调强适形放射治疗计划剂量学的验证

目的探讨逆向调强适形放射治疗(IMRT)过程中剂量学验证的方法，保证IMRT治疗计划临床实施的正确性。方法针对实施IMRT病人，使用CMS FOCUS9200三维治疗计划系统设计出5野IMRT治疗计划。利用固体水模板在治疗计划系统中建立三维等效体模。将待验证病人的IMRT计划移置到体模中重新进行优化，计算出体模中感兴趣点或平面上的剂量和剂量分布。将体模移放到加速器治疗床上，调用体模IMRT计划数据对体模进行模拟照射。使用0．23 cc电离室测量出体模中感兴趣点上的吸收剂量；使用RIT 113胶片剂量分析系统测量出体模中感兴趣平面上的剂量分布。然后和计划系统计算的结果相比较，验证绝对剂量和相对剂量。结果绝对剂量和相对剂量的测量结果基本上和计划系统计算的结果相一致。测量的绝对剂量误差在3％以内，相对剂量曲线分布也是比较准确的。结论IMRT计划剂量学验证是临床实施IMRT治疗过程中的可靠保证。

Dosimetric verification of the intensity-modulated radiation therapy

Objective To discuss the methods of the dosimetric verification in the intensity modulated radiation therapy(IMRT) and insure correct execution of the IMRT planning in the clinical practice. Methods The CMS FOCUS9200 inverse planning system was used to provide optimized 5 field IMRT treatment plans for the patients. A phantom was made from true water equivalent material. The doses of the interesting points and isodose distributions of the interesting planes in the phantom were calculated using patients' treatment plan. The phantom was placed on the couch of the accelerator and was irradiated using the phantom's treatment planning data. The doses of interesting points were measured using a 0 23 cc chamber and the isodose distributions of interesting planes were measured using RIT 113 film dosimetry system in the phantom. The results were compared with those from calculation in planning system for verification. Results The doses and isodose distributions measured by the chamber and the film were consistent with those predicted by the planning. The error between the measured dose and calculated dose in the interesting points was less than 3%. Conclusion The dosimetric verification of IMRT is a reliable measure in the course of its implementation.