123I-MIBG Cardiac Imaging: Acquisition Protocols and Correction Methods for Quantitative Evaluation

摘要

Cardiac sympathetic imaging with 123I-MIBG offers unique insights into heart failure and neurodegenerative disease. Because of the diffuse nature of impairment, quantitative evaluation is indispensable, and the heart-to-mediastinum ratio is widely accepted as a valuable index. However, estimation of this index is highly dependent on acquisition protocol, especially collimator choice. A low-energy high-resolution collimator having thin septa is often used for 123I-MIBG imaging, and high-energy photons emitted from 123I readily penetrate the thin septa. The heart-to-mediastinum ratios are affected by accumulation in the lung and liver and are underestimated to various degrees. Medium-energy collimators having thick septa are less susceptible to septal penetration and are expected to offer a better indicator of cardiac sympathetic function. This review will provide an overview of the physics of 123I imaging and discuss acquisition protocols and correction methods for quantitative evaluation of cardiac 123I-MIBG imaging with special reference to the effect of septal penetration.