X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Patent
1984-04-18
1987-05-26
Howell, Janice A.
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
378135, 378137, A61B 600, H01J 3504
Patent
active
046691022
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with a method and a device designed to direct and focus a tomographic x-ray unit employing an electron beam. Such a unit embodies at least one electron gun and an anode at which it is aimed as well as the x-ray detectors needed to produce a tomographic image.
As a source of radiation, tomographic equipment generally employs an x-ray tube which, during exposure, revolves around the object to be photographed. However, it is not possible to attain such a high rate of revolution for the x-ray tube as to make the equipment suitable for photographing fast-moving organs of the human body, such as the heart region. In practice, exposure times shorter than 1 second cannot be achieved, although exposure times in the order of 0.1 seconds would be required to produce adequate pictures of the heart region, or brain blood circulation when using a contrast medium.
In order to achieve sufficiently short exposure periods, equipment has been devised in which the x-ray tube is replaced with an electron gun generating an electron beam which is focused and magnetically directed at a fixed anode encircling the object.
The problem associated with this construction is how to direct and focus a high-intensity, high-energy electron beam, and how to stabilize the high voltage involved which affects the aforementioned factors.
This invention is an attempt to avoid these problems and to accomplish a method and a device which does not require focusing of the electron gun, nor accurate collimation of the beam. Also, no requirements are set for high-voltage stabilization from the point of view of beam focusing or direction. Beam directing is effected mechanically by means of a focusing ring, and focusing is achieved in the space between the focusing device and the anode where also the actual acceleration of electrons takes place. Characteristic of the method under consideration is that the beam emitted by the electron gun is roughly aimed at a hole in the focusing ring which, by means of focusing field lines, draws the electrons into the hole as well as focuses and accelerates the electron beam, directing it at the anode disc to produce an x-ray source. Moreover, the focusing hole is moved in regard to the anode in such a way as to generate a mobile x-ray sourcewhich produces a "layerwise" photograph of the object under examination.
Another characteristic feature of this method is that the focusing plane has zero potential for which reason the acceleration of the electrons takes place between the focusing surface and the anode. Furthermore, the field lines generated by the potential between the focusing plane and the anode extend partly to the space between the focusing plane and the electron gun, thus drawing the electrons into the focusing hole like a hopper.
Another characteristic feature of this method is that the anode and the focusing plane are in the form of concentric rings, and that the focusing plane is caused to revolve at a uniform speed, and that the electron gun is timed to emit the beam in pulses whereby it hits the anode at evenly spaced points. In addition to a ring-shaped anode and focusing plane, the object is surrounded by a ring of x-ray detectors, for which reason the most appropriate form of the apparatus is that of a funnel or a cylinder.
Furthermore, it is characteristic of the method that several electron guns are mounted along the casing of a basically cylinder-shaped apparatus so that the beams emitted by them are roughly deflected in the direction of the tangent of the casing towards the holes in the focusing plane numbering from one to several to each gun. In this way, each deflected beam is directed at a specific portion of the anode disc. During irradiation, the focusing ring turns a distance equivalent to the distance between two holes. The deflection of the electron beam can be effected as one-level rough deflection which permits the use of two focusing holes to each gun.
Furthermore, it is characteristic of the method based on this invention that, when the focusing ring turns
REFERENCES:
patent: 4045672 (1977-08-01), Watanabe
patent: 4135095 (1979-01-01), Watanabe
patent: 4274005 (1981-06-01), Yamamura et al.
patent: 4287425 (1981-09-01), Elliott, Jr.
patent: 4300051 (1981-11-01), Little
Howell Janice A.
Puumalaisen Tutkimuslaitos Oy
LandOfFree
Method and device for operating and focusing tomographic X-ray e does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for operating and focusing tomographic X-ray e, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for operating and focusing tomographic X-ray e will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-708694