Viana Miranda Lima, T;
(2016)
Development and testing of a biologic dosimentric phantom for proton and ion beam therapy.
Doctoral thesis , UCL (University College London).
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Abstract
The development of clinical treatment protocols for particle therapy depends on the availability and quality of radiobiological data. Studying available commercial and in-house phantoms, showed that the current solutions either lack dosimetry or this dosimetry introduces uncertainties to the biological results. Therefore new radiobiological tools with improved dosimetry response were required. The chosen material, the effect of detectors uncertainties and the impact of detectors? positions were studied so the effect of the introduced uncertainties in the measurements could be evaluated. The phantom was subsequently tested at different experiments with both protons and carbon ion beams where a number of dose fields were simulated and delivered. Simulated and measured doses were compared to establish accuracy of simulation. Finally, a clonogenic survival assay was performed to assess the viability and capabilities of the phantom. No disturbance was introduced in the cell region by the detectors where 95.3% of the cases were within the 95% confidence level. Additionally, the detector measurements were free from any disturbance arising from the adjacent detectors (sigma 0.76). When evaluating the simulation accuracy, a good agreement was obtained between measurements and dose modelling where the average dose deviation was between 1.05% and 2.39%. Superior effectiveness was obtained for protons and carbon ions in respect to X-rays (1.2 and 2 times for protons and carbon ions respectively) and the phantom was able to correlate the cell survival and dose deposition. Concluding, these results showed that the phantom limitations were accounted for which enabled the measured physical dose and the dosimetry in the cell compartment to be correctly correlated. The results demonstrate the superior dosimetry obtained in respect to other set-ups either by correctly describing the dose profile (additional 1.5% mean deviation due to dose delivery uncertainties) or by not introducing uncertainties in the beam path (up to ± 2%).
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