X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Patent
1996-12-04
1998-08-04
Wong, Don
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
378 983, H05G 110
Patent
active
057906297
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The Invention relates to an apparatus for making X-ray images.
BACKGROUND OF THE INVENTION
In clinical diagnostics, the quality of X-ray images is a very important factor. Furthermore, archiving and further processing of the images in a hospital environment imposes many special demands on the apparatus by which the X-ray images are made. One factor which increases the usability of the apparatus its small size and light weight.
Conventional apparatus, for example used for X-ray pneumography, comprises a plate on which a visible image is formed due to X-rays incident on the plate, and the film placed on the plate is exposed. The plate and the film are disposed in a cassette which is removed after each exposure. An apparatus is also known in which a latent image is formed on a drum with a selenium surface. Imaging comprises charging the drum by rotating the drum, image formation, and scanning of it for storage again by rotating the drum. The apparatus contains moving parts and is heavy.
Conventional X-ray apparatus has a measuring chamber in front of the photographic plate which measures the X-ray intensity incident on the plate and sends out a message to an automatic exposure control unit in connection with the X-ray generator after a specific exposure is attained. In this way, one tries to achieve a correct exposure at each picture taking.
An apparatus is known from U.S. Pat. No. 5,187,730 for an X-ray diagnostic system and method of picking up X-ray picture. The image is formed by an image intensifier which converts the X-rays into fluorescent light. There is also an optical system having a lens means for converting the fluorescent light and a beam splatter means for splitting the fluorescent light into a plurality of optical paths. The beam splitter is a partly transparent mirror so that a part of the fluorescent light is led to a photodetector, such as a photodiode. In the diagnostic system according to the above U.S. patent, there is a risk that part of the X-rays penetrate the reflecting mirror and the X-rays may cause damage to the CCD. Only a part of the fluorescent light is reflected to the photosensor so the quantity-of-light controller may use incorrect values in controlling the X-ray generator.
An X-ray imaging system including brightness control is also known from European Patent Application 547679. In this application, the image from the X-ray image intensifier is conducted through prisms. Part of the beam is reflected to a photodiode for automatic dose control or exposure timing. Also, in this apparatus, there is the disadvantage that some X-rays may penetrate through the prisms to the CCD sensor which may be damaged. Another disadvantage is that the photosensitive sensor sees only part of the light beam from the image intensifier.
An apparatus is also known from the European patent 264218 for making an image of an object by X-rays in which the image formed on a phosphor screen by the X-rays is stored by means of a CCD camera after which the image can be processed digitally. Exposure time is controlled by a shutter and the CCD is operated in slow scan mode which involves cooling down to at least -40.degree. C. to decrease noise due to slow exposure of the picture and/or the read-out. Exposure times with this apparatus are generally minutes or even hours. The apparatus is adapted for X-ray inspection of objects, but it does not take into account needs of clinical X-raying.
SUMMARY OF THE INVENTION
The purpose of the invention is to obtain a new kind of apparatus for making X-ray images which is particularly suitable for X-raying patients in clinical examinations like for X-raying of lungs and bones. To accomplish this objective, the apparatus of this invention is provided with a photosensor which is separate from the CCD camera and is in optical communication with the image formed on the luminescent screen which sends out light of visible wavelength. The photosensor is positioned so that the illumination power of the luminescent screen falls on it practically withi
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Olesen Steen
Salmi Matti
Svensson Stig
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