Arterial flow characteristics in the presence of vascular disease and implications for fast spin echo‐based noncontrast MR angiography

Abstract

To investigate arterial flow characteristics in the setting of vascular disease, and examine their effect on the performance of fast spin-echo (FSE)-based noncontrast MR angiography (NC-MRA). Seventeen patients were recruited from among those scheduled for routine contrast-enhanced MR angiography (CE-MRA) of the lower extremities at 1.5 Tesla. The research portion of the exam was performed before the clinically-indicated protocol and included phase-contrast imaging at multiple levels in the legs and FSE-based NC-MRA in the calf and thigh, using a three-dimensional ECG-gated technique that exploits differences in arterial flow velocity between diastole and systole. Vascular occlusions were associated with reduced systolic velocity, a delayed systolic peak, and, in two middle-aged patients, an increase in diastolic velocity. Elevated systolic and diastolic velocities were observed in a subject with a nonhealing ulcer. NC-MRA allowed visualization of arteries with systolic velocities as low as 3 cm/s, and exhibited comparable depiction to CE-MRA for diastolic velocities as high as 6 cm/s. At the highest diastolic velocities observed (15 cm/s) arterial depiction was severely degraded. FSE-based NC-MRA as presently implemented performs successfully over a wide range of flow patterns, but does not accommodate extremely low systolic velocities or very high diastolic velocities.