EP0013241A1 - Radiological intensifier tube with video output and radiological network provided with such a tube - Google Patents

Radiological intensifier tube with video output and radiological network provided with such a tube Download PDF

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Publication number
EP0013241A1
EP0013241A1 EP79401064A EP79401064A EP0013241A1 EP 0013241 A1 EP0013241 A1 EP 0013241A1 EP 79401064 A EP79401064 A EP 79401064A EP 79401064 A EP79401064 A EP 79401064A EP 0013241 A1 EP0013241 A1 EP 0013241A1
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EP
European Patent Office
Prior art keywords
target
image
tube
radiological
layer
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Granted
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EP79401064A
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German (de)
French (fr)
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EP0013241B1 (en
Inventor
Jean Ricodeau
Henri Rougeot
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Thales SA
Thomson CSF Scpi
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Thomson CSF Scpi
Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/49—Pick-up adapted for an input of electromagnetic radiation other than visible light and having an electric output, e.g. for an input of X-rays, for an input of infrared radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens

Definitions

  • the invention relates to a radiological image intensifier tube, and to the radiology chain which includes such an intensifier.
  • radiological image intensifier tubes In radiological image intensifier tubes (IIR tubes) the incident X-rays are converted into light in a luminescent screen, then into phtoelectrons in a photocathode. These photo-electrons are accelerated by electronic optics and focused on a luminescent powder giving a luminous image of the density of the flux of the indicative X photons. For a televised operation, this output image is taken up by an optic which transforms the image on the photosensitive target of a shooting tube, a vidicon for example, where it creates a distribution of charges which are read by an electron beam. then giving the video signal.
  • IIR tubes radiological image intensifier tubes
  • a first solution of the prior art was an IIR-vidicon coupling by optical fibers.
  • the light output screen of the IIR is brought into contact with a wafer of optical fibers as well as the target of the shooting tube, the two wafers then being coupled together (see French patent n ° 74.23 277). .
  • optical fibers have flaws which prove to be serious for radiological use.
  • a defect in one of the individual fibers forming the whole of the wafer results in a black spot or area; moreover, the design of the fiber mosaic is apparent on the image.
  • a second solution of the prior art consists in eliminating the output screen of the intensifier and the coupling optics and in sending the photo-electrons directly to a target of the vidicon, sensitive to the impact of the electrons. all being placed in the same enclosure - such as a diode mosaic target. This gives an X-ray gain - very high video signal.
  • the object of the invention is another solution not having these drawbacks.
  • the radiological image intensifier tube with video output comprises, in the same envelope maintained under vacuum, a luminescent input screen in contact with a photocathode which converts X-rays into photo-electrons, as in an intensifier. known image. These phot-electrons are focused by electronic optics and accelerated towards a layer of luminescent powder, after having passed through a metallic layer making them lose part of their energy.
  • This luminescent layer is, according to the invention, deposited on the rear face of a photo-sensitive target previously covered with a semi-transparent layer.
  • Figure 1 shows in schematic section, such a tube, and Figure 2 the structure of the target compared to that of a target used in the prior art.
  • the tube of FIG. 1 has two sections I and II, image and analysis sections respectively.
  • the phot-electrons directed from the entry screen of the tube towards the target which constitutes the entry face of the second section, a target vidicon for example .
  • This target is scanned by an electron beam from the other end of this section on the right of the figure.
  • the section in order, from left to right of the drawing, an input screen 10, composed, according to known art, of a scintillator 11 and a photocathode 12, and exposed to incident X-radiation (arrows of left) crossing the object to be observed 30.
  • a beam of electrons or photo-electrons, coming from photocathode 12, is focused and accelerated towards the exit face of this first section occupied by the target of the second section.
  • This target is marked 16 and the various focusing electrodes marked 14; the electron beam is represented by the line beam in dashed lines.
  • the second section of the tube further comprises means of produc tion of an electron brush, symbolized by the arrow, and means ensuring, in operation, the point-by-point scanning of the target by the latter; this scanning uses a deflection device carrying the mark 20; the cathode and all the electrodes of the barrel bear the mark 18. All of the two sections are kept under vacuum in the envelope 24.
  • the acceleration of the photoelectrons is ensured by a DC voltage source shown at 22.
  • the assembly is placed in the protective envelope 25.
  • the video signal is taken from the electron beam circuit, under the conditions known in this matter and not shown.
  • FIG. 2 (a) shows a schematic section of the target 16 of the tubes of the invention, compared to that used in tubes of the same type of the prior art ( Figure 2b), and their incorporation into the intensifier tube.
  • the target of the invention comprises superimposed, on the target proper 4, on the side opposite to that read by the electron beam (bottom arrow), three layers which consist respectively of a metal barrier layer 1, a luminescent screen 2 and a semi-transparent layer 3, unlike the targets of the known art (FIG. 2b), which comprise, in contact with the target 4 proper, only the metallic layer 1.
  • This layer is, for example, made of aluminum and has a thickness of 1 micrometer.
  • the metal layer 1 In the target of the invention braking of the electrons is exerted, as in the previous case, by the metal layer 1; this braking leaves them enough energy to excite the underlying luminescent layer 2 which emits photons towards the semi-transparent layer 3; the metal layer 1, also made of aluminum for example, in this case has a thickness less than that of the prior art, of the order of 5000 angstroms.
  • the photons emitted by part 2 of the target are absorbed by the semi-transparent layer 3 in a proportion which depends on its thickness and its nature.
  • the semi-transparent material used is for example chromium, deposited on the target proper 4 over a thickness of approximately 500 angtroms; the luminescent layer is made of a cathodo-luminescent material such as calcium tungstate, Ca W0 4 , with a thickness of 5000 angtroms also, or zinc sulfide, ZnS.
  • the reduction in gain takes place at two levels; first by braking, as in the prior art, at the metal barrier layer 1, and then at the semi-transparent layer 3, by photon absorption.
  • This arrangement therefore makes it possible to use two parameters to reduce the X-ray gain - video signal and adjust its value between the desired limits.
  • a sufficiently high acceleration voltage makes it possible to confer on the photoelectrons sufficient energy for them to pass through both the metal barrier layer 1, the luminescent layer and the semi-transparent layer, and that they reach the target itself 4 and directly excite it, with a gain high enough to allow fluorography observations at low dose of incident X-rays.
  • each incident photon X creates P photo-electrons (around 150 to fix ideas), which photo-electrons each create G photons in the luminescent layer 2 of the target of the tube of the invention, that the semi-transparent layer 3 partially absorbs to allow only the fraction T to pass through; each of these photons creates a carrier in the target proper 4; the number of free carriers in the target per incident photon X is therefore finally TGP.
  • This gain is reduced to the last two factors GP in the case of a target of the known art comprising only the barrier layer 1, by admitting that each incident electron creates in the target a number G of carriers.
  • the input screen 10 of the tubes of the invention is of the type used in the art for the formation of radiological images, namely a two-layer screen, one of cesium iodide ICs, by example with a thickness of 100 to 200 micrometers, and the other in a photo-emissive material, such as the potassium sodium antimonide, Sb Na 2 K, with a thickness of the order of 500 angstroms.
  • the target proper 4 read by the electron brush, was a semiconductor target constituted by a mosaic of diodes formed in a semiconductor substrate, as shown in the drawings, where these diodes bear the mark 42 and the substrate mark 40. More generally, this target can be, within the limits of the invention, any photo-sensitive target, read by an electron beam, of the prior art.
  • the tubes of the invention are used in radiology channels, in particular in fluoroscopy, for direct viewing on a television screen, or in fluorography for viewing with memory.
  • the chain diagram of this kind is given in FIG. 3 where the whole of the tube carries the mark 100.
  • the mark 102 designates the display screen terminating the chain in the first case and the marks 104 and 106 the memory tube and the display screen, in the second case.
  • the signals are taken directly from the exit of the tube in the target scanning circuit, under known conditions.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Measurement Of Radiation (AREA)

Abstract

L'invention concerne un tube intensificateur d'image radiologique à sortie vidéo. Le tube comporte, dans une même enveloppe à vide, une section image et une section d'analyse ayant une face commune occupée par le cible 16. Dans la section image est formée, dans la cible, une image électrique correspondant à l'image en rayons X incidente; cette image est lue dans la section d'analyse par un pinceau d'électrons balayant la cible point par point. Cette cible a, dans les tubes de l'invention, une structure permettant de limiter le gain photons X - signal vidéo et de la régler entre deux valeurs prédéterminées; elle comporte, sur sa face qui reçoit les photo-électrons e<->, une couche barriére en métal 1 recouvrant une couche luminescente 2, en contact elle-même avec une couche semi-transparente 3 recouvrant la cible proprement dite 4. Application, dans une large gamme, de doses indicentes, en fluoroscopie comme en fluorographie.The invention relates to a radiological image intensifier tube with video output. The tube comprises, in the same vacuum envelope, an image section and an analysis section having a common face occupied by the target 16. In the image section is formed, in the target, an electric image corresponding to the image in incident X-rays; this image is read in the analysis section by an electron brush scanning the target point by point. This target has, in the tubes of the invention, a structure making it possible to limit the gain of X photons - video signal and to adjust it between two predetermined values; it comprises, on its face which receives the photoelectrons e <->, a metal barrier layer 1 covering a luminescent layer 2, in contact itself with a semi-transparent layer 3 covering the target proper 4. Application, in a wide range, of indicative doses, in fluoroscopy as in fluorography.

Description

L'invention concerne un tube intensificateur d'image radiologique, et la chaîne de radiologie qui comporte un tel intensificateur.The invention relates to a radiological image intensifier tube, and to the radiology chain which includes such an intensifier.

Dans les tubes intensificateurs d'image radiologique (tubes IIR) les rayons X incidents sont convertis en lumière dans un écran luminescent, puis en phto-électrons dans une photocathode. Ces photo-électrons sont accélérés par une optique électronique et focalisés sur une poudre luminescente donnant une image lumineuse de la densité du flux des photons X indicents. Pour une exploitation télévisée on reprend cette image de sortie par une optique qui reforme l'image sur la cible photosensible d'un tube de prise de vues, un vidicon par exemple, où elle crée une distribution de charges qui sont lues par un faisceau électronique donnant alors le signal vidéo.In radiological image intensifier tubes (IIR tubes) the incident X-rays are converted into light in a luminescent screen, then into phtoelectrons in a photocathode. These photo-electrons are accelerated by electronic optics and focused on a luminescent powder giving a luminous image of the density of the flux of the indicative X photons. For a televised operation, this output image is taken up by an optic which transforms the image on the photosensitive target of a shooting tube, a vidicon for example, where it creates a distribution of charges which are read by an electron beam. then giving the video signal.

Il est souhaitable de supprimer l'optique de couplage IIR-vidicon à cause de son poids et de son encombrement, de son manque de luminosité, et d'une façon générale des défauts supplémentaires qu'elle introduit dans la chaîne.It is desirable to remove the IIR-vidicon coupling optics because of its weight and size, its lack of brightness, and generally the additional faults that it introduces into the chain.

Une première solution de l'art antérieur a été un couplage IIR-vidicon par fibres optiques. L'écran de sortie lumineux de l'IIR est mis en contact avec une galette de fibres optiques ainsi que la cible du tube de prise de vues, les deux galettes étant ensuite couplées entre elles (voie. le brevet français n° 74.23 277).A first solution of the prior art was an IIR-vidicon coupling by optical fibers. The light output screen of the IIR is brought into contact with a wafer of optical fibers as well as the target of the shooting tube, the two wafers then being coupled together (see French patent n ° 74.23 277). .

Mais les fibres optiques présentent des défauts qui s'avèrent graves pour un usage radiologique. Un défaut de l'une des fibres individuelles formant l'ensemble de la galette se traduit par un point ou une zone noire ; de plus, le dessin de la mosaïque des fibres est apparent sur l'image.But optical fibers have flaws which prove to be serious for radiological use. A defect in one of the individual fibers forming the whole of the wafer results in a black spot or area; moreover, the design of the fiber mosaic is apparent on the image.

Une deuxième solution de l'art antérieur consiste à supprimer l'écran de sortie de l'intensificateur et l'optique de couplage et à envoyer les photo-électrons directement sur une cible du vidicon, sensible à l'impact des électrons-l'ensemble étant placé dans une même enceinte - telle qu'une cible à mosaïque de diodes. On obtient alors un gain rayons X - signal vidéo très élevé.A second solution of the prior art consists in eliminating the output screen of the intensifier and the coupling optics and in sending the photo-electrons directly to a target of the vidicon, sensitive to the impact of the electrons. all being placed in the same enclosure - such as a diode mosaic target. This gives an X-ray gain - very high video signal.

Malheureusement, il est nécessaire de réduire au maximum le bruit quantique des rayons par l'utilisation de doses X très élevées. De plus, les dimensions du champ d'entrée de l'intensificateur imposent des tensions élevées à l'optique électronique, ce qui donne une énergie élevée aux photo-électrons arrivant sur la cible, et partant, un gain électronique très grand dans la cible. A cause de la dose X élevée et du gain de cible élevé il est nécessaire, pour éviter la saturation électrique de celle-ci, de prévoir des dispositions pour diminuer le gain de la cible. Il faut de plus prévoir, dans ce genre de tubes, la possibilité d'un gain variable de la cible entre 1 et 50 par exemple, pour fonctionner, selon les utilisations, soit en graphie, soit en scopie.Unfortunately, it is necessary to minimize the quantum noise of the rays by the use of very high X doses. In addition, the dimensions of the input field of the intensifier impose high voltages on the electronic optics, which gives high energy to the photoelectrons arriving on the target, and therefore, a very large electronic gain in the target. . Because of the high dose X and the high target gain, it is necessary, in order to avoid the electrical saturation thereof, to make provisions to reduce the target gain. It is also necessary to provide, in this kind of tubes, the possibility of a variable gain of the target between 1 and 50 for example, to function, depending on the uses, either in writing or in scanning.

Pour cela une solution consistait dans l'art antérieur à déposer sur une cible à mosaïque de diodes,du côté de l'arrivée des photo-électrons,une ou plusieurs couches barrière, métalliques, épaisses, par exemple de U um d'aluminium, absorbant une partie de l'énergie des électrons (voir la demande de brevet français n° 77 05 031). Cette couche, bien que diminuant le gain, introduidait un bruit de multiplication considérable dû au fait que la perte d'énergie des photo-électrons dans la couche barrière est un phénomène statistique qui présente des fluctuations importantes.For this, a solution consisted in the prior art of depositing on a target with a diode mosaic, on the side of the arrival of the photoelectrons, one or more barrier layers, metallic, thick, for example of U μm of aluminum, absorbing part of the energy of the electrons (see the request for French patent n ° 77 05 031). This layer, although decreasing the gain, introduced a considerable multiplication noise due to the fact that the energy loss of the photoelectrons in the barrier layer is a statistical phenomenon which presents significant fluctuations.

L'objet de l'invention est une autre solution n'ayant pas ces inconvénients.The object of the invention is another solution not having these drawbacks.

L'invention sera mieux comprise en se reportant à la description qui suit et aux figures jointes qui représentent :

  • - figure 1 : une vue schématique d'ensemble d'un tube intensificateur d'image radiologique de l'invention ;
  • - figures 2a, 2b : des vues en coupe schématique comparées des cibles d'un tube intensificateur d'image radiologique de l'invention et de l'art antérieur respectivement.
  • - figure 3 : un diagramme de chaîne de radiologie utilisant un tube intensificateur d'image de l'invention.
The invention will be better understood by referring to the description which follows and to the attached figures which represent:
  • - Figure 1: a schematic overview of a radiological image intensifier tube of the invention;
  • - Figures 2a, 2b: schematic sectional views compared of the targets of an X-ray image intensifier tube of the invention and the prior art respectively.
  • - Figure 3: a radiology chain diagram using an image intensifier tube of the invention.

Le tube intensificateur d'image radiologique à sortie vidéo selon l'invention comporte, dans une même enveloppe maintenue sous vide, un écran d'entrée luminescent en contact avec une photocathode qui convertit les rayons X en photo-électrons, comme dans un intensificateur d'image connu. Ces phot-électrons sont focalisés par une optique électronique et accélérés vers une couche de poudre luminescente, après avoir traversé une couche métallique leur faisant perdre une partie de leur énergie. Cette couche luminescente est, selon l'invention, déposée sur la face arrière d'une cible photo-sensible recouverte au préalable d'une couche semi-transparente. Les photons lumineux émis par la couche luminescente, et non absorbés dans la couche semi-transparente, créent des porteurs dans la cible, lesquels créent au niveau de la face balayée de la cible une répartition de charges qui est lue par le faisceau d'électrons ; l'ensemble des signaux lus constitue le signal vidéo.The radiological image intensifier tube with video output according to the invention comprises, in the same envelope maintained under vacuum, a luminescent input screen in contact with a photocathode which converts X-rays into photo-electrons, as in an intensifier. known image. These phot-electrons are focused by electronic optics and accelerated towards a layer of luminescent powder, after having passed through a metallic layer making them lose part of their energy. This luminescent layer is, according to the invention, deposited on the rear face of a photo-sensitive target previously covered with a semi-transparent layer. The light photons emitted by the luminescent layer, and not absorbed in the semi-transparent layer, create carriers in the target, which create at the level of the scanned face of the target a charge distribution which is read by the electron beam; all the signals read constitute the video signal.

La figure 1 montre en coupe schématique, un tel tube, et la figure 2 la structure de la cible comparé à celle d'une cible utilisée dans l'art antérieur.Figure 1 shows in schematic section, such a tube, and Figure 2 the structure of the target compared to that of a target used in the prior art.

Le tube de la figure 1 comporte deux sections I et II,sections image et d'analyse respectivement. Dans la première de ces deux sections, à gauche sur la figure, sont produits les phot-électrons dirigés de l'écran d'entrée du tube vers la cible qui constitue la face d'entrée de la deuxième section, une cible vidicon par exemple. Cette cible est balayé par un faisceau d'électrons issu de l'autre extrémité de cette section à droite de la figure. La section dans l'ordre, de gauche à droite du dessin, un écran d'entrée 10, composé, selon l'art connu, d'un scintillateur 11 et d'une photocathode 12, et exposé au rayonnement X incident (flêches de gauche) traversant l'objet à observer 30.The tube of FIG. 1 has two sections I and II, image and analysis sections respectively. In the first of these two sections, on the left in the figure, are produced the phot-electrons directed from the entry screen of the tube towards the target which constitutes the entry face of the second section, a target vidicon for example . This target is scanned by an electron beam from the other end of this section on the right of the figure. The section in order, from left to right of the drawing, an input screen 10, composed, according to known art, of a scintillator 11 and a photocathode 12, and exposed to incident X-radiation (arrows of left) crossing the object to be observed 30.

En fonctionnement, un faisceau d'électrons ou photo-électrons, issu de la photocathode 12, est focalisé et accéléré vers la face de sortie de cette première section occupée par la cible de la deuxième section. Cette cible porte le repère 16 et les diverses électrodes de focalisation le repère 14 ; le faisceau d'électrons est représenté par le faisceau de droites en traits interrompus. La deuxième section du tube comprend en outre des moyens de production d'un pinceau d'électrons, symbolisé par la flèche, et des moyens assurant, en fonctionnement, le balayage point par point de la cible par celui- ci ; ce balayage utilise un dispositif de déviation portant le repère 20 ; la cathode et l'ensemble des électrodes du canon portent le repère 18. L'ensemble des deux sections est maintenu sous vide dans l'enveloppe 24. En fonctionnement, l'accélération des photo-électrons est assurée par une source de tension continue représentée en 22. Enfin, l'ensemble est placé dans l'enveloppe de protection 25. Le signal vidéo est prélévé sur le circuit du faisceau d'électrons, dans les conditions connues en cette matière et non représentées.In operation, a beam of electrons or photo-electrons, coming from photocathode 12, is focused and accelerated towards the exit face of this first section occupied by the target of the second section. This target is marked 16 and the various focusing electrodes marked 14; the electron beam is represented by the line beam in dashed lines. The second section of the tube further comprises means of produc tion of an electron brush, symbolized by the arrow, and means ensuring, in operation, the point-by-point scanning of the target by the latter; this scanning uses a deflection device carrying the mark 20; the cathode and all the electrodes of the barrel bear the mark 18. All of the two sections are kept under vacuum in the envelope 24. In operation, the acceleration of the photoelectrons is ensured by a DC voltage source shown at 22. Finally, the assembly is placed in the protective envelope 25. The video signal is taken from the electron beam circuit, under the conditions known in this matter and not shown.

La figure 2(a) montre une coupe schématique de la cible 16 des tube de l'invention, comparé à celle utilisée dans les tubes du même type de l'art antérieur (figure 2b), et leur incorporation dans le tube intensificateur. On voit sur ces figures l'écran d'entrée 10 (11, 12) soumis au rayonnement X incident (flêche ondulée) et la cible 16 de la figure précédente, entre lesquels sont accélérés les électrons de charges e . La cible de l'invention, figure 2a, comporte superposées, sur la cible proprement dite 4, du côté opposé à celui lu par le faisceau d'électrons (flèche du bas), trois couches qui consistent respectivement en une couche barrière métallique 1, un écran luminescent 2 et une couche semi-transparente 3, contrairement aux cibles de l'art connu (figure 2b), qui ne comportent, en contact avec la cible 4 proprement dite, que la couche métallique 1.Figure 2 (a) shows a schematic section of the target 16 of the tubes of the invention, compared to that used in tubes of the same type of the prior art (Figure 2b), and their incorporation into the intensifier tube. We see in these figures the input screen 10 (11, 12) subjected to incident X-radiation (wavy arrow) and the target 16 of the previous figure, between which the electrons of charge e are accelerated. The target of the invention, FIG. 2a, comprises superimposed, on the target proper 4, on the side opposite to that read by the electron beam (bottom arrow), three layers which consist respectively of a metal barrier layer 1, a luminescent screen 2 and a semi-transparent layer 3, unlike the targets of the known art (FIG. 2b), which comprise, in contact with the target 4 proper, only the metallic layer 1.

Dans ces dernières, les électrons sont freinés par la couche barrière 1, de façon à aborder la cible avec une énergie suffisamment réduite par rapport à leur énergie d'accélératiop pour éviter les inconvénients signalés. Cette couche est, par exemple, en aluminium et présente une épaisseur de 1 micromètre.In the latter, the electrons are braked by the barrier layer 1, so as to approach the target with a sufficiently reduced energy compared to their acceleration energy to avoid the reported disadvantages. This layer is, for example, made of aluminum and has a thickness of 1 micrometer.

Dans la cible de l'invention un freinage des électrons est exercé, comme dans le cas précédent, par la couche métallique 1 ; ce freinage leur laisse suffisamment d'énergie pour exciter la couche luminescente sous-jacente 2 qui émet des photons vers la couche semi-transparent 3 ; la couche métallique 1, également en aluminium par exemple, présente dans ce cas une épaisseur moins grande que l'art connu, de l'ordre de 5000 angstroms. Les photons émis par la partie 2 de la cible sont absorbés par la couche semi-transparente 3 dans une proportion qui dépend de son épaisseur et de sa nature. Le matériau semi-transparent utilisé est par exemple le chrome, déposé sur la cible proprement dite 4 sur une épaisseur de 500 angtroms environ ; la couche luminescente est faite d'un matériau cathodo-luminescent tel que le tungstate de calcium, Ca W04, avec une épaisseur de 5000 angtroms également, ou le sulfure de zinc, ZnS.In the target of the invention braking of the electrons is exerted, as in the previous case, by the metal layer 1; this braking leaves them enough energy to excite the underlying luminescent layer 2 which emits photons towards the semi-transparent layer 3; the metal layer 1, also made of aluminum for example, in this case has a thickness less than that of the prior art, of the order of 5000 angstroms. The photons emitted by part 2 of the target are absorbed by the semi-transparent layer 3 in a proportion which depends on its thickness and its nature. The semi-transparent material used is for example chromium, deposited on the target proper 4 over a thickness of approximately 500 angtroms; the luminescent layer is made of a cathodo-luminescent material such as calcium tungstate, Ca W0 4 , with a thickness of 5000 angtroms also, or zinc sulfide, ZnS.

Ainsi, dans l'invention, la réduction du gain s'effectue à deux niveaux ; d'abord par freinage, comme dans l'art antérieur, au niveau de la couche barrière métallique 1, et, ensuite, au niveau de la couche semi-transparente 3, par absorption photonique. Cette disposition permet donc d'user de deux paramètres pour réduire le gain rayons X - signal vidéo et régler sa valeur entre les limites désirées.Thus, in the invention, the reduction in gain takes place at two levels; first by braking, as in the prior art, at the metal barrier layer 1, and then at the semi-transparent layer 3, by photon absorption. This arrangement therefore makes it possible to use two parameters to reduce the X-ray gain - video signal and adjust its value between the desired limits.

Elle permet notamment de réduire-ce gain en agissant sur un nombre élevé de particules, ce qui, toutes choses égales réduit le bruit. Elle permet d'ajuster le gain, en agissant sur la tension d'accélération des électrons notamment.It makes it possible in particular to reduce this gain by acting on a high number of particles, which, all things being equal reduces noise. It makes it possible to adjust the gain, by acting on the acceleration voltage of the electrons in particular.

De plus, une tension d'accélération suffisamment élevée permet de conférer aux photo-électrons une énergie suffisante pour qu'ils traversent à la fois la couche barrière métallique 1, la couche luminescente et la couche semi-transparente, et qu'ils atteignent la cible proprement dite 4 et l'excitent directement, avec un gain assez élevé pour permettre les observations en fluorographie à faible dose de rayons X incidents. Ces possibilités constituent des avantages de l'invention par rapport à l'art antérieur.In addition, a sufficiently high acceleration voltage makes it possible to confer on the photoelectrons sufficient energy for them to pass through both the metal barrier layer 1, the luminescent layer and the semi-transparent layer, and that they reach the target itself 4 and directly excite it, with a gain high enough to allow fluorography observations at low dose of incident X-rays. These possibilities constitute advantages of the invention compared to the prior art.

Le gain se décompose comme suit : chaque photon X incident crée P photo-électrons (environ 150 pour fixer les idées), lesquels photo-électrons créent chacun G photons dans la couche luminescente 2 de la cible du tube de l'invention, que la couche semi-transparente 3 absorbe en partie pour n'en laisser passer que la fraction T ; chacun de ces photons crée un porteur dans la cible proprement dite 4 ; le nombre de porteurs libres dans la cible par photon X incident est donc finalement TGP. Ce gain se réduit aux deux derniers facteurs GP dans le cas d'une cible de l'art connu ne comportant que la couche barrière 1, en admettant que chaque électron incident crée dans la cible un nombre G de porteurs.The gain breaks down as follows: each incident photon X creates P photo-electrons (around 150 to fix ideas), which photo-electrons each create G photons in the luminescent layer 2 of the target of the tube of the invention, that the semi-transparent layer 3 partially absorbs to allow only the fraction T to pass through; each of these photons creates a carrier in the target proper 4; the number of free carriers in the target per incident photon X is therefore finally TGP. This gain is reduced to the last two factors GP in the case of a target of the known art comprising only the barrier layer 1, by admitting that each incident electron creates in the target a number G of carriers.

L'écran d'entrée 10 des tubes de l'invention est du type de ceux utilisés dans l'art pour la formation d'images radiologiques, à savoir un écran à deux couches, l'une d'iodure de césium ICs, par exemple d'une épaisseur de 100 à 200 micromètres, et l'autre en un matériau photo-émissif, comme l'antimoniure de sodium de potassium, Sb Na2K, avec une épaisseur de l'ordre de 500 angstroms.The input screen 10 of the tubes of the invention is of the type used in the art for the formation of radiological images, namely a two-layer screen, one of cesium iodide ICs, by example with a thickness of 100 to 200 micrometers, and the other in a photo-emissive material, such as the potassium sodium antimonide, Sb Na 2 K, with a thickness of the order of 500 angstroms.

On a admis que la cible proprement dite 4, lue par le pinceau d'électrons, était une cible à semi-conducteur constitué par une mosaïque de diodes formées dans un substrat semi-conducteur, comme le montrent les dessins, où ces diodes portent le repère 42 et le substrat le repère 40. Plus généralement, cette cible peut être, dans les limites de l'invention, toute cible photo-sensible, lue par un faisceau d'électrons, de l'art antérieur.It was admitted that the target proper 4, read by the electron brush, was a semiconductor target constituted by a mosaic of diodes formed in a semiconductor substrate, as shown in the drawings, where these diodes bear the mark 42 and the substrate mark 40. More generally, this target can be, within the limits of the invention, any photo-sensitive target, read by an electron beam, of the prior art.

Les tubes de l'invention sont utilisés dans les chaînes de radiologie, notamment en fluoroscopie, pour la visualisation directe sur un écran de télévision, ou en fluorographie pour la visualisation avec mémoire. Le diagramme de chaînes de ce genre est donné sur la figure 3 où l'ensemble du tube porte le repère 100. Le repère 102 désigne l'écran de visualisation terminant la chaîne dans le premier cas et les repères 104 et 106 le tube à mémoire et l'écran de visualisation, dans le deuxième cas. Les signaux sont prélevés directement à la sortie du tube dans le circuit de balayage de la cible, dans les conditions connues.The tubes of the invention are used in radiology channels, in particular in fluoroscopy, for direct viewing on a television screen, or in fluorography for viewing with memory. The chain diagram of this kind is given in FIG. 3 where the whole of the tube carries the mark 100. The mark 102 designates the display screen terminating the chain in the first case and the marks 104 and 106 the memory tube and the display screen, in the second case. The signals are taken directly from the exit of the tube in the target scanning circuit, under known conditions.

Claims (3)

1. Tube ïntensificateur d'image radiologique à sortie vidéo réunissant, dans une même enveloppe à vide, de part et d'autre d'une cible, composée de quatre parties, d'une part, des moyens transformant l'image en rayon X incidente en un faisceau de photo-électrons dirigé vers cette cible et y produisant un impact sous l'effet duquel est formé dans la cible une image électrique de l'image incidente, et d'autre part, des moyens de lecture des signaux électriques constitutifs de l'image ainsi formée, caractérisé en ce que cette cible comporte, du côté exposé aux photo-électrons, trois couches successives consistant en une barrière métallique, recouvrant une couche d'un matériau luminescent, cette dernière étant en contact avec une couche semi-transparente recouvrant la cible proprement dite dans laquelle est formée ladite image électrique.1. Radiological image intensifier tube with video output uniting, in the same vacuum envelope, on either side of a target, composed of four parts, on the one hand, means transforming the image into X-ray incident in a beam of photo-electrons directed towards this target and producing an impact thereon under the effect of which is formed in the target an electric image of the incident image, and on the other hand, means for reading the constituent electrical signals of the image thus formed, characterized in that this target comprises, on the side exposed to photo-electrons, three successive layers consisting of a metal barrier, covering a layer of luminescent material, the latter being in contact with a semi-layer -transparent covering the target itself in which said electrical image is formed. 2. Tube intensificateur d'image radiologique selon la revendication 1, caractérisé en ce que la cible proprement dite est une cible à mosaïque de diodes formée dans un substrat semi-conducteur.2. X-ray image intensifier tube according to claim 1, characterized in that the target itself is a diode mosaic target formed in a semiconductor substrate. 3. Chaîne de radiologie comprenant un tube intensificateur d'image radiologique et un écran alimenté par les signaux de lexture de ce tube pour la visualisation de 11.image incidente, caractérisé en ce que le tube intensificateur est un tube suivant l'une des revendications 1 ou 2.3. X-ray chain comprising a radiological image intensifier tube and a screen fed by the signals of lexture of this tube for viewing 1 1. incident image, characterized in that the intensifier tube is a tube according to one of the claims 1 or 2.
EP79401064A 1978-12-29 1979-12-21 Radiological intensifier tube with video output and radiological network provided with such a tube Expired EP0013241B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7836957 1978-12-29
FR7836957A FR2445613A1 (en) 1978-12-29 1978-12-29 RADIOLOGICAL IMAGE INTENSIFIER TUBE AND RADIOLOGY CHAIN INCORPORATING SUCH A TUBE

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EP0013241A1 true EP0013241A1 (en) 1980-07-09
EP0013241B1 EP0013241B1 (en) 1982-05-05

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EP (1) EP0013241B1 (en)
DE (1) DE2962751D1 (en)
FR (1) FR2445613A1 (en)

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WO1993001612A1 (en) * 1991-07-11 1993-01-21 The University Of Connecticut Large area video camera

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DE3236155A1 (en) * 1982-09-29 1984-03-29 Siemens AG, 1000 Berlin und 8000 München X-RAY IMAGE CONVERTER
US4912737A (en) * 1987-10-30 1990-03-27 Hamamatsu Photonics K.K. X-ray image observing device
IL93969A (en) * 1990-04-01 1997-04-15 Yeda Res & Dev Ultrafast x-ray imaging detector
US5194726A (en) * 1991-06-17 1993-03-16 U.S. Philips Corp. X-ray imaging system with observable image during change of image size

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GB1102756A (en) * 1964-04-22 1968-02-07 Emi Ltd Improvements relating to electron discharge devices
FR2301916A1 (en) * 1975-02-18 1976-09-17 Philips Corp SEMICONDUCT TARGET

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WO1993001612A1 (en) * 1991-07-11 1993-01-21 The University Of Connecticut Large area video camera

Also Published As

Publication number Publication date
FR2445613A1 (en) 1980-07-25
EP0013241B1 (en) 1982-05-05
DE2962751D1 (en) 1982-06-24
US4346326A (en) 1982-08-24
FR2445613B1 (en) 1981-11-20

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