A method is disclosed for automatically finding the true axis and the radius of cross sections of three dimensional tube-like shaped objects such as the left head ventricle, lung airways and blood vessels from 3-D transverse images constructed from known imaging techniques. The problem of finding the center axis of a 3-D tube-like shape is reduced to searches for the center points of its cross sections. The true axis of the tube-like shaped object is defined as the 3-D curve which connects all detected center points of all cross sections. Additionally, a method is disclosed for automatic determination of the center and the radius of each cross section of the tube-like shape, which may be irregular or incomplete, by analyzing the average intensity of the image intensity patterns in transverse image slices of the cross section. The curved axis detected by this method can then be used as the spatial reference to reslice the image volume for accurate medical related diagnosis or industrial non-destructive inspection.