Claims
- 1. A dosimeter for ionizing radiation comprising a casing defining a gas-filled measuring chamber in which there is provided electrode elements and wherein said casing is provided with at least one entry window for the ionizing radiation, characterized in that said casing is of an oblong shape defining an oblong measuring chamber, said casing including at least two opposed side walls of a material transparent to ionizing radiation, an inner surface of one side wall being provided with wire electrodes extending essentially longitudinally to said oblong measuring chamber and an inner surface of another side wall being provided with a plurality of strip-like electrode elements essentially transversely to said oblong measuring chamber.
- 2. The dosimeter according to claim 1 wherein said casing includes an oblong frame mounted in gas-tight relationship to said side walls.
- 3. The dosimeter according to claim 2 wherein said casing is manufactured from glass.
- 4. The dosimeter according to claim 2 wherein said casing is manufactured from acrylic.
- 5. The dosimeter according to claim 1 and further including a guard electrode surrounding said wire electrodes on said side wall.
- 6. The dosimeter according to claim 1 wherein said strip-like electrodes are formed by depositing a layer of conducting material in a required pattern by evaporation.
- 7. The dosimeter according to claim 1 wherein said strip-like electrodes are formed by depositing a layer of metal in a desired pattern by sputtering technique.
- 8. The dosimeter according to claim 6 or 7 wherein said strip=like electrodes are formed of nickel.
- 9. The dosimeter according to claim 1 wherein a strip of each side wall extends beyond said casing and said electrodes are provided with connecting sections.
- 10. The dosimeter according to claim 9 wherein each strip is constructed as a connecting connector.
- 11. The dosimeter according to claim 9 or 10 wherein a strip of each side wall defines a recess with said casing extending lengthwise along outermost edges of said frame diagonally opposite one another.
- 12. The dosimeter according to claim 1 wherein said casing includes a side wall having a hole for inserting a tube for evacuating said oblong measuring chamber and wherein said tube is sealed after introduction of gas into said oblong measuring chamber.
- 13. The dosimeter according to claim 1 wherein said oblong measuring chamber is filled with xenon.
- 14. The dosimeter according to claim 13 wherein potential difference between said wire electrodes and said strip-like electrode elements during operation prevent gas multiplication.
- 15. The dosimeter according to claim 1 wherein said strip-like electrode elements extend obliquely with respect to said transverse direction of said oblong measuring chamber.
- 16. An apparatus for slit radiography, which comprises:
- an X-ray source;
- an X-ray detector collecting radiation passing through a body to be radiographed;
- a slit diaphragm positioned between said X-ray source and said body for forming a planar X-ray beam;
- a plurality of attenuating elements positioned along said slit diaphragm forming a plurality of attenuating sections;
- means for scanning said body with said planar X-ray beam;
- a detection member disposed in a path of said planar X-ray beam to measure ionizing radiation comprised of an oblong-shaped casing defining a gas-filled chamber said casing having at least two side walls formed of a material transparent to ionizing radiation, one side wall having a plurality of strip-like electrodes extending transversely to a longitudinal direction of said oblong-shaped casing, another side wall having wire electrodes extending in said longitudinal direction, said electrode capable of being connected to a source of electromotive force, each of said strip-like electrodes generating a signal representative of intensity of ionizing radiation, a group of said strip-like electrodes corresponding to a respective attenuating element;
- means for moving said detection member in synchronization with said means for scanning said body with said planar X-ray beam; and
- means for simultaneously controlling each of said attenuating elements during scanning of said body in response to electric signals produced at respective groups of said strip-like electrodes.
- 17. The apparatus for slit radiography as defined in claim 16 wherein said casing includes an oblong frame mounted in a gas-tight manner between said side walls.
- 18. The apparatus for slit radiography as defined in claim 17 wherein said casing is manufactured from glass.
- 19. The apparatus for slit radiography as defined in claim 17 wherein said casing is manufactured from acrylic.
- 20. The apparatus for slit radiography as defined in claim 16 and further including a guard electrode surrounding said wire electrodes.
- 21. The apparatus for slit radiography as defined in claim 16 wherein said strip-like electrodes are formed by depositing a layer of conducting material in a required pattern by evaporation.
- 22. The apparatus for slit radiography as defined in claim 21 wherein said strip-like electrodes are formed of nickel.
- 23. The apparatus for slit radiography as defined in claim 16 wherein said strip-like electrodes are formed by depositing a layer of metal in a desired pattern by means of sputtering technique.
- 24. The apparatus for slit radiography as defined in claim 23 characterized in that said electrodes are formed of nickel. 32. The apparatus for slit radiography as defined in claim 16 wherein said detection member is mounted obliquely with respect to direction of scanning movement.
- 25. The apparatus for slit radiography as defined in claim 16 wherein a strip of each side wall extends beyond said casing and said electrodes are provided with connecting sections.
- 26. The apparatus for slit radiography as defined in claim 25 wherein each strip is constructed as a connecting connector.
- 27. The apparatus for slit radiography as defined in claim 25 or 26 wherein a strip of each side wall defines a recess with said casing extending essentially lengthwise of said frame along outermost edges of said frame diagonally opposite one another.
- 28. The apparatus for slit radiography as defined in claim 16 wherein said casing includes a side wall having a hole for inserting a tube for evacuating said measuring chamber and wherein said tube is sealed after introduction of gas into said measuring chamber.
- 29. The apparatus for slit radiography as defined in claim 16 wherein said measuring chamber is filled with xenon.
- 30. The apparatus for slit radiography as defined in claim 29 wherein said potential difference between said wire electrodes and said strip-like electrodes during operation prevent gas multiplication.
- 31. The apparatus for slit radiography as defined in claim 16 wherein said strip-like electrodes extend obliquely with respect to a transverse direction of said oblong measuring chamber.
- 32. The apparatus for slit radiography as defined in claim 16 wherein said detection member is mounted obliquely with respect to direction of scanning movement.
Priority Claims (1)
| Number |
Date |
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| 8503153 |
Nov 1985 |
NLX |
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BACKGROUND OF THE INVENTION
(1) Related Application
This is a continuation-in-part application of U.S. application Ser. No. 06/931,539, filed Nov. 14, 1986.
(2) Field of the Invention
This invention relates to a dosimeter for slit radiography, and more particularly to a dosimeter for slit radiography to control radiation intensity during scanning of a body.
(3) Brief Description of the Prior Art
A dosimeter for use in a slit radiography apparatus is described in European patent application No. 155064 and is comprised of a common electrode and a number of needle-like electrodes opposite the common electrode extending into the planar X-ray beam. The needle-like electrodes point in a direction parallel to the scanning direction and give rise to a visible X-ray shadow in the ultimate radiograph.
Dosimeters, as such, are known from the Handbook on Synchrotron Radiation, volume 1A, pages 323-328 by Ernst Eckhard Koch, published by North Holland Publishing Company, Amsterdam, N.Y., Oxford, 1983. A problem with such dosimeters, as described therein, is that application thereof is not readily usable in slit radiography equipment, where it is necessary to measure and regulate the quantity of radiation per diaphragm section transmitted through the diaphragm slit at any instance during the production of a radiograph without giving rise to a visible X-ray shadow image of the dosimeter itself in the radiograph.
In Nuclear Instruments and Methods 133 (1976) 409-413, there is described a pulse counter showing some similarities to a dosimeter in that an oblong gas filled chamber is enclosed by side walls having electrodes thereon. The pulse counter described is designed to count the number of heavy ion particles that enter or pass through the counter. As is usual in pulse counters, measures have been taken to create a continuous gas flow through the gas filled chamber. The pulse counter described is designed to have good temporal and hardly any spatial resolution for heavy ion particles. If and how it could function in detecting single X-ray photons let alone X-ray dosage is not described in the article.
Pulse counters like the one described are unfit to be used as dosimeters for X-rays because ionization chamber dosimeters measure current resulting from a number of photons is so great that a pulse counter would be totally overloaded. Current in a dosimeter is proportional to intensity of radiation whereas in a pulse counter current during pulses has no relation to intensity of radiation. Pulse counters, as the one described in the Nuclear Instruments article, are also less fit for use in a slit radiography apparatus because of the additional equipment needed to maintain gas flow.
In the abstract JP-A-57lO477 of Patent Abstracts of Japan 6 (1982) no.7, (P-143) 948, there is described a square X-ray dosimeter comprised of one large area dosimeter covering the whole area of the device as well as within the same housing back to back with the large area dosimeter there is provided a small area dosimeter covering a fraction of the area of the device. Such dosimeter does not have any spatial resolution and thus, is unfit to be used in slit radiography apparatus.
An object of the present invention is to provide an improved method and apparatus for slit radiography including an improved dosimeter.
Another object of the present invention is to provide an improved method and apparatus for slit radiography including an improved dosimeter for effecting the production of improved radiographs.
These and other objects of the present invention are achieved by a dosimeter to be used in connection with slit radiography and comprised of a gas filled chamber with one side wall provided with a plurality of X-ray transparent strip-like electrodes extending substantially transversely to a longitudinal direction of the oblong-shaped casing and another side wall provided with wire electrodes extending parallel to such longitudinal direction of the oblong-shaped casing wherein each of the strip-like electrodes generates a signal representative of intensity of ionizing radiation and wherein the strip-like electrodes are divided into a number of groups, signals from the strip-like electrodes belonging to each group are combined to provide a control signal for a respective attenuation element.
US Referenced Citations (6)
Continuation in Parts (1)
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Number |
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931539 |
Nov 1986 |
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Patent Grant
4956557
