MRI SYSTEM USING NONUNIFORM MAGNETIC FIELDS

摘要

A method for magnetic resonance imaging uses an electromagnet [304], which may have open geometry, to generate a spatially nonuniform magnetic field within an imaging region [306]. The current through the electromagnet is controlled to repeatedly cycle the nonuniform magnetic field between a high strength for polarizing spins and a low strength for spatial encoding and readout. Using RF coils [308], excitation pulses are generated at a frequency that selects a non-planar isofield slice for imaging. The RF coils are also used to generate refocusing pulses for imaging and to generate spatial encoding pulses, which may be nonlinear. Magnetic resonance signals originating from the selected non-planar isofield slice of the nonuniform magnetic field in the imaging region [306] are detected using the RF coils [308] in parallel receive mode. MRI images are reconstructed from the parallel received magnetic resonance signals, e.g., using algebraic reconstruction.