A preliminary study on modeling and commissioning method of the treatment planning system used in the first domestic proton therapy device / 中华放射医学与防护杂志

ABSTRACT

Objective:To introduce the method and result of the modeling and preliminary dose verification of the treatment planning system used in the first domestic proton therapy device of China (Raystation 10B, a system of scientific research version with no available registration certificate) and to verify the modeling accuracy using dose verification result.Methods:The modeling method for a treatment planning system (TPS) mainly included the data acquisition and modeling of integrated depth dose (IDD) curves, the data acquisition and modeling of beam spot profiles in air, and the calibration and modeling of absolute dose by scanning a 10 cm ×10 cm square field with a spot spacing of 2.5 mm. By measuring the dose distributions in three cases with different complexity levels and comparing them with the dose distributions calculated using the TPS, this study verified and analyzed the modeling accuracy and proposed the requirements for beam parameters and the commissioning suggestions of the proton device.Results:The peak values of the IDD curves of low-energy regions fitted using the TPS model were less than the measured values, while those of medium- and high-energy regions fitted using the TPS model approximated the measured values. The range in all energy regions fitted accurately. For the three cases with different complexity levels, the deviation between the average dose calculated by the TPS and that measured was within ±5% (national standard for type tests of medical devices). Moreover, the DTA of high-dose-gradient areas was less than 3 mm.Conclusions:The modeling accuracy of the TPS generally meets the verification requirements. However, due to the low resolution of IDDs obtained by Monte Carlo simulation in the TPS model and the sharp Bragg peaks of low-energy regions, the IDD modeling accuracy of low-energy regions is insufficient.