EP1446810B1 - Method and device for the recording of objects - Google Patents

Abstract

A process for taking a picture of an object (4) involves using a radiation source (2) and a recording medium e.g. a film. The object is illuminated and pictures are continuously taken by moving the object and the source relative to a screen. The screen opening (9) is dependent on the size of the object and is adjusted before or during each exposure. The source is e.g. an X-ray source.

Description

Technical area

The invention relates to a method according to the preamble of claim 1 and to a device according to the preamble of claim 9.

State of the art

In photographic technology, moving shutters (shutter, shutter) for metering the amount of light are known, e.g. the width of the aperture for varying the amount of light can be set differently.

In radiology, diaphragms are known as collimators, which serve with constant dimensions to reduce the radiation dose produced but also according to US-A-4,773,087 be used to reduce the scattered radiation. Collimators may also be adjustable to limit the irradiated area adapted to the object to be photographed. So in the US-A-4,122,350 a size-adjustable collimator for limiting the irradiated area in mammography is shown, wherein no relative movement between the object and the X-ray source takes place. Out U.S.-A-4,603,427 An adjustable collimator is known that can limit the height of the irradiated area in cephalometric panoramic exposures. The width of the intersection of the cone and the plane of rotation is determined by a non-adjustable slot at the exit of the X-ray source. Perpendicular to the pivot plane, the cone of rays is limited by the height-adjustable collimator, with display bars indicating the limit in height. Out US-A-3,518,435 An adjustable collimator is known which limits the irradiated area depending on the size of the film cassette used. In the recording mode shown, there is no relative movement between the object and the X-ray source. As a general rule In radiology, it is known to use collimators to confine the irradiated area and to represent the limited area for the control of the same on the object (patient) before the actual recording by means of visible light. Collimators are also used to confine the X-ray radiation when using line detectors, such that only the radiation-sensitive line detector is irradiated. Also, in classical photographic radiology, raster screens are used to reduce stray radiation. However, this method of reducing the stray radiation also simultaneously weakens the useful radiation, so that high doses of X-radiation must be used to produce a high-contrast image. These ray patterns, which are located between the object and the image, are constant in their dimensions. The recording of unwanted scattered radiation on the recording medium generally leads to a deteriorated useful signal / interference signal ratio during image acquisition and thus to a non-optimal image quality. Out EP-A-0 223 432 For the purpose of equalizing the exposure of X-ray images, it is known to control a multiplicity of diaphragms by the patient body as a function of the attenuation of the X-radiation, with a plurality of detectors being arranged behind the patient for detecting the X-radiation intensity. Out US-A-5,627,869 It is known to set the collimator in mammographic individual recordings so that the size of the X-ray cone is matched to the size of the breast compression disc and its distance from the X-ray source so that the X-ray cone covers the breast compression disc but does not extend beyond its edges. This is to reduce the scattered radiation.

Presentation of the invention

It is an object of the present invention to improve the image quality.

In a method of the type mentioned, this is achieved by the characterizing features of claim 1. In a device of the type mentioned by the characterizing features of claim 9.

The fact that a screen with object size-dependent aperture is used, the scattered radiation can be particularly well reduced, which increases the image quality. It has been shown in X-ray photography that the object size-dependent aperture leads to sharper images, which allow a better interpretation of the image of the object.

Brief description of the drawings

• Figur 1 eine schematische Ansicht des erfindungsgemässen Vorgehens bzw. einer Vorrichtung zum Durchleuchten eines Gegenstandes;
• Figur 2 schematisch eine Draufsicht auf die Blende von Figur 1;
• Figur 3 eine Schnittansicht entlang der Linie A-A von Figur 2 sowie eine Variante der Blende;
• Figur 4 eine schematische Ansicht einer Abwandlung des Vorgehens bzw. der Vorrichtung von Figur 1;
• Figur 5 eine weitere Ausführungsform;
• Figur 6 eine weitere Ausführungsform der Vorrichtung; und
• Figur 7 eine Ausführungsform mit zwei Blenden.

Embodiments of the invention are explained in more detail below with reference to the description and the drawings. It shows

• FIG. 1 a schematic view of the inventive approach or a device for scanning an object;
• FIG. 2 schematically a plan view of the diaphragm of FIG. 1 ;
• FIG. 3 a sectional view taken along the line AA of FIG. 2 as well as a variant of the aperture;
• FIG. 4 a schematic view of a modification of the procedure or the device of FIG. 1 ;
• FIG. 5 another embodiment;
• FIG. 6 a further embodiment of the device; and
• FIG. 7 an embodiment with two panels.

Best way to carry out the invention

Scattering, which always occurs, for example, when imaging objects by light rays or X-rays, reduces the contrast on the image as it reduces the desired optimum contour sharpness of the object. Scattered radiation is formed when imaging objects through object-related reflections or through ionizing radiation that penetrates the object. Resulting blurred contours are the cause of a poorer contrast of the image of the object and can lead to indecipherable conclusions in the evaluation of the image, since the lack of explanatory power of the image a secure statement about the object is impossible. FIG. 1 shows a first embodiment in plan, in which by means of an object-dependent adjusted aperture, the scattered radiation is reduced. Set object-dependent means that the object size, actually the object volume, but in a simplified manner only the surface of the object facing the radiation, or even only one dimension of this surface, is taken into account, around the diaphragm, which allows only a portion of the radiation to pass , which is sent by the source in the direction of the object (with or without collimator) proportional to this object size. The FIG. 1 shows schematically a device 1, by means of which an object 4 is transilluminated in order to produce on a receiving means 3 an image of the object 4. In this case, the device 1 is, for example, an industrial or medical X-ray system, which illuminates a technical object 4, or a patient, and generates the image on an X-ray film or an X-ray plate 3. Accordingly, the X-ray source 2 is an X-ray tube. For the object, a per se known, only with two lines laterally of the object indicated slide 4 'is provided. The X-ray source 2, which is arranged in a schematically illustrated housing, generates X-rays, their cones or otherwise differently shaped outline with the boundary lines 5 in the Figure is indicated. The x-ray source 2 is located, for example, in a housing 10, which is closed by the aperture 6 to the object 4 out. The panel can also be arranged separately, housing independent. The diaphragm 6 has an opening 9, through which a part of the X-rays can escape through the aperture from the housing 10, while the rest of the X-rays is prevented by the diaphragm 6 from exiting the housing. In the example shown, the object is placed so that it can be detected by the entire cone of rays, as it exits from the source 2 and is indicated by the lines 5. The radiation emerging from the source 2 can be limited in a known manner by an only indicated collimator 2 '; In this case, the lines 5 represent the already limited radiation, which may also extend only over a part of the object 4, if only this part is to be imaged or only this part is moved relative to the beam. In the arrangement of Figure 1 it is assumed that the housing 10 with the source 2 and the diaphragm 6 is stationary, while the object 4 and the receiving means 3 in the direction of arrow A between the diaphragm 6 and the receiving means 3 is moved past. In this case, the opening 9 of the aperture 6 shown in section is set in any case in the aperture dimension, which corresponds to the direction of movement, as a function of the size of the object 4. In the present case, the width b of the aperture 9 is set, which is in the direction of movement (arrow A). This is in the FIG. 1 schematically represented by two sensors 8, which measure the object 4, for example, contactless by an ultrasonic measurement or an optical measurement. Sensors may also be provided which contact the object to accommodate its dimension for the aperture setting. This measurement is preferably carried out before the image acquisition in a separate step. According to the measured values, the size of the Aperture 9 determined and adjusted for example by servomotors 7, which are operated by the controller 11. One in the recording situation of FIG. 1 dimension of interest is the width B of the object, which is traversed by the relative movement in the direction of an arrow A. Corresponding to this width B, the width b of the slot-shaped aperture opening of the diaphragm 6 is set in the present example. The width b of the aperture is x times smaller than the width B of the object, where x is in the range of 10 to 100,000, so that the slot width is thus 10 times to 100,000 times less than the width B of the object. In the case of a beam which has already been limited by collimation or otherwise placed, in which only a part is imaged, the diaphragm aperture can also be chosen to be proportional to the width B of the part of the object. Further, preferably, the height of the slot opening of the aperture 6 corresponding to the height of the object 4, that is, the extension perpendicular to the plane of the object 4, set. For this example, the same divider can be used as in the width setting, so that the slot height is also 10 times smaller to 100,000 times smaller than the height of the object 4. The object 4 is then imaged accordingly by a limited by the object size dependent aperture X-ray, in which case the object and the imaging means or the X-ray plate 3 are moved together several times along the stationary and dimmed X-ray source 2, in each case correspondingly displaced in height, so that the image is produced strip by strip. As I said, it has been shown that a particularly good reduction of the scattered radiation and thus an increase in the image quality can be achieved by the appropriate object-size-proportional adjustment of the diaphragm 6.

FIG. 2 schematically shows a view of the diaphragm 6, wherein this according to FIG. 1 a slit with the slot 9 is. This slot 9 can be adjusted in height h and its width b by means of movable diaphragm elements 12 and 13, which are displaceable relative to one another. This is done by the in FIG. 1 indicated actuating means, which may be motor, pneumatic or hydraulic actuating means. Figure 3 shows a corresponding sectional view through the aperture 6 of FIG. 2 , wherein like elements are provided with the same reference numerals. The diaphragm can also be set differently in its depth t, for which purpose preferably also the depth T of the object is measured. A depth adjustment can take place in that several of the apertures are connected in series, as in FIG. 3 with a further aperture 6 'is merely indicated.

The use according to the invention of the diaphragm for reducing the stray radiation is possible for the entire spectrum of electromagnetic radiation. The smaller the object to be imaged, the smaller the aperture should be, whereby the ratio of proportions (aperture to object) can be from 1:10 to 1: 100,000. In order to achieve the best possible scattered radiation reduction, the highest possible proportionality, e.g. between 1: 10,000 to 1: 100,000. In this case, e.g. the width of the aperture of the aperture to the micrometer range desirable. Especially for very small objects, e.g. smaller than 1 mm, the optimum ratio diaphragm: object can only be realized technically complex, e.g. just for apertures in the range of 10 to 100 microns. In this case, a lower proportionality is decreased, e.g. 1:10 or 1:50.

FIG. 4 shows a further embodiment of the invention, wherein like reference numerals as used in the previous figures denote like elements. In this embodiment, the aperture also shown cut is between the object 4 and the receiving means 3 arranged. Again, the object 4 and the imaging means 3 are moved past the stationary diaphragm 6 and the stationary X-ray source according to the arrows A. Corresponding to the height h of the slot and the multiple greater height of the object 4, this passing movement takes place several times with different shifted height positions of diaphragm and object. To simplify the figure, the means 7, 8 and 11 are no longer shown, but are also present in the device. In any case, according to the invention, the dimension of the diaphragm is also set here, which corresponds to the relative movement, in the present case again the width b proportional to the width of the object 4. The beam 5 exits from the source 2, possibly through a collimator.

FIG. 5 shows a further embodiment in which in turn the same elements are provided with the same reference numerals and the means 7, 8 and 11 are not shown, but the X-ray source 2 and the diaphragm 6 according to the arrow A on the fixed object and the stationary imaging means 3 are moved past , Again, the image on the imaging means 3 line by line corresponding to the height of the slot of the diaphragm 6 can be generated. FIG. 6 shows a corresponding embodiment, wherein, however, the diaphragm between the object 4 and the imaging means 3 is arranged. Also the aperture of the Figures 5 and 6 are each set in their slot width b according to the direction of the process of the diaphragm.

FIG. 7 shows a further embodiment in which two apertures 6 and 16 are provided with the openings 9 and 19, wherein the one aperture between the X-ray source and the object and the other diaphragm between the object and the imaging means 3 is provided. The apertures are moved synchronously with the X-ray source 2 in order to scan the object line by line. The aperture 9 is doing again in the width b set object-dependent, preferably this also takes place at the aperture 19th

A preferred application of the invention is in the medical X-ray technology and in the industrial X-ray technology for testing materials.

The following are examples of X-rays with the object-dependent adjustable aperture.

Examples 1. As an example of a structure according to FIG. 1:

The tripod is a commercially available multistat with film cassettes or storage foils. On the tripod a panel with control is installed later. The reduction of the scattered radiation can be calculated as a first approximation as a proportion, which results from the total irradiated area without aperture to the passage area of the aperture.

Calculation example I

Irradiated area without aperture: 350 mm x 430 mm = 150 500 mm2 Passage area of the aperture: 350 mm x 1 mm = 350 mm2 Ratio to the aperture: 430: 1 or 0.2325%

Without aperture, 100% scattered radiation is produced; With Aperture a reduction of the scattered radiation by 100% -0.2325% = 99.7675% can be achieved.

Calculation Example II

Passage area of the aperture: 175 mm x 0.01 mm = 1.75 mm2 Ratio area of the aperture: 86,000: 1 or 0,001163%

With this aperture, the scattered radiation is reduced by 100% -0.001163% = 99.9987%.

2. Number of passes and time required:

The number of passes is usually 1.

The time required for the linear movement in direction A depends on the size of the object and is practicable between 0.1 and 10 seconds.

Claims (13)

1. Method for the recording of an object (4) by imaging by means of an X-ray radiation source (2) onto a recording means (3), particularly a film, wherein the object is roentgenised and is recorded continuously or discontinuously section by section during the recording, by means of at least one aperture (6) and a relative movement of the object on the one hand and aperture and recording means and optionally X-ray radiation source on the other hand, wherein the size of the aperture opening (9, 19) is adjusted depending on the object size in at least the dimension of the aperture opening lying in the direction of the relative movement, characterized in that the object volume or the surface of the object facing the X-ray radiation or only a dimension of this surface is taken into account as object size, and in that the object size is detected by means of a detection installation having mechanical and/or optical sensors or ultrasonic sensors (8) for the detection of the object volume or of at least one object dimension, wherein the aperture opening (9, 19) is particularly adjusted before or during each recording.
2. Method according to claim 1, characterized in that the X-rays (5) are limited in front of the aperture by means of at least one collimator (2').
3. Method according to one of the claims 1 or 2, characterized in that the object (4) and the recording means (3) are passed by the stationary X-ray radiation source (2) and the stationary aperture (6), wherein the aperture (6) is arranged between the X-ray radiation source (2) and the object (4) or wherein the aperture (6) is arranged between the object (4) and the recording means.
4. Method according to one of the claims 1 or 2, characterized in that the X-ray radiation source (2) and the aperture (6) are passed by the stationary object (4) and the stationary recording means (3), wherein the aperture (6) is arranged between the X-ray radiation source (2) and the object (4) or wherein the aperture (6) is arranged between the object (4) and the recording means (3), or wherein a first aperture (6) is arranged between the radiation source (3) and the object (4) and a second aperture (16) between the object (4) and the recoding means (3).
5. Method according to one of the claims 1 to 4, characterized in that the relative movement occurs in the direction of the width B of the object and the width b of the aperture opening is adjusted depending on the object size and optionally the height h of the aperture opening is additionally adjusted.
6. Method according to one of the claims 1 to 4, characterized in that the relative movement occurs in the direction of the height of the object and the height h of the aperture opening is adjusted depending on the object height.
7. Method according to one of the claims 5 or 6, characterized in that the thickness t of the aperture is additionally adjusted, particularly depending on the object thickness T.
8. Method according to one of the claims 1 to 7, characterized in that the aperture opening dimension is adjusted in a range of 1:10 to 1:100000 with respect to the object dimension, preferably in a range of 1:100 to 1:100000, further preferred in a range of 1:1000 to 1:100000 and further preferred in a range of 1:10000 to 1:100000.
9. Device for the recording of an object onto recording means (3) by means of an X-ray radiation source (2), wherein the device comprises at least an aperture (6) and movement means for the relative movement between the aperture (6) and the object (4), and wherein an adjustment installation (7, 11) is provided for the adjustment of at least one aperture opening dimension and a detection installation (8, 11) is provided for detecting at least one object dimension and wherein the adjustment installation is connected to the detection installation in such a way that at least an aperture opening dimension is adjustable depending on the at least one detected object dimension, wherein the at least one adjustable aperture opening dimension is adjustable in the direction of the relative movement, characterized in that the object volume or the surface of the object facing the X-ray radiation or only a dimension of this surface can be taken into account as object size, and in that the detection installation has mechanical and/or optical sensors or ultrasonic sensors (8) for the detection of the object volume or of at least one object dimension.
10. Device according to claim 9, characterized in that it comprises an X-ray radiation source (2), the ray of which is limited by means of at least one collimator (2').
11. Device according to claim 9 or 10, characterized in that it comprises an object carrier (4') and in that the object carrier on the one hand and the aperture (6) on the other hand are movable relatively to each other by means of the movement means (7, 11).
12. Device according to claim 11, characterized in that the X-ray radiation source (2) and the aperture (6) are secured to the device, and in that for this, the object carrier (4') and the recording means (3) are movably arranged for the performance of the relative movement, wherein the aperture (6) is arranged between the X-ray radiation source (2) and the object carrier (4'), or wherein the aperture (6) is arranged between the object carrier and the recording means (3).
13. Device according to claim 11, characterized in that the object carrier and the recording means (3) are secured to the device and in that for this, the X-ray radiation source (2) and the aperture (6) are movably arranged for the performance of the relative movement, wherein the aperture (6) is arranged between the X-ray radiation source (2) and the object carrier or wherein the aperture (6) is arranged between the object carrier and the recording means (3) or wherein a first aperture (6) is arranged between the X-ray radiation source (2) and the object carrier and a second aperture (16) which is motion-coupled with the first aperture is arranged between the object carrier and the recording means.

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