Low-dose 3D time-resolved magnetic resonance angiography (MRA) of the supraaortic arteries: Correlation with high spatial resolution 3D contrast-enhanced MRA

Abstract

To evaluate the feasibility of low-dose, 3D time-resolved contrast-enhanced magnetic resonance angiography (TR-CEMRA) in the assessment of the supraaortic vessel, and to compare the results with high-resolution contrast-enhanced MRA (HR-CEMRA). This was an Institutional Review Board-approved retrospective study. Forty-five consecutive patients underwent contrast-enhanced 3D TR-CEMRA and 3D HR-CEMRA for evaluation of neurovascular disease at 3.0 T. Gadobutrol was administered at a constant dose of 1 mL for TR-CEMRA (independent of patient weight), and 0.1 mmol/kg for HR-CEMRA. Two readers evaluated image quality using a four-point scale (from 0 = excellent to 3 = nondiagnostic), and subsequently graded each stenosis into clinically relevant categories: normal (0%), mild stenosis (<50%), moderate to severe (>50%), and occlusion. The overall image quality for low-dose TR-CEMRA was in the diagnostic range (median 0, range 0-3). On the grading of stenosis, TR-CEMRA using the TWIST sequence correlated with HR-CEMRA (r = 0.668, P < 0.001). In terms of the comparison of TR-CEMRA with HR-CEMRA, of the 675 supraaortic arterial segments evaluated for stenosis or occlusion, agreement occurred in 611 of 675 (90.5%), overestimation in 41 of 675 (6.1%), and underestimation 23 of 675 (3.4%). TR-CEMRA achieved by administration of a small contrast dose (1 cc) yields rapid and important functional and anatomical information in the evaluation of supraaortic arteries. Due to limited spatial resolution, TR-CEMRA at the current parameters has a tendency to overestimate the stenosis of smaller intracranial arteries compared to HR-CEMRA.