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目的探讨图像引导放疗(IGRT)系统的临床摆位误差。方法应用医科达SynergyTM系统治疗51例,其中头颈部肿瘤19例,胸部肿瘤25例,腹、盆部肿瘤7例。每次照射前获取X线容积图像(XVI)即锥形束断层扫描(CBCT),将CBCT图像和计划CT图像及其靶中心匹配,获得靶中心x、y、z方向的误差,分析误差及其分布规律。结果CBCT图像对比度好,临床上能清楚显示肿瘤大小、位置及其和周围的关系。51例每次治疗开始前的CBCT共955次,分别分析头颈部、胸部及腹、盆部摆位误差,均呈正态分布。系统误差(均数)±随机误差(标准差)在x、y、z方向分别为头颈部(- 0.3±1.5)、(-0.3±1.6)、(0±1.3)mm,胸部(-0.6±2.9)、(-0.2±5.6)、(0.7±3.2)mm,腹、盆部(-0.8±2.1)、(-0.3±5.9)、(0.1±2.6)mm。结论通过CBCT测量治疗前摆位误差并实时调整摆位误差,可大大提高患者摆位精度,同时为正确设定计划靶体积(PTV)提供了依据。
Objective To investigate the clinical setup error of image guided radiotherapy (IGRT) system. Methods The medical science SynergyTM system was used in the treatment of 51 cases, including 19 cases of head and neck cancer, 25 cases of chest tumor, 7 cases of abdominal and pelvic tumors. Obtain X-ray volumetric image (XVI), cone beam tomography (CBCT) before each irradiation, match CBCT images with planned CT images and their target centers, and obtain the errors in the x, y and z directions, the analysis errors and Its distribution. Results CBCT image contrast is good, clinically clear tumor size, location and its relationship with the surrounding. A total of 955 CBCTs were performed before the start of each treatment in 51 patients. The errors of the head, neck, chest, abdomen and pelvis were analyzed respectively and all showed a normal distribution. The systematic errors (mean) ± random errors (standard deviations) were respectively head and neck (-0.3 ± 1.5), (± 0.3 ± 1.6), (± 1.3) mm and chest (-0.6 ± 2.9 ± 0.2 ± 5.6, 0.7 ± 3.2 mm, -0.8 ± 2.1, ± 0.3 ± 5.9 and ± 0.1 ± 2.6 mm respectively. Conclusions Measurement of pre-treatment setup error and adjustment of positioning error in real time by CBCT can greatly improve patient positioning accuracy and provide basis for setting PTV correctly.