胸中段食管癌共面不等分5野及铅门跟随调强放疗计划的剂量学研究

目的:比较4种调强放疗计划（IMRT）的剂量学差异，探讨不同布野方式和铅门跟随（JT）技术对胸中段食管癌靶区和危及器官的剂量影响。方法:选取10例鳞状细胞癌患者入组，并对每例患者设计4种放疗方案。3种铅门固定计划:IMRT1:0°、130°、160°、195°、220°，IMRT2:0°、130°、165°、200°、330°，IMRT3:0°、30°、130°、200°、330°；1种铅门跟随计划IMRT-JT:在IMRT2基础上使用铅门跟随技术对剂量重新计算评估。比较4种计划的靶区和危及器官的剂量体积参数、适形度指数（CI）、剂量均匀性指数（HI）及机器跳数（MU）。结果:4种计划的靶区剂量分布均达到临床处方的剂量要求。IMRT1、IMRT2、IMRT3计划比较，IMRT1、IMRT3计划PTV的CI略优于IMRT2计划；在心脏（V20、V30、V40、Dmean）剂量方面，IMRT1<0.05）；在脊髓（dmax、d1%）方面，imrt1><0.05）；imrt2计划可显著降低肺（v5、v20、dmean）剂量，但mu相较于其它计划有增加（p><0.05）。imrt2与imrt-jt相比，ptv的hi差异无统计学意义（p>0.05），但IMRT-JT的CI优于IMRT2计划（P<0.05）；IMRT-JT计划的肺（V5、V20、V30、Dmean）、心脏（V20、V30、V40、Dmean）、脊髓（Dmax、D1%、Dmean）均低于IMRT2计划的相应值（P<0.05）；IMRT-JT的MU相较于IMRT2计划有增加（P<0.05）。结论:IMRT1、IMRT2可分别降低心脏、肺的受量；而JT技术则可进一步降低危及器官的受量。

Dosimetric study on coplanar unequal 5-field versus jaw tracking intensity-modulated radiotherapy for middle thoracic esophageal cancer

Abstract: Objective To compare the dosimetric different of 4 different intensity-modulated radiotherapy (IMRT) plans, and to explore the dosimetric effects of different field arrangements and jaw tracking (JT) technique on target areas and organs-at-risk in radiotherapy for middle thoracic esophageal cancer. Methods Ten patients with squamous cell carcinoma were enrolled in the study. Four kinds of radiotherapy plans, including 3 static jaw plans and 1 JT plan, were designed for each patient. The static jaw plans included IMRT1 (0°, 130°, 160°, 195°, 220°), IMRT2 (0°, 130°, 165°, 200°, 330°) and IMRT3 (0°、30°、130°、200°、330°), and there was only 1 JT plan (IMRT-JT) in which the dose was recalculated and assessed by JT technique based on IMRT2. The dose-volume parameters of target areas and organs-at-risk, conformity index (CI), homogeneity index (HI) and monitor units (MU) were compared among 4 different plans. Results The target dose distribution in 4 plans all met the prescribed dose requirements. The comparison among IMRT1, IMRT2 and IMRT3 showed that the CI of PTV in IMRT1 and IMRT3 was slightly higher than that in IMRT2, and that the V20, V30, V40 and Dmean of the heart were highest in IMRT3, followed by IMRT2 and IMRT1 (P<0.05), and that the Dmax and D1% of spinal cord were highest in IMRT2, followed by IMRT3 and IMRT1 (P<0.05), and that compared with the other two plans, IMRT2 plan significantly reduced the V5, V20 and Dmean of lungs, but increased MU (P<0.05). There was no statistically significant difference in the HI of PTV between IMRT2 and IMRT-JT, but the CI of IMRT-JT was higher than that in IMRT2 (P<0.05). IMRT-JT was superior to IMRT2 in decreasing the dosimetric parameters of lungs (V5, V20, V30, Dmean), the heart (V20, V30, V40, Dmean), and spinal cord (Dmax, D1%, Dmean), but MU in IMRT-JT was increased as compared with that in IMRT2 (P<0.05). Conclusion Although IMRT1 and IMRT2 can decrease the doses to the heart and lungs, respectively, JT technique can further decrease the doses to organs-at-risk.