A Device to Allow the Use of a Tomograph on a Tilting Table

Abstract

The problem which led to the development of this device was one concerned with air myelography in the diagnosis of lesions of the lower spinal canal, particularly ruptured nuclei pulposi. We desired to use a tomograph, but this was impossible since the patient must be kept in the Trendelenburg position. The ordinary tomograph requires a horizontal or vertical table, as the tube must run horizontally along the rail or vertically along the tube stand. The device described below allows the table to be placed at any angle, and at the same time the tube always runs parallel with the table by means of a compound motion of the tube carriage on the vertical tube stand and the horizontal rail. The device consists of three main parts. A separate rail has been attached at the side of the table and parallel with the top by means of two brackets (Fig. 1). This is a steel bar 1∕2 × 11∕4 in. in size. The carriage was made of two pieces of 1∕4-in. steel plate 14 in. long between which were mounted four ball-bearing rollers. This was fitted over the extra rail, and the bearings roll in grooves on the top and bottom edges. The third portion of the device consists of two light steel rods made of 3∕16 × 1 in. steel perforated for adjustment and attached by means of bolts near the ends of the carriage. Both upper ends are attached together by means of a bolt and thumb nut to the tube carriage on the vertical tube stand, thus forming a triangle. Since the rail is parallel with the table top and the carriage must run along it, then by simple triangulation the tube must also run parallel with the rail and table top. The tomograph is one made by the Standard X-ray Corporation, and was remodeled to fit the General Electric R-36 table. It consists simply of an arm attached to the tube carriage rails and extends through an adjustable fulcrum to a pivot at the level of the x-ray plate (Fig. 2). This pivot is attached to the Bucky by means of three steel bars arranged to clear the edge of the table. The device works very satisfactorily as regards the anteroposterior examination of the air-filled spinal canal. This portion of the examination shows extremely well the air-filled subarachnoid space with a definitely outlined dural tube, and occasionally nerve sheaths are clearly visualized (Fig. 3). At the present time we have not been completely satisfied as to the views in the lateral position, but this we hope to overcome with further experience. We have been able definitely to rule out lesions at the lumbosacral junction. With ordinary air myelography, this has been difficult. Our procedure has been to take ordinary films preliminary to the injection of air so as to rule out anatomic defects in the bone. After the air has been introduced, anteroposterior and lateral plain films are taken.