CA2009693A1

CA2009693A1 - Primary collimator for x-ray apparatus

Info

Publication number: CA2009693A1
Application number: CA 2009693
Authority: CA
Inventors: Juhani Palonen
Original assignee: Instrumentarium Oyj
Current assignee: Instrumentarium Oyj
Priority date: 1989-09-14
Filing date: 1990-02-09
Publication date: 1991-03-14
Also published as: FI894338A0; FI894338A7; JPH03107799A

Abstract

Abstract The invention relates to a primary collimator for an X-ray apparatus, comprising at least two plate-like shutters (6) and means for moving/
controlling them. A collimator of the invention includes a control disc (3) provided with a guideway (4). The guideway (4) is used for moving through the intermediary of dowels (5) carried by said shutters, any given position of shutters (6) being determined by the angular position of disc (3). The collimator further includes a motor (1) which through a pinion (2) drives disc (3) provided with a toothed outer rim.

Description

zoo~r,s3 Primary collimator for X-ray apparatus The present invention relates to a collimator for delimit-ing the primary cone of rays of an X-ray apparatus.

An object of the invention is to provide a collimator which is readily operable and has combined possibilities of using a single collimator for delimiting a cone of rays as required by a plurality of image sizes and/or imaging methods.

The most common way of collimating a cone of rays is to replace elements fixed to the body section of a colli-mator by means of certain fasteners or guides, each of such elements being provided with an aperture required by a single image size or imaging method. However, this procedure is generally considered troublesome; partly due to the great number of elements but partly also be-cause they are inconvenient to handle and difficult to store.
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In order to achieve the above object, a collimator of the invention is characterized in that the collimator carries a control disc provided with a guideway, said ~-guideway being used for displacing the shutters through the intermediary of dowels carried by the shutters, any given position of the shutters being determined by the angular position of the disc.
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In a preferred embodiment of the invention there is em-ployed four shutters movable independently of each other.

The offers an advantageous possibility of using a single collimator for imaging e.g. narrow-cone tomography and lateral projections of various sizes by moving the shut-' zno~s3 ter plates relative to each other for forming primaryapertures of a plurality of different sizes and shapes.

The invention will now be described with reference made to the accompanying drawings, in which:

fig. 1 shows one embodiment of a collimator of the in-vention with a control disc removed, and fig. 2 shows one embodiment of a control disc for a col-limator of the invention.

As shown in figs. 1 and 2, the collimator comprises a body 10 provided with guideways 9 for shutter plates 6.
Each shutter plate 6 is fitted with a control dowel 5 as well as with a return means 11, preferably a coil spring. The return spring 11 is preferably fitted in -a groove 8 cut in the bottom of guideway 9. The colli-mator further includes a control disc 3 shown in fig. 2 and provided with an internal guideway 4. For driving a disc 3 its rim is preferably toothed for facilitating the rotation of diisc 3 by means of a motor 1 through the intermediary of a pinion 2. When assembling the collimator, a control disc 3 is placed in a recess 12 formed in body 10 on top of shutter plates 6 in a man- -ner that the control dowels 5 are set against guideway 4 by virtue of an attraction applied to shutters 6 by return springs 11. When driving said control disc 3, the shutters 6 reciprocate in a forced manner in their quideways 9 under the control of guideway 4. Thus, the position of each shutter depends on the anugular posi-tion of disc 3. Hence, according to the invention, an aperture 7 of a desired size and/or shape can be formed in a relatively simple manner between shutter plates 6 by rotating said disc 3.

3 Z(~0~,93 The above embodiment is only described as an example of one preferred way of carrying out the invention and is I by no means intended to limit the scope of protection i defined by the annexed claims. In certain cases, for example, the number of shutters 6 may be just two where-by, for example, the length of a formed gap remmains con-stant as the gap width changes as a function of the move-ment of the shutters.

Claims

1. A primary collimator for an X-ray apparatus, com-prising at least two plate-like shutters (6) and means for moving/controlling them, c h a r a c t e r i z e d in that the collimator includes a control disc (3) which is provided with a guideway (4), said guideway (4) be-ing used for moving shutters (6) through the intermediary of dowels (5) carried by shutters (6), any given posi-tion of shutters (6) being determined by the angular po-sition of disc (3).

2. A collimator as set forth in claim 1, c h a r a c -t e r i z e d by including at least four shutters (6) movable independently of each other.

3. A collimator as set forth in claim 1 or 2, c h a r -a c t e r i z e d in that the collimator includes a motor (1) which through a pinion (2) drives said disc (3) whose outer rim is toothed.

4. A collimator as set forth in any of claims 1 - 3, c h a r a c t e r i z e d in that each shutter (6) is positively driven in a guideway (9), each shutter (6) being fitted with means for holding dowel (5) against guideway (4).

5. A collimator as set forth in claim 4, c h a r a c -t e r i z e d in that said means comprises a return spring (11) which is fixed by one of its ends to a col-limator body (10) and by its other end to shutter (6).

6. A collimator as set forth in claim 5, c h a r a c -t e r i z e d in that said return spring (11) is fitted in a groove (8) cut in the bottom of guideway (9).