Patent ID: 6275038
Filing Date: 2001-08-14
Classification: G01R

Abstract:
A method for measuring the inhomogeneity in a magnetic polarizing field at a point in a slice of a subject to which a magnetic polarizing field is applied to acquire an MRI image of a slice said method comprising:(1) acquiring data in a k-space for first and second k-space scans of said subject with a single application of a first MRI pulse sequence, wherein said MRI pulse sequence, comprises:(a) a train of alternating polarity read gradient pulses having substantially same magnitude and duration, wherein said slice is perpendicular to a z axis of a spatial coordinate system and said read gradient pulses provide magnetic field gradients in said slice in an x direction of said coordinate system;(b) a train of substantially identical phase gradient pulses that provide a magnetic field gradient in a y direction of said coordinate system and wherein a phase gradient pulse occurs after every other read gradient pulse in said train of read gradient pulses; and(c) wherein data acquisition for said second k-space scan is delayed with respect to data acquisition for said first k-space scan by a time delay;(2) generating first and second spatial images from said first and second k-space scans;(3) determining a phase difference between values of said first and second spatial images at said point; and(4) measuring said the inhomogeneity at said point using said phase difference and said time delay.