SU‐E‐T‐32: The Use of Monte Carlo Method as an Independent Dose Verification Calculation Tool for TomoTherapy

Purpose: It has been widely recognized, as stated in a ICRP 2009 report, that a secondary calculation, independent from treatment‐planning‐system (TPS), has proven to be an efficient tool for prevention of major errors in dose delivery. The purpose of this study is to develop such tool for TomoTherapy system. Methods: A Monte Carlo tool that has been validated previously, TomoPen, was modified to have better integration with the TomoTherapy software. Patient plan and CT information is DICOM exported. The Monte Carlo tool reads the plan and CT information from the dicom file and computes the dose. The Monte Carlo computed dose is compared with the TPS dose to make sure no major deviation is observed. Results: The tool has been tested on several clinical patient plans. By using a coarse dose grid, a decent dose distribution can be obtained in less than an hour on an Intel i7 CPU. The run time can be further reduced by using a computer cluster. The time takes for this secondary calculation is comparable with the standard DQA plan creation and measurement. However, the secondary calculation does not take the treatment machine time as well as physicist's time. Conclusions: A Monte Carlo based secondary calculation tool is developed to prevent major errors in TomoTherapy delivery. It is shown that it can be fitted into the current clinical workflow.