A Surface Landmark Chart for Use in X-Ray Examinations of the Trunk

Abstract

THE ability to place patient, x-ray tube, and film in such relationship that some selected anatomical structure in the chest, abdomen, or pelvis shall appear at the center of the finished roentgenogram is an accomplishment much to be desired in a roentgenologist or his lay helper. Two general problems are involved: first, one must line up tube and film until the target lies perpendicularly above the center of the film; second, one must know what point on the skin of the patient's body lies directly above the anatomical structure selected for examination. The first of these problems is more or less time-consuming if commercial types of apparatus are employed. In this particular laboratory it has been disposed of by equipping all exposing tables with special tube arms similar to the one on the obstetrical table described by Hodges and Ledoux. When these tube arms are locked to the Potter grid and are made to stand at 90° to the table top, the target of the x-ray tube lies perpendicularly above the center of the film. The second problem is the subject of the present dissertation. Sitting Height.—The sitting height of a subject is obviously closely related to the length of his spine and so this measurement was the first one used. Subjects were made to sit on a stool, their backs against a standard height board, and then, after sitting height had been measured, they were placed back down on the x-ray table. Measuring downward from the vertex along the anterior surface of the body in a plane parallel to the table top, a point was located halfway from crown to rump. The patient was now arranged on the table so that this ½ S. H. (half sitting height) point lay along an imaginary perpendicular joining the target of the x-ray tube and the center of the film, and the exposure was made. In six adults ranging in build from short and fat to tall and lean, this one-half sitting height point was found to correspond to that portion of the spine bounded above by the center of the eighth thoracic vertebra, below by the center of the ninth thoracic vertebra. In one eight-year-old child it corresponded to the body of the eighth thoracic and in another, six years old, to the seventh thoracic vertebra. However, sitting height does not lend itself well to such work because the measurement cannot be made as the patient lies on the table ready for examination. S. S. Axis (suprasternal notch—symphysis pubis axis).—Obviously the measurement of choice should be related to landmarks on the anterior surface of the body. Several such landmarks on examination proved unsatisfactory: the umbilicus did not have a constant relationship to spinal segments and the costal margin, iliac spines, and iliac crests could not be palpated with sufficient precision.