211 High resolution non-contrast magnetic resonance coronary angiography for coronary artery disease assessment

Introduction Coronary artery disease (CAD) is the leading cause of morbidity and mortality in the developed world. Computed tomography coronary angiography (CTCA), with a spatial resolution of approximately 0.6 mm, is the gold standard in both American and European guidelines for non-invasive anatomical assessment low and intermediate risk patients with suspected coronary artery disease. However, CTCA involves use of ionising radiation and iodinated contrast agents. Coronary magnetic resonance angiography (CMRA) offers a promising radiation- and contrast-free alternative. However, clinical adoption has been hampered by challenges such as low spatial resolution, prolonged and unpredictable scan durations, and susceptibility to motion artefacts. Recent advances utilising image navigators (iNAV) have allowed for 100% respiratory scan efficiency and predicable scan times. In this work we sought to perform high resolution (0.7 mm3) CMRA acquisitions on patients presenting with suspected CAD. Methods Individuals referred for a CTCA to investigate suspected CAD were enrolled in the study. An ECG-triggered, free-breathing, 3D whole-heart, balanced steady-state free precession (bSSFP) research sequence with an under sampled 3D variable density spiral-like Cartesian trajectory with golden-angle rotation was utilised. Low-resolution 2D image navigators (iNAV) were incorporated into the sequence to enable 100% respiratory scan efficiency with predictable scan times. Patient preparation involved sublingual nitrates for coronary dilatation +/- intravenous beta-blockers to achieve a target resting heart rate of 50–60 beats-per-minute (bpm). The acquisition window was defined by the diastolic rest period of the right coronary artery (RCA). Imaging was performed using a 1.5T MRI scanner (MAGNETOM Sola, Siemens Healthineers, Erlangen, Germany). Multiplanar reconstruction and image analysis was performed using cvi42 software (Circle Cardiovascular Imaging Inc., Calgary, Alberta, Canada). CMRA was compared with CTCA for presence of atherosclerotic plaque disease. Results Twenty-two patients were successfully scanned utilising the described CMRA technique. The average heart rate was 55 bpm, and all were in sinus rhythm. The average scan time for the 0.7 mm3 CMRA acquisition was 13 minutes 42 seconds. All acquisitions provided clear visualisation of the proximal and mid portions of all three coronary arteries. An example is shown in figure 1. When compared with the corresponding CTCA there was good agreement for presence of plaque stenosis (figure 2). Discussion This study demonstrates feasibility of free-breathing whole heart CMRA at 0.7 mm3 isotropic spatial resolution with a predictable scan time. The high-resolution acquisition showed excellent stenosis detection when compared with CTCA. This study lends support to CMRA as a radiation and contrast agent-free alternative to CTCA for imaging of coronary anatomy which has the potential to enter clinical practice. Further work is required to assess the negative predictive value of CMRA vs CTCA on a larger cohort of patients. Conflict of Interest Nil