PhDRadiotherapy involves the treatment of tumours with ionising radiation. Technological advances have improved the ability to conform dose distributions to tumours in three dimensions (3D) and thereby reduce morbidity. However, sophisticated measurement devices are required to verify these complex distributions and ensure their accuracy. Radiation-sensitive gels, including polymer and Fricke gels, are a potential solution to this 3D dosimetry problem. Scanning these detectors using imaging methods such as magnetic resonance imaging (MRI) provides quantifiable images of dose distribution. Despite research efforts, 3D gel dosimetry has not yet been implemented as a routine dosimetry tool in clinical radiotherapy. This thesis aims to investigate the implementation of Fricke gel detectors within a clinical radiotherapy department. The existing literature was reviewed to establish what evidence already existed on the dosimetric accuracy of Fricke gel detectors. This review highlighted gaps for many important dosimetric characteristics and a lack of a systematic approach to the testing of these detectors. Basic dosimetric characteristics were then investigated using test tube Fricke gel samples and an MR spectrometer. These experiments showed an excellent basic precision over a dose range of 3 to 20Gy. However, detectors need to be scanned within a certain time of irradiation to avoid signal drift. There was no evidence of any dependence of response on dose rate, energy or fractionation. Larger volume detector samples were analysed using a 3T MRI scanner. Detector response was homogeneous and did not vary with volume. Post-irradiation blurring of the measured distribution due to ferric ion diffusion was within acceptable limits if detectors were scanned within 2 hours following irradiation for typical clinical dose gradients. Finally, large volume Fricke gel detectors were used to measure complex VMAT stereotactic plans, describing the integrated dose distribution with sufficient accuracy and demonstrating clear potential to be applied to our clinical practice.Barts Charity grant reference 691-1003; Translating Polymer Gel Dosimetry Research into Clinical Routine Use in Radiotherap
