SPECT成像空间分辨率的测量与评价

作者使用ＳＰＥＣＴ性能体模和ＮＥＭＡ三线源分辨体模等标准化仪器，对一台日本进口的ＳＰＥＣＴ设备进行了空间分辨率测量。基本方法是对采集的线源平面影像和断层影像取计数分布曲线（ｐｒｏｆｉｌｅ）并求出半高宽（ＦＷＨＭ），即以线源失锐值作为空间分辨率定量。结果表明：（１）平面分辨率合格但未达到标称值；（２）散射媒质的影响是空间分辨率下降的原因；（３）偏心线源断层影像具有几何非对称性，径向半高宽大于切向半高宽，而且两者的差值呈现各向异性；（４）断层分辨率随探头旋转半径的增大而下降．把圆轨道改为椭圆轨道，可以改善空间分辨率；（５）断层扫描时，冷灶影像的分辨率优于热灶影像，等等。本文对测量结果进行分析，并参照现行标准作出评价。

MEASUREMENT AND EVALUATION OF SPATIAL RESOLUTOIN IN SPECT IMAGING

A SPECT unit imported from Japan was conducted a list of tests on Spatial resolution(SR)bymeans of standardized equipments,including SPECT performance phantom and NEMA resolution phantom;et al.The method was basically to take profile curves and measure their FWHMs in acquired planar images and tomo-graphic images of line sources,i.e.the values of sharpness of line sources are used as quantitation of SR.Themeasutment results indicated:(1)The planar SR was acceptable but not as good as the nominal value;(2)Theihfluehce of scattering mediem is a cause of dealine in SR;(3)In tomographic images the off-axis sources werefound to asymmetric in geometry,i.e,the radial FWHM>the tangential FWHM,and the difference of these twoFWHMs is anisotropis;(4)SR is degrated with the increase in rotation radius,it can be improved if there is achange in orbit from circle to ellipse;(5)SR measured in a cold lesion image is superior to that in a hot lesion im-age.This paper analyses the measurement results and provides evaluation according to some current criteria andstandards.