Dosimetric verification of radiotherapy treatment planning system at TMSS Cancer Center, Bogura, Bangladesh

Abstract

Authentication of TPS is the component of the QA program for RTPS and planning process. So, verification of dose calculation algorithm is essential to measure the efficiency of the dose calculations. The goal is to assess how far the dosage measured deviates from the dose predicted by the treatment planning system (TPS) algorithm using a CIRS Thorax phantom. It has been done to measure the dosimetric variations of 6MV, 10MV and 15MV photon beams. The phantom was initially scanned using a CT-simulator, and the raw data from the gated scans were then exported to TPS to perform the planning. Using this planning, the phantom was irradiated for four different cases. The computed dose was then compared with the measured dose to ensure TPS validity. The findings demonstrate that the variation between the measured doses in altered holes of the CIRS thorax phantom and the calculated doses by TPS was within the allowed limit except few points of four cases. Max. and Min. deviations for 6MV were 3.87% and 0.05% respectively. On the other hand, Max. and Min. deviations for 10MV were 7.87% and 0.12% respectively and that for 15MV are 4.44% and 0.02% respectively. Satisfactory results were obtained for lung and bone substitute. The results demonstrate the accuracy of the doses determined by the treatment planning system algorithm using a thorax phantom, and they also demonstrate the competency of using the phantom for regular verification. In case of external beam radiation therapy with AAA algorithm, the CIRS Thorax Phantom is suitable for dose computation in heterogeneous medium. However it is more compatible for 6MV than 10MV and 15MV.