Study of 1-D and 3-D Detectors for Application in Radiation Therapy.

This work encompasses dosimetric studies of Ge-doped SiO2 telecommunication fibre as a 1-D thermoluminescence (TL) system and the radiochromic plastic material PRESAGE™ as a 3-D dosimetric system, both for therapeutic applications. The therapy modalities used are a mercury arc lamp, a synchrotron microbeam facility, a superficial X-ray beam therapy facility and an electron linear accelerator, covering the energy range from a few eV to several MeV. The irradiations made included ultraviolet (UV) exposure at a power output of 9. 85 - 10. 50 mW cm-2, 90 kVp X-ray exposure delivered by a superficial X-ray unit, synchrotron radiation delivered at a mean energy of 109 keV and electron and photon beam irradiations delivered by an electron linac (9 - 20 MeV for electrons and accelerating potentials of 6 - 15 MV for photons). Both dosimeters have been characterised. The dosimetric characteristics of commercially available Ge-doped SiO2 optical fibre investigated includes, reproducibility, fading, dose response, reciprocity between TL yield and dose-rate and energy dependence. For 3-D PRESAGE™ radiochromic plastic material, the characteristics investigated are attenuation, dose linearity and reproducibility. Building upon these characterisations, the dosimeters were subsequently used in various dosimetry applications. Firstly, the fibers were used to measure UV radiation for PUVA dosimetry. The fibre was also used to measure photoelectron enhancement from iodinated contrast media as might be applied in radiation synovectomy. Another study looked into creation of test objects using PRESAGE for quality assurance of the associated Optical CT scanner. The test objects were created using UV radiation and synchrotron X-ray microbeam to measure the scanner spatial resolution and geometrical distortion. Finally, to illustrate the potential of PRESAGE for use in Microbeam Radiation Therapy (MRT) dosimetry, development of a micro Optical CT scanner has been made. The capability of the scanner for imaging micron spatial resolution has been performed, evaluating the peak-to-valley dose ratio (PVDR) and verifying cross-firing irradiation applied in MRT treatment