Rapid inner-volume imaging in the steady-state with 3D selective excitation and small-tip fast recovery imaging.

Magnetic Resonance in Medicine

PubMedID: 26507586

Sun H, Fessler JA, Noll DC, Nielsen JF. Rapid inner-volume imaging in the steady-state with 3D selective excitation and small-tip fast recovery imaging. Magn Reson Med. 2016;76(4):1217-23.
PURPOSE
Develop a method for rapid three-dimensional inner-volume (IV), or reduced field-of-view, steady-state imaging.

METHODS
Tailored radiofrequency pulses for exciting a three-dimensional IV were designed using a recently proposed algorithm and used in three different sequences: spoiled gradient echo, balanced steady-state free precession, and "small-tip fast recovery" (STFR) which uses a "tip-up" RF pulse after the readout to fast recover spins to the longitudinal axis. The inner- and outer-volume (OV) steady-state signals were analyzed. To demonstrate the potential utility of the proposed method, segmented stack-of-spirals reduced field-of-view images in a volunteer were acquired.

RESULTS
For a given three-dimensional IV excitation pulse, STFR can achieve higher IV/OV signal ratio compared with spoiled gradient echo and balanced steady-state free precession. For spoiled gradient echo and balanced steady-state free precession, this ratio is significantly lower than that produced by a single IV excitation. For STFR, this ratio exceeds that produced by a single IV excitation, due to partial OV saturation produced by the nonspatially selective tip-up pulse. Reduced FOV STFR stack-of-spirals imaging with 2-fold under-sampling in both x-y and z is demonstrated.

CONCLUSION
STFR provides an effective mechanism for OV suppression in steady-state IV imaging. The recently proposed joint pulse design method can be used in the STFR sequence to achieve fast reduced field-of-view imaging. Magn Reson Med 76:1217-1223, 2016. © 2015 Wiley Periodicals, Inc.