(TFE) Turbo field echo is a
gradient echo pulse sequence with data acquisition after an initial 180° (similar to IR) preparation pulse for
contrast enhancement. The difference between a FFE and TFE other than the speed of the sequence is that the image is acquired while approaching steady state (the echoes are collected during the time in which the tissues are experiencing
T1 relaxation).
The
contrast is prepared one time, which means the
contrast is changing while the echoes are collected and can be manipulated by selecting the type and timing of the
prepulse.
A delay time is given before the actual image acquisition. To achieve
T1 contrast the 180°
prepulse is followed by an operator selected delay time, that results in no signal from the targeted tissue. So when the echoes are acquired, no signal is present, additional RF spoiling is performed to optimize for
T1 contrast.
The delay chosen corresponds to when
T1 relaxation reaches and suppresses
T1 signal or optimizes the difference between tissues.
Contrast for these
sequences are enhanced when
K-space is filled using a centric or low-high ordering.
A TFE can be acquired with a 2D or 3D technique and with or without
T1,
T2 weighting.
See
Ultrafast Gradient Echo Sequence,
TurboFLASH and
Magnetization Prepared Rapid Gradient Echo (MPRAGE).
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