质子治疗计划系统CT建模的校准

The calibration of CT modeling for proton therapy treatment planning system

目的:在RayStation质子治疗计划系统(TPS)中为三台CT设备进行建模,验证并校准CT建模曲线。方法:使用CT设备扫描模体得到不同组织替代材料的CT值,建立CT值与质量密度(CT-MD)曲线。同时,根据各种人体组织的化学成分,计算得到CT值与阻止本领(CT-SP)曲线。在TPS中使用不同CT建模曲线计算组织替代模块的等效水厚度;利用布拉格峰测量设备测得各模块实际等效水厚度,与TPS计算值进行比较,验证不同CT建模的精度。结果:不同管电压扫描条件下,CT建模曲线差异有统计学意义。基于化学成分校准的CT-SP曲线与CT-MD曲线比较更适合质子剂量计算,但对高CT值对应的阻止本领值仍需进行修正,校准后的计算误差在3%以内。结论:本文阐述的在质子TPS中验证并校准CT值曲线的方法,证明了化学成分计量校准后的CT-SP曲线更适用于质子剂量计算。

ObjectiveTo verify and calibrate the CT modeling curves of three CT devices in RayStation proton treatment planning system(TPS).MethodsCT-mass density(CT-MD)curves were established by CT Hounsfield units of different tissue substitute materials obtained by scanning the model with CT equipment.CT-stopping power(CT-SP)curves were established by calculation based on the chemical composition of various human tissues.The equivalent water thickness of tissue substitute modules was calculated with different CT modeling curves in TPS.The actual equivalent water thickness of various modules was measured by a Bragg peak detector,and compared with the calculated values of TPS to verify the accuracy of different CT models.ResultsThe differences of CT modeling curves were significantly different under different tube voltage scanning protocols.Compared with CT-MD curves,CT-SP curves based on the stoichiometric calibration were more suitable for proton dose calculation.However,the values of stopping power corresponding to high CT values still needed to be optimized,and the calculation error after calibration was less than 3%.ConclusionThe method of verifying and calibrating CT unit curves of proton TPS is described,proving that the CT-SP curves after stoichiometric calculation are more suitable for proton dose calculation.