A method of determining a spatial distribution of magnetic particles with non-linear magnetization characteristics in an examination area, comprising the steps a) generating a first, temporally constant magnetic field with a spatial course of the magnetic field strength such that in the examination area there is a first part-region having a relatively low magnetic field strength where the magnetization of the magnetic particles is not saturated and a second part-region having a relatively high magnetic field strength where the magnetization of the magnetic particles is saturated, b) changing the spatial position of the two part-regions (301, 302) in the examination area so that the magnetization of the particles changes locally, c) recording real measured values which depend on the magnetization in the examination area, said magnetization being influenced by the change in position of the two part-regions (301, 302), d) reconstructing the spatial distribution ( c) of magnetic particles in the examination area from the real measured values, characterised by means of the following steps: - providing a transfer function which, applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, supplies fictitious measured values, and also providing a regularization parameter (λ) and a regularization functional which can be applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, - determining a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, such that a sum which comprises as summands i) the difference of the real measured values from fictitious measured values which are determined by applying the transfer function to the dependence distribution, and ii) the product of the regularization parameter (λ) and of a regularization value which is determined by applying the regularization functional to the dependence distribution, is minimized, e) determining the spatial distribution ( c) of magnetic particles from the determined dependence distribution. a) generating a first, temporally constant magnetic field with a spatial course of the magnetic field strength such that in the examination area there is a first part-region having a relatively low magnetic field strength where the magnetization of the magnetic particles is not saturated and a second part-region having a relatively high magnetic field strength where the magnetization of the magnetic particles is saturated, b) changing the spatial position of the two part-regions (301, 302) in the examination area so that the magnetization of the particles changes locally, c) recording real measured values which depend on the magnetization in the examination area, said magnetization being influenced by the change in position of the two part-regions (301, 302), d) reconstructing the spatial distribution ( c) of magnetic particles in the examination area from the real measured values, characterised by means of the following steps: - providing a transfer function which, applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, supplies fictitious measured values, and also providing a regularization parameter (λ) and a regularization functional which can be applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, - determining a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, such that a sum which comprises as summands i) the difference of the real measured values from fictitious measured values which are determined by applying the transfer function to the dependence distribution, and ii) the product of the regularization parameter (λ) and of a regularization value which is determined by applying the regularization functional to the dependence distribution, is minimized, - providing a transfer function which, applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, supplies fictitious measured values, and also providing a regularization parameter (λ) and a regularization functional which can be applied to a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, - determining a dependence distribution which depends on a spatial distribution ( c) of magnetic particles, such that a sum which comprises as summands i) the difference of the real measured values from fictitious measured values which are determined by applying the transfer function to the dependence distribution, and ii) the product of the regularization parameter (λ) and of a regularization value which is determined by applying the regularization functional to the dependence distribution, i) the difference of the real measured values from fictitious measured values which are determined by applying the transfer function to the dependence distribution, and ii) the product of the regularization parameter (λ) and of a regularization value which is determined by applying the regularization functional to the dependence distribution, e) determining the spatial distribution ( c) of magnetic particles from the determined dependence distribution.