非均整与均整模式下宫颈癌容积旋转调强放疗计划的剂量学比较  

Dosimetric comparison of VMAT plans in different modes for cervical cancer: flatting filter free vs flattening filter

作　　者：王占宇[1] 谭军文 龙雨松[1] 贺先桃 韦婷[1] 李钢 

机构地区：[1]广西医科大学第四附属医院肿瘤科放疗室,广西柳州545005

出　　处：《中国医学物理学杂志》2017年第11期1110-1116,共7页Chinese Journal of Medical Physics

摘　　要：目的:容积旋转调强放疗(VMAT)是治疗宫颈癌的有效方法之一,通过比较宫颈癌非均整与均整模式下VMAT计划的剂量学特性,分析宫颈癌非均整模式下VMAT计划的临床可行性。方法:选取2016年1月~2017年3月期间的宫颈癌患者10例,分别对同一患者的CT图像及临床靶区,用相同的处方剂量50.4 Gy在Ray Station计划系统平台设计均为两个全弧的6 MV-X射线非均整模式(6FFF)和均整模式(6X)的VMAT计划,比较6FFF计划与6X计划的剂量学特性、剂量验证通过率、机器跳数和出束时间。结果:6X与6FFF两种VMAT计划所得PTV的最大剂量D2%,平均剂量D_(mean),最小剂量D_(98%),靶区覆盖率,靶区适形指数均相差不大(P>0.05);在危及器官保护上,6FFF计划中膀胱的V_(45)、平均剂量D_(mean)和小肠的V_(45)均低于6X计划;6FFF计划受到相应剂量照射的正常组织体积均小于6X计划;两种计划的剂量验证通过率均能满足治疗要求,其中6FFF计划验证通过率均值为(98.52±0.66)%,6X VMAT计划剂量验证通过率比6FFF计划略高;二者的机器跳数相比,6FFF计划平均机器跳数增加至6X计划的1.34倍(P=0.000),平均出束时间减少为6X计划出束时间的95.5%(P=0.012)。结论:6X计划和6FFF计划均能满足临床剂量学要求。在危及器官保护和正常组织低剂量照射方面,6FFF计划更具优势,有利于降低二次癌症的发生率,6FFF计划剂量验证通过率满足临床要求,二者在机器跳数和出束时间上,虽然6FFF的机器跳数增加,但出束时间反而下降,因此采用非均整模式并不会降低治疗效率。如何评估非均整模式下宫颈癌VMAT计划的临床效果,需进一步研究讨论。Objective To compare the dosimetric characteristics of flatting filter free （FFF） volumetric-modulated arc therapy （VMAT） plans and flattening filter VMAT plan for cervical cancer for analyzing the feasibility of VMAT plan in FFF mode for cervical cancer. Methods Ten patients with cervical cancer admitted between January 2016 and March 2017 were selected. Based on the CT image and clinical target areas of each patient, two plans with the same prescription dose of 50.4 Gy and the same parameters were designed in RayStation planning system, namely VMAT plan with 6 MV FFF X-ray （6FFF plan） and VMAT plan with 6 MV flattening filter X-ray （6X plan）. The dosimetric characteristics, dose passing rate, monitor unit and delivery time were compared between 6FFF plan and 6X plan. Results The differences between 6X plan and 6FFF plan in the maximum dose （D2%）, mean dose and minimum dose （D98%） of planning target volume, target coverage and conformity index of target areas were trivial （P〉0.05）. The V45 and Dmean of bladder and the V45 of small intestine were lower in 6FFF plan than in 6X plan. The irradiated volume of normal tissue in 6FFF plan was less than that in 6X plan. Both 6FFF plan and 6X plan met the requirements for dosimetric verification. The average gamma passing rate in 6FFF plan were （98.52±0.66）%, slightly lower than that in 6X plan. 6FFF plan increased the average monitor unit to 1.34 times of that in 6X plans （P=0.000）, but reduced the average delivery time to the 95.5% of that in 6X plan （P=0.012）. Conclusion Though both 6X plan and 6FFF plan meet the requirements for clinical dosimetric verification, 6FFF plan has more advantages in decreasing the dose to low dose area in normal tissue and protecting organs-at-risk, which can reduce the risk of cancer recurrence. The dosimetric verification also showed that 6FFF plan can achieve a gamma passing rate satisfying the clinical requirements. Compared with 6X plan, 6FFF plan increases the monitor units but shortens the

关 键 词：宫颈癌 非均整模式 容积旋转调强放疗 剂量学比较 

分 类 号：R815.6[医药卫生—放射医学]