A disclosed method includes: defining two first points in a model cross section of a model of an object and two corresponding second points in an image that is a cross section of the object for a reference time； performing first transforming including expansion or reduction for the model cross section so that a position of a second point is identical to a position of a corresponding first point； superimposing the image and the model cross section after the performing； second transforming a second model cross section for a second time after the reference time, so that positions of two second points in a second image for the second time are almost identical to positions of corresponding two first points in the second model cross section； and superimposing the second image and the second model cross section after the second transforming.
