X-ray or gamma ray systems or devices – Beam control – Filter
Patent
1989-11-01
1991-10-29
Westin, Edward P.
X-ray or gamma ray systems or devices
Beam control
Filter
378 97, 378116, 378 7, 378154, G21K 300
Patent
active
050621297
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for slit radiography with image equalization, comprising an X-ray source which can scan a body for examination via a slit of a slit diaphragm with a flat, fan-shaped X-ray beam over a scanning path in a direction transverse to the lengthwise direction of the slit for forming an X-ray shadowgraph on an X-ray detector; an absorption device which under the control of control signals can influence the fan-shaped X-ray beam per sector thereof, in order to permit control of the X-ray radiation falling in each sector on the body to be examined; and detection means which are designed to detect the quantity of X-ray radiation transmitted by the body instantaneously per sector during a scanning movement of the X-ray beam and to convert it into corresponding signals.
Such a device is known, for example from Dutch Patent Application 8400845, which has been laid open for inspection. The known device can have as the X-ray detector an oblong X-ray image intensifier tube which carries out a scanning movement synchronized with the X-ray beam or, for example, a large stationary X-ray screen which is scanned in strips by the flat fan-shaped X-ray beam to form a complete X-ray shadow image of (part of) the body to be examined. In the case of a device intended for making thorax photographs such a large X-ray screen has, for example, dimensions of 40 cm.times.40 cm.
According to the older Dutch Patent Application 8503152 and the older Dutch Patent Application 8503153, an elongated dosimeter for ionizing radiation can be used for the detection of the quantity of radiation transmitted by the body to be examined instantaneously and per sector. For this purpose, the known dosimeters also carry out a scanning movement in synchronization with the scanning movement of the X-ray beam in such a way that at any instant in the scanning movement the X-ray radiation transmitted by the body for examination also passes through the dosimeter.
For this purpose, special means are needed to ensure that the dosimeter can make a scanning movement along the desired path, and to ensure that the scanning movement of the dosimeter does in fact take place in synchronization with the X-ray beam.
According to Dutch Patent Applications 8503152 and 8503153, it is possible to use for this purpose an arm which carries the X-ray source, the slit diaphragm and the absorption device, and which can swivel about the X-ray focus of the X-ray source. The end of the arm facing away from the X-ray source is then connected to the dosimeter.
An object of the invention is to provide a device for slit radiography in which no special means are needed to make a dosimeter or other detection means physically carry out a scanning movement.
Another object of the invention is to limit the number of moving parts of a device for slit radiography with image equalization.
According to the invention, a device of the above-described type is to this end characterized in that the detection means comprise a two-dimensional dosimeter for ionizing radiation, which is placed beyond the body to be examined, is of a width corresponding to the width of the flat, fan-shaped X-ray beam at that point and a height corresponding to the total scanning distance, and which has at least one system of essentially parallel electrodes extending in the direction of scanning and connected to a control device for forming control signals for the absorption device, and has at least one counter electrode.
The invention will be explained in greater detail below with reference to the appended drawing showing a number of examples of embodiments.
FIG. 1 shows schematically an example of a device according to the invention;
FIG. 2 shows schematically in front view a dosimeter for a device according to the invention;
FIG. 3 shows a cross section of a dosimeter according to FIG. 2;
FIG. 4 shows a modification of FIG. 3;
FIGS. 5 and 6 show cross sections of a different dosimeter for a device according to the invention;
FIG. 7 shows yet another embodiment of a dosimeter for a device acc
REFERENCES:
patent: 4260894 (1981-04-01), Neumann
patent: 4859855 (1989-08-01), Vlasbloem
patent: 4864594 (1989-09-01), Inbar et al.
patent: 4866744 (1989-09-01), Yoshida
B.V. Optische Industrie "De Oude Delft"
Marn Louis E.
Westin Edward P.
Wong Don
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