Three-dimensional phase contrast angiography.

Bipolar flow-encoding gradients can be used in a three-dimensional magnetic resonance imaging procedure to provide a noninvasive measure of in vivo blood flow. The resulting volume angiogram is a three-dimensional data matrix which can be retrospectively analyzed and displayed in a variety of ways. This angiographic technique provides good suppression of signals arising from stationary tissue, thereby permitting the visualization of small vessels having relatively slow flow. This suppression is obtained by modulating the amplitude of the flow-encoding gradient pulse to either cancel the stationary tissue signal or displace it relative to the flow signal in the volume image.