Patent ID: 6064208
Filing Date: 2000-05-16
Classification: G01R

Abstract:
A method of shimming a main magnetic field in a magnetic resonance imaging apparatus comprising:(a) generating a radio frequency pulse sequence while a subject is in an examination region of the magnetic resonance imaging apparatus;(b) acquiring a reference signal which is immune to shim errors;(c) acquiring a field echo signal which is sensitive to shim errors at a time interval equal to a multiple of an amount of time it takes for fat and water signals to become in-phase;(d) comparing a temporal position of a maximum of the field echo signal to its predicted temporal position relative to the reference signal;(e) calculating a shim term based on the comparison of step (d);(f) applying an electrical current to one of a gradient offset and a shim coil such that the main magnetic field is adjusted according to the shim term.