Improved k-space trajectory measurement with signal shifting.

Various techniques for k-space trajectory measurement have been described in the literature. Self-encoding gradient techniques are time-consuming due to the high number of phase-encoding steps needed. The approach with localized slices is faster, but its use apparently has not been reported in the context of high spatial resolution experiments. Signals associated with high k-space frequencies may then reach low or even zero values, and this may result in errors in the estimate of the trajectories at the k-space periphery. To overcome this problem without increasing the measurement duration of the localized slice method too much, a new approach is proposed in which an addition dephasing gradient applied prior to the gradient to be measured shifts the signal maximum. (c) 2007 Wiley-Liss, Inc.