Modelling and development of tissue-equivalent dosimeters for small field radiotherapy
A radiotherapy treatment is a clinical treatment which makes use of ionizing radiation to treat cancerous diseases. However, the ionizing radiation interacting within the cells can lead to DNA damage in both the cancerous and normal tissues. Therefore the exact knowledge of the dose delivered to the...
| Main Author: | |
|---|---|
| Published: |
Swansea University
2013
|
| Subjects: | |
| Online Access: | https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678604 |
| Summary: | A radiotherapy treatment is a clinical treatment which makes use of ionizing radiation to treat cancerous diseases. However, the ionizing radiation interacting within the cells can lead to DNA damage in both the cancerous and normal tissues. Therefore the exact knowledge of the dose delivered to the patient is essential because it greatly affects the effectiveness of the treatment. Dosimetry is usually performed by air ionization chambers however their use in the dosimetry of small photon beams is limited by their large sensitive volume. The ideal detector has a small, water-equivalent sensitive volume but the design of the detector and the presence of the encapsulation materials placed in close proximity to the sensitive volume can cause perturbations to the radiation fluence. The Monte Carlo method is the ideal tool because it allows a detailed investigation of the perturbation effects of each detector component but a Monte Carlo model often requires detailed information of the device which can be difficult to access. In this study, an experimental approach involving the use of CT scans and fluorescence spectroscopy in the measurements of the physical properties of a liquid ion chamber was explored. The performance of eight single crystal CVD diamond detectors in the dosimetry of photon beams was also assessed. One of the drawbacks of diamond detectors is the dose rate dependence. The evaluation of the dose rate dependence using clinical photon beams is controversial because the dose rate can be varied by either changing the source to detector distance or the Pulse Repetition Frequency of the LINAC machine. A simple analytical model of the charge collection dynamics was written in the Matlab code to understand the effects introduced by a pulsed radiation beam. The outcome of this study correlates the PRF dependence with the presence of deeper traps. |
|---|