US Patent 10145913 Methods and apparatus for magnetic field shimming

According to some aspects, a method of producing a permanent magnet shim configured to improve a profile of a B0 magnetic field produced by a B0 magnet is provided. The method comprises determining deviation of the B0 magnetic field from a desired B0 magnetic field, determining a magnetic pattern that, when applied to magnetic material, produces a corrective magnetic field that corrects for at least some of the determined deviation, and applying the magnetic pattern to the magnetic material to produce the permanent magnet shim. According to some aspects, a permanent magnet shim for improving a profile of a B0 magnetic field produced by a B0 magnet is provided. The permanent magnet shim comprises magnetic material having a predetermined magnetic pattern applied thereto that produces a corrective magnetic field to improve the profile of the B0 magnetic field.