瓦里安加速器静态调强放疗剂量分布与剂量率关系的评价  

The relation of the dose distributions with the dose rates in static intensity modulated radiotherapy using Varian＇s linear accelarator

作　　者：李亮[1] 戴建荣[2] 江波[2] 马攀[2] 

机构地区：[1]武汉大学物理科学与技术学院放射医学物理专业,武汉430072 [2]中国医学科学院北京协和医学院肿瘤医院肿瘤研究所放疗科

出　　处：《中华放射肿瘤学杂志》2010年第3期268-272,共5页Chinese Journal of Radiation Oncology

摘　　要：目的 评价静态多叶准直器调强放疗剂量分布与剂量率的关系,为特定患者治疗时如何选择剂量率提供参考.方法 选取静态多叶准直器调强放疗（IMRT）的3例（前列腺癌、鼻咽癌和淋巴瘤）典型治疗计划,分别使用瓦里安600CD加速器和I＇mRT Matrixx二维电离室阵列,在不同剂量率（100、300、600 MU/min）下比较验证通过率.在Pinnacle计划系统中把每例子野单独作为1个射野,形成CRT计划.使用OmniPro-I＇mRT V1.6调强验证软件把每例计划测最数据中每个子野,与同一剂量率下的CRT计划测量数据进行对比;得到实际治疗中每个子野在射野中的权重,再导回计划系统得到不同剂量率下的模拟计划.采用剂量分布和剂量体积直方图评价模拟计划与原计划对靶区和正常组织照射剂量情况.结果 随剂量率增加调强验证通过率下降.3例病例模拟计划靶区的Dmax、D（main）、Dmean、D95够均变大,靶区内高剂量区明显增加,95%等剂量线外扩.600 MU/min模拟计划中,鼻咽癌病例中GTVnd的D95比原计划增加5.33%,其V10达到19.38%.危及器官受量同样增加.淋巴瘤病例中全肺V20在原计划与模拟计划（100、300、600 MU/min）中依次为31.77%与32.11%、32.60%、33.26%,鼻咽癌病例中右腮腺V30依次为48.75%与49.56%、51.65%、53.91%.结论 高剂量率下进行静态多叶准直器IMRT实际得到的剂量分布将偏离计划分布,靶区高剂量区和危及器官受量将增加.当原计划中危及器官受量与耐受量接近时,不宜使用高剂量率进行IMRT.Objective To evaluate the dose distributions with different dose rates, and approach a reference to the dose rate for radiation. Methods Three classic static intensity modulated radiotherapy （IMRT） plans of prostate cancer, lymphoma and nasopharyngeal carcinoma were chosen for the study. For each plan, the dose verification of three different dose rates （ 100, 300 and 600 MU/min） was performed with the Varian 600CD linear accelarator by using the 2-DICA of I＇mRT Matrixx. With the Pinncale planning system, each segment was used as a beam to form another IMRT plan. The OmniPro-I＇mRT V1.6 was applied to compare the segments in the two IMRT plans, and then the actual weights were obtained. The simulated plans at different dose rate were designed when setting the weights back into the planning system. Results With the increase of dose rate, the passing ratio of the verification decreased and the Dmax, Dmin,D and Dgs of the planning tumor volume increased. The high dose area expanded significantly in target regions, and the 95% isodose line extended. At the dose rate of 600 MU/min, The D95 of CTVnd in nasopharyngeal carcinoma increased by 5.33% than the original plan with the Vllo up to 19. 38%. The irradiation dose of the organs at risk （OARs） increased. For the case of lymphoma, the V20 of the lungs in the original plan and the three simulated plans were 31.77%, 32. 11%, 32.60% and 33.26%, respectively. For the case of nasopharyngeal carcinoma, the V30 of the right parotid were 48.75%, 49.56%, 51.65% and 53.91%, respectively. Conclusions With the increase of dose rate in static IMRT , the actual dose distribution deviates the original plan , and the high dose area and the OARs dose increases. The higher dose rate is suboptimal when the dose of the OARs is proximate to the tolerance limit.

关 键 词：调强放疗 剂量率 二维电离室矩阵 剂量分布 

分 类 号：R686[医药卫生—骨科学]