Non-ECG-gated unenhanced MRA of the carotids: Optimization and clinical feasibility

Abstract : OBJECTIVES: To optimise and assess the clinical feasibility of a carotid non-ECG-gated unenhanced MRA sequence. METHODS: Sixteen healthy volunteers and 11 patients presenting with internal carotid artery (ICA) disease underwent large field-of-view balanced steady-state free precession (bSSFP) unenhanced MRA at 3T. Sampling schemes acquiring the k-space centre either early (kCE) or late (kCL) in the acquisition window were evaluated. Signal and image quality was scored in comparison to ECG-gated kCE unenhanced MRA and TOF. For patients, computed tomography angiography was used as the reference. RESULTS: In volunteers, kCE sampling yielded higher image quality than kCL and TOF, with fewer flow artefacts and improved signal homogeneity. kCE unenhanced MRA image quality was higher without ECG-gating. Arterial signal and artery/vein contrast were higher with both bSSFP sampling schemes than with TOF. The kCE sequence allowed correct quantification of ten significant stenoses, and it facilitated the identification of an infrapetrous dysplasia, which was outside of the TOF imaging coverage. CONCLUSIONS: Non-ECG-gated bSSFP carotid imaging offers high-quality images and is a promising sequence for carotid disease diagnosis in a short acquisition time with high spatial resolution and a large field of view. KEY POINTS : * Non-ECG-gated unenhanced bSSFP MRA offers high-quality imaging of the carotid arteries. * Sequences using early acquisition of the k-space centre achieve higher image quality. * Non-ECG-gated unenhanced bSSFP MRA allows quantification of significant carotid stenosis. * Short MR acquisition times and ungated sequences are helpful in clinical practice. * High 3D spatial resolution and a large field of view improve diagnostic performance.