前列腺癌调强放疗中直肠充盈状态对靶区及危及器官的影响

目的 探讨前列腺癌调强放疗（IMRT）中直肠充盈状态对靶区及危及器官（OAR）的影响。方法 选取15例局限期前列腺癌IMRT患者，在直肠充盈和排空状态下采集2次盆腔定位CT图像，由同一高年资放疗医师勾画靶区及OAR（如直肠、膀胱、股骨头）后，由同一高年资放疗物理师在相同处方剂量下行调强放疗计划设计。将2种直肠充盈状态下的靶区和OAR剂量学参数进行分析和配对t检验。结果 当定位和实际治疗时直肠体积一致（排空或充盈状态），直肠不同体积状态对靶区、膀胱及股骨头剂量学参数无统计学差异（P＞0.05）。当出现本试验假设的CT定位时为直肠排空状态而实际治疗时为直肠充盈状态，放疗靶区的平均剂量、均匀指数、适形指数差异具有统计学意义（P＜0.05）；直肠受照射剂量增加，直肠平均剂量、V50和V70增加56％、58％和288％（P＜0.05）；膀胱及股骨头剂量学参数则不受直肠状态的影响（P＞0.05）。结论 前列腺癌IMRT治疗期间直肠保持充盈状态一致能保证放疗计划得到很好的执行，反之当定位与放疗期间直肠充盈状态不一致时，放疗靶区及直肠剂量学将出现明显差异。

Impacts of rectum filling status on dosimetric parameters of target volume and organ at risk in intensity-modulated radiotherapy for prostate cancer

Objective To investigate the impact of rectum filling status on the dosimetric parameters of target volume and organ at risk （OAR） in intensity-modulated radiotherapy （IMRT） for patients with prostate cancer. Methods Fifteen patients with prostate cancer were enrolled in this study. Target and OAR were contoured by the same doctor both when the rectum was full and empty. And the IMRT plan was designed by the same medical physicist at the same radiotherapy dose. The impact of rectum filling status in dose of target and OAR during radiotherapy was investigated. Results If the rectum filling status was consistent in orientation and radiation， the rectum fill status was not associated with the dosimetric parameter of target volume and bladder， femoral heads （P＞0.05）. If the rectum filling status was not consistent in orientation and actual radiation， the dosimetric dose， uniform index and conformal index of target were different（P＜0.05）. The impacts on bladder and femoral heads were not significant. ConclusionTo guarantee the perfect execution of IMRT in patients with prostate cancer， it is recommended to keep the same rectal filling status during orientation and actual radiation.