Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
Phys Med Biol. 2011 Jul 21;56(14):4415-31. doi: 10.1088/0031-9155/56/14/012. Epub 2011 Jun 27.
Clinically relevant intensity modulated proton therapy (IMPT) treatment plans were measured in a newly developed anthropomorphic phantom (i) to assess plan accuracy in the presence of high heterogeneity and (ii) to measure plan robustness in the case of treatment uncertainties (range and spatial). The new phantom consists of five different tissue substitute materials simulating different tissue types and was cut into sagittal planes so as to facilitate the verification of co-planar proton fields. GafChromic films were positioned in the different planes of the phantom, and 3D-IMPT and distal edge tracking (DET) plans were delivered to a volume simulating a skull base chordoma. In addition, treatments planned on CTs of the phantom with HU units modified were delivered to simulate systematic range uncertainties (range-error treatments). Finally, plans were delivered with the phantom rotated to simulate spatial errors. Results show excellent agreement between the calculated and the measured dose distribution: >99% and 98% of points with a gamma value <1 (3%/3 mm) for the 3D-IMPT and the DET plan, respectively. For both range and spatial errors, the 3D-IMPT plan was more robust than the DET plan. Both plans were more robust to range than to the spatial uncertainties. Finally, for range error treatments, measured distributions were compared to a model for predicting delivery errors in the treatment planning system. Good agreement has been found between the model and the measurements for both types of IMPT plan.
我们在一个新开发的人体模型（i）中测量了具有临床相关性的强度调制质子治疗（IMPT）计划，以评估在存在高异质性的情况下计划的准确性，以及在治疗不确定性（范围和空间）的情况下测量计划的稳健性。新的人体模型由五种不同的组织替代材料组成，模拟不同的组织类型，并被切割成矢状面，以便于共面质子场的验证。GafChromic 胶片被放置在人体模型的不同平面中，并且将 3D-IMPT 和远端边缘跟踪（DET）计划递送到模拟颅底脊索瘤的体积。此外，还使用 CT 对人体模型的 HU 单位进行了修改，以模拟系统范围不确定性（范围误差治疗）来规划治疗。最后，将人体模型旋转以模拟空间误差来交付计划。结果表明，计算剂量分布与测量剂量分布之间具有极好的一致性：3D-IMPT 和 DET 计划的伽马值<1（3%/3mm）的点分别超过 99%和 98%。对于范围和空间误差，3D-IMPT 计划比 DET 计划更稳健。两种计划对范围误差的稳健性都比对空间不确定性的稳健性更强。最后，对于范围误差治疗，测量的分布与用于预测治疗计划系统中输送误差的模型进行了比较。对于两种类型的 IMPT 计划，模型与测量之间都存在很好的一致性。
