胸段食管癌图像引导调强放射治疗的摆位误差分析

目的  探讨锥形束CT扫描在胸段食管癌患者调强放射治疗摆位中的重要性。方法  选取胸段食管癌调强放射治疗患者30例，胸腹板和热塑体膜进行体位固定，首次治疗前对患者行锥形束CT（CBCT）扫描，治疗过程中每周行1次CBCT扫描，并记录患者左右、头脚、腹背3个方向的误差数值，对数据进行分析并在线纠正摆位误差。结果  30例患者行168次CBCT扫描验证摆位误差，校正前患者左右（X）、头脚（Y）、腹背（Z） 3个方向的摆位误差分别为（0.195±0.075）、（0.273±0.091）和（0.202±0.079）cm；校正后误差分别为（0.024±0.013）、（0.044±0.023）和（0.030±0.016）cm。治疗过程中摆位误差逐渐减小，治疗体位重复率高。30例患者顺利按放射治疗计划完成治疗，肿瘤局部控制率为96.8%，不良反应明显下降。结论  胸段食管癌调强放射治疗中行CBCT扫描具有重要作用；胸段食管癌调强放射治疗中，重复摆位必然会产生一定误差，只有分析误差产生原因，采取有效措施减少误差，才能使靶区及周围正常组织器官的剂量分布更准确，为临床放疗提供质量保证。

Beam position error analysis of image-guided intensity-modulated radiotherapy for thoracic-segment esophageal cancer

 Objective To investigate the importance of cone-beam computed tomography (CBCT) scan in setup of image-guided radiotherapy (IMRT) for thoracic-segment esophageal cancer. Methods Thirty patients with thoracic-segment esophageal cancer were enrolled into the study. All the patients were scanned by kilovoltage CBCT before treatment and every week during radiotherapy. The setup errors of isocenter positions on the axes of X, Y and Z were recorded. The data were analyzed and placement error was corrected online. Results The position errors in the 30 patients were verified by 168 times of CBCT scan. Before correction the positioning errors of X, Y and Z three directions were (0.195 ± 0.075), (0.273 ± 0.091) and (0.202 ± 0.079) cm respectively. After correction the errors were (0.024 ± 0.013), (0.044 ± 0.023) and (0.030 ± 0.016) cm respectively. All the patients completed the radiotherapy plan. Local control rate of the tumor was 96.8%, and adverse reactions decreased. Conclusions CBCT scan plays an important role in IMRT for esophageal cancer and the setup errors always occur in radiotherapy of esophageal cancer. Only analyzing the causes of errors and taking effective measures to reduce errors can make more accurate dose distribution in target and surrounding normal tissues and organs, and assure the efficacy of clinical radiotherapy.