Biomedical Engineering Reference
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Figure 3.32: (a) Two-dimensional and (b) 3D ODESSA pulse sequences. Two
TR intervals are shown. Each axis has zero net gradient area over the TR interval.
During odd TRs (at left), a bipolar flow-encoding pulse follows readout on any
axis. A triphasic pulse after even readouts, though not necessary, is included to
mitigate imaging system nonidealities. The numbered locations correspond to
spin states.
3.4.21 Fat-Suppressed 3D MRA
Appropriate rate of fat-suppression pulses (using spec IR spectral selective
inversion recovery) were determined for fat-suppressed 3D magnetic resonance
angiography (MRA) with an elliptical centric view order [21]. In abdominal
3D fast spoiled gradient echo (fast SPGR) wit an elliptical centric view order,
the spec IR pulse rate was changed from zero to one every 15 repetitions (in
nine steps) in eight volunteers. In the equilibrium phase, abdominal contrast-
enhanced 3D MRA was obtained by 3D fast SPGR using an elliptical centric
order without fat-suppression and with two spec IR, and by fat-suppressed 3D
fast SPGR with a sequential-centric view order (3D-EFGRE). Fat and vascular
signals were estimated. Although 3D fast SPGR using an elliptical centric order
with two spec IR placed every 15 TR and 3D-EFGRE effectively decreased fat
signals, these sequences lengthened the breath-hold by 4-6 seconds compared
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