Cardiovascular magnetization transfer ratio imaging compared with histology: a postmortem study.

Cardiovascular magnetization transfer ratio (MTR) imaging by steady state free precession is a promising imaging method to assess microstructural changes within the myocardium. Hence, MTR imaging was correlated to histological analysis. Three postmortem cases were selected based on a suspicion of myocardial infarction. MTR and T2-weighted (T-2w) imaging was performed, followed by autopsy and histological analysis. All tissue abnormalities, identified by autopsy or histology, were retrospectively selected on visually matched MTR and T-2w images, and corresponding MTR values compared with normal appearing tissue. Regions of elevated MTR (up to approximately 20%, as compared to normal tissue), appearing hypo-intense in T-2w-images, revealed the presence of fibrous tissue in microscopic histological analysis. Macroscopic observation (autopsy) described scar tissue only in one case. Regions of reduced MTR (up to approximately 20%) corresponded either to (i) the presence of edema, appearing hyperintense in T-2w-images and confirmed by autopsy, or to (ii) inflammatory granulocyte infiltration at a microscopic level, appearing as hypo-intense T-2w-signal, but not observed by autopsy. Findings from cardiovascular MTR imaging corresponded to histology results. In contrast to T-2w-imaging, MTR imaging discriminated between normal myocardium, scar tissue and regions of acute myocardial infarction in all three cases.