Commissioning, calibration, and quality control procedures for nuclear medicine imaging systems are typically performed using hollow containers filled with radionuclide solutions. This leads to multiple sources of uncertainty, many of which can be overcome by using traceable, sealed, long-lived surrogate sources containing a radionuclide of comparable energies and emission probabilities. This study presents the results of a quantitative SPECT/CT imaging comparison exercise performed within the MRTDosimetry consortium to assess the feasibility of using 133Ba as a surrogate for 131I imaging. Two sets of four traceable 133Ba sources were produced at two National Metrology Institutes and encapsulated in 3D-printed cylinders (volume range 1.68–107.4 mL). Corresponding hollow cylinders to be filled with liquid 131I and a mounting baseplate for repeatable positioning within a Jaszczak phantom were also produced. A quantitative SPECT/CT imaging comparison exercise was conducted between seven members of the consortium (eight SPECT/CT systems from two major vendors) based on a standardised protocol. Each site had to perform three measurements with the two sets of 133Ba sources and liquid 131I. As anticipated, the 131I pseudo-image calibration factors (cps/MBq) were higher than those for 133Ba for all reconstructions and systems. A site-specific cross-calibration reduced the performance differences between both radionuclides with respect to a cross-calibration based on the ratio of emission probabilities from a median of 12–1.5%. The site-specific cross-calibration method also showed agreement between 133Ba and 131I for all cylinder volumes, which highlights the potential use of 133Ba sources to calculate recovery coefficients for partial volume correction. This comparison exercise demonstrated that traceable solid 133Ba sources can be used as surrogate for liquid 131I imaging. The use of solid surrogate sources could solve the radiation protection problem inherent in the preparation of phantoms with 131I liquid activity solutions as well as reduce the measurement uncertainties in the activity. This is particularly relevant for stability measurements, which have to be carried out at regular intervals.

中文翻译：

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关于在 SPECT/CT 校准中使用固体 133Ba 源作为液体 131I 的替代品：欧洲多中心评估

核医学成像系统的调试、校准和质量控制程序通常使用填充放射性核素溶液的中空容器来执行。这导致了多种不确定性来源，其中许多可以通过使用包含具有可比能量和发射概率的放射性核素的可追踪、密封、长寿命替代源来克服。本研究介绍了 MRTDosimetry 联盟内进行的定量 SPECT/CT 成像比较研究的结果，以评估使用 133Ba 作为 131I 成像替代品的可行性。两套四个可追溯的 133Ba 源在两个国家计量研究所生产，并封装在 3D 打印的圆柱体中（体积范围 1.68–107.4 mL）。还生产了相应的填充液体 131I 的空心圆柱体和用于在 Jaszczak 体模内重复定位的安装底板。根据标准化协议，在该联盟的七个成员（来自两个主要供应商的八个 SPECT/CT 系统）之间进行了定量 SPECT/CT 成像比较活动。每个站点必须使用两组 133Ba 源和液体 131I 进行 3 次测量。正如预期的那样，对于所有重建和系统，131I 伪图像校准因子 (cps/MBq) 均高于 133Ba。与基于中值 12-1.5% 的发射概率之比的交叉校准相比，特定地点的交叉校准减少了两种放射性核素之间的性能差异。特定地点交叉校准方法还显示 133Ba 和 131I 对于所有气瓶体积都一致，这突出了 133Ba 源计算部分体积校正的恢复系数的潜在用途。该比较练习表明，可追踪的固体 133Ba 源可用作液体 131I 成像的替代品。使用固体替代源可以解决用 131I 液体活度溶液制备模型所固有的辐射防护问题，并减少活度测量的不确定性。这对于必须定期进行的稳定性测量尤其重要。