GB683408A - Improvements relating to x-ray apparatus and methods of radiography - Google Patents

Abstract

683,408. Radiography. SCIENTIFIC & INDUSTRIAL RESEARCH, HONORARY ADVISORY COUNCIL FOR. Feb. 7, 1950 [Feb. 10, 1949], No. 3128/50. Class 98 (i). In making radiographs with apparatus in which the X-ray sensitive material is screened from the object to be radiographed by a Bucky grid, the grid and sensitive material are mounted for adjustment about a horizontal axis which is parallel to the plane of the grid but transverse to the length of the X-ray opaque strips in it, and the grid is reciprocated in a direction parallel to the said axis through a number of cycles of progressively decreasing amplitude during an exposure. The grid may be resiliently supported, as by leaf springs, so that when set in motion it executes a series of damped vibrations. As shown, Fig. 6, the Bucky grid 21 is mounted on a frame 19 by means of spring strips 22. Frame 19 fits against a frame 28 with the grid between them, Fig. 3, and carries a lead masking member 23 running on trackways. Frame 28 has an opening the size of the film to be exposed and registering with the grid, and mask 23 has an opening 24 one quarter this size. Frame 28 also has a covering sheet of synthetic resin 29a, and trackway 31 with a high flange 32 and a low flange 33. A fluorescent screen (not shown) is hinged at one edge to a flange of frame 28, and has a lead glass covering sheet. To make an exposure, mask 23 is moved away from the opening in frame 28, and an image is obtained on the fluorescent screen. A rotating anode X-ray tube is used and operates at low power with the anode stationary for screening. A lever 45, pivoted at 46, is rocked by a spring 50 so that a headed screw 43 at one end engages a bracket 40 on the grid 21 which is thereby moved into a position with springs 22 stressed A cassette 34 is slid along trackway 31 into the exposure position, one edge engaging a roller 48 on lever 45, which is rocked to release the grid, which thereupon executes damped vibrations perpendicular to the direction of the grid elements. A switch 53 actuated by lever 45 increases the power supplied to the tube and starts rotation of the anode. The radiographic exposure is completed and the tube switched off, e.g. by timing mechanism. To expose one quarter of the cassette at a time, the mask 23 is moved into the exposure position, and a lever 56, pivoted at 57 and acting as a stop for the cassette, is turned to stop the cassette when only half is in the exposure position. The first exposure is made through opening 24 in mask 23. For the second exposure lever 56 is turned into the position shown to stop the cassette when it is wholly in the exposure position. The cassette is then rotated through 180 degrees in its own plane, and two further exposures made in the same way.