聚氨酯发泡胶结合翼板个体化塑形与负压真空袋固定肺癌放疗摆位精度比较

目的 运用KV级CBCT比较聚氨酯发泡胶结合翼板个体化塑形与负压真空袋固定在肺癌放疗中体位固定的精确度。方法 对2015—2016年在中山大学肿瘤防治中心接受胸部放疗的肺癌患者随机选取两种固定方法的患者,其中负压真空袋组 20例,聚氨酯发泡胶结合翼板个体化塑形组 19例。1 次/周CBCT图像与计划CT图像进行匹配后分别记录左右、上下和前后方向摆位误差、3D矢量位移及摆位时间,根据2.5∑+0.7σ计算PTV外放边界。成组t检验两组数据差异。结果 发泡胶组和真空袋组线性摆位误差x轴向分别为(1.80m±1.48) mm和(1.90±1.41) mm (P=0.46),y轴向分别为(2.54±1.79) mm和(3.19±2.14) mm (P=0.03),z轴向分别为(2.14±1.75) mm和(2.25±1.75) mm (P=0.35);旋转摆位误差在Rx向分别为1.15°±0.76°和1.15°±0.85°(P=0.50),Ry向分别为0.71°±0.60°和0.72°±0.43°(P=0.45),Rz向分别为0.62°±0.54°和0.46°±0.30°(P=0.06)。发泡胶组和真空袋组在x、y、z轴向PTV所需外扩边界分别为5.56、8.57、7.02 mm和5.62、9.27、7.23 mm。3D矢量位移>5 mm者,发泡胶组为40%,真空负压袋组为45%。结论 采用聚氨酯发泡胶结合翼板个体化塑形固定可在一定程度上减少肺癌放疗患者在上下方向摆位误差并减少PTV外扩边界。

Comparison of positioning accuracy between personalized polyurethane foam with wing boards and negative pressure vacuum bag in radiotherapy for lung cancer

Objective To compare the positioning accuracy between personalized polyurethane foam with wing boards and negative pressure vacuum bag in radiotherapy for lung cancer using kilovoltage cone beam computed tomography (CBCT). Methods Thirty-nine patients with lung cancer who received chest radiotherapy in our hospital from 2015 to 2016 were enrolled as subjects. In those patients, 20 were immobilized by negative pressure vacuum bags (VB group) and the others by personalized polyurethane foam with wing boards (PF group).CBCT images were acquired weekly and registered with planning CT images. Setup errors in the left-right, superior-inferior, and anterior-posterior directions, three-dimensional (3D) displacement vector, and setup time were recorded. The margin of the planning target volume (PTV) was calculated using the Van Herk formula (2.5∑+0.7σ). Between-group comparison was made by paired t test. Results The PF group had a significant smaller setup error in the y-direction than the VB group (2.54±1.79 vs. 3.19±2.14 mm, P=0.03), while there were no significant differences in setup errors in the x-or z-direction between the two groups (1.80±1.48 vs. 1.90±1.41 mm, P=0.46;2.14±1.75 vs. 2.25±1.75 mm, P=0.35). There were no significant differences in rotational setup errors in the Rx-, Ry-, or Rz-direction between the two groups(1.15°±0.76°vs. 1.15°±0.85°, P=0.50;0.71°±0.60°vs. 0.72°±0.43°, P=0.45;0.62°±0.54° vs. 0.46°±0.30°, P=0.06). The PTV margins in the x-, y-, and z-directions were expanded by 5.56, 8.57, and 7.02 mm, respectively, in the PF group, and by 5.62, 9.27, and 7.23 mm, respectively, in the VB group. The proportion of patients with 3D displacement vectors larger than 5 mm was 40% in the PF group and 45% in the VB group. Conclusions For patients undergoing radiotherapy for lung cancer, personalized polyurethane foam with wing boards can, to a certain extent, reduce the setup error in the superior-inferior direction and PTV margin expansion.