A simple accurate plane and incline indicator.

Abstract

At the Long Island College Hospital (Brooklyn, N. Y.), where a large number of myelographic examinations are performed, it has become apparent to us that a simple means for recording on film the degree of table inclination would be of great value. Accordingly, we have designed a simple indicator which records accurately the degree of table tilt on each spot film. This indicator consists primarily of a mercury droplet enclosed in a hollow glass tube which has been bent to form a semicircle and sealed at both ends. The tube is encased in a block of wood or plastic (Fig. 1) so grooved that it may be affixed to the spot-film device. The system is semiopaque except for the mercury droplet; thus a shadow will be cast on both the fluoroscopic screen and the exposed film. The glass tube will appear as a rectangular column, within which lies the opaque droplet. Since the indicator depends upon gravity for operation, it follows that the mercury droplet will appear in the center of the column when the table is horizontal and will gravitate toward either extremity of the column depending upon the degree of inclination in either the Trendelenburg or erect position. The indicator may be constructed by heating and bending ordinary glass tubing of 4 mm. diameter into a semicircle having a 3 cm. radius. After sealing a mercury droplet within the lumen, the tube may be enclosed in a small block of white pine or lucite which has been grooved for attachment to the spot-film device. The degree of tilt can then be calibrated and labeled by affixing lead numerals at appropriate points on the block, parallel to the long axis of the glass tube. This simple inexpensive device has proved of great value in myelography and its use is planned in other radiographic examinations in which the inclination of the table should be known during interpretation of the film.