Validity of the mediastinum as a reference region to evaluate cardiac accumulation of iodine-123 metaiodobenzylguanidine

Objective The heart-to-mediastinum (H/M) ratio, the heart count normalized for the mediastinum count, is commonly used in cardiac 123I-metaiodobenzylguanidine (MIBG) imaging. However, there are reports describing age-dependent increases in the mediastinum count with or without correction for the injected dose (ID) and a poor correlation between the H/M ratio and heart count normalized for ID. We evaluated the validity of the mediastinum count as a reference in comparison with the ID.