At ultra-high field (7T), the quantification of glutamate by 1H-MRS is more accurate and precise than at lower field strengths. The semi-LASER 1H-MRS pulse sequence has advantages at high field but requires the use of relatively long radio frequency pulses to reduce power deposition. Typically, the shortest achievable echo times (TE) are sub-optimal for glutamate detection. In this study, the optimal TE for glutamate detection was estimated by time-domain simulation and verified against in-vivo measurements. Using simulations, the optimal TE was found to be 125 ms. In-vivo measurements in one subject produced a result of ~102 ms. Both results suggest that the glutamate signal is greater at longer TEs (100-125 ms) when using semi-LASER at 7T compared to the shortest achievable TEs (40-60 ms).
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