Means to correlate images from scans taken at different times including means to determine the minimum distances between a patient anatomical contour and a correlating surface

Herein is described a method for creating composite images from disparate sets of tomographic images. The images may be derived from CAT, MRI or PET systems. Initially, a "head" is created from one set of tomographic image slices. The head comprises a three dimensional stack of contours created from such slices. A "hat" is created from another set of tomographic image slices with the hat being described by a plurality of points with coordinate positions which define the three dimensional surface of stack of image slices. The hat is then superimposed over the head and subsequently, a determination is made by examination of side and top planar views of the hat and head, of a factor which defines the mean distance of the hat points from the head contours. The hat is subsequently adjusted relative to the head until the mean distance is found to be within minimum limits.