Vosoughi Habibeh, Momennezhad Mehdi, Emami Farshad, Hajizadeh Mohsen, Rahmim Arman, Geramifar Parham
Department of Medical Physics, Mashhad University of Medical Science, Mashhad, Iran.
Nuclear Medicine Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Quant Imaging Med Surg. 2023 Apr 1;13(4):2218-2233. doi: 10.21037/qims-22-443. Epub 2023 Feb 8.
Harmonization methods reduce variability between different make and models of positron emission tomography (PET) scanners. The study aims to explore harmonization strategies that lead to comparable and robust quantitative metrics in a multicenter setting.
NEMA IEC Phantom data acquisition was performed for low and high spheres-to-background ratios (SBR4:1 and 10:1) on six PET/CT (computed tomography) scanners. Different reconstruction sets, including the number of sub-iterations, number of subsets, and full width at half maximum (FWHM) for each scanner, were evaluated towards optimized and harmonized reconstruction settings. Recovery coefficients (RCs) of four quantitative metrics, including standardized uptake value (SUV), SUV (SUV in 50% isocontour), SUV, and mean uptake of 10 highest concentration voxels were evaluated as RC, RC, RC, and RC, representing percent difference relative to the static ground truth case as functions of sphere sizes. A set of image reconstruction parameters was proposed for harmonized reconstruction to minimize variability between scanners. The root mean square error (RMSE), curvature, and reproducibility were examined. The proposed reconstruction protocols for harmonization and standard clinical reconstruction settings were compared to each other across all scanners.
A significant difference (P value <0.0001) was observed in the aforementioned quantitative metrics between SBR10 and SBR4. Reconstruction parameter sets with the smallest RMSE and RC values within 10% bias were identified as the best candidate for harmonization. The coefficient of variation of the mean value of RCs (CV) shows a remarkable reduction of about 28%, 26%, 32%, and 19% in harmonized reconstruction settings for MRC, MRC, MRC, and MRC, respectively. CV for MRC in the harmonized reconstruction setting was 5.9% in SBR4, while the smallest value in SBR10 belongs to MRC with a value of 5.8%. The reproducibility of RC is improved by deriving the value from ten hottest voxels and is equally reproducible with RC. Compared to RC and RC, the variability is reduced by 18% and 22% if ten voxels are pooled.
Harmonizing PET/CT systems with and without point spread function/time of flight (PSF/TOF) using various vendor-developed image reconstruction algorithms improves the quantification reproducibility. RC, likewise RC, is superior to the rest of the quantitative indices in terms of accuracy and reproducibility and helpful in quantifying lesion volume below 1 mL.
归一化方法可减少不同品牌和型号的正电子发射断层扫描（PET）扫描仪之间的差异。本研究旨在探索在多中心环境中实现可比且稳健的定量指标的归一化策略。
在六台PET/CT（计算机断层扫描）扫描仪上，针对低和高球与背景比值（SBR4:1和10:1）进行了NEMA IEC体模数据采集。对不同的重建参数集进行评估，包括每个扫描仪的子迭代次数、子集数量和半高宽（FWHM），以实现优化和归一化的重建设置。评估了四个定量指标的恢复系数（RC），包括标准化摄取值（SUV）、SUV（50%等轮廓线处的SUV）、SUV以及10个最高浓度体素的平均摄取量，分别表示为RC、RC、RC和RC，即相对于静态真实情况的百分比差异作为球体大小的函数。提出了一组用于归一化重建的图像重建参数，以最小化扫描仪之间的差异。检查了均方根误差（RMSE）、曲率和可重复性。在所有扫描仪之间比较了用于归一化的建议重建协议和标准临床重建设置。
在上述定量指标中，观察到SBR10和SBR4之间存在显著差异（P值<0.0001）。在偏差10%以内，RMSE和RC值最小的重建参数集被确定为归一化的最佳候选方案。在归一化重建设置中，MRC、MRC、MRC和MRC的RC平均值的变异系数（CV）分别显著降低了约28%、26%、32%和19%。在SBR4的归一化重建设置中，MRC的CV为5.9%，而在SBR10中最小值属于MRC，值为5.8%。通过从十个最热体素中得出RC值，其可重复性得到改善，并且与RC具有同等的可重复性。与RC和RC相比，如果合并十个体素，变异性降低了18%和22%。
使用各种供应商开发的图像重建算法对具有和不具有点扩散函数/飞行时间（PSF/TOF）的PET/CT系统进行归一化，可提高定量的可重复性。RC以及RC在准确性和可重复性方面优于其他定量指标，有助于量化小于1 mL的病变体积。
