Department of Medical Physics, School of Medicine, University of Patras, Patras 26504, Greece; Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation, Academy of Athens (BRFAA), Athens 11527, Greece.
Mathematics Research Center, Academy of Athens, Athens 11527, Greece; Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, National Center for Scientific Research "Demokritos", 15341 Athens, Greece.
Comput Methods Programs Biomed. 2022 Apr;217:106668. doi: 10.1016/j.cmpb.2022.106668. Epub 2022 Feb 1.
The Spline Reconstruction Technique (SRT) is a fast algorithm based on a novel numerical implementation of an analytic representation of the inverse Radon transform. The purpose of this study is to provide a comparison between SRT, Filtered Back-Projection (FBP), Ordered Subset Expectation Maximization 2D (2D-OSEM), and the Tera-Tomo 3D algorithm, using phantom data at various acquisition durations as well as small-animal data obtained from the Mediso nanoScan® PET/CT scanner.
For this purpose, the "NEMA NU 4-2008 standards" protocol was employed at five different realizations and acquisition durations. In addition to the image quality metrics described by the NEMA protocol, Cold Region Contrast was also considered as a figure-of-merit. Furthermore, Cold Region Contrast was measured in the myocardial infarction region of six male Wistar rats. The volumetric defect quantification was assessed with dedicated computer software. Lastly, plots of Recovery Coefficient and Spill-Over Ratio as a function of the Percentage Standard Deviation were generated, after smoothing the phantom reconstructions with four different Gaussian filters. Statistical significance was determined by employing the Kruskal-Wallis test or One-way Analysis of Variance depending on the normality of the variable's distribution.
The present study revealed that, at the expense of slightly increased noise in the reconstructed images, SRT resulted in higher Recovery Coefficient values for small hot regions of interest, when compared with FBP and 2D-OSEM at all acquisition durations. Furthermore, SRT reconstructed images exhibit higher Recovery Coefficient values, for all hot regions of interest, when compared to the other 2D algorithms at short acquisition durations. In both phantom and animal studies, SRT achieved a significant improvement over 2D-OSEM for the Spill-Over Ratio and the Cold Region Contrast. These advantages were maintained even after comparing the algorithms at equal noise levels. The Tera-Tomo 3D algorithm (4 subsets, iterations≥ 13) performed significantly better compared to the other algorithms for all figures-of-merit. No statistically significant differences regarding the myocardial defect size were observed between the algorithms investigated.
Overall, SRT appears that could be useful for the quantification of small hot regions of interest, cold regions of interest, as well as in low-count imaging applications.
Spline 重建技术（SRT）是一种快速算法，基于对逆 Radon 变换的分析表示的新数值实现。本研究的目的是通过在不同采集时间的体模数据以及从 Mediso nanoScan® PET/CT 扫描仪获得的小动物数据，对 SRT、滤波反投影（FBP）、有序子集期望最大化 2D（2D-OSEM）和 Tera-Tomo 3D 算法进行比较。
为此，使用了五个不同的实现和采集时间的“NEMA NU 4-2008 标准”协议。除了 NEMA 协议中描述的图像质量指标外，冷区对比度也被认为是一种性能指标。此外，还在六只雄性 Wistar 大鼠的心肌梗死区域测量了冷区对比度。使用专用计算机软件评估容积缺陷定量。最后，通过对体模重建进行四种不同的高斯滤波平滑处理，生成恢复系数和溢出比与标准偏差百分比的函数图。根据变量分布的正态性，采用 Kruskal-Wallis 检验或单因素方差分析确定统计学意义。
本研究表明，在所有采集时间下，与 FBP 和 2D-OSEM 相比，SRT 会导致重建图像中的噪声略有增加，但会导致小的感兴趣的热点区域的恢复系数值更高。此外，在短采集时间下，与其他 2D 算法相比，SRT 重建图像在所有热点区域都具有更高的恢复系数值。在体模和动物研究中，SRT 与 2D-OSEM 相比，在溢出比和冷区对比度方面都取得了显著的改善。即使在比较算法的等效噪声水平时，这些优势仍然存在。对于所有性能指标，Tera-Tomo 3D 算法（4 个子集，迭代次数≥13）的表现明显优于其他算法。在所研究的算法中，心肌缺陷大小没有观察到统计学上的显著差异。
总体而言，SRT 似乎可用于对小的感兴趣的热点区域、冷区以及低计数成像应用进行定量分析。
