EP1266391B1 - Radiation converter comprising a scintillator, a photocathode and an electron multiplier - Google Patents

Radiation converter comprising a scintillator, a photocathode and an electron multiplier Download PDF

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Publication number
EP1266391B1
EP1266391B1 EP01935937A EP01935937A EP1266391B1 EP 1266391 B1 EP1266391 B1 EP 1266391B1 EP 01935937 A EP01935937 A EP 01935937A EP 01935937 A EP01935937 A EP 01935937A EP 1266391 B1 EP1266391 B1 EP 1266391B1
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EP
European Patent Office
Prior art keywords
radiation
photocathode
converter according
radiation converter
case
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EP01935937A
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German (de)
French (fr)
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EP1266391A2 (en
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Manfred Fuchs
Erich Hell
Wolfgang KNÜPFER
Detlef Mattern
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Siemens AG
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Siemens AG
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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
    • H01J2231/00—Cathode ray tubes or electron beam tubes
    • H01J2231/50—Imaging and conversion tubes
    • H01J2231/50005—Imaging and conversion tubes characterised by form of illumination
    • H01J2231/5001—Photons
    • H01J2231/50031—High energy photons
    • H01J2231/50036—X-rays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2231/00—Cathode ray tubes or electron beam tubes
    • H01J2231/50—Imaging and conversion tubes
    • H01J2231/50057—Imaging and conversion tubes characterised by form of output stage
    • H01J2231/50068—Electrical
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2231/00—Cathode ray tubes or electron beam tubes
    • H01J2231/50—Imaging and conversion tubes
    • H01J2231/501—Imaging and conversion tubes including multiplication stage

Definitions

  • the invention relates to an X-radiation incident with a radiation absorber for generating photons as a function of the intensity.
  • image intensifier radiation converter From the DE 33 32 648 A1 a known as image intensifier radiation converter is known.
  • image intensifiers have an input window with a radiation absorber for generating light photons depending on the radiation intensity incident radiation.
  • the beam absorber is followed by a photocathode, which generates electrons as a function of the light photons emitted by the radiation absorber.
  • These electrons are accelerated by an electrode system onto an electron receiver.
  • this electron receiver In the case of the image intensifier, this electron receiver is designed as an output screen which generates light photons on account of the incident electrons.
  • An X-ray detector is known in which the photocathode is applied to a radiation absorber.
  • the photocathode is disposed at a distance opposite to an amorphous selenium layer of an output screen.
  • Another detector device is out of the DE 44 29 925 C1 known.
  • a shadow mask made of wires is provided on the radiation input side, which is connected downstream of a chevron plate.
  • a low-resistance anode structure is provided outside the detector on its rear side. From the EP 0 053 530 a photodetector is known, in which in the radiation direction of a photocathode, an electron multiplier and a detector anode are connected downstream.
  • a radiation converter is known with a radiation absorber for generating photons in response to the intensity of incident X-ray radiation to enable the display of X-ray images with a photocathode for generating electrons in dependence from the photons emitted by the beam absorber, with means for accelerating the electrons emitted from the photocathode, with an electron multiplier for multiplying electrons, and with an electron detector for generating electrical signals in response to the incident electrons.
  • the radiation exposure is to be kept as small as technically feasible to minimize the radiation exposure of the patient, the efficient use of the patient and penetrating the radiation receiver incident radiation top priority.
  • the lower the radiation intensity impinging on the radiation receiver the lower the signals which can be derived from the radiation receiver.
  • the distance between the signal levels and the noise signals also decreases, which is accompanied by a poorer diagnosability of the visual representations that can be generated on the basis of these signals. So it is a compromise between a low radiation exposure of the patient and to close the necessary for a good diagnosability of producible radiographic images of the patient radiation dose.
  • the photographic film for example, is nothing more than a chemical amplifier that amplifies the ionization processes of the radiation in the microscopic range by many orders of magnitude and makes them visible in the macroscopic range.
  • Storage phosphor plates store the radiation shadow of an object latently. By scanning the storage phosphor plate by means of a light beam light photons are generated due to the latent image, which are converted by a readout with a photomultiplier into electrons, which can be amplified almost noiseless up to a factor of 10 6 and converted into electrical signals. This electrical Signals are then available for visual representation.
  • the geometric reduction which results from a large input window and a smaller output window, is used to increase the luminance, which is supported by the energy absorption of the electrons from the input screen to the output screen by a here intermediate acceleration field.
  • a radiation-to-light-emitting layer comprising CsI, for example, is brought into direct contact with a photodiode array of amorphous silicon, so that the light photons generated by the layer due to incident radiation can be converted into electrical signals via the photodiode array then be available for pictorial representation. Since there is no amplification of the light photons via electrons, only relatively small signals can be derived from the photodiode matrix, which can only be amplified in a downstream device, for example an amplifier.
  • the signals derived from the flat-panel detector are particularly low and are close to the noise region and thus require complex artifact corrections.
  • fluoroscopy for example, the signals of every other beam scanning are used for correction purposes, so that the usual image repetition rates can not be approached.
  • the dynamic one Range of signals derived from the flat panel detector is also severely limited.
  • the object of the invention is to provide a radiation converter which is as universally usable as possible. Another goal is to improve the dynamics of the radiation converter.
  • a gap is provided between the radiation absorber and the photocathode.
  • the dynamics of the proposed radiation converter is improved.
  • Another advantage is that the photocathode does not have to be made transparent due to the arrangement proposed here. It can thereby be achieved a cost savings.
  • the photocathode may expediently be made opaque. Avalanche UV photons can not reach the photocathode directly.
  • the photocathode is made of a metallic material which preferably contains gold, cesium, copper or antimony. It is further expedient that the photocathode is formed as a layer on the electron multiplier, wherein the electron multiplier can in turn be formed as a layer on the electron detector. According to a particularly advantageous embodiment, the electron multiplier has a perforated, preferably made of polyimide, plastic film. The diameter of the holes is about 25 microns.
  • a common, gas-tight housing is assigned, resulting in a compact design of the radiation converter.
  • a UV photon absorbing gas is received in the housing.
  • the gas may include at least one of argon, krypton, xenon, helium, neon, CO 2 , N 2 , hydrocarbon, di-methyl ether, methanol / ethanol vapor.
  • the radiation absorber converts radiation into light photons in particular advantageously if it has a needle-shaped structure and consists of CsI: Na.
  • the electron detector is designed as a 2D thin-film panel and consists of a-Se, a-Si: H or poly-Si.
  • Such an electron detector is simple in construction and inexpensive.
  • radiation converter is designated by the reference numeral 1, a housing.
  • the housing has a radiation absorber 2, which converts radiation into light photons.
  • the radiation absorber 2 is either designed as a separate part or arranged outside the housing 1 in the region of a first end face. It consists of a scintillator material, preferably of CsI: Na in needle structure, the needles being directed in the direction of a photocathode 3 are.
  • the photocathode 3 is arranged at a distance a of approximately 50 ⁇ m from the radiation absorber 2. It is designed as a layer, which is preferably made of copper, on a perforated polyimide film 4.
  • the polyimide film 4 acts as an electron multiplier. It is applied to an electron detector 5.
  • the electron detector 5 preferably has a pixel structure and converts the incident electrons into electrical signals which can be derived via suitable known measures, for example an electrical line, and on the basis of which a pictorial representation on a display device is possible.
  • the electron detector 5 is preferably designed as a 2D thin-film panel and may preferably consist of a-Se, a-Si: H or poly-Si.
  • a gas, in particular quenching gas for example, a mixture of argon and hydrocarbon, is added.
  • the function of the device is as follows:
  • X-rays are absorbed by the radiation absorber 2 and thereby converted into photons.
  • the photons release photoelectrons from the photocathode 3.
  • the photoelectrons reach the area of the perforated polyimide film 4.
  • a potential is applied between the photocathode 3 and the electron detector 5.
  • By the applied electric potential is achieved that all the photoelectrons are pulled from the surface of the photocathode 3 in the nearest holes.
  • charge ionization takes place by impact ionization.
  • the charge carrier multiplication or gain can be set by the level of the applied potential. Thus, the signal / noise ratio can be improved.
  • the photoelectrons are accelerated by the applied potential on the electron detector. The charges accumulated there are read out with a predetermined clock sequence.
  • the radiation absorber 2 may be provided with a UV-photon absorbing conductive layer.
  • the quench gas absorbs the UV photons generated by impact ionization so that they do not reach the photocathode 3, where they could unintentionally trigger photoelectrons.
  • Fig. 2 the modulation transfer function is plotted above the spatial frequency.
  • the curves MTF 1 and MTF 2 show the modulation transfer function at a distance of the photocathode 3 from the beam absorber 2 of 50 ⁇ m.
  • the curve MTF 2 shows the dot image function of an isotropic point source, the curve MTF 1 the aforementioned point image function for a Lambert source.
  • the curve MTF 3 shows the modulation transfer function, in which case the radiation absorber 2 is in direct contact with the electron detector 5.
  • the curve MTF 3 thus represents the characteristic of conventional flat-panel detectors.
  • the values MTF 4 indicate the modulation transfer function for a Lambert source, wherein the beam absorber 2 is arranged at a distance of 50 ⁇ m from the electron detector 5. It can be seen that the spaced array does not significantly change the modulation transfer function.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Measurement Of Radiation (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Description

Die Erfindung bezieht sich auf einen mit einem Strahlenabsorber zum Erzeugen von Photonen in Abhängigkeit von der Intensität auftreffender Röntgenstrahlung.The invention relates to an X-radiation incident with a radiation absorber for generating photons as a function of the intensity.

Aus der DE 33 32 648 A1 ist ein als Bildverstärker ausgeführter Strahlungswandler bekannt. Solche Bildverstärker weisen ein Eingangsfenster mit einem Strahlenabsorber zum Erzeugen von Lichtphotonen in Abhängigkeit von der Strahlenintensität auftreffender Strahlung auf. Dem Strahlenabsorber ist eine Photokathode nachgeordnet, die in Abhängigkeit von den von dem Strahlenabsorber ausgehenden Lichtphotonen Elektronen erzeugt. Diese Elektronen werden durch ein Elektrodensystem auf einen Elektronenempfänger beschleunigt. Beim Bildverstärker ist dieser Elektronenempfänger als Ausgangsschirm ausgeführt, der aufgrund der auftreffenden Elektronen Lichtphotonen erzeugt.From the DE 33 32 648 A1 a known as image intensifier radiation converter is known. Such image intensifiers have an input window with a radiation absorber for generating light photons depending on the radiation intensity incident radiation. The beam absorber is followed by a photocathode, which generates electrons as a function of the light photons emitted by the radiation absorber. These electrons are accelerated by an electrode system onto an electron receiver. In the case of the image intensifier, this electron receiver is designed as an output screen which generates light photons on account of the incident electrons.

Aus der US 5,369,268 ist ein Röntgendetektor bekannt, bei dem auf einem Strahlenabsorber die Photokathode aufgebracht ist. Die Photokathode ist mit einem Abstand gegenüberliegend angeordnet einer amorphen Selenschicht eines Ausgangsschirms.From the US 5,369,268 An X-ray detector is known in which the photocathode is applied to a radiation absorber. The photocathode is disposed at a distance opposite to an amorphous selenium layer of an output screen.

Eine weitere Detektoreinrichtung ist aus der DE 44 29 925 C1 bekannt. Dabei ist strahleneingangsseitig eine aus Drähten hergestellte Schattenmaske vorgesehen, welcher einer Chevron-Platte nachgeschaltet ist. Zur Erzeugung eines Bildsignals ist außerhalb des Detektors auf dessen Rückseite eine niederohmige Anodenstruktur vorgesehen. Aus der EP 0 053 530 ist ein Photodetektor bekannt, bei dem in Strahlungsrichtung einer Photokathode ein Elektronenvervielfacher und eine Detektoranode nachgeschaltet sind.Another detector device is out of the DE 44 29 925 C1 known. In this case, a shadow mask made of wires is provided on the radiation input side, which is connected downstream of a chevron plate. To generate an image signal, a low-resistance anode structure is provided outside the detector on its rear side. From the EP 0 053 530 a photodetector is known, in which in the radiation direction of a photocathode, an electron multiplier and a detector anode are connected downstream.

Aus der DE 42 37 097 A1 ist ein Strahlungswandler bekannt, mit einem Strahlenabsorber zum Erzeugen von Photonen in Abhängigkeit von der Intensität auftreffender Röntgenstrahlung, um die Wiedergabe von Röntgenbildern zu ermöglichen, mit einer Photokathode zum Erzeugen von Elektronen in Abhängigkeit von den vom Strahlenabsorber ausgehenden Photonen, mit einer Einrichtung zum Beschleunigen der von der Photokathode ausgehenden Elektronen, mit einem Elektronenvervielfacher zur Vervielfachung von Elektronen, und mit einem Elektronendetektor zum Erzeugen elektrischer Signale in Abhängigkeit von den auftreffenden Elektronen.From the DE 42 37 097 A1 For example, a radiation converter is known with a radiation absorber for generating photons in response to the intensity of incident X-ray radiation to enable the display of X-ray images with a photocathode for generating electrons in dependence from the photons emitted by the beam absorber, with means for accelerating the electrons emitted from the photocathode, with an electron multiplier for multiplying electrons, and with an electron detector for generating electrical signals in response to the incident electrons.

Da bei der medizinischen Untersuchung eines Patienten, im Unterschied zur zerstörungsfreien Werkstoffprüfung, die Strahlenbelastung so klein zu halten ist, wie dies technisch sinnvoll ist, um die Strahlenbelastung des Patienten möglichst gering zu halten, ist die effiziente Nutzung der den Patienten durchdringenden und auf den Strahlenempfänger auftreffenden Strahlung oberstes Gebot. Je geringer jedoch die auf den Strahlenempfänger auftreffende Strahlenintensität ist, um so geringer sind auch die vom Strahlenempfänger ableitbaren Signale. Der Abstand der Signalpegel zu den Rauschsignalen wird ebenfalls geringer, was mit einer schlechteren Diagnostizierbarkeit der aufgrund dieser Signale erzeugbaren bildlichen Darstellungen einher geht. Es ist also ein Kompromiß zwischen einer geringen Strahlenbelastung des Patienten und der für eine gute Diagnostizierbarkeit von erzeugbaren Durchstrahlungsbildern des Patienten notwendigen Strahlendosis zu schließen.As in the medical examination of a patient, unlike non-destructive material testing, the radiation exposure is to be kept as small as technically feasible to minimize the radiation exposure of the patient, the efficient use of the patient and penetrating the radiation receiver incident radiation top priority. However, the lower the radiation intensity impinging on the radiation receiver, the lower the signals which can be derived from the radiation receiver. The distance between the signal levels and the noise signals also decreases, which is accompanied by a poorer diagnosability of the visual representations that can be generated on the basis of these signals. So it is a compromise between a low radiation exposure of the patient and to close the necessary for a good diagnosability of producible radiographic images of the patient radiation dose.

Der fotografische Film ist beispielsweise nichts anderes als ein chemischer Verstärker, der die Ionisationsprozesse der Strahlung im mikroskopischen Bereich um viele Größenordnungen verstärkt und im makroskopischen Bereich sichtbar macht.The photographic film, for example, is nothing more than a chemical amplifier that amplifies the ionization processes of the radiation in the microscopic range by many orders of magnitude and makes them visible in the macroscopic range.

Speicherleuchtstoffplatten speichern das Strahlenschattenbild eines Objektes latent. Durch Abtastung der Speicherleuchtstoffplatte mittels eines Lichtstrahles werden aufgrund des latenten Bildes Lichtphotonen erzeugt, die von einer Auslese mit einem Photomultiplier in Elektronen gewandelt werden, die nahezu rauschfrei bis zu einem Faktor von 106 verstärkt und in elektrische Signale gewandelt werden können. Diese elektrischen Signale stehen dann für die bildliche Darstellung zur Verfügung.Storage phosphor plates store the radiation shadow of an object latently. By scanning the storage phosphor plate by means of a light beam light photons are generated due to the latent image, which are converted by a readout with a photomultiplier into electrons, which can be amplified almost noiseless up to a factor of 10 6 and converted into electrical signals. This electrical Signals are then available for visual representation.

Bei Röntgenbildverstärkern wird die geometrische Verkleinerung, die sich aufgrund eines großen Eingangsfensters und eines kleineren Ausgangsfensters ergibt, zur Verstärkung der Leuchtdichte herangezogen, wozu unterstützend die Energieaufnahme der Elektronen vom Eingangsleuchtschirm zum Ausgangsleuchtschirm durch ein hier zwischenliegendes Beschleunigungsfeld dient.In X-ray image intensifiers, the geometric reduction, which results from a large input window and a smaller output window, is used to increase the luminance, which is supported by the energy absorption of the electrons from the input screen to the output screen by a here intermediate acceleration field.

Bei den sogenannten Flachbilddetektoren wird eine Strahlung in Licht wandelnde Schicht, die beispielsweise CsI aufweist, in direkten Kontakt mit einer Photodiodenmatrix aus amorphem Silizium gebracht, so daß die von der Schicht aufgrund auftreffender Strahlung erzeugten Lichtphotonen über die Photodiodenmatrix in elektrische Signale gewandelt werden können, die dann für die bildliche Darstellung zur Verfügung stehen. Da keine Verstärkung der Lichtphotonen über Elektronen erfolgt, sind nur relativ kleine Signale von der Photodiodenmatrix ableitbar, die erst in einer nachgeschalteten Einrichtung, z.B. einem Verstärker, verstärkt werden können. Da die Ladungsmengen dieser relativ geringen elektrischen Signale dann auch noch über komplizierte Taktverfahren aus den zum Teil großflächigen Flachbilddetektoren über relativ lange Leitungen bis zu den Verstärkern geleitet werden müssen, ist das mittlere Rauschen, in Elektronen gemessen, fast doppelt so groß wie das Signal, das von einzelnen Röntgenquanten erzeugt wird. Insbesondere für die Fluoroskopie, bei der nur kleine Röntgendosen appliziert werden, sind die von dem Flachbilddetektor ableitbaren Signale besonders gering und liegen nahe des Bereiches des Rauschens und erfordern somit aufwendige Artefaktkorrekturen. Bei der Fluoroskopie werden beispielsweise die Signale jeder zweiten Strahlenabtastung zu Korrekturzwecken herangezogen, so daß die üblichen Bildwiederholraten nicht annähernd erreicht werden können. Der dynamische Bereich der von dem Flachbilddetektor ableitbaren Signale ist zudem stark eingeschränkt.In the so-called flat-panel detectors, a radiation-to-light-emitting layer comprising CsI, for example, is brought into direct contact with a photodiode array of amorphous silicon, so that the light photons generated by the layer due to incident radiation can be converted into electrical signals via the photodiode array then be available for pictorial representation. Since there is no amplification of the light photons via electrons, only relatively small signals can be derived from the photodiode matrix, which can only be amplified in a downstream device, for example an amplifier. Since the charge quantities of these relatively small electrical signals then also over complicated clocking procedures from the partially large-area flat panel detectors over relatively long lines must be routed to the amplifiers, the average noise, measured in electrons, almost twice as large as the signal, the is generated by individual X-ray quanta. In particular, for fluoroscopy, in which only small X-ray doses are applied, the signals derived from the flat-panel detector are particularly low and are close to the noise region and thus require complex artifact corrections. In fluoroscopy, for example, the signals of every other beam scanning are used for correction purposes, so that the usual image repetition rates can not be approached. The dynamic one Range of signals derived from the flat panel detector is also severely limited.

Bei den heutigen Flachbilddetektoren werden als Elektronendetektoren vorwiegend a-Si:H Ausleseplatten benutzt. Ein Betrieb solcher Flachbilddetektoren in verschiedenen Betriebsarten, wie Fluoroskopie und Radiographie, die sich um Dosisfaktoren von 100 - 1000 unterscheiden, erfordert einen hohen Rechenaufwand. Beim Übergang der mit einer hohen Dosis betriebenen Betriebsart Radiographie zur mit niedriger Dosis betriebenen Betriebsart Fluoroskopie müssen Restbilder in der a-Si:H Ausleseplatte durch Subtraktion rechnerisch entfernt werden.In today's flat panel detectors are used as electron detectors mainly a-Si: H readout plates. Operation of such flat panel detectors in various modes of operation, such as fluoroscopy and radiography, which differ by dose factors of 100-1000, requires a great deal of computational effort. When transitioning from the high-dose mode Radiography to the low-dose fluoroscopy mode, residual images in the a-Si: H read-out plate must be mathematically removed by subtraction.

Aufgabe der Erfindung ist es, einen möglichst universell verwendbaren Strahlungswandler anzugeben. Weiteres Ziel ist es, die Dynamik des Strahlungswandlers zu verbessern.The object of the invention is to provide a radiation converter which is as universally usable as possible. Another goal is to improve the dynamics of the radiation converter.

Diese Aufgabe wird durch die Merkmale des Patentanspruchs 1 gelöst. Zweckmäßige Ausgestaltungen der Erfindung ergeben sich aus den Merkmalen der Patentansprüche 2 - 12.This object is solved by the features of patent claim 1. Advantageous embodiments of the invention will become apparent from the features of claims 2-12.

Beim erfindungsgemäßen Strahlungswandler ist zwischen dem Strahlenabsorber und der Photokathode ein Abstand vorgesehen. Dadurch kann die die Messung nachteilig beeinflussende Wirkung von UV-Photonen reduziert werden. Die Dynamik des vorgeschlagenen Strahlungswandlers ist verbessert. Ein weiterer Vorteil besteht darin, daß die Photokathode in Folge der hier vorgeschlagenen Anordnung nicht mehr transparent ausgeführt sein muß. Es kann dadurch eine Kostenersparnis erzielt werden. Dabei beträgt der Abstand zwischen 10 und 100µm. Als besonders vorteilhaft hat sich ein Abstand von etwa 50µm erwiesen.In the radiation converter according to the invention, a gap is provided between the radiation absorber and the photocathode. As a result, the measurement of adversely affecting effect of UV photons can be reduced. The dynamics of the proposed radiation converter is improved. Another advantage is that the photocathode does not have to be made transparent due to the arrangement proposed here. It can thereby be achieved a cost savings. The distance between 10 and 100μm. A distance of approximately 50 μm has proven to be particularly advantageous.

Die Photokathode kann zweckmäßigerweise opak ausgebildet sein. UV-Photonen aus dem Lawinen-Bereich können nicht auf direktem Wege auf die Photokathode gelangen.The photocathode may expediently be made opaque. Avalanche UV photons can not reach the photocathode directly.

Nach einem weiteren Ausgestaltungsmerkmal ist die Photokathode aus einem metallischen Material hergestellt, das vorzugsweise Gold, Cäsium, Kupfer oder Antimon enthält. Zweckmäßig ist es weiter, daß die Photokathode als Schicht auf den Elektronenvervielfacher ausgebildet ist, wobei der Elektronenvervielfacher wiederum als Schicht auf dem Elektronendetektor ausgebildet sein kann. Nach einer besonders vorteilhaften Ausführung weist der Elektronenvervielfacher eine gelochte, vorzugsweise aus Polyimid hergestellte, Kunststoffolie auf. Der Durchmesser der Löcher beträgt etwa 25 µm.According to a further embodiment feature, the photocathode is made of a metallic material which preferably contains gold, cesium, copper or antimony. It is further expedient that the photocathode is formed as a layer on the electron multiplier, wherein the electron multiplier can in turn be formed as a layer on the electron detector. According to a particularly advantageous embodiment, the electron multiplier has a perforated, preferably made of polyimide, plastic film. The diameter of the holes is about 25 microns.

Vorteilhaft ist es, wenn dem Strahlenabsorber, dem Elektrodensystem, dem Elektronenvervielfacher und dem Elektronendetektor ein gemeinsames, gasdichtes Gehäuse zugeordnet ist, wodurch sich ein kompakter Aufbau des Strahlungswandlers ergibt. Vorzugsweise ist im Gehäuse ein UV-Photonen absorbierendes Gas aufgenommen. Das Gas kann mindestens einen der folgenden Bestandteile aufweisen: Argon, Krypton, Xenon, Helium, Neon, CO2, N2, Kohlenwasserstoff, Di-Methyl-Äther, Methanol-/Ethanol-Dampf.It is advantageous if the radiation absorber, the electrode system, the electron multiplier and the electron detector, a common, gas-tight housing is assigned, resulting in a compact design of the radiation converter. Preferably, a UV photon absorbing gas is received in the housing. The gas may include at least one of argon, krypton, xenon, helium, neon, CO 2 , N 2 , hydrocarbon, di-methyl ether, methanol / ethanol vapor.

Der Strahlenabsorber wandelt Strahlung in Lichtphotonen insbesondere dann vorteilhaft, wenn er eine nadelförmige Struktur aufweist und aus CsI:Na besteht.The radiation absorber converts radiation into light photons in particular advantageously if it has a needle-shaped structure and consists of CsI: Na.

Besonders vorteilhaft ist der Elektronendetektor als 2D-Dünnschichtpanel ausgeführt und besteht aus a-Se, a-Si:H oder Poly-Si. Ein solcher Elektronendetektor ist einfach im Aufbau und kostengünstig.Particularly advantageously, the electron detector is designed as a 2D thin-film panel and consists of a-Se, a-Si: H or poly-Si. Such an electron detector is simple in construction and inexpensive.

Weitere Vorteile und Einzelheiten der Erfindung ergeben sich aus der nachfolgenden Beschreibung eines Ausführungsbeispieles anhand der Zeichnungen. Hierin zeigen:

Fig. 1
eine schematische Querschnittsansicht eines Strahlungswandlers und
Fig. 2
die Modulationstransferfunktion als Funktion der Ortsfrequenz.
Further advantages and details of the invention will become apparent from the following description of an embodiment with reference to the drawings. Herein show:
Fig. 1
a schematic cross-sectional view of a radiation converter and
Fig. 2
the modulation transfer function as a function of the spatial frequency.

Bei dem in der Fig. 1 gezeigten Strahlungswandler ist mit dem Bezugszeichen 1 eine Gehäuse bezeichnet. Das Gehäuse weist einen Strahlenabsorber 2 auf, der Strahlung in Lichtphotonen wandelt. Der Strahlenabsorber 2 ist entweder als separates Teil ausgeführt oder außerhalb des Gehäuses 1 im Bereich einer ersten Stirnseite angeordnet. Er besteht aus einem Szintillatormaterial, vorzugsweise aus CsI:Na in Nadelstruktur, wobei die Nadeln in Richtung einer Photokathode 3 gerichtet sind. Die Photokathode 3 ist in einem Abstand a von etwa 50µm von Strahlenabsorber 2 entfernt angeordnet. Sie ist als Schicht, die vorzugsweise aus Kupfer hergestellt ist, auf einer gelochten Polyimid-Folie 4 ausgeführt. Die Polyimid-Folie 4 wirkt als Elektronenvervielfacher. Sie ist aufgebracht auf einen Elektronendetektor 5. Der Elektronendetektor 5 weist vorzugsweise eine Pixelstruktur auf und wandelt die auftreffenden Elektronen in elektrische Signale, die über geeignete bekannte Maßnahmen, beispielsweise eine elektrische Leitung, ableitbar sind und aufgrund deren eine bildliche Darstellung an einer Anzeigevorrichtung möglich ist. Der Elektronendetektor 5 ist hierzu vorzugsweise als 2D-Dünnschichtpanel ausgeführt und kann vorzugsweise aus a-Se, a-Si:H oder Poly-Si bestehen. Innerhalb des Gehäuses 1, insbesondere zwischen dem Strahlenabsorber 2 und der Photokathode 3, ist ein Gas, insbesondere Quenchgas, beispielsweise eine Mischung aus Argon und Kohlenwasserstoff, aufgenommen.In the in the Fig. 1 shown radiation converter is designated by the reference numeral 1, a housing. The housing has a radiation absorber 2, which converts radiation into light photons. The radiation absorber 2 is either designed as a separate part or arranged outside the housing 1 in the region of a first end face. It consists of a scintillator material, preferably of CsI: Na in needle structure, the needles being directed in the direction of a photocathode 3 are. The photocathode 3 is arranged at a distance a of approximately 50 μm from the radiation absorber 2. It is designed as a layer, which is preferably made of copper, on a perforated polyimide film 4. The polyimide film 4 acts as an electron multiplier. It is applied to an electron detector 5. The electron detector 5 preferably has a pixel structure and converts the incident electrons into electrical signals which can be derived via suitable known measures, for example an electrical line, and on the basis of which a pictorial representation on a display device is possible. For this purpose, the electron detector 5 is preferably designed as a 2D thin-film panel and may preferably consist of a-Se, a-Si: H or poly-Si. Within the housing 1, in particular between the radiation absorber 2 and the photocathode 3, a gas, in particular quenching gas, for example, a mixture of argon and hydrocarbon, is added.

Die Funktion der Vorrichtung ist folgende:The function of the device is as follows:

Röntgenstrahlen werden vom Strahlenabsorber 2 absorbiert und dabei in Photonen umgewandelt. Die Photonen setzen Photoelektronen aus der Photokathode 3 frei. Die Photoelektronen gelangen in den Bereich der gelochten Polyimid-Folie 4. Zwischen der Photokathode 3 und dem Elektronendetektor 5 ist ein Potential angelegt. Durch das angelegte elektrische Potential wird erreicht, daß alle Photoelektronen von der Oberfläche der Photokathode 3 in die nächstliegenden Löcher gezogen werden. In dem stark anwachsenden elektrischen Feld findet durch Stoßionisation eine Ladungsträgervervielfachung statt. Die Ladungsträgervervielfachung bzw. Verstärkung ist durch die Höhe des angelegten Potentials einstellbar. Damit kann das Signal/Rauschverhältnis verbessert werden. Die Photoelektronen werden durch das angelegte Potential auf den Elektronendetektor beschleunigt. Die dort akkumulierten Ladungen werden mit einer vorgegebenen Taktsequenz ausgelesen.X-rays are absorbed by the radiation absorber 2 and thereby converted into photons. The photons release photoelectrons from the photocathode 3. The photoelectrons reach the area of the perforated polyimide film 4. A potential is applied between the photocathode 3 and the electron detector 5. By the applied electric potential is achieved that all the photoelectrons are pulled from the surface of the photocathode 3 in the nearest holes. In the strongly growing electric field, charge ionization takes place by impact ionization. The charge carrier multiplication or gain can be set by the level of the applied potential. Thus, the signal / noise ratio can be improved. The photoelectrons are accelerated by the applied potential on the electron detector. The charges accumulated there are read out with a predetermined clock sequence.

Zur Reduzierung von UV-Photonen kann der Strahlenabsorber 2 mit einer UV-photonenabsorbierenden Leitschicht versehen sein. Durch das Quenchgas werden die bei der durch Stoßionisation erzeugten UV-Photonen absorbiert, damit diese nicht zur Photokathode 3 gelangen, wo sie Photoelektronen ungewollt auslösen könnten.To reduce UV photons, the radiation absorber 2 may be provided with a UV-photon absorbing conductive layer. The quench gas absorbs the UV photons generated by impact ionization so that they do not reach the photocathode 3, where they could unintentionally trigger photoelectrons.

In Fig. 2 ist über der Ortsfrequenz die Modulationstransferfunktion aufgetragen. Die Kurven MTF 1 und MTF 2 zeigen die Modulationstransferfunktion bei einem Abstand der Photokathode 3 vom Strahlenabsorber 2 von 50µm. Die Kurve MTF 2 zeigt die Punktbildfunktion einer isotropen Punktquelle, die Kurve MTF 1 die vorgenannte Punktbildfunktion für eine Lambertquelle.In Fig. 2 the modulation transfer function is plotted above the spatial frequency. The curves MTF 1 and MTF 2 show the modulation transfer function at a distance of the photocathode 3 from the beam absorber 2 of 50 μm. The curve MTF 2 shows the dot image function of an isotropic point source, the curve MTF 1 the aforementioned point image function for a Lambert source.

Die Kurve MTF 3 zeigt die Modulationstransferfunktion, wobei hier der Strahlenabsorber 2 in direktem Kontakt mit dem Elektronendetektor 5 ist. Die Kurve MTF 3 repräsentiert damit die Charakteristik von herkömmlichen Flachdetektoren. Die Werte MTF 4 geben die Modulationstransferfunktion für eine Lambertquelle an, wobei der Strahlenabsorber 2 in einem Abstand von 50µm von dem Elektronendetektor 5 angeordnet ist. Es zeigt sich, daß die beabstandete Anordnung keine wesentliche Änderung der Modulationstransferfunktion mit sich bringt.The curve MTF 3 shows the modulation transfer function, in which case the radiation absorber 2 is in direct contact with the electron detector 5. The curve MTF 3 thus represents the characteristic of conventional flat-panel detectors. The values MTF 4 indicate the modulation transfer function for a Lambert source, wherein the beam absorber 2 is arranged at a distance of 50 μm from the electron detector 5. It can be seen that the spaced array does not significantly change the modulation transfer function.

Claims (12)

  1. Radiation converter having a radiation absorber (2) for generating photons in a manner dependent on the intensity of impinging x-ray radiation,
    having a photocathode (3) arranged downstream of the radiation absorber (2) in the radiation direction at a distance (a) and serving for generating electrons in a manner dependent on the photons emerging from the radiation absorber (2),
    having a device for accelerating the electrons emerging from the photocathode (3) onto an electron detector (5) for generating electrical signals in a manner dependent on the impinging electrons, and
    having an electron multiplier (4) arranged between the photocathode (3) and the electron detector (5), in which case the electrons emerging from the photocathode (3) can be multiplied by the electron multiplier (4) and characterized in that the distance (a) is between 10 and 100 µm.
  2. Radiation converter according to Claim 1, in which case the photocathode (3) is opaque.
  3. Radiation converter according to one of the preceding Claims, in which case the photocathode (3) is produced from a metallic material which preferably contains gold, cesium, copper or antimony.
  4. Radiation converter according to one of the preceding Claims, in which case the photocathode (3) is formed as a layer on the electron multiplier (4).
  5. Radiation converter according to one of the preceding Claims, in which case the electron multiplier (4) is formed as a layer on the electron detector (5).
  6. Radiation converter according to one of the preceding Claims, in which case the electron multiplier (4) has a perforated plastic film preferably produced from polyimide.
  7. Radiation converter according to one of the preceding Claims, in which case the radiation absorber (2), the electron multiplier (4) and the electron detector (5) are accommodated in a common gastight housing (1).
  8. Radiation converter according to Claim 7, in which case a gas absorbing UV photons is accommodated in the housing (1).
  9. Radiation converter according to Claim 8, in which the gas has at least one of the following constituents: argon, krypton, xenon, helium, neon, CO2, N2, hydrocarbon, dimethyl ether, methanol/ethanol vapor.
  10. Radiation converter according to one of the preceding Claims, in which the radiation absorber (2) is produced from a scintillator material which preferably has an acicular structure comprising CsI:Na.
  11. Radiation converter according to one of the preceding Claims, in which the electron detector (5) is embodied as a 2D thin-film panel.
  12. Radiation converter according to Claim 11, in which the 2D thin-film panel is formed from a-Se, a-Si:H or poly-Si.
EP01935937A 2000-03-23 2001-03-22 Radiation converter comprising a scintillator, a photocathode and an electron multiplier Expired - Lifetime EP1266391B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10014311A DE10014311C2 (en) 2000-03-23 2000-03-23 radiation converter
DE10014311 2000-03-23
PCT/DE2001/001109 WO2001071381A2 (en) 2000-03-23 2001-03-22 Radiation converter with a scintillator a photocathode and an electron multiplier

Publications (2)

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EP1266391A2 EP1266391A2 (en) 2002-12-18
EP1266391B1 true EP1266391B1 (en) 2008-07-16

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EP01935937A Expired - Lifetime EP1266391B1 (en) 2000-03-23 2001-03-22 Radiation converter comprising a scintillator, a photocathode and an electron multiplier

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US (1) US7022994B2 (en)
EP (1) EP1266391B1 (en)
JP (1) JP2003528427A (en)
DE (2) DE10014311C2 (en)
WO (1) WO2001071381A2 (en)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3145066A1 (en) 1981-11-13 1983-05-19 Fritz Werner Industrie-Ausrüstungen GmbH, 6222 Geisenheim Process for producing a comparatively higher-energy, nitrogen-rich gas and equipment for carrying out the process
US6747258B2 (en) * 2001-10-09 2004-06-08 Itt Manufacturing Enterprises, Inc. Intensified hybrid solid-state sensor with an insulating layer
US7015452B2 (en) 2001-10-09 2006-03-21 Itt Manufacturing Enterprises, Inc. Intensified hybrid solid-state sensor
US7791047B2 (en) 2003-12-12 2010-09-07 Semequip, Inc. Method and apparatus for extracting ions from an ion source for use in ion implantation
US7835502B2 (en) * 2009-02-11 2010-11-16 Tomotherapy Incorporated Target pedestal assembly and method of preserving the target
JP5554322B2 (en) * 2009-04-01 2014-07-23 株式会社トクヤマ Radiation image detector
US8395312B2 (en) * 2010-04-19 2013-03-12 Bridgelux, Inc. Phosphor converted light source having an additional LED to provide long wavelength light
WO2014133849A2 (en) 2013-02-26 2014-09-04 Accuray Incorporated Electromagnetically actuated multi-leaf collimator
GB2524778A (en) * 2014-04-02 2015-10-07 Univ Warwick Ultraviolet light detection

Family Cites Families (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1175597A (en) * 1967-06-16 1969-12-23 Mullard Ltd Improvements in or relating to Image Intensifiers
US3609359A (en) * 1969-01-08 1971-09-28 Eugene Wainer X-ray image intensifier with electron michrochannels and electron multiplying means
US3846630A (en) * 1970-01-07 1974-11-05 Zeev D Ben Method for identifying elemental areas of a photocathode
US3710125A (en) * 1970-04-29 1973-01-09 Univ Northwestern Secondary emission enhancer for an x-ray image intensifier
GB1457213A (en) * 1975-01-30 1976-12-01 Mullard Ltd Electron multipliers
US4345153A (en) * 1980-07-30 1982-08-17 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Low intensity X-ray and gamma-ray spectrometer
US4376892A (en) * 1980-10-16 1983-03-15 Agence Nationale De Valorisation De La Recherche (Anvar) Detection and imaging of the spatial distribution of visible or ultraviolet photons
FR2494906A1 (en) * 1980-11-25 1982-05-28 Thomson Csf ELECTRON MULTIPLICATION PHOTODETECTOR TUBE FOR USE IN A COLOR VIDEO READER
DE3332648A1 (en) 1983-09-09 1985-03-28 Siemens AG, 1000 Berlin und 8000 München X-RAY DIAGNOSTIC DEVICE WITH A X-RAY CONVERTER
US4866970A (en) * 1985-04-24 1989-09-19 Albino Castiglioni Apparatus for the continuous shearing off and cold swaging of metal workpieces
EP0534547B1 (en) * 1991-09-27 1996-09-04 Koninklijke Philips Electronics N.V. X-ray detector with charge pattern read-out
DE4237097A1 (en) 1991-11-19 1993-05-27 Siemens Ag X=ray image intensifier with vacuum housing having input light screening - has input window of vacuum housing and photocathode optically coupled on one side of glass carrier and electron multiplying stage
GB2269048B (en) * 1992-07-03 1995-10-04 Third Generation Technology Li Photoemitters
JPH07294644A (en) * 1994-04-25 1995-11-10 Shimadzu Corp Two-dimensional radiation detector
DE4429925C1 (en) * 1994-08-23 1995-11-23 Roentdek Handels Gmbh Electronic contactless position determination of EM photons or particles e.g. electrons
DE19527794C2 (en) * 1995-07-19 1997-10-23 Ifg Inst Fuer Geraetebau Gmbh Method and device for producing optical elements for capillary optics
JP2001135267A (en) * 1999-09-08 2001-05-18 Siemens Ag Radiation converter

Also Published As

Publication number Publication date
US7022994B2 (en) 2006-04-04
DE10014311A1 (en) 2001-10-04
DE50114124D1 (en) 2008-08-28
US20030164682A1 (en) 2003-09-04
DE10014311C2 (en) 2003-08-14
WO2001071381A3 (en) 2002-04-18
JP2003528427A (en) 2003-09-24
WO2001071381A2 (en) 2001-09-27
EP1266391A2 (en) 2002-12-18

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