摘要目的:探讨γ射线立体定向放射治疗设备CybeRay ?实时图像引导系统检测颅脑肿瘤患者治疗过程中的位置误差情况以及该系统位置误差检测的不确定性。 方法:采用γ射线立体定向放射治疗设备CybeRay ?对人形头部模体和颅脑肿瘤患者进行照射或治疗，均使用热塑膜面罩固定，放疗过程使用千伏级投影进行实时成像，收集5次模体治疗和9例开封市肿瘤医院收治的颅脑肿瘤患者27分次的实时图像监测数据，确定位置误差检测系统的精度和不确定性。 结果:通过模体测试实时图像引导系统在左右、头脚、腹背3个方向的位置误差分别为（-0.02±0.41）、（-0.05±0.22）、（0.01±0.35）mm；检测到的患者在治疗过程中左右、头脚、腹背3个方向的位置误差分别为（-0.13±0.48）、（-0.05±0.48）、（0.11±0.36）mm；去除位置误差的不确定性因素，患者在3个方向的真实位置误差分别为（-0.11±0.25）、（0±0.43）、（0.10±0.08）mm。结论:基于实时图像引导的患者位置误差的标准差小于0.5 mm，采用无创热塑膜固定颅脑肿瘤患者临床可操作性强，并可将患者位置误差限制在0.5 mm以内。CybeRay ?实时图像引导系统可准确用于无框架立体定向放射外科/立体定向放疗过程中患者的位置误差检测。

abstractsObjective:To determine the motion detection uncertainty of the real-time CybeRay ? imaging system and patient intrafractional motion with thermoplastic mask-based immobilization. Methods:Real-time CybeRay ? imaging system was used for irradiation and treatment for head phantom and patients with brain tumors. All patients were immobilized with thermoplastic masks. Real-time imaging was delivered using kilovoltage projection images during radiotherapy. The detected patient motion data was collected from 5 head phantom measurements and 27 treatment fractions of 9 brain tumor patients admitted to Kaifeng Cancer Hospital. The accuracy and uncertainty of the motion monitoring system were determined. Results:The mean and standard deviation (SD) of the detected motion in the X, Y, and Z directions for phantom were (-0.02±0.41) mm, (-0.05±0.22) mm and (0.01±0.35) mm, respectively. The detected motion in the X, Y and Z directions for patents were (-0.13±0.48) mm, (-0.05±0.48) mm and (0.11±0.36) mm, respectively. After removing the motion detection uncertainty, the actual intrafractional motion of patients were (-0.11±0.25) mm, (0±0.43) mm and (0.10±0.08) mm in three directions, respectively. Conclusions:The uncertainty of real-time imaging-based motion monitoring system of CybeRay ? is less than 0.5 mm. It is feasible to apply thermoplastic masks for brain tumor patients in clinical practice, which can provide steady immobilization and limit the SD of patient intrafractional motion within 0.5 mm. Real-time imaging-based motion monitoring system of CybeRay ? is accurate for patient motion monitoring during frameless stereotactic radiosurgery/radiotherapy.