MR flow imaging by velocity-compensated/uncompensated difference images

The phase shifts acquired by motion of excited spins along magnetic field gradients can result in decreased signal intensity from blood vessels in conventional magnetic resonance images. The imaging technique can be modified with the use of additional gradient pulses so as to either compensate these phase shifts and increase the signal from the vessels or augment the phase shift and decrease the signal, without altering the signal from stationary tissues. Making a difference image from images made with and without sensitization to motion will cancel out the stationary tissues, leaving an image of the vessels alone. The technique does not require cardiac gating, shows veins as well as arteries, and can be performed in an interleaved manner to avoid registration errors due to patient motion.