Method for processing of time-variable measured values saved in a four-dimensional data matrix as matrix elements (24, 27), which describe a time-variable 3D volume element and are referred to as toxels, wherein boundary hypersurfaces are determined from said measured values (24, 27) of said data matrix and represent as boundary contours a limit between measured values that are below a limit value and measured values that are above said limit value, and between which a contrast transition thus applies, wherein said measured values are medical measured values and describe as a material property the density of a tissue, and wherein said boundary hypersurfaces distinguish differing tissue regions, the method having the following steps: - reading said measured values from said four-dimensional data matrix into a computer; - identifying adjacent matrix elements (24, 27), between which a contrast transition applies; - providing one intermediate hypersurface each between said identified adjacent matrix elements (24, 27) with a contrast transition, wherein said intermediate hypersurface is an intermediate cube and corresponds to part of the boundary hypersurface to be determined; - representing an intermediate cube by a support point calculated in the center of said intermediate cube and by six connecting points at each of which two adjacent intermediate cubes make contact, wherein each connecting point is in the center of a boundary surface of said intermediate cube; - providing connecting lines each designed as double vectors between said support point and each of said six connecting points of said intermediate cubes; - stipulating paths along said connecting lines, on which said support points of said intermediate cubes of directly adjacent toxels are to be connected via connecting points in between, wherein each support point of an intermediate cube is assigned a triplet of paths and each path of a triplet leads from a connecting point of said intermediate cube to said support point and further on to another connecting point of said intermediate cube, wherein for a contrast transition in the positive direction and for a contrast transition in the negative direction corresponding paths with differing orientation ("plus", "minus") are provided; - connecting said support points and said connecting points by closed curves running along said paths with differing orientation depending on the contrast transition; - combining the partial hypersurfaces formed by the closed curves into at least one boundary hypersurface. - reading said measured values from said four-dimensional data matrix into a computer; - identifying adjacent matrix elements (24, 27), between which a contrast transition applies; - providing one intermediate hypersurface each between said identified adjacent matrix elements (24, 27) with a contrast transition, wherein said intermediate hypersurface is an intermediate cube and corresponds to part of the boundary hypersurface to be determined; - representing an intermediate cube by a support point calculated in the center of said intermediate cube and by six connecting points at each of which two adjacent intermediate cubes make contact, wherein each connecting point is in the center of a boundary surface of said intermediate cube; - providing connecting lines each designed as double vectors between said support point and each of said six connecting points of said intermediate cubes; - stipulating paths along said connecting lines, on which said support points of said intermediate cubes of directly adjacent toxels are to be connected via connecting points in between, wherein each support point of an intermediate cube is assigned a triplet of paths and each path of a triplet leads from a connecting point of said intermediate cube to said support point and further on to another connecting point of said intermediate cube, wherein for a contrast transition in the positive direction and for a contrast transition in the negative direction corresponding paths with differing orientation ("plus", "minus") are provided; - connecting said support points and said connecting points by closed curves running along said paths with differing orientation depending on the contrast transition; - combining the partial hypersurfaces formed by the closed curves into at least one boundary hypersurface.