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Professor David Bradley


Emeritus Professor
+44 (0)1483 683771
07 BC 04

Academic and research departments

Department of Physics.

Biography

Biography

David Bradley (PhD (USM), MSc (London), BSc (Exeter)) is Professor of Radiation and Medical Physics at the University of Surrey. He has taught and researched in Universities for some 35 years. For some 14 years he Directed MSc programmes in Medical Physics. He was also for six years the Secretary of the International Radiation Physics Society (IRPS). Presently he is Editor-in-Chief of the British Journal of Radiology and Consulting Editor to the Elsevier journals 'Applied Radiation and Isotopes' and 'Radiation Physics and Chemistry'. Dr Bradley is the author of over 250 publications and has made more than 150 presentations at conferences. His interests are in researching the fundamental interactions of radiation in matter as well as their applications in biomedical areas and in industry.

Research interests

Dr Bradley has active research interests in the fundamentals and applications of photon scattering, radioanalytical techniques for determination of trace element concentrations, radiological risks associated with Naturally Occurring Radioactive Material (NORM), the development of synchrotron techniques for characterisation of media, predominantly biological tissues, radiation effects on tissues, and development of silica based luminesence dosimeters.

Research projects of current interest include: the localisation of Zn and Sr in synovial joints, the development of doped radiosensitive glass, the effects of ionizing radiation on extracellular matrix, and near-edge elastic photon scattering from dilute aqueous ions.

Teaching

Module Leader for PHYM018 Radiation Protection

Departmental duties

Course Deputy Director for the MSc Programme in Medical Physics and the MSc Programme in Medical Physics

My publications

Publications

Khandaker MU, Wahib NB, Amin YM, Bradley DA (2013) Committed effective dose from naturally occuring radionuclides in shellfish, Radiation Physics and Chemistry
Recognizing their importance in the average Malaysian daily diet, the radioactivity concentrations in mollusc- and crustacean-based food have been determined for key naturally occuring radionuclides. Fresh samples collected from various maritime locations around peninsular Malaysia have been processed using standard procedures; the radionuclide concentrations being determined using an HPGe ³-ray spectrometer. For molluscs, assuming secular equilibrium, the range of activities of U (Ra), Th (Ra) and K were found to be 3.28±0.35 to 5.34±0.52, 1.20±0.21 to 2.44±0.21 and 118±6 to 281±14 Bq kg dry weight, respectively. The respective values for crustaceans were 3.02±0.57 to 4.70±0.52, 1.38±0.21 to 2.40±0.35 and 216±11 to 316±15 Bq kg. The estimated average daily intake of radioactivity from consumption of molluscs are 0.37 Bq kg for U (Ra), 0.16 Bq kg for Th (Ra) and 18 Bq kg for K; the respective daily intake values from crustaceans are 0.36 Bq kg, 0.16 Bq kg and 23 Bq kg. Associated annual committed effective doses from molluscs are estimated to be in the range 21.3 to 34.7 ¼Sv for Ra, 19.3 to 39.1 ¼Sv for Ra and 17.0 to 40.4 ¼Sv for K. For crustaceans, the respective dose ranges are 19.6 to 30.5 ¼Sv, 22.0 to 38.4 ¼Sv and 31.1 to 45.5 ¼Sv, being some several times world average values. © 2013 Elsevier Ltd.
Santawamaitre T, Malain D, Al-Sulaiti HA, Bradley DA, Matthews MC, Regan PH (2014) Determination of (238)U, (232)Th and (40)K activity concentrations in riverbank soil along the Chao Phraya river basin in Thailand., J Environ Radioact 138 pp. 80-86
The activity concentrations of (238)U, (232)Th and (40)K in riverbank soil along the Chao Phraya river basin was determined through gamma-ray spectrometry measurements made using a hyper-pure germanium detector in a low background configuration. The ranges of activity concentrations of (238)U, (232)Th and (40)K were found to be 13.9 ” 76.8, 12.9 ” 142.9 and 178.4 ” 810.7 Bq kg(-1), respectively. The anthropogenic radionuclide, (137)Cs, was not observed in statistically significant amounts above the background level in the current study. The absorbed gamma dose rate in air at 1 m above the ground surface, the outdoor annual effective dose equivalent, the values of the radium equivalent activity and the external hazard index associated with all the soil samples in the present work were evaluated. The results indicate that the radiation hazard from primordial radionuclides in all soil samples from the area studied in this current work is not significant.
Abdul Rahman AT, Nisbet A, Bradley DA (2010) Dose-rate and the reciprocity law: TL response of Ge-doped SiO2 optical fibers at therapeutic radiation doses, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Alawiah A, Bauk S, Marashdeh MW, Nazura MZN, Abdul-Rashid HA, Yusoff Z, Gieszczyk W, Noramaliza MN, Adikan FRM, Mandiraji GA, Tamchek N, Muhd-Yassin SZ, Mat-Sharif KA, Zulkifli MI, Omar N, Abdullah WSW, Bradley DA (2015) The thermoluminescence glow curve and the deconvoluted glow peak characteristics of erbium doped silica fiber exposed to 70-130 kVp x-rays, APPLIED RADIATION AND ISOTOPES 104 pp. 197-202 PERGAMON-ELSEVIER SCIENCE LTD
Palmer AL, Bradley DA, Nisbet A (2015) Evaluation and mitigation of potential errors in radiochromic film dosimetry due to film curvature at scanning, JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 16 (2) pp. 425-431 MULTIMED INC
Mizanur Rahman AKM, Mizanur Rahman AKM, Zubair HT, Begum M, Begum M, Abdul-Rashid HA, Yusoff Z, Ung NM, Mat-Sharif KA, Wan Abdullah WS, Amouzad Mahdiraji G, Amin YM, Maah MJ, Bradley DA (2014) Germanium-doped optical fiber for real-time radiation dosimetry, Radiation Physics and Chemistry
© 2015 Elsevier Ltd. Over the past three decades growing demand for individualized in vivo dosimetry and subsequent dose verification has led to the pursuit of newer, novel and economically feasible materials for dosimeters. These materials are to facilitate features such as real-time sensing and fast readouts. In this paper, purposely composed SiO2:Ge optical fiber is presented as a suitable candidate for dosimetry. The optical fiber is meant to take advantage of the RL/OSL technique, providing both online remote monitoring of dose rate, and fast readouts for absorbed dose. A laboratory-assembled OSL reader has been used to acquire the RL/OSL response to LINAC irradiations (6MV photons). The notable RL characteristics observed include constant level of luminescence for the same dose rate (providing better consistency compared to TLD-500), and linearity of response in the radiotherapy range (1Gy/min to 6Gy/min). The OSL curve was found to conform to an exponential decay characteristic (illumination with low LED source). The Ge doping resulted in an effective atomic number, Z eff, of 13.5 (within the bone equivalent range). The SiO2:Ge optical fiber sensor, with efficient coupling, can be a viable solution for in vivo dosimetry, besides a broad range of applications.
Hashim S, Mhareb MHA, Mhareb MHA, Ghoshal SK, Alajerami YSM, Bradley DA, Bradley DA, Saripan MI, Tamchek N, Alzimami K (2014) Luminescence characteristics of Li2O-MgO-B2O3 doped with Dy3+ as a solid TL detector, Radiation Physics and Chemistry
© 2015 Elsevier Ltd. Enhancing the luminescence characteristics of rare earth doped borate glasses is the key issue in achieving an accurate dosimeter. Series of lithium and magnesium oxide modified borate glasses of compositions 20Li2O-(70-x)B2O3-10MgO-xDy2O3, where 0.3dxd1mol% are prepared using melt-quenching method. Synthesized samples are further activated with different concentration of Dy3+ and subjected to different doses by using a 60Co source. Effects of Dy3+ concentrations on luminescence behavior are examined. XRD patterns confirm the amorphous nature of all samples. A simple glow curve exhibits a peak at 190°C and optimum intensity for 0.5mol% of Dy3+ ions. Thermoluminescence (TL) properties including dose response and effective atomic number are determined. A good linearity in the dose response with correlation coefficient ~0.9977 and a tissue equivalent Z eff ~8.71 is achieved. The room temperature photoluminescence (PL) spectra of these glasses under 350nm laser excitations reveal two enhanced peaks centered at 480nm (blue) and 573nm (yellow). The mechanism for the TL and PL enhancements are discussed and understood. These attractive luminescence features of prepared glasses may contribute towards the advancement of dosimetry.
Daar E, Al Mugren KS, Chika S, Barnes S, Bradley DA (2015) XRF measurements of Zn, Sr and Pb in archaeological bone, X-Ray Spectrometry 44 (3) pp. 129-134
© 2015 John Wiley & Sons, Ltd.We study elemental concentrations in archaeological human bone, linked to interest in essential element homeostasis and also uptake of potentially harmful elements; the study of elemental concentrations in ancient skeletal remains can potentially be linked with modern studies, providing a reference to high exposure levels no longer common today. The samples, adult bone from the Romano-British period, were obtained from Cirencester, located approximately 150km to the west of London. Some of the remains were found in stone enclosures, others in Pb-lined enclosures, and yet, others devoid of a record of the form of burial. Using a measurement arrangement consisting of a low-energy mini-X-ray generator and a Si-PIN detector, results are obtained of periosteal (bone surface) concentrations, the influence of the post-mortem environment being clearly differentiated from in vivo uptake. Simultaneous multi-element measurements have been made of Zn, Sr and Pb, with respective concentrations in the range 27±16 to 254±17¼gg-1; 33±16 to 124±17¼gg-1 and 44±15 to ~10% Pbg-1 of interrogated medium. Lead-lined burials result in Pb contamination of the inner (cambium/osteogenic) surface layer of the bone, positively skewing Pb data.
Abdul Rahman A, Hugtenburg R, Abdul Sani S, Alalawi A, Issa F, Thomas R, Barry M, Nisbet A, Bradley DA (2012) An investigation of the thermoluminescence of Ge-doped SiO(2) optical fibres for application in interface radiation dosimetry., Applied Radiation and Isotopes 70 (7) pp. 1436-1441
We investigate the ability of high spatial resolution (
Dermosesian E, Amouzad Mahdiraji G, Mahamd Adikan FR, Bradley DA, Bradley DA (2014) Improving thermoluminescence response through the fabrication of novel microstructured fibers, Radiation Physics and Chemistry
© 2015. We present a novel technique aimed at improving upon the thermoluminescence (TL) response of optical fibers. The technique, based on the stack-and-draw method, is more conventionally used for microstructured optical fiber (MOF) fabrication. Utilizing the approach, the TL response of a single microstructured fiber can be shown to substantially improve upon that of a single capillary fiber, approaching a 30 fold increase in sensitivity. Present results provide strong support for the idea that by collapsing and fusing the surface walls of stacked fibers, strain-related defects are created, increasing the TL yield many times over. The substantial increase in sensitivity of these glass-based systems point to more extensive applications, the production of such detectors allowing versatile use, down to much lower doses than currently available using single capillary fibers.
Hugtenburg RP, England DW, Bradley DA (2007) Near-edge elastic photon scattering in amorphous systems, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 263 (1) pp. 22-26 ELSEVIER SCIENCE BV
Al-Sulaiti H, Alkhomashi N, Al-Dahan N, Al-Dosari M, Bradley DA, Bukhari S, Matthews M, Regan PH, Santawamaitre T (2011) Determination of the natural radioactivity in Qatarian building materials using high-resolution gamma-ray spectrometry, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 915-919
This study is aimed at the determination of the activity concentrations of naturally occurring and technically enhanced levels of radiation in building materials used across the State of Qatar. Samples from a range of common building materials, including Qatarian cement, Saudi cement, white cement, sand and washed sand, have been analyzed, in addition to other samples of cements raw materials and additives collected from the main suppliers in Qatar. In order to establish the activity concentrations associated with the 235,8U and 232Th natural decay chains and 40K, the samples have been studied using a high-resolution, low-background gamma-ray spectrometry set-up. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the preliminary results of the activity concentrations associated with the naturally occurring radionuclide chains for the building materials collected across the Qatarian peninsula. © 2011 Elsevier B.V.
Ramli AT, Bradley DA, Hashim S, Wagiran H (2009) The thermoluminescence response of doped SiO2 optical fibres subjected to alpha-particle irradiation, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 428-432 PERGAMON-ELSEVIER SCIENCE LTD
Al-Sulaiti H, Nasir T, Al Mugren KS, Alkhomashi N, Al-Dahan N, Al-Dosari M, Bradley DA, Bukhari S, Matthews M, Regan PH, Santawamaitre T, Malain D, Habib A (2012) Determination of the natural radioactivity levels in north west of Dukhan, Qatar using high-resolution gamma-ray spectrometry., Appl Radiat Isot 70 (7) pp. 1344-1350
This study is aimed at the determination of the activity concentrations of naturally occuring and technologically enhanced levels of radiation in 34 representative soil samples that have been collected from an inshore oil field area which was found to have, in a previous study, the highest observed value of 226Ra concentration among 129 soil samples. The activity concentrations of 238U and 226Ra have been inferred from gamma-ray transitions associated with their decay progenies and measured using a hyper-pure germanium detector. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the values of the activity concentrations associated with the naturally occuring radionuclide chains for all the samples collected from NW Dukhan. Discrete-line, gamma-ray energy transitions from spectral lines ranging in energy from
Bradley DA, Wells K (2013) Reprint of: Biomedical applications reviewed: Hot topic areas, Radiation Physics and Chemistry
Making reference to the British Journal of Radiology and competitor journal titles, we look at the general area of biomedical physics, reviewing some of the associated topics in ionising radiation research attracting interest over the past 2 years. We also reflect on early developments that have paved the way for these endeavours. The talk is illustrated by referring to a number of biomedical physics areas in which this group has been directly involved, including novel imaging techniques that address compositional and structural makeup as well as use of elastically scattered X-ray phase contrast, radiation damage linking to possible pericardial effects in radiotherapy, simulation of microvascularity and oxygenation with a focus of radiation resistant hypoxic tumours, issues of high spatial resolution dosimetry and tissue interface radiotherapy with doses enhanced through use of high atomic number photoelectron conversion media. © 2013 Elsevier Ltd. All rights reserved.
Al-Sulaiti H, Alkhomashi N, Al-Dahan N, Al-Dosari M, Bradley DA, Bukhari S, Matthews M, Regan PH, Santawamaitre T (2011) Determination of the natural radioactivity in Qatarian building materials using high-resolution gamma-ray spectrometry, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 915-919 Elsevier
Alajerami YSM, Hashim S, Ghoshal SK, Bradley DA, Mhareb M, Saleh MA (2014) Copper doped borate dosimeters revisited, Journal of Luminescence 155 pp. 141-148
We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu+ and Cu++) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu+ ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. © 2014 Elsevier B.V.
Farquharson MJ, Al-Ebraheem A, Theodorakou C, Ryan E, Bradley DA, Gurusamy K, Davidson B (2009) Measurement of K, Fe, Cu and Zn levels in secondary colorectal liver cancer and surrounding normal liver tissue, and their potential as a tissue classifier, X-RAY SPECTROMETRY 38 (2) pp. 81-88 JOHN WILEY & SONS LTD
Bradley DA, Hugtenburg RP, Nisbet A, Abdul Rahman AT, Issa F, Mohd Noor N, Alalawi A (2012) Review of doped silica glass optical fibre: Their TL properties and potential applications in radiation therapy dosimetry., Appl Radiat Isot
Review is made of dosimetric studies of Ge-doped SiO(2) telecommunication fibre as a 1-D thermoluminescence (TL) system for therapeutic applications. To-date, the response of these fibres has been investigated for UV sources, superficial X-ray beam therapy facilities, a synchrotron microbeam facility, electron linear accelerators, protons, neutrons and alpha particles, covering the energy range from a few eV to several MeV. Dosimetric characteristics include, reproducibility, fading, dose response, reciprocity between TL yield and dose-rate and energy dependence. The fibres produce a flat response to fixed photon and electron doses to within better than 3% of the mean TL distribution. Irradiated Ge-doped SiO(2) optical fibres show limited signal fading, with an average loss of TL signal of
Abdelkader MH, Alkhateeb SM, Bradley DA, Pani S, Abdelkader MH, Alkhateeb SM, Bradley DA (2012) Development and characterization of a laboratory based X-ray diffraction imaging system for material and tissue characterization, Applied Radiation and Isotopes
Soft tissues feature a degree of short-range order, giving rise to diffraction patterns with broader peaks than crystalline materials. For this reason, an X-ray diffraction system (XRD) for characterization of soft tissue has less stringent requirements in terms of momentum transfer resolution than the one aimed at characterizing crystalline materials. We present results on the characterization of two energy-dispersive XRD systems. The first was based on conical collimation at 5.9° and the second was based on linear collimation at varying angles between 2° and 10°. The systems include a CdTe detector and a W-anode X-ray source. The angular resolution was measured as a function of sample thickness and scattering angle. Preliminary results confirm the effectiveness of the method for the characterization of biological tissues, showing insensitivity to small changes in angular acceptance and sample thickness, also showing it is possible to combine scattering data obtained at different angles. © 2012 Elsevier Ltd. All rights reserved.
Mohd Noor N, Nisbet A, Hussein M, Sarene Chu S, Kadni T, Abdullah N, Bradley DA (2017) Dosimetry Audits and Intercomparisons in Radiotherapy: a Malaysian Profile, Radiation Physics and Chemistry 140 pp. 207-212 Elsevier
Quality audits and intercomparisons are important in ensuring control of processes in any system of endeavour. Present interest is in control of dosimetry in teletherapy, there being a need to assess the extent to which there is consistent radiation dose delivery to the patient. In this study we review significant factors that impact upon radiotherapy dosimetry, focusing upon the example situation of radiotherapy delivery in Malaysia, examining existing literature in support of such efforts. A number of recommendations are made to provide for increased quality assurance and control. In addition to this study, the first level of intercomparison audit i.e. measuring beam output under reference conditions at eight selected Malaysian radiotherapy centres is checked; use being made of 9 µm core diameter Ge-doped silica fibres (Ge-9 µm). The results of Malaysian Secondary Standard Dosimetry Laboratory (SSDL) participation in the IAEA/WHO TLD postal dose audit services during the period between 2011 and 2015 will also been discussed. In conclusion, following review of the development of dosimetry audits and the conduct of one such exercise in Malaysia, it is apparent that regular periodic radiotherapy audits and intercomparison programmes should be strongly supported and implemented worldwide. The programmes to-date demonstrate these to be a good indicator of errors and of consistency between centres. A total of ei+ght beams have been checked in eight Malaysian radiotherapy centres. One out of the eight beams checked produced an unacceptable deviation; this was found to be due to unfamiliarity with the irradiation procedures. Prior to a repeat measurement, the mean ratio of measured to quoted dose was found to be 0.99 with standard deviation of 3%. Subsequent to the repeat measurement, the mean distribution was 1.00, and the standard deviation was 1.3%.
Issa F, Latip NAA, Bradley DA, Nisbet A (2011) Ge-doped optical fibres as thermoluminescence dosimeters for kilovoltage X-ray therapy irradiations, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 834-837
We investigate key dosimetric parameters for the thermoluminescence (TL) of Ge-doped silica optical fibres irradiated by X-rays generated at 90 and 300 kVp. The parameters include dose response, reproducibility and fading. Relative dose measurements were performed, obtaining central axis percentage depth dose (PDD) values, use being made of doped fibres irradiated in water and solid water phantoms. TL yields were compared with published data and ionisation chamber measurements. Linearity to dose was demonstrated over the investigated range (0.16 Gy), with reproducibility to within±2%. TL fading was found to be minimal, at
Asaduzzaman KH, Khandaker MU, Amin YM, Bradley DA, Mahat RH, Nor RM (2014) Soil-to-root vegetable transfer factors for (226)Ra, (232)Th, (40)K, and (88)Y in Malaysia., J Environ Radioact 135 pp. 120-127
Soil-to-plant transfer factors (TFs) are of fundamental importance in assessing the environmental impact due to the presence of radioactivity in soil and agricultural crops. Tapioca and sweet potato, both root crops, are popular foodstuffs for a significant fraction of the Malaysian population, and result in intake of radionuclides. For the natural field conditions experienced in production of these foodstuffs, TFs and the annual effective dose were evaluated for the natural radionuclides (226)Ra, (232)Th, (40)K, and for the anthropogenic radionuclide (88)Y, the latter being a component of fallout. An experimental tapioca field was developed for study of the time dependence of plant uptake. For soil samples from all study locations other than the experimental field, it has been shown that these contain the artificial radionuclide (88)Y, although the uptake of (88)Y has only been observed in the roots of the plant Manihot esculenta (from which tapioca is derived) grown in mining soil. The estimated TFs for (226)Ra and (232)Th for tapioca and sweet potato are very much higher than that reported by the IAEA. For all study areas, the annual effective dose from ingestion of tapioca and sweet potato are estimated to be lower than the world average (290 ¼Sv y(-1)).
Saeed Al-Ahbabi S, Bradley DA, Beyomi M, Alkatib Z, Adhaheri S, Darmaki M, Nisbet A (2012) A comparison of protocols for external beam radiotherapy beam calibrations., Appl Radiat Isot 70 (7) pp. 1331-1336
A number of codes of practice (CoP) for electron and photon radiotherapy beam dosimetry are currently in use. Comparison is made of the more widely used of these, specifically those of the International Atomic Energy Agency (IAEA TRS-398), the American Association of Physicists in Medicine (AAPM TG-51) and the Institute of Physics and Engineering in Medicine (IPEM 2003). All are based on calibration of ionization chambers in terms of absorbed dose to water, each seeking to reduce uncertainty in delivered dose, providing an even stronger system of primary standards than previous air-kerma based approaches. They also provide a firm, traceable and straight-forward formalism (Radiology, 1996). Included in making dose assessments for the three CoP are calibration coefficients for a range of beam quality indices. Measurements have been performed using clinical photon and electron beams, the absorbed dose to water being obtained following the recommendations given by each code. Electron beam comparisons have been carried out using measurements for electron beams of nominal energies 6, 9, 12, 16 and 20 MeV. Comparisons were also carried out for photon beams of nominal energies 6 and 18 MV. For photon beams use was made of NE2571 cylindrical graphite walled ionization chambers, cross-calibrated against an NE2611 Secondary Standard; for electron beams, PTW Markus and NACP-02 plane-parallel chambers were used. Irradiations were made using Varian 600C/2100C linacs, supported by water tanks and Virtual Water" phantoms. The absorbed doses for photon and electron beams obtained following these CoP are all in good agreement, with deviations of less than 2%. A number of studies have been carried out by different groups in different countries to examine the consistency of dosimetry codes of practice or protocols. The aim of these studies is to confirm that the goal of those codes is met, namely uniformity in establishment of dosimetry of all radiation beam types used in cancer therapy in the world, and this is one of the studies.
Akar Tarim U, Gurler O, Ozmutlu EN, Yalcin S, Gundogdu O, Sharaf JM, Bradley DA (2012) The energy spectrum of 662 keV photons in a water equivalent phantom, Radiation Physics and Chemistry 81 (7) pp. 745-748 Elsevier
Investigation is made on the energy spectrum of photons originating from interactions of 662 keV primary gamma-ray photons emitted by a point source positioned at the centre of a water equivalent solid phantom of dimensions 19 cm×19 cm×24 cm. Peaks resulting from total energy loss (photopeak) and multiple and back scattering have been observed using a 51 mm×51 mm NaI(Tl) detector; good agreement being found between the measured and simulated response functions. The energy spectrum of the gamma photons obtained through the Monte Carlo simulation reveals local maxima at about 100 keV and 210 keV, being also observed in the experimental response function. Such spectra can be used as a method of testing the water equivalence of solid phantom media before their use for dosimetry measurements.
Ibrahim SA, Omar SSC, Hashim S, Mahdiraji GA, Bradley DA, Kadir AB, Isa NM (2014) Assessment of Ge-doped optical fibres subjected to x-ray irradiation, Journal of Physics: Conference Series 546 (1)
© Published under licence by IOP Publishing Ltd.We have reported the thermoluminescence (TL) response of five different diameters
Hashim S, Al-Ahbabi S, Bradley DA, Webb M, Jeynes C, Ramli AT, Wagiran H (2009) The thermoluminescence response of doped SiO2 optical fibres subjected to photon and electron irradiations, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 423-427 PERGAMON-ELSEVIER SCIENCE LTD
Daar E, Woods E, Keddie JL, Nisbet A, Bradley DA (2010) Effect of penetrating ionising radiation on the mechanical properties of pericardium, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 356-360 ELSEVIER SCIENCE BV
Issa F, Abdul Rahman AT, Hugtenburg RP, Bradley DA, Nisbet A (2012) Establishment of Ge-doped optical fibres as thermoluminescence dosimeters for brachytherapy., Appl Radiat Isot 70 (7) pp. 1158-1161 Elsevier
This study aims to establish the sensitive,
Abdul Rahman AT, Abu Bakar NK, Bradley DA, Chandra Paul M (2014) Ultraviolet radiation (UVR) dosimetry system and the use of Ge-doped silica optical fibres, Radiation Physics and Chemistry
Previous studies have shown that over exposure to ultraviolet radiation (UVR), either from sunlight or artificial sources, can cause severe biological effects including cataracts, photokeratitis and skin cancer. In this respect, there exists the need to introduce a sensitive UV dosimetric material capable of measuring radiation dose to high accuracy in order to deliver UVR safely and efficiently. Present study has focussed on the investigation of the potential thermoluminescent (TL) sensitivity of commercially available germanium (Ge)-doped silica (SiO) optical fibres subjected to UVR. The main interest of this study is to find out whether these doped SiO optical fibres can be used as a sensible integrator of environmental UV exposures. In the present study, commercially available Ge-doped SiO optical fibres have been used with a core diameter of 11 ¼m (CorActive, Canada), 23 ¼m (Central Glass and Ceramic Research Institute Kolkata, India) and 50 ¼m (Central Glass and Ceramic Research Institute Kolkata, India) and a cladding diameter of 125±0.1 ¼m, irradiated over a wide range of UV dose. Results have shown that these fibres exhibit a linear dose response (with correlation coefficient better than 0.9852). The 50 ¼m fibre produces greater TL response than that obtained for 11- and 23 ¼m fibres. The TL results are compared with that of the well-established TL dosimeter material lithium fluoride. © 2014 Elsevier Ltd. All rights reserved.
Alalawi AI, Jafari SM, Najem MA, Nisbet A, Hussein M, Alzimami KS, Bradley DA, Spyrou NM, Alsaleh W, Hugtenburg RP, Clark CH, Abolaban F (2014) Preliminary investigations of two types of silica-based dosimeter for small-field radiotherapy, Radiation Physics and Chemistry
Two thermoluminescent dosimeters (SiO-GeO doped fibres and glass beads (GB)) were used to measure small photon field doses and compared against GAFCHROMIC film, a small ionisation chamber (RK-018) and a p-type silicon diode (SCANDITRONIX, F1356), as well as Monte Carlo simulations with FLUKA and BEAMnrc/DOSXYZnrc. Ge-doped SiO fibres have been shown by this group to offer a viable system for use as dosimeters. The fibres and GB offer good spatial resolution (~120 ¼m and 2 mm respectively), large dynamic dose range (with linearity from tens of mGy up to well in excess of many tens of Gy), are non-hygroscopic and are of low cost. Measurements of beam profiles for field sizes of 10 mm×10 mm, 20 mm×20 mm, 30 mm×30 mm, 40 mm×40 mm, and 100 mm×100 mm were carried out. Through the use of a customised solid water phantom, doped optical fibres and GBs were placed at defined positions along the x-and y-axes to allow accurate beam profile measurement. The maximum difference between FWHM measurements was 1.8 mm. For penumbra measurements (measured between 80% and 20% isodoses), the maximum difference was
Bradley DA, Aziz AZ, Knapton AJ, Abdul-Rashid HA, Rahman AKMM, Amin YM, Nor RM, Maah MJ, Mahat R (2013) Optically stimulated luminescence in beta irradiated Ge-doped optical fibre, 4th International Conference on Photonics, ICP 2013 - Conference Proceeding pp. 38-40
Ge-doped optical fiber has been reported to luminate following exposures to radiation sources. We report in this paper Optically Stimulated Luminescence (OSL) of Ge-doped SiO2 fibres following prolonged exposure to beta particles, giving a dose of ~20 Gy. A shift in the wavelength of transmitted light has been observed, due to OSL from 827 ± 34 nm to 917 ± 15 nm. © 2013 IEEE.
Yaakob NH, Wagiran H, Hossain I, Ramli AT, Bradley DA, Hashim S, Ali H (2011) Electron irradiation response on Ge and Al-doped SiO2 optical fibres, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Kaabar W, Daar E, Gundogdu O, Jenneson PM, Farquharson MJ, Webb M, Jeynes C, Bradley DA (2009) Metal deposition at the bone-cartilage interface in articular cartilage, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 475-479 PERGAMON-ELSEVIER SCIENCE LTD
Alalawi AI, Jafari SM, Najem MA, Alsaleh W, Clark CH, Nisbet A, Abolaban F, Hugtenburg RP, Hussein M, Alzimami KS, Bradley DA, Spyrou NM (2014) Preliminary investigations of two types of silica-based dosimeter for small-field radiotherapy, Radiation Physics and Chemistry 104 pp. 139-144
Two thermoluminescent dosimeters (SiO2-GeO2 doped fibres and glass beads (GB)) were used to measure small photon field doses and compared against GAFCHROMIC film, a small ionisation chamber (RK-018) and a p-type silicon diode (SCANDITRONIX, F1356), as well as Monte Carlo simulations with FLUKA and BEAMnrc/DOSXYZnrc. Ge-doped SiO2 fibres have been shown by this group to offer a viable system for use as dosimeters. The fibres and GB offer good spatial resolution (~120¼m and 2mm respectively), large dynamic dose range (with linearity from tens of mGy up to well in excess of many tens of Gy), are non-hygroscopic and are of low cost. Measurements of beam profiles for field sizes of 10mm×10mm, 20mm×20mm, 30mm×30mm, 40mm×40mm, and 100mm×100mm were carried out. Through the use of a customised solid water phantom, doped optical fibres and GBs were placed at defined positions along the x-and y-axes to allow accurate beam profile measurement. The maximum difference between FWHM measurements was 1.8mm. For penumbra measurements (measured between 80% and 20% isodoses), the maximum difference was
Bradley DA, Mahdiraji GA, Ghomeishi M, Dermosesian E, Adikan FRM, Rashid HAA, Maah MJ (2015) Enhancing the radiation dose detection sensitivity of optical fibres, Applied Radiation and Isotopes 100 pp. 43-49
© 2014 Elsevier Ltd.A method for improving the thermoluminescence (TL) yield of silica-based optical fibres is demonstrated. Using silica obtained from a single manufacturer, three forms of pure (undoped) fibre (capillary-, flat-, and photonic crystal fibre (PCF)) and two forms of Ge-doped fibre (capillary- and flat-fibre) were fabricated. The pure fibre samples were exposed to 6 and 21. MeV electrons, the doped fibres to 6. MV photons. The consistent observation of large TL yield enhancement is strongly suggestive of surface-strain defects generation. For 6. MeV irradiations of flat-fibre and PCF, respective TL yields per unit mass of about 12.0 and 17.5 times that of the undoped capillary-fibre have been observed. Similarly, by making a Ge-doped capillary-fibre into flat-fibre, the TL response is found to increase by some 6.0 times. Thus, in addition to TL from the presence of a dopant, the increase in fused surface areas of flat-fibres and PCF is seen to be a further important source of TL. The glow-curves of the undoped fibres have been analysed by computational deconvolution. Trap centre energies have been estimated and compared for the various fibre samples. Two trap centre types observed in capillary-fibre are also observed in flat-fibre and PCF. An additional trap centre in flat-fibre and one further trap centre in PCF are observed when compared to capillary fibre. These elevated-energy trap centres are linked with strain-generated defects in the collapsed regions of the flat fibre and PCF.
Daar E, Kaabar W, Keddie JL, Nisbet A, Bradley DA, Lei C, Nisbet A (2010) AFM and uni-axial testing of pericardium exposed to radiotherapy doses, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
The pericardium, a double-layered sac that encloses the heart, is made up of collagen and elastin fibres embedded in an amorphous matrix (forming the extracellular matrix). Collagen fibres are aligned in multidirectional orientation layers. This free arrangement of fibres gives the pericardium its viscoelastic properties and the ability to deform in all directions. This is an important mechanical property for the heart to perform its physiological functions, acknowledging the fact that the heart is attached to different ligaments and muscles in all directions. The present study aims to investigate the effect of penetrating photon ionising radiation on bovine pericardium tissue. This links to an interest in seeking to understand possible mechanisms underlying cardiac complications following treatment of the left breast in radiotherapy regimes. Pericardium samples were subjected to doses in the range 0-80 Gy. Atomic force microscopy (AFM) has been applied in characterising changes in the infrastructural and mechanical properties of the tissues. Preliminary data for doses of 80 Gy shows there was no significant change in the D-spacing period of the banded structure collagen type I but a significant increase is observed in the FWHM of the fibril widths (by between 25% and 27%) over that of unirradiated pericardium tissue. © 2010 Elsevier B.V. All rights reserved.
Alalawi AI, Nisbet A, Alzimami KS, Bradley DA, Hugtenburg RP, Abdul Rahman AT, Barry MA (2013) Measurement of dose enhancement close to high atomic number media using optical fibre thermoluminescence dosimeters, Radiation Physics and Chemistry
Present interest concerns development of a system to measure photoelectron-enhanced dose close to a tissue interface using analogue gold-coated doped silica-fibre thermoluminescence detectors and an X-ray set operating at 250 kVp. Study is made of the dose enhancement factor for various thicknesses of gold; measurements at a total gold thickness of 160 nm (accounting for incident and exiting photons) produces a mean measured dose enhancement factor of 1.33±0.01 To verify results, simulations of the experimental setup have been performed. © 2013 Elsevier Ltd. All rights reserved.
Bradley DA, Wells K (2013) Biomedical applications reviewed: Hot topic areas, Radiation Physics and Chemistry 85 pp. 42-52
Making reference to the British Journal of Radiology and competitor journal titles, we look at the general area of biomedical physics, reviewing some of the associated topics in ionising radiation research attracting interest over the past 2 years. We also reflect on early developments that have paved the way for these endeavours. The talk is illustrated by referring to a number of biomedical physics areas in which this group has been directly involved, including novel imaging techniques that address compositional and structural makeup as well as use of elastically scattered X-ray phase contrast, radiation damage linking to possible pericardial effects in radiotherapy, simulation of microvascularity and oxygenation with a focus of radiation resistant hypoxic tumours, issues of high spatial resolution dosimetry and tissue interface radiotherapy with doses enhanced through use of high atomic number photoelectron conversion media. © 2012 Elsevier Ltd.
Alawiah A, Bauk S, Abdul-Rashid HA, Gieszczyk W, Hashim S, Mahdiraji GA, Tamchek N, Bradley DA (2015) Potential application of pure silica optical flat fibers for radiation therapy dosimetry, Radiation Physics and Chemistry 106 pp. 73-76
Pure silica optical flat fibers (FF) have been proposed as the basis for a novel radiation sensor by the measurement of the thermoluminescence (TL) produced. In this paper the TL performance of the FFs were studied. Using a linear accelerator (LINAC) delivering doses in the range 0.2-10.0Gy, the TL dosimetric glow curves of the FFs were studied with respect to 6MeV electron and 6MV photon beams. When exposed to 6MeV electron irradiation, the pure silica FFs displayed a supralinear response starting from 2Gy up to 10.0Gy. While for 6MV photon irradiation, the FFs shows linear characteristic (f(D) = 1) nearly up to 2Gy. The TL intensity (Im) of the main peak of FFs is 1.5 times higher for 6MeV electron beams than for 6MV photon beams. The maximum peak temperature (Tm) it is not affected by the type of irradiation used at the same dose while the maximum TL intensity (Im) was found to be dependent on the type of radiation used. Overall results indicate that the pure silica FFs can be used as radiation sensors in the high-dose therapy dosimetry. © 2014 Elsevier Ltd.
Zahaimi NA, Ooi Abdullah MHR, Abdul Rahman AT, Zin H, Abdul Rahman AL, Hashim S, Saripan MI, Paul MC, Bradley DA (2014) Dopant concentration and thermoluminescence (TL) properties of tailor-made Ge-doped SiO fibres, Radiation Physics and Chemistry
Study focuses on characterisation of diverse concentrations of Ge-doped SiO fibre as a potential thermoluminescence (TL) system for radiotherapy dosimetry. Irradiations were made using a linear accelerator providing 6 MV and 10 MV photon beams. Investigation has been done on various doped core diameter Ge-doped SiO glass fibres such as commercial telecommunication fibres of 8 ¼m and 9 ¼m (CorActive High Tech, Canada), tailor-made fibres of 23 and 50 ¼m produced by the Central Glass and Ceramic Research Institute Kolkata, and tailor-made fibres of 11 ¼m produced by the University of Malaya Photonics Research Centre. The fibres have been characterised for TL sensitivity, reproducibility, dose- and energy-dependence. The area under the TL glow curve increases with increasing core diameter. For repeat irradiations at a fixed dose the dosimeter produces a flat response better than 4% (1SD) of the mean of the TL distribution. Minimal TL signal fading was found, less than 0.5% per day post irradiation. Linearity of TL has been observed with a correlation coefficient (r) of better than 0.980 (at 95% confidence level). For particular dopant concentrations, the least square fits show the change in TL yield, in counts per second per unit mass, obtained from 50 ¼m core diameter fibres irradiated at 6 MV of photon to be 8 times greater than that of 8 ¼m core diameter fibre. With respect to energy response, the TL yield at 10 MV decreases by~5% compared to that at 6 MV, primarily due to the lower mass energy absorption coefficient at higher photon energy. These early results indicate that selectively screened fibres can be developed into a promising TL system, offering high spatial resolution capability and, with this, verification of complex radiotherapy dose distributions. © 2014 Elsevier Ltd. All rights reserved.
Alzimami KS, Maghraby AM, Bradley DA (2013) Comparative study of some new EPR dosimeters, Radiation Physics and Chemistry
Investigations have been made of four new radiation dosimetry EPR candidates from the same family of materials: sulfamic acid, sulfanillic acid, homotaurine, and taurine. Mass energy attenuation coefficients, mass stopping power values and the time dependence of the radiation induced radicals are compared. Also investigated are the microwave saturation behavior and the effect of applied modulation amplitude on both peak-to-peak line width (W ) and peak-to-peak signal height (H ). The dosimeters are characterized by simple spectra and stable radiation-induced radicals over reasonable durations, especially in taurine dosimeters. Sulfamic acid dosimeters possessed the highest sensitivity followed by taurine and homotaurine and sulfanillic. © 2013 Elsevier Ltd. All rights reserved.
Habib AS, Bradley DA, Regan PH, Shutt AL (2010) The use of MCNP and gamma spectrometry in supporting the evaluation of NORM in Libyan oil pipeline scale, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 245-251 ELSEVIER SCIENCE BV
Farquharson MJ, Al-Ebraheem A, Falkenberg G, Leek R, Harris AL, Bradley DA (2008) The distribution of trace elements Ca, Fe, Cu and Zn and the determination of copper oxidation state in breast tumour tissue using mu SRXRF and mu XANES, PHYSICS IN MEDICINE AND BIOLOGY 53 (11) pp. 3023-3037 IOP PUBLISHING LTD
Skeldon AC, Chaffey G, Lloyd DJ, Mohan V, Bradley DA, Nisbet A (2012) Modelling and detecting tumour oxygenation levels., PLoS One 7 (6)
Tumours that are low in oxygen (hypoxic) tend to be more aggressive and respond less well to treatment. Knowing the spatial distribution of oxygen within a tumour could therefore play an important role in treatment planning, enabling treatment to be targeted in such a way that higher doses of radiation are given to the more radioresistant tissue. Mapping the spatial distribution of oxygen in vivo is difficult. Radioactive tracers that are sensitive to different levels of oxygen are under development and in the early stages of clinical use. The concentration of these tracer chemicals can be detected via positron emission tomography resulting in a time dependent concentration profile known as a tissue activity curve (TAC). Pharmaco-kinetic models have then been used to deduce oxygen concentration from TACs. Some such models have included the fact that the spatial distribution of oxygen is often highly inhomogeneous and some have not. We show that the oxygen distribution has little impact on the form of a TAC; it is only the mean oxygen concentration that matters. This has significant consequences both in terms of the computational power needed, and in the amount of information that can be deduced from TACs.
Bradley DA, Hugtenburg RP, Hashim S, Okoya OO, Yusoff AL, Hassan AAM, Ramli AT, Wagiran H (2007) The development of doped radiosensitive glass, Solid State Science and Technology 909 pp. 9-18 AMER INST PHYSICS
Abdul Sani SF, Grime GW, Palitsin V, Mahdiraji GA, Abdul Rashid HA, Maah MJ, Bradley DA (2015) Micro-PIXE analysis of doped SiO2 fibres intended as TL dosimeters for radiation measurements, X-Ray Spectrometry 44 (2) pp. 33-40
© 2014 John Wiley & Sons, Ltd.Sample elemental concentrations can be determined using the microbeam proton-induced X-ray emission (PIXE) technique, providing non-destructive simultaneous low-background multi-element analysis. Present interest concerns analysis of Ge-doped SiO2 fibres intended as high spatial-resolution thermoluminescence (TL) dosimeters for radiation measurements in place of their more typical applications in telecommunications. During fibres fabrication, defined amounts of the Ge dopant are added, the dopant more usually having a determining role in the transmission properties of the fibre. Characteristic X-rays produced in PIXE analysis provide information on the relative distribution of elements within a sample, as in for instance Ge and Si concentrations, the Ge acting as point defect centres that promote TL. With the dopant tending to diffuse in and away from the fibre core, it is essential to define the sample matrix composition in order to accurately evaluate the X-ray yield. This is determined in part using simultaneous Rutherford Back Scattering analysis. In present work, PIXE/Rutherford Back Scattering measurements have been employed to ascertain dopant concentrations of fibres that have been fabricated at the University of Malaya with a view to improving TL yield. Present results concern cylindrical fibres, nominally with 4%, 6% and 8% weight peak Ge concentrations and flat fibres of nominal 6% weight Ge concentration. For the cylindrical fibres, Ge dopant concentration has been found to be in the range of 2.41-4.56%, 6.44-8.29% and 10.27-12.25% weight, respectively, while for the flat fibres, the Ge concentration range is broader, at 0.07-6.55% weight.
Hugtenburg RP, Adegunloye AS, Bradley DA (2010) X-ray microbeam radiation therapy calculations, including polarisation effects, with the Monte Carlo code EGS5, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 221-224 ELSEVIER SCIENCE BV
Malain D, Regan PH, Bradley DA, Matthews M, Al-Sulaiti HA, Santawamaitre T (2012) An evaluation of the natural radioactivity in Andaman beach sand samples of Thailand after the 2004 tsunami., Appl Radiat Isot 70 (8) pp. 1467-1474
Following the 2004 'Boxing day' tsunami, a determination has been made of the activity concentrations of (226)Ra, (232)Th and (40)K in beach sand samples which have been collected from various locations along the Andaman coast of the Thai peninsula. Use has been made of a HPGe detector-based, low-background gamma-ray counting system. The natural radioactivity levels of (226)Ra, (232)Th and (40)K measured from these samples was found to lie in the range 1.6-52.5, 0.3-73.9 and 2.8-1111.9Bq/kg respectively for the west coast and 3.5-83.1, 4.5-42.0, and 9.6-1376 Bq/kg respectively for the east coast. The radioactivity concentrations of (226)Ra, (232)Th and (40)K along the Andaman coast are comparable to that of the east coast, which was not exposed to the tsunami. The corresponding annual effective dose varies from 1.6-105.9 ¼Sv/y with a mean value of 59.1 ± 0.3 ¼Sv/y, significantly lower than the worldwide average as reported by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (2000).
Bajoga A, Alazemi N, Regan P, Bradley D (2015) Radioactive investigation of NORM samples from Southern Kuwait soil using high-resolution gamma-ray spectroscopy, RADIATION PHYSICS AND CHEMISTRY 116 pp. 305-311 PERGAMON-ELSEVIER SCIENCE LTD
Issa F, Hugtenburg RP, Bradley DA, Nisbet A (2011) Investigating radionuclide source shielding performance using Ge-doped optical fibre thermoluminescence dosimeters, AIP Conference Proceedings 1423 pp. 401-405 American Institute of Physics
Mahdirajia GA, Ghomeishi M, Dermosesian E, Hashim S, Ung NM, Adikan FRM, Bradley DA (2015) Optical fiber based dosimeter sensor: Beyond TLD-100 limits, Sensors and Actuators, A: Physical 222 pp. 48-57
© 2014 Elsevier B.V. All rights reserved.This work investigates the suitability of single mode optical fibers (SMFs) as ionizing radiation dosimeter sensors. Thermoluminescence (TL) response studies have been carried out to investigate the performance of two commercial optical fibers, SMF-1 and SMF-2, with different Ge-doping concentrations of 4.9 and 4.3 wt%, respectively, exposed to 0.5 to 8 Gy doses under 6, 9, and 20 MeV electron radiations. The performance parameters include dose response linearity and sensitivity, energy dependency, glow curve analysis, minimum detectable dose, repeatability, fading effects and optical absorption. The TL dose response of SMF-1, the .ber with the greater Ge concentration of the two, was found to be in excess of 6.3 and 3.2 times that of SMF-2 and TLD-100, respectively. SMF-1 demonstrated capability for detecting a minimum dose of as low as 6 mGy, being some 3.2 times superior to that of TLD-100. The results underline the potential of these optical fibers as next-generation alternative dosimeter sensors for detection of ionizing radiation.
Alkhateeb SM, Abdelkader MH, Bradley DA, Seller P, Veale MC, Wilson MD, Pani S (2013) Energy dispersive X-ray diffraction computed tomography of breastsimulating phantoms and a tissue sample, Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8668
Breast lesions and normal tissue have different characteristics of density and molecular arrangement that affect their diffraction patterns. X-ray diffraction can be used to determine the spatial structure of such tissues at the atomic and molecular level and Energy Dispersive X-Ray Diffraction Computed Tomography (EDXRDCT) can be used to produce 2-dimensional images of cross sections of the samples. The purpose of this work is to use an EDXRDCT system to find the limiting visibility for details that simulate breast lesions. Results are presented for EDXRDCT images of samples of different materials simulating breast tissue contrast and shapes. For simple circular details, the contrast between details and background in the images was measured with the goal of simulating the contrast between real breast tissue components. The limiting visible diameter was measured as a function of detail diameter for different combinations of scanning and geometrical parameters. Images of more complex test objects were assessed in terms of both contrast and accuracy of shape reproduction, evaluating the feasibility of using shape analysis as an additional parameter for lesion identification. The optimum combination of parameters are intended to be applied to the scanning of waxed breast tissue blocks. © 2013 SPIE.
Bradley DA, Wells K (2014) Reprint of: Biomedical applications reviewed: Hot topic areas, Radiation Physics and Chemistry 95 pp. 191-201
Making reference to the British Journal of Radiology and competitor journal titles, we look at the general area of biomedical physics, reviewing some of the associated topics in ionising radiation research attracting interest over the past 2 years. We also reflect on early developments that have paved the way for these endeavours. The talk is illustrated by referring to a number of biomedical physics areas in which this group has been directly involved, including novel imaging techniques that address compositional and structural makeup as well as use of elastically scattered X-ray phase contrast, radiation damage linking to possible pericardial effects in radiotherapy, simulation of microvascularity and oxygenation with a focus of radiation resistant hypoxic tumours, issues of high spatial resolution dosimetry and tissue interface radiotherapy with doses enhanced through use of high atomic number photoelectron conversion media. © 2013 Elsevier Ltd.
Loveland J, Gundogdu O, Morton E, Wells K, Bradley DA (2010) Phase contrast imaging: Effect of increased object-detector distances at X-ray diagnostic and megavoltage energies, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issa F, Nisbet A, Bradley DA, Hugtenburg RP (2013) Novel high resolution I brachytherapy source dosimetry using Ge-doped optical fibres, Radiation Physics and Chemistry
The steep dose gradients close to brachytherapy sources limit the ability to obtain accurate measurements of dose. Here we use a novel high spatial resolution dosimeter to measure dose around a I source and compare against simulations. Ge-doped optical fibres, used as thermoluminescent dosimeters, offer sub-mm spatial resolution, linear response from 10 cGy to >1 kGy and dose-rate independence. For a I brachytherapy seed in a PMMA phantom, doses were obtained for source-dosimeter separations from 0.1 cm up to several cm, supported by EGSnrc/DOSRZznrc Monte Carlo simulations and treatment planning system data. The measurements agree with simulations to within 2.3%±0.3% along the transverse and perpendicular axes and within 3.0%±0.5% for measurements investigating anisotropy in angular dose distribution. Measured and Veriseed" brachytherapy treatment planning system (TPS) values agreed to within 2.7%±0.5%. Ge-doped optical fibre dosimeters allow detailed dose mapping around brachytherapy sources, not least in situations of high dose gradient. © 2013 Elsevier Ltd.
Bradley DA (2013) Subtle signs, subtle designs: future change and the BJR., Br J Radiol
Al-Ahbabi SS, Bradley DA, Nisbet A (2013) Tomotherapy evaluation for head and neck cases using two types of phantoms, Radiation Physics and Chemistry
The use of rotational therapy as an important method of treatment delivery is expected to increase due in a large part to the development and utilisation of tomotherapy. Rotational therapy minimises the occurrence of hotspots and the irradiation of critical organs, providing more uniform dosing while sparing critical organs. Two important characteristics of rotational radiation are its dynamic nature and dosimetric variability in radiation delivery, both of which present a considerable challenge for clinical physicists seeking appropriate tools to meet the demands of quality assurance. In this paper 15 Delivery Quality Assurance (DQA) plans of head and neck patients were assessed for the Hi-Art tomotherapy system using Kodak X-Omat V film and an A1SL Ref F92722 ion chamber versus MapCheck. Absolute dose measurement showed average differences of 3.42 cGy and 98% Gamma (³) factor for the Cheese phantom technique. For the MapCheck technique the average difference and Gamma factor were 0.74 cGy and 96%, respectively. Gamma (³) matrix distribution was used to evaluate the difference between measured and calculated dose distribution. © 2013 Elsevier Ltd. All rights reserved.
Noor NM, Shukor NA, Nisbet A, Bradley DA, Hussein M, Nisbet A, Bradley DA (2012) Comparison of the TL fading characteristics of Ge-doped optical fibres and LiF dosimeters, Applied Radiation and Isotopes
Fading is important in choosing appropriate thermoluminescence (TL) materials for particular applications. Comparison is made herein of changes due to fading in the TL yield of Ge-doped fibres and lithium fluoride (LiF) dosimeters, for varying temperature and dose. The fading is independent of dose for all investigated dosimeters while the loss in TL yield reduces for lower storage temperatures. At room temperature and for 133 days of storage, a maximum signal loss of 5% has been observed for both forms of LiF dosimeter, while 9 and 50 ¼m core diameter Ge-doped fibres produced a loss of 11% and 8%, respectively. © 2011 Elsevier Ltd.
Santawamaitre T, Malain D, Al-Sulaiti HA, Matthews M, Bradley DA, Regan PH (2011) Study of natural radioactivity in riverbank soils along the Chao Phraya river basin in Thailand, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 920-924
Levels of naturally occurring radioactivity in surface soils along the Chao Phraya river have been investigated. The activity concentrations of radionuclides in the 238U and 232Th decay chains and from 40K were determined through gamma-ray spectrometry measurements made using a hyperpure germanium detector in a low background configuration. Activity concentrations of 238U, 232Th and 40K were found to be 55.3±1.2”65.2±1.4, 60.7±1.2”69. 1±1.3 and 393±13”478±16 Bq/kg, respectively. Concerning radiological risk, the absorbed gamma dose rate in air from those soils was estimated to lie in the range 81.6±1.9”90.4±2.1 nGy/h; the outdoor annual effective dose equivalent was calculated to be 100.1±2.3”110.8±2.5 ¼Sv/yr. These results are compared with radioactivity measurements with world mean values. © 2010 Elsevier B.V.
Alawiah A, Intan AM, Bauk S, Abdul-Rashid HA, Yusoff Z, Mokhtar MR, Wan Abdullah WS, Mat Sharif KA, Mahdiraji GA, Mahamd Adikan FR, Tamchek N, Noor NM, Bradley DA (2013) Thermoluminescence characteristics of flat optical fiber in radiation dosimetry under different electron irradiation conditions, Proceedings of SPIE - The International Society for Optical Engineering 8775
The thermoluminescence (TL) provided by flat optical fibers (FF) have been proposed as the basis for a novel radiation sensor, for use in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm3 and made of pure silica SiO2 was selected for this research. The FF was annealed at 400oC for 1 h before being irradiated. Using a linear accelerator (LINAC), delivering doses in the range 2.0-10.0 Gy, the kinetic parameters and dosimetric glow curve representing TL response of the FF were studied with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV. The TL response was read out using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80oC, maximum readout temperature of 400oC and a heating rate of 30oCs-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used LiF:MgTi dosimeter, for application in medical radiotherapy application. © 2013 SPIE.
Al-Sulaiti H, Regan PH, Bradley DA, Malain D, Santawamaitre T, Habib A, Matthews M, Bukhari S, Al-Dosari M (2010) A preliminary report on the determination of natural radioactivity levels of the State of Qatar using high-resolution gamma-ray spectrometry, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 427-431 ELSEVIER SCIENCE BV
This work considers a previously overlooked uncertainty present in film dosimetry which results from moderate curvature of films during the scanning process. Small film samples are particularly susceptible to film curling which may be undetected or deemed insignificant. In this study, we consider test cases with controlled induced curvature of film and with film raised horizontally above the scanner plate. We also evaluate the difference in scans of a film irradiated with a typical brachytherapy dose distribution with the film naturally curved and with the film held flat on the scanner. Typical naturally occurring curvature of film at scanning, giving rise to a maximum height 1 to 2 mm above the scan plane, may introduce dose errors of 1% to 4%, and considerably reduce gamma evaluation passing rates when comparing film-measured doses with treatment planning system-calculated dose distributions, a common application of film dosimetry in radiotherapy. The use of a triple-channel dosimetry algorithm appeared to mitigate the error due to film curvature compared to conventional single-channel film dosimetry. The change in pixel value and calibrated reported dose with film curling or height above the scanner plate may be due to variations in illumination characteristics, optical disturbances, or a Callier-type effect. There is a clear requirement for physically flat films at scanning to avoid the introduction of a substantial error source in film dosimetry. Particularly for small film samples, a compression glass plate above the film is recommended to ensure flat-film scanning. This effect has been overlooked to date in the literature.
Hashim S, Alajerami YSM, Ghoshal SK, Saleh MA, Saripan MI, Kadir ABA, Bradley DA, Alzimami K (2014) Dosimetric characteristics of LKB:CU,P solid TL detector, Radiation Physics and Chemistry 104 pp. 36-39
The dosimetric characteristics of newly developed borate glass dosimeter modified with lithium and potassium carbonate (LKB) and co-doped with CuO and NH4H2PO4 are reported. Broad peaks in the absence of any sharp peak confirms the amorphous nature of the prepared glass. A simple glow curve of Cu doped sample is observed with a single prominent peak (Tm) at 220°C. The TL intensity response shows an enhancement of ~100 times due to the addition of CuO (0.1mol%) to LKB compound. A further enhancement of the intensity by a factor of 3 from the addition of 0.25mol% NH4H2PO4 as a co-dopant impurity is attributed to the creation of extra electron traps with consequent increase in energy transfer of radiation recombination centers. The TL yield performance of LKB:Cu,P with Zeff H8.92 is approximately seventeen times less sensitive compared to LiF:Mg,Ti (TLD-100). The proposed dosimeter shows good linearity up to 103Gy, minimal fading and photon energy independence. These attractive features offered by our dosimeter is expected to pave the way towards dosimetric applications. © 2013 Elsevier Ltd.
Hashim S, Bradley DA, Saripan MI, Ramli AT, Wagiran H (2010) The thermoluminescence response of doped SiO2 optical fibres subjected to fast neutrons, APPLIED RADIATION AND ISOTOPES 68 (4-5) pp. 700-703 PERGAMON-ELSEVIER SCIENCE LTD
Yalcin S, Gurler O, Gundogdu O, Bradley DA (2012) A practical method for in-situ thickness determination using energy distribution of beta particles, APPLIED RADIATION AND ISOTOPES 70 (1) pp. 128-132 Elsevier
Alajerami YSM, Hashim S, Ghoshal SK, Ramli AT, Saleh MA, Ibrahim Z, Kadni T, Bradley DA (2013) Luminescence characteristics of Li2CO3-K2CO3-H3BO3 glasses co-doped with TiO2/MgO, Applied Radiation and Isotopes 82 pp. 12-19
Understanding the influence of co-dopants in the luminescence enhancement of carbonate glasses is the key issue in dosimetry. A series of borate glasses modified by lithium and potassium carbonate were synthesized by the melt-quenching method. The glass mixture activated with various concentrations of TiO2 and MgO was subjected to various doses of gamma-rays (60Co). The amorphous nature of the samples was confirmed by x-ray diffraction (XRD) spectra. The simple glowing curve of the glass doped with TiO2 features a peak at 230°C, whose intensity is maximal at 0.5mol% of the dopant. The intensity of the glowing curve increases with the concentration of MgO added as a co-dopant up to 0.25mol%, where it is two times higher than for the material without MgO thermoluminescence properties, including dose response, reproducibility, and fading were studied. The effective atomic number of the material was also determined. Kinetic parameters, such as kinetics order, activation energy, and frequency factor are estimated. The photoluminescence spectra of the titanium-doped glass consist of a prominent peaks at 480nm when laser excitation at 650nm is used. A three-fold photoluminescence enhancement and a blue shift of the peak were observed when 0.1% MgO was introduced. In addition, various physical parameters, such as ion concentration, polaron radius and internuclear distances were calculated. The mechanism for the thermoluminescence and photoluminescence enhancements are discussed. © 2013 Elsevier Ltd.
Alajerami YSM, Hashim S, Ghoshal SK, Saleh MA, Kadni T, Saripan MI, Alzimami K, Ibrahim Z, Bradley DA (2013) The effect of TiO2 and MgO on the thermoluminescence properties of a lithium potassium borate glass system, Journal of Physics and Chemistry of Solids 74 (12) pp. 1816-1822
The influence of dopant TiO2 and co-dopant MgO on the thermoluminescence (TL) properties of lithium potassium borate glass (LKB) is reported in this paper. The glow curve exhibits a prominent peak (Tm) at 230 C. The TL intensity was enhanced by a factor of ~3 due to the incorporation of MgO, and this was attributed to the creation of extra electron traps mediated by radiative recombination energy transfer. We achieved good linearity of the TL yield with dose, low fading, excellent reproducibility and a promising effective atomic number (Zeff=8.89), all of which are highly suitable for dosimetry. The effect of heating rate, sunlight and dose rate on the TL are also examined. These attractive features demonstrate that our dosimeter is useful in medical radiation therapy. © 2013 Elsevier Ltd.
Yalcin S, Gurler O, Gundogdu O, Bradley DA (2012) A practical method for in-situ thickness determination using energy distribution of beta particles, Applied Radiation and Isotopes 70 (1) pp. 128-132
This paper discusses a method to determine the thickness of an absorber using the energy distribution of beta particles. An empirical relationship was obtained between the absorber thickness and the energy distribution of beta particles transmitted through. The thickness of a polyethylene radioactive source cover was determined by exploiting this relationship, which has largely been left unexploited allowing us to determine the in-situ cover thickness of beta sources in a fast, cheap and non-destructive way. © 2011 Elsevier Ltd.
Jafari SM, Alalawi AI, Hussein M, Alsaleh W, Najem MA, Hugtenburg RP, Bradley DA, Spyrou NM, Clark CH, Nisbet A (2014) Glass beads and Ge-doped optical fibres as thermoluminescence dosimeters for small field photon dosimetry., Phys Med Biol 59 (22) pp. 6875-6889
An investigation has been made of glass beads and optical fibres as novel dosimeters for small-field photon radiation therapy dosimetry. Commercially available glass beads of largest dimension 1.5 mm and GeO2-doped SiO2 optical fibres of 5 mm length and 120 µm diameter were characterized as thermoluminescence dosimeters. Results were compared against Monte-Carlo simulations with BEAMnrc/DOSXYZnrc, EBT3 Gafchromic film, and a high-resolution 2D-array of liquid-filled ionization chambers. Measurements included relative output factors and dose profiles for square-field sizes of 1, 2, 3, 4, and 10 cm. A customized Solid-Water® phantom was employed, and the beads and fibres were placed at defined positions along the longitudinal axis to allow accurate beam profile measurement. Output factors and the beam profile parameters were compared against those calculated by BEAMnrc/DOSXYZnrc. The output factors and field width measurements were found to be in agreement with reference measurements to within better than 3.5% for all field sizes down to 2 cm2 for both dosimetric systems, with the beads showing a discrepancy of no more than 2.8% for all field sizes. The results confirm the potential of the beads and fibres as thermoluminescent dosimeters for use in small photon radiation field sizes.
Jeynes JCG, Webb M, Kirkby KJ, Kirkby NF, Bradley DA (2009) Proceedings of the First International Conference on Biomedical Applications of High Energy Ion Beams Preface, APPLIED RADIATION AND ISOTOPES 67 (3) pp. 369-370 PERGAMON-ELSEVIER SCIENCE LTD
Hashim S, Saripan MI, Rahman ATA, Yaakob NH, Bradley DA, Alzimami K (2013) Effective atomic number of Ge-doped and Al-doped optical fibers for radiation dosimetry purposes, IEEE Transactions on Nuclear Science 60 (2) pp. 555-559
Optical fibers have been demonstrated by this group to show promising thermoluminescence (TL) properties with respect to ionizing radiation. Present research has focused on commercially produced single-mode telecommunication optical fibers manufactured by CorActive (Canada) either in the form of SiO 2 optical fibers doped with either Ge or Al. Control of radiation dose is essential in performing an experiment in a biomedical context. One important aspect in this is the tissue equivalence of the dosimetric material. Mixtures or compounds that are similar in their radiation interaction characteristics to the soft tissue, bone or any other body constituents can be identified for this purpose. Effective atomic number of a medium prescribes its detection efficiency and tissue equivalence. To obtain the effective atomic number of the doped fibers, SEM (Scanning Electron Microscope) and EDXRS (Energy Dispersive X-ray Spectroscopy) analysis was performed to acquire the composition of the element inside the optical fibers. From our investigation, the value of Zeff is in the range of 11.5-13.4 and 11.7-13.7 for Ge-doped and Al-doped respectively (value of Zeff in soft tissue is 7.5 and Zeff for bone is between 11.6-13.8). Given that Ge- and Al-doped optical fibers are not soft-tissue equivalent, the assessment of dose deposition in such media would need to be corrected for an expected over-response. However, the value of Zeff is within the range of bone, making the optical fiber a strong candidate for use in skeletal radiation dosimetry. © 1963-2012 IEEE.
Daar E, Kaabar W, Woods E, Lei C, Nisbet A, Bradley DA (2014) Atomic force microscopy and mechanical testing of bovine pericardium irradiated to radiotherapy doses, Radiation Physics and Chemistry 96 pp. 176-180
Within the context of radiotherapy our work investigates the feasibility of identifying changes in structural and biomechanical properties of pericardium resulting from exposure to penetrating photon irradiation. Collagen fibres extracted from bovine pericardium were chosen as a model of pericardium extracellular matrix as these form the main fibrous component of the medium. Tests of mechanical properties, controlled by the various structural elements of the tissues, were performed on frontal pericardium, including uni-axial tests and atomic force microscopy (AFM). While the irradiated collagen fibres showed no significant change in D-band spacing up to doses of 80. Gy, the fibre width was found to increase by 34±9% at 80. Gy when compared with that for un-irradiated samples. © 2013 Elsevier Ltd.
Gonçalves OD, Bradley DA (2013) ISRP-12: The 12th International Symposium on Radiation Physics, Radiation Physics and Chemistry
Hashim S, Alajerami YS, Ramli AT, Ghoshal SK, Saleh MA, Abdul Kadir AB, Saripan MI, Alzimami K, Bradley DA, Mhareb MH (2014) Thermoluminescence dosimetry properties and kinetic parameters of lithium potassium borate glass co-doped with titanium and magnesium oxides., Appl Radiat Isot 91 pp. 126-130
Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of (60)Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230 °C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Z(eff)=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 10(3) Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software.
Noor NM, Jusoh MA, Razis AFA, Alawiah A, Bradley DA (2015) Flat Ge-doped Optical Fibres for Food Irradiation Dosimetry, NATIONAL PHYSICS CONFERENCE 2014 (PERFIK 2014) 1657 AMER INST PHYSICS
Bradley DA, Mahdiraji GA, Ghomeishi M, Dermosesian E, Adikan FR, Rashid HA, Maah MJ (2014) Enhancing the radiation dose detection sensitivity of optical fibres., Appl Radiat Isot 100 pp. 43-49
A method for improving the thermoluminescence (TL) yield of silica-based optical fibres is demonstrated. Using silica obtained from a single manufacturer, three forms of pure (undoped) fibre (capillary-, flat-, and photonic crystal fibre (PCF)) and two forms of Ge-doped fibre (capillary- and flat-fibre) were fabricated. The pure fibre samples were exposed to 6 and 21MeV electrons, the doped fibres to 6MV photons. The consistent observation of large TL yield enhancement is strongly suggestive of surface-strain defects generation. For 6MeV irradiations of flat-fibre and PCF, respective TL yields per unit mass of about 12.0 and 17.5 times that of the undoped capillary-fibre have been observed. Similarly, by making a Ge-doped capillary-fibre into flat-fibre, the TL response is found to increase by some 6.0 times. Thus, in addition to TL from the presence of a dopant, the increase in fused surface areas of flat-fibres and PCF is seen to be a further important source of TL. The glow-curves of the undoped fibres have been analysed by computational deconvolution. Trap centre energies have been estimated and compared for the various fibre samples. Two trap centre types observed in capillary-fibre are also observed in flat-fibre and PCF. An additional trap centre in flat-fibre and one further trap centre in PCF are observed when compared to capillary fibre. These elevated-energy trap centres are linked with strain-generated defects in the collapsed regions of the flat fibre and PCF.
Yaakob NH, Wagiran H, Hossain MI, Ramli AT, Bradley DA, Hashim S, Ali H (2011) Thermoluminescence response of Ge- and Al-doped optical fibers subjected to low-dose electron irradiation, Journal of Nuclear Science and Technology 48 (7) pp. 1115-1117
Bradley DA, Hashim S, Cabello J, Wells K, Dunn WL (2010) Photon-induced positron annihilation for standoff bomb detection, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 415-418 ELSEVIER SCIENCE BV
Begum M, Rahman A, Abdul-Rashid H, Abdullah W, Noor N, Zulkifli M, Muhamad-Yasin S, Mat-Sharif K, Tamchek N, Nawi S, Wahib N, Amin Y, Bradley D (2013) Thermoluminescence response of Ge-doped optical fiber dosimeters with different core sizes, 4th International Conference on Photonics, ICP 2013 - Conference Proceeding pp. 291-293
Thermoluminescence (TL) properties of five different core diameter of 6 mol% germanium (Ge) doped optical fibers have been investigated for the purpose of TL dosimetry. The optical fiber dosimeter TL properties is compared with commercially available TLD-100 chips (LiF:Mg,Ti). Samples were irradiated using Cobalt-60 standard radiation source ranging from 1Gy to 10 Gy. These fibers show good linear dose response up to 10 Gy. Highest core diameter of Ge doped optical fiber (core 100 ¼m) provides the best response among all fibers. We observe the larger core fiber show better response than smaller core fiber. The relative sensitivity of 100 ¼m core optical fiber is 0.26 ± 0.04 with respect to TLD-100 chip. © 2013 IEEE.
Palmer AL, Nisbet A, Bradley DA (2013) Semi-3D dosimetry of high dose rate brachytherapy using a novel Gafchromic EBT3 film-array water phantom, 7TH INTERNATIONAL CONFERENCE ON 3D RADIATION DOSIMETRY (IC3DDOSE) 444 IOP PUBLISHING LTD
Sani SFA, Mahdiraji GA, Shafiqah ASS, Grime GW, Palitsin V, Hinder SJ, Tamchek N, Rashid HAA, Maah MJ, Watts JF, Bradley DA (2015) XPS and PIXE Analysis of Doped Silica Fibre for Radiation Dosimetry, JOURNAL OF LIGHTWAVE TECHNOLOGY 33 (11) pp. 2268-2278 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Alkhateeb SM, Abdelkader MH, Bradley DA, Pani S, Alkhateeb SM, Abdelkader MH, Bradley DA (2012) Breast tissue contrast-simulating materials using energy-dispersive X-ray diffraction, Applied Radiation and Isotopes
Breast lesions and normal tissues have different molecular arrangements that affect their diffraction patterns. Different mouldable and non-mouldable materials were analysed using an energy dispersive X-ray diffraction system based on a conventional X-ray source (operated at 70 kVp) and a CdTe detector (Amptek XT-100), including a conventional spectroscopic chain. Combinations of materials were identified to have a contrast comparable to that achieved in diffraction imaging for different breast tissues at the momentum transfer values carrying the greatest amount of information (1.1 nm
and 1.6 nm
). © 2012 Elsevier Ltd. All rights reserved.
Habib AS, Regan PH, Bradley DA, Matthews MC, Shutt AL, Alsulaiti H (2013) Characterization of naturally occurring radioactive materials in Libyan oil pipe scale using a germanium detector and Monte Carlo simulation, Radiation Physics and Chemistry
Radioactive scale formation in various oil production facilities is acknowledged to pose a potential significant health and environmental issue. The presence of such an issue in Libyan oil fields was recognized as early as 1998. The naturally occurring radioactive materials (NORM) involved in this matter are radium isotopes (Ra and Ra) and their decay products, precipitating into scales formed on the surfaces of production equipment. A field trip to a number of onshore Libyan oil fields has indicated the existence of elevated levels of specific activity in a number of locations in some of the more mature oil fields. In this study, oil scale samples collected from different parts of Libya have been characterized using gamma spectroscopy through use of a well shielded HPGe spectrometer. To avoid potential alpha-bearing dust inhalation and in accord with safe working practices at this University, the samples, contained in plastic bags and existing in different geometries, are not permitted to be opened. MCNP, a Monte Carlo simulation code, is being used to simulate the spectrometer and the scale samples in order to obtain the system absolute efficiency and then to calculate sample specific activities. The samples are assumed to have uniform densities and homogeneously distributed activity. Present results are compared to two extreme situations that were assumed in a previous study: (i) with the entire activity concentrated at a point on the sample surface proximal to the detector, simulating the sample lowest activity, and; (ii) with the entire activity concentrated at a point on the sample surface distal to the detector, simulating the sample highest activity. © 2013 Elsevier Ltd.
Gundogdu O, Nirgianaki E, Che Ismail E, Jenneson PM, Bradley DA (2007) Benchtop phase-contrast X-ray imaging., Appl Radiat Isot 65 (12) pp. 1337-1344
Clinical radiography has traditionally been based on contrast obtained from absorption when X-rays pass through the body. The contrast obtained from traditional radiography can be rather poor, particularly when it comes to soft tissue. A wide range of media of interest in materials science, biology and medicine exhibit very weak absorption contrast, but they nevertheless produce significant phase shifts with X-rays. The use of phase information for imaging purposes is therefore an attractive prospect. Some of the X-ray phase-contrast imaging methods require highly monochromatic plane wave radiation and sophisticated X-ray optics. However, the propagation-based phase-contrast imaging method adapted in this paper is a relatively simple method to implement, essentially requiring only a microfocal X-ray tube and electronic detection. In this paper, we present imaging results obtained from two different benchtop X-ray sources employing the free space propagation method. X-ray phase-contrast imaging provides higher contrast in many samples, including biological tissues that have negligible absorption contrast.
Alalawi AI, Hugtenburg RP, Abdul Rahman AT, Barry MA, Nisbet A, Alzimami KS, Bradley DA (2013) Measurement of dose enhancement close to high atomic number media using optical fibre thermo luminescence dosimeters, Radiation Physics and Chemistry
Present interest concerns development of a system to measure photoelectron-enhanced dose close to a tissue interface using analogue gold-coated doped silica-fibre thermo luminescence detectors and an X-ray set operating at 250 kVp. Study is made of the dose enhancement factor for various thickness of gold; measurements at a total gold thickness of 160 nm produces a mean dose enhancement factor of 3.19. To verify results, simulations of the experimental setup have been performed. © 2013 Elsevier Ltd. All rights reserved.
Santawamaitre T, Regan PH, Bradley DA, Matthews M, Malain D, Al-Sulaiti HA (2010) An evaluation of the level of naturally occurring radioactive material in soil samples along the Chao Phraya river basin, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 453-456 ELSEVIER SCIENCE BV
Alanazi A, Alkhorayef M, Alzimami K, Jurewicz I, Abuhadi N, Dalton A, Bradley DA (2016) Carbon nanotubes buckypaper radiation studies for medical physics applications., Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine
Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In such circumstance, dosimeters with atomic number similar to human tissue are needed. Carbon nanotubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nanotubes (SWCNTs) buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2Gy. This finding suggests that carbon nanotubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance.
Bradley DA, Jafari SM, Siti Shafiqah AS, Tamcheck N, Shutt A, Siti Rozaila Z, Abdul Sani SF, Sabtu SN, Alanazi A, Amouzad Mahdiraji G, Abdul Rashid HA, Maah MJ (2015) Latest developments in silica-based thermoluminescence spectrometry and dosimetry., Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine
Using irradiated doped-silica preforms from which fibres for thermoluminescence dosimetry applications can be fabricated we have carried out a range of luminescence studies, the TL yield of the fibre systems offering many advantages over conventional passive dosimetry types. In this paper we investigate such media, showing emission spectra for irradiated preforms and the TL response of glass beads following irradiation to an (241)Am-Be neutron source located in a tank of water, the glass fibres and beads offering the advantage of being able to be placed directly into liquid. The outcomes from these and other lines of research are intended to inform development of doped silica radiation dosimeters of versatile utility, extending from environmental evaluations through to clinical and industrial applications.
Mohamed F, Bradley D, Winlove C (2006) Effects of ionizing radiation on extracellular matrix, Transactions of the American Nuclear Society 95 pp. 433-?
Uwatse OB, Olatunji MA, Khandaker MU, Amin YM, Bradley DA, Alkhorayef M, Alzimami K (2015) Measurement of Natural and Artificial Radioactivity in Infant Powdered Milk and Estimation of the Corresponding Annual Effective Dose, ENVIRONMENTAL ENGINEERING SCIENCE 32 (10) pp. 838-846 MARY ANN LIEBERT, INC
Abdul Rahman AT, Hugtenburg RP, Abdul Sani SF, Alalawi AIM, Issa F, Thomas R, Barry MA, Nisbet A, Bradley DA (2012) An investigation of the thermoluminescence of Ge-doped SiO 2 optical fibres for application in interface radiation dosimetry, Applied Radiation and Isotopes 70 (7) pp. 1436-1441
We investigate the ability of high spatial resolution (~120¼m) Ge-doped SiO 2 TL dosimeters to measure photoelectron dose enhancement resulting from the use of a moderate to high-Z target (an iodinated contrast media) irradiated by 90kVp X-rays. We imagine its application in a novel radiation synovectomy technique, modelled by a phantom containing a reservoir of I 2 molecules at the interface of which the doped silica dosimeters are located. Measurements outside of the iodine photoelectron range are provided for using a stepped-design that allows insertion of the fibres within the phantom. Monte Carlo simulation (MCNPX) is used for verification. At the phantom medium I 2-interface additional photoelectron generation is observed, ~60% above that in the absence of the I 2, simulations providing agreement to within 3%. Percentage depth doses measured away from the iodine contrast medium reservoir are bounded by published PDDs at 80kVp and 100kVp. © 2011 Elsevier Ltd.
Siti Shafiqah AS, Amin YM, Md Nor R, Tamchek N, Khairul Anuar MS, Abdul Rashid HA, Bradley DA (2015) Properties of ge-doped silica preform by raman spectroscopy, ARPN Journal of Engineering and Applied Sciences 10 (15) pp. 6214-6218
©2006-2015 Asian Research Publishing Network (ARPN).In the present work, the structural modifications of Ge-doped silica preforms due to ³-irradiation at room temperature have been investigated using Raman spectroscopy. The MCVD fabricated preforms labelled as P1 and P2 are distinguishable by the oxidation and thermal history during the fabrication process, in which related to the oxygen bonding of SiO4 tetrahedral. From Raman analysis, the 480 cm-1(D1) and 609 cm-1(D2) peaks are the main network features of pure and doped silica glass, suggest the formation of defect centers in the preforms. The structural modifications of this defects centers are more sensitive in P2, due to the oxygen deficient state of the preform.
Jafari SM, Jordan TJ, Distefano G, Bradley DA, Spyrou NM, Nisbet A, Clark CH (2015) Feasibility of using glass-bead thermoluminescent dosimeters for radiotherapy treatment plan verification, BRITISH JOURNAL OF RADIOLOGY 88 (1055) ARTN 20140804 BRITISH INST RADIOLOGY
Norbani NE, Abdullah Salim NA, Saat A, Hamzah Z, Ramli AT, Wan Idris WMR, Jaafar MZ, Bradley DA, Abdul Rahman AT (2014) Terrestrial gamma radiation dose rates (TGRD) from surface soil in Negeri Sembilan, Malaysia, Radiation Physics and Chemistry 104 pp. 112-117
Baseline data on background radiation levels allows for future assessment of possible changes in natural radionuclide concentrations, either as a result of geological processes or radioactive contamination. We have measured terrestrial gamma radiation dose-rates (TGRD) from surface soils throughout accessible areas in the Peninsular Malaysia state of Negeri Sembilan (NS). Dose rate measurements were carried out using a NaI (TI) scintillation survey meter, encompassing 1708 locations, covering about 73% of the 6645km2 of the land area in NS. This has allowed development of a TGRD contour map, plotted using WinSurf software. The range of measured TGRD was from 71±3nGy/h up to 1000±11nGy/h. The greatest measured TGRD was obtained in an area covered by soil types originating from igneous rock of granitic formations, while the least value of TGRD was observed in an area covered by limestone composed of calcite mineral, mostly found near river and coastal areas. Mean values of TGRD across the seven districts of NS ranged from 244±7nGy/h to 458±13nGy/h, the global mean being 330±8nGy/h compared to a mean value of 92nGy/h and 59nGy/h for Malaysia and the world, respectively. The average annual dose from such terrestrial gamma radiation dose-rates to an individual residing in NS, assuming a tropical rural setting, is estimated to be 0.96mSv per year. © 2014 Elsevier Ltd.
Fahimi A, Jurewicz I, Smith RJ, Sharrock CS, Bradley DA, Henley SJ, Coleman JN, Dalton AB (2013) Density controlled conductivity of pristine graphene films, Carbon 64 pp. 435-443
Single or few layer graphene can be considered an exciting pseudo-two-dimensional molecular material that potentially has a wide range of applications. A critical bottleneck may arise with issues in their controlled assembly into macroscopic ensembles over large areas both in two and three dimensions. Langmuir-type assembly is a particularly useful method to control and manipulate the distribution of graphene at the air-water interface via edge-edge interactions. In this study, pristine graphene suspended in organic solvent was prepared through adaptation of a previously developed process involving the non-invasive exfoliation of graphite. Successful deposition of graphene at the air-water interface was achieved by manipulating the vapor-pressure of the graphene dispersion through solvent mixing. Through careful control of density, by following the pressure-area isotherm during monolayer compression, it is possible to precisely tune the electrical conductivity. The resulting assemblies can be easily transferred to glass and other substrates using the Langmuir-Schaefer horizontal deposition method producing thin films with tunable electrical conductivity that exhibits percolation-type behavior. A major advantage of this process is that the conducting films require no further treatment unlike their graphene-oxide counterparts. Moreover, the physical properties of these assemblies can be easily controlled which is a precursor for graphene-based electronic applications. © 2013 Elsevier Ltd. All rights reserved.
Shams H, Bajoga AD, Alazemi N, Bradley DA, Regan PH (2015) A preliminary evaluation of naturally occurring radioactivity concentration levels across the State of Kuwait, APPLIED RADIATION AND ISOTOPES 109 pp. 479-481 PERGAMON-ELSEVIER SCIENCE LTD
Bajoga A, Bajoga A, Alazemi N, Alazemi N, Regan P, Regan P, Bradley D, Bradley D (2014) Radioactive investigation of NORM samples from Southern Kuwait soil using high-resolution gamma-ray spectroscopy, Radiation Physics and Chemistry
© 2015. Activity concentrations of soil and sand samples from southern part of Kuwait have been deduced for members of the 238U(226Ra) and 232Th(228Ac) decay chains, together with initial evaluations also provided of the concentrations for members of the 235U, 4n+1 chain. Additional activity concentration measurements have also been established for the single primordial radionuclide 40K and the anthropogenic radionuclides 137Cs from the same samples. The calculated activity concentration values and associated radiation hazard indices calculated were evaluated. The current results indicate activity concentrations ranging from 0.15±0.04 to 9.97±0.20Bq/kg for Cs. For 226Ra, 232Th and 40K this ranges from 9.02±0.13 to 17.48±0.18, 7.90±0.10 to 14.29±0.22, and 259.6±4.7 137Cs to 347.3±6.0Bq/kg, respectively. The mean values for dose rates, radium equivalent, hazard indices, and annual effective dose equivalent are 24.65±0.26nG/h, 50.72±0.50Bq/kg, 0.17, 0.14, and 30.0±0.3¼Sv/yr, respectively. These are compared with analogous measurements from other locations both in the Middle Eastern Region and far-afield.
Abdul Rahman AT, Nisbet A, Bradley DA (2011) Dose-rate and the reciprocity law: TL response of Ge-doped SiO2 optical fibers at therapeutic radiation doses, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 891-895
Abdul Rahman AT, Abdul Sani SF, Bradley DA (2011) Doped SiO 2 telecommunication fibre as a 1-D detector for radiation therapy dosimetry, AIP Conference Proceedings 1423 pp. 347-353 American Institute of Physics
Present studies concern Ge-doped SiO2 telecommunication fibre as a high spatial resolution 1-D thermoluminescence (TL) system for radiotherapeutic dosimetry. Using tube xray bremsstrahlung sources operating at kilovoltage energies, these fibres have been shown to offer linear response, from
Santawamaitre T, Malain D, Al-Sulaiti HA, Matthews M, Bradley DA, Regan PH (2011) Study of natural radioactivity in riverbank soils along the Chao Phraya river basin in Thailand, SORMA XII 2010: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 920-924 Elsevier
Habib AS, Shutt AL, Regan PH, Matthews MC, Alsulaiti H, Bradley DA (2014) Characterization of naturally occurring radioactive materials in Libyan oil pipe scale using a germanium detector and Monte Carlo simulation, Radiation Physics and Chemistry 95 pp. 352-355
Radioactive scale formation in various oil production facilities is acknowledged to pose a potential significant health and environmental issue. The presence of such an issue in Libyan oil fields was recognized as early as 1998. The naturally occurring radioactive materials (NORM) involved in this matter are radium isotopes (226Ra and 228Ra) and their decay products, precipitating into scales formed on the surfaces of production equipment. A field trip to a number of onshore Libyan oil fields has indicated the existence of elevated levels of specific activity in a number of locations in some of the more mature oil fields. In this study, oil scale samples collected from different parts of Libya have been characterized using gamma spectroscopy through use of a well shielded HPGe spectrometer. To avoid potential alpha-bearing dust inhalation and in accord with safe working practices at this University, the samples, contained in plastic bags and existing in different geometries, are not permitted to be opened. MCNP, a Monte Carlo simulation code, is being used to simulate the spectrometer and the scale samples in order to obtain the system absolute efficiency and then to calculate sample specific activities. The samples are assumed to have uniform densities and homogeneously distributed activity. Present results are compared to two extreme situations that were assumed in a previous study: (i) with the entire activity concentrated at a point on the sample surface proximal to the detector, simulating the sample lowest activity, and; (ii) with the entire activity concentrated at a point on the sample surface distal to the detector, simulating the sample highest activity. © 2013 Elsevier Ltd.
Akar Tarim U, Ozmutlu EN, Gurler O, Yalcin S, Gundogdu O, Sharaf JM, Bradley DA (2013) Monte Carlo modelling of single and multiple Compton scattering profiles in a concrete material, Radiation Physics and Chemistry 85 pp. 12-17
A Monte Carlo simulation study has been conducted of 60Co photons Compton scattered in concrete, illustrating the degraded energy spectra of gamma-ray radiation. Results are produced representing a NaI(Tl) detector model. We were able to analyse energy distributions of photons that reach the detector system after suffering several successive Compton scatterings in the target. The predicted decrease in intensity of single- and multiple-scattering peaks with increase in thickness of the target medium are in good agreement with experimental observations and findings reported by others. © 2012 Elsevier Ltd.
Shafiqah ASS, Amin YM, Nor RM, Bradley DA (2015) Effect of particle size on the thermoluminescence (TL) response of silica nanoparticles, RADIATION PHYSICS AND CHEMISTRY 117 pp. 102-107 PERGAMON-ELSEVIER SCIENCE LTD
Kaabar W, Gundogdu O, Tzaphlidou M, Janousch M, Attenburrow D, Bradley DA (2008) Investigation of essential element distribution in the equine metacarpophalangeal joint using a synchrotron radiation micro x-ray fluorescence technique, CURRENT ISSUES OF PHYSICS IN MALAYSIA 1017 pp. 18-24 AMER INST PHYSICS
Noor NM, Hussein M, Bradley DA, Nisbet A (2011) Investigation of the use of Ge-doped optical fibre for in vitro IMRT prostate dosimetry, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 819-823
In this study, the thermoluminescence (TL) yield of Ge-doped optical fibres for in vitro dosimetry has been investigated for the verification of Intensity Modulated Radiation Therapy (IMRT) three-dimensional (3D) dose distributions. Ge-doped optical fibres offer many advantages over conventional dosimetry systems including high sensitivity, minimal fading, and cost effectiveness. IMRT verification plans using the Varian Eclipse treatment planning system for two prostate cancer patients were created using Alderson Rando Anthropomorphic Phantom CT data-sets. Measurements were performed using the Rando phantom at nominal energies of 6 MV and 15 MV. Ge-doped optical fibre TL yields were compared with dose determined through use of the treatment planning system and also with the well-established TL lithium fluoride (LiF) dosimetry system (Harshaw TLD-100 and TLD-700). Results show the Ge-doped optical fibre to verify in vitro doses within 3% of the Eclipse predicted doses and LiF TLDs for the particular high energy photon beams used. © 2010 Elsevier B.V.
Al-Hinai KH, Benkara Mohd N, Rozullyah Zulkepely N, Md Nor R, Mohd Amin Y, Bradley DA (2013) A search for novel thermoluminescent radiation dosimeter media, Applied Radiation and Isotopes 82 pp. 126-129
We describe two example pilot efforts to help define new thermoluminescent dosimeter media. The first concerns ZnS:Mn nanophosphors, prepared by chemical precipitation using zinc and sodium sulfate, doped with manganese sulfate at concentrations varying from 1 to 3mol. The second concerns chemical vapor deposited diamond, produced as a thin film or as amorphous carbon on a single-crystal silicon substrate, each deposited under the same conditions, use being made of the hot filament-chemical vapor deposition (HFCVD) technique. The gas concentrations used were 1% CH4 in 99% H2 and 25% CH4 in 75% H2. Characterization of formations used FESEM, XRD and EDX. The nanophosphors consisted of particles of sizes in the range 85-150nm, the thermoluminescence (TL)-based radiation detection medium giving rise to a single peaked glow curve of maximum yield at a temperature of 250°C at a heating rate of 5°C/s. The TL response increased linearly with radiation dose, ZnS doped to 2mol of Mn being found the most sensitive. Regarding chemical vapor deposited (CVD) carbon, inappreciable TL was found for the resultant ball-like amorphous carbon films, graphite, and the silicon substrate, whereas CVD diamond films showed a promising degree of linearity with dose. For both the ZnS and diamond samples, TL signal fading was appreciable, being some 40% per day for ZnS and>50% per day for CVD films even under storage in the dark at room temperature, making it apparent that there is need to adjust parameters such as the size of nanoparticles. © 2013 Elsevier Ltd.
Issa F, Hugtenburg RP, Nisbet A, Bradley DA (2013) Novel high resolution 125I brachytherapy source dosimetry using Ge-doped optical fibres, Radiation Physics and Chemistry 92 pp. 48-53
The steep dose gradients close to brachytherapy sources limit the ability to obtain accurate measurements of dose. Here we use a novel high spatial resolution dosimeter to measure dose around a 125I source and compare against simulations. Ge-doped optical fibres, used as thermoluminescent dosimeters, offer sub-mm spatial resolution, linear response from 10cGy to >1kGy and dose-rate independence. For a 125I brachytherapy seed in a PMMA phantom, doses were obtained for source-dosimeter separations from 0.1cm up to several cm, supported by EGSnrc/DOSRZznrc Monte Carlo simulations and treatment planning system data. The measurements agree with simulations to within 2.3%±0.3% along the transverse and perpendicular axes and within 3.0%±0.5% for measurements investigating anisotropy in angular dose distribution. Measured and Veriseed" brachytherapy treatment planning system (TPS) values agreed to within 2.7%±0.5%.Ge-doped optical fibre dosimeters allow detailed dose mapping around brachytherapy sources, not least in situations of high dose gradient. © 2013 Elsevier Ltd.
Abdul Rahman AT, Abu Bakar NK, Chandra Paul M, Bradley DA (2014) Ultraviolet radiation (UVR) dosimetry system and the use of Ge-doped silica optical fibres, Radiation Physics and Chemistry 104 pp. 129-133
Previous studies have shown that over exposure to ultraviolet radiation (UVR), either from sunlight or artificial sources, can cause severe biological effects including cataracts, photokeratitis and skin cancer. In this respect, there exists the need to introduce a sensitive UV dosimetric material capable of measuring radiation dose to high accuracy in order to deliver UVR safely and efficiently. Present study has focussed on the investigation of the potential thermoluminescent (TL) sensitivity of commercially available germanium (Ge)-doped silica (SiO2) optical fibres subjected to UVR. The main interest of this study is to find out whether these doped SiO2 optical fibres can be used as a sensible integrator of environmental UV exposures. In the present study, commercially available Ge-doped SiO2 optical fibres have been used with a core diameter of 11¼m (CorActive, Canada), 23¼m (Central Glass and Ceramic Research Institute Kolkata, India) and 50¼m (Central Glass and Ceramic Research Institute Kolkata, India) and a cladding diameter of 125±0.1¼m, irradiated over a wide range of UV dose. Results have shown that these fibres exhibit a linear dose response (with correlation coefficient better than 0.9852). The 50¼m fibre produces greater TL response than that obtained for 11- and 23¼m fibres. The TL results are compared with that of the well-established TL dosimeter material lithium fluoride. © 2014 Elsevier Ltd.
Sabtu SN, Mahat RH, Amin YM, Price DM, Bradley DA, Maah MJ (2015) Thermo luminescence dating analysis at the site of an ancient brick structure at Pengkalan Bujang, Malaysia, APPLIED RADIATION AND ISOTOPES 105 pp. 182-187 PERGAMON-ELSEVIER SCIENCE LTD
Noor NM, Hussein M, Bradley DA, Nisbeta A (2010) The potential of Ge-doped optical fibre TL dosimetry for 3D verification of high energy IMRT photon beams, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 619 (1-3) pp. 157-162
Fahimi A, Jurewicz I, Sharrock CS, Bradley DA, Dalton AB, Smith RJ, Coleman JN, Henley SJ (2013) Density controlled conductivity of pristine graphene films, Carbon
Single or few layer graphene can be considered an exciting pseudo-two-dimensional molecular material that potentially has a wide range of applications. A critical bottleneck may arise with issues in their controlled assembly into macroscopic ensembles over large areas both in two and three dimensions. Langmuir-type assembly is a particularly useful method to control and manipulate the distribution of graphene at the air-water interface via edge-edge interactions. In this study, pristine graphene suspended in organic solvent was prepared through adaptation of a previously developed process involving the non-invasive exfoliation of graphite. Successful deposition of graphene at the air-water interface was achieved by manipulating the vapor-pressure of the graphene dispersion through solvent mixing. Through careful control of density, by following the pressure-area isotherm during monolayer compression, it is possible to precisely tune the electrical conductivity. The resulting assemblies can be easily transferred to glass and other substrates using the Langmuir-Schaefer horizontal deposition method producing thin films with tunable electrical conductivity that exhibits percolation-type behavior. A major advantage of this process is that the conducting films require no further treatment unlike their graphene-oxide counterparts. Moreover, the physical properties of these assemblies can be easily controlled which is a precursor for graphene-based electronic applications. © 2013 Elsevier Ltd. All rights reserved.
Bradley DA, Moger CJ, Winlove CP (2007) Zn deposition at the bone-cartilage interface in equine articular cartilage, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 580 (1) pp. 473-476 ELSEVIER SCIENCE BV
Amin YM, Uddin Khandaker M, Shyen AKS, Mahat RH, Nor RM, Bradley DA (2013) Radionuclide emissions from a coal-fired power plant, Applied Radiation and Isotopes 80 pp. 109-116
Current study concerns measurement of radioactivity levels in areas surrounding a 2420MW thermal power plant fueled predominantly by bituminous coal. The concentrations of 226Ra, 232Th and 40K in onsite bottom-ash were found to be 139Bq/kg, 108Bq/kg and 291Bq/kg, respectively, the levels for these radiolnuclides in soil decreasing with distance from the power plant. At the plant perimeter the respective radionuclide concentrations were 87Bq/kg, 74Bq/kg and 297Bq/kg. In a nearby town, the corresponding concentrations were 104Bq/kg, 52Bq/kg and 358Bq/kg, suggestive of use of TENORM affected soils. The mean radium equivalent activities (Raeq) in soil and ash sample in the town were 205Bq/kg and 316Bq/kg, respectively. The Kapar plant ash/slag appears to contain a higher level of TENORM than the world average. The degree of contamination is much higher inside the town where slag has been mixed with topsoil as landfill or as simple domestic waste. For the prevailing levels of exposure and a worst case senario, the predicted committed effective dose due to ingestion and inhalation for intake durations of 1- and 30 years would be 4.2¼Sv and 220¼Sv, respectively. © 2013 Elsevier Ltd.
Bradley DA, Hugtenburg RP, Yusoff AL (2006) Near-edge elastic photon scattering from dilute aqueous ions, RADIATION PHYSICS AND CHEMISTRY 75 (12) pp. 2129-2135 PERGAMON-ELSEVIER SCIENCE LTD
Mahdiraji GA, Adikan FRM, Bradley DA (2015) Collapsed optical fiber: A novel method for improving thermoluminescence response of optical fiber, Journal of Luminescence 161 pp. 442-447
©2015 Elsevier B.V. All rights reserved.A new technique is shown to provide improved thermoluminescence (TL) response from optical fibers, based on collapsing down hollow capillary optical fibers (COF) into flat fibers (FF), producing fused inner walls and consequent defects generation. Four different fused silica preform tubes are used to fabricate in-house COFs and FFs, i.e., ultra-pure (F300), relatively pure silica (PS), germanium-doped (Ge), and Ge-Boron-doped (GeB). The optical fibers are then subjected to 6 MeV electron irradiation. While the results show similar TL response from F300-COF and -FF, the TL response of PS-COF is improved by a factor of 6 by collapsing it down to a FF. By doping Ge into the F300 tube, the TL response of the resultant Ge-COF shows an improvement of 3 times over that of F300-COF, while an improvement of a factor of 12 is obtained by producing a Ge-FF. In GeB preform, by collapsing the capillary fiber into a FF, an improvement in TL response of 31 times that of GeB-COF is obtained. TL glow curve analysis shows an additional peak to be generated in the FFs compared to that observed in the COFs. The TL intensity value of the new peak is significantly increased in the doped FFs compared to the undoped FFs. The results suggest that defects generation occurs as a result of the fusing/collapsing technique, providing a TL response from the optical fibers that can substantially improve upon that of existing TL system sensitivities.
Begum M, Rahman AK, Abdul-Rashid HA, Yusoff Z, Begum M, Mat-Sharif KA, Amin YM, Bradley DA (2014) Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry., Appl Radiat Isot 100 pp. 79-83
Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples
Hashim S, Omar SSC, Ibrahim SA, Hassan WMSW, Ung NM, Mahdiraji GA, Bradley DA, Alzimami K (2015) Thermoluminescence response of flat optical fiber subjected to 9 MeV electron irradiations, Radiation Physics and Chemistry 106 pp. 46-49
We describe the efforts of finding a new thermoluminescent (TL) media using pure silica flat optical fiber (FF). The present study investigates the dose response, sensitivity, minimum detectable dose and glow curve of FF subjected to 9. MeV electron irradiations with various dose ranges from 0 Gy to 2.5 Gy. The above-mentioned TL properties of the FF are compared with commercially available TLD-100 rods. The TL measurements of the TL media exhibit a linear dose response over the delivered dose using a linear accelerator. We found that the sensitivity of TLD-100 is markedly 6 times greater than that of FF optical fiber. The minimum detectable dose was found to be 0.09 mGy for TLD-100 and 8.22 mGy for FF. Our work may contribute towards the development of a new dosimeter for personal monitoring purposes. © 2014 Elsevier Ltd.
Malain D, Regan PH, Bradley DA, Matthews M, Santawamaitre T, Al-Sulaiti HA (2010) Measurements of NORM in beach sand samples along the Andaman coast of Thailand after the 2004 tsunami, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 441-445 ELSEVIER SCIENCE BV
Geraki K, Farquharson MJ, Bradley DA, Gundogdu O, Falkenberg G (2008) The localisation of biologically important metals in soft and calcified tissues using a synchrotron x-ray fluorescence technique, X-RAY SPECTROMETRY 37 (1) pp. 12-20 JOHN WILEY & SONS LTD
Abdul Sani SF, Alalawi AI, Nisbet A, Bradley DA, Azhar A R H, Amouzad Mahdiraji G, Tamchek N, Maah MJ (2014) High sensitivity flat SiO fibres for medical dosimetry, Radiation Physics and Chemistry
We describe investigation of a novel undoped flat fibre fabricated for medical radiation dosimetry. Using high energy X-ray beams generated at a potential of 6 MV, comparison has been made of the TL yield of silica flat fibres, TLD-100 chips and Ge-doped silica fibres. The flat fibres provide competitive TL yield to that of TLD-100 chips, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. The dose enhancement factor (DEF) of (0.0150±0.0003) nm Pt is comparable to that obtained using gold, agreeing at the 1% level with the value expected on the basis of photoelectron generation. Finally, X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface oxidation state of the fibre medium. The charge state of Si2p was found to lie on 103.86 eV of binding energy and the atomic percentage obtained from the XPS analysis is 22.41%. © 2014 Elsevier Ltd. All rights reserved.
Khandaker MU, Asaduzzaman K, Nawi SM, Usman AR, Amin YM, Daar E, Bradley DA, Ahmed H, Okhunov AA (2015) Assessment of Radiation and Heavy Metals Risk due to the Dietary Intake of Marine Fishes (Rastrelliger kanagurta) from the Straits of Malacca., PloS one 10 (6)
The environment of the Straits of Malacca receives pollution as a result of various industrial and anthropogenic sources, making systematic studies crucial in determining the prevailing water quality. Present study concerns concentrations of natural radionuclides and heavy metals in marine fish (Rastrelliger kanagurta) collected from the Straits of Malacca, since aquatic stock form an important source of the daily diet of the surrounding populace. Assessment was made of the concentrations of key indicator radionuclides (226Ra, 232Th, 40K) and heavy metals (As, Mn, Fe, Cr, Ni, Zn, Cu, Co, Sr, Al, Hg and Pb) together with various radiation indices linked to the consumption of seafish. The annual effective dose for all detected radionuclides for all study locations has been found to be within UNSCEAR acceptable limits as has the associated life-time cancer risk. The overall contamination of the sampled fish from heavy metals was also found to be within limits of tolerance.
Begum M, Begum M, Mizanur Rahman AKM, Mizanur Rahman AKM, Abdul-Rashid HA, Yusoff Z, Mat-Sharif KA, Zulkifli MI, Muhamad-Yasin SZ, Ung NM, Kadir ABA, Amin YM, Bradley DA (2014) Comparison of thermoluminescence response of different sized Ge-doped flat fibers as a dosimeter, Radiation Physics and Chemistry
© 2015 Elsevier Ltd. Prime dosimetric properties, including dose-response, linearity with dose, energy response, fading and threshold doses were investigated for three different dimension Ge-doped flat fibers. The results of measurement were also compared with two of the more commonly used standard TLD media, TLD-100 (LiF:Mg,Ti-7.5%6LiF) and TLD-700 (7LiF:Mg,Ti-99.9%7LiF) chips. The flat cross-section samples (60×180) ¼m2, (100×350) ¼m2 and (200×750) ¼m2 were fabricated using the Modified Chemical Vapor Deposition (MCVD) process and pulled from the same "preform." In the study, all flat fiber samples provided good linear dose-response for the photon and electron beams generated using a medical linear accelerator (LINAC), for doses in the range 0.5-8Gy. Among the samples, the smallest dimension flat fiber provided the best response, with a sensitivity of some 61% and 54%, respectively of that of the TLD-100 and TLD-700 chips. The energy responses of the samples were studied for various photon (6MV, 10MV) and electron (6MeV, 9MeV) beam energies. TL fading of around 20% was observed over a period of thirty (30) days. These favorable TL characteristics point towards promising development of Ge-doped flat fibers for use in radiotherapy dosimetry.
Noor NM, Hussein M, Bradley DA, Nisbet A (2011) Investigation of the use of Ge-doped optical fibre for in vitro IMRT prostate dosimetry, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 819-823 Elsevier
Bradley DA, Muthuvelu P, Ellis RE, Green EM, AttenburrOW D, Barrett R, Arkill K, Colridge DB, Winlove CP (2007) Characterisation of mineralisation of bone and cartilage: X-ray diffraction and Ca and SrK alpha X-ray fluorescence microscopy, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 263 (1) pp. 1-6 ELSEVIER SCIENCE BV
Akar Tarim U, Ozmutlu EN, Gurler O, Yalcin S, Gundogdu O, Sharaf JM, Bradley DA (2012) Monte Carlo modelling of single and multiple Compton scattering profiles in a concrete material, Radiation Physics and Chemistry
A Monte Carlo simulation study has been conducted of Co photons Compton scattered in concrete, illustrating the degraded energy spectra of gamma-ray radiation. Results are produced representing a NaI(Tl) detector model. We were able to analyse energy distributions of photons that reach the detector system after suffering several successive Compton scatterings in the target. The predicted decrease in intensity of single- and multiple-scattering peaks with increase in thickness of the target medium are in good agreement with experimental observations and findings reported by others. © 2012 Elsevier Ltd. All rights reserved.
Bradley D, Kaabar W, Gundogdu O (2012) Elemental and structural studies at the bone-cartilage interface, AIP Conference Proceedings 1423 pp. 319-326 American Institute of Physics
The techniques ¼Proton-Induced X-and ³-ray Emission, ¼-PIXE and ¼-PIGE, were used to investigate trace and essential element distributions in sections of normal and osteoarthritic (OA) human femoral head. ¼-PIGE yielded 2-D mappings of Na and F while Ca, Z, P and S were mapped by ¼-PIXE. The concentration of chondroitin sulphate supporting functionality in healthy cartilage is significantly reduced in OA samples. Localised Zn points to osteoblastic/osteoclastic activity at the bone-cartilage interface. Small-angle X-ray scattering applied to decalcified OA-affected tissue showed spatial alterations of collagen fibres of decreased axial periodicity compared to normal collagen type I.
Noor NM, Hussein M, Bradley DA, Nisbet A (2010) The potential of Ge-doped optical fibre TL dosimetry for 3D verification of high energy IMRT photon beams, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 157-162 ELSEVIER SCIENCE BV
Daar E, King L, Nisbet A, Thorpe R, Bradley D (2010) Viscosity changes in hyaluronic acid: Irradiation and rheological studies, APPLIED RADIATION AND ISOTOPES 68 (4-5) pp. 746-750 PERGAMON-ELSEVIER SCIENCE LTD
Saripan MI, Mohd Saad WH, Hashim S, Rahman ATA, Wells K, Bradley DA (2013) Analysis of photon scattering trends for material classification using artificial neural network models, IEEE Transactions on Nuclear Science 60 (2) pp. 515-519
In this project, we concentrate on using the Artificial Neural Network (ANN) approach to analyze the photon scattering trend given by specific materials. The aim of this project is to fully utilize the scatter components of an interrogating gamma-ray radiation beam in order to determine the types of material embedded in sand and later to determine the depth of the material. This is useful in a situation in which the operator has no knowledge of potentially hidden materials. In this paper, the materials that we used were stainless steel, wood and stone. These moderately high density materials are chosen because they have strong scattering components, and provide a good starting point to design our ANN model. Data were acquired using the Monte Carlo N-Particle Code, MCNP5. The source was a collimated pencil-beam projection of 1 MeV energy gamma rays and the beam was projected towards a slab of unknown material that was buried in sand. The scattered photons were collected using a planar surface detector located directly above the sample. In order to execute the ANN model, several feature points were extracted from the frequency domain of the collected signals. For material classification work, the best result was obtained for stone with 86.6% accurate classification while the most accurate buried distance is given by stone and wood, with a mean absolute error of 0.05. © 1963-2012 IEEE.
Fadzil MSA, Ramli NNH, Jusoh MA, Kadni T, Bradley DA, Ung NM, Suhairul H, Noor NM (2014) Dosimetric characteristics of fabricated silica fibre for postal radiotherapy dose audits, Journal of Physics: Conference Series 546 (1)
© Published under licence by IOP Publishing Ltd.Present investigation aims to establish the dosimetric characteristics of a novel fabricated flat fibre TLD system for postal radiotherapy dose audits. Various thermoluminescence (TL) properties have been investigated for five sizes of 6 mol% Ge-doped optical fibres. Key dosimetric characteristics including reproducibility, linearity, fading and energy dependence have been established. Irradiations were carried out using a linear accelerator (linac) and a Cobalt-60 machine. For doses from 0.5 Gy up to 10 Gy, Ge-doped flat fibres exhibit linearity between TL yield and dose, reproducible to better than 8% standard deviation (SD) following repeat measurements (n 3). For photons generated at potentials from 1.25 MeV to 10 MV an energy-dependent response is noted, with a coefficient of variation (CV) of less than 40% over the range of energies investigated. For 6.0 mm length flat fibres 100 ¼m thick × 350 pm wide, the TL fading loss following 30 days of storage at room temperature was
Norbani NE, Saat A, Hamzah Z, Wan Idris WMR, Jaafar MZ, Abdul Rahman AT, Abdullah Salim NA, Ramli AT, Bradley DA (2014) Terrestrial gamma radiation dose rates (TGRD) from surface soil in Negeri Sembilan, Malaysia, Radiation Physics and Chemistry
Baseline data on background radiation levels allows for future assessment of possible changes in natural radionuclide concentrations, either as a result of geological processes or radioactive contamination. We have measured terrestrial gamma radiation dose-rates (TGRD) from surface soils throughout accessible areas in the Peninsular Malaysia state of Negeri Sembilan (NS). Dose rate measurements were carried out using a NaI (TI) scintillation survey meter, encompassing 1708 locations, covering about 73% of the 6645 km of the land area in NS. This has allowed development of a TGRD contour map, plotted using WinSurf software. The range of measured TGRD was from 71±3 nGy/h up to 1000±11 nGy/h. The greatest measured TGRD was obtained in an area covered by soil types originating from igneous rock of granitic formations, while the least value of TGRD was observed in an area covered by limestone composed of calcite mineral, mostly found near river and coastal areas. Mean values of TGRD across the seven districts of NS ranged from 244±7 nGy/h to 458±13 nGy/h, the global mean being 330±8 nGy/h compared to a mean value of 92 nGy/h and 59 nGy/h for Malaysia and the world, respectively. The average annual dose from such terrestrial gamma radiation dose-rates to an individual residing in NS, assuming a tropical rural setting, is estimated to be 0.96 mSv per year. © 2014 Elsevier Ltd. All rights reserved.
Al-Sulaiti H, Nasir T, Al Mugren KS, Alkhomashi N, Al-Dahan N, Al-Dosari M, Bradley DA, Bukhari S, Matthews M, Regan PH, Santawamaitre T, Malain D, Habib A (2012) Determination of the natural radioactivity levels in north west of Dukhan, Qatar using high-resolution gamma-ray spectrometry, Applied Radiation and Isotopes 70 (7) pp. 1344-1350
This study is aimed at the determination of the activity concentrations of naturally occuring and technologically enhanced levels of radiation in 34 representative soil samples that have been collected from an inshore oil field area which was found to have, in a previous study, the highest observed value of 226Ra concentration among 129 soil samples. The activity concentrations of 238U and 226Ra have been inferred from gamma-ray transitions associated with their decay progenies and measured using a hyper-pure germanium detector. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented, together with the values of the activity concentrations associated with the naturally occuring radionuclide chains for all the samples collected from NW Dukhan. Discrete-line, gamma-ray energy transitions from spectral lines ranging in energy from ~100keV up to 2.6MeV have been associated with characteristic decays of the various decay products within the 235.8U and 232Th radioactive decay chains. These data have been analyzed, under the assumption of secular equilibrium for the U and Th decay chains. Details of the sample preparation and the gamma-ray spectroscopic analysis techniques are presented. The weighted mean value of the activity concentrations of 226Ra in one of the samples was found to be around a factor of 2 higher than the values obtained in the previous study and approximately a factor of 10 higher than the accepted worldwide average value of 35Bq/kg. The weighted mean values of the activity concentrations of 232Th and 40K were also deduced and found to be within the worldwide average values of 30 and 400Bq/kg, respectively. Our previous study reported a value of 201.9±1.5 Stat.±13 Syst.Bq/kg for 226Ra in one sample and further investigation in the current work determined a measured value for 226Ra of 342.00±1.9 Stat.±25 Syst.Bq/kg in a sample taken from the same locality. This is significantly higher than all the other investigated soil samples in the current and previous works. Notably, the Th levels in the same sample are within the worldwide average expectations, implying that the increased 226Ra concentration arises from TENORM processes. © 2011 Elsevier Ltd.
Hugtenburg RP, Adegunloye AS, Bradley DA (2010) X-ray microbeam radiation therapy calculations, including polarisation effects, with the Monte Carlo code EGS5, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 619 (1-3) pp. 221-224
Bradley DA, Hugtenburg RP, Yusoff AL (2006) At-edge minima in elastic photon scattering amplitudes for dilute aqueous ions, RADIATION PHYSICS AND CHEMISTRY 75 (11) pp. 1676-1682 PERGAMON-ELSEVIER SCIENCE LTD
Alawiah A, Bauk S, Marashdeh MW, Ng KS, Abdul-Rashid HA, Yusoff Z, Gieszczyk W, Noramaliza MN, Mahdiraji GA, Tamchek N, Muhd-Yassin SZ, Mat-Sharif KA, Zulkifli MI, Maah MJ, Che Omar SS, Bradley DA (2015) Thermoluminescence glow curves and deconvoluted glow peaks of Ge doped flat fibers at ultra-high doses of electron radiation, Radiation Physics and Chemistry 113 pp. 53-58
© 2015 Elsevier Ltd.The behavior of Ge doped silica, SiO2 flat fibers (FF) irradiated with 2.5MeV electron radiation at ultra-high dose (UHD) range, up to 1MGy, has been investigated. The analyzed glow curves measured by the usage of the WinREMS software revealed that peak height and glow curve maximum temperature are highly dependent on the dose. The shape of the glow curves is constant with increasing dose. The supralinearity of all glow peaks increases to its f(D)max, which occurs around 50kGy. No saturation occurs at f(D)max and further increases in dose, up to 1MGy, exhibits a significant decrease in f(D). The glow peaks 2 (230°C) and 4 (290°C), deconvoluted by the usage of WinGCF software, are the first-order kinetic peaks and can be used as the main dosimetric peaks for high-dose measurements between 1 and 50kGy in an industrial environment.
Bradley D, Hoggard N (2013) Happy New Year from BJR!, Br J Radiol 87 (1033)
Müller B, Deyhle H, Bradley DA, Farquharson M, Schulz G, Müller-Gerbl M, Bunk O (2010) Scanning X-ray scattering: Evaluating the nanostructure of human tissues, European Journal of Nanomedicine 3 (1) pp. 30-33
Dunn WL, Solomon CJ, Loschke KW, Bradley DA, Gilboy WB (2007) Ionizing photon methods for standoff bomb detection, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 580 (1) pp. 778-781 ELSEVIER SCIENCE BV
Alawiah A, Alina MS, Bauk S, Abdul-Rashid HA, Gieszczyk W, Noramaliza MN, Mahdiraji GA, Tamchek N, Zulkifli MI, Bradley DA, Marashdeh MW (2015) The thermoluminescence characteristics and the glow curves of Thulium doped silica fiber exposed to 10MV photon and 21MeV electron radiation., Appl Radiat Isot 98 pp. 80-86
The thermoluminescence (TL) glow curves and kinetics parameters of Thulium (Tm) doped silica cylindrical fibers (CF) are presented. A linear accelerator (LINAC) was used to deliver high-energy radiation of 21MeV electrons and 10MV photons. The CFs were irradiated in the dose range of 0.2-10Gy. The experimental glow curve data was reconstructed by using WinREMS. The WinGCF software was used for the kinetic parameters evaluation. The TL sensitivity of Tm-doped silica CF is about 2 times higher as compared to pure silica CF. Tm-doped silica CF seems to be more sensitive to 21MeV electrons than to 10MV photons. Surprisingly, no supralinearity was displayed and a sub-linear response of Tm-doped silica CF was observed within the analyzed dose range for both 21MeV electrons and 10MV photons. The Tm-doped silica CF glow curve consists of 5 individual glow peaks. The Ea of peak 4 and peak 5 was highly dependent on dose when irradiated with photons. We also noticed that the electron radiation (21MeV) caused a shift of glow peak by 7-13°C to the higher temperature region compared with photons radiation (10MV). Our Tm-doped fibers seem to give high TL response after 21MeV electrons, which gives around 2 times higher peak integral as compared with 10MV photon radiation. We concluded that peak 4 is the first-order kinetic peak and can be used as the main dosimetric peak of Tm-doped silica CF.
Bradley DA, Wells K (2013) Biomedical applications reviewed: Hot topic areas, Radiation Physics and Chemistry
Making reference to the British Journal of Radiology and competitor journal titles, we look at the general area of biomedical physics, reviewing some of the associated topics in ionising radiation research attracting interest over the past 2 years. We also reflect on early developments that have paved the way for these endeavours. The talk is illustrated by referring to a number of biomedical physics areas in which this group has been directly involved, including novel imaging techniques that address compositional and structural makeup as well as use of elastically scattered X-ray phase contrast, radiation damage linking to possible pericardial effects in radiotherapy, simulation of microvascularity and oxygenation with a focus of radiation resistant hypoxic tumours, issues of high spatial resolution dosimetry and tissue interface radiotherapy with doses enhanced through use of high atomic number photoelectron conversion media. © 2012 Elsevier Ltd. All rights reserved.
Nawi SNBM, Wahib NFB, Zulkepely NNB, Amin YBM, Min UN, Bradley DA, Nor RBM, Maah MJ (2015) The Thermoluminescence Response of Ge-Doped Flat Fibers to Gamma Radiation, SENSORS 15 (8) pp. 20557-20569 MDPI AG
Garrity DJ, De Rosa AJ, Bradley DA, Jarman SE, Jenneson PM, Vincent SM (2010) Development of a prototype pipework scanning system based upon energy dispersive X-ray diffraction (EDXRD), NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 287-290 ELSEVIER SCIENCE BV
Yaakob NH, Wagiran H, Imam Hossain M, Ramli AT, Bradley DA, Ali H, Imam Hossain M (2011) Low-dose photon irradiation response of Ge and Al-doped SiO
optical fibres,
Applied Radiation and Isotopes
We have investigated the thermoluminescent response and fading characteristics of germanium- and aluminium-doped SiO
optical fibres. These optical fibres were placed in a solid phantom and irradiated using 6 and 10 MV photon beams at doses ranging from 0.02 to 0.24 Gy delivered using a linear accelerator. In fading studies, the TL measurements were continued up to 14 days post-irradation. We have investigated the linearity of TL response as a function of dose for Ge-, Al-doped optical fibre and TLD-100 obtained for 6 and 10 MV photon irradiations. We have concentrated on doses that represent a small fraction of that delivered to the tumour to establish sensitivity of measurement for peripheral exposures in external beam radiotherapy. © 2011 Elsevier Ltd.
Muthuvelu P, Ellis RE, Green EM, Attenburrow D, Barrett R, Arkill K, Colridge DB, Winlove CP, Bradley DA (2007) Microvascularity, blood flow and tissue structure at the subchondral plate using an X-ray fluorescence technique, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 271 (3) pp. 771-775 SPRINGER
Palmer AL, Bradley DA, Nisbet A (2014) Dosimetric audit in brachytherapy., Br J Radiol 87 (1041)
Dosimetric audit is required for the improvement of patient safety in radiotherapy and to aid optimization of treatment. The reassurance that treatment is being delivered in line with accepted standards, that delivered doses are as prescribed and that quality improvement is enabled is as essential for brachytherapy as it is for the more commonly audited external beam radiotherapy. Dose measurement in brachytherapy is challenging owing to steep dose gradients and small scales, especially in the context of an audit. Several different approaches have been taken for audit measurement to date: thimble and well-type ionization chambers, thermoluminescent detectors, optically stimulated luminescence detectors, radiochromic film and alanine. In this work, we review all of the dosimetric brachytherapy audits that have been conducted in recent years, look at current audits in progress and propose required directions for brachytherapy dosimetric audit in the future. The concern over accurate source strength measurement may be essentially resolved with modern equipment and calibration methods, but brachytherapy is a rapidly developing field and dosimetric audit must keep pace.
Yaakob NH, Wagiran H, Imam Hossain M, Ramli AT, Bradley DA, Ali H (2011) Low-dose photon irradiation response of Ge and Al-doped SiO2 optical fibres, Applied Radiation and Isotopes 69 (9) pp. 1189-1192 Elsevier
Ghomeishi M, Mahdiraji GA, Adikan FRM, Ung NM, Bradley DA (2015) Sensitive Fibre-Based Thermoluminescence Detectors for High Resolution In-Vivo Dosimetry, SCIENTIFIC REPORTS 5 ARTN 13309 NATURE PUBLISHING GROUP
Abdelkader MH, Alkhateeb SM, Bradley DA, Pani S (2012) Development and characterization of a laboratory based X-ray diffraction imaging system for material and tissue characterization., Appl Radiat Isot 70 (7) pp. 1325-1330 Elsevier
Soft tissues feature a degree of short-range order, giving rise to diffraction patterns with broader peaks than crystalline materials. For this reason, an X-ray diffraction system (XRD) for characterization of soft tissue has less stringent requirements in terms of momentum transfer resolution than the one aimed at characterizing crystalline materials. We present results on the characterization of two energy-dispersive XRD systems. The first was based on conical collimation at 5.9° and the second was based on linear collimation at varying angles between 2° and 10°. The systems include a CdTe detector and a W-anode X-ray source. The angular resolution was measured as a function of sample thickness and scattering angle. Preliminary results confirm the effectiveness of the method for the characterization of biological tissues, showing insensitivity to small changes in angular acceptance and sample thickness, also showing it is possible to combine scattering data obtained at different angles.
Amin YM, Mahat RH, Nor RM, Khandaker MU, Takleef GH, Bradley DA (2013) The presence of natural radioactivity and 137Cs in the South China Sea bordering peninsular Malaysia., Radiat Prot Dosimetry 156 (4) pp. 475-480
The presence of natural radioactivity and (137)Cs has been investigated in fresh media obtained from South China Sea locations off the coast of peninsular Malaysia. The media include seafood, sea water and sediment. The samples were collected some weeks prior to the devastating 2011 TMhoku earthquake and associated tsunami, the occurrence of which precipitated the Fukushima incident. All samples showed the presence of naturally occurring (226)Ra, (228)Ra and primordial (40)K, all at typically prevailing levels. The concentrations of natural radioactivity in molluscs were found to be greater than that of other marine life studied herein, the total activity ranging from 337 to 393 Bq kg(-1) dry weight. The total activity in sea water ranged from 15 to 88 Bq l(-1). Sediment samples obtained at deep sea locations more than 20 km offshore further revealed the presence of (137)Cs. The activity of (137)Cs varied from ND to 0.5 Bq kg(-1) dry weight, the activity increasing with offshore distance and depth. The activity concentrations presented herein should be considered useful in assessing the impact of any future radiological contamination to the marine environment.
Yaakob NH, Wagiran H, Imam Hossain M, Ramli AT, Bradley DA, Ali H (2011) Low-dose photon irradiation response of Ge and Al-doped SiO2 optical fibres, Applied Radiation and Isotopes
Zulkepely NN, Amin YM, Nor RM, Bradley DA, Maah MJ, Nawi SNM, Wahib NF (2015) Preliminary results on the photo-transferred thermoluminescence from Ge-doped SiO2 optical fiber, RADIATION PHYSICS AND CHEMISTRY 117 pp. 108-111 PERGAMON-ELSEVIER SCIENCE LTD
Rahman ATA, Bradley DA, Doran SJ, Thierry B, Braeuer-Krisch E, Bravin A (2010) The thermoluminescence response of Ge-doped silica fibres for synchrotron microbeam radiation therapy dosimetry, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 167-170 ELSEVIER SCIENCE BV
Ismail EC, Kaabar W, Garrity D, Gundogdu O, Bunk O, Pfeiffer F, Farquharson MJ, Bradley DA (2010) X-ray phase contrast imaging of the bone-cartilage interface, APPLIED RADIATION AND ISOTOPES 68 (4-5) pp. 767-771 PERGAMON-ELSEVIER SCIENCE LTD
Hashim S, Ibrahim SA, Che Omar SS, Alajerami YS, Saripan MI, Noor NM, Ung NM, Mahdiraji GA, Bradley DA, Alzimami K (2014) Photon irradiation response of photonic crystal fibres and flat fibres at radiation therapy doses., Appl Radiat Isot 90 pp. 258-260
Radiation effects of photon irradiation in pure Photonic Crystal Fibres (PCF) and Flat fibres (FF) are still much less investigated in thermoluminescense dosimetry (TLD). We have reported the TL response of PCF and FF subjected to 6 MV photon irradiation. The proposed dosimeter shows good linearity at doses ranging from 1 to 4 Gy. The small size of these detectors points to its use as a dosimeter at megavoltage energies, where better tissue-equivalence and the Bragg-Gray cavity theory prevails.
Yaakob NH, Wagiran H, Hossain I, Ramli AT, Bradley DA, Hashim S, Ali H (2011) Electron irradiation response on Ge and Al-doped SiO2 optical fibres, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 637 (1) pp. 185-189
Noor NM, Hussein M, Kadni T, Bradley DA, Nisbet A (2014) Characterization of Ge-doped optical fibres for MV radiotherapy dosimetry, Radiation Physics and Chemistry 98 pp. 33-41
Ge-doped optical fibres offer promising thermoluminescence (TL) properties together with small physical size and modest cost. Their use as dosimeters for postal radiotherapy dose audits of megavoltage photon beams has been investigated. Key dosimetric characteristics including reproducibility, linearity, dose rate, temperature and angular dependence have been established. A methodology of measuring absorbed dose under reference conditions was developed. The Ge-doped optical fibres offer linearity between TL yield and dose, with a reproducibility of better than 5%, following repeated measurements (n=5) for doses from 5cGy to 1000cGy. The fibres also offer dose rate, angular and temperature independence, while an energy-dependent response of 7% was found over the energy range 6MV to 15MV (TPR20,10 of 0.660, 0.723 and 0.774 for 6, 10 and 15MV respectively). The audit methodology has been developed with an expanded uncertainty of 4.22% at 95% confidence interval for the photon beams studied. © 2013 Elsevier Ltd.
Issa F, Latip NAA, Bradley DA, Nisbet A (2010) Ge-doped optical fibres as thermoluminescence dosimeters for kilovoltage X-ray therapy irradiations, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 834-837 Elsevier
Jafari SM, Bradley DA, Gouldstone CA, Sharpe PHG, Alalawi A, Jordan TJ, Clark CH, Nisbet A, Spyrou NM (2014) Low-cost commercial glass beads as dosimeters in radiotherapy, Radiation Physics and Chemistry 97 pp. 95-101
Recent developments in advanced radiotherapy techniques using small field photon beams, require small detectors to determine the delivered dose in steep dose gradient fields. Commercially available glass jewellery beads exhibit thermoluminescent properties and have the potential to be used as dosimeters in radiotherapy due to their small size (
Hugtenburg RP, Saeedi F, Bradley DA (2007) Modeling dose response to synchrotron X-rays in solid-state and biological systems, RADIATION EFFECTS AND DEFECTS IN SOLIDS 162 (10-12) pp. 765-769 TAYLOR & FRANCIS LTD
Zahaimi NA, Ooi Abdullah MHR, Zin H, Abdul Rahman AL, Hashim S, Saripan MI, Paul MC, Bradley DA, Abdul Rahman AT (2014) Dopant concentration and thermoluminescence (TL) properties of tailor-made Ge-doped SiO2 fibres, Radiation Physics and Chemistry 104 pp. 297-301
Study focuses on characterisation of diverse concentrations of Ge-doped SiO2 fibre as a potential thermoluminescence (TL) system for radiotherapy dosimetry. Irradiations were made using a linear accelerator providing 6MV and 10MV photon beams. Investigation has been done on various doped core diameter Ge-doped SiO2 glass fibres such as commercial telecommunication fibres of 8¼m and 9¼m (CorActive High Tech, Canada), tailor-made fibres of 23 and 50¼m produced by the Central Glass and Ceramic Research Institute Kolkata, and tailor-made fibres of 11¼m produced by the University of Malaya Photonics Research Centre. The fibres have been characterised for TL sensitivity, reproducibility, dose- and energy-dependence. The area under the TL glow curve increases with increasing core diameter. For repeat irradiations at a fixed dose the dosimeter produces a flat response better than 4% (1SD) of the mean of the TL distribution. Minimal TL signal fading was found, less than 0.5% per day post irradiation. Linearity of TL has been observed with a correlation coefficient (r2) of better than 0.980 (at 95% confidence level). For particular dopant concentrations, the least square fits show the change in TL yield, in counts per second per unit mass, obtained from 50¼m core diameter fibres irradiated at 6MV of photon to be 8 times greater than that of 8¼m core diameter fibre. With respect to energy response, the TL yield at 10MV decreases by~5% compared to that at 6MV, primarily due to the lower mass energy absorption coefficient at higher photon energy. These early results indicate that selectively screened fibres can be developed into a promising TL system, offering high spatial resolution capability and, with this, verification of complex radiotherapy dose distributions. © 2014 Elsevier Ltd.
Daar E, Kaabar W, Lei C, Keddie JL, Nisbet A, Bradley DA (2010) AFM and uni-axial testing of pericardium exposed to radiotherapy doses, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 874-877 Elsevier
Khandaker MU, Wahib NB, Amin YM, Bradley DA (2013) Committed effective dose from naturally occuring radionuclides in shellfish, Radiation Physics and Chemistry 88 pp. 1-6
Recognizing their importance in the average Malaysian daily diet, the radioactivity concentrations in mollusc- and crustacean-based food have been determined for key naturally occuring radionuclides. Fresh samples collected from various maritime locations around peninsular Malaysia have been processed using standard procedures; the radionuclide concentrations being determined using an HPGe ³-ray spectrometer. For molluscs, assuming secular equilibrium, the range of activities of 238U (226Ra), 232Th (228Ra) and 40K were found to be 3.28±0.35 to 5.34±0.52, 1.20±0.21 to 2.44±0.21 and 118±6 to 281±14Bqkg-1 dry weight, respectively. The respective values for crustaceans were 3.02±0.57 to 4.70±0.52, 1.38±0.21 to 2.40±0.35 and 216±11 to 316±15Bqkg-1. The estimated average daily intake of radioactivity from consumption of molluscs are 0.37Bqkg-1 for 238U (226Ra), 0.16Bqkg-1 for 232Th (228Ra) and 18Bqkg-1 for 40K; the respective daily intake values from crustaceans are 0.36Bqkg-1, 0.16Bqkg-1 and 23Bqkg-1. Associated annual committed effective doses from molluscs are estimated to be in the range 21.3 to 34.7¼Sv for 226Ra, 19.3 to 39.1¼Sv for 228Ra and 17.0 to 40.4¼Sv for 40K. For crustaceans, the respective dose ranges are 19.6 to 30.5¼Sv, 22.0 to 38.4¼Sv and 31.1 to 45.5¼Sv, being some several times world average values. © 2013 Elsevier Ltd.
Bradley DA, Farquharson MJ, Gundogdu O, Al-Ebraheem A, Ismail EC, Kaabar W, Bunk O, Pfeiffer F, Falkenberge G, Bailey M (2010) Applications of condensed matter understanding to medical tissues and disease progression: Elemental analysis and structural integrity of tissue scaffolds, RADIATION PHYSICS AND CHEMISTRY 79 (2) pp. 162-175 PERGAMON-ELSEVIER SCIENCE LTD
Loveland J, Gundogdu O, Morton E, Wells K, Bradley DA (2010) Phase contrast imaging: Effect of increased object-detector distances at X-ray diagnostic and megavoltage energies, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 625-629 Elsevier
Yip M, Saripan MI, Wells K, Bradley DA (2015) Monte Carlo Simulations for the Detection of Buried Objects Using Single Sided Backscattered Radiation, PLOS ONE 10 (9) ARTN e0135769 PUBLIC LIBRARY SCIENCE
Begum M, Rahman A, Abdul-Rashid H, Abdullah W, Noor N, Zulkifli M, Muhamad-Yasin S, Mat-Sharif K, Tamchek N, Nawi S, Wahib N, Amin Y, Bradley D (2013) Thermoluminescence Response of Ge-doped Optical Fiber Dosimeters with Different Core Sizes, 2013 IEEE 4TH INTERNATIONAL CONFERENCE ON PHOTONICS (ICP) pp. 290-292 IEEE
Kaabar W, Gundogdu O, Laklouk A, Bunk O, Pfeiffer F, Farquharson MJ, Bradley DA (2010) mu-PIXE and SAXS studies at the bone-cartilage interface, APPLIED RADIATION AND ISOTOPES 68 (4-5) pp. 730-734 PERGAMON-ELSEVIER SCIENCE LTD
Ramli NNH, Salleh H, Mahdiraji GA, Zulkifli MI, Hashim S, Bradley DA, Bradley DA, M Noor N (2014) Characterization of amorphous thermoluminescence dosimeters for patient dose measurement in X-ray diagnostic procedures, Radiation Physics and Chemistry
© 2015. We investigate the use of novel Ge-doped amorphous silica flat fibers as thermoluminescence dosimeters (TLDs) in verifying patient entrance surface-dose (ESD) in diagnostic examinations. Selected fibers with established dosimetric characteristics (including energy dependence, linearity, reproducibility, and fading) were loaded into plastic capsules in groups of six. The fibers have been calibrated against a parallel plate ionization chamber, use being made of x-rays generated at 70. kVp, accessing a Secondary Standards Dosimetry Laboratory (SSDL) facility. The fiber characterization measurements were made using a Toshiba X-ray machine operating within the nominal energies range 40. kVp to 150. kVp, for doses in the range 0.02. mGy up to 3. mGy. For doses from 2. mGy up to 150. mGy, the flat fibers exhibit linearity between TL yield and dose, reproducible to better than 3% standard deviation following repeat measurements (n=3). A marked energy-dependent response is observed for photons generated at potentials from 40. kVp to 150. kVp. From present results, it is concluded that Ge-doped fibers represent a viable system for use in diagnostic dosimetry, corrections being made for the various factors influencing TL yield.
Moger CJ, Barrett R, Bleuet P, Bradley DA, Ellis RE, Green EM, Knapp KM, Muthuvelu P, Winlove CP (2007) Regional variations of collagen orientation in normal and diseased articular cartilage and subchondral bone determined using small angle X-ray scattering (SAXS)., Osteoarthritis Cartilage 15 (6) pp. 682-687
OBJECTIVE: To determine regional differences in the orientation of collagen in the articular cartilage of the equine metacarpophalangeal joint as well as describing cartilage orientation in lesions using small angle X-ray scattering (SAXS). DESIGN: SAXS diffraction patterns were taken at the European Synchrotron Radiation Facility (ESRF), with increasing depth into cartilage and bone cross sections. Results for healthy samples were taken at different regions along the joint which receive different loads and differences in collagen orientation were determined. Results were also taken from diseased samples and the collagen orientation changes from that of healthy samples observed. RESULTS: Regions subject to low loads show a lower degree of orientation and regions exposed to the highest loads possess oriented collagen fibres especially in the radial layer. In early lesions the orientations of the collagen fibres are disrupted. Subchondral bone fibres are twisted in regions where the joint receives shear forces. Changes in fibre orientation are also observed in the calcified cartilage even in regions where the cartilage is intact. In more advanced lesions where there is loss of cartilage the fibres in the calcified layer are realigned tangential to the surface. CONCLUSIONS: Regional variations in collagen arrangement show that the highly ordered layers of the articular cartilage are the most important elements in supporting high variable loads. In lesions changes occur in the deep tissue whilst the overlying cartilage appeared normal. We therefore suggest that the interface region is a key element in the early stages of the disease.
Bradley DA, Hashim S, Saripan MI, Wells K, Dunn WL (2011) Photon signature analysis using template matching, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 466-469
We describe an approach to detect improvised explosive devices (IEDs) by using a template matching procedure. This approach relies on the signature due to backstreaming ³ photons from various targets. In this work we have simulated cylindrical targets of aluminum, iron, copper, water and ammonium nitrate (nitrogen-rich fertilizer). We simulate 3.5 MeV source photons distributed on a plane inside a shielded area using Monte Carlo N-Particle (MCNPTM) code version 5 (V5). The 3.5 MeV source gamma rays yield 511 keV peaks due to pair production and scattered gamma rays. In this work, we simulate capture of those photons that backstream, after impinging on the target element, toward a NaI detector. The captured backstreamed photons are expected to produce a unique spectrum that will become part of a simple signal processing recognition system based on the template matching method. Different elements were simulated using different sets of random numbers in the Monte Carlo simulation. To date, the sum of absolute differences (SAD) method has been used to match the template. In the examples investigated, template matching was found to detect all elements correctly. © 2011 Elsevier B.V.
Mahdiraji GA, Dermosesian E, Safari MJ, Adikan FRM, Bradley DA (2015) Collapsed-Hole Ge-Doped Photonic Crystal Fiber as a Diagnostic Radiation Dosimeter, JOURNAL OF LIGHTWAVE TECHNOLOGY 33 (16) pp. 3439-3445 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Bradley DA, Hashim S, Saripan MI, Wells K, Dunn WL (2011) Photon signature analysis using template matching, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 466-469 Elsevier
Alzimami KS, Maghraby AM, Bradley DA (2014) Comparative study of some new EPR dosimeters, Radiation Physics and Chemistry 95 pp. 109-112
Investigations have been made of four new radiation dosimetry EPR candidates from the same family of materials: sulfamic acid, sulfanillic acid, homotaurine, and taurine. Mass energy attenuation coefficients, mass stopping power values and the time dependence of the radiation induced radicals are compared. Also investigated are the microwave saturation behavior and the effect of applied modulation amplitude on both peak-to-peak line width (WPP) and peak-to-peak signal height (HPP). The dosimeters are characterized by simple spectra and stable radiation-induced radicals over reasonable durations, especially in taurine dosimeters. Sulfamic acid dosimeters possessed the highest sensitivity followed by taurine and homotaurine and sulfanillic. © 2013 Elsevier Ltd.
Alkhateeb SM, Abdelkader MH, Bradley DA, Pani S (2012) Breast tissue contrast-simulating materials using energy-dispersive X-ray diffraction, Applied Radiation and Isotopes 70 (7) pp. 1446-1450
Breast lesions and normal tissues have different molecular arrangements that affect their diffraction patterns. Different mouldable and non-mouldable materials were analysed using an energy dispersive X-ray diffraction system based on a conventional X-ray source (operated at 70kVp) and a CdTe detector (Amptek XT-100), including a conventional spectroscopic chain. Combinations of materials were identified to have a contrast comparable to that achieved in diffraction imaging for different breast tissues at the momentum transfer values carrying the greatest amount of information (1.1nm -1 and 1.6nm -1). © 2012 Elsevier Ltd.
Hashim S, Bradley DA, Peng N, Ramli AT, Wagiran H (2010) The thermoluminescence response of oxygen-doped optical fibres subjected to photon and electron irradiations, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 619 (1-3) pp. 291-294 ELSEVIER SCIENCE BV
Siti Shafiqah AS, Amin YM, Md Nor R, Tamchek N, Bradley DA (2015) Enhanced TL response due to radiation induced defects in Ge-doped silica preforms, Radiation Physics and Chemistry 111 pp. 87-90
© 2015 Elsevier Ltd.Study has been made of the thermoluminescence (TL) response of Ge-doped silica preforms fabricated using the MCVD process and subsequently subjected to ³-ray irradiation. Two types of preform were fabricated, obtained using a different flow rate and deposition temperature for each case. Results from the absorption spectra of the samples show a signature absorption peak at 5.1. eV and 6.8. eV, indicative of oxygen-deficient and oxygen-rich defects respectively. The TL efficiency for both Ge samples were compared with the standard phosphor-based (LiF) thermoluminescence dosimeter, TLD100. For both sample types, a linear response has been obtained over the dose range 1-10. Gy. Analysis further showed the oxygen deficient Ge-doped silica sample provides a very much greater TL yield than TLD100, at 890. nC/Gy compared to 220. nC/Gy. Conversely, the oxygen rich sample gave a more limited response, with a sensitivity of 75. nC/Gy.
Alajerami YSM, Hashim S, Ghoshal SK, Saleh MA, Ibrahim Z, Kadni T, Saripan MI, Alzimami K, Bradley DA (2013) The Effect of TiO and MgO on the Thermoluminescence Properties of a Lithium Potassium Borate Glass System, Journal of Physics and Chemistry of Solids
The influence of dopant TiO and co-dopant MgO on the thermoluminescence (TL) properties of lithium potassium borate glass (LKB) is reported in this paper. The glow curve exhibits a prominent peak (T) at 230 °C. The TL intensity was enhanced by a factor of ~3 due to the incorporation of MgO, and this was attributed to the creation of extra electron traps mediated by radiative recombination energy transfer. We achieved good linearity of the TL yield with dose, low fading, excellent reproducibility and a promising effective atomic number (Z =8.89), all of which are highly suitable for dosimetry. The effect of heating rate, sunlight and dose rate on the TL are also examined. These attractive features demonstrate that our dosimeter is useful in medical radiation therapy. © 2013 Elsevier Ltd. All rights reserved.
Wells K, Bradley DA (2012) A review of X-ray explosives detection techniques for checked baggage, Applied Radiation and Isotopes 70 (8) pp. 1729-1746
In recent times, the security focus for civil aviation has shifted from hijacking in the 1980s, towards deliberate sabotage. X-ray imaging provides a major tool in checked baggage inspection, with various sensitive techniques being brought to bear in determining the form, and density of items within luggage as well as other material dependent parameters. This review first examines the various challenges to X-ray technology in securing a safe system of passenger transportation. An overview is then presented of the various conventional and less conventional approaches that are available to the airline industry, leading to developments in state-of-the-art imaging technology supported by enhanced machine and observer-based decision making principles. © 2012 Elsevier Ltd.
Zahaimi NA, Zin H, Mahdiraji GA, Rahman ALA, Bradley DA, Rahman ATA (2014) Characterisation of the thermoluminescence (TL) properties of tailor-made Ge-doped silica glass fibre for applications in medical radiation therapy dosimetry, Journal of Physics: Conference Series 546 (1)
© Published under licence by IOP Publishing Ltd.We have investigated the characterisation of new fabricated material Ge doped silica glass thermoluminescence TL dosimeter (Photonic Research Centre, University of Malaya) for medical radiation dosimetry at therapy energy. Previously, the dosimeter has been studied to provide ideal dosimetry system, suitable to ensure an accurate delivery of radiation doses to tumour tissue while minimising the amount of radiation administrated to healthy tissue. Both energies of photon and electron were used in this experiment for a dose range of 1 to 5 Gy. The various sizes of core diameter Ge doped silica glass (120, 241, 362, 483 and 604 ¼m) were exposed by using linear accelerator at Pantai Medical Centre. For both energies, the optical fibres were found to produce a flat response to a fixed photon and electron doses to within 4% (S.D) of the mean of the TL distribution. In terms of dose response, the fibres provide linear response over the range investigated, from a fraction of 1-5 Gy. The finding shows 120 ¼m fibres have 1.82 greater dose response than 604 pm fibres irradiated at 6 MV photon with a fixed dose of 3 Gy. While for electron energy 12 MeV, the response shows 120 ¼m fibres have 1.58 greater dose response compared to 604 ¼m fibres. The good responses are suitable to make these tailor-made doped silica fibres a promising TL material for use as a dosimetric system in medical radiation therapy.
Hashim S, Alajerami YSM, Ghoshal SK, Saleh MA, Saripan MI, Kadir ABA, Bradley DA, Alzimami K (2014) Dosimetric characteristics of LKB:Cu,P solid TL detector, Radiation Physics and Chemistry
The dosimetric characteristics of newly developed borate glass dosimeter modified with lithium and potassium carbonate (LKB) and co-doped with CuO and NHHPO are reported. Broad peaks in the absence of any sharp peak confirms the amorphous nature of the prepared glass. A simple glow curve of Cu doped sample is observed with a single prominent peak (T) at 220 °C. The TL intensity response shows an enhancement of ~100 times due to the addition of CuO (0.1 mol%) to LKB compound. A further enhancement of the intensity by a factor of 3 from the addition of 0.25 mol% NHHPO as a co-dopant impurity is attributed to the creation of extra electron traps with consequent increase in energy transfer of radiation recombination centers. The TL yield performance of LKB:Cu,P with Z H8.92 is approximately seventeen times less sensitive compared to LiF:Mg,Ti (TLD-100). The proposed dosimeter shows good linearity up to 10 Gy, minimal fading and photon energy independence. These attractive features offered by our dosimeter is expected to pave the way towards dosimetric applications. © 2013 Elsevier Ltd. All rights reserved.
Bradley DA, Abdul Sani SF, Alalawi AI, Jafari SM, Nisbet A, Noor NM, Hairul Azhar AR, Mahdiraji GA, Tamchek N, Ghosh S, Paul MC, Alzimami KS, Maah MJ (2014) Development of tailor-made silica fibres for TL dosimetry, Radiation Physics and Chemistry
The Ge dopant in commercially available silica optical fibres gives rise to appreciable thermoluminscence (TL), weight-for-weight offering sensitivity to MV X-rays several times that of the LiF dosimeter TLD100. The response of these fibres to UV radiation, X-rays, electrons, protons, neutrons and alpha particles, with doses from a fraction of 1 Gy up to 10 kGy, have stimulated further investigation of the magnitude of the TL signal for intrinsic and doped SiO fibres. We represent a consortium effort between Malaysian partners and the University of Surrey, aimed at production of silica fibres with specific TL dosimetry applications, utilizing modified chemical vapour deposition (MCVD) doped silica-glass production and fibre-pulling facilities. The work is informed by defect and dopant concentration and various production dependences including pulling parameters such as temperature, speed and tension; the fibres also provide for spatial resolutions down to
Akar Tarim U, Gurler O, Ozmutlu EN, Yalcin S, Gundogdu O, Sharaf JM, Bradley DA (2012) The energy spectrum of 662keV photons in a water equivalent phantom, Radiation Physics and Chemistry 81 (7) pp. 745-748
Investigation is made on the energy spectrum of photons originating from interactions of 662. keV primary gamma-ray photons emitted by a point source positioned at the centre of a water equivalent solid phantom of dimensions 19. cm×19. cm×24. cm. Peaks resulting from total energy loss (photopeak) and multiple and back scattering have been observed using a 51. mm×51. mm NaI(Tl) detector; good agreement being found between the measured and simulated response functions. The energy spectrum of the gamma photons obtained through the Monte Carlo simulation reveals local maxima at about 100. keV and 210. keV, being also observed in the experimental response function. Such spectra can be used as a method of testing the water equivalence of solid phantom media before their use for dosimetry measurements. © 2012 Elsevier Ltd.
Noor NM, Shukor NA, Hussein M, Nisbet A, Bradley DA (2012) Comparison of the TL fading characteristics of Ge-doped optical fibres and LiF dosimeters, Appl Radiat Isot 70 (7) pp. 1384-1387 Elsevier
Fading is important in choosing appropriate thermoluminescence (TL) materials for particular applications. Comparison is made herein of changes due to fading in the TL yield of Ge-doped fibres and lithium fluoride (LiF) dosimeters, for varying temperature and dose. The fading is independent of dose for all investigated dosimeters while the loss in TL yield reduces for lower storage temperatures. At room temperature and for 133 days of storage, a maximum signal loss of 5% has been observed for both forms of LiF dosimeter, while 9 and 50¼m core diameter Ge-doped fibres produced a loss of 11% and 8%, respectively.
Wahib N, Zulkepely NN, Nawi SNM, Amin YM, Ling YS, Sani SFA, Maah MJ, Bradley DA (2015) Gamma irradiated thermoluminescence response of Ge-doped SiO2 fibre, APPLIED RADIATION AND ISOTOPES 105 pp. 158-162 PERGAMON-ELSEVIER SCIENCE LTD
Jafari SM, Jordan TJ, Hussein M, Bradley DA, Clark CH, Nisbet A, Spyrou NM (2014) Energy response of glass bead TLDs irradiated with radiation therapy beams, Radiation Physics and Chemistry 104 pp. 208-211
Glass beads are a novel TL dosimeter in radiotherapy. An important characteristic of TL dosimeters is their energy response, especially when intended for use in radiotherapy applications over a wide range of energies (typically from X-rays generated at 80kVp up to 25MV photon and MeV electron beams). In this paper, the energy response of glass beads (Mill Hill, Japan) is investigated for their TL response to kV X-rays from an orthovoltage radiotherapy unit and also for MV photon and MeV electron beams from a medical linear accelerator. The experimental findings show that for photon and electron beams, the TL response of this particular glass bead, normalised to unity for 6MV X-rays (TPR20/10=0.670), decreases to 0.96±0.02 for 15MV X-rays (TPR20/10=0.761) and to 0.95±0.01 for 20MeV electron beams (R50,D=8.35cm). This compares favourably with other TLD materials such as LiF and also alanine dosimeters that are readout with an EPR system. For kV X-rays, the response increases to 4.52±0.05 for 80kV X-rays (HVL=2.4mm Al) which approaches 3 times that of LiF TLDs and 5 times that of alanine. In conclusion, the particular glass beads, when used as a dosimeter material, show a relatively small energy dependence over the megavoltage range of clinically relevant radiation qualities, being clearly advantageous for accurate dosimetry. Conversely, the energy response is significant for photon beam energies covering the kV range. In both circumstances, in dosimetric evaluations the energy response needs to be taken into account. © 2014 Elsevier Ltd.
Gundogdu O, Ismail EC, Jenneson RM, Bradley DA (2009) Making Clear the Imperceptible: In-Line X-ray Phase Contrast Imaging, ADVANCED SCIENCE LETTERS 2 (1) pp. 78-80 AMER SCIENTIFIC PUBLISHERS
Mohamed F, Bradley D, Winlove C (2007) Effects of ionizing radiation on extracellular matrix, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 580 (1) pp. 566-569 ELSEVIER SCIENCE BV
Alkhorayef MA, Alkhorayef MA, Alnaaimi MA, Alduaij MA, Mohamed MO, Ibahim SY, Alkandari FA, Bradley DA (2014) Toward standardising gamma camera quality control procedures, Radiation Physics and Chemistry
© 2015 Elsevier Ltd. Attaining high standards of efficiency and reliability in the practice of nuclear medicine requires appropriate quality control (QC) programs. For instance, the regular evaluation and comparison of extrinsic and intrinsic flood-field uniformity enables the quick correction of many gamma camera problems. Whereas QC tests for uniformity are usually performed by exposing the gamma camera crystal to a uniform flux of gamma radiation from a source of known activity, such protocols can vary significantly. Thus, there is a need for optimization and standardization, in part to allow direct comparison between gamma cameras from different vendors. In the present study, intrinsic uniformity was examined as a function of source distance, source activity, source volume and number of counts. The extrinsic uniformity and spatial resolution were also examined. Proper standard QC procedures need to be implemented because of the continual development of nuclear medicine imaging technology and the rapid expansion and increasing complexity of hybrid imaging system data. The present work seeks to promote a set of standard testing procedures to contribute to the delivery of safe and effective nuclear medicine services.
Daar E, Chika S, Barnes S, Bradley DA, Al Mugren KS (2015) XRF measurements of Zn, Sr and Pb in archaeological bone, X-Ray Spectrometry
We study elemental concentrations in archaeological human bone, linked to interest in essential element homeostasis and also uptake of potentially harmful elements; the study of elemental concentrations in ancient skeletal remains can potentially be linked with modern studies, providing a reference to high exposure levels no longer common today. The samples, adult bone from the Romano-British period, were obtained from Cirencester, located approximately 150km to the west of London. Some of the remains were found in stone enclosures, others in Pb-lined enclosures, and yet, others devoid of a record of the form of burial. Using a measurement arrangement consisting of a low-energy mini-X-ray generator and a Si-PIN detector, results are obtained of periosteal (bone surface) concentrations, the influence of the post-mortem environment being clearly differentiated from in vivo uptake. Simultaneous multi-element measurements have been made of Zn, Sr and Pb, with respective concentrations in the range 27±16 to 254±17¼gg; 33±16 to 124±17¼gg and 44±15 to ~10% Pbg of interrogated medium. Lead-lined burials result in Pb contamination of the inner (cambium/osteogenic) surface layer of the bone, positively skewing Pb data.
Wells K, Bradley DA (2012) A review of X-ray explosives detection techniques for checked baggage., Appl Radiat Isot 70 (8) pp. 1729-1746
In recent times, the security focus for civil aviation has shifted from hijacking in the 1980s, towards deliberate sabotage. X-ray imaging provides a major tool in checked baggage inspection, with various sensitive techniques being brought to bear in determining the form, and density of items within luggage as well as other material dependent parameters. This review first examines the various challenges to X-ray technology in securing a safe system of passenger transportation. An overview is then presented of the various conventional and less conventional approaches that are available to the airline industry, leading to developments in state-of-the-art imaging technology supported by enhanced machine and observer-based decision making principles.
Asaduzzaman KH, Khandaker MU, Amin YM, Zainuddin Z, Farook MS, Bradley DA (2015) Measurement of radioactivity and heavy metal levels in edible vegetables and their impact on Kuala Selangor communities of Peninsular Malaysia., Radiat Prot Dosimetry 167 (1-3) pp. 165-170
Vegetable is an essential daily diet item for the people of Malaysia. This work addressed the radiation and heavy metal exposure scenarios through the consumption of vegetables. Kuala Selangor is located in Sungai Selangor estuary in the west coast of Peninsular Malaysia, which is susceptible to pollution load due to the presence of large-scale industrial and human activities. Radioactivity and heavy metals level in human diet is of particular concern for the assessment of possible radiological and chemical hazards to human health. Therefore, a comprehensive study was carried out to determine the radioactivity levels ((226)Ra, (228)Ra and (40)K) and heavy metal concentrations (Cr, As, Cd, Mn, Mg, Al, Sr, Rb, Sb, Ba, Hg, Fe, Ni, Zn, Cu, Bi and Pb) in 10 varieties of vegetable collected from different farmlands in Kuala Selangor region. The committed doses for (226)Ra, (228)Ra and (40)K due to consumption of vegetables were found 16.6±1.3, 23.6±1.7 and 58±5 µSv y(-1), respectively, with a total of 98±8 µSv y(-1). This dose imposes no significant threat to human health. The estimated cancer risk shows that probability of increase in cancer risk from daily intake of vegetables is only a minor fraction of International Commission on Radiological Protection values. The concentrations of heavy metal were below the daily intake recommended by the international organisations.
Kaabar W, Daar E, Bunk O, Farquharson MJ, Laklouk A, Bailey M, Jeynes C, Gundogdu O, Bradley DA (2011) Elemental and structural studies at the bonecartilage interface, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 786-790
Bajoga A, Alazemi N, Shams H, Regan PH, Bradley DA (2016) Evaluation of naturally occurring radioactivity across the State of
Kuwait using high-resolution gamma-ray spectrometry,
Radiation Physics and Chemistry 137 pp. 203-209 Elsevier
A study of natural radioactivity from 90 different soil samples from the state of Kuwait has been carried out to ascertain the NORM concentration values across the country. The calculated activity concentrations were determined from: (i) the decays of the 226Ra, 214Pb and 214Bi members of the 4n+2 decay chain headed by 238U and; (ii) the 228Ac, 212Pb and 208Tl members of the 4n chain headed by 232Th. The study also included evaluations for the 235U decay chain with the 186 keV doublet transition used together with the measured 4n+2 activity concentration values to determine the 235U/238U isotopic ratios for each sample. The values for the arithmetic mean activity concentrations for 90 separate locations across Kuwait as determined in the current work were 17.2, 14.1, and 368 Bq/kg, with standard deviations of 5.2, 3.7 and 90 Bq/kg for the 238U, 232Th and 40K activity concentrations respectively. Measured isotope ratios for 235U/238U give an arithmetic mean value for all of the samples of 0.045±0.003, consistent with that expected for natural uranium. These results indicate no evidence for a radiologically significant dispersion of additional depleted uranium across the entire State of Kuwait from the 1991 Gulf War.
Abubakar Y, Taggart M, Alsubaie A, Alanazi A, Alyahyawi A, Lohstroh A, Shutt A, Jafari S, Bradley D (2016) Characterisation of an isotropic neutron source: a comparison of conventional neutron detectors and micro-silica glass bead thermoluminescent detectors, Radiation Physics and Chemistry 140 pp. 497-501 Elsevier
As a result of their thermoluminescent response, low cost commercial glass beads have been demonstrated to offer potential use as radiation dosimeters, providing capability in sensing different types of ionising radiation. With a linear response over a large range of dose and spatial resolution that allows measurements down to the order of 1 mm, their performance renders them of interest in situations in which sensitivity, dynamic range, and fine spatial resolution are called for. In the present work, the suitability of glass beads for characterisation of an AmericiumBeryllium (241AmBe) neutron source has been assessed. Direct comparison has been made using conventional 3He and boron tri-fluoride neutron detectors as well as Monte Carlo simulation. Good agreement is obtained between the glass beads and gas detectors in terms of general reduction of count rate with distance. Furthermore, the glass beads demonstrate exceptional spatial resolution, leading to the observation of fine detail in the plot of dose versus distance from source. Fine resolution peaks arising in the measured plots, also present in simulations, are interesting features which based on our best knowledge have previously not been reported. The features are reproduced in both experiment and simulation but we do not have a firm reason for their origin. Of greater clarity is that the glass beads have considerable potential for use in high spatial resolution neutron field characterisation, subject to the availability of a suitable automated TLD reader.
Begum M, Rahman AKMM, Abdul-Rashid HA, Yusoff Z, Begum M, Mat-Sharif KA, Amin YM, Bradley DA (2015) Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry, Applied Radiation and Isotopes 100 pp. 79-83
© 2014 Elsevier Ltd.Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ~0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100¼m core diameter fiber provides highest response that is 2.6 times than that of smallest core (20¼m core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25-13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6-13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry.
Kaabar W, Daar E, Bunk O, Farquharson MJ, Laklouk A, Bailey M, Jeynes C, Gundogdu O, Bradley DA (2010) Elemental and structural studies at the bone-cartilage interface, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652 (1) pp. 786-790 Elsevier
Saeed Al-Ahbabi S, Bradley DA, Nisbet A, Beyomi M, Alkatib Z, Adhaheri S, Darmaki M (2012) A comparison of protocols for external beam radiotherapy beam calibrations, Applied Radiation and Isotopes 70 (7) pp. 1331-1336
A number of codes of practice (CoP) for electron and photon radiotherapy beam dosimetry are currently in use. Comparison is made of the more widely used of these, specifically those of the International Atomic Energy Agency (IAEA TRS-398), the American Association of Physicists in Medicine (AAPM TG-51) and the Institute of Physics and Engineering in Medicine (IPEM 2003). All are based on calibration of ionization chambers in terms of absorbed dose to water, each seeking to reduce uncertainty in delivered dose, providing an even stronger system of primary standards than previous air-kerma based approaches. They also provide a firm, traceable and straight-forward formalism (Radiology, 1996). Included in making dose assessments for the three CoP are calibration coefficients for a range of beam quality indices. Measurements have been performed using clinical photon and electron beams, the absorbed dose to water being obtained following the recommendations given by each code. Electron beam comparisons have been carried out using measurements for electron beams of nominal energies 6, 9, 12, 16 and 20. MeV. Comparisons were also carried out for photon beams of nominal energies 6 and 18. MV. For photon beams use was made of NE2571 cylindrical graphite walled ionization chambers, cross-calibrated against an NE2611 Secondary Standard; for electron beams, PTW Markus and NACP-02 plane-parallel chambers were used. Irradiations were made using Varian 600C/2100C linacs, supported by water tanks and Virtual Water" phantoms. The absorbed doses for photon and electron beams obtained following these CoP are all in good agreement, with deviations of less than 2%.A number of studies have been carried out by different groups in different countries to examine the consistency of dosimetry codes of practice or protocols. The aim of these studies is to confirm that the goal of those codes is met, namely uniformity in establishment of dosimetry of all radiation beam types used in cancer therapy in the world, and this is one of the studies. © 2011 Elsevier Ltd.
Da Silva F, Bradley DA, Regan PH, Siti Rozaila Z (2016) Measurement of the total activity concentrations of Libyan oil scale, Radiation Physics and Chemistry 137 pp. 198-202 Elsevier
Twenty-three oil scale samples obtained from the Libyan oil and gas industry production facilities onshore have been measured using high-resolution gamma-ray spectrometry with a shielded HPGe detector, the work being carried out within the Environmental Radioactivity Laboratory at the University of Surrey. The main objectives of this work were to determine the extent to which the predominant radionuclides associated with the uranium and thorium natural decay chains were in secular equilibrium with their decay progeny, also to compare differences between the total activity concentrations (TAC) in secular equilibrium and disequilibrium and to evaluate the measured activities for the predominant gamma-ray emitting decay radionuclides within the 232Th and 238U chains. The oil scale NORM samples did not exhibit radioactive equilibrium between the decay progeny and longer-lived parent radionuclides of the 238U and 232Th series.
Jafari S, Jordan T, Hussein M, Bradley DA, Clark C, Nisbet A, Spyrou NM (2014) Energy response of glass bead TLDs irradiated with radiation therapy beams, RADIATION PHYSICS AND CHEMISTRY 104 pp. 208-211 PERGAMON-ELSEVIER SCIENCE LTD
Glass beads are a novel TL dosimeter in radiotherapy. An important characteristic of TL dosimeters is
their energy response, especially when intended for use in radiotherapy applications over a wide range
of energies (typically from X-rays generated at 80 kVp up to 25 MV photon and MeV electron beams). In
this paper, the energy response of glass beads (Mill Hill, Japan) is investigated for their TL response to kV
X-rays from an orthovoltage radiotherapy unit and also for MV photon and MeV electron beams from a
medical linear accelerator. The experimental findings show that for photon and electron beams, the TL
response of this particular glass bead, normalised to unity for 6 MV X-rays (TPR20/10¼0.670), decreases
to 0.9670.02 for 15 MV X-rays (TPR20/10¼0.761) and to 0.9570.01 for 20 MeV electron beams
(R50,D¼8.35 cm). This compares favourably with other TLD materials such as LiF and also alanine
dosimeters that are readout with an EPR system. For kV X-rays, the response increases to 4.5270.05 for
80 kV X-rays (HVL¼2.4 mm Al) which approaches 3 times that of LiF TLDs and 5 times that of alanine.
In conclusion, the particular glass beads, when used as a dosimeter material, show a relatively small
energy dependence over the megavoltage range of clinically relevant radiation qualities, being clearly
advantageous for accurate dosimetry. Conversely, the energy response is significant for photon beam
energies covering the kV range. In both circumstances, in dosimetric evaluations the energy response
needs to be taken into account.
Advances in Nanotechnology enable us to structure new materials at the nanoscale and develop novel systems capable of active response of X-rays and sensing humidity. Carbon nanomaterials are two-dimensional sheets of
Bradley DA, Abdul Sani S, Alalawi A, Jafari S, Nisbet A, Noor N, Hairul Azhar A, Mahdiraji G, Tamchek N, Ghosh S, Paul M, Alzimami K, Maah M (2014) Development of tailor-made silica fibres for TL dosimetry, Radiation Physics and Chemistry 104 pp. 3-9
The Ge dopant in commercially available silica optical fibres gives rise to appreciable thermoluminscence (TL), weight-for-weight offering sensitivity to MV X-rays several times that of the LiF dosimeter TLD100. The response of these fibres to UV radiation, X-rays, electrons, protons, neutrons and alpha particles, with doses from a fraction of 1Gy up to 10kGy, have stimulated further investigation of the magnitude of the TL signal for intrinsic and doped SiO fibres. We represent a consortium effort between Malaysian partners and the University of Surrey, aimed at production of silica fibres with specific TL dosimetry applications, utilizing modified chemical vapour deposition (MCVD) doped silica-glass production and fibre-pulling facilities. The work is informed by defect and dopant concentration and various production dependences including pulling parameters such as temperature, speed and tension; the fibres also provide for spatial resolutions down to
Issa F, Abdul Rahman A, Hugtenburg R, Bradley DA, Nisbet A (2012) Establishment of Ge-doped optical fibres as thermoluminescence dosimeters for brachytherapy, Applied Radiation and Isotopes 70 (7) pp. 1158-1161 Elsevier
This study aims to establish the sensitive, ~120¼m high spatial resolution, high dynamic range Ge-doped optical fibres as thermoluminescence (TL) dosimeters for brachytherapy dose distribution. This requires investigation to accommodate sensitivity of detection, both for the possibility of short range dose deposition from beta components as well as gamma/x-mediated dose. In-air measurements are made at distances close to radionuclide sources, evaluating the fall off in dose along the transverse axis of Ba and Co radioactive sources, at distances from 2mm up to 20mm from their midpoints. Measurements have been compared with Monte Carlo code DOSRZnrc simulations for photon-mediated dose only, agreement being obtained to within 3% and 1% for the Ba and Co sources, respectively. As such, in both cases it is determined that as intended, beta dose has been filtered out by source encapsulation. © 2012 Elsevier Ltd.
Choulis S, Kim Y, Nelson J, Bradley DA, Giles M, Shkunov M, McCulloch I (2004) High Ambipolar and Balanced Carrier Mobility in Regioregular Poly(3-hexylthiophene), Applied Physics Letters 85 (17) AIP Publishing

The carrier transport of carefully purified regioregular poly(3-hexylthiophene) films was studied using time-of-flight photocurrent measurements. The authors find balanced ambipolar transport with a room-temp. mobility for holes of 3 * 10-4 cm2 V-1 s-1 and for electrons of 1.5 * 10-4 cm2 V-1 s-1 at elec. fields >=105 V/cm. The transport is relatively field independent and weakly temp. dependent, pointing to a high degree of chem. regioregularity and purity. These factors make poly(3-hexylthiophene) attractive for use in a range of electronic applications.

Kamali-Zonouzi P, Shutt A, Nisbet A, Bradley D (2017) Feasibility of employing thick microbeams from superficial and orthovoltage kVp x-ray tubes for radiotherapy of superficial cancers, Radiation Physics and Chemistry 140 pp. 237-241 Elsevier
Preclinical investigations of thick microbeams show these to be feasible for use in radiotherapeutic dose delivery. To create the beams we access a radiotherapy x-ray tube that is familiarly used within a conventional clinical environment, coupling this with beam-defining grids. Beam characterisation, both single and in the form of arrays, has been by use of both MCNP simulation and direct Gafchromic EBT film dosimetry. As a first step in defining optimal exit-beam profiles over a range of beam energies, simulation has been made of the x-ray tube and numbers of beam-defining parallel geometry grids, the latter being made to vary in thickness, slit separation and material composition. For a grid positioned after the treatment applicator, and of similar design to those used in the first part of the study, MCNP simulation and Gafchromic EBT film were then applied in examining the resultant radiation profiles. MCNP simulations and direct dosimetry both show useful thick microbeams to be produced from the x-ray tube, with peak-to-valley dose ratios (PVDRs) in the approximate range 8.8?13.9. Although the potential to create thick microbeams using radiotherapy x-ray tubes and a grid has been demonstrated, Microbeam Radiation Therapy (MRT) would still need to be approved outside of the preclinical setting, a viable treatment technique of clinical interest needing to benefit for instance from substantially improved x-ray tube dose rates.
Abdul Sani S, Alalawi A, Nisbet A, Bradley DA, Azhar A R H, Amouzad Mahdiraji G, Tamchek N, Maah M (2014) High sensitivity flat SiO fibres for medical dosimetry, Radiation Physics and Chemistry 104 pp. 134-138
We describe investigation of a novel undoped flat fibre fabricated for medical radiation dosimetry. Using high energy X-ray beams generated at a potential of 6MV, comparison has been made of the TL yield of silica flat fibres, TLD-100 chips and Ge-doped silica fibres. The flat fibres provide competitive TL yield to that of TLD-100 chips, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20nm up to 80nm. The dose enhancement factor (DEF) of (0.0150±0.0003)nm Pt is comparable to that obtained using gold, agreeing at the 1% level with the value expected on the basis of photoelectron generation. Finally, X-ray photoelectron spectroscopy (XPS) has been employed to characterize the surface oxidation state of the fibre medium. The charge state of Si2p was found to lie on 103.86eV of binding energy and the atomic percentage obtained from the XPS analysis is 22.41%. © 2014 Elsevier Ltd.
Alalawi A, Nisbet A, Alzimami K, Bradley DA, Hugtenburg R, Abdul Rahman A, Barry M (2014) Measurement of dose enhancement close to high atomic number media using optical fibre thermoluminescence dosimeters, Radiation Physics and Chemistry 95 pp. 145-147
Present interest concerns development of a system to measure photoelectron-enhanced dose close to a tissue interface using analogue gold-coated doped silica-fibre thermoluminescence detectors and an X-ray set operating at 250. kVp. Study is made of the dose enhancement factor for various thicknesses of gold; measurements at a total gold thickness of 160. nm (accounting for incident and exiting photons) produces a mean measured dose enhancement factor of 1.33±0.01 To verify results, simulations of the experimental setup have been performed. © 2013 Elsevier Ltd.
Bardi N, Jurewicz I, King A, Alkhorayef M, Bradley D, Dalton A (2017) X-ray irradiation-induced structural changes on Single Wall Carbon Nanotubes, Radiation Physics and Chemistry 140 pp. 34-37 Elsevier
Dosimetry devices based on Carbon Nanotubes are a promising new technology. In particular using devices based on single wall carbon nanotubes may offer a tissue equivalent response with the possibility for device miniaturisation, high scale manufacturing and low cost. An important precursor to device fabrication requires a quantitative study of the effects of X-ray radiation on the physical and chemical properties of the individual nanotubes. In this study, we concentrate on the effects of relatively low doses, 20 cGy and 45 cGy, respectively. We use a range of characterization techniques including scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to quantify the effects of the radiation dose on inherent properties of the nanotubes. Specifically we find that the radiation exposure results in a reduction in the sp2 nature of the nanotube bond structure. Moreover, our analysis indicates that the exposure results in nanotubes that have an increased defect density which ultimately effects the electrical properties of the nanotubes.
Scuffham J, Yip-Braidley M, Shutt A, Hinton P, Nisbet A, Bradley DA (2016) Adapting clinical gamma cameras for body monitoring in the event of a large-scale radiological incident, JOURNAL OF RADIOLOGICAL PROTECTION 36 (2) pp. 363-381 IOP PUBLISHING LTD
After a release of radionuclides, accidental or otherwise, there will be an urgent need to identify members of the general public who have received a significant intake of radioactive material, sufficient to require medical treatment or further investigation. A large number of people could be contaminated in such an incident. For gamma-ray emitting radionuclides this screening could be carried out using gamma camera medical imaging systems, such as those that are present in many large UK hospital sites. By making a number of simple reversible changes such as removal of collimators, these cameras could be employed as useful additional screening instruments as well as an aid in contamination control. A study was carried out to investigate which systems were present in sufficient number to offer wide scale coverage of UK population centres. Nine gamma cameras (eight dual head and one single head) were assessed using point source and bottle mannequin (BOMAB) phantom measurements so that a mathematical model could be developed for use with the MCNPX Monte Carlo radiation transport code. The gamma camera models were assessed for practical seated and supine geometries to give calibration factors for a list of target radionuclides that could be released in a radiological incident. The minimum detectable activities (MDAs) that were achieved for a five minute measurement demonstrated that these systems are sufficiently sensitive to be used for screening of the general public and are comparable to other body monitoring facilities. While gamma cameras have on-board software that are designed for imaging and provide for a gamma-ray energy range suitable for radionuclides for diagnostic imaging (such as 99mTc), they are not as versatile as custom-built body monitoring systems.
Bradley DA, Hugtenburg R, Nisbet A, Abdul Rahman A, Issa F, Mohd Noor N, Alalawi A (2012) Review of doped silica glass optical fibre: Their TL properties and potential applications in radiation therapy dosimetry, Applied Radiation and Isotopes 71 (SUPPL.) pp. 2-11 Elsevier
Review is made of dosimetric studies of Ge-doped SiO telecommunication fibre as a 1-D thermoluminescence (TL) system for therapeutic applications. To-date, the response of these fibres has been investigated for UV sources, superficial X-ray beam therapy facilities, a synchrotron microbeam facility, electron linear accelerators, protons, neutrons and alpha particles, covering the energy range from a few eV to several MeV. Dosimetric characteristics include, reproducibility, fading, dose response, reciprocity between TL yield and dose-rate and energy dependence. The fibres produce a flat response to fixed photon and electron doses to within better than 3% of the mean TL distribution. Irradiated Ge-doped SiO optical fibres show limited signal fading, with an average loss of TL signal of ~0.4% per day. In terms of dose response, Ge-doped SiO optical fibres have been shown to provide linearity to x and electron doses, from a fraction of 1Gy up to 2kGy. The dosimeters have also been used in measuring photoelectron generation from iodinated contrast media; TL yields being some 60% greater in the presence of iodine than in its absence. The review is accompanied by previously unpublished data. © 2012 Elsevier Ltd.
Al-Ahbabi S, Bradley DA, Nisbet A (2013) Tomotherapy evaluation for head and neck cases using two types of phantoms, Radiation Physics and Chemistry 95 pp. 323-325 Elsevier
The use of rotational therapy as an important method of treatment delivery is expected to increase due in a large part to the development and utilisation of tomotherapy. Rotational therapy minimises the occurrence of hotspots and the irradiation of critical organs, providing more uniform dosing while sparing critical organs. Two important characteristics of rotational radiation are its dynamic nature and dosimetric variability in radiation delivery, both of which present a considerable challenge for clinical physicists seeking appropriate tools to meet the demands of quality assurance.In this paper 15 Delivery Quality Assurance (DQA) plans of head and neck patients were assessed for the Hi-Art tomotherapy system using Kodak X-Omat V film and an A1SL Ref F92722 ion chamber versus MapCheck. Absolute dose measurement showed average differences of 3.42. cGy and 98% Gamma (³) factor for the Cheese phantom technique. For the MapCheck technique the average difference and Gamma factor were 0.74. cGy and 96%, respectively. Gamma (³) matrix distribution was used to evaluate the difference between measured and calculated dose distribution. © 2013 Elsevier Ltd.
This work encompasses characterisation of defects and dosimetric studies of novel tailor made doped SiO2 fibres. Present studies have been carried out seeking to improve upon the thermoluminescence (TL) yield of commercially produced small diameter telecommunication optical fibres. Using the modified chemical vapour deposition (MCVD) process, the optical fibres have been fabricated to a range of dopant concentrations of nominal value 6- 8- and 10 wt%. In this study, three different types of optical fibres have been utilised, made using the same doped preform. The doped fibres are cylindrical fibres (CF), flat fibres (FF) and photonic crystal fibres (PCF). It should be noted that the process of fibre drawing has been found to produce defect centres, influencing characteristics of optical fibre and TL response. To seek support of this, an X-ray Photoelectron Spectroscopy (XPS) study of a Ge doped SiO2 fibres sample has been undertaken to determine the oxidation state of Ge. Results from this have confirmed the efficiency of the surface analysis technique, leading to understanding of the Ge structure. Following on from this, facilities supporting characterization of the fibres are outlined, including an ion beam facility used for Particle Induced X-ray
Emission (PIXE)/Rutherford Back Scattering (RBS) analysis to localize and determine the concentration of Ge dopants. Building upon these characterisations, thermoluminescence studies were carried out. For the first of the experiment, undoped flat fibres were used, comparison of response being made with that of conventional TLD-100 and commercial Ge-doped silica fibres. The undoped flat fibres provide competitive TL yield to that of TLD-100, being some 100 times that of the Ge-doped fibres. Pt-coated flat fibres have then been used to increase the photoelectron production and hence local dose deposition, obtaining significant increase in dose sensitivity over that of undoped flat fibres. Using 250 kVp X-ray beams, the TL yield reveals a progressive linear increase in dose for Pt thicknesses from 20 nm up to 80 nm. Finally, to illustrate the potential of novel tailor-made doped SiO2 optical fibres, the dosimetric characteristics that have been investigated include, dose response, glow curves and energy dependence. Taking TLD-100 as a benchmark, results are presented for Ge-doped, Ge-B-doped and Ge-Br-doped optical fibres. The dose response of doped silica fibres was found to be linear over the range 2 cGy up to 50 Gy, also showing good dosimetric response for low photon energies. Additional investigation of the same doped SiO2 optical fibres have been conducted for measurement of TL yield from the high linear energy transfer (LET) radiation offered by a liquid 223Ra alpha particle source.
Abstract

Glioblastoma (GBM) is a known photon radio-resistant tumour and charged ion therapy could be an alternative treatment to improve survival and quality of life. This work aims to determine the effects of ion species, 4He, 12C, 20Ne, 28Si and 56Fe and photon 200 kVp X-rays - 1.7 keV/µm on three different glioblastoma cell lines, T98G, U87 and LN18. Their capacity for potential lethal damage repair (PLDR) was also examined. Mono-energetic beams of 4He, 12C, 20Ne, 28Si and 56Fe were generated by the Heavy Ion Medical Accelerator at Chiba at the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. X-rays experiments were also performed at NIRS.

The linear energy transfer (LET) of charged ions used ranges from 2.3 - 200 keV/µm, covering the entrance (plateau) to clinically relevant and high LETs that simulate space radiation. Space radiation biology was an opportunistic study at NIRS. Exposure to space radiation is known to be a high risk to the central nervous system. It is acknowledged that there are benefits and limitations of using GBM cell lines to study space radiation. Using GBM cell line which arises from the brain may aid in the understanding of the effects of space radiation to the brain. Moreover, some strains of GBM cell lines are low dose hypersensitive and very low doses that are used to study space radiation maybe relevant. The limitation is that they are not normal cells such as the lymphocytes or fibroblast; hence, restrictions may have to be applied when interpreting these results. Clonogenic assay was used to determine the efficacy of the radiations. For potential lethal damage repair (PLDR) study, the cells were allowed 24 hours to repair before plating out.

Results show that LN18 relative biological effectiveness at 10% survival (RBE10) increases with LET and peaks 85 at keV/µm; however, both T98G and U87 at 200 keV/µm. LN18 ± (single hit kill) peaks at 200 keV/µm, whereas, U87 and T98G peak at 100 keV/µm. The statistical significance between the mean of RBE10; and of the mean of ± between the three GBM cell lines (p

Keywords: Glioblastoma (GBM), ion therapy, carbon ions, neon ions, helium ions, silicon ions, iron ions, PLDR, PLDR-ratio, LET, RBE10, RBE2 Gy, RSF2 Gy, ± parameter, ² parameter, ±/² ratio, and space radiation.

Ley Katie, Jafari S.M., Lohstroh Annika, Shenton-Taylor Caroline, Bradley David (2019) Thermoluminescent Response of Beta-irradiated Silica Beads, Radiation Physics and Chemistry 154 pp. 32-37 Elsevier
Research into the potential for silica based materials as TLDs continues to increase, harnessing the various advantages that the materials have to offer as a dosimeter, including; affordability, chemical inertness, geometry and size, while producing suitable TL yields. Studies into the possibility of beta source dosimetry open another range of applications for this type of dosimeter, including procedures involving the possibility of in vivo dosimetry (Morino et al., 2002). This work aims to further investigate the properties of a much-studied batch of Mill Hill silica beads of various colours, irradiated with a SR90/Y90 source yielding a dose rate of 0.02 Gy/s, activity 37 MBq and maximum energy of 2.27 MeV, facilitated by the Ris
ø
TL/OSL reader. The TL yield is compared to that in previous work, with the same set of beads irradiated by a 6 MV photon beam provided by a Varian electron linac (Varian Medical Systems, Palo Alto, CA) X-ray source, delivering a dose of 10 Gy. Present study shows a decrease in the mass normalised TL yield from X-ray to beta source by a factor of 10, assumed to be accounted for by the estimated mean penetration depth of the beta particles in the doped silica beads. Investigating the potential for doped silica beads to be used as a beta source dosimeter a linearity study is reported with a dose range of 5 to 20 Gy. The studies show that all coloured beads except green show a strong conformity to a linear fit of the data over the tested range of doses. Fading studies conducted with clear petite beads (producing the greatest TL yield/mg) for doses of 5 Gy and 20 Gy have shown that the majority of fading occurs within the first hour following irradiation, with a plateau in the fading to approximately 17 % and 22 % loss of signal for 5 Gy and 20 Gy respectively in the interval of 24 hours to 70 hours after irradiation. The decay of the TL yield/mg was fitted to a logarithmic trend of reduction for both the 5 Gy and 20 Gy irradiation, with values of 0.9883 and 0.9705 respectively.
Jafari S, Gouldstone C, Sharpe P, Alalawi A, Bradley D, Clark C, Nisbet A, Spyrou N (2013) Low-cost commercial glass beads as dosimeters in radiotherapy,
Jafari S, Gouldstone C, Sharpe P, Bradley D, Clark C, Nisbet A, Spyrou N (2013) Characterisation of Glass Beads for Radiotherapy Dosimetry, Proceedings of the 7th United Kingdom & Republic of Ireland Postgraduate Conference in Biomedical Engineering and Medical Physics pp. p15-15
Examinations have been made of a low cost commercially available material which is potentially useful as a dosimeter in radiotherapy. An investigation of the thermoluminescent (TL) yield and electron paramagnetic resonance (EPR) signal was performed by irradiating acid-washed glass jewellery beads to MV photons using a medical linear-accelerator and 60Co gamma rays. For
comparison, irradiation exposures were also carried
out on 5 mm length of Ge-doped optical fibres that
have been widely investigated for their TL properties
[1].
The dose response was linear for the investigated
dose range of 1 to 2500 cGy, with an R2 correlation
coefficient of > 0.999 and reproducibility of 1.7%.
The results suggest the potential for use of glass
beads as TL dosimeters in radiotherapy.
Jafari S, Bates N, Jupp T, Abdul Sani S, Nisbet A, Bradley D (2016) Characterisation of commercial glass beads as TLDs in radiotherapy, Radiation Physics and Chemistry 137 pp. pp181-186 Elsevier
Jafari S, Bates N, Jupp T, Abdul Sani S, Nisbet A, Bradley D (2016) Commercial glass beads as TLDs in radiotherapy produced by different manufacturers, Radiation Physics and Chemistry 137 pp. pp181-186 www.elsevier.com
While commercial jewellery glass beads offer the basis of novel radiotherapy TL dosimetry (Jafari et al.
2014a,b,c, 2015a,b), detailed study of TL variation is required for the products from various manufacturers.
Investigation is made for glass beads from four manufacturers from four countries: China (Rocaille), Japan (Mill Hill), Indonesia (TOHO") and Czech Republic (Czech). Sample composition was determined using an energy-dispersive X-ray unit coupled to a scanning electron microscope. Values of mass attenuation coefficient, ¼/Á, as a function of photon energy were then calculated for photons of energy 1 keV to 10 MeV, using the National Institute of Standards and Technology XCOM program. Radiation and energy response were determined using X-rays generated at accelerating potentials from 80 kVp to 6 MV (TPR20/10¼0.670).
All bead types showed TL to be linear with dose (R240.999). Glow curve dosimetric peaks reached a
maximum value at 300 °C for the Toho and 290 °C for the Czech and Mill Hill products but was between
200?250 °C for the Rocaille product. Radiation sensitivity following mass normalisation varied within an
order of magnitude; Toho samples showed the greatest and Rocaille the least sensitivity. For the Toho,
Czech, Rocaille and Mill Hill samples the energy responses at 80 kVp were 5.0, 4.0, 3.6 and 3.3 times that
obtained at 6 MV. All four glass bead types offer potential use as TL dosimeters over doses commonly
applied in radiotherapy. Energy response variation was o1% at 6 MV but significant variation was found
for photon beam energies covering the kV range; careful characterisation is required if use at this range is
intended.
Bradley D, Siti Shafiqah A, Siti Rozaila Z, Sabtu S, Abdul Sani S, Alanazi A, Jafari S, Amouzad Mahdiraji G, Mahamd Adikan F, Maah M, Nisbet A, Tamchek N, Abdul Rashid H, Alkhorayef M, Alzimami K (2016) Developments in production of silica-based thermoluminescence dosimeters, Radiation Physics and Chemistry 137 pp. 37-44 http://www.elsevier.com/
This work addresses purpose-made thermoluminescence dosimeters (TLD) based on doped silica fibres and sol?gel nanoparticles, produced via Modified Chemical Vapour Deposition (MCVD) and wet chemistry techniques respectively. These seek to improve upon the versatility offered by conventional phosphor-based TLD forms such as that of doped LiF. Fabrication and irradiation-dependent factors are seen to produce defects of differing origin, influencing the luminescence of the media. In coming to a close, we illustrate the utility of Ge-doped silica media for ionizing radiation dosimetry, first showing results from gamma-irradiated Ag-decorated nanoparticles, in the particular instance pointing to an extended dynamic range of dose. For the fibres, at radiotherapy dose levels, we show high spatial resolution (0.1 mm) depth-dose results for proton irradiations. For novel microstructured fibres (photonic crystal fibres, PCFs) we show first results from a study of undisturbed and technologically modified naturally occurring radioactivity environments, measuring doses of some 10 s of ¼Gy over a period of several months.
Abdul Sani S, Hammond R, Jafari S, Wahab N, Amouzad Mahdiraji G, Siti Shafiqah A, Abdul Rashid H, Maah M, Aldousari H, Alkhorayef M, Alzimami M, Bradley D (2016) Measurement of a wide-range of X-ray doses using specialty doped silica fibres, Radiation Physics and Chemistry 137 pp. 49-55 http://www.elsevier.com/
Using six types of tailor-made doped optical fibres, we carry out thermoluminescent (TL) studies of X-rays, investigating the TL yield for doses from 20 mGy through to 50 Gy. Dosimetric parameters were investigated for nominal 8 wt% Ge doped fibres that in two cases were co-doped, using B in one case and Br in the other. A comparative measurement of surface analysis has also been made for non-annealed and annealed capillary fibres, use being made of X-ray Photoelectron Spectroscopy (XPS) analysis. Comparison was made with the conventional TL phosphor LiF in the form of the proprietary product TLD-100, including dose response and glow curves investigated for X-rays generated at 60 kVp over a dose range
from 2 cGy to 50 Gy. The energy response of the fibres was also performed for X-rays generated at peak
accelerating potentials of 80 kVp, 140 kVp, 250 kVp and 6 MV photons for an absorbed dose of 2 Gy. Present results show the samples to be suitable for use as TL dosimeters, with good linearity of response and a simple glow curve (simple trap) distribution. It has been established that the TL performance of an irradiated fibre is not only influenced by radiation parameters such as energy, dose-rate and total dose but also the type of fibre.
Jafari S M, Distefano G, Bradley D, Spyrou N M, Nisbet A, Clark C H (2014) Validation of glass bead TLDs for radiotherapy treatment verification, Radiotherapy and Oncology 111 (1) PO-0793 pp. p317-317 0167-8140
Alalawi A, Jafari S, Najem M, Clark K, Nisbet A, Abolaban F, Hugtenburg R, Hussein M, Alzimami K, Spyrou N, Bradley D (2013) Comparison of Ge-doped TL optical fibres and glass beads with ion chamber and Gafchromic film for small field photon dosimetry, 1st International Conference on Dosimetry and its Applications - Book of abstracts pp. pp1-206 ?eské vysoké u
ení technické v Praze Fakulta jaderná a fyzikáln? in~enýrská
Small field (d 4 × 4 cm) photon radiotherapy treatments include intensity-modulated radiation therapy (IMRT)and stereotactic body radiation therapy (SBRT). These require small, high spatial resolution dosimeters of adequate dynamic range. In this study, field sizes of 1 cm ×
1 cm, 2 cm × 2 cm, 3 cm × 3 cm, 4 cm × 4 cm, and 10 cm × 10 cm have been investigated using commercially available silica-based fibres and glass beads (GB) as TL dosimeters and a Varian linear accelerator operating at 6, 10 and 15 MV. Ge-doped SiO2 fibres have previously been shown by this group to offer a viable system for use as dosimeters. The fibres and GB, offer good spatial resolution ( 2 mm respectively), large dynamic dose range (with linearity from tens of mGy up to well in excess of many tens of Gy), a non-hygroscopic nature and low cost. The
main aim of this present work is to investigate the use of Ge-doped optical fibres and GBs as thermoluminescence dosimeters in small photon fields for different photon beam energies, comparing the measurements against Gafchromic films, hospital commissioning data obtained from small
ionisation chambers and photon diodes and Monte Carlo simulations with FLUKA and BEAMnrc.
Thomas R.A.S., Jafari S. M., Bradley D. A., Spyrou N. M., Nisbet A., Clark C.H. (2014) PO-0796: Dosimetric characterisation of glass bead TLDs in proton beams, Radiotherapy and Oncology 111 (1) PO-0796 pp. S58-S58 Elsevier
Purpose/Objective: To investigate the feasibility of using glass beads as a novel thermoluminescence dosimeter (TLD) in clinical proton radiotherapy. The glass beads have several physical characteristics which suggest their suitability for use as TLDs in this area: a spherical physical shape with a hole in the middle that facilitate their use in 2D and 3D arrangements; chemically inert nature; small size of 1.5 mm diameter and 1 mm thickness; inexpensive and readily available; reusable; and importantly their TL light transparency with negligible self-attenuation which is very important for high LET beams. Proton beams have high LET and therefore can deposit dose nonuniformly across a detector. Readout of TL detectors can be influenced if any opacity is present causing self-attenuation of TL light [1], [2]. The transparency of glass beads to TL light means the beads have the potential to avoid such issues.
Jafari Shakardokht, Distefano G., Lee J., Gouldstone C., Mayles H., Bradley D. A., Spyrou N. M., Nisbet A., Clark C. H. (2015) Feasibility of using glass bead TLDs for a postal dosimetry audit of MV radiotherapy photon beams, Proceedings of the 8th UK Radiation Oncology Conference (UKRO) Varian Medical Systems, Inc.
This work encompasses studies of two novel materials for radiation dosimetry as well establishment of a novel technique for dosimetry. Silica-based material and CNTs (carbon nanotubes) were used as passive radiation dosimeters. The atomic effective numbers (Zeff) for the silica-based materials (glass beads and optical fibres) are similar to that for the bone tissue, while carbon nanotubes have effective atomic number (Zeff) similar to that of human soft tissue. Present studies have been carried out seeking to improve upon the thermoluminescence (TL) yield of commercially produced small diameter telecommunication optical fibres as well as glass beads. Their small sizes make them of great interest as they can fulfil the Bragg?Gray cavity theory. In this thesis, demonstration is made of their utilities to measure the depth-dose profile for protons and neutrons at therapeutic energies range. In regard to carbon nanotubes, these were made in thin films (known as buckypaper) with various thickness ranging from ~10 to ~100 µm to fulfil two conditions; (i) satisfying the Bragg?Gray cavity theory, and; (ii) to present tissue equivalent material. The CNTs were examined in using conventional thermoluminescence technique. Then, a novel method of dosimetry was established by use of x-ray photoelectron spectroscopy (XPS).
An evaluation of the specific activity concentrations associated with technologically enhanced naturally occurring radioactive materials (TENORM) and anthropogenic radionuclides has been undertaken, with particular focus on produced water from the Kuwait oil industry. This work is part of a systematic study to provide a radiological map of the outer boundary of the produced water lagoon located in the Minagish oil field in the south west region of the State of Kuwait. This particular lagoon contains material from the discharge of produced water which is a by-product of oil production in the region. The lagoon samples were prepared and placed into sealed, marinelli beakers for a full gamma-ray spectrometric analysis using a high-resolution, low-background, high-purity germanium detection systems at the University of Surrey Environmental Radioactivity Laboratory. Of particular interest are the calculation of the activity concentrations associated with members of the decay chains following decays of the primordial radionuclides of the 238U chain (226Ra, 214Pb, 214Bi) and the 232Th chain (228Ra, 228Ac, 212Pb, 212Bi, 208Tl), and the enhanced concentrations of radium isotopes. This thesis presents overview of the experimental samples which have been measured and the analysis techniques applied, including isotopic correlation plots across the sample region. The result shows the expected significant increase in 226Ra (and progeny) concentrations compared to the NORM values were taken from outside of the lagoon, with 226Ra activity concentrations ranging from approximately 10 Bq/kg to 2 kBq/kg from different samples. Radium equivalent and hazard indices are calculated for different regions of the pool boundary, with some regions have hardard indices greater than unity, and therefore constituting a potential radiological hazard. The analysis also investigates the correlations between members of the 232Th and 238U chain in these samples, and shows evidence for enhancement of radium isotopes (226Ra and 228Ra) in the lagoon produced water samples compared to the background levels.
The intent of external beam radiotherapy is to deliver as high a radiation dose as possible to tumour volume whilst minimizing the dose to surrounding normal tissues. Recent development of techniques such as intensity modulated radiation therapy (IMRT) and stereotactic ablative body radiotherapy (SABR) aim to extend this capability. The main feature of these techniques is to use beams which often contain small fields and very steep dose gradients. These present several dosimetric challenges including loss of charge particle equilibrium (CPE), partial occlusion of the direct-beam source and steep fall-off in dose in the penumbra. Dosimeters which are small in size relative to the radiation field dimensions are recommended for such conditions.
The particular glass beads studied herein have several potentially favourable physical characteristics; they are small in size (1 to 3 mm diameter), chemically inert, inexpensive, readily available and reusable. The dosimetric characterisation of glass beads has been obtained by irradiating them in various radiotherapy beams of kilo-voltage and mega-voltage photons, megavoltage electrons, protons and carbon ions. They exhibit minimal fading compared with commercial LiF thermo-luminescent (TL) dosimeters, have high TL light transparency, high sensitivity and a large dynamic dose range that remains linear from 1 cGy to 100 Gy They have also been shown to be independent of dose rate and beam incidence angle, as well as having a low variation in response with energy over a range of megavoltage photon and electron beams. The latter characteristic is of importance, where spectral changes may occur as a function of field size and off axis location and for the use of dosimeters in postal audit situations where each institution may have slightly different quality index (QI) for their respective photon energies thus ensuring that the calibration is still valid. These properties suggest their practical use as TL dosimeters for radiotherapy dosimetry.
Investigations have been performed to evaluate the feasibility of using glass beads in treatment plan verification, small field radiation dosimetry and postal dosimetry audit.
Alyahyawi Amjad, Dimitriadis A., Jafari S.M., Lohstroh A., Alanazi A., Alsubaie A., Clark C.H., Nisbet A., Bradley D.A. (2019) Thermoluminescence measurements of eye-lens dose in a multi-centre stereotactic radiosurgery audit, Radiation Physics and Chemistry 155 pp. 75-81 Elsevier
Stereotactic radiosurgery (SRS), a non-invasive therapeutic technique, seeks delivery of elevated doses of ionizing radiation to precisely defined targets while at the same time preserving surrounding tissue viability. SRS was developed for treatment of various functional abnormalities, extending also to benign and malignant lesions (the latter sometimes referred to as stereotactic body radiation therapy, SBRT). Local tumour control for single and multiple brain metastases at low complication rates is one such outcome. Notable commercial SRS platforms include Gamma Knife and the linac-based systems, Novalis and Cyberknife. Such systems use imaging techniques that include computed tomography (CT) and magnetic resonance imaging (MRI) in localizing SRS targets, down to a small fraction of one mm. With a wide range of platforms for delivery of SRS, greater investigation and standardization is called for. Present work concerns a multi-centre dosimetric audit (20 centres in all), investigating the range of SRS machines and techniques for a single brain metastasis using a series of small dimension detectors (1.55/mm and less) and an anthropomorphic head phantom. With the lens as one of the more radiosensitive tissues, the aim has been to determine the scattered radiation lens dose received during an SRS treatment, as well as the imaging dose received during planning-stage CT-scanning. Custom-designed holders were fabricated to carry three types of thermoluminescence dosimeters: Ge-doped silica fibres, silica glass beads and TLD-100, the latter as a reference dosimeter (being also of larger dimension than the silica-based dosimeters). For reproducible placement of the TLD holders, a bespoke 3D-printed goggle insert was produced for the head phantom. International guidance is to seek reduction in lens dose down to 0.5/Gy. Present results show lens dose values below 0.5/Gy, albeit sometimes to modest degree, there being need to continue to exercise associated due care in SRS planning and delivery.