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:
Sep. 12, 1995
Filed:
Jun. 29, 1993
Peter Van Der Meulen, Eindhoven, NL;
Gerrit H Van Yperen, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
In an MRI device (1) operating according to a spin-echo method, switched gradient magnetic fields are applied in the form of slice selection (231-233), phase encoding (243-243, 243'243') and read gradients (252-253). The switching of the gradients causes eddy currents in metal parts of the apparatus. The eddy currents disturb the applied magnetic fields, thereby changing the phases of the precessing nuclear spins of a body (7) to be examined and causing artefacts in a reconstructed image. Another source of disturbance may be phase-distortion in the RF amplifier. By modifying a gradient (251, 231') in between the excitation pulse (221) and the first refocusing pulse to (222) in the spin-echo sequence and/or a change in phase of the RF-pulses, the effects of the disturbances can largely be compensated for. The additional gradient size is adjusted by measuring the position in time and the relative phase of spin-echo signals (162, 163) in a preparatory sequence (121-173).