A method is presented to calculate the relative contribution of different tissues, or tissue mix, to at least one data element in a medical object data set, the medical object data set containing data elements, the data elements assigning data values to respective positions in a multi-dimensional geometrical space containing more than one tissue, by means by which parameters are calculated for the at least one data element, the parameters being dependent on the data value of the at least one data element and data values of surrounding data elements in the neighborhood of the at least one data element, the parameters being further compared to combinations of said parameters for data elements occurring in the region of boundaries between tissues.