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

PURPOSE: 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).
MATERIALS AND METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.