Method and apparatus for compensating for nonuniformity of static

Abstract

A method and apparatus for compensating for nonuniformity of a static magnetic field in a MRI system wherein one of X-, Y- and Z-axes of a Cartesian coordinate system is selected as a phase encoding direction, a region of a field of view is selectively excited by applying a high frequency pulse of a predetermined angle to an object under inspection, and an NMR signal is measured by applying a phase encoding gradient magnetic field and a frequency encoding gradient magnetic field after application of the high frequency pulse for a plurality of times while changing the phase encoding gradient magnetic field. A peak value is detected of the measurement data obtained for determining a phase encoding quantity at which the peak value can be obtained, an intensity and a polarity of a linear component of nonuniformity components of the static magnetic field in the direction selected is determined by obtaining an intensity and a polarity of the phase encoding gradient magnetic field corresponding to the peak value, and a pulse sequence for measuring the NMR signal is executed by applying a gradient magnetic field added with a compensating gradient magnetic field having the same intensity as the linear component and a polarity opposite to the linear component to a gradient magnetic field applied in the selected direction.