The use of diagnostic imaging services has been increasing significantly over recent decades as the availability and the sophistication of diagnostic imaging equipment has expanded. This has resulted in improved patient outcome through earlier and more accurate diagnoses at cost of increasing radiation exposure to the general populace. This may result in an increased incidence of radiation-induced conditions and cancer. Monitoring the radiation exposures during these procedures is crucial to preventing ra-diation induced conditions and minimising radiation exposure both to patients and to operators of radiation imaging technologies where possible. This thesis investigated the applications of the MOSkin dosimeter, in clinical diagnostic procedures. The MOSkin provides advantages over traditional dosimetry solutions by providing minimal beam perturbation, the ability to measure doses in real-time, exhibiting radio-transparency in images acquired by diagnostic beam qualities and by allowi
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Abstract
Purpose. To compare the accuracies of the AAA and AcurosXB dose calculation algorithms and to predict the change in the down-stream and lateral dose deposition of high energy photons in the presence of material with densities higher that commonly found in the body. Method. Metal rods of titanium (d=4.5 g cm-3), stainless steel (d = 8 g cm-3) and tungsten (d = 19.25 g cm-3) were positioned in a phantom. Film was position behind and laterally to the rods to measure the dose distribution for a 6 MV, 18MVand 10 FFF photon beams. A DOSXYZnrc Monte Carlo simulation of the experimental setup was performed. The AAA and AcurosXB dose calculation algorithms were used to predict the dose distributions. The dose from film and DOSXYZnrc were compared with the dose predicted by AAA and AcurosXB. Results. AAA overestimated the dose behind the rods by 15%- 25% and underestimated the dose laterally to the rods by5%-15% depending on the range of materials and energies investigated. AcurosXB
Abstract
Plastic scintillation dosimeters (PSDs) have many properties that make them desirable for relative dosimetry with MRI-LINACs. An in-house PSD, Farmer ionisation chamber and Gafchromic EBT3 film were used to measure central axis percentage depth dose distributions (PDDs) at the Australian MRI-LINAC Mean errors were calculated between each detector s responses, where the in-house PSD was on average within 0.7% of the Farmer chamber and 1.4% of film, while the Farmer chamber and film were on average within 1.1% of each other. However, the PSD systematically over-estimated the dose as depth increased, approaching a maximum overestimation of the order of 3.5% for the smallest field size measured. This trend was statistically insignificant for all other field sizes measured; further investigation is required to determine the source of this effect. The calculated values of mean absolute error are comparable to the those of trusted dosimeters reported in the literature. These mean
Abstract
Microbeam radiation therapy (MRT) is a developing radiotherapy, based on the use of beams only a few tens of micrometres wide, generated by synchrotron X-ray sources. The spatial fractionation of the homogeneous beam into an array of microbeams is possible using a multislit collimator (MSC), i.e. a machined metal block with regular apertures. Dosimetry in MRT is challenging and previous works still show differences between calculated and experimental dose profiles of 10-30%, which are not acceptable for a clinical implementation of treatment. The interaction of the X-rays with the MSC may contribute to the observed discrepancies; the present study therefore investigates the dose contribution due to radiation interaction with the MSC inner walls and radiation leakage of the MSC. Dose distributions inside a water-equivalent phantom were evaluated for different field sizes and three typical spectra used for MRT studies at the European Synchrotron Biomedical beamline ID17. Film