Structures of the midface on cylindrical pantomograms

The paper presents the anatomical structures of the middle third of the face as they are visualized in cylindrical pantomograms, in the projections found to give maximum information in my earlier experimental study (Altonen 1972). The pantomograms are taken with the prototype equipment developed since the earlier study, which can be used to take orthopantomograms, concentric patomograms of the desired shape, and linear tomograms. With this equipment, the patient can be examined while lying down, and experiments with corpses of road traffic victims have shown that it is particularly useful for diagnosing fractures in the middle third of the face. Maximum information is given by a projection in which the radiation beam traverses the region to be visualized parallel to the Frankfort plane, and in which the diameter of the cylindrical image layer corresponds to the width of the middle third of the face. The central part of the middle region is visualized best in ca. 30 degrees retroversion, with the exception of the alveolar process of the maxilla, the hard palate and the dentition. The best reproduction of the lateral areas of obtained in ca. 25 degrees anteversion. The contusing shadows cast by the cranial base in radiography of the middle facial region can be shifted from the area to be examined by tilting the head forward or backward, or positioning the rotational axis of the beam dorsally to the porion-porion line. Thin shadows can also be shifted by using stereoscopic pantomography.