Steady-state sequence synthesis and its application to efficient fat-suppressed imaging.
A new synthesis algorithm, based on the Shinnar-Le Roux (SLR) transform, can be used to generate fully refocused steady-state pulse sequences with arbitrary magnetization profiles as a function of off-resonant precession. This is accomplished by appropriate periodic oscillation of the RF excitation magnitude and phase from echo to echo. The technique is applied to the design of refocused steady-state free precession (SSFP) sequences with flat profiles, providing the opportunity for banding-artifact-free imaging with steady-state contrast. The algorithm is also used to generate refocused-SSFP sequences with an arbitrarily broad region of attenuated signal. These sequences are implemented and applied to the problem of steady-state fat suppression. Preliminary results show signal levels that agree well with theory, and a broad region of suppressed signal at each echo. Total imaging time is kept identical to that of a standard refocused-SSFP experiment through echo equalization and interleaving. 3D images from the leg of a normal volunteer acquired in 44 s demonstrate the applicability of the technique to fat-suppressed imaging.
Overall
William R
WR
Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA. wro@stanford.edu
Nishimura
Dwight G
DG
Hu
Bob S
BS
D000273:Adipose Tissue / Q000033:anatomy & histology; D000465:Algorithms; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging