摘要目的:研究俯卧盆腔固定装置对妇科肿瘤调强放射治疗剂量学的影响。方法:回顾性分析2020年8月至2021年6月在中山大学附属第三医院接受放疗的宫颈癌和子宫内膜癌患者共20例，每位患者均采取两种方法勾画外轮廓，第1种仅包含患者轮廓，第2种包含患者轮廓和固定装置。每例患者在放疗计划系统(TPS)中分别用两组轮廓计算相同的7野调强计划，通过剂量体积直方图(DVH)和计划相减来比较不带固定装置计划Plan without和带固定装置计划Plan with间剂量学差异。在仿真人模体中使用EBT3胶片验证实际点剂量，并分别比较其与上述两个计划剂量的差异。 结果:Plan with的靶区100%、98%处方剂量的覆盖体积 V50 Gy、 V49 Gy和均值 Dmean分别下降了19.75%、7.99%和2.54%( t ＝ 8.96、10.49、22.09， P<0.01)；皮肤的 V40Gy、 V30Gy、 V20Gy、 V15Gy和 Dmean分别上升了51.79%、51.05%、45.72%、33.63%和10.80%( t ＝ －2.54、－5.63、－15.57、－24.06、－13.88， P<0.01)；其他危及器官无显著性变化。仿真人模体中EBT3胶片点剂量测量结果提示，腹盆部皮肤剂量约增高了37.24%( t ＝ 10.86， P<0.01)。 结论:俯卧盆腔固定装置可以有效降低小肠的低剂量，但其引起的射线衰减会使得放疗计划靶区的覆盖下降、腹盆部皮肤剂量陡增，尤其是需要照射腹股沟和会阴区的患者。

abstractsObjective:To investigate the dosimetric effects of prone immobilization devices combined with a belly board (PIDBBs) in the intensity-modulated radiotherapy (IMRT) for gynecologic cancers.Methods:A total of 20 patients with cervical or endometrial cancer treated with radiotherapy in the Third Affiliated Hospital of Sun Yat-sen University from August 2020 to June 2021 were retrospectively analyzed. Two sets of body contours were outlined for each patient. One set of body contours did not contain the immobilization devices, and the other contour set included the immobilization devices. For each patient, doses were calculated for the two sets of contours using the same 7-field IMRT plan and were recorded as Plan without and Plan with. The dosimetric difference caused by the immobilization devices was assessed by comparing the parameter values in the dose-volume histograms (DVHs) and by plan subtraction. The Gafchromic EBT3 film and anthropomorphic phantom were used to verify the calculated doses. Results:The target coverage and average dose of Plan with were lower than those of Plan without. Specifically, the V50 Gy, V49 Gy, and Dmean of planning target volume (PTV) decreased by 19.75%, 7.99%, and 2.54% ( t = 8.96, 10.49, 22.09, P < 0.01), respectively. The V40 Gy, V30 Gy, V20 Gy, V15 Gy, and Dmean of skins increased by 51.79%, 51.05%, 45.72%, 33.63% and 10.80% ( t = -2.54, -5.63, -15.57, -24.06, -13.88, P < 0.01), respectively. Doses to other organs at risk (OARs) showed no significant differences. As indicated by the EBT3 measurements, the doses to skins of the abdomen and pelvis on the anthropomorphic phantom increased by approximately 37.24% ( t = 10.86, P<0.01). Conclusions:Although PIDBBs can effectively reduce the low dose to the small intestine, the radiation attenuation caused by them can reduce the PTV coverage of radiotherapy plans and increase the doses to abdominal and pelvic skins sharply, especially for patients requiring irradiation of the groin and perineum.