Magnetic resonance imaging and measurement of blood flow.
Blood flow can be shown as a negative image with magnetic resonance spin-echo techniques or as a positive image with gradient-echo techniques. Phase contrast refers to techniques where structures can be seen because of flow-induced phase shifts. These techniques can show the presence (slow flow) and also the direction of flow. Gradient-echo techniques--including phase-contrast versions--can be used with cardiac synchronization to obtain multiple images during the cardiac cycle. These images can be viewed in a movie or cine format to provide dynamic information about blood flow. Blood flow can be measured by using contrast media in boluses or even more elegantly with phase-contrast methods. Clinical applications of flow measurements are growing rapidly. Phase-contrast or gradient-echo techniques can be used to create magnetic resonance angiography, which was first used to study the carotid bifurcation and intracranial circulation and is now being used throughout the body.
McDonnell
C H
CH
Department of Diagnostic Radiology, Stanford University Medical Center, California.
Herfkens
R J
RJ
Norbash
A M
AM
Rubin
G D
GD
D000792:Angiography / Q000379:methods*; D001775:Blood Circulation; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods