Basic Principles; Principle Of Multi-Echo Epi - Siemens MULTI-ECHO EPI 4A21 Installation And User Manual

Multi-Echo EPI

1 Basic principles

1.1 Principle of Multi-Echo EPI

The basic timing scheme of Multi-Echo EPI is shown in Figure 1. It is based on the
original EPI sequence proposed by Mansfield (1). After a single RF-excitation, n
complete EPI images are acquired in a single shot. The phase gradient is rewound to
the original starting position after each echo-image to ensure identical k-space
trajectories for all echo-images (2).
RF
G
S
G
R
G
P
echo-image loop
n
Figure 1 – Basic timing of the Multi-Echo EPI sequence. The shaded gradient in
phase encoding direction ensures identical k-space trajectories for all echo-images.
The resulting echo-images have different increasing echo times and thus T2*-
weighting. The single echo-images correspond to standard gradient echo EPI images
with the same echo time.
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