Standardization of 123I-meta-iodobenzylguanidine myocardial sympathetic activity imaging: phantom calibration and clinical applications

PURPOSE Myocardial sympathetic imaging with 123I-meta-iodobenzylguanidine (123I-mIBG) has gained clinical momentum. Although the need for standardization of 123I-mIBG myocardial uptake has been recognized, the availability of practical clinical standardization approaches is limited. The need for standardization includes the heart-to-mediastinum ratio (HMR) and washout rate with planar imaging, and myocardial defect scoring with single-photon emission computed tomography (SPECT). METHODS The planar HMR shows considerable variation due to differences in collimator design. These camera-collimator differences can be overcome by cross-calibration phantom experiments. The principles of these cross-calibration phantom experiments are summarized in this article. 123I-mIBG SPECT databases were compiled by Japanese Society of Nuclear Medicine working group. Literature was searched based on the words "123I-mIBG quantification method", "standardization", "heart-to-mediastinum ratio", and its application to "risk model". RESULTS Calibration phantom experiments have been successfully performed in Japan and Europe. The benefit of these cross-calibration phantom experiments is that variation in the HMR between institutions is minimized including low-energy, low-medium-energy and medium-energy collimators. The use of myocardial 123I-mIBG SPECT can be standardized using 123I-mIBG normal databases as a basis for quantitative evaluation. This standardization method can be applied in cardiac event prediction models. CONCLUSION Standardization of myocardial 123I-mIBG outcome parameters may facilitate a universal implementation of myocardial 123I-mIBG scintigraphy.