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Variability in lutetium-177 SPECT quantification between different state-of-the-art SPECT/CT systems.
EJNMMI Physics ( IF 4 ) Pub Date : 2020-02-11 , DOI: 10.1186/s40658-020-0278-3
Steffie M B Peters 1 , Sebastiaan L Meyer Viol 2 , Niels R van der Werf 3 , Nick de Jong 4 , Floris H P van Velden 4 , Antoi Meeuwis 1 , Mark W Konijnenberg 3 , Martin Gotthardt 1 , Hugo W A M de Jong 2 , Marcel Segbers 3
Affiliation  

Quantitative SPECT imaging in targeted radionuclide therapy with lutetium-177 holds great potential for individualized treatment based on dose assessment. The establishment of dose-effect relations requires a standardized method for SPECT quantification. The purpose of this multi-center study is to evaluate quantitative accuracy and inter-system variations of different SPECT/CT systems with corresponding commercially available quantitative reconstruction algorithms. This is an important step towards a vendor-independent standard for quantitative lutetium-177 SPECT. Four state-of-the-art SPECT/CT systems were included: Discovery™ NM/CT 670Pro (GE Healthcare), Symbia Intevo™, and two Symbia™ T16 (Siemens Healthineers). Quantitative accuracy and inter-system variations were evaluated by repeatedly scanning a cylindrical phantom with 6 spherical inserts (0.5 – 113 ml). A sphere-to-background activity concentration ratio of 10:1 was used. Acquisition settings were standardized: medium energy collimator, body contour trajectory, photon energy window of 208 keV (± 10%), adjacent 20% lower scatter window, 2 × 64 projections, 128 × 128 matrix size, and 40 s projection time. Reconstructions were performed using GE Evolution with Q.Metrix™, Siemens xSPECT Quant™, Siemens Broad Quantification™ or Siemens Flash3D™ algorithms using vendor recommended settings. In addition, projection data were reconstructed using Hermes SUV SPECT™ with standardized reconstruction settings to obtain a vendor-neutral quantitative reconstruction for all systems. Volumes of interest (VOI) for the spheres were obtained by applying a 50% threshold of the sphere maximum voxel value corrected for background activity. For each sphere, the mean and maximum recovery coefficient (RCmean and RCmax) of three repeated measurements was calculated, defined as the imaged activity concentration divided by the actual activity concentration. Inter-system variations were defined as the range of RC over all systems. RC decreased with decreasing sphere volume. Inter-system variations with vendor-specific reconstructions were between 0.06 and 0.41 for RCmean depending on sphere size (maximum 118% quantification difference), and improved to 0.02–0.19 with vendor-neutral reconstructions (maximum 38% quantification difference). This study shows that eliminating sources of possible variation drastically reduces inter-system variation in quantification. This means that absolute SPECT quantification for 177Lu is feasible in a multi-center and multi-vendor setting; however, close agreement between vendors and sites is key for multi-center dosimetry and quantitative biomarker studies.

中文翻译:

不同最先进 SPECT/CT 系统之间 lutetium-177 SPECT 量化的差异。

使用 lutetium-177 进行靶向放射性核素治疗的定量 SPECT 成像具有基于剂量评估的个体化治疗的巨大潜力。剂量效应关系的建立需要标准化的 SPECT 量化方法。这项多中心研究的目的是使用相应的商用定量重建算法评估不同 SPECT/CT 系统的定量准确性和系统间变化。这是迈向独立于供应商的定量 lutetium-177 SPECT 标准的重要一步。包括四个最先进的 SPECT/CT 系统:Discovery™ NM/CT 670Pro(GE Healthcare)、Symbia Intevo™ 和两个 Symbia™ T16(Siemens Healthineers)。通过重复扫描带有 6 个球形插入物(0.5 – 113 ml)的圆柱形体模来评估定量准确性和系统间变化。使用 10:1 的球体与背景活动浓度比。采集设置标准化:中等能量准直器、身体轮廓轨迹、208 keV (± 10%) 的光子能量窗口、相邻的 20% 下散射窗口、2 × 64 投影、128 × 128 矩阵大小和 40 s 投影时间。使用 GE Evolution with Q.Metrix™、Siemens xSPECT Quant™、Siemens Broad Quantification™ 或 Siemens Flash3D™ 算法使用供应商推荐的设置进行重建。此外,投影数据是使用 Hermes SUV SPECT™ 和标准化重建设置重建的,以获得所有系统的供应商中立的定量重建。通过应用针对背景活动校正的球体最大体素值的 50% 阈值,获得球体的感兴趣体积 (VOI)。对于每个球体,计算了三个重复测量的平均和最大恢复系数(RCmean 和 RCmax),定义为成像活动浓度除以实际活动浓度。系统间差异被定义为所有系统的 RC 范围。RC 随球体体积的减小而减小。根据球体大小(最大 118% 量化差异),RCmean 与供应商特定重建的系统间差异在 0.06 和 0.41 之间,并通过供应商中立重建(最大 38% 量化差异)改进到 0.02–0.19。这项研究表明,消除可能变异的来源可以大大减少量化中的系统间变异。这意味着 177Lu 的绝对 SPECT 量化在多中心和多供应商环境中是可行的;然而,供应商和站点之间的密切协议是多中心剂量测定和定量生物标志物研究的关键。
更新日期:2020-02-11
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