肺部肿瘤立体定向放疗技术中基于锥形束CT影像的摆位误差分析

背景与目的:准确的靶区位置是肺部肿瘤立体定向放疗的重要影响因素.该研究旨在分析在肺部肿瘤患者立体定向放疗中基于锥形束CT(cone-beam CT,CBCT)影像的摆位误差及其影响因素.方法:29例单发肺部恶性肿瘤行立体定向放疗的患者,每次放疗前行CBCT扫描,将得到的CBCT图像与定位CT图像匹配,获得前后、头脚和左右方向的摆位误差值,并计算临床靶区(clinical target volume,CTV)外扩至计划靶区(planning target volume,PTV)的边界.同时,还分析对可能影响摆位误差的临床参数等进行分层比较.结果:29例患者共获得155幅CBCT图像.考虑误差方向时前后、头脚和左右方向摆位误差分别为(-1.68±3.62)、(-1.34±3.90)和(0.36±2.15)mm,只考虑误差数值大小时分别为(3.16±2.42)、(3.29±2.48)和(1.74±1.30)mm.根据摆位误差得到CTV外扩至PTV的边界在前后、头脚和左右方向分别为9.6、10.0和5.3 mm.病灶位于周围的肺部肿瘤患者前后方向摆位误差更大(P=0.007),下肺病灶、右肺病灶、肺转移灶在头脚方向摆位误差更大(P=0.008、0.000和0.000).结论:肺部肿瘤患者放疗中的头脚和前后方向摆位误差较大,立体定向放疗需采用锥形束CT扫描、呼吸控制等技术以减少摆位误差.

Analysis of setup errors in lung stereotactic body radiotherapy with cone-beam CT-based image guidance

Background and purpose:Correct target positioning is an important factor affecting the precision of stereotactic body radiotherapy (SBRT) in patients with lung tumors. This study investigated the setup errors in patients with malignant lung tumors receiving SBRT with cone-beam CT (CBCT) and analyzed the factors influencing setup errors.Methods:Twenty-nine patients with solitary malignant lung tumors were enrolled in the study. Each patient underwent SBRT with CBCT before each treatment. Setup errors in CBCT were obtained according to the matched and planned CT images in anterior-posterior (AP), superior-inferior (SI) and left-right (LR) directions. The expanding margins of clinical target volume (CTV) to planning target volume (PTV) according to the analyzed setup errors were then calculated. And the influencing factors of setup errors were analyzed.Results:A total of 155 CBCT images from 29 patients were obtained during the treatment. The setup errors were (-1.68±3.62), (-1.34±3.90) and (0.36±2.15) mm in the AP, SI and LR directions, respectively. The absolute setup errors were (3.16±2.42), (3.29±2.48) and (1.74±1.30) mm in the AP, SI and LR directions, respectively. The suggested expanding margins of CTV to PTV were 9.6, 10.0 and 5.3 mm in the AP, SI and LR directions according to the setup errors. The setup errors in the AP direction of peripheral lesions and in the SI direction of inferior, right and metastatic lesions were relatively larger(P=0.007, 0.008, 0.000 and 0.000)..Conclusion:In patients with malignant lung tumors receiving SBRT, the setup errors were more obvious in the SI and AP directions. Tumor motion management techniques including CBCT, breath-holding technique are required to reduce the setup error in patients with lung tumors receiving SBRT.