Patent ID: 7689262

Claim:
A method for calculating a one-dimensional map of a basic magnetic field (B 0 ) for correcting image artifacts in a magnetic resonance tomographic image due to changes in the basic magnetic field, comprising the steps of: obtaining magnetic resonance signals representing magnetic resonance data from a slice of an examination subject by executing a fast magnetic resonance tomography imaging sequence applied to said slice in a B 0 field under conditions that disrupt phase-coherence over multiple executions of said sequence, said imaging sequence comprising at least three phase correction scans, and acquiring measurement signals representing data points for each of said phase correction scans; calculating a phase difference between corresponding data points respectively in two of said phase correction scans for said slice, for which said measurement signals were acquired in a same readout direction for all data points in said two of said phase correction scans on a point-by-point basis; identifying an average phase difference for said two of said phase correction scans by adapting a mathematical function; determining an adjusted resonant frequency from said average phase difference and from echo time differences between said two of said phase correction scans, and calculating a frequency offset between an actual resonant frequency and said adjusted resonant frequency; calculating a B 0 field map of said B 0 field dependent on said frequency offset; dependent on said mathematical function, correcting shimming of said B 0 field in said readout direction; and after correcting said shimming of said B 0 field, correcting said magnetic resonance data for said slice using said B 0 field map.