Gs. Slavin et Sj. Riederer, GRADIENT MOMENT SMOOTHING - A NEW FLOW COMPENSATION TECHNIQUE FOR MULTISHOT ECHO-PLANAR IMAGING, Magnetic resonance in medicine, 38(3), 1997, pp. 368-377
This work identifies an additional source of phase error across k(y) i
n multi-shot echo-planar imaging resulting from flow or motion along t
he phase-encoding direction, A velocity-independent flow compensation
technique, gradient moment smoothing, is presented that corrects this
error by forcing the phase to have smooth quadratic behavior, The corr
ection is implemented, without compromising scan time, by changing the
first moment of a bipolar prephaser pulse on a shot-by-shot basis, In
phantom and in vivo experiments, gradient moment smoothing effectivel
y eliminates ghosting and signal loss due to phase-encoding flow, When
used in conjunction with a ''flyback'' echo-planar readout, which com
pensates for flow in the frequency-encoding direction, gradient moment
smoothing renders multi-shot echo-planar imaging relatively insensiti
ve to in-plane flow. This can make multi-shot echo-planar imaging a vi
able technique for accurately imaging inplane flow and may desensitize
it to the otherwise serious problem of in-plane motion.