Assessment of Coronary Plaque Burden using Non-Contrast T1-weighted Cardiovascular MR: Comparison with Coronary CT Angiography.

BACKGROUND: Non-contrast T1-weighted cardiovascular MR (CMR) enables assessment of coronary atherosclerotic plaques by exploiting elevated signal intensity within high-risk plaque components. The novel iT2prep-BOOST sequence provides co-registered coronary lumen and vessel wall whole-heart imaging, potentially facilitating plaque assessment. However, direct comparison of quantitative plaque measures between iT2prep-BOOST and coronary computed tomography angiography (CCTA), the non-invasive standard for plaque assessment, remains limited. This study aimed to compare coronary plaque burden and plaque signal intensity measured by iT2prep-BOOST with plaque burden and plaque attenuation characteristics derived from CCTA. METHODS: In this prospective, observational study, patients with stable coronary artery disease confirmed by diagnostic CCTA were recruited and subsequently underwent CMR using the iT2prep-BOOST sequence. Using semi-automated software, per-lesion cross-sectional areas of total, calcified, non-calcified, and low-density non-calcified plaque (≤30 Hounsfield unit) together with measures of plaque burden (percentage vessel atheroma) were quantified on CCTA. The corresponding coronary atherosclerotic lesion was analysed on T1-weighted black-blood iT2prep-BOOST CMR to assess cross-sectional plaque area, burden, and plaque-to-myocardial signal intensity ratio (PMR). RESULTS: A total of 188 lesions in 85 patients were analysed and compared between iT2prep-BOOST and CCTA. Plaque burden estimates derived from iT2prep-BOOST demonstrated moderate correlation with CCTA-derived total plaque burden (r = 0.58) and non-calcified plaque burden (r = 0.54). However, agreement between modalities was limited. For total plaque burden, the mean difference was -4% (95% CI: -7% to -2%) with limits of agreement ranging from -38% to 29%. For non-calcified plaque burden, the mean difference was 3% (95% CI: 0% to 5%) with limits of agreement from -34% to 39%. In univariate regression analyses, PMR was associated with increasing total, non-calcified, and low-density non-calcified plaque areas and decreasing CT attenuation values. CONCLUSION: Coronary plaque burden assessed by iT2prep-BOOST demonstrated modest correlation and limited agreement with CCTA-derived plaque burden, indicating that the two modalities are not directly interchangeable for plaque burden quantification. Nevertheless, the observed associations between PMR and adverse CCTA plaque characteristics support the potential role of T1-weighted CMR as a complementary, non-invasive tool for coronary plaque characterization.