CA1154547A - Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap - Google Patents
Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlapInfo
- Publication number
- CA1154547A CA1154547A CA000362569A CA362569A CA1154547A CA 1154547 A CA1154547 A CA 1154547A CA 000362569 A CA000362569 A CA 000362569A CA 362569 A CA362569 A CA 362569A CA 1154547 A CA1154547 A CA 1154547A
- Authority
- CA
- Canada
- Prior art keywords
- diaphragm
- images
- layer
- beams
- recording
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Analysing Materials By The Use Of Radiation (AREA)
Abstract
ABSTRACT:
"Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap."
The invention relates to a device for producing images of a layer of a three-dimensional object, with radiation sources arranged in a radiation source plane, for irradiating the object with beams of rays from differ-ent directions, and with several planar recording layers, arranged parallel to one another, of recording all said shadow images, wherein before each recording layer there is arranged a diaphragm arrangement that has been allo-cated to it for (stepwise) masking of the beams of rays, and wherein the diaphragm apertures of each diaphragm arrangement are so much the smaller, the greater the distance the diaphragm arrangement is from the radiation sources.
"Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap."
The invention relates to a device for producing images of a layer of a three-dimensional object, with radiation sources arranged in a radiation source plane, for irradiating the object with beams of rays from differ-ent directions, and with several planar recording layers, arranged parallel to one another, of recording all said shadow images, wherein before each recording layer there is arranged a diaphragm arrangement that has been allo-cated to it for (stepwise) masking of the beams of rays, and wherein the diaphragm apertures of each diaphragm arrangement are so much the smaller, the greater the distance the diaphragm arrangement is from the radiation sources.
Description
~5~S47 The invention relates to a device for producing ` images of a layer of a three-dimensional object, with radi-; ation sources arranged in a radiation source plane, for irradiating the object with beams of penetrating rays from S different directions, and with several planar recording layers, arranged parallel to one another, for the purpose of recording all shadow images thereby generated.
In the German Patent application DE-OS 25 14 988 by U. Tiemens and which was published on October 10, 1976, 10 there has already been shown, using a multiple radiation source containing X-ray tubes, how to record coded images on several successive films, the coded images consisting in each case of shadow images superimposed on one another to more or lesser degrees. From these coded images it is pos-15 sible, in a later step, to reconstruct images of layers ofthe ob~ect (see German patent applications DE-OS 27 19 386 and 27 46 035 by H. Weiss et al which were published on April 5, 1979 and April 19, 1979, respectively).
The images of layers of an object (DE-OS 2514 988) 20 are obtained in principle from shadow images, but the latter are not present in an isolated but in an overlapped form, then because of this overlap additional artefacts are trans-ferred into the reccnstructed image in the process of layer representation and thus impair the picture quality. The 25 influence of the artefacts becomes greater with increasing degree of overlap. The artefacts can in fact be removed;
but the method requires multichannel decoding devices for decoding the overlapping shadow images recorded in each of the respective planes. By means of separate shadow images 30 in each recording plane, however, i~ is possible to avoid the above artefacts and thus considerably improve the image quality. In the case of separate images, however, the object size is severely limited unless film formats that are too big are used. Using a beam geometry that is tech-35 nically feasible (approximately 25 tubes, focus-object ~.
~54S~7 Pl~ 79 119 2 1~-9-198() distance FOD = 1200 mm (object-film distance OFA = 500 mm)) and a commercial film format of 40 x 40 cm2 it is only possible therefore to record objec-ts with a diameter of approxima-tely 50 mm, separately. In objects of this size, however, it is very difficult for the doctor to make an accurate diagnosis because, with this size, orientation towards adjacent, known and larger object details (for example vessels filled with contrast medium), which can be an important aid to a doctor making his diagnosis, is usu-lO ally impossible because this information is not present inthe images or lies at an unfavourable spot, for example at the edge of the image. I-t is desirable, therefore~ that an image first be prepared of a relatively large object area, which will enable the doctor to orientate himself. An 15 additional exposure, however, means a greater radiation load on the patient. The patient has also to be subjected to more contrast medium if this is being used for exposure purposes. The longer examination period -that results is also, of course, a disadvantage for both patient and doctor.
It is the objec-t of the present invention, there-fore, to create a device for producing images of a layer of an object whereby it is possible to prepare both shadow images of large objec-t areas in the case of relatively marked overlap of the shadow images and simultaneously 25 shadow images, which hardly or not overlap, which repre-sent only a part of said large object area. According to the invention the device is charac-terized in that in fron-t of each recording layer is placed a diaphragm arrangement allocated to it for masking of the beams of rays, -the 30 diaphragm apertures o~ each diaphragm arrangement being so much the smaller the greater the distance between the diaphragm arrangement and the radiation sources.
In this way, the shadow images produced with the multiple radiation source are recorded in a set of films 35 (recording ~ayers~ stacked one above the other in which film by film, the object area and the associated overlap of the shadow images become lesser and lesser.
This means tha-t, when a relatively large object : ~54~5~7 ```:
PHD 79 119 3 16~9-1980 area is :irradia-ted, it is possible to record shadow images of an object on a first film, these shadow images over-lapping one another to a large extent but from which it '; is possible to make an initial diagnosis of the patient.
' 5 At the same time, without the patient or the object having to be irradiated again, further shadow images -of a smaller area of the object are produced which shadow images do not overlap one another or only to a slight extent. From these shadow images it is then possible to reconstruct artefact-'' lO free (small) images of a layer of the object. It is im-portant here that the medically relevant object detail should still be present in the masked (thus small) object ' area.
Fig. 1 represents schematically an embodiment of the invention.
It shows a multiple radiation source 1 with three X-ray tubes 2, 3 and 4. The object 5 is mas~ed with a diaphragm arrangement 6, for example a diaphragm plate. The X-ray beams 2a, 3a, 4a can be restricted in such a way 20 that an area of the `object which is i~radiated, which is as large as possible~ or that the ~ilm formats used are fully exposed. The diaphragm 6 can be provided with dia-phragm apertures of different or the same size. Diaphragm apertures of a different size can be used, for example, 25 if the shadow images are to be exposed with little overlap and distributed as uniformly as possible over a film. It is also, of course, possi'ble to arrange underneath the object, that is to say 'between objec-t and first recording layer, a further diaphragm for masking the primary beam of 30 rays (not shown).
The shadow images 7a are recorded on a film 8 at an object-film-distànce OFA1. With this distance and with this masked object area -the individual shadow images over-lap considerably. The result of this is reduced image 35 quality o~ the reconstructed image of a layer of the object.
' At the distances OFA2 and OFA3, for example, further films 9 and 10 are simultaneously arranged on which the more strongly masked shadow images 7b and 7c are recorded wi-th ~lS~S~7 . ~, ., the aid of diaphragms (for example lead diaphragms) 11 and 12 arranged between them. For the sake of clarity the full paths of the beams are shown only for radiation source 4.
The diaphragm apertures of the diaphragm arrangements 11 and 12 become smaller with increasing object-film distance.
In this example, therefore, the perspective images 7c are recorded separately at the distance OFA3. The masking can be done, for example, centrally to the primary beams of rays 2a, 3a, 4a, but also in any other form. Furthermore, 10 the masking may also be different for the individual shadow images~ the purpose being always to obtain li-ttle or no overlap of the shadow images. Without the diaphragm arrangement 11 and 12 the path of the beam for X-ray source 4 would be as shown with the dashed lines 15.
In this example the object-film distance OFA1 is selected in such a way that the film format of film 8 is utilized to the optimum, i.e. right to the edge. Films 8, 9 and 10 are combined, in a kno~in manner, on both sides with intensifying foils; for the sake of clarity, however, these 20 have not been shown. By suitable adaptation of the inten-sifier foils (intensification factor) it is possible to ensure that the varying irnage inforlnation (degree of over-lap, object-film distance~ is recorded on the d:ifferen-t filrns 8, 9 and 10 with appro~imately the same photographic 25 densi-ty. The intensification factor is on a r:ising scale from 8 to 10. In principle, the adap-ta-tion can a:Lso be achieved by using X-ray films of different sensitivity.
When such a set of films is used, the dose of radiation to `
which -the patient is subjected increases only insubstan-3U tia]ly.
Filrns 7, 8 and 9 are housed, preferably, in a cornmon film cassette (simul-taneous cassette) or are simul-taneously moved into their respective position by means of a film-changing device. In addition, the individual dia-35 phragm arrangements 11 or 12 have a thickness decreasingtowards the edge of -the diaphragm apertures, so that the edges of the shadow images will face out. From tihe shadow images it is possible~ using known decoding methods (DE-AS
~;4S~7 ~' ~; 27 19 386 and 27 46 035), to obtain images of layers of the three-dimensional object by means of scale variation and correlation. All the shadow images can be evaluated one after the other with the same decoding device. Rough object orientation is then possible with the layer images recon-structed from the considerably overlapping shadow images 7a, whereas detailed and accurate diagnoses can be made with the layer images reconstructed from shadow images 7b or 7c that have little or no overlap at all. It is assumed, 10 of course, that the desired object detail was also recorded in the set of shadow images present. By means of so-called "survey" exposures, however, that are often made in radio-logy, it is possible to obtain a rough object orientatlon for the exposure of the set of shadow images with the 5 multiple radiation source.
:,
In the German Patent application DE-OS 25 14 988 by U. Tiemens and which was published on October 10, 1976, 10 there has already been shown, using a multiple radiation source containing X-ray tubes, how to record coded images on several successive films, the coded images consisting in each case of shadow images superimposed on one another to more or lesser degrees. From these coded images it is pos-15 sible, in a later step, to reconstruct images of layers ofthe ob~ect (see German patent applications DE-OS 27 19 386 and 27 46 035 by H. Weiss et al which were published on April 5, 1979 and April 19, 1979, respectively).
The images of layers of an object (DE-OS 2514 988) 20 are obtained in principle from shadow images, but the latter are not present in an isolated but in an overlapped form, then because of this overlap additional artefacts are trans-ferred into the reccnstructed image in the process of layer representation and thus impair the picture quality. The 25 influence of the artefacts becomes greater with increasing degree of overlap. The artefacts can in fact be removed;
but the method requires multichannel decoding devices for decoding the overlapping shadow images recorded in each of the respective planes. By means of separate shadow images 30 in each recording plane, however, i~ is possible to avoid the above artefacts and thus considerably improve the image quality. In the case of separate images, however, the object size is severely limited unless film formats that are too big are used. Using a beam geometry that is tech-35 nically feasible (approximately 25 tubes, focus-object ~.
~54S~7 Pl~ 79 119 2 1~-9-198() distance FOD = 1200 mm (object-film distance OFA = 500 mm)) and a commercial film format of 40 x 40 cm2 it is only possible therefore to record objec-ts with a diameter of approxima-tely 50 mm, separately. In objects of this size, however, it is very difficult for the doctor to make an accurate diagnosis because, with this size, orientation towards adjacent, known and larger object details (for example vessels filled with contrast medium), which can be an important aid to a doctor making his diagnosis, is usu-lO ally impossible because this information is not present inthe images or lies at an unfavourable spot, for example at the edge of the image. I-t is desirable, therefore~ that an image first be prepared of a relatively large object area, which will enable the doctor to orientate himself. An 15 additional exposure, however, means a greater radiation load on the patient. The patient has also to be subjected to more contrast medium if this is being used for exposure purposes. The longer examination period -that results is also, of course, a disadvantage for both patient and doctor.
It is the objec-t of the present invention, there-fore, to create a device for producing images of a layer of an object whereby it is possible to prepare both shadow images of large objec-t areas in the case of relatively marked overlap of the shadow images and simultaneously 25 shadow images, which hardly or not overlap, which repre-sent only a part of said large object area. According to the invention the device is charac-terized in that in fron-t of each recording layer is placed a diaphragm arrangement allocated to it for masking of the beams of rays, -the 30 diaphragm apertures o~ each diaphragm arrangement being so much the smaller the greater the distance between the diaphragm arrangement and the radiation sources.
In this way, the shadow images produced with the multiple radiation source are recorded in a set of films 35 (recording ~ayers~ stacked one above the other in which film by film, the object area and the associated overlap of the shadow images become lesser and lesser.
This means tha-t, when a relatively large object : ~54~5~7 ```:
PHD 79 119 3 16~9-1980 area is :irradia-ted, it is possible to record shadow images of an object on a first film, these shadow images over-lapping one another to a large extent but from which it '; is possible to make an initial diagnosis of the patient.
' 5 At the same time, without the patient or the object having to be irradiated again, further shadow images -of a smaller area of the object are produced which shadow images do not overlap one another or only to a slight extent. From these shadow images it is then possible to reconstruct artefact-'' lO free (small) images of a layer of the object. It is im-portant here that the medically relevant object detail should still be present in the masked (thus small) object ' area.
Fig. 1 represents schematically an embodiment of the invention.
It shows a multiple radiation source 1 with three X-ray tubes 2, 3 and 4. The object 5 is mas~ed with a diaphragm arrangement 6, for example a diaphragm plate. The X-ray beams 2a, 3a, 4a can be restricted in such a way 20 that an area of the `object which is i~radiated, which is as large as possible~ or that the ~ilm formats used are fully exposed. The diaphragm 6 can be provided with dia-phragm apertures of different or the same size. Diaphragm apertures of a different size can be used, for example, 25 if the shadow images are to be exposed with little overlap and distributed as uniformly as possible over a film. It is also, of course, possi'ble to arrange underneath the object, that is to say 'between objec-t and first recording layer, a further diaphragm for masking the primary beam of 30 rays (not shown).
The shadow images 7a are recorded on a film 8 at an object-film-distànce OFA1. With this distance and with this masked object area -the individual shadow images over-lap considerably. The result of this is reduced image 35 quality o~ the reconstructed image of a layer of the object.
' At the distances OFA2 and OFA3, for example, further films 9 and 10 are simultaneously arranged on which the more strongly masked shadow images 7b and 7c are recorded wi-th ~lS~S~7 . ~, ., the aid of diaphragms (for example lead diaphragms) 11 and 12 arranged between them. For the sake of clarity the full paths of the beams are shown only for radiation source 4.
The diaphragm apertures of the diaphragm arrangements 11 and 12 become smaller with increasing object-film distance.
In this example, therefore, the perspective images 7c are recorded separately at the distance OFA3. The masking can be done, for example, centrally to the primary beams of rays 2a, 3a, 4a, but also in any other form. Furthermore, 10 the masking may also be different for the individual shadow images~ the purpose being always to obtain li-ttle or no overlap of the shadow images. Without the diaphragm arrangement 11 and 12 the path of the beam for X-ray source 4 would be as shown with the dashed lines 15.
In this example the object-film distance OFA1 is selected in such a way that the film format of film 8 is utilized to the optimum, i.e. right to the edge. Films 8, 9 and 10 are combined, in a kno~in manner, on both sides with intensifying foils; for the sake of clarity, however, these 20 have not been shown. By suitable adaptation of the inten-sifier foils (intensification factor) it is possible to ensure that the varying irnage inforlnation (degree of over-lap, object-film distance~ is recorded on the d:ifferen-t filrns 8, 9 and 10 with appro~imately the same photographic 25 densi-ty. The intensification factor is on a r:ising scale from 8 to 10. In principle, the adap-ta-tion can a:Lso be achieved by using X-ray films of different sensitivity.
When such a set of films is used, the dose of radiation to `
which -the patient is subjected increases only insubstan-3U tia]ly.
Filrns 7, 8 and 9 are housed, preferably, in a cornmon film cassette (simul-taneous cassette) or are simul-taneously moved into their respective position by means of a film-changing device. In addition, the individual dia-35 phragm arrangements 11 or 12 have a thickness decreasingtowards the edge of -the diaphragm apertures, so that the edges of the shadow images will face out. From tihe shadow images it is possible~ using known decoding methods (DE-AS
~;4S~7 ~' ~; 27 19 386 and 27 46 035), to obtain images of layers of the three-dimensional object by means of scale variation and correlation. All the shadow images can be evaluated one after the other with the same decoding device. Rough object orientation is then possible with the layer images recon-structed from the considerably overlapping shadow images 7a, whereas detailed and accurate diagnoses can be made with the layer images reconstructed from shadow images 7b or 7c that have little or no overlap at all. It is assumed, 10 of course, that the desired object detail was also recorded in the set of shadow images present. By means of so-called "survey" exposures, however, that are often made in radio-logy, it is possible to obtain a rough object orientatlon for the exposure of the set of shadow images with the 5 multiple radiation source.
:,
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Device for producing images of a layer of a three-dimensional object, with radiation sources arranged in a radiation source plane, for irradiating the object with beams of penetrating rays from different directions, and with several planar recording layers, arranged par-allel to one another, for recording all shadow images thereby generated, characterized in that in front of each recording layer is located a diaphragm arrangement allo-cated to it, for masking of the beams of rays, wherein the diaphragm apertures of each particular diaphragm arrange-ment are so much the smaller the further the distance between the diaphragm arrangement and the radiation sources.
2. Device as claimed in Claim 1, characterized in that a diaphragm arrangement has diaphragm apertures of equal size which lie centrally with respect to the beams of rays.
3. Device as claimed in Claim 1, characterized in that the diaphragm arrangements each have diaphragm aper-tures that differ from one another in size, shape and position.
4. Device as claimed in Claim 2 or 3, in which the diaphragm arrangements are in the form of diaphragm plates.
5. Device as claimed in Claim 1, 2 or 3, character-ized in that the diaphragm arrangements decrease in thick-ness towards the edge of the diaphragm apertures.
6. Device as claimed in Claim 1, characterized in that the diaphragm arrangements, together with the record-ing layers, are arranged in a light-tight cassette.
7. Device as claimed in Claim 6, characterized in that a film-changing device is provided for positioning the cassette or the recording medium in their respective expos-ure positions.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000362569A CA1154547A (en) | 1980-10-16 | 1980-10-16 | Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000362569A CA1154547A (en) | 1980-10-16 | 1980-10-16 | Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154547A true CA1154547A (en) | 1983-09-27 |
Family
ID=4118176
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000362569A Expired CA1154547A (en) | 1980-10-16 | 1980-10-16 | Device for producing images of a layer of an object from multiple shadow images with varying degrees of overlap |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1154547A (en) |
-
1980
- 1980-10-16 CA CA000362569A patent/CA1154547A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |