Phase-modulated binomial RF pulses for fast spectrally-selective musculoskeletal imaging.
Two fat-suppressed three-dimensional gradient echo pulse sequences, FLASH and DESS (Double Echo in Steady-State), that have significantly reduced scan time compared with conventional chemical shift fat-suppression sequences are presented. This fat-suppression technique is based on selectively exciting water spins using a time-optimized binomial RF pulse pair at the water resonance frequency with a null in the excitation profile at the fat frequency. To minimize the total pulse length, the delay between the binomial components of the RF pulse is decreased from a standard jump-return implementation. To maintain the proper null frequency, the phase of the second RF pulse is shifted such that it returns the fat resonance back to its initial z position while further tipping the water spins. Nonselective phase-modulated RF pulse pairs can be implemented in 1.20 ms at 1.0 T, significantly reducing the minimum TR.
Thomasson
D
D
Siemens Medical Systems Magnetic Resonance Research and Development Department, Iselin, New Jersey 08830, USA.
Purdy
D
D
Finn
J P
JP
D006801:Humans; D007091:Image Processing, Computer-Assisted; D007717:Knee / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009141:Musculoskeletal System / Q000033:anatomy & histology*; D019047:Phantoms, Imaging; D013997:Time Factors