METHOD FOR HIGH-SPEED CORRECTION OF MAGNET

PURPOSE: To reduce the time necessary for shimming and to measure non- homogeneity with good spatial resolving capacity by obtaining two NMR images different in phase developing times and developing a magnetic field formed by a shim coil to an approximate polynominal expression. CONSTITUTION: First and second NMR view sets are obtained on the basis of first and second different developing times tE1 , tE2 . The first and second complex multipixel images corresponding to the respective NMR view sets are re-constituted and one of two these images is divided by the other one of them at every pixels to form a complex multipixel ratio image and the non-homogenous map of a polarizing magnetic field is obtained by the declination thereof. Next, the magnetic field formed by a shim coil is developed to one set of approximate polynominal expressions and a non-homogenous map over vol. concerned is applied. The values of the coefficients of the polynominal expressions after development are approximate to a necessary shim coil current. A correction matrix is determined from the corresponding polynominal expressions and used along with the coefficients of these polynominal expressions to adjust the energizing of the shim coil.