The introduction of hybrid SPECT/CT devices enables quantitative imaging in SPECT, providing a methodological setup for quantitation using SPECT tracers comparable to PET/CT. We evaluated a specific quantitative reconstruction algorithm for SPECT data using a 99mTc-filled NEMA phantom. Quantitative and qualitative image parameters were evaluated for different parametrizations of the acquisition and reconstruction protocol to identify an optimized quantitative protocol. The reconstructed activity concentration (ACrec) and the signal-to-noise ratio (SNR) of all examined protocols (n = 16) were significantly affected by the parametrization of the weighting factor k used in scatter correction, the total number of iterations and the sphere volume (all, p < 0.0001). The two examined SPECT acquisition protocols (with 60 or 120 projections) had a minor impact on the ACrec and no significant impact on the SNR. In comparison to the known AC, the use of default scatter correction (k = 0.47) or object-specific scatter correction (k = 0.18) resulted in an underestimation of ACrec in the largest sphere volume (26.5 ml) by − 13.9 kBq/ml (− 16.3%) and − 7.1 kBq/ml (− 8.4%), respectively. An increase in total iterations leads to an increase in estimated AC and a decrease in SNR. The mean difference between ACrec and known AC decreased with an increasing number of total iterations (e.g., for 20 iterations (2 iterations/10 subsets) = − 14.6 kBq/ml (− 17.1%), 240 iterations (24i/10s) = − 8.0 kBq/ml (− 9.4%), p < 0.0001). In parallel, the mean SNR decreased significantly from 2i/10s to 24i/10s by 76% (p < 0.0001). Quantitative SPECT imaging is feasible with the used reconstruction algorithm and hybrid SPECT/CT, and its consistent implementation in diagnostics may provide perspectives for quantification in routine clinical practice (e.g., assessment of bone metabolism). When combining quantitative analysis and diagnostic imaging, we recommend using two different reconstruction protocols with task-specific optimized setups (quantitative vs. qualitative reconstruction). Furthermore, individual scatter correction significantly improves both quantitative and qualitative results.

中文翻译：

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用于定量和定性 99mTc SPECT 的 SPECT/CT 成像协议的优化

混合 SPECT/CT 设备的引入实现了 SPECT 中的定量成像，为使用与 PET/CT 相当的 SPECT 示踪剂进行定量提供了方法设置。我们使用 99mTc 填充的 NEMA 体模评估了 SPECT 数据的特定定量重建算法。针对采集和重建协议的不同参数化评估定量和定性图像参数，以确定优化的定量协议。所有检查协议（n = 16）的重建活动浓度（ACrec）和信噪比（SNR）受到散射校正中使用的加权因子k的参数化，迭代总数和球体体积（全部，p < 0.0001）。两个检查的 SPECT 采集协议（具有 60 或 120 个投影）对 ACrec 有轻微影响，对 SNR 没有显着影响。与已知的 AC 相比，使用默认散射校正 (k = 0.47) 或特定对象散射校正 (k = 0.18) 导致最大球体体积 (26.5 ml) 中的 ACrec 被低估了 − 13.9 kBq/ml (- 16.3%) 和- 7.1 kBq/ml (- 8.4%)，分别。总迭代次数的增加导致估计的 AC 增加和 SNR 降低。ACrec 和已知 AC 之间的平均差异随着总迭代次数的增加而减小（例如，20 次迭代（2 次迭代/10 个子集）= - 14.6 kBq/ml (- 17.1%)，240 次迭代 (24i/10s) = - 8.0 kBq/ml (- 9.4%)，p < 0.0001)。同时，平均 SNR 从 2i/10s 显着降低到 24i/10s 76% (p < 0.0001)。使用重建算法和混合 SPECT/CT 进行定量 SPECT 成像是可行的，并且其在诊断中的一致实施可以为常规临床实践中的量化（例如，骨代谢评估）提供前景。在结合定量分析和诊断成像时，我们建议使用两种不同的重建协议和特定任务的优化设置（定量与定性重建）。此外，个体散射校正显着改善了定量和定性结果。在结合定量分析和诊断成像时，我们建议使用两种不同的重建协议和特定任务的优化设置（定量与定性重建）。此外，个体散射校正显着改善了定量和定性结果。在结合定量分析和诊断成像时，我们建议使用两种不同的重建协议和特定任务的优化设置（定量与定性重建）。此外，个体散射校正显着改善了定量和定性结果。