Spin-echo magnetic resonance spectroscopic imaging at 7 T with frequency-modulated refocusing pulses

He Zhu, Brian J. Soher, Ronald Ouwerkerk, Michael Schär, Peter B. Barker
2012 Magnetic Resonance in Medicine  
Two approaches to high-resolution SENSE-encoded magnetic resonance spectroscopic imaging (MRSI) of the human brain at 7 Tesla (T) with whole-slice coverage are described. Both sequences use high-bandwidth radiofrequency pulses to reduce chemical shift displacement artifacts, SENSE-encoding to reduce scan time, and dual-band water and lipid suppression optimized for 7T. Simultaneous B 0 and transmit B 1 mapping was also used for both sequences to optimize field homogeneity using high order
more » ... ng and determine optimum radiofrequency (RF) transmit level, respectively. One sequence ('Hahn-MRSI') used reduced flip angle (90°) refocusing pulses for lower RF power deposition, while the other sequence used adiabatic fast passage (AFP) refocusing pulses for improved sensitivity and reduced signal dependence on the transmit-B 1 level. In 4 normal subjects, AFP-MRSI showed a signal-to-noise ratio improvement of 3.2±0.5 compared to Hahn-MRSI at the same spatial resolution, TR, TE and SENSE-acceleration factor. An interleaved two-slice Hahn-MRSI sequence is also demonstrated to be experimentally feasible.
doi:10.1002/mrm.24357 pmid:22692894 pmcid:PMC3443531 fatcat:szbpfujfwnaxrf6pmbtj2j5xty