Combined Coronary Vessel Lumen and Plaque Assessment Using iT2prep-BOOST: A Prospective Study in Patients with Stable Chest Pain

Background: Atherosclerotic coronary artery plaques are associated increased cardiovascular events¹. CT coronary angiography (CTCA) is the guideline recommended technique for non-invasive coronary artery imaging in patients with low-intermediate risk chest pain due to its high negative predictive value, high spatial resolution, and fast acquisition times^2,3. However, inherent drawbacks include ionising radiation and iodinated contrast administration. Cardiovascular magnetic resonance (CMR) has the potential to provide an alternative. We sought to assess an interleaved T2 and inversion recovery prepared Bright-blood and black-blOOd phase SensiTive (iT2prep-BOOST) sequence^4,5 to evaluate coronary lumen, stenosis, and plaque characteristics compared with CTCA in patients with stable chest pain.

Methods: Fifty patients (average age 56 ± 11 years, 60% male) referred for CTCA for stable chest pain symptoms underwent additional BOOST imaging on a 1.5T MRI scanner (MAGNETOM Sola, Siemens Healthcare, Forchheim, Germany). iT2prep-BOOST is an ECG-triggered, 3D whole heart, free breathing research sequence, where a combined T2 preparation and inversion recovery (T2Prep-IR) preparation module was applied before data acquisition in odd heartbeats and fat saturation was applied in even heartbeats, resulting in two co-registered datasets. 2D image navigators (iNAVs)⁶ are incorporated at each heartbeat to enable 100% respiratory efficiency. Non-rigid motion-corrected reconstruction was performed directly in the scanner software with patch-based low-rank denoising with PROST⁷ performed offline. The two datasets undergo magnitude subtraction to generate a co-registered black-blood image for vessel wall and plaque visualisation. Coronary plaques identified on CTCA were analysed on CMR for plaque-to-myocardium signal intensity ratio (PMR), and a healthy vessel-to-myocardium ratio (HVMR) was derived as reference. Luminal stenosis was assessed on bright-blood images on cross-sectional views and compared with CTCA.

Results: Example patient images with plaque in the LAD and RCA are demonstrated in Figures 1 and 2 respectively. PMR of coronary plaque was significantly higher than HVMR (0.64 ± 0.16 vs 0.36 ± 0.11; p < 0.001) (Figure 3). In addition, all plaque subtypes (calcified, partially calcified and non-calcified) showed a significantly higher PMR than HVMR (0.53 ± 0.11 vs 0.70 ± 0.15 vs 0.69 ± 0.16 vs 0.36 ± 0.11 respectively; all p < 0.001). There was minimal bias for stenosis quantification compared with CTCA (mean difference –0.36%, 95% LoA –19.3% to 18.5%).

Conclusion: The iT2prep-BOOST sequence allows simultaneous evaluation of coronary lumen and plaque characteristics in a single non-contrast CMR acquisition, with reliable plaque identification and high agreement with CTCA for stenosis assessment. This approach may offer a much-needed radiation and contrast-free alternative for integrated anatomical and plaque imaging in patients with stable chest pain.

Figure 1. BOOST and CTCA assessment of a mid LAD plaque. Top row: axial BOOST bright-blood image (left), black-blood image (centre), and corresponding CTCA (right). Bottom row: cross-sectional views at the level of a plaque in the mid LAD using the same modalities. White arrows indicate the location of the atherosclerotic plaque, which appears hyperintense on the black-blood image and corresponds to a partially calcified lesion on CTCA.Figure 2. Plaque visualisation in the proximal RCA using iT2prep-BOOST and CTCA. Top left: BOOST bright-blood image; Top right: BOOST black-blood image; Bottom left: fusion image of bright- and black-blood BOOST; Bottom right: corresponding CTCA image. White arrows indicate the location of an atherosclerotic plaque in the proximal RCA, which appears hyperintense on the black-blood image and corresponds to a partially calcified lesion on CTCA.
Figure 2. Plaque visualisation in the proximal RCA using iT2prep-BOOST and CTCA. Top left: BOOST bright-blood image; Top right: BOOST black-blood image; Bottom left: fusion image of bright- and black-blood BOOST; Bottom right: corresponding CTCA image. White arrows indicate the location of an atherosclerotic plaque in the proximal RCA, which appears hyperintense on the black-blood image and corresponds to a partially calcified lesion on CTCA.
Figure 3. Paired comparison of PMR and healthy HVMR on iT2prep-BOOST (left) and Subgroup analysis of PMR across plaque morphologies and healthy vessels (right). Each red dot represents a single coronary plaque, with lines connecting paired PMR and HVMR values from the same patient. PMR values were significantly higher than HVMR values (mean difference = 0.28, p < 0.001), indicating increased signal in plaque regions relative to healthy vessel segments. Individual PMR values are shown for healthy vessels (blue), calcified plaques (red), mixed plaques (orange), and non-calcified plaques (green). A one-way ANOVA demonstrated a significant difference among groups (p < 0.001). Tukey’s post hoc test showed significantly higher PMR higher in all plaque types compared to healthy vessels (healthy vs calcified: mean difference –0.17, 95% CI –0.254= to –0.09, p < 0.001; healthy vs mixed: –0.35, 95% CI –0.42 to –0.27, p < 0.001; healthy vs non-calcified: –0.33, 95% CI –0.42 to –0.24, p < 0.001). Both mixed and non-calcified plaques showed significantly higher PMR than calcified plaques (mean difference –0.17, 95% CI –0.27 to –0.08, p < 0.001 and mean difference –0.16, 95% CI –0.26 to –0.05, p < 0.001, respectively). No significant difference was observed between mixed and non-calcified plaques (mean difference 0.02, 95% CI –0.09 to 0.12, p = 0.98).