Development Of RBM Dose Engine For Accurate Radiotherapy Planning System

Radiotherapy is one of the most important means to treat tumours. Treatment Planning System (TPS) is a software tool, with which radiotherapy doctors and radiotherapy physicists can design and optimize the treatment plan before dose delivery. Now both the routine and inverse planning systems need fast and accurate dose calculation tools. The aim of this work is to improve the performance of the Regular Beam Model (RBM) method to meet the clinical requirement.RBM (Regular Beam Model) dose engine is a kind of analytical method based on the measured database, which can calculate the dose distribution of the 3-D water box. With the Batho inhomogeneity correction, RBM can be used to evaluate the dose distribution of the patient based on the medical images like CT images.In this work, the RBM dose engine is programmed with the Batho and the Modified Batho inhomogeneity correction methods, respectively. In the pure water and water-lung-water examples, the above two engines are tested and compared with the result of the EGS4 code. In addition, a mixed Batho correction scheme is proposed and implemented in the RBM program. The test results demonstrate that this engine can improve the precision without increasement of the calculation time. Because the mixed Batho based RBM can calculate the dose distribution with high speed and accuracy, and can satisfy the clinical requirement for velocity and precision, it can be used as a reliable dose calculation tool for clinical utilization.In addition, the results show that in the area which is near to large inhomogeneity and air region, considerable discrepancy appears. In the future work, the coupling method of RBM and Monte-Carlo will be investigated to handle this problem.