肺部肿瘤大分割放疗分次内体位移动影响因素分析

目的 应用IGRT技术,探讨肺部恶性肿瘤患者大分割放疗过程中分次内体位移动情况及相关影响因素。方法 选择江苏省肿瘤医院收治的 96例肺部恶性肿瘤接受大分割治疗的患者。每次治疗前常规行千伏级CBCT扫描并在线配准,校正误差后进行治疗。治疗后再次行CBCT扫描并配准,记录治疗后患者左右、上下、前后方向上的体位变化,应用多元线性回归分析相关影响因素与治疗后体位偏差的关系。结果 上下和前后方向随着分割序数增大分次内体位偏差减小(P=0.000);左右方向随治疗时间延长则分次内移动度增大(P=0.010),体重较大者则移动度较小(P=0.003)。相对于真空体膜,采用热塑网膜固定分次内左右移动度明显增大(P=0.009)。结论 肺部肿瘤大分割放疗分次内存在一定体位误差;这种误差不同方向上有不同的影响因素。改进相关因素,可减少分次内体位误差,提高治疗精度。

Analysis of influencing factors of intrafractional positioning errors in the hypofractionated radiotherapy for pulmonary tumors

Objective Image-guided radiation therapy (IGRT) was performed to investigate the intrafractional body motion and identify the relevant influencing factors during hypofractionated radiotherapy for malignant pulmonary tumors. Methods A total of ninety-six patients with malignant pulmonary tumors receiving hypofractionated radiotherapy in Jiangsu Cancer Hospital were enrolled in this clinical trial. The kilo-voltage cone beam CT (kV-CBCT) was acquired prior to each fraction and matched to the planning CT images to correct the set-up errors. CBCT was performed immediately after the end of treatment to evaluate the intrafractional variation in the mediolateral, anteroposterior and craniocaudal dimensions. The relationship between relevant influencing factors and intrafractional variation was analyzed using multivariate linear regression. Results In the anteroposterior and craniocaudal directions, the intrafractional positioning errors were reduced along with the increase of ordinal number of fraction (P=0.000). In the mediolateral direction,the intrafractional positioning errors were increased along with the longer duration of hypofractionated radiotherapy (P=0.010).The intrafractional positioning errors were decreased over larger body weight (P=0.003).The intrafractional positioning errors were significantly increased when vacuum bag and thermoplastic film were utilized for fixation (P=0.009). Conclusions Certain intrafractional positioning errors occur during hypofractionated radiotherapy. Relevant influencing factors differ in different directions. Relevant influencing factors should be modified to reduce intrafractional positioning variation and improve the treatment accuracy.