Absolute quantification of radiotracer distribution using SPECT/CT imaging is of great importance for dosimetry aimed at personalized radionuclide precision treatment. However, its accuracy depends on many factors. Using phantom measurements, this multi-vendor and multi-center study evaluates the quantitative accuracy and inter-system variability of various SPECT/CT systems as well as the effect of patient size, processing software and reconstruction algorithms on recovery coefficients (RC). Five SPECT/CT systems were included: Discovery™ NM/CT 670 Pro (GE Healthcare), Precedence™ 6 (Philips Healthcare), Symbia Intevo™, and Symbia™ T16 (twice) (Siemens Healthineers). Three phantoms were used based on the NEMA IEC body phantom without lung insert simulating body mass indexes (BMI) of 25, 28, and 47 kg/m2. Six spheres (0.5–26.5 mL) and background were filled with 0.1 and 0.01 MBq/mL 99mTc-pertechnetate, respectively. Volumes of interest (VOI) of spheres were obtained by a region growing technique using a 50% threshold of the maximum voxel value corrected for background activity. RC, defined as imaged activity concentration divided by actual activity concentration, were determined for maximum (RCmax) and mean voxel value (RCmean) in the VOI for each sphere diameter. Inter-system variability was expressed as median absolute deviation (MAD) of RC. Acquisition settings were standardized. Images were reconstructed using vendor-specific 3D iterative reconstruction algorithms with institute-specific settings used in clinical practice and processed using a standardized, in-house developed processing tool based on the SimpleITK framework. Additionally, all data were reconstructed with a vendor-neutral reconstruction algorithm (Hybrid Recon™; Hermes Medical Solutions). RC decreased with decreasing sphere diameter for each system. Inter-system variability (MAD) was 16 and 17% for RCmean and RCmax, respectively. Standardized reconstruction decreased this variability to 4 and 5%. High BMI hampers quantification of small lesions (< 10 ml). Absolute SPECT quantification in a multi-center and multi-vendor setting is feasible, especially when reconstruction protocols are standardized, paving the way for a standard for absolute quantitative SPECT.

中文翻译：

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迈向绝对SPECT / CT量化的标准化：多中心，多供应商的幻像研究

使用SPECT / CT成像对放射性示踪剂分布进行绝对定量，对于针对个性化放射性核素精密治疗的剂量学非常重要。但是，其准确性取决于许多因素。该多厂商，多中心的研究使用幻像测量来评估各种SPECT / CT系统的定量准确性和系统间可变性，以及患者规模，处理软件和重建算法对恢复系数（RC）的影响。包括五个SPECT / CT系统：Discovery™NM / CT 670 Pro（GE Healthcare），Precedence™6（Philips Healthcare），Symbia Intevo™和Symbia™T16（两次）（Siemens Healthineers）。根据NEMA IEC人体模型使用了三个体模，没有肺插入物模拟体重指数（BMI）为25、28和47 kg / m2。六个球体（0.5–26。5 mL）和背景分别充满0.1 MB和0.01 MBq / mL 99mTc-高tech酸盐。通过区域生长技术，使用针对背景活性校正的最大体素值的50％阈值获得球体的目标体积（VOI）。对于每个球体直径，确定VOI中的最大值（RCmax）和平均体素值（RCmean），将RC定义为成像的活动浓度除以实际活动浓度。系统间可变性表示为RC的中值绝对偏差（MAD）。采集设置标准化。使用特定于供应商的3D迭代重建算法重建图像，并在临床实践中使用特定于研究所的设置，并使用基于SimpleITK框架的标准化，内部开发的处理工具进行处理。另外，所有数据均使用与供应商无关的重建算法（Hybrid Recon™； Hermes Medical Solutions）进行重建。每个系统的RC随球体直径的减小而减小。RCmean和RCmax的系统间变异性（MAD）分别为16％和17％。标准化重建将这种变异性降低到4％和5％。高BMI妨碍了小病变（<10 ml）的定量。在多中心和多供应商的环境中进行绝对SPECT定量分析是可行的，尤其是在标准化重组协议的情况下，这为绝对定量SPECT标准奠定了基础。标准化重建将这种变异性降低到4％和5％。高BMI妨碍了小病变（<10 ml）的定量。在多中心和多供应商环境中进行绝对SPECT定量分析是可行的，尤其是在对重建协议进行标准化的情况下，这为绝对定量SPECT标准奠定了基础。标准化重建将这种变异性降低到4％和5％。高BMI妨碍了小病变（<10 ml）的定量。在多中心和多供应商环境中进行绝对SPECT定量分析是可行的，尤其是在对重建协议进行标准化的情况下，这为绝对定量SPECT标准奠定了基础。