Coronary Artery Blood Flow Imaging Using 3D Flow MRI

In this work, a 3D phase contrast (PC) technique is presented, which enables flow velocity measurements in three spatial directions, simultaneously covering the proximal left (LCA) and right (RCA) coronary arteries and yielding both morphological and flow information.

Data is acquired in a single diastolic cardiac phase during free breathing using an isotropic (Δx = 1.2 mm) 3D PC sequence with respiratory gating and compressed sensing acceleration (factor 14). The reference and flow-encoded datasets are obtained from separate scans instead of one interleaved measurement, enabling inter-scan motion correction through image co-registration. The proposed method is validated in a flow phantom and its feasibility is demonstrated in 16 volunteers (8 female, 59.3 ± 16.5 years) and 3 patients (1 female, 71.0 ± 9.6 years) with known CAD, where additional CTA and CT-FFR data were obtained. Data were acquired on a 3 T MRI system and post-processed using in-house developed software.

Flow phantom experiments demonstrated good agreement between the proposed method and a typical 4D Flow acquisition. Mean average velocities in the proximal coronary arteries of volunteers were found to be 11.9 ± 3.3 cm s^-1 (LCA) and 8.4 ± 2.6 cm s^-1 (RCA). For patients, increases in velocities correlated with the locations of stenoses and reduced CT-FFR values.

The feasibility of 3D-PC-MRI for non-invasive 3D blood flow velocity imaging in the coronary arteries is demonstrated. Simultaneous acquisitions of high-resolution morphology and velocities could offer new opportunities for diagnosing and monitoring CAD.