Rita G. Nunes1, Ivana Drobnjak2,
Stuart Clare3, Peter Jezzard3, Mark Jenkinson3
1Robert Steiner MRI Unit, Imaging
Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital,
Imperial College London, London, United Kingdom; 2Centre for
Medical Image Computing, University College London, London, United Kingdom; 3Oxford
Centre for Functional Magnetic Resonance Imaging of the Brain, University of
Oxford, Oxford, United Kingdom
Echo-planar
diffusion-weighted images can display significant geometric distortions due
to eddy current fields. Several diffusion preparation schemes have been
proposed, which can null eddy currents with a single time constant. We use an
MRI simulator to compare the performance of three such sequences in the
presence of multiple components, and investigate whether affine registration
is capable of correcting for the resulting distortions. Our study confirms
that, in general, doubly-refocused sequences perform better than single
spin-echo approaches, and suggest that when the use of two refocusing pulses
is not desirable, it may be preferable to use a modified single spin-echo
sequence.