注入剂量和滤波函数取值对门控心肌灌注显像定量测定结果的影响

目的:评估注射放射性药物99TcmO4-剂量和图像重建时滤波函数参数大小对门控心肌灌注断层显像(G-SPECT)测定准确性的影响.方法:应用心脏模型评估剂量大小和滤波函数中不同截止频率(fc)对左室壁及左心腔容量测定结果的影响.心脏模型室壁腔内注射放射性99TcmO4-溶液,其活度分别为50MBq和10MBq,截止频率由高到低,分别选择0.75～0.20(间隔0.05);陡度因子均为5.应用门控心肌定量测定软件自动计算左室心腔大小及左室心肌量.结果:在截止频率选择相同时,注入大剂量所测定左室心腔容量小于小剂量测定值;左室壁测定值大于小剂量测定值.在截止频率选择0.45时,大剂量所测定左室心腔容量和左室壁心肌量值最接近模型值.随截止频率减少,左室壁增厚,左室心腔缩小,左室壁心肌量增加.左室心腔容量改变大于左室壁心肌量改变.在fc值设置在0.35～0.65时,左室容量测定结果相对变化平稳.结论:应用门控心肌定量软件测定左室功能主要依赖左室边界的确定.为保证临床应用G-SPECT测定的准确性和可比性,应在足够的采集计数的同时,选择合适的图像重建参数.

Assessment the accuracy of gated SPECT with different filtered function evaluation and radioactivity doses on myocardial phantom

Objective:To assesse the accuracy and reproducibility of gated SPECT with different filtered function evaluation and radioactivity doses on myocardial phantom.Methods:The myocardial phantoms were filled with 50 MBq and 10 MBq of 99TcmO4-solution separately.The projection data were processed with varied critical frequencies from 0.20 to 0.75.Left ventricular(LV)cavity and LV volume were calculated automatically using QGS software.Results:When the radioactivity dose increased,the estimated LV volume was larger and LV cavity volume was smaller than the lower dose.During the larger dose and critical frequency selected in 0.45 cycles/cm,the values of measured LV volume and LV cavity volume were mostly close to the actual values of the myocardial phantom.As the critical frequency decreased,the estimated LV volume increased and LV cavity volume decreased.When critical frequencies selected between 0.35-0.65 cycles/cm,the estimated LV volume and LV cavity volume reached a plateau.Conclusion:The accuracy and reproducibility of LV measurements using QGS depend on the critical frequency of pre-reconstruction filters and injected radioactivity dose.