Magnetic resonance angiography in the head and neck.

Magnetic resonance angiography (MRA) provides a means to visualize vessel structure without the use of contrast agents and consequently without the risks and discomfort associated with contrast media. We have developed a flow encoding procedure which exploits the spatial dependence in the phase of spin magnetization generated by a gradient pulse. This technique yields image information for only those spins having macroscopic motion (i.e. flowing blood). Excellent suppression of non-moving spins can be obtained despite the overwhelming abundance of stationary spins. Data are presented in a projection format similar to that of traditional subtraction angiography.