Multi-modality imaging of high-intensity plaques on non-contrast T1-weighted magnetic resonance imaging: a case report.

Background: Non-contrast T1-weighted imaging (T1WI) with cardiac magnetic resonance enables to evaluate the intensity of coronary plaque. Plaque-to-myocardial signal intensity ratio (PMR) has been shown to associate with an elevated risk of future coronary events. Of note, PMR >1.4 is a best cut-off value to identify high-risk plaque causing future coronary events. One recent study has reported intraluminal thrombus as a contributor to PMR. However, whether plaque material itself is associated with PMR has not been fully characterized yet. We present three cases with coronary artery stenosis evaluated by non-contrast T1WI-magnetic resonance imaging, optical coherence tomography (OCT) and near-infrared spectroscopy (NIRS)-intravascular ultrasound (IVUS) imaging.

Case description: Case 1 exhibited one lesion with high PMR (2.79) at the proximal segment of left anterior descending (LAD) artery. OCT imaging did not identify any obvious intra-luminal thrombus but the presence of lipid-rich plaque harboring cholesterol crystal at the corresponding lesion. In addition, an elevated maximum 4-mm lipid-core burden index (maxLCBI_4mm) (=873) was observed at this lesion by NIRS/IVUS imaging. In case 2, PMR of coronary stenosis at the middle segment of LAD artery was 1.88. This lesion harboured lipidic materials without any thrombus on OCT imaging. NIRS-derived maxLCBI_4mm was 725. Case 3 had a severe stenosis at the middle segment of LAD artery. This lesion exhibited a low PMR (0.90). On OCT and NIRS/IVUS imaging, this lesion was characterized as the presence of small lipid arc with a low maxLCBI_4mm (=386).

Conclusions: These cases showed the possible relationship of T1WI-derived PMR with the degree of lipidic plaque components.