1. A method for the segmentation of locally defined, two-dimensional regions, the method which comprises: separating input data acquired from an image region under investigation into a foreground mask containing foreground data corresponding to relatively larger or higher values, and a background mask containing background data corresponding to relatively lower values by applying a threshold value; subjecting the input data to two different filtering operations to determine segmentation starting points, with a filter reducing sharp contours or contrasts, and a filter for determining local maxima in a region; subtracting the data sets resulting from the two different filtering operations and defining image regions having a specific threshold value or threshold value range as segmentation starting points; generating a less restrictive mask by subjecting the input data to a filtering operation accentuating high-frequency parts or a filtering operation detecting edges, and applying a specific threshold value to the resulting data, and correlating the data set obtained therewith the data of the foreground mask; generating a restrictive mask by subjecting the less restrictive mask to a labeling with respect to the determination of local values of each individual locally defined region or cluster, and determining median values of the respective regions, and subjecting the values obtained in each cluster to a discrimination with a preset threshold value; eliminating segmentation starting points not contained in the less restrictive mask; effecting a growth in the respective regions of the restrictive mask proceeding from the individual segmentation starting points; continuing a growth of these regions in the less restrictive mask; and viewing the regions obtained in the restrictive mask as the segmented brightness regions.