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目的 通过一系列调强验证方法的研究 ,探讨逆向计划调强适形放射治疗 (IMRT)的质量保证方法是否可行。方法 用VarianCadplan三维治疗计划系统中Helios逆向计划系统对前列腺癌、鼻咽癌、脑瘤、胰腺癌、椎骨转移癌等设计并进行IMRT。为验证计划系统生成的各个照射野注量图与实际注量图的一致性 ,将剂量胶片放在平板有机玻璃体模下 ,使计划中的各个照射野始终垂直于体模表面 ;调用患者治疗数据分别单独照射 ,冲洗胶片后与计划得出的注量图进行比较。将剂量胶片夹在仿真体模适当的部位 ,调用患者治疗数据对体模进行模拟照射 ,由此得出轴向截面上的等剂量分布 ,与计划的等剂量曲线拟合比对。用电离室和水箱验证等中心和偏离点的绝对剂量。在模拟机或加速器上拍正侧位照射野验证片 ,与CT模拟数字重建的射线影像片比较 ,验证等中心位置。结果 各射线束轴垂直方向测得的注量图与计划系统计算的一致 ;等中心点绝对剂量测量的结果与计划计算的误差在 3%以内 ,偏离点绝对剂量误差较大 ;轴向截面等剂量曲线分布的胶片测量结果与计划计算的很接近 ;等中心位置误差在 3mm以内。结论 近一年的实践证明在IMRT中所采用的上述质量保证措施是切实可行的
Objective To investigate the feasibility of quality assurance of reverse-planted IMRT through a series of studies on intensity-modulated verification. Methods Helios reverse planning system in VarianCadplan three-dimensional treatment planning system was designed and performed for IMRT in prostate cancer, nasopharyngeal carcinoma, brain tumor, pancreatic cancer, vertebral metastasis and so on. In order to verify the consistency of the various irradiation field maps generated by the planning system with the actual fluence map, the dose film is placed on the slab plexiglass body so that the planned irradiation fields are always perpendicular to the phantom surface; the patient treatment data is invoked After irradiation, the film was processed and compared with the planned fluence map. The dose film is sandwiched in the appropriate part of the simulation phantom, the patient treatment data is called to simulate the phantom irradiation, and an equal dose distribution in the axial section is obtained, which is matched with the planned isodose curve fitting. Use ionization chambers and water tanks to verify centers and deviations from the absolute dose. On the simulator or accelerator, shoot the lateral radiographs and verify the isocenter compared with the radiographs reconstructed by CT simulation. Results The fluence measured in the vertical direction of each beam axis was consistent with that calculated by the planning system. The error between the absolute dose measurement at the isocenter and the planned calculation was within 3%, and the error of the absolute dose at the deviation point was large. The axial section Dose curve distribution of the film measurement results are very close to the calculated plan; the center position error within 3mm. Conclusions Nearly a year of practice has proved that the quality assurance measures adopted in IMRT are feasible