摘要
目的:采用客观方法测定多层CT在不同螺距扫描时的z轴空间分辨率,分析多层CT的螺距对z轴空间分辨率的影响。方法:应用螺旋CT层敏感度曲线测试模体分别测试GE Light Speed 16层、Somatom Cardiac 16层和Soma-tom Sensation 64层三种CT的z轴空间分辨率。采用腹部模式,0.1mm重建间隔重建图像。GE Light Speed 16层CT扫描参数:准直宽度0.625mm×16,重建层厚0.625mm,螺距分别为0.562、0.938、1.375、1.75。Somatom Cardiac 16层CT扫描参数:准直宽度0.75mm×16,重建层厚0.75mm,螺距分别为0.5、0.75、1.0、1.25、1.5。Somatom Sensation 64层CT扫描参数:准直宽度0.6mm×32,重建层厚0.6mm,螺距分别为0.5、0.75、1.0、1.25、1.5。测定出各机型不同螺距的调制传递函数(MTF),在各条MTF曲线上测试出相对信号强度2%的空间分辨率。结果:在各MTF曲线上测试的相对信号强度2%的空间分辨率,GE Light Speed 16层CT在螺距为0.562、0.938、1.375、1.75时的测定值分别是14.3、11.4、11.41、1.1 LP/cm,Somatom Cardiac 16层CT在螺距为0.5、0.75、1.0、1.25、1.5时的测定值分别是10.6、11.3、9.5、9.7、9.5 LP/cm,Somatom Sensation 64层CT在螺距为0.5、0.75、1.0、1.25、1.5时的测定值分别是15.5、15.6、15.5、15.61、5.5 LP/cm。结论:多层CT的z轴空间分辨率受螺距的影响比较小,且与采用的锥形角校正重建算法有关。对于16层CT,如欲获得最大的z轴空间分辨率,需选择最佳螺距。
Objective：To measure z-direction spatial resolution for multislice spiral CT systems using different pitch and to study the relativity of pitch and z-direction spatial resolution.Methods：Using the same CT technique and body protocol as those used for clinical CT,slice sensitivity profile（SSP） phantom was scanned repectively employing three CT systems,which were GE light speed 16-slice CT system,Somatom Cardiac 16-slice CT system,and Somatom Sensation 64-slice CT system.The default parameters were used for each CT system except those ones as follows： the thinnest slice width,0.1mm reconstruction increment,and different pitchs.Then,Spiral SSPs were got and transformed into MTFs by Fourier transform.Results：The measured z-direction spatial resolution was 14.3,11.4,11.4,11.1 LP/cm at pitch=0.562,0.938,1.375,and 1.75 for GE light speed 16-slice CT system respectively at 2% MTF with MTF curve.That was 10.6,11.3,9.5,9.7,and 9.5 LP/cm for Somatom Cardiac 16-slice CT system,while 15.5,15.6,15.5,15.6,and 15.5 LP/cm for Somatom Sensation 64-slice CT system at pitch=0.5,0.75,1.0,1.25,and 1.5 respectively at 2% MTF with MTF curve.Conclusion：The z-direction spatial resolution can be scarcely affected by pitch for multi-slice spiral CT systems,especially for 64-slice CT system. In addition,it can be influenced by cone beam reconstruction angorithm adopted in CT system.
出处
《医学影像学杂志》
2010年第10期1559-1561,共3页
Journal of Medical Imaging
