1. An imaging system comprising: a CT scanner; a first storage unit storing a plurality of transverse images taken by the CT scanner; an image conversion unit producing a two-dimensional cross sectional image on the basis of the transverse images, for which the transverse images are arranged in a direction perpendicular to a transverse plane; a second storage unit storing the cross sectional image; a peak detection unit extracting an outline of the cross sectional image for detecting relative extreme peaks of the outline; a peak interpolation unit carrying out interpolation on the basis of a specified standard for an outline between the relative extreme peaks detected by the peak detecting unit; and an image construction unit reconstructing the cross sectional image stored in the second storage unit using the outline interpolated by the peak interpolation unit.