Patent GB-677813-A (GB)
Title: Improvements in x-ray apparatus
IPC: A61B6/02
Filed: 1949-10-08
Abstract: 677,813. X-ray apparatus. ZURLI, G., and REGIBUS, A. DE. Oct. 8, 1949, No. 25880/49. Class 98 (i). X-ray apparatus for laminographic radiography such as is described in Specification 508,381, wherein an X-ray tube is adjustably mounted behind an object supporting turntable carried on a common base with a film-supporting turntable, means being provided for synchronously rotating the turntables about vertical axes and for varying the height of the turntables and their spacing relatively to each other, is characterized in that means are provided enabling the central ray of the X-ray beam to be directed on to the centre of rotation of a film carried on the film-supporting turntable, said means including a light projector carried on the mounting of the film-supporting turntable for angular adjustment in a vertical plane parallel to the plane containing the axes about which the turntables are caused to rotate, said projector being adapted to project an image of a cross-wire towards a disc mounted for angular adjustment with the X-ray tube and itself provided with a cross-wire, said cross-wires being displaced horizontally in the same direction and spaced equidistantly from the centre of the film turntable and the axis of the X-ray beam respectively, a mirror at the intersection of the cross-wire on the disc, the mirror being adapted to receive the projected image of the projector cross-wire, and a screen transversely arranged with respect to the optical axis of the projector and provided with reference means concentric with the optical axis, the screen being adapted to intercept the image of the projector cross-wire reflected back from the disc mirror. As shown, Fig. 1, an X-ray tube 10 is carried on an arm 12 rotatable in a sleeve 13 slidable on a vertical column 11. An extension of arm 12 carries a sighting disc 32 carrying a central mirror 33 and cross-wires 34. A patient-supporting turntable 14 is rotatable about a vertical axis and has a seat 16 and a back-rest 18 bearing a vertical scale 19. A turntable 20, which supports a photographic film 22, has a common mounting with the turntable 14, and is rotatable in synchronism therewith about a vertical axis. The distance between the axes is variable, and both turntables are adjustable in height. An arm 23 on the mounting of turntable 20 carries a projector 24, which throws an image of internal illuminated cross-wires on to the disc 32. In use, the central ray from the X-ray tube passes through the axis of rotation of turntable 14 and falls on the centre of rotation of the film 22. The film is enclosed in a cassette and is supported at any angle, e.g. horizontally or vertically, and records an image of the body section parallel thereto. As shown in Fig. 7, the film 22 is horizontal. To align the various parts, the projector 24 is adjusted at an angle to the horizontal equal to the angle at which the central beam of X-rays-is to fall on the film 22, by means of a scale on the arm 23, and the beam is focused by means of a graduated scale to form an image on the disc 32. The tube is adjusted until the image of the cross-wires of the projector falls on the cross-wires 34, and until the image of the cross-wires. formed on a screen 43 surrounding the projector head is symmetrically placed thereon. This ensures that the central ray from the X-ray tube lies in the plane of the axes of rotation 15, 21 of the turntable 14, 20. A horizontal bar 39 is slidable on a vertical rod 37 on the common mounting of the turntables; and carries a transparent screen 41 with a horizontal line 42 in line with a pointer 40. Bar 39 is adjusted until the shadow cast by line 42 on screen 32 coincides with the horizontal cross-wire thereof. The pointer 40 then indicates the section of the body to be recorded, and may be read against a scale 19 on the back-rest 18. When the film 22 is vertical, the projector is turned until its axis is vertical, and the light rays are reflected horizontally by means on an internally-reflecting prism to fall on the disc 32, and the apparatus is adjusted as before. A radiograph may then be made by turning turntables 14, 22 in synchronism.