Faculty of Medicine and Health, University of Sydney, Sydney, Australia.
Department of Radiological sciences, College of Applied Medical Science, Najran University, Najran, Saudi Arabia.
J Appl Clin Med Phys. 2022 Apr;23(4):e13528. doi: 10.1002/acm2.13528. Epub 2022 Jan 20.
Investigate the impact of acquisition time and reconstruction parameters on single-photon emission computed tomography/computed tomography (SPECT/CT) image quality with the ultimate aim of finding the shortest possible acquisition time for clinical whole-body SPECT/CT (WB-SPECT/CT) while maintaining image quality METHODS: The National Electrical Manufacturers Association (NEMA) image quality measurements were performed on a SPECT/CT imaging system using a NEMA International Electrotechnical Commission (IEC) phantom with spherical inserts of varying diameter (10-37 mm), filled with Tc in activity sphere-to-background concentration ratio of 8.5:1. A gated acquisition was acquired and binned data were summed to simulate acquisitions of 15, 8, and 3 s per projection angle. Images were reconstructed on a Hermes (HERMES Medical Solutions AB, Stockholm, Sweden) workstation using eight subsets and between 4 and 24 iterations of the three-dimensional (3D) ordered subset expectation maximization (OSEM) algorithm. Reconstructed images were post-smoothed with 3D Gaussian filter ranging from 0 to 12 mm full-width at half maximum (FWHM). Contrast recovery, background variability, and contrast-to-noise ratio were evaluated RESULTS: As expected, the spheres were more clearly defined as acquisition time and count statistics improved. The optimal iteration number and Gaussian filter were determined from the contrast recovery convergence and level of noise. Convergence of contrast recovery was observed at eight iterations while 12 iterations yielded stabilized values at all acquisition times. In addition, it was observed that applying 3D Gaussian filter of 8-12 mm FWHM suppressed the noise and mitigated Gibbs artifacts. Background variability was larger for small spheres than larger spheres and the noise decreased when acquisition time became longer. A contrast-to-noise ratio >5 was reached for the two smallest spheres of 10 and 13 mm at acquisition times of 8 s CONCLUSION: Optimized reconstruction parameters preserved image quality with reduce acquisition time in present study. This study suggests an optimal protocol for clinical Tc SPECT/CT can be reached at 8 s per projection angle, with data reconstructed using 12 iterations and eight subset of the 3D OSEM algorithm and 8 mm Gaussian post-filter.
研究采集时间和重建参数对单光子发射计算机断层扫描/计算机断层扫描（SPECT/CT）图像质量的影响，最终目的是在保持图像质量的同时，找到临床全身 SPECT/CT（WB-SPECT/CT）最短的采集时间。
使用具有不同直径（10-37 毫米）的球形插件的 NEMA 国际电工委员会（IEC）体模，在 SPECT/CT 成像系统上进行 NEMA 图像质量测量，这些插件充满了 Tc，活性球体与背景的浓度比为 8.5:1。采集门控采集，对 bin 数据进行求和，模拟每个投影角采集 15、8 和 3 秒。使用八个子集和三维（3D）有序子集期望最大化（OSEM）算法的 4 到 24 次迭代在 Hermes（HERMES Medical Solutions AB，斯德哥尔摩，瑞典）工作站上重建图像。重建后的图像使用 3D 高斯滤波器进行后平滑处理，滤波器的半峰全宽（FWHM）为 0 至 12 毫米。评估对比恢复、背景变化和对比噪声比。
正如预期的那样，随着采集时间和计数统计的改善，球体的定义更加清晰。从对比恢复的收敛性和噪声水平确定了最佳的迭代次数和高斯滤波器。在八次迭代时观察到对比恢复的收敛，而在所有采集时间下，十二次迭代均产生稳定值。此外，观察到应用 3D 高斯滤波器（FWHM 为 8-12 毫米）可以抑制噪声并减轻 Gibbs 伪影。与较大球体相比，小球体的背景变化更大，当采集时间变长时，噪声减小。在 8 秒的采集时间下，两个最小的 10 毫米和 13 毫米球体的对比噪声比达到了>5。
在本研究中，优化的重建参数在减少采集时间的同时保留了图像质量。本研究表明，对于临床 Tc SPECT/CT，可以达到 8 秒/投影角的最佳协议，使用 12 次迭代和 3D OSEM 算法的 8 个子集以及 8 毫米高斯后置滤波器重建数据。
