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Dr Abdulaziz Alanazi


Visiting Staff
+44 (0)1483 682722
20 BB 03

Academic and research departments

Department of Physics.

My publications

Publications

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.
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.