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Inversion in the steady state: contrast optimization and reduced imaging time with fast three-dimensional
T K Foo1, A M Sawyer, W H Faulkner
1Applied Science Laboratory, GE Medical Systems, Milwaukee, WI 53201.
Purpose:
To evaluate the differences in contrast between 1-second delay and zero delay (for magnetization recovery) before the preparation radio-frequency pulse in three-dimensional, inversion-recovery (IR) fast gradient-echo (GRE) acquisitions.
Materials And Methods:
Mathematical simulations and measurements of brain image contrast were performed with healthy volunteers and 10 patients.
Results:
The zero-delay sequence generated T1-weighted contrast similar to that obtained with 1-second delay but was accompanied by a substantial reduction in imaging time. However, the zero delay prohibits full recovery of the longitudinal magnetization. Hence, the signal null characteristic of IR experiments is not easily observed, since it occurs (as a function of tissue T1) at very short inversion times (< 150 msec).
Conclusion:
T1-weighted contrast comparable with that of magnetization-prepared rapid GRE sequences with a 1-second delay and preparation time (TP) of 600-700 msec can be achieved in less time by using a zero delay and a shorter TP (400-500 msec).