Objective Otologic Roentgen Stereoscopy and its Significance for the Roentgen Diagnosis of Diseases of the Mastoid Process

Abstract

ROENTGEN technical improvements in the demonstration of the temporal bone, especially its petrous portion, still are welcome as the exploration of this area, due to its complicated structure, is quite difficult. Any methods permitting of correct identification and spatial correlation of the various superimposed structural shadows deserve critical evaluation. It is presupposed in this paper that the reader is familiar with various typical projections of the temporal bone, especially those devised by Schüller, Stenvers, and Mayer; furthermore, that he is familiar with the principles of roentgenstereoscopy.2 The three special projections of Schüller, Stenvers, and Mayer are regarded as sufficient for satisfactory demonstration of all detail desirable. The Schüller projection furnishes a good survey of the entire pneumatic system, the course of the venous sinus, and the ala of the temporal bone; the apex of the mastoid process also may be readily differentiated. The Mayer projection demonstrates to best advantage the spaces of the middle ear, especially the attic, and the mastoid antrum, while the Stenvers projection is chosen when information is desired concerning the apex of the pyramids, the labyrinth, and the tegmen. All other projections—more than twenty have been recommended in the roentgenologic-otologic literature—may be omitted without sacrifice, when correct stereoscopic projections in the three types mentioned, are secured. Tautomorphic roentgen stereoscopic demonstration of the temporal bone with any of the common oblique projections has not been described previously, though, of course, stereoscopic procedures, as, for instance, inherently incorporated into the Reaves “Radiographscope” and the Hasselwander “Stereoskiagraph,” point toward correct application of physical laws with such projections. As long as it is possible to reproduce conditions of projection during visual observation of stereoscopic images, all distortions due to oblique projections may be visually eliminated so that correct spatial relationship is not only perceived but may also be proven by stereoscopic measurements. Therefore, if one will record the angles of inclination, besides all other stereoscopic data; if one, furthermore, will devise a viewing apparatus, permitting of a reproduction of such angles, then correct spatial evaluation is possible. Many of the tube stands commonly in use for roentgenography are equipped with calibration, which permits one readily to record any angle of inclination of the inciding roentgen-ray beam. Roentgen stereoscopes commonly in use have no such calibration; many of them permit of a rotation of the viewing boxes around a vertical axis in a horizontal plane, but they do not permit of an inclination of these boxes around a horizontal axis.