Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 62, Issue 1, Pages 17-25Publisher
WILEY
DOI: 10.1002/mrm.21970
Keywords
short echo spectroscopic imaging; human brain; 7T; transceiver arrays
Funding
- NCCIH NIH HHS [R21 AT002984] Funding Source: Medline
- NIBIB NIH HHS [R01 EB000473-08, R01 EB000473, R01 EB011639] Funding Source: Medline
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Recent advances in magnet technology have enabled the construction of ultrahigh-field magnets (7T and higher) that can accommodate the human head and body. Despite the intrinsic advantages of performing spectroscopic imaging at 7T, increased signal-to-noise ratio (SNR), and spectral resolution, few studies have been reported to date. This limitation is largely due to increased power deposition and B, inhomogeneity. To overcome these limitations, we used an 8-channel transceiver array with a short TE (15 ms) spectroscopic imaging sequence. Utilizing phase and amplitude mapping and optimization schemes, the 8-element transceiver array provided both improved efficiency (17% less power for equivalent peak B-1) and homogeneity (SD(B-1) = +/-10% versus +/-22%) in comparison to a transverse electromagnetic (TEM) volume coil. To minimize the echo time to measure J-modulating compounds such as glutamate, we developed a short TE sequence utilizing a single-slice selective excitation pulse followed by a broadband semiselective refocusing pulse. Extracerebral lipid resonances were suppressed with an inversion recovery pulse and delay. The short TIE sequence enabled visualization of a variety of resonances, including glutamate, in both a control subject and a patient with a Grade 11 oligodendroglioma. Magn Reson Med 62: 17-25, 2009. (C) 2009 Wiley-Liss, Inc.
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