Takalo Reijo, Hytti Heli, Ihalainen Heimo, Sohlberg Antti
Division of Nuclear Medicine, Department of Diagnostic Radiology, Oulu University Hospital (OYS), P.O. Box 500, 90029 Oulu, Finland.
Department of Automation Science and Engineering, Tampere University of Technology, P.O. Box 692, 33101 Tampere, Finland.
Comput Math Methods Med. 2015;2015:494691. doi: 10.1155/2015/494691. Epub 2015 May 18.
This paper presents improved autoregressive modelling (AR) to reduce noise in SPECT images. An AR filter was applied to prefilter projection images and postfilter ordered subset expectation maximisation (OSEM) reconstruction images (AR-OSEM-AR method). The performance of this method was compared with filtered back projection (FBP) preceded by Butterworth filtering (BW-FBP method) and the OSEM reconstruction method followed by Butterworth filtering (OSEM-BW method). A mathematical cylinder phantom was used for the study. It consisted of hot and cold objects. The tests were performed using three simulated SPECT datasets. Image quality was assessed by means of the percentage contrast resolution (CR%) and the full width at half maximum (FWHM) of the line spread functions of the cylinders. The BW-FBP method showed the highest CR% values and the AR-OSEM-AR method gave the lowest CR% values for cold stacks. In the analysis of hot stacks, the BW-FBP method had higher CR% values than the OSEM-BW method. The BW-FBP method exhibited the lowest FWHM values for cold stacks and the AR-OSEM-AR method for hot stacks. In conclusion, the AR-OSEM-AR method is a feasible way to remove noise from SPECT images. It has good spatial resolution for hot objects.
本文提出了改进的自回归建模（AR）方法以降低单光子发射计算机断层扫描（SPECT）图像中的噪声。将AR滤波器应用于预滤波投影图像和后滤波有序子集期望最大化（OSEM）重建图像（AR - OSEM - AR方法）。将该方法的性能与巴特沃斯滤波（BW）预处理后的滤波反投影（FBP）（BW - FBP方法）以及OSEM重建方法后接巴特沃斯滤波（OSEM - BW方法）进行了比较。使用数学圆柱体模型进行研究。它由热物体和冷物体组成。使用三个模拟的SPECT数据集进行测试。通过圆柱体线扩展函数的对比度分辨率百分比（CR%）和半高宽（FWHM）来评估图像质量。对于冷堆，BW - FBP方法显示出最高的CR%值，而AR - OSEM - AR方法给出最低的CR%值。在热堆分析中，BW - FBP方法的CR%值高于OSEM - BW方法。对于冷堆，BW - FBP方法表现出最低的FWHM值，对于热堆，AR - OSEM - AR方法表现出最低的FWHM值。总之，AR - OSEM - AR方法是去除SPECT图像噪声的一种可行方法。它对热物体具有良好的空间分辨率。
