Motion robust GRAPPA for echo-planar imaging.

Baron, Corey A.; Beaulieu, Christian

Purpose A readout-segmented method for acquiring robust GRAPPA calibration data for echo-planar imaging (EPI) was proposed and compared with two previous methods, including the gold standard interleaved approach and a single shot method with halved phase encode resolution. Theory and Methods The readout-segmented and single shot techniques acquire adjacent phase encode lines in the same shot to obtain the calibration data, rather than interleaving of lines between shots, to decrease sensitivity to motion. Additionally, it uses multiple segments with shortened frequency encode extent to match the phase encode bandwidth to the undersampled data, which decreases sensitivity to B0 inhomogeneity. The three methods were tested using simulations and EPI scans of the brain in healthy volunteers. Results The interleaved approach exhibited high sensitivity to motion, while residual undersampling artifacts remained in the single shot method due to mismatch of B0 inhomogeneity between the calibration and undersampled data. The readout segmented method exhibited no such errors, having 30% lower ghosting intensity than the single shot method and 90% lower ghosting intensity than the interleaved approach in moving subjects. Conclusion Artifacts from B0 inhomogeneity and motion during calibration scans for EPI GRAPPA can be mitigated with a readout segmented calibration scan. Magn Reson Med 75:1166-1174, 2016. © 2015 Wiley Periodicals, Inc.

Magnetic Resonance in Medicine, 2016, Vol 75, Issue 3, p1166

0740-3194

Academic Journal

10.1002/mrm.25705