METHOD FOR ACCOMPLISHING IN VIVO QUICK SHIM ACTION FOR MAGNETIC FIELD

PROBLEM TO BE SOLVED: To quickly and accurately correct non-uniformity within a magnetic field considering effect of a subject by a method wherein an inversely partial differential matrix is multiplied by a coefficient of a partial differential nonuniformity map to determine a shim current and the current is fed to individual coils to generate a more uniform magnetic field. SOLUTION: This system is constituted of a general purpose minicomputer functionally linked to a disc memory unit 2a and an interface unit 2b. A wireless frequency (RF) transmitter 3, a signal equalizer 4 and gradient power sources 5a, 5b and 5c apply energy to gradient coils 12-1, 12-2 and 12-3 to generate magnetic field gradients Gx , Gy and Gz individually in directions 'X', 'Y' and 'Z' of the subject for imaging. A gating of the RF transmitter 3 is made by a pulse envelop from the minicomputer 2 to generate an RF pulse having a necessary modulation for exciting a magnetic resonance response signal from the subject.