The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 27, 1996
Filed:
Apr. 13, 1995
Mark A Richard, Cleveland Hts., OH (US);
Michael A Morich, Mentor, OH (US);
Labros S Petropoulos, Solon, OH (US);
Picker International, Inc., Highland Heights, OH (US);
Abstract
A toroidal housing (18), such as a vacuum dewar, contains magnets (10, 12) for generating a temporally constant magnetic field through a central bore (14). Gradient coils (32, 42) are mounted around the bore defining a space therebetween. A radio frequency shield (78) is disposed radially inward from the gradient coils. Inside the radio frequency shield, an inner shimming assembly (60) includes a dielectric cylinder (62) having annular grooves around its periphery. Segmented ferrous material (66) is arranged in annular rings in the grooves. The ferrous material is segmented into small pieces electrically insulated from each other to limit radio frequency and gradient frequency eddy currents. A radio frequency coil (70) is mounted inside of the annular ferrous shims (66). Preferably, additional shim trays (50) which carry shims (54) are mounted in the space between the primary and secondary gradient coils.