摘要目的：通过分析千伏级 CBCT 引导前列腺癌 IMRT 的数据，为选择合理的图像配准方法和适宜的外放边界提供临床依据。方法针对16例接受根治性 IMRT 的前列腺癌患者，共行CBCT 在线校正治疗体位214次。采用常规皮肤标记激光对位后采集图像，将所获得 CBCT 图像与计划 CT 图像进行默认自动配准、骨性配准、软组织配准及手动靶区配准。比较4种配准方式之间差异，并计算由 CTV 外放产生 PTV 间距。结果16例患者默认自动配准、骨性配准、软组织配准及手动靶区配准方式在左右、前后、上下方向平移摆位误差分别为（－0．6±2.8）、（－0．6±4.5）、（－0．6±3.8） mm，（－0．7±2.7）、（－0．9±4.5）、（－0．8±4.1） mm，（－0．8±2.6）、（－0．3±4.4）、（－1．1±4.0） mm，（－0．6±2.9）、（－0．7±5.1）、（－0．9±3.9） mm。经分析4种配准方式之间相近。 PTV 在左右、前后、上下方向外放间距分别为4.7、5.2、6.5 mm。结论综合各种因素考虑，应用在线默认自动配准＋手动微调CBCT 引导放疗技术治疗前列腺癌患者更为合适。 PTV 安全外放边界在左右、前后、上下方向分别为4.7、5.2、6.5 mm。

abstractsObjective To analyze the data from intensity-modulated radiotherapy ( IMRT) for prostate cancer guided by kilovoltage cone-beam computed tomography (CBCT), and to provide a clinical basis for selecting the optimal image registration method and reasonable target volume margins.Methods A total of 16 patients with prostate cancer who received radical IMRT were enrolled, and CBCT for online position verification was performed 214 times.The images were obtained after conventional skin marking and laser alignment, and automatic registration, bone registration, soft tissue registration, and manual registration were performed for CBCT images and planned CT images.The differences between these four registration methods were evaluated, and the margins for extending clinical target volume into planning target volume (PTV) were calculated.Results The setup errors in left-right, anterior-posterior, and cranial-caudal directions for automatic registration, bone registration, soft tissue registration, and manual registration were-0.6±2.8 mm/-0.6±4.5 mm/-0.6±3.8 mm,-0.7±2.7 mm/-0.9±4.5 mm/-0.8±4.1 mm,-0.8± 2.6 mm/-0.3±4.4 mm/-1.1±4.0 mm, and-0.6±2.9 mm/-0.7±5.1 mm/-0.9±3.9 mm, respectively. There were no significant differences between the four registration methods.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions were calculated as 4.7 mm, 5.2 mm, and 6.5 mm, respectively.Conclusions With a comprehensive consideration of various factors, a default setting of automatic registration and manual fine adjustment is appropriate for CBCT-guided radiotherapy for prostate cancer.The margins for extension in the left-right, anterior-posterior, and cranial-caudal directions are 4.7 mm, 5.2 mm, and 6.5 mm, respectively.