Robinson Andrew P, Ferreira Kelley M, Heetun Warda, Bardiès Manuel, Denis-Bacelar Ana M, Fenwick Andrew J, Lassmann Michael, Tipping Jill, Tran-Gia Johannes
National Physical Laboratory, Hampton Road, London, TW11 0LW, UK.
Department of Oncology, University of Oxford, Oxford, UK.
EJNMMI Phys. 2025 Jun 23;12(1):58. doi: 10.1186/s40658-025-00778-9.
Single Photon Emission Computed Tomography (SPECT) is increasingly used as a quantitative modality, especially in the context of Molecular Radiotherapy, where the measurements are used as input to absorbed dose calculations for patient-specific dosimetry. Establishing measurement traceability is an essential step in providing confidence in quantitative measurements. This requires an unbroken chain of calibrations where uncertainties must be reported in all stages of calibration and for the final measurement result. Traceability ensures that a measurement result can be related to an underlying standard, allowing harmonisation of data, and facilitating comparison of results between sites.
The process of establishing measurement traceability for quantitative SPECT is demonstrated for the therapeutic radionuclide Lu using a common, phantom based, calibration method. Phantoms with activities of Lu, measured using a traceably calibrated radionuclide calibrator, were used to perform the calibration. The calibration was validated using 3D-printed anthropomorphic organ phantom inserts mimicking clinically relevant geometries. For all measurements, traceability to primary standards for radioactivity is demonstrated along with an accompanying calibration chain and statement of uncertainty.
For all activity measurements the dominant component in the activity uncertainty budget was the uncertainty on the radionuclide calibrator calibration factor, resulting in an average combined standard uncertainty of 1.57%. The resulting uncertainty on the SPECT Image Calibration Factor was 1.6%. An optional additional correction was included in the calibration to provide volume-based partial volume correction (PVC). Measurement traceability was extended for measurands using this additional correction. The activity recovery in the organ phantoms with PVC applied was 96(7)% for both the kidney and spleen.
A manufacturer independent methodology for establishing measurement traceability for quantitative SPECT is demonstrated for Lu, using a radionuclide calibrator previously calibrated against national standards. The ability to establish measurement traceability for quantitative SPECT using standard clinical equipment, and the limitations of traceability are presented.
单光子发射计算机断层扫描（SPECT）越来越多地用作一种定量手段，尤其是在分子放射治疗的背景下，其中测量结果被用作患者特定剂量测定中吸收剂量计算的输入。建立测量可追溯性是确保定量测量可信度的关键步骤。这需要一个不间断的校准链，在校准的所有阶段以及最终测量结果中都必须报告不确定度。可追溯性确保测量结果能够与一个基本标准相关联，从而实现数据的统一，并便于不同地点之间的结果比较。
使用一种基于体模的通用校准方法，展示了为治疗性放射性核素镥建立定量SPECT测量可追溯性的过程。使用经过可追溯校准的放射性核素校准器测量的具有镥活度的体模用于进行校准。使用模仿临床相关几何形状的3D打印人体器官体模插入件对校准进行验证。对于所有测量，展示了对放射性基本标准的可追溯性以及伴随的校准链和不确定度声明。
对于所有活度测量，活度不确定度预算中的主要成分是放射性核素校准器校准因子的不确定度，导致平均合成标准不确定度为1.57%。SPECT图像校准因子的最终不确定度为1.6%。校准中包含了一个可选的额外校正，以提供基于体积的部分体积校正（PVC）。使用此额外校正可将测量可追溯性扩展到被测量物。应用PVC后，肾脏和脾脏器官体模中的活度回收率均为96(7)%。
使用先前根据国家标准校准的放射性核素校准器，展示了一种独立于制造商的为镥建立定量SPECT测量可追溯性的方法。介绍了使用标准临床设备建立定量SPECT测量可追溯性的能力以及可追溯性的局限性。
