1. A method for a 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 larger or higher values, and a background mask containing background data corresponding to lower values by applying a first 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 first 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 second specific threshold value to the data resulting from the filtering operation, and correlating the data set obtained by applying the second specific threshold value to the data resulting from the filtering operation with the foreground data of the foreground mask; generating a restrictive mask by subjecting the less restrictive mask to a labeling with respect to a determination of local values of each individual locally defined region or cluster, and determining median values of the respective locally defined regions, and subjecting the values obtained in the labeling for 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 locally defined regions of the restrictive mask proceeding from the individual segmentation starting points; continuing a growth of these locally defined regions in the less restrictive mask; and viewing the locally defined regions obtained in the restrictive mask as segmented brightness regions.