From gradient echo to echo planar

One excitation, then several echoes. These three lessons measure the echo spacing of a train of readouts, the effect of a phase-encode blip between the echoes, and the artefacts that remain when the whole matrix is acquired after a single pulse.

Page	What it establishes
Multi-echo readouts	A train of readouts of alternating polarity, and the echo spacing set by the receiver bandwidth and the gradient ramps.
Segmented echo planar	A phase-encode blip between the echoes, and the exchange of scan time for geometric fidelity the shot count makes.
Single-shot echo planar	One excitation for the whole matrix: the blurring the decay across the train produces, and the ghost a gradient delay produces.