Sci-Thur PM Therapy-03: Automated Monte Carlo Simulation and Validation of an External Beam Radiotherapy Treatment Plan

Abstract

We present the implementation of an integrated EGSnrc‐based Monte Carlo(MC) system as a tool for the verification of Varian's Eclipse clinical external beam radiotherapytreatment planning system (TPS). Once a TPS plan is generated an automated and fully integrated MC simulation is performed based on the information contained in the DICOM RT Plan, RT Sset, RT Dose and CTimage set. MC simulation parameters are determined from information extracted from the RT Plan. The CTimage set is then used to generate a virtual phantom in a manner analogous to that of CTcreate (the relevant EGSnrc program), but with the added advantage of incorporating the structures in RT Sset for volume definition within the phantom. The MC simulation is broken into stages that progress from the target in the head of the accelerator, through the various stages of collimation, and into the phantom using both BEAMnrc and DOSXYZnrc on a dedicated cluster. Using RT Dose, we are then able to compare absolute dose differences between the approaches quantitatively in 3D using a χ metric. To illustrate the process, we compare dose distributions for an unblocked four field pelvic treatment generated both using Eclipse and the MC system. Significant differences (> 4%) between the MC and TPS dose matrixes are observed in the vicinity of the bony anatomy.