Patent ID: 9329254
Filing Date: 2016-05-03
CPC Classification: G01R

Claim Text:
1. A method to correct phase information in magnetic resonance (MR) images of a volume segment of an examination subject, comprising; placing an examination subject in an MR data acquisition unit and operating the MR data acquisition unit to apply a basic magnetic field at least to a predetermined volume segment of the examination subject and to acquire MR data from the predetermined volume segment, said MR data representing image elements of said predetermined volume segment; detecting a navigator signal originating within said MR data acquisition unit during acquisition of said MR data; in a processor, evaluating said MR data to calculate phase information for each of said image elements of said predetermined volume segment; in said processor, using said navigator signal to determine a change in said basic magnetic field caused by a source selected from the group consisting of movement of the examination subject, and said MR data acquisition unit itself; determining a first reference phase value by detecting transverse magnetization in said examination subject in a reference measurement in which said navigator signal is not phase coded, using free induction decay, during a first time interval after said RF excitation; determining a second reference phase value by transverse magnetization of an echo signal resulting from said navigator signal being detected in a center of k-space in said reference measurement at a second time interval after said RF excitation; determining a first phase value by detecting the transverse magnetization in a measurement with a measurement signal that is not phase coded using the free induction decay after said first time interval after said RF excitation; determining a second phase value by detecting the transverse magnetization of an echo signal resulting from the measurement signal during said measurement in the center of k-space after a second time interval after the RF excitation; correcting said MR data during entry thereof into k-space dependent on said first reference phase value, said second reference phase value, said first phase value and said second phase value; determining a factor F dependent on time t according to wherein Δφ and Δω are calculated according to wherein φ R,1 is the first reference phase value, φ R,2 is the second reference phase value, φ n,1 is the first phase value, φ r,2 is the second phase value, T 1 is the first time interval and T 2 is the second time interval; correcting the MR data by multiplying the MR data with the factor F at time t; and from said processor, making said MR data with the corrected phase information available in electronic form at an output of said processor, as a data file.