EFFECTS OF GRADIENT TIMING AND SPATIAL-RESOLUTION ON THE NMR SIGNAL FROM FLOWING BLOOD

The authors report both theoretical and experimental studies of the effects on signals from flowing blood due to the application of the rephasing gradient both before and after the 180 degrees refocusing pulse by considering combined time-of-flight and intravoxel phase dispersion effects. They demonstrate that signal losses can occur because of destructive phase cancellations between spin populations of different uniform velocities without turbulence even for relatively slow flows. These effects support the notion that flow compensation gradients are needed to reduce intravoxel phase dispersion effects even for laminar flows.