基于离线自适应放疗的宫颈癌病例靶区外扩边界及其剂量评估

目的 分析行容积旋转调强放射治疗宫颈癌病例在离线自适应放疗（off-line ART）中靶区的外扩边界及其剂量学参数。方法 选取50例宫颈癌病例，采用随机配对法均分成试验组与对照组，每例患者每周行2次锥形束CT （CBCT）扫描，记录整个治疗过程中，患者在左右（LR）、前后（AP）与头脚（CC）方向上的摆位误差值，利用靶区外放边界公式计算新的临床靶区体积（CTV）-计划靶区体积（PTV）的外扩边界。同时，将摆位误差值归一至等中心点（ISO），回归治疗计划系统，对照组在原有PTV的基础上移动ISO后重新计算剂量，试验组在得到新的外扩边界后移动ISO重新计算剂量，比较评估两组计划在重新计算剂量后的CTV与危及器官剂量学参数。结果 根据靶区外放边界公式，CTV外扩边界在LR、AP和CC方向上分别为0.45、0.46和0.82 cm。治疗计划系统（TPS）剂量再计算结果显示，试验组在CTV的D_100%与D_95%上优于对照组（t=-8.16、-6.73，P<0.05），在股骨头的V₄₀、V₃₀以及D_mean上均优于对照组（t=3.14、-9.52、-7.48，P<0.05），在骨盆的V₃₄与D_mean上均优于对照组（t=10.14、-9.38，P<0.05）。结论 在宫颈癌的容积旋转调强放射治疗中，off-line ART技术可以有效地减少CTV-PTV的外扩边界，并且可以提高靶区的照射覆盖范围，减少相应危及器官的照射剂量。

Target setup margin and dose evaluation for cervical cancer cases based on the off-line adaptive radiotherapy

Objective To study the target setup margin and dose evaluation for cervical cancer patients with volume-modulated arc therapy in the off-line adaptive radiation therapy (off-line ART), Methods A total of fifty patients with cervical cancer were randomly divided into test group and control group. Cone beam CT scanning was performed twice a week, the setup errors in directions of LR, AP and CC were recorded in the whole treatment process. The target setup formula was used to calculate the new CTV-PTV setup margin. At the same time, the setup error was returned to planning isocenter (ISO). For the control group, the dose was recalculated on the basis of the original PTV after considering ISO shift. For the test group, the dose was also recalculated after the new extended boundary of the target. The dosimetric parameters of CTV and organs at risk (OAR) were evaluated between two groups after dose recalculation. Results According to the target setup formula, extended boundaries of CTV in the direction of LR, AP, CC were 0.45, 0.46 and 0.82 cm, respectively. The test group increased in CTV with D_100% and D_95% (t=-8.16, -6.73, P<0.05) and decreased in femoral head with V₄₀, V₃₀ and D_mean (t=3.14, -9.52, -7.48, P<0.05) than the control group. The test group decreased in the pelvis with V₃₄ and D_mean than control group (t=10.14, -9.38, P<0.05). Conclusions The CTV-PTV setup margin and the dose of OAR were effectively reduced, and the coverage of target area was extended when the off-line ART technology was conducted in the volume-modulated arc therapy for cervical cancer.