Stirrat CG, et al. - The diagnostic and management benefits of ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced MRI in acute myocarditis were investigated, presuming diagnosis and management gains via this non-invasive imaging technique. USPIO-enhanced MRI did not afford additional clinically relevant information over and above late gadolinium enhancement (LGE) and T2 mapping MRI. This finding indicates no substantial contribution of tissue-resident macrophages to the myocardial inflammation in this entity.