Combined Bright- and Black-Blood Whole-Heart Imaging for Simultaneous Coronary Angiography and Plaque Assessment in Patients with Suspected Stable Coronary Artery Disease (RF_FR_289)

Coronary artery disease (CAD) is one of the major causes of morbidity and mortality in the world.¹  Coronary plaques are associated with an increased risk of cardiovascular events.²  Simultaneous bright- and black-blood whole heart imaging (iT2prep-BOOST) has been demonstrated to identify the coronary and aortic lumen, and vessel wall in patients with aortopathy and acute coronary syndrome for the detection of stenosis and plaque.^3,4 In this study we sought to implement this framework in patients presenting with suspected stable CAD.



Methods:

43 patients who were referred for an elective CT coronary angiogram (CTCA) were recruited and scanned using the iT2prep-BOOST sequence on a 1.5T MRI scanner (MAGNETOM Sola, Siemens Healthcare, Forcheim, Germany). The sequence employs ECG-triggering and a 3D bSSFP readout in concert with a T2 preparation and inversion recovery (T2Prep-IR) module, which was applied before data acquisition in odd heartbeats and fat saturation was applied in even heartbeats (Figure 1), resulting in two bright-blood datasets. The sequence parameters have previously been published^3,5,6  and the following adaptations were used: FoV = 320x320x112-144mm³, isotropic spatial resolution 1.2mm³. 2D image navigators (iNAVs)⁷ are incorporated at each heartbeat to enable 100% respiratory efficiency. Non-rigid motion-corrected iterative SENSE reconstruction was performed inline on the scanner and patch-based low-rank denoising with PROST⁸performed offline. The T2prep-IR dataset can then be used for lumen visualisation whereas digital subtraction of the prepared and unprepared datasets produces a T1-weighted black-blood dataset for vessel wall visualisation. Acquisition was performed in diastole when HR < 70 bpm and in systole otherwise. Coronary plaque lesions were assessed by drawing a region of interest (ROI) within the lesion as well as in the myocardium to achieve a plaque-to-myocardium signal ratio (PMR) and compared to a region of healthy vessel-to-myocardium ratio (HVMR). Qualitative image quality analysis using a 4-point Likert scale (1: uninterpretable images, 2: poor image quality, 3: acceptable image quality, 4: excellent image quality) was performed by a clinical expert to analyse the quality of the images.

 



Results:

Of the 43 patients recruited, 21 had CAD identified on CTCA (14 males, average age 55 years ±12) with a total of 35 plaque lesions. The average overall image quality score for the iT2prep-BOOST was 3.3 with only 1 scan considered poor quality. Therefore, 34 plaque lesions were included for analysis. Example patients demonstrating a plaque in the left anterior descending artery (LAD) and the right coronary artery (RCA) are demonstrated in Figure 2 and Figure 3 respectively. The mean PMR was higher than mean HVMR (0.57±0.13 vs. 0.35±0.10, p< 0.001) with a mean difference of 0.22 (95% CI: 0.27 to 0.19).

 

Conclusion:

The proposed iT2prep-BOOST framework has demonstrated the ability to simultaneously visualise coronary artery stenosis and to differentiate healthy from diseased vessel wall in patients with stable CAD. iT2prep-BOOST has the potential to identify coronary plaques, which are associated with an increase in cardiovascular events², without the need for ionising radiation or contrast agents. Consequently, the proposed framework has the potential to affect downstream medical management to lower cardiovascular risk.