MRI Sequences

Ultrafast spoiled gradient echo sequences

by Denis Hoa

Type of sequence Philips Siemens GE Hitachi Toshiba
Ultrafast spoiled GE

T1-TFE
T2-TFE

 

THRIVE

 

 

TurboFLASH

 

VIBE

FGRE
Fast SPGR
FMPSPGR
VIBRANT
FAME
LAVA
SARGE

 

 

Fast FE

 

RADIANCE
QUICK 3D

Ultrafast spoiled GE
with magnetization preparation
IR-TFE T1/T2-TurboFLASH IR-FSPGR
DE-FSPGR
Fast FE

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Ultrafast gradient echo sequences use a small flip angle, a very short TR and optimized k-space filling to reduce acquisition time (to roughly one second per slice). The drawback of a small flip angle and very short TR is poor T1-weighting.
To preserve T1 contrast, a 180° inversion pulse prepares magnetization before repetitions of the ultrafast gradient echo imagery sequence . Effective inversion time will correspond to the delay between the inversion pulse and acquisition of the central k-space lines.
To obtain T2-weighting, the preparatory pattern is of the spin echo type (90° - 180°) so that the ultrafast GE imaging sequence can start with longitudinal magnetization whose amplitude depends on T2 .

 

K-space filling can follow variable trajectories (linear, centripetal, centrifugal) to determine image contrast. Either all the k-space lines are acquired after a single inversion pulse (« single shot »), or only a group of lines is acquired (segmented filling).
The speed of these T1-weighted gradient echo sequences is particularly suited to monitoring Gadolinium bolus arrival in imaging at arterial phase and in T1 high resolution 3D imaging.