EP0142645B1 - X-ray diagnostic apparatus comprising an x-ray converter - Google Patents

X-ray diagnostic apparatus comprising an x-ray converter Download PDF

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Publication number
EP0142645B1
EP0142645B1 EP84110187A EP84110187A EP0142645B1 EP 0142645 B1 EP0142645 B1 EP 0142645B1 EP 84110187 A EP84110187 A EP 84110187A EP 84110187 A EP84110187 A EP 84110187A EP 0142645 B1 EP0142645 B1 EP 0142645B1
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Prior art keywords
fluorescent screen
ray
screen
image
input
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EP84110187A
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German (de)
French (fr)
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EP0142645A1 (en
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Jörg Haendle
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/64—Circuit arrangements for X-ray apparatus incorporating image intensifiers

Definitions

  • the invention relates to an x-ray diagnostic device with an x-ray converter with a luminescence storage luminescent screen, which stores the respective x-ray image latently and can be stimulated to light up by an additional radiation source, with a scanning device for the storage luminescent screen, optics arranged between the storage luminescent screen and a detector, and a television -Player.
  • a fluorescent screen is used in X-ray diagnostics to record and reproduce an X-ray image. It is known, for example, from US-A-3,975,637.
  • DE-A-2 928 244 describes an X-ray diagnostic device in which an X-ray image is first stored as a latent image in a plate with a storage fluorescent screen made of a phosphor that can be excited by visible light or infrared rays.
  • the defect electrons that are generated by the absorption of the X-rays in the phosphor layer of the phosphor screen are trapped in a potential trap of the phosphor, so that the radiation image remains stored.
  • the number of defects depends on the amount of the absorbing radiation energy. Only by scanning the fluorescent screen pixel by pixel, for example with an infrared laser beam, are these defect electrons lifted into the conductivity band and emit light in the visible range when they fall back.
  • the stored radiation image is made visible by the excitation with visible light or infrared rays, the electrons stored in the potential trap of the phosphor being released and thus the radiation image stored in the fluorescent screen being released in the form of fluorescent light.
  • the fluorescent light is captured by a photo detector and converted into an electrical signal, which is then visualized on a monitor.
  • US Pat. No. 3,975,637 describes an X-ray diagnostic device of the type mentioned at the outset, in which the radiation image contained in the storage luminescent screen is scanned pixel by pixel, with an optical system, a radiation collector, imaging the light beams emitted by the storage luminescent screen onto a detector will. After subsequent amplification of the electrical output signal from the detector, it is displayed on a reproduction device. In the case of dark image parts in the radiation image, the detector is only weakened to a small extent, so that its electrical noise can disturb these image signals.
  • FR-A-2 212 946 describes a method for generating an X-ray image in which the X-ray image contained in a storage phosphor is scanned by infrared rays.
  • the light emitted by the storage phosphor screen is fed to an image intensifier tube via an optical system, the output image of which is imaged on an X-ray image via a further optical system, so that the radiation image contained in the storage phosphor is recorded on the X-ray film.
  • the image intensifier tube with optics the light emanating from the storage fluorescent screen can also be detected by a detector, the output signal of which, after buffering, controls a cathode ray tube for recording on a microfilm. Losses or increased noise can also occur here due to the optics or the electrical transmission path.
  • the invention is based on the object of designing an X-ray diagnostic device of the type mentioned at the outset in such a way that the relative sensitivity is further increased and the output image of the luminescent screen is further enhanced, so that television images with high contrast and a low noise component are obtained.
  • an image intensifier is electronically optically coupled to an image intensifier unit with the luminescence storage fluorescent screen.
  • This coupled image intensifier immediately enhances the image visible through stimulating rays, so that losses, for example due to a subsequent optical coupling, do not have a disruptive effect.
  • the image intensifier unit has an input screen as a first carrier layer, on which an input phosphor screen is applied, on which a photocathode is vapor-deposited, and when an output phosphor screen is applied on a second carrier layer in the direction of the input thin conductive layer is covered.
  • the phosphor screen can be scanned from the input side if the input phosphor screen is made of storable luminescent material and the output phosphor screen of zinc sulfide or cadmium sulfide, and if the first carrier layer is transparent to light rays.
  • FIG. 1 shows a high-voltage generator 1 that feeds an X-ray tube 2 that emits X-rays that penetrate a patient 3.
  • the X-rays which have been weakened by the patient in accordance with its transparency, fall on an image intensifier unit 4, which consists, for example, of a fluorescent screen made of luminescent material and a coupled flat-screen amplifier with near-field focusing.
  • This striking radiation image generates defect electrons in the fluorescent screen of the image intensifier unit 4, which are stored in a potential trap of the phosphor, so that a latent image is stored in the fluorescent screen of the image intensifier unit 4.
  • the luminescent screen of the image intensifier unit 4 is scanned pixel by pixel by a laser beam, which is generated by a laser 5 and deflected by a deflection device 6 over the surface of the luminescent screen of the image intensifier unit 4.
  • the deflection device 6 for the laser 5 can consist, for example, of a deflection mirror for the vertical and an electro-optical beam deflector for the horizontal deflection.
  • An optical system 7 forms the output fluorescent screen of the image intensifier unit 4 on a detector 8, which detects the brightness of the scanned pixels and feeds it to a playback circuit 9, which generates a video signal for display on a monitor 10 from the individual, analog output signals of the detector 8.
  • the playback circuit 9 may include image memories, processing circuits and converters.
  • a control device 11 generates the control clocks for synchronizing the deflection device 6, the playback circuit 9 and the monitor 10.
  • this image intensifier unit 4 consists of a first carrier layer 12 on the input side facing the X-ray tube 2, on which an input fluorescent screen 13 is applied.
  • a photocathode 14, which is connected to the one pole of a voltage source 15, is evaporated on the input fluorescent screen 13.
  • a vacuum 16 follows, which can be, for example, twelve millimeters thick as the acceleration path.
  • the adjoining output screen of the image intensifier unit 4, which faces the detector 8, consists of a second carrier layer 19, on which an output fluorescent screen 18 is applied.
  • a thin conductive layer 17, to which the second pole of the voltage source 15 is connected, is applied from the exit fluorescent screen 18 to delimit it from the vacuum 16.
  • the image intensifier unit 4 can have two versions.
  • the input fluorescent screen 13 consists of luminescent material and the output fluorescent screen 18 consists of zinc sulfide or cadmium sulfide.
  • the carrier layers 12 and 19 can consist of glass, the carrier layer 12 having to be transparent to infrared rays, for example when using an infrared laser.
  • the photocathode 14 can for example consist of an antimony-cesium compound and the layer 17 made of aluminum. If the x-ray image is now imaged on the input fluorescent screen 13 in this arrangement, defect electrons are generated in accordance with the energy of the individual pixels and are stored in potential traps of the phosphor.
  • the defect electrons are released which are caused by the acceleration voltage applied to the photocathode 14 of e.g. more than 5 kV can be accelerated to the output luminescent screen 18, which is covered by the thin layer 17.
  • a brightness-enhanced image (factor 50 to 100) is thus emitted on the exit fluorescent screen 18.
  • the light generated in the exit fluorescent screen 18 is imaged on the photodetector 8 via the optics 7 by the final glass carrier.
  • the input luminescent screen 13 consists of casium iodide and the output luminescent screen 18 consists of thermoluminescent material.
  • the first carrier layer 12 can, as is customary in image intensifier technology, consist of aluminum, while the second carrier layer must be transparent to infrared rays and visible radiation. In this case, it can also consist of infrared-permeable glass.
  • the incident X-ray radiation produces 13 photoelectrons in the input fluorescent screen, which are accelerated in the vacuum 16, fall on the output fluorescent screen 18 and generate defect electrons. There they are saved again in the traps.
  • This arrangement according to the invention ensures that the detector 8 is still sufficiently controlled, even with low image dose values, so that the noise of the detector is negligible.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Radiography Using Non-Light Waves (AREA)
  • X-Ray Techniques (AREA)

Description

Röntgendiagnostikeinrichtung mit einem RöntgenkonverterX-ray diagnostic device with an X-ray converter

Die Erfindung betrifft eine Röntgendiagnostikeinrichtung mit einem Röntgenkonverter mit Lumineszenz-Speicherleuchtschirm, der das jeweilige Röntgenstrahlenbild latent speichert und zur Bildwiedergabe durch eine zusätzliche Strahlenquelle zum Leuchten anregbar ist, mit einer Abtastvorrichtung für den Speicherleuchtschirm, einer zwischen dem Speicherleuchtschirm und einem Detektor angeordneten Optik und einer Fernseh-Wiedergabevorrichtung. Ein derartiger Leuchtschirm dient in der Röntgendiagnostik der Aufzeichnung und Wiedergabe eines Röntgenstrahlenbildes. Er ist beispielsweise aus der US-A-3 975 637 bekannt.The invention relates to an x-ray diagnostic device with an x-ray converter with a luminescence storage luminescent screen, which stores the respective x-ray image latently and can be stimulated to light up by an additional radiation source, with a scanning device for the storage luminescent screen, optics arranged between the storage luminescent screen and a detector, and a television -Player. Such a fluorescent screen is used in X-ray diagnostics to record and reproduce an X-ray image. It is known, for example, from US-A-3,975,637.

In der DE-A-2 928 244 ist eine Röntgendiagnostikeinrichtung beschrieben, bei der ein Röntgenstrahlenbild in einer Platte mit einem Speicherleuchtschirm aus einem durch sichtbares Licht oder Infrarotstrahlen anregbarem Leuchtstoff zunächst als latentes Bild gespeichert wird. Die Defektelektronen, die durch die Absorption der Röntgenstrahlen in der Leuchtstoffschicht das Leuchtschirmes erzeugt werden, werden in einer Potentialfalle des Leuchtstoffes, in Traps, festgehalten, so dass das Strahlenbild gespeichert bleibt. Die Anzahl der Defektelektronen hängt von dem Betrag der absorbierenden Bestrahlungsenergie ab. Erst durch eine bildpunktweise Abtastung des Leuchtschirmes, beispielsweise mit einem Infrarot-Laserstrahl, werden diese Defektelektronen ins Leitfähigkeitsband gehoben und geben beim Rückfallen Licht im sichtbaren Bereich ab. Durch die Anregung mit sichbarem Licht oder Infrarotstrahlen wird das gespeicherte Bestrahlungsbild sichtbar gemacht, wobei die in der Potentialfalle des Leuchtstoffes gespeicherten Elektronen freigegeben werden und somit das in dem Leuchtschirm gespeicherte Bestrahlungsbild in Form von Fluoreszenzlicht freigesetzt wird. Durch einen Fotodetektor wird das Fluoreszenzlicht aufgefangen und in ein elektrisches Signal umgewandelt, das anschliessend auf einem Monitor sichtbar gemacht wird.DE-A-2 928 244 describes an X-ray diagnostic device in which an X-ray image is first stored as a latent image in a plate with a storage fluorescent screen made of a phosphor that can be excited by visible light or infrared rays. The defect electrons that are generated by the absorption of the X-rays in the phosphor layer of the phosphor screen are trapped in a potential trap of the phosphor, so that the radiation image remains stored. The number of defects depends on the amount of the absorbing radiation energy. Only by scanning the fluorescent screen pixel by pixel, for example with an infrared laser beam, are these defect electrons lifted into the conductivity band and emit light in the visible range when they fall back. The stored radiation image is made visible by the excitation with visible light or infrared rays, the electrons stored in the potential trap of the phosphor being released and thus the radiation image stored in the fluorescent screen being released in the form of fluorescent light. The fluorescent light is captured by a photo detector and converted into an electrical signal, which is then visualized on a monitor.

In der DE-A-2 928 244 ist darauf hingewiesen, dass die bisher bekannten Leuchtschirme eine zu geringe Empfindlichkeit aufweisen. Durch Wahl des Leuchtstoffes kann zwar die relative Empfindlichkeit erhöht werden. Diese reicht aber in vielen Fällen immer nocht nicht aus, Röntgenbilder mit ausreichender Helligkeit zu erzeugen, da beispielsweise eine optische Kopplung des Leuchtschirmes an dem Detektor weitere Verluste ergibt, so dass der Rauschanteil des Detektors nicht vernachlässigbar ist.In DE-A-2 928 244 it is pointed out that the previously known fluorescent screens are too insensitive. The relative sensitivity can be increased by choosing the phosphor. In many cases, however, this is still not sufficient to generate X-ray images with sufficient brightness, since, for example, optically coupling the fluorescent screen to the detector results in further losses, so that the noise component of the detector is not negligible.

In der US-A-3 975 637 ist eine Röntgendiagnostikeinrichtung der eingangs genannten Art beschrieben, bei der das im Speicherleuchtschirm enthaltene Strahlenbild durch einen Laser bildpunktweise abgetastet wird, wobei durch eine Optik, einen Strahlenkollektor, die von dem Speicherleuchtschirm emittierten Lichtstrahlen auf einen Detektor abgebildet werden. Nach anschliessender Verstärkung des elektrischen Ausgangssignales des Detektors wird dieses auf einer Wiedergabevorrichtung dargestellt. Bei dunklen Bildteilen im Strahlenbild wird, weiterhin durch die Optik geschwächt, der Detektor nur in geringem Masse ausgesteuert, so dass sein elektrisches Rauschen diese Bildsignale stören kann.US Pat. No. 3,975,637 describes an X-ray diagnostic device of the type mentioned at the outset, in which the radiation image contained in the storage luminescent screen is scanned pixel by pixel, with an optical system, a radiation collector, imaging the light beams emitted by the storage luminescent screen onto a detector will. After subsequent amplification of the electrical output signal from the detector, it is displayed on a reproduction device. In the case of dark image parts in the radiation image, the detector is only weakened to a small extent, so that its electrical noise can disturb these image signals.

in der FR-A-2 212 946 ist ein Verfahren zum Erzeugen eines Röntgenbildes beschrieben, bei dem das in einem Speicherleuchtstoff enthaltene Röntgenstrahlenbild durch Infrarotstrahlen abgetastet wird. Über eine Optik wird das von dem Speicherleuchtschirm emittierte Licht einer Bildverstärkerröhre zugeführt, deren Ausgangsbild über eine weitere Optik auf einem Röntgenbild abgebildet wird, so dass auf dem Röntgenfilm das in dem Speicherleuchtstoff enthaltene Strahlenbild aufgezeichnet wird. Anstelle der Bildverstärkerröhre mit Optiken kann das vom Speicherleuchtschirm ausgehende Licht auch von einem Detektor erfasst werden, dessen Ausgangssignal nach Zwischenspeicherung eine Kathodenstrahlröhre zur Aufzeichnung auf einen Mikrofilm ansteuert. Auch hier können durch die Optik bzw. den elektrischen Übertragungsweg Verluste bzw. erhöhtes Rauschen auftreten.FR-A-2 212 946 describes a method for generating an X-ray image in which the X-ray image contained in a storage phosphor is scanned by infrared rays. The light emitted by the storage phosphor screen is fed to an image intensifier tube via an optical system, the output image of which is imaged on an X-ray image via a further optical system, so that the radiation image contained in the storage phosphor is recorded on the X-ray film. Instead of the image intensifier tube with optics, the light emanating from the storage fluorescent screen can also be detected by a detector, the output signal of which, after buffering, controls a cathode ray tube for recording on a microfilm. Losses or increased noise can also occur here due to the optics or the electrical transmission path.

Die Erfindung geht von der Aufgabe aus, eine Röntgendiagnostikeinrichtung der eingangs genannten Art derart auszubilden, dass die relative Empfindlichkeit weiter erhöht und das Ausgangsbild des Leuchtschirmes weiter verstärkt werden, so dass Fernsehbilder mit hohem Kontrast und geringem Rauschanteil erhalten werden.The invention is based on the object of designing an X-ray diagnostic device of the type mentioned at the outset in such a way that the relative sensitivity is further increased and the output image of the luminescent screen is further enhanced, so that television images with high contrast and a low noise component are obtained.

Die Aufgabe wird erfindungsgemäss dadurch gelöst, dass mit dem Lumineszenz-Speicherleuchtschirm ein Bildverstärker elektronenoptisch zu einer Bildverstärkereinheit gekoppelt ist. Durch diesen angekoppelten Bildverstärker wird das durch anregende Strahlen sichtbare Bild sofort weiter verstärkt, so dass Verluste beispielsweise durch eine eventuell nachfolgende optische Kopplung nicht störend wirken.According to the invention, the object is achieved in that an image intensifier is electronically optically coupled to an image intensifier unit with the luminescence storage fluorescent screen. This coupled image intensifier immediately enhances the image visible through stimulating rays, so that losses, for example due to a subsequent optical coupling, do not have a disruptive effect.

Die Abmessungen können relativ klein gehalten werden, wenn der Bildverstärker ein Flachbildverstärker mit Nahfeld-Fokussierung ist. Ein besonders einfacher Aufbau ergibt sich sich wenn die Bildverstärkereinheit als Eingangsschirm eine erste Trägerschicht aufweist, auf der ein Eingangsleuchtschirm aufgetragen ist, auf dem eine Fotokathode aufgedampft ist, und wenn auf einer zweiten Trägerschicht in Richtung auf den Eingang ein Ausgangsleuchtschirm aufgetragen ist, der von einer dünnen leitenden Schicht abgedeckt ist. Der Leuchtschirm lässt sich von der Eingangsseite abtasten, wenn der Eingangsleuchtschirm aus speicherfähigem lumineszentem Material und der Ausgangsleuchtschirm aus Zinksulfid oder Cadmiumsulfid besteht, und wenn die erste Trägerschicht für Lichtstrahlen durchlässig ist. Eine vorteilhafte Variante ergibt sich, wenn die Abtastung auf der Ausgangsseite der Bildverstärkereinheit erfolgt, wenn der Eingangsleuchtschirm aus Cäsiumjodid und der Ausgangsleuchtschirm aus speicherfähigem lumineszentem Material besteht und wenn die zweite Trägerschicht für Lichtstrahlen durchlässig ist.The dimensions can be kept relatively small if the image intensifier is a flat-panel amplifier with near-field focusing. A particularly simple construction results when the image intensifier unit has an input screen as a first carrier layer, on which an input phosphor screen is applied, on which a photocathode is vapor-deposited, and when an output phosphor screen is applied on a second carrier layer in the direction of the input thin conductive layer is covered. The phosphor screen can be scanned from the input side if the input phosphor screen is made of storable luminescent material and the output phosphor screen of zinc sulfide or cadmium sulfide, and if the first carrier layer is transparent to light rays. An advantageous variant results if the scanning takes place on the output side of the image intensifier unit, if the input fluorescent screen made of cesium iodide and the output fluorescent screen made of storable luminescent material Material exists and when the second carrier layer is transparent to light rays.

Die Erfindung wird nachfolgend anhand eines in den Figuren dargestellten Ausführungsbeispieles näher erläutert. Es zeigen:

  • Fig. 1 den Aufnahmeteil einer erfindungsgemässen Röntgendiagnostikeinrichtung,
  • Fig. 2 den Wiedergabeteil einer erfindungsgemässen Röntgendiagnostikeinrichtung, und
  • Fig. 3 schematisch den Schichtaufbau der in den Figuren 1 und 2 dargestellten Bildverstärkereinheit.
The invention is explained in more detail below with reference to an embodiment shown in the figures. Show it:
  • 1 shows the recording part of an X-ray diagnostic device according to the invention,
  • 2 shows the reproducing part of an X-ray diagnostic device according to the invention, and
  • Fig. 3 shows schematically the layer structure of the image intensifier unit shown in Figures 1 and 2.

In der Figur 1 ist ein Hochspannungsgenerator 1 dargestellt, der eine Röntgenröhre 2 speist, die Röntgenstrahlen aussendet, die einen Patienten 3 durchdringen. Auf eine Bildverstärkereinheit 4, die beispielsweise aus einem Leuchtschirm aus Lumineszenz-Material und einem angekoppelten Flachbildverstärker mit Nahfeld-Fokussierung besteht, fallen die Röntgenstrahlen, die durch den Patienten entsprechend seiner Transparenz geschwächt wurden. Dieses auffallende Strahlenbild erzeugt in dem Leuchtschirm der Bildverstärkereinheit 4 Defektelektronen, die in einer Potentialfalle des Leuchtstoffes gespeichert werden, so dass in dem Leuchtschirm der Bildverstärkereinheit 4 ein latentes Bild gespeichert ist.FIG. 1 shows a high-voltage generator 1 that feeds an X-ray tube 2 that emits X-rays that penetrate a patient 3. The X-rays, which have been weakened by the patient in accordance with its transparency, fall on an image intensifier unit 4, which consists, for example, of a fluorescent screen made of luminescent material and a coupled flat-screen amplifier with near-field focusing. This striking radiation image generates defect electrons in the fluorescent screen of the image intensifier unit 4, which are stored in a potential trap of the phosphor, so that a latent image is stored in the fluorescent screen of the image intensifier unit 4.

Zur Wiedergabe des latenten Bildes wird der Leuchtschirm der Bildverstärkereinheit 4 von einem Laserstrahl bildpunktweise abgetastet, der von einem Laser 5 erzeugt und von einer Ablenkvorrichtung 6 über die Fläche des Leuchtschirmes der Bildverstärkereinheit 4 abgelenkt wird. Die Ablenkvorrichtung 6 für den Laser 5 kann beispielsweise aus einem Ablenkspiegel für die vertikale und einem elektro-optischen Strahlenablenker für die horizontale Ablenkung bestehen-Durch die Abtastung mit dem Laserstrahl werden alle auf dem Leuchtschirm liegenden Bildpunkte nacheinander angeregt und zum Leuchten gebracht. Eine Optik 7 bildet den Ausgangsleuchtschirm der Bildverstärkereinheit 4 auf einem Detektor 8 ab, der die Helligkeit der abgestasteten Bildpunkte erfasst und einer Wiedergabeschaltung 9 zuführt, die aus den einzelnen, analogen Ausgangssignalen des Detektors 8 ein Videosignal zur Darstellung auf einem Monitor 10 erzeugt. Die Wiedergabeschaltung 9 kann Bildspeicher, Verarbeitungsschaltungen und Wandler enthalten. Eine Steuereinrichtung 11 erzeugt die Steuertakte zur Synchronisation der Ablenkvorrichtung 6, der Wiedergabeschaltung 9 und des Monitors 10.To display the latent image, the luminescent screen of the image intensifier unit 4 is scanned pixel by pixel by a laser beam, which is generated by a laser 5 and deflected by a deflection device 6 over the surface of the luminescent screen of the image intensifier unit 4. The deflection device 6 for the laser 5 can consist, for example, of a deflection mirror for the vertical and an electro-optical beam deflector for the horizontal deflection. By scanning with the laser beam, all the pixels on the fluorescent screen are excited one after the other and made to glow. An optical system 7 forms the output fluorescent screen of the image intensifier unit 4 on a detector 8, which detects the brightness of the scanned pixels and feeds it to a playback circuit 9, which generates a video signal for display on a monitor 10 from the individual, analog output signals of the detector 8. The playback circuit 9 may include image memories, processing circuits and converters. A control device 11 generates the control clocks for synchronizing the deflection device 6, the playback circuit 9 and the monitor 10.

Anhand der Figur 3, in der der Schichtaufbau der Bildverstärkereinheit 4 dargestellt ist, wird die Funktionsweise dieser Bildverstärkereinheit 4 näher erläutert. Sie besteht auf der der Röntgenröhre 2 zugewandten Eingangsseite aus einer ersten Trägerschicht 12, auf der ein Eingangsleuchtschirm 13 aufgetragen ist. Auf dem Eingangsleuchtschirm 13 ist eine Fotokathode 14 aufgedampft, die mit dem einen Pol einer Spannungsquelle 15 verbunden ist. Nach dem Eingangsschirm 12 bis 14 folgt als Beschleunigungsstrecke ein Vakuum 16, das beispielsweise zwölf Millimeter dick sein kann. Der daran anschliessende Ausgangschirm der Bildverstärkereinheit 4, der dem Detektor 8 zugewandt ist, besteht aus einer zweiten Trägerschicht 19, auf der ein Ausgangsleuchtschirm 18 aufgetragen ist. Aus dem Ausgangsleuchtschirm 18 ist zur Abgrenzung an das Vakuum 16 eine dünne leitende Schicht 17 aufgetragen, an der der zweite Pol der Spannungsquelle 15 angeschlossen ist.The mode of operation of this image intensifier unit 4 is explained in more detail with reference to FIG. 3, in which the layer structure of the image intensifier unit 4 is shown. It consists of a first carrier layer 12 on the input side facing the X-ray tube 2, on which an input fluorescent screen 13 is applied. A photocathode 14, which is connected to the one pole of a voltage source 15, is evaporated on the input fluorescent screen 13. After the input screen 12 to 14, a vacuum 16 follows, which can be, for example, twelve millimeters thick as the acceleration path. The adjoining output screen of the image intensifier unit 4, which faces the detector 8, consists of a second carrier layer 19, on which an output fluorescent screen 18 is applied. A thin conductive layer 17, to which the second pole of the voltage source 15 is connected, is applied from the exit fluorescent screen 18 to delimit it from the vacuum 16.

Die Bildverstärkereinheit 4 kann zwei Ausführungen aufweisen. Bei der ersten besteht der Eingangsleuchtschirm 13 aus Lumineszenz-Material und der Ausgangsleuchtschirm 18 aus Zinksulfid oder Cadmiumsulfid. Die Trägerschichten 12 und 19 können hierbei aus Glas bestehen, wobei die Trägerschicht 12 bei Verwendung eines Infrarotlasers beispielsweise für Infrarotstrahlen durchlässig sein muss. Die Fotokathode 14 kann beispielsweise aus einer Antimon-Cäsium-Verbindung und die Schicht 17 aus Aluminium bestehen. Wird nun bei dieser Anordnung das Röntgenstrahlenbild auf dem Eingangsleuchtschirm 13 abgebildet, so werden entsprechend der Energie der einzelnen Bildpunkte Defektelektronen erzeugt, die in Potentialfallen des Leuchtstoffes gespeichert werden. Wird nun anschliessend von der Eingangsseite der Eingangsleuchtschirm 13 durch einen durch den Laser 5 erzeugten Infrarot-Laserstrahl bildpunktweise abgetastet, so werden die Defektelektronen freigesetzt, die durch die an der Fotokathode 14 angelegte Beschleunigungsspannung von z.B. mehr als 5 kV auf den Ausgangsleuchtschirm 18 beschleunigt werden, der von der dünnen Schicht 17 abgedeckt ist. Auf dem Ausganqsnleuchtschirm 18 wird somit ein helligkeitsverstärktes Bild (Faktor 50 bis 100) abgegeben. Durch den abschliessenden Glasträger wird das in dem Ausgangsleuchtschirm 18 erzeugte Licht über die Optik 7 auf dem Fotodetektor 8 abgebildet.The image intensifier unit 4 can have two versions. In the first case, the input fluorescent screen 13 consists of luminescent material and the output fluorescent screen 18 consists of zinc sulfide or cadmium sulfide. The carrier layers 12 and 19 can consist of glass, the carrier layer 12 having to be transparent to infrared rays, for example when using an infrared laser. The photocathode 14 can for example consist of an antimony-cesium compound and the layer 17 made of aluminum. If the x-ray image is now imaged on the input fluorescent screen 13 in this arrangement, defect electrons are generated in accordance with the energy of the individual pixels and are stored in potential traps of the phosphor. If the input luminescent screen 13 is then scanned pixel by pixel from the input side by an infrared laser beam generated by the laser 5, the defect electrons are released which are caused by the acceleration voltage applied to the photocathode 14 of e.g. more than 5 kV can be accelerated to the output luminescent screen 18, which is covered by the thin layer 17. A brightness-enhanced image (factor 50 to 100) is thus emitted on the exit fluorescent screen 18. The light generated in the exit fluorescent screen 18 is imaged on the photodetector 8 via the optics 7 by the final glass carrier.

In einem zweiten möglichen Aufbau der Bildverstärkereinheit 4 besteht der Eingangsleuchtschirm 13 aus Casiumjodid und der Ausgangsleuchtschirm 18 aus Thermolumineszenz-Material. Die erste Trägerschicht 12 kann, wie in der Bildverstärkertechnik üblich, aus Aluminium bestehen, während die zweite Trägerschicht für Infrarotstrahlen und sichtbare Strahlung durchlässig sein muss. Sie kann in diesem Falle auch aus infrarotdurchlässigem Glas bestehen. Durch die auffallende Röntgenstrahlung werden in dem Eingangsleuchtschirm 13 Fotoelektronen erzeugt, die in dem Vakuum 16 beschleunigt werden, auf den Ausgangsleuchtschirm 18 fallen und Defektelektronen erzeugen. Dort werden sie wieder in den Traps gespeichert. Anschliessend können sie von der Ausgangsseite her durch den Infrarot-Laserstrahl abgetastet werden, wobei bildpunktweise wiederum ein sichtbares Bild ensteht, das auf dem Detektor 8 abgebildet wird. Durch diese Anregung des Ausgangsleuchtschirmes 18 können additive Schirmstörstrukturen besser unterdrückt werden. Bei dieser Ausführungsform muss aber darauf geachtet werden, dass die Sättigungsgrenze des Lumineszenz-Materials nicht überschritten wird.In a second possible construction of the image intensifier unit 4, the input luminescent screen 13 consists of casium iodide and the output luminescent screen 18 consists of thermoluminescent material. The first carrier layer 12 can, as is customary in image intensifier technology, consist of aluminum, while the second carrier layer must be transparent to infrared rays and visible radiation. In this case, it can also consist of infrared-permeable glass. The incident X-ray radiation produces 13 photoelectrons in the input fluorescent screen, which are accelerated in the vacuum 16, fall on the output fluorescent screen 18 and generate defect electrons. There they are saved again in the traps. They can then be scanned from the output side by the infrared laser beam, a pixel-by-pixel image being generated which is imaged on the detector 8. This excitation of the output fluorescent screen 18 can be used to better suppress additive screen interference structures. In this embodiment, however, care must be taken that the saturation limit of the luminescent material is not exceeded.

Durch diese erfindungsgemässe Anordnung wird erreicht, das selbst bei geringen Bilddosiswerten der Detektor 8 noch genügend ausgesteuert wird, so dass das Rauschen des Detektors vernachlässigbar ist.This arrangement according to the invention ensures that the detector 8 is still sufficiently controlled, even with low image dose values, so that the noise of the detector is negligible.

Claims (5)

1. X-ray diagnostic equipment having an X-ray converter with a luminescence storage fluorescent screen (13) of the type which stores in a latent manner each X-ray beam image and which can be excited for the purpose of image reproduction by means of a radiation source (5) for illumination, a scanning device (5, 6) for the storage fluorescent screen (13), an optical system (7) arranged between the storage fluorescent screen (13) and a detector (8), and a visual display reproduction device (9, 10), characterised in that an image intensifier is coupled electro optically with the luminescence storage fluorescent screen (13) to form an image intensifier unit (4).
2. X-ray diagnostic equipment according to claim 1, characterised in that the image intensifier is a flat image intensifier with near filed focusing.
3. X-ray diagnostic equipment according to claim 1 or 2, characterised in that the image intensifier unit (4) has as an input screen (12 to 14) a first carrier layer (12) on which there is applied an input fluorescent screen (13) on which there is evaporated a photocathode (14), and in that an output fluorescent screen (18) covered by a thin conductive layer (17) is applied to a second carrier layer (19) in the direction of the input.
4. X-ray diagnostic equipment according to claim 3, characterised in that the input fluorescent screen (13) is made of luminescent material having a storing capability and the output fluorescent screen (18) is made of zinc sulphide or cadmium sulphide and in that the first carrier layer (12) is light permeable.
5. X-ray diagnostic equipment according to claim 3, characterised in that the input fluorescent screen (13) is made of caesium iodide and the output fluorescent screen (18) is made of luminescent material having a storing capability and in that the second carrier layer (19) is light permeable.
EP84110187A 1983-09-09 1984-08-27 X-ray diagnostic apparatus comprising an x-ray converter Expired EP0142645B1 (en)

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DE3332648 1983-09-09
DE19833332648 DE3332648A1 (en) 1983-09-09 1983-09-09 X-RAY DIAGNOSTIC DEVICE WITH A X-RAY CONVERTER

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EP0142645A1 EP0142645A1 (en) 1985-05-29
EP0142645B1 true EP0142645B1 (en) 1988-06-22

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DE3472352D1 (en) 1988-07-28
JPS6068543U (en) 1985-05-15
EP0142645A1 (en) 1985-05-29
DE3332648A1 (en) 1985-03-28
US4886970A (en) 1989-12-12

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