基于CBCT非小细胞肺癌外放边界研究

目的：探讨非小细胞肺癌（Non-Small Cell Lung Cancer，NSCLC）放疗靶区外放边界的确定。方法：本研究随机抽取14例行锥形束CT（Cone-Beam Computer Tomography，CBCT）扫描的NSCLC体部立体定向放疗（Stereotactic BodyRa-diationTherapy，SBRT）治疗患者，利用治疗前CBCT扫描图像与定位CT图像匹配，得出所有患者的摆位误差。利用国际辐射单位及测量委员会（International Commission 0n Radiation Units and Measurements，ICRU）第83号文件报道的计算外放边界的公式计算出NSCLC患者放疗靶区的外放边界。放射治疗肿瘤组织（Radiation Therapy Oncology Group，RTOG）推荐肺部肿瘤外放边界为左右、前后0．50cm，上下1．00cm，与本研究结果进行对比。结果：NSCLC患者摆位系统误差在左右、前后、上下三个方向上分别为（-0．03±0．23）cm、（-0．02±0．42）cm、（0．02±0．25）cm。在ICRU第83号文件报道的公式中，利用VanHerk提出的计算公式得出的靶区外放边界最大，左右、前后、上下分别为0．72cm、0．74cm、1．30cm。结论：与RTOG提出的肺部肿瘤外放边界相比，利用本研究方法计算各个方向的外放边界比原来RTOG提出的外放标准更加精确，给个体化放疗外放边界的选取提供了很好的依据。

Study of the Individualization Margin Definition by CBCT for NSCLC

Abstract：Objective： This study mainly focuses on calculating target margin in the radiotherapy treatment planning for non-small cell lung cancer （NSCLC）. Methods： In order to study the accuracy and reproducibility of patient and beam set-up, Cone-beam Computer Tomography （CBCT） images from 14 patients were evaluated. Discrepancies between planned and actual field positions were measured and the systematic and random errors were calculated. Then, several equations published in international commission on radiation units and measurements （ICRU） were applied in calculating target margin. It is recommended that the target margin were 0.50 cm in the transversal plane and 1.00 cm in the cranially and caudally in Radiation Therapy Oncology Group. Finally, the margin data recommended from the RTOG and the ones calculated from this paper method were compared. Results：The set-up errors were （-0.03±0.23） cm in the medio-lateral directions, （-0.02±0.42） cm in the dorso-ventral directions, （0.02±0.25） cm in the cranio-caudal directions. The target margin calculated by van Herk＇ s equation was the largest in all equations published in ICRU. we conclude that the magin were 0.72 em in the medio-lateral directions, 0.74 cm in the dorso-ventral directions, 1.30 cm in the craniocaudal directions. Conclusions： Compared with the margin recommended from the RTOG, the margin used in this paper is more accurate, giving the reference data for individualized radiotheraoy treatment.