Siemens EPI 4A21 User Manual

Works-in-Progress package

Version 2.0

For the

SIEMENS Magnetom under VA21B

Installation and User’s Guide

NUMARIS/4A21

April 4th, 2003

Section of Medical Physics, University Hospital Freiburg, Germany

Contact:

Oliver Speck PhD, Hugstetterstr. 55, D 79106 Freiburg,

email: [e-mail]

, phone: [phone]

Multi-Echo EPI

Table of Contents

1 Basic principles................................................................................................. 3

1.1 Principle of Multi-Echo EPI........................................................................... 3

1.2 Image contrast of Multi-Echo EPI................................................................. 4

1.3 Processing options....................................................................................... 4

1.4 References................................................................................................... 4

2 Software Installation Procedure....................................................................... 5

2.1 Installation....................................................................................................5

3 Sequences and Protocols................................................................................. 7

3.1 General Remarks ......................................................................................... 7

3.2 New Parameters........................................................................................... 7

3.3 Remarks on reconstruction performance...................................................... 9

3.4 Protocols....................................................................................................... 9

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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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