Patent ID: 7605589
Filing Date: 2009-10-20
Classification: G01R

Abstract:
1. A method for homogenising a static magnetic field with a magnetic field distribution B 0 (r) for nuclear magnetic resonance spectroscopy by adjusting the currents C i through the shim coils, thus creating spatial field distributions C i ·S i (r), where r stands for one, two, or three of the spatial dimensions x, y, and z, and said magnetic field distribution B 0 (r) has only a field component along z, in a working volume of a magnetic resonance apparatus with one or more radio frequency (=RF) coils ( 5 ) for inducing RF pulses and receiving RF signals within a working volume, said RF coils having a spatial sensitivity distribution of magnitudes B 1 k (r), and with shim coils ( 6 ) for homogenising the magnetic field within the working volume, said shim coils ( 6 ) being characterised by their magnetic field distributions per unit current S i (r) and having components only along z, the method including the following steps: (a) Mapping the magnetic field distribution B (b) calculating a simulated spectrum I (c) optimising a quality criterion derived from the simulated spectrum I (d) realising the found optimum of the quality criterion of step (c) by generating the associated target field distribution B