Performance of single spin-echo and doubly refocused diffusion-weighted sequences in the presence of eddy current fields with multiple components.

Echo-planar diffusion-weighted images can display significant geometric distortions due to eddy current fields. Several preparation schemes have been proposed, which can null eddy currents with a single time constant. The aim of this work was to compare the performance of three such pulse sequences in the presence of multiple components and investigate whether affine registration is capable of correcting for the resulting distortions. A magnetic resonance imaging simulator was used to eliminate potential confounding factors. The doubly refocused sequences showed substantially reduced effects. Applying affine registration to the single spin-echo images leads to reduced residuals, but not to the level observed for the doubly refocused sequences. Modified versions of the standard single spin-echo and doubly refocused sequences performed better than their original counterparts. Affine registration is not sufficient to correct for strong eddy current effects, which should therefore be minimized at source. When the use of a doubly refocused sequence is not possible, a modified single spin-echo sequence should be considered