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Abstract #0900

B1-gradient based MRI using Frequency-modulated Rabi Encoded Echoes (FREE)

Efraín Torres1,2, Taylor Froelich2, Lance DeLaBarre2, Michael Mullen2, Gregory Adriany2, Alberto Tannús3, Daniel Cosmo Pizetta3, Mateus Jose Martins3, and Michael Garwood2
1Biomedical Engineering, University of Minnesota, Minneapolis, MN, United States, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 3Centro de Imagens e Espectroscopia por Ressonância Magnética - CIERMag - Sao Carlos Physics, São Carlos, Brazil

Gradient coils reduce available bore space, incur costs, and create acoustic noise, but their encoding ability requires them to be present in MRI. The encoding strategy introduced here (FREE) removes the reliance on these coils by using a B1-gradient to create a spatially-dependent nutation frequency. Double spin-echoes created with adiabatic full-passage pulses generate magnetization phase proportional to the difference in their time-bandwidth products (R). Modulating the R-value of one of these π pulses traverses k-space similar to standard MRI. Adiabatic pulses make this approach highly tolerant to B0 and B1 inhomogeneity. A family of new sequences using FREE is presented.

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