Abstract #0900

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

Efraín Torres^1,2, 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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