X-ray or gamma ray systems or devices – Beam control – Scanner
Patent
1990-02-23
1991-10-15
Westin, Edward P.
X-ray or gamma ray systems or devices
Beam control
Scanner
378145, 378147, 378148, 378152, G21K 102, G21K 104
Patent
active
050581490
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an equipment for slit radiography comprising an X-ray source which can scan a body under examination with a fan-shaped X-ray beam via a slit of a slit-type diaphragm to form an X-ray shadow image; an X-ray detector for receiving the X-ray radiation transmitted through the body; detection means which are equipped to deliver continuously, per sector of the fan-shaped X-ray beam, a signal which is a measure of the quantity of X-ray radiation instantaneously transmitted in the respective sector through the body under examination; control means which form control signals on the basis of the signals from the detection means: and an attenuation device which operates in conjunction with the slit-type diaphragm and which regulates the quantity of X-ray radiation transmitted under the control of the control signals per sector of the fan-shaped X-ray beam.
Such an equipment is known from Dutch Patent Application 8400845. Dutch Patent Application 8400845 describes various exemplary embodiments of suitable attentuation devices which all comprise a number of attenuation elements which cover sharply defined regions, situated next to each other, of the slit diaphragm and which are each able to move, essentially independently of the adjacent attenuation elements, transversely to the longitudinal direction of the slit of the slit diaphragm under the influence of suitable control signals, and extend to a greater or lesser degree into the fan-shaped X-ray beam in the process.
In practice it has emerged that, in certain circumstances which depend essentially on the nature of the body under examination, strip-like artefacts may occur in the X-ray shadow image to be formed.
The object of the invention is to prevent the occurence of such strip artefacts in X-ray shadow images produced with the aid of an equipment for slit radiography of the type described above.
For this purpose, such an equipment for slit radiogaphy is characterized, according to the invention, in that the attenuation device comprises an elastic strip of X-ray radiation-absorbing material, which strip extends, in the rest position essentially parallel to the slit of the slit diaphragm and, during operation, can be brought to an undulated state by controllable drive members.
The invention will be described in more detail below with reference to the accompanying drawing.
FIG. 1 shows diagrammatically an equipment for slit radiography;
FIG. 2 shows diagrammatically a front view of the slit diaphragm;
FIGS. 3, 4 and 5 illustrate diagrammatically a first exemplary embodiment of an attenuation device according to the invention in side, plan and front view;
FIG. 6 shows diagrammatically a modification of the device of FIGS. 3 to 5 inclusive;
FIG. 7 illustrates another elaboration of the invention idea; and
FIGS. 8 to 10 inclusive illustrate another elaboration of the inventive idea and two variants thereof.
FIG. 1 shows diagrammatically an example of an equipment for slit radiography comprising an X-ray source 1, a slit diaphragm 2 placed in front of the X-ray source, and an X-ray screen 3. The slit diaphragm 2 transmits a fan-shaped X-ray beam 4 with a relatively small thickness. In operation, the X-ray source and/or the slit diaphragm are moved in a manner such that the X-ray beam 4 scans the X-ray detector 3. For this purpose, for example, the X-ray source may be swivelled together with the slit diaphragm about an axis extending transversely to the plane of the drawing through the X-ray focus f, as indicated by an arrow 5. If a body 6 to be irradiated is situated between the X-ray source and the X-ray detector, a radiograph can be made in this manner of (a part of) the body 6. Attention is drawn to the fact that, instead of a stationary X-ray detector, a strip-type X-ray detector can be used in the manner as described in Dutch Patent Application 8303156.
In order to be able to influence the quantity of X-ray radiation transmitted through the slit diaphragm per sector of the fan-shaped X-ray beam to make an equalized radiograph, a controllabl
REFERENCES:
patent: 4675893 (1987-06-01), Duinker et al.
patent: 4715056 (1987-12-01), Vlasbloem et al.
patent: 4890312 (1989-12-01), Duinker
B.V. Optische Industrie "De Oude Delft"
Marn Louis E.
Westin Edward P.
Wong Don
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