兆伏级锥形束CT在食管癌放射治疗中摆位误差的分析  

Study of megavolt cone-beam computed tomography to 3-dimensional conformal radiotherapy of esophageal carcinoma

作　　者：张学成 杨植 王永锋 王方勇 刘小超 华保卫 韩良辅 

机构地区：[1]西安市长安医院肿瘤中心,陕西西安710016

出　　处：《现代肿瘤医学》2013年第3期627-629,共3页Journal of Modern Oncology

摘　　要：目的:评估兆伏级锥形束CT(CBCT)图像引导食管癌三维适形放射治疗(3DRT)的摆位误差,计算临床靶体积(CTV)到计划靶体积(PTV)的外放边界。方法:用西门子配备有MVision兆伏级CBCT的直线加速器,对32例三维适形放疗(3DRT)的食管癌患者,在治疗的5周内每周1次,分别对治疗前、摆位误差调整后行CBCT扫描。通过计划CT图像与治疗图像进行匹配,获取左右(X)、头脚(Y)、前后(Z)的摆位误差,计算CTV到PTV的外放边界。结果:32例患者共获取320幅CBCT图像。在校正前,患者的摆位误差分别为左右(-1.25±3.28)mm、头脚(-0.63±5.00)mm、前后(0.84±3.26)mm;根据Van等提供的公式,CTV至PTV的外放边界为左右9.38mm,头脚12.28mm,前后7.70mm。摆位误差调整后:误差分别为左右(0.19±1.89)mm、头脚(-0.56±3.71)mm和前后(0.53±1.54)mm,与调整前相比在三维方向均有降低,且有统计学差异(P<0.05)。摆位误差调整后PTV外扩边界,左右3.68mm,头脚4.83mm,前后4.24mm。结论:通过CBCT获取食管癌患者的摆位误差并对其进行纠正,能显著降低分次间的摆位误差,提高放疗精确度,减小PTV外放边界。Objective：To evaluate the setup errors in radiotherapy on esophageal carcinoma by Megavoh Cone - beam Computed Tomography and propose optimum margin of planning target volume （ PTV ）. Methods： Thirty - two patients received 3 - dimensional conformal radiotherapy by imaging - guided with aregavolt MVision CBCT scans e- quipped in ONCOR linear accelerator. The five fractional CBCT volume - imaging weekly and data obtained after ini- tial setup and after therapy were dimensionally matched with planned CT image. Results： A total of 320 MVCBCT scans were obtained. The initial average set - up error （x ± s） was （ - 1.25 ±3.28） ram, （ - 0.63 ＋ 5.00） mm and （0.84± 3.26） mm in the left - right（ LR）, superior - inferior（SI） and anterior - posterior（AP） direction, respective- ly. After online correction and treatment , average set - up error （ x _＋ s ） was （ 0. 19 -＋ 1.8 9 ） mm, （ - 0.5 6 ＋ 3.71 ） mm and（0.53 ＋ 1.54）ram in the LR,SI and AP directions,respectively. Comparing with the pre - and post - correction, setup errors decreased significantly on all three axes （P 〈 0.05 ）. According to the formalar suggested by van Herk et al, while without correction of CBCT setup errors, PTV margin in three dimension were Lat （ cm ） - X ： 9.3 8 mm, Long （ cm ） - Y ： 12.2 8 ram, Vert （ cm ） - Z ： 7.70ram. While with correction, they were Lat （cm） - X：3.68ram,Long（cm） - Y：4.83mm,Vert（cm） - Z：4.24mm. Comparing the pre - and post - correction, there were statistically significant differences in PTV margins（P 〈 0.05 ）. Conclusion： MVision CBCT could help to im- prove the precision of 3 - D radiotherapy for esophageal carcinomas and reduce the CTV - PTV margin significantly.

关 键 词：食管癌 三维适形放射治疗 锥形束CT 摆位误差 图像引导 

分 类 号：R735.1[医药卫生—肿瘤]