IR prepped FSPGR
On a GE SIGNA 5.x system the 3D Fast Spoiled Grass sequence (3D-IR-FSPGR) with IR preparation is the nearest equivalent to the MP-RAGE technique. As with MP-RAGE, this sequence uses an inversion pulse followed by a spoiled low flip, short TR GRE train to collect all partition data (Kz), then repeating the process with a different value of Gy. The notable difference is that 3D-IR-FSPGR uses centric ordering of Gz. This means the selected TI is also the effective TI. The centric re-ordering strategy can lead to image blurring if a steady state is not achieved quickly with low flip angles (<20 degrees). In practice this requirement is not restrictive, and the images of the two sequences should look similar, but the TI parameters of the IR-FSPGR will be longer than that selected for MP-RAGE when achieving the same image contrast.
TR 20 mSec, Flip 25 degrees TE Minimum (bandwidth dependant)
TI 350 - 800 mSec (depending on Age)
Enhanced Dynamic Range ON
Sagittal or Coronal Slab 180 - 240 mm 3/4 FOV
Resolution approx 1 mm x 0.7 mm x 0.7 mm
Bandwidth less than +/- 10 kHz.
Michael Kean of Royal Childrens' Hospital, Melbourne, has optimised the sequence for general isotropic T1 weighted brain imaging. His parameters are shown in the technique box. The SNR of the sequence has been maximised by minimising the bandwidth. This protocol appears to display more extensive flow related enhancement (in children at least) than the MP-RAGE sequences.
