FSE, RARE, TSE, FASE

Expansion:

Fast Spin Echo

Rapid Acquisition with Refocussed Echoes

Turbo Spin Echo™ (GE)

Fast Acquistion Spin Echo

Technique:

As in routine spin-echo imaging, a 90 degree RF pulse is followed by a single 180 degree refocussing pulse. However, in fast spin echo (FSE) imaging, multiple 180 degree refocussing pulses are performed with multiple resulting spin-echoes. Each echo has a different phase encoding value and is assigned to a different k-space line. As the number of echoes acquired after a 90 degree excitation increases, scan time decreases but signal to noise also decreases and T2 blurring increases. Maximum ETL is limited by true T2 decay.

Typical Paramaters:

TR: >3000 msec (for T2-weighted images)

TE: Effective TE is time when the central k-space views are acquired (which determine image contrast).

ETL: Echo Train Length - generally between 4 and 16

 

Reference:

All You Really Need to Know About MR Physics, 8-1

Contributor:

 

Related Sequences/Terms:

RARE, SE, Turbo Spin Echo (GE)

Comments:

ETL is number of echoes obtained following single 90 degree RF pulse
As ETL increases scan time decreases
fat appears abnormally bright on T2 FSE images (due to J-coupling)
some proteinaceous tissue appears darker due to magnetization transfer

Pulse Sequence Diagram:

FSEa.GIF (11333 bytes) Fast Spin Echo (FSE/RARE) sequence

 

About MARS MARS Developers

MRI Links Contact MARS What's New