علوم - دكتوراة
Permanent URI for this collectionhttps://repository.neelain.edu.sd/handle/123456789/511
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Item EPID BASED INVIVO TREATMENT VERIFICATION for ADVANCED RADIOTHERAPY TECHNIQUES(Al Neelain University, 2016) Ali Sid Ahmed Mohammed AliRadiotherapy is an essential method for the treatment of cancer diseases, it can be used alone to destroy the cancer cells, also it can be used as a combination with other treatment modalities to shrink the tumor volume. The key factor for successful radiotherapy treatment is the accuracy in localizing the tumor cells and delivering the dose to the patient (treatment verification). Inaccurate radiation treatment might cause severe side effects because radiation damages the tumor cells, as well as the healthy normal cells. However, with the improvement of technologies, targeting the tumor became possible. This thesis concerns with improvements to in-vivo treatment verification for intensity modulation radiation therapy. The treatment verification model is basically based on the electronic portal imaging device, and mainly compares the measured portal dose image to the predicted one. For the improvement of the model, first an experimental method was used to model the treatment couch, and afterwards it was included in the portal dose image prediction; this couch model compensates the beam attenuation by the treatment couch in the measured portal dose image. The model was verified using phantom measurements for different gantry angles, in addition to in-vivo clinical validation using head and neck and prostate cancer patients. In the second part of this thesis, the influence of the changing in patient anatomy during the radiotherapy treatment course was investigated. It was hypothesized that an in-room acquired cone beam CT would better represent the patient’s anatomy during acquisition of the Electronic Portal Imaging Device (EPID) images than the planning CT would do, therefore, the kilovoltage cone-beam CT scan (CBCT), acquired during the same day of the fraction, was used to calculate the portal dose image prediction instead of the planning CT. For evaluation purposes, predictions were also calculated using the patients’ planning CT. The method was verified firstly using phantom measurements with different fields, then for 50 prostate cancer patients, 5 fractions each, measured portal dose images were compared to the predicted ones using predictions based on the planning CT, and compared to the predictions based on the cone beam CT. The results of the treatment couch model showed improvements in the agreement between measured and predicted portal dose images, especially when the beam was passing through the holder of the treatment couch. The results of using the CBCT instead of the planning CT for portal dose image predictions showed a better agreement when the cone beam CT was used instead of the planning CT. However, for some patient’s fractions VI still some deviations were observed, due to the fact that using the cone beam CT resolves the problem of intra-fraction anatomy changes. To solve the problem of inter-fraction anatomy changes, it was investigated whether combining in-vivo measurements performed in the first 1–5 fractions could enhance agreement between measurements and predictions, comparable to pre-treatment verification.