A method of determining an internal three-dimensional thermally distinguishable region in the living body is disclosed. The method comprises obtaining a synthesized thermospatial image defined over a three-dimensional spatial representation of the living body and having thermal data arranged gridwise over a surface of the three-dimensional spatial representation in a plurality of picture-elements each represented by a intensity value over the grid. The method further comprises searching over the grid for at least one set of picture-elements represented by generally similar intensity values. For at least a few sets of picture-elements, the method defines a plurality of loci, each locus being associated with at least a pair of picture-elements of the set and defined such that each point of the locus is at equal thermal distances from individual picture-elements of the pair. The plurality of loci is used for determining the internal three-dimensional thermally distinguishable region.
