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Abstract #2371

Prospective frequency correction for TE-averaged semi-LASER

Chu-Yu Lee1, In-Young Choi1,2,3, Peter Adany1, and Phil Lee1,3

1Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas city, KS, United States, 2Department of Neurology, University of Kansas Medical Center, Kansas City, KS, United States, 3Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, United States

Frequency drifts during MRS acquisition results in broad and distorted spectral lineshapes, a reduced SNR and quantification errors. The consequence of frequency drifts is particularly significant in spectral-editing sequences, because spectral editing critically relies on narrow-band frequency selective pulses or accurate spectral alignments among scans for subtraction/addition of spectra. Frequency drift can occur due to subject’s movement and/or MR system instability. Even in advanced MR systems with self-shielded gradients, significant frequency drifts occur due to eddy current-induced heating and cooling of passive shim materials, particularly after MR scans with heavy gradient duty cycles. The effects of frequency drifts can be mitigated through prospective and retrospective frequency corrections. Currently, most spectral-editing methods use post-processing approaches to correct the effects of frequency drifts retrospectively. In this study, we have developed a prospective frequency correction method and implemented it in a semi-LASER based TE-averaged sequence for glutamate detection.

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