Image distortion in rotational panoramic radiography. IV. Object morphology; outer contours.

On films exposed with rotational panoramic radiography, distortion effects are often apparent. The distortion of the outer contour of three-dimensional model objects jas been analysed mathematically. The applied mathematical expressions for coordinate transformation between object and film were confirmed experimentally. The distortion of the outer contour is dependent on the basic form of the object; the more rounded the object is, the less marked is the distortion. It is concluded that for practical clinical purposes the correctly exposed panoramic film is reliable when the form of rounded objects is assessed.