摘要
目的通过实验来探讨多层螺旋CT的重组图像空间分辨率与扫描时所用螺距的关系,以便为优化设置扫描方案提供可靠的理论基础。方法在多台多层螺旋CT机上,应用不同螺距扫描线对测试模块,并将各种不同扫描方案的扫描数据重建为层厚、间距均为0.625 mm的轴位像(axial image),以轴位像为基本元素重新组合为新的平面图像,即多平面重组(MPR)。采用相同的窗宽(window width)、窗位(window level)显示各种不同扫描方案的MPR图像,鉴别线对测试模块的线径粗细级别,也就是在同一窗宽、窗位情况下对各组多平面重组图像空间分辨率进行评价。结果螺距Pitch&Speed(mm/rot)为0.531:1、10.62扫描的MPR图像可显示6个级别粗细的线径,对应的线对数是0.45 mm(11 LP/cm);而螺距Pitch&Speed(mm/rot)为1.375:1、27.50扫描的MPR图像只可显示4个级别的粗细的线径,对应的线对数是0.55 mm(9LP/cm);两种扫描方式的MPR图像空间分辨率差别明显。结论在使用对称型排列探测器的多层螺旋CT机时,如果加大扫描螺距,会使重组图像噪声增大,空间分辨率降低,图像质量变差。所以在患者清醒和配合良好又不要求高时间分辨率的情况下,要把扫描方案中的螺距因子尽量设为≤1或小螺距,减少大螺距对MPR图像空间分辨率的影响。
【Objective】To explore experimentally the relationship between MSCT restructuring spatial resolution and the scan pitch, in order to provide a theoretical basis of scan program optimization settings. 【Methods】Application of multiple MSCT, scan lines with different pitches to the test module, and reconstruct a variety of different scanning program scan data for thickness, axial images are 0.625 mm, and axial images as the basic element regroup for a new flat image, which is multi-planar reformation（MPR）. MPR displayed various different scanning programs with the same window width, window level. That is each group MPR spatial resolution evaluated in the same window width and the same window level.【Results】There are 6 levels of the wire diameter can display at pitch speed（mm/rot）） is 0.531：1、10.62,but there are 4 levels of the wire diameter can display at pitch speed（mm/rot）） is1.375：1、27.50.corresponding the number or linepair is 0.55mm（9LP/cm）. The restructuring spatial resolution of MPR is clear different between these two scan methods. 【Conclusion】The reconstructed pattem noise increase, the spatial resolution reduction, image quality variation will occur when the scanning pitch enlarged in Symmetric array detector MSCT using. So in the case patients awake and not requiring the high time resolution, make as far as possible the pitch factor ≤ 1 or small pitch, to reduce the impact of big pitch for MPR spatial resolution.
出处
《中国医学工程》
2015年第8期18-19,共2页
China Medical Engineering
关键词
重组
螺距
空间分辨率
线对
重叠重建
reformation
pitch
spatial resolution
linepair
overlap reconstruction
