(FGRE) The fast gradient recalled echo sequence belong to the refocused gradient echo sequences.

See Gradient Echo Sequence.

FSE optimization runs a preliminary TR period at the central slice and compares the phase of each echo in the echo train. If the phases do not compliment each other the RF is recalibrated and then the entire sequence is run. If there is an error in calibrating the phases of each of the echoes artifacts will appear.

(DE FGRE, Dual/FFE, DE FFE) Simultaneously acquired in and out of phase TE gradient echo images. To quantitatively measure the signal intensity differences between out of phase and in phase images the parameters should be the same except for the TE.
The chemical shift artifact appearing on the out-of-phase image allows for the detection of lipids in the liver or adrenal gland, such as diffuse fatty infiltration, focal fatty infiltration, focal fatty sparing, benign adrenocortical masses and intracellular lipids within a hepatocellar neoplasm, where spin echo and fat suppression techniques are not as sensitive. Specific pathologies that have been reported include liver lipoma, angiomyolipoma, myelolipoma, metastatic liposarcoma, teratocarcinoma, melanoma, haemorrhagic neoplasm and metastatic choriocarcinoma.

(FADE) A fast imaging technique, which observes both components of the SSFP signal in separate acquisition periods during a single interpulse interval.

See Dual Echo Steady State.

(IRSE) Form of inversion recovery imaging in which the signal is detected as a spin echo. For TE short compared to the T2 relaxation time, there will be only a small effect of T2 differences on image intensities; for longer TE's, the effect of T2 may be significant.