Shim method with determination of the target field distribution by optimization in a parameter space of reduced dimension.

摘要

The invention relates to a method for homogenizing the static magnetic field with a distribution B0 (r) in the working volume of a magnetic resonance device with N shim coils comprising the following steps: (a) mapping (21) of the magnetic field distribution B0 (r), (b) Determining (22) a target field distribution B0T (r), (c) generating (23) the target field distribution B0T (r) in the working volume by adjusting the shim currents, wherein in step (b) an optimization method for optimizing a numerical quality criterion for the target field distribution B0T (r ), which as a result provides values for the N shim currents, and wherein a spatial weighting function is used, is characterized in that a filtering method is used in which filter norms influence a norm of the shim currents and in that the optimization method is in a parameter space with M control parameters, where 2 ≤ M N, where one of the control parameters is a weighting parameter is used to modify a spatial weighting function and another control parameter to control the filter factors. In this way, the hardware limitations can be taken into account when determining the target field distribution (22), without the computational outlay in the optimization for determining the target field distribution (22) being significantly greater.