TLD质量核查调强放射治疗非均匀野剂量方法

TLD Quality Audit Method for Intensity Modulated Radiotherapy in the Presence of Heterogeneities

目的 核查放射治疗计划系统（TPS）计算病人治疗剂量的非均匀野剂量校正。方法 将插有TLD的聚苯乙烯固体模体,聚苯乙烯/肺固体模体,聚苯乙烯/骨固体模体分别经CT扫描,影像分别传入TPS并计算高能X射线下监督单位数,使传递给中心束轴TLD剂量为2 Gy。在高能X射线下完成TLD照射,照射后的TLD经测量、剂量计算,D（TLD）与D（TPS）剂量比值在0.95～1.05范围为可接受范围。结果 核查结果表明,光子线束均匀模体轴上（P）剂量和非均匀骨模体轴上（BP）剂量核查结果较好。非均匀肺模体轴上（LP）和离轴（LL）剂量核查结果误差很大。结论 光子线束非均匀性剂量校正在放射治疗中是非常重要,尤其是肺组织。校正不当,对于肺组织剂量误差也可达到11.1%,离轴情况下更多达18.4%。对于骨组织剂量误差较小。

Objective To check the heterogeneity corrected dose calculations performed by the treatment planning system. Methods Homogeneous polystyrene solid phantom with TLD,Polystyrene/lung solid phantom with TLD and Polystyrene/bone solid phantom with TLD will be required to be CT scanned respectively, images exported to the TPS and monitor units calculat- ed as if to deliver 2Gy to the TLD on photon beam axis. The TLDs was irradiated by high energy X - ray. TLDs irradiated by measuring and dose calculation, and D（TLD）/D（TPS） dose ratio in 0.95 to 1.05 was acceptable. Results Verification re- sults showed that homogeneous polystyrene solid phantom on axis （P） dose and polystyrene/bone solid phantom on axis （BP） dose are good ,polystyrene/lung solid phantom on axis （LP） and off- axis （LL） relative deviation are large. Conclusion Heterogeneity of photon beam close correction is very important in radiotherapy, especially in the lung tissue. Improper correc- tion, the deviation for lung tissue can also be reached 11.1% , off- axis cases up to 18.4%. The deviation for bone tissue is smaller.