摘要目的:探讨采用容积旋转调强放疗（VMAT）非均整器（FFF）模式下锥形束CT（CBCT）图像引导对脊柱转移瘤体部立体定向放疗（SBRT）摆位误差的影响。方法:回顾性分析吉林省肿瘤医院2020年8月至2022年1月15例行SBRT的脊柱转移瘤患者临床资料。骨转移灶放疗剂量32 Gy/4次，每次放疗前后均行CBCT扫描。每例患者行4次放疗，15例患者共进行60次SBRT，共获得120幅CBCT容积图像，对图像进行分析，计算系统误差（Σ）和随机误差（σ）。比较放疗前后的左右（X）、头脚（Y）、前后（Z）方向上的平移摆位误差和旋转摆位误差，均以Σ±σ表示。结果:15例患者放疗前后X方向上的平移摆位误差分别为（0.14±0.27）cm、（0.07±0.19）cm（ P<0.001），Y方向上分别为（-0.05±0.33）cm、（0.00±0.19）cm（ P=0.001），Z方向上分别为（-0.13±0.19）cm、（-0.02±0.14）cm（ P=0.012）。放疗前后X方向上的旋转摆位误差分别为（-0.31±0.76）°、（-0.09±0.34）°（ P<0.001），Y方向上分别为（-0.13±0.88）°、（-0.07±0.36）°（ P<0.001），Z方向上分别为（0.10±0.51）°、（0.16±0.38）°（ P<0.001）。 结论:采用VMAT-FFF模式进行脊柱转移瘤SBRT时，应用CBCT校正后可缩小平移摆位和旋转摆位的Σ和σ，提高放疗精确性。

abstractsObjective:To evaluate the effect of image-guided with cone-beam computed tomography (CBCT) based on volumetric modulated arc therapy (VMAT)-flattening filter free (FFF) on the setup errors of stereotactic body radiotherapy (SBRT) in patients with spinal metastatic tumors.Methods:The clinical data of 15 patients with spinal metastatic tumors who underwent SBRT in Jilin Cancer Hospital from August 2020 to January 2022 were retrospectively analyzed. The radiotherapy dose of bone metastasis was 32 Gy per 4 times and CBCT scanning was performed before and after radiotherapy. Every patient received radiotherapy 4 times; all 15 patients underwent SBRT 60 times in total and 120 CBCT volume images were finally obtained and analyzed. The systematic error (Σ) and random error (σ) were calculated at different correction threshold levels. The translational setup error and rotational setup error at the left-right (X axis), head-foot (Y axis) and front-back (Z axis) directions before and after radiotherapy were compared, which were expressed as Σ ± σ.Results:The pre-SBRT and post-SBRT translational setup errors were (0.14±0.27) cm and (0.07±0.19) cm, respectively ( P<0.001) in the X direction, (-0.05±0.33) cm and (0.00±0.19) cm, respectively ( P = 0.001) in the Y direction, (-0.13±0.19) cm and (-0.02±0.14) cm, respectively ( P = 0.012) in the Z direction. The pre-SBRT and post-SBRT rotational setup errors were (-0.31±0.76)° and (-0.09±0.34)°, respectively ( P < 0.001) in the X direction, (-0.13±0.88)° and (-0.07±0.36) °, respectively ( P < 0.001) in the Y direction, (0.10±0.51)° and (0.16±0.38)°, respectively ( P < 0.001) in the Z direction. Conclusions:CBCT correction could reduce Σ and σof the translational setup and rotational setup, increase the accuracy of SBRT based on VMAT-FFF for patients with spinal metastatic tumors.