Toward the development of a B0 gradientless MRI system: Frequency-encoded Frequency-modulated Rabi Encoded Echoes.

Frequency-encoded Frequency-modulated Rabi Encoded Echoes (FE-FREE) is a new method to perform spatial encoding using a B1 field gradient. FE-FREE is analogous to conventional frequency-encoding with a B0 gradient, except a B1 gradient is used. A first demonstration of FE-FREE is shown using the B1 gradient of a surface coil in a 0.5 T magnet with large B0 inhomogeneity (±3 ppm). Frequency encoding with FE-FREE is one approach that in the future might enable low cost MRI scanners without B0 gradient hardware and infrastructure.