Department of Radiology, University of Southern California, Los Angeles, CA.
Clin Nucl Med. 2018 Nov;43(11):811-814. doi: 10.1097/RLU.0000000000002284.
Current PET/CT lutetium oxyorthosilicate (LSO) or lutetium-yttrium oxyorthosilicate crystal scanners are equipped with sophisticated softwares including point-spread function (PSF) and time-of-flight (TOF) image reconstruction. These softwares are associated with increased SUVs compared with 3D-OSEM reconstructions associated with older BGO PET/CT scanners. The European Association of Nuclear Medicine (EANM) identified the problem of SUV harmonization since 2010 through the EANM Research Ltd European Association of Nuclear Medicine Research Ltd [EARL] FDG PET/CT accreditation program. This required processing 2 reconstructions, one optimized for maximum spatial lesion detection and one for harmonized quantitation. We investigated an alternative single reconstruction method for both qualitative and quantitative analysis optimized to maximize spatial lesion detectability, followed by an intrinsic postreconstruction algorithm for SUV harmonization.
Phantom and "in vivo" patient data analysis were acquired and analyzed on (a) a Siemens Biograph mCT system with LSO crystals and PSF and TOF algorithms, and on (b) a General Electric Discovery STE system with BGO crystals, without PSF and TOF. A dedicated algorithm (EQ.filter) was tested to harmonize SUV between the 2 scanners compared with EANM/EARL specifications. NEMA IQ phantom and a Jaszczak cylindrical phantom equipped with small fillable spheres (lesion to background ratios of 8:1 and 4:1) were used. Phantom data were validated on 7 oncologic patients with 39 hyperactive lesions ranging from 3 mm to 26 mm.
The main benefit of PSF + TOF LSO PET/CT systems was increased contrast for small active lesions. Recovery coefficients measured according to NEMA standards exceeded those obtained by 3D-OSEM reconstruction. SUVmax discrepancies between the 2 PET/CT systems were as high as 149%, dropping to below 10% when optimized by EQ.filter.
A single reconstruction optimized by EQ.filter for maximum spatial lesion detectability is an easy and precise solution to harmonize SUVs between different PET/CT scanners, avoiding a second reconstruction with an additional smoothing filter as requested by EANM/EARL.
目前配备有镥氧钇正硅酸盐（LSO）或硅酸镥正硅酸盐晶体的正电子发射断层扫描/计算机断层扫描（PET/CT）扫描仪均配备有复杂的软件，包括点扩展函数（PSF）和飞行时间（TOF）图像重建。与较旧的锗酸铋（BGO）PET/CT 扫描仪相关联的三维有序子集期望最大化（3D-OSEM）重建相比，这些软件与更高的标准摄取值（SUV）相关联。自 2010 年以来，欧洲核医学协会（EANM）通过 EANM 研究有限公司（EANM Research Ltd）[EARL]FDG PET/CT 认证计划，已经确定了 SUV 协调的问题。这需要处理 2 个重建，一个优化用于最大空间病变检测，一个用于协调定量。我们研究了一种替代的单重建方法，用于定性和定量分析，优化用于最大程度地提高空间病变检测能力，然后对 SUV 进行内在的重建后算法协调。
在配备有 PSF 和 TOF 算法的 LSO 晶体的西门子 Biograph mCT 系统（a）和配备有 BGO 晶体、没有 PSF 和 TOF 的通用电气 Discovery STE 系统（b）上，获取和分析了体模和“体内”患者数据。测试了专用算法（EQ.filter）以根据 EANM/EARL 规范在 2 个扫描仪之间协调 SUV。使用 NEMA IQ 体模和配备有可填充小球的 Jaszczak 圆柱形体模（病变与背景比为 8:1 和 4:1）。对 7 名患有 39 个活性病变（范围为 3 毫米至 26 毫米）的肿瘤患者进行了体模数据验证。
PSF + TOF LSO PET/CT 系统的主要优势是对小活性病变的对比度增加。根据 NEMA 标准测量的恢复系数高于 3D-OSEM 重建的恢复系数。2 个 PET/CT 系统之间的 SUVmax 差异高达 149%，通过 EQ.filter 优化后降至 10%以下。
EQ.filter 优化的单重建用于最大程度地提高空间病变检测能力，是一种在不同的 PET/CT 扫描仪之间协调 SUV 的简单而精确的解决方案，避免了按照 EANM/EARL 的要求进行第二次重建并增加额外的平滑滤波器。
