Figure 2.
MRE pulse sequence diagrams are shown depicting the RF pulses; gradients in the frequency-encoding, phase-encoding, and slice-select directions; and the applied motion (RF, Gx, Gy, Gz, and M, respectively). On the left is a GRE MRE sequence for imaging 60-Hz mechanical motion using a 16.7-ms gradient-moment-nulled (GMN) motion-encoding gradient (MEG) applied along Gz. On the right is a SE-EPI MRE sequence for imaging 60-Hz motion using 2 bipolar 6.5-ms MEG, 1 on each side of the refocusing pulse and synchronized to the motion. Both sequences are shown with GMN imaging gradients and spatial presaturation pulses.