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目的比较二弧旋转容积调强(volumetric modulated arc therapy,VMAT)与固定7野动态调强(dynamic intensity modulated radiotherapy,dIMRT)在宫颈癌放疗计划中的剂量学差异,寻找宫颈癌放疗的最佳计划方案。方法 10例宫颈癌患者利用VARIAN计划系统(Eclipse 8.6)分别制定二弧VMAT和7野dIMRT放疗计划。比较两种计划中靶区、射野内正常组织以及危及器官的剂量学差异和执行两种计划所需的机器条数(MU)、照射时间及计划制定优化时间的差别。结果与7野dIMRT相比,二弧VMAT靶区适合度指数(CI)更接近1(P<0.05)、靶区剂量均匀性指数(HI)无显著差异;D100%显著大于7野dIMRT放疗计划,且D min更接近处方剂量,差异均有统计学意义(P<0.05)。在二弧VMAT计划中股骨头的D mean显著低于7野dIMRT计划(P<0.05),而D5%两者接近。在小肠、膀胱、直肠和马尾的保护上二弧VMAT较7野dIMRT无明显优势,但仍能很好地达到临床要求。二弧VMAT总MU为7野dIMRT的1/4,治疗时间减少2/3。结论二弧VMAT计划可以达到或优于7野dIMRT计划的靶区剂量分布,能更好地降低部分危及器官的受照剂量,使正常组织内高剂量区(20~30 Gy)体积明显减少,并且具有相对减少总MU、总治疗时间的优势,是宫颈癌放射治疗计划的较好选择之一。
Objective To compare the dosimetry differences between volumetric modulated arc therapy (VMAT) and dynamic intensity modulated radiotherapy (dIMRT) in the planning of cervical cancer radiotherapy and to find out the optimal radiotherapy for cervical cancer Program. Methods Ten patients with cervical cancer using VARIAN planning system (Eclipse 8.6) to develop two arc VMAT and seven wild dIMRT radiotherapy plans. Differences in dosimetry between the two planned target zones, normal field tissues, and endangered organs were compared with the number of machines (MU) required to perform the two schedules, the exposure time and the planned optimization time. Results Compared with the 7-filed dIMRT, the fitness index of the second-order VMAT target area was closer to 1 (P <0.05) and the dose uniformity index (HI) of the target area was not significantly different; D100% was significantly greater than that of the 7-day dIMRT radiotherapy plan , And D min closer to the prescription dose, the difference was statistically significant (P <0.05). D mean of the femoral head in the second-arc VMAT program was significantly lower than in the 7-field dIMRT plan (P <0.05), while D5% was close to both. In the protection of the small intestine, bladder, rectum and cauda equina, the two-arc VMAT has no obvious advantage over the 7-filed dIMRT, but still meets the clinical requirements well. The second-arc VMAT total MU was 1/4 of the 7-field dIMRT and the treatment time was reduced by 2/3. Conclusion The second-arc VMAT scheme can achieve or exceed the target dose distribution in the 7-field dIMRT plan, and can reduce the doses of partially-endangerd organs and significantly reduce the volume of high-dose areas (20-30 Gy) in normal tissues. And has the relative reduction of total MU, the total treatment time advantages, is one of the better options for cervical cancer radiotherapy plan.