Time-of-flight MR flow imaging: selective saturation recovery with gradient refocusing.

Abstract

A novel magnetic resonance flow-imaging technique is presented and its suitability evaluated for both qualitative and quantitative imaging of flow. The method is derived from a selective saturation-recovery scheme consisting of at tagging and detection pulse followed by a bipolar read gradient. The detrimental phase effect causing signal loss at fast flow are shown to be greatly reduced because of the absence of 180.degree. pulse and its associated section-selection gradient. The second loss mechanism intrinsic to 180.degree. spin echoes, the washout of excited spins between excitation and detection pulse, likewise is not present with the discussed technique. Assuming a parabolic flow profile, the authors calculated the signal evolution curve and found it to be in agreement with the experimental washout curve. The technique is shown to provide high-intensity signals for arteries such as carotid and vertebral arteries. Arteries and veins can be differentiated by judiciously choosing interpulse intervals or by alternating selective and nonselective tagging pulses.