Abstract #3666

Application of SLR pulses to short-TR spin-echo fMRI at 7T: SNR considerations and a direct demonstration of reduced cardiac noise

Mukund Balasubramanian^1,2, Avery J. L. Berman^3,4, Robert V. Mulkern^1,2, Lawrence L. Wald^1,5, William A. Grissom⁶, and Jonathan R. Polimeni^1,5,7

¹Harvard Medical School, Boston, MA, United States, ²Boston Children's Hospital, Boston, MA, United States, ³Carleton University, Ottawa, ON, Canada, ⁴University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada, ⁵Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ⁶Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ⁷Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

Synopsis

Keywords: fMRI, RF Pulse Design & Fields, Ultra-High-Field MRIWe show that SLR pulses provide much better slice profiles (and thus much higher SNR) than standard sinc pulses for short-TR spin-echo (SE) acquisitions, even when there is substantial B₁⁺ inhomogeneity. As one application, we used SLR pulses and a TR of 300 ms in SE-EPI acquisitions at 7T, enabling the “direct” measurement of cardiac frequencies at ~1 Hz without aliasing. Far less cardiac fluctuation was seen in SE- versus GE-EPI data. While SE-fMRI is known to have reduced macrovascular weighting and thus improved spatial specificity relative to GE-fMRI, our results suggest that it may also have better temporal specificity.

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