目的 探讨立体定向放射治疗（SBRT）中体位固定装置和治疗床对计划剂量的影响。 方法 回顾性选取23例SBRT患者，CT模拟定位均为发泡胶或真空袋固定。每例患者的CT图像均被勾画为两套外轮廓：一套仅涵盖患者皮肤（Body），另一套则包括皮肤及固定装置（Body_F）。首先基于Body轮廓制定满足临床需求的参考计划Plan（noFC）。在不改变Plan（noFC）参数和照射野设置的前提下，分别基于Body_F（仅加固定装置）、Body + C（仅加治疗床）和Body_F + C（加固定装置及治疗床）3种不同轮廓进行计划计算，得到Plan（F）、Plan（C）和Plan（FC）。通过对比这4种计划下的靶区及皮肤剂量参数，评估体位固定装置和治疗床对计划剂量的影响。 结果 相较于仅基于患者皮肤轮廓的计划，包含体位固定装置的计划在靶区的高剂量、处方剂量覆盖以及平均剂量方面均有所降低。其中处方剂量的105%所占体积（PTV/V105%p）在Plan（FC）与Plan（noFC）中差异达到61.86%。相较于仅基于患者皮肤轮廓的计划，包含体位固定装置的计划在皮肤的高量和平均量方面均有所增加。其中距离皮肤2 mm范围内，10 cc皮肤的剂量（body2mm/D10cc）在Plan（FC）与Plan（noFC）中差异达到21.36%。对于所有的靶区及皮肤的参数，Plan（C）与Plan（noFC）之间差异无统计学意义（P > 0.05）。在包含固定装置的计划剂量差异中，靶区到皮肤的最小距离与皮肤受量表现负相关。靶区与皮肤距离越小，固定装置对皮肤剂量影响越大。 结论 SBRT中的体位固定装置会导致射线衰减和建成效应变化，显著降低靶区剂量参数，同时增加皮肤剂量。靶区与皮肤距离越近，固定装置对皮肤剂量影响越大。在制定放疗计划时，建议将固定装置纳入外轮廓设计。

Objective To investigate the impact of immobilization devices and treatment couches on the planned dose in stereotactic body radiation therapy （SBRT）. Methods A retrospective study was conducted involving 23 SBRT patients， all of whom underwent CT simulation with foam padding or vacuum bag immobilization. For each patient， two sets of contours were outlined on CT images： one encompassing only the patient′s skin （Body）， and the other including the skin plus immobilization devices （Body_F）. Initially， a reference plan（noFC） meeting clinical requirements was generated based on the Body contour. Without altering the plan（noFC） parameters and field setups， plan calculations were performed separately based on three different contours： Body_F （with immobilization devices only）， Body + C （with treatment couch only）， and Body_F + C （with both immobilization devices and treatment couch）， yielding plan（F）， plan（C）， and plan（FC）， respectively. By comparing the target and skin dose parameters across these four plans， the effects of immobilization devices and treatment couches on the planned dose were evaluated. Results Compared to plans based solely on the patient′s skin contour， plans incorporating immobilization devices showed reduced high?dose， prescription dose coverage， and average dose in the target volume. Notably， the difference in the percentage of the planning target volume （PTV） receiving 105% of the prescribed dose （PTV/V105%p（%）） between plan（FC） and plan（noFC） could reach 61.86%. Conversely， plans with immobilization devices increased both the maximum and average skin doses. Specifically， the dose to 10 cc of skin within 2 mm of the surface （body 2 mm/D 10 cc（Gy）） showed a 21.36% difference between plan（FC） and plan（noFC）. For all target and skin parameters， no statistically significant differences were observed between plan（C） and plan（noFC）. Among plans with immobilization devices， the minimum distance from the target to the skin correlated inversely with skin dose， indicating greater impact on skin dose with closer proximity. Conclusions Immobilization devices in SBRT lead to beam attenuation and altered build?up effects， significantly reducing target dose parameters while increasing skin dose. The closer the target is to the skin， the greater the impact of immobilization devices on skin dose. It is recommended to incorporate immobilization devices into the contour design during radiotherapy planning.