Closed superconductive magnet with uniform imaging volume

摘要

A closed magnetic resonance imaging (MRI) magnet has a single superconductive coil assembly including a toroidal-shaped coil housing containing a pair of superconductive main coils and at least one additional superconductive main coil. A pair of generally-non-permanently-magnetized ferromagnetic rings is spaced radially inward and apart from the superconductive main coils. The ferromagnetic rings allow the design of a shorter MRI magnet because the ferromagnetic rings overcome the gross magnetic field distortions in the imaging volume of the magnet (created by removing some of the additional longitudinally-outermost superconductive main coils, otherwise used in the magnet, to make the magnet shorter) to produce a magnetic field of high uniformity within the imaging volume.