Why high intensity plaque is bright on MRI?

Although CT is an excellent imaging modality for detecting lipid pools and calcification in the atherosclerotic plaque, it cannot distinguish hemorrhage from fibrous tissue. MRI has a unique capability of identifying subacute hemorrhage as high signal intensity area on T1-weighted MRI. Non-contrast T1-weighted MRI has been used to demonstrate high intensity plaque (HIP) in the coronary arterial wall. HIP was shown to be an important feature of a vulnerable plaque that increases the risk of future cardiac events. However, due to the lack of histopathological analysis of in vivo tissue samples from patients with HIP, the pathological features of HIP are still unknown. In the current issue of American Heart Journal Plus, Ehara et al. investigated the association between the PMR on non-contrast T1-weighted MRI and coronary intraplaque hemorrhage by analyzing plaque specimen obtained by directional coronary atherectomy. An antibody against glycophorin A was used to identify sites of previous plaque hemorrhage. They found a strong positive correlation between PMR and glycophorin A score. The results in the current study by Ehara reinforce the importance and implications of non-contrast T1-weighted MRI for the evaluation of HIP from a pathological perspective. Recent technical advances in MRI such as goldenangle radial sampling, self-gating, compressed sensing with deep learning reconstruction, and simultaneous acquisition of anatomical reference images and T1 weighted images may substantially reduce the total imaging time of coronary plaque MRI.