目的 分析医用电子直线加速器机载kV 级锥形束CT 的输出剂量及其稳定性.方法 用Unidos 剂量仪和0.6cc 电离室在空气中 对Synergy 机载的XVI kV 级锥形束CT 的空气比释动能、剂量输出稳定性、百分深度剂量进行测量.结果 拍片模式下XVI 空气比释动能随管电压呈二次方变化;空气比释动能随管电流和曝光时间线性变化;透视模式下,空气比释动能随图像 桢数线性变化.输出剂量的重复性以及随机架角度的波动小于±1%.体模中百分深度剂量随管电压增加而变大.结论 锥 形束CT 的剂量输出比较稳定,但随成像参数的设置变化范围大.临床应用时需要合理选择曝光条件,尽量减少患者接受 的剂量.%Objective To evaluate the radiation output and stability of linac-integrated kV cone beam CT unit. Methods Air kermas in radiographic mode were measured with 0.6cc ion chamber and Unidos electrometer for Synergy-integrated XVI kV cone beam CT unit. Air kermas vs image frames were measured in fluoroscopic mode. Output stability and depth doses were measured. Results The air kerma increased quadratically with the increased tube voltage;while increasing linearly with the tube current;exposure time;and number of frames. The radiation output stability and its change with the gantry angle were within ±1%. The percentage depth dose increased with higher tube voltage. Conclusion The radiation output of XVI is stable. The radiation outputs change considerably with the preset parameters. Parameters should be optimally chosen to reduce the patient dose.
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