Zero to low-field MRI with averaging of concomitant gradient fields

Magnetic resonance imaging (MRI) encounters fundamental limits in circumstances where the static magnetic field is not sufficiently strong to truncate unwanted, so-called ''concomitant'' components of the gradient field. Most prominently in low field imaging this limitation affects the attainable optimal image fidelity and resolution. In this communication we introduce the use of pulsed magnetic field averaging toward relaxing these constraints. It is found that the image of an object can be retrieved by pulsed low fields in the presence of the full spatial variation of the imaging encoding gradient field even in the absence of the typical uniform high-field time independent contribution. In addition, error compensation schemes can be introduced through the application of symmetrized pulse sequences. Such schemes substantially mitigate artifacts related to evolution in strong magnetic field gradients, magnetic fields that vary in direction and orientation, and imperfections of the applied field pulses