Patent ID: 6696835
Filing Date: 2004-02-24
Classification: G01R

Abstract:
A second order static magnetic field correcting method comprising the steps of:disposing a first circular loop coil and a second circular loop coil at positions spaced in a static magnetic field to be symmetrical with respect to a center of an imaging region of an MRI apparatus; disposing a third circular loop coil and a fourth circular loop coil having a larger diameter than that of said first and second circular loop coils at positions spaced in said static magnetic field direction to be symmetrical with respect to said center of said imaging region; generating a first corrective magnetic field in a first direction by said first circular loop coil, and generating a second corrective magnetic field in the same direction as said first direction of said second circular loop coil; generating a third corrective magnetic field in a second direction by said third circular loop coil, and generating a fourth corrective magnetic field in the same direction as said second direction by said fourth circular loop coil, wherein said second direction is opposite to said first direction; and providing said static magnetic field in a direction which is parallel to said first direction; thereby correcting second order static magnetic field components in the static magnetic field direction; wherein at least one of the ratios of electric currents and the turns of ratio of said first through fourth circular loop coils is determined so that zeroth order corrective magnetic field components in said static magnetic field direction cancel one another.