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目的:测量千伏锥形束CT(CBCT)引导脑转移瘤放疗计划靶区设定过程中临床靶区(CTV)-计划靶区(PTV)边缘外放值。方法:14例脑转移瘤患者应用热塑面膜+头枕固定,静脉注射造影剂后行螺旋CT扫描,Eclipse计划系统制定治疗计划,应用影像引导放疗系统给予患者前10次治疗前CBCT和计划CT配准,治疗结束后再次给予CBCT和计划CT配准,记录X轴(左右)、Y轴(前后)以及Z轴(上下)3个方向偏移值。结果:总系统误差的标准差X轴为0.92 mm,Y轴为0.95 mm,Z轴为1.10 mm;其相对应的总随机误差的标准差X轴为2.19 mm,Y轴为1.87 mm,Z轴为1.94 mm。根据VanHerk公式,CTV-PTV外放结果X轴为3.2 mm,Y轴为3.5 mm,Z轴为4.0 mm。结论:增强扫描可以使脑转移瘤在kVCBCT中显像,脑转移瘤适形放疗CTV-PTV外放可以为4.0 mm。
OBJECTIVE: To measure the value of clinical target zone (CTV) -planned target zone (PTV) margins in the setting of target zone of radiation therapy in brain metastases guided by kilovoltage cone beam CT (CBCT). Methods: Fourteen patients with brain metastases were fixed with a thermoplastic mask and a head restraint. A spiral CT scan was performed after intravenous injection of contrast medium. The Eclipse planning system developed a treatment plan. The patients were treated with the imaging guided radiotherapy system before the first 10 treatments of CBCT and planned CT After registration, the CBCT and the planning CT are again registered after the treatment is completed. Three offset values of X axis (left and right), Y axis (front and back) and Z axis (up and down) are recorded. Results: The standard deviation of the total systematic error was 0.92 mm, the Y-axis was 0.95 mm and the Z-axis was 1.10 mm. The standard deviation of the total random errors was 2.19 mm, Y axis was 1.87 mm, Z axis 1.94 mm. According to VanHerk’s formula, the X-axis of CTV-PTV is 3.2 mm, the Y-axis is 3.5 mm and the Z-axis is 4.0 mm. Conclusion: Enhanced CT scan can make brain metastases in kVCBCT imaging, brain metastases conformal radiation CTV-PTV external release can be 4.0 mm.