title: Single-shot echo-planar imaging with Nyquist ghost compensation: interleaved dual echo with acceleration (IDEA) echo-planar imaging (EPI).
abstract: Echo planar imaging (EPI) is most commonly used for blood oxygen level-dependent fMRI, owing to its sensitivity and acquisition speed. A major problem with EPI is Nyquist (N/2) ghosting, most notably at high field. EPI data are acquired under an oscillating readout gradient and hence vulnerable to gradient imperfections such as eddy current delays and off-resonance effects, as these cause inconsistencies between odd and even k-space lines after time reversal. We propose a straightforward and pragmatic method herein termed "interleaved dual echo with acceleration (IDEA) EPI": two k-spaces (echoes) are acquired under the positive and negative readout lobes, respectively, by performing phase encoding blips only before alternate readout gradients. From these two k-spaces, two almost entirely ghost free images per shot can be constructed, without need for phase correction. The doubled echo train length can be compensated by parallel imaging and/or partial Fourier acquisition. The two k-spaces can either be complex averaged during reconstruction, which results in near-perfect cancellation of residual phase errors, or reconstructed into separate images. We demonstrate the efficacy of IDEA EPI and show phantom and in vivo images at both 3 T and 7 T.
authors.affiliation: Department of Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA. poser@hawaii.edu
authors.forename: Benedikt A
authors.initials: BA
authors.lastname: Poser
authors.forename: Markus
authors.initials: M
authors.lastname: Barth
authors.forename: Pål-Erik
authors.initials: PE
authors.lastname: Goa
authors.forename: Weiran
authors.initials: W
authors.lastname: Deng
authors.forename: V Andrew
authors.initials: VA
authors.lastname: Stenger
mesh_terms: D016477:Artifacts; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement; D019047:Phantoms, Imaging