Nuclear magnetic resonance scanners with composite pole facings

摘要

A medical NMR scanner having a primary field magnet assembly is disclosed. The scanner includes a ferromagnetic frame defining a patient-receiving space adapted to receive a human body. It also includes a pair of opposed polar regions aligned on a polar axis. The polar regions are disposed on opposite sides of the patient-receiving space. Structure including either electrical windings or a permanent magnet is provided in each of the polar regions for producing a magnetic field within the patient-receiving space. Windings positioned in proximity to each of the polar regions are provided for producing gradients in the magnetic field, when energized. A plurality of ferromagnetic elements positioned in side-by-side relation to one another in each of the polar regions is provided for limiting eddy current generation in the polar regions when the gradient producing auxiliary coils are energized. Each of the ferromagnetic elements has its shortest dimension oriented generally perpendicular to the polar axis. The ferromagnetic elements comprise rods which are positioned generally parallel to one another and to the polar axis in one form of the invention. In another form of the invention the ferromagnetic elements comprise generally rectangular, planar laminations the planes of which are positioned generally parallel to the polar axis.