Enhancement of the UK primary standard for absorbed dose for proton radiotherapy

With the implementation of proton beam therapy; modern radiotherapy treatments have better outcomes than ever before. Likewise, the development of spatially fractionated radiotherapy treatments have shown tremendous potential in pre-clinical studies for improving patient outcomes. Both of these implementation come at the cost of increasing complexity, providing a greater challenge for both routine quality assurance and primary standard dosimetry. Simultaneously, recent advances in the field of silicon radiation detectors offer a possible solution for high resolution real-time monitoring would would increase confidence in the dosimetry. This thesis describes the application of Silicon Strip Detectors (SSD) and Complementary Metal-Oxide Semiconductor (CMOS) devices to X-ray and Proton beam therapies with the intention to develop new methods of quality assurance and a combined system using the NPL Graphite Calorimeter for proton radiotherapy. A combined system using a large-format CMOS is tested in 6 MV X-ray beams at the NPL, verifying the concept and providing a proof of principle. \ud These measurements produced some unexpected results, which required the development of a model of the Calorimeter in COMSOL, a finite-element simulation software package, to study and better understand the internal heat flow. The developed model can use parameterised beam data acquired by an independent silicon detector (whether CMOS or SSD detectors) as a heat source for coupled simulations of delivered beams. After validating against experimental results, the model was subjected to fields of radiation representative of Pencil beam scanning (PBS), providing confidence in the effectiveness of the NPL Graphite Calorimeter in these radiation beams