Patent ID: 7423431

Claim:
A permanent magnet assembly for an imaging apparatus comprising a permanent magnet body having a first surface and a stepped second surface which is adapted to face an imaging volume of the imaging apparatus, wherein the stepped second surface contains at least four steps, the permanent magnet body comprising: a cylindrical base section having a major first surface attached to the at least one layer of a soft magnetic material and a major second surface having at least three steps such that at least two of the steps in the second surface of the base section are machined into the second surface of the base section, wherein the second surface of the base section is opposite to the first surface of the base section, wherein the base section comprises at least two layers of permanent magnet blocks, and wherein the at least one layer of the soft magnetic material is attached to a substantially flat first surface of the permanent magnet body; a hollow ring section attached to an outer portion of the second surface of the base section, wherein the first and second surfaces of the base section and the first and second surfaces of the hollow ring section are arranged substantially perpendicular to a direction of a magnetic field of the magnet assembly, wherein the stepped second surface of the permanent magnet body comprises the second surface of the hollow ring section and a portion of the second surface of the base section that is not covered by the ring section, and wherein the second surface of the ring section extends at least 0.05 meters above an outer step on the second surface of the base section to form a pocket.