EP0021441A2 - Electron accelerator for X-ray therapy - Google Patents

Electron accelerator for X-ray therapy Download PDF

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Publication number
EP0021441A2
EP0021441A2 EP80103661A EP80103661A EP0021441A2 EP 0021441 A2 EP0021441 A2 EP 0021441A2 EP 80103661 A EP80103661 A EP 80103661A EP 80103661 A EP80103661 A EP 80103661A EP 0021441 A2 EP0021441 A2 EP 0021441A2
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Prior art keywords
electron
target
absorber
filter plate
electron accelerator
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EP80103661A
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German (de)
French (fr)
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EP0021441B1 (en
EP0021441A3 (en
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Leonhard Dipl.-Phys. Taumann
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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
    • H01J35/00—X-ray tubes
    • 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
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/10—Scattering devices; Absorbing devices; Ionising radiation filters

Definitions

  • the invention relates to an electron accelerator with an evacuated acceleration tube, with a target exposed to the electron beam, with an electron absorber downstream of the target in the beam direction, with a collimator and with a compensating body arranged centered on the axis of symmetry of the aperture of the collimator.
  • an electron accelerator which is preferably known for use in medical radiation therapy, is known.
  • a target is exposed to the electron beam emerging from the radiation exit window of the acceleration tube.
  • An electron absorber through which the electrons remaining in the X-rays are filtered out, is arranged in the beam direction behind the target.
  • a compensating body made of iron is attached to the collimator, centered on the collimator's fade-out opening and projecting into it. It compensates for the intensity of the radiation across the entire width of the X-ray field. With such an electron accelerator, it is felt to be disadvantageous that the low-energy X-ray component is relatively high.
  • the invention is therefore based on the object of achieving a hardening of the X-rays with the simplest possible means in an electron accelerator in which no deflection magnet is used.
  • a filter plate made of heavy metal, for example lead is therefore connected downstream of the electron absorber and the compensating body for this is never made of one material third atomic number, preferably made of aluminum.
  • a particularly expedient development of the invention is achieved if the filter plate is inserted between the electron absorber and the compensating body.
  • This has the advantage that the filter plate can no longer be hit by electrons due to the upstream electron absorber and therefore does not itself appear as a competing target.
  • the choice of filter material can only be based on its suitability for hardening the X-rays.
  • the compensation downstream of the filter plate in the beam direction body hit by X-rays which is largely homogenized by the upstream filter plate.
  • the target is attached to the side of the electron absorber facing the coating tube.
  • the electron absorber which must be kept much stronger in its dimensions than the target, which generally consists only of an approximately 3 mm thick lead foil, supports this.
  • this solution also lays the foundation for a further improvement of the construction.
  • the radiation exposure of the target can namely be significantly increased if the electron absorber is cooled in a particularly expedient embodiment of the invention.
  • the electron absorber not only serves as a protective base for the target, but also as a heat sink, on the solid wall of which coolant can be easily connected.
  • the figure shows a sectional view through the last two cavity resonators of an acceleration tube, through the target and through the collimator.
  • the two last, cavity-shaped cavity resonators 1, 2 of an acceleration tube 3 of a linear accelerator shown cut along its axis of symmetry 4.
  • the axis of symmetry of the cavity resonators coincides with the electron beam 5.
  • the outlet opening 6 of the last cavity 2 is closed by a metal plate with high thermal conductivity, the electron absorber 7, in the exemplary embodiment a 20 mm thick copper plate.
  • This electron absorber 7 is soldered onto the last cavity 2 in a gas-tight manner.
  • the location of the electron absorber 7 where the electron beam 5 would strike it is provided with a disk-shaped depression, into which a target 8 only a few tenths of a millimeter thick is soldered.
  • the electron absorber 7 is provided with cooling channels (not shown) which end in hose connections 9, 10 for connection to a cooling system (not shown here for the sake of clarity).
  • the electron absorber 7 carries a filter plate 11 on the side facing away from the target 8.
  • the collimator 12 is arranged with a conical opening 13 for the passage of the X-ray field 14 that is maximally used.
  • a compensating body 15 is fastened to the collimator 12, by means of which the intensity profile of the X-ray radiation following a Gaussian distribution curve is compensated for over the entire cross-section of the X-ray field 14 that is maximally used.
  • the electrons accelerated by the acceleration tube 3 strike the target 8 which closes the exit opening 6 of the accelerator tube 3.
  • X-ray brake radiation is generated in the target.
  • the waste heat generated in the target is via the solder joint tion between target 8 and electron absorber 7 passed through to the electron absorber and flows there to a coolant.
  • the electrons passing through the target are braked and absorbed in the material of the electron absorber 7 located behind them. For this reason, no further X-ray radiation can be generated in the filter plate 11 arranged behind the electron absorber 7 in the beam direction.
  • a material has therefore been used for the filter plate 11, which has been selected solely on the basis of its absorption properties - the largest possible absorption factor in the range of low-energy X-ray quanta of 1 to 3 MeV and the smallest possible absorption factor in the range of higher-energy X-ray quanta above 3 MeV.
  • the heavy metals lead, tantalum, gold, tungsten and uranium are particularly suitable for this purpose.
  • a 2 mm thick filter plate made of lead was used for an electron energy of approx. 4 MeV. Since the filter plate 11 has the same strength over the entire maximum radiation cross section that is used, the hardening effect for the radiation is also uniform over this entire radiation cross section.
  • the compensating body following in the beam direction therefore does not need and should no longer show any hardening effect. It can therefore be made of a material with a low atomic number, in which the absorption is approximately the same over the entire X-ray energy spectrum that occurs. Aluminum is particularly well suited for this.
  • the advantage of this design can be seen in particular in the fact that the omission of the complex and bulky 270 ° deflection and focusing magnet for
  • the disadvantages associated with the electron beam 5 with regard to the radiation quality can largely be compensated for by the compensating body 15 being made from a material of low atomic number, for example aluminum, and a filter plate 11 being used behind the electron absorber 7, which preferably absorbs lower-energy X-ray quanta.
  • the design is not only decidedly cheaper, it also leads to devices that are much smaller and easier to position in medical applications.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Particle Accelerators (AREA)
  • Radiation-Therapy Devices (AREA)
  • Apparatus For Radiation Diagnosis (AREA)

Abstract

Die Erfindung bezieht sich auf einen Elektronenbeschleuniger mit einer evakuierten Beschleunigungsröhre (3), mit einem dem Elektronenstrahl ausgesetzten Target (8), mit einem dem Target in Strahlenrichtung nachgeschalteten Elektronenabsorber (7) mit einem Kollimator (12) und mit einem zentriert zur Symmetrieachse (4) angeordneten Ausgleichskörper (15). Bei solchen in der Strahlentherapie zur Anwendung kommenden Elektronenbeschleunigern soll die weiche Strahlenkomponente möglichst stark unterdrückt werden. Die Erfindung sieht hierzu vor, daß dem Elektronenabsorber eine aus Schwermetall gefertigte Filterplatte (11) nachgeschaltet ist und der Ausgleichskörper dafür aus einem Material vergleichsweise niedrigerer Ordnungszahl gefertigt ist. Die Filterplatte (11) kann zwischen dem Elektronenabsorber (7) und dem Ausgleichskörper (15) eingesetzt sein. Das Target (8) kann auf der der Beschleunigungsröhre zugewandten Seite des Elektronenabsorbers angebracht sein. Zusätzlich kann der Elektronenabsorber (7) gekühlt sein.The invention relates to an electron accelerator with an evacuated acceleration tube (3), with a target (8) exposed to the electron beam, with an electron absorber (7) downstream of the target in the beam direction, with a collimator (12) and with one centered on the axis of symmetry (4 ) arranged compensating body (15). In such electron accelerators used in radiation therapy, the soft radiation component should be suppressed as much as possible. To this end, the invention provides that a filter plate (11) made of heavy metal is connected downstream of the electron absorber and the compensating body is made of a material of a comparatively lower atomic number. The filter plate (11) can be inserted between the electron absorber (7) and the compensating body (15). The target (8) can be attached to the side of the electron absorber facing the acceleration tube. In addition, the electron absorber (7) can be cooled.

Description

Die Erfindung bezieht sich auf einen Elektronenbeschleuniger mit einer evakuierten Beschleunigungsröhre, mit einem dem Elektronenstrahl ausgesetzten Target, mit einem dem Target in Strahlenrichtung nachgeschalteten Elektronenabsorber, mit einem Kollimator und mit einem zentriert zur Symmetrieachse der Ausblendöffnung des Kollimators angeordneten Ausgleichskörpers.The invention relates to an electron accelerator with an evacuated acceleration tube, with a target exposed to the electron beam, with an electron absorber downstream of the target in the beam direction, with a collimator and with a compensating body arranged centered on the axis of symmetry of the aperture of the collimator.

Durch die DE-OS 27 27 275 ist ein vorzugsweise für den Einsatz in der medizinischen Strahlentherapie bestimmter Elektronenbeschleuniger bekannt. Bei diesem Elektronenbeschleuniger ist ein Target dem aus dem Strahlenaustrittsfenster der Beschleunigungsröhre austretenden Elektronenstrahl ausgesetzt. In Strahlenrichtung hinter dem Target ist ein Elektronenabsorber, durch den die in der Röntgenstrahlung übriggebliebenen Elektronen herausgefiltert werden, angeordnet. In Strahlenrichtung hinter dem Elektronenabsorber befindet sich ein Kollimator für die Ausblendung des maximalen zur Anwendung kommenden Röntgenstrahlenfeldes. Zur Ausblendöffnung des Kollimators zentriert, in denselben hineinragend, ist ein aus Eisen gefertigter Ausgleichskörper am Kollimator befestigt. Durch ihn wird die Intensität der Strahlung über die gesamte Breite des Röntgenstrahlenfeldes hinweg ausgeglichen. Bei einem solchen Elektronenbeschleuniger wird es als nachteilig empfunden, daß der niederenergetische Röntgenstrahlenanteil relativ hoch ist.From DE-OS 27 27 275, an electron accelerator, which is preferably known for use in medical radiation therapy, is known. In this electron accelerator, a target is exposed to the electron beam emerging from the radiation exit window of the acceleration tube. An electron absorber, through which the electrons remaining in the X-rays are filtered out, is arranged in the beam direction behind the target. There is a collimator in the beam direction behind the electron absorber to suppress the maximum X-ray field to be used. A compensating body made of iron is attached to the collimator, centered on the collimator's fade-out opening and projecting into it. It compensates for the intensity of the radiation across the entire width of the X-ray field. With such an electron accelerator, it is felt to be disadvantageous that the low-energy X-ray component is relatively high.

Zwar ist es zur Reduzierung des niederenergetischen Röntgenstrahlenanteils bei dem der obengenannten DE-PS 27 27 275 zugrundeliegenden Gerät bekannt, in dem Elektronenstrahl einen diesen um 2700 umlenkenden und die Elektronen vorgegebener Energie fokussierenden Umlenkmagneten einzusetzen. Auf-diese Weise wird das Target nur noch von Elektronen der jeweils eingestellten Beschleunigungsenergie getroffen. Ein solcher Umlenkmagnet ist in seiner Konstruktion jedoch außerordentlich aufwendig und benötigt auch einen entsprechend großen Platz zwischen dem Strahlenaustrittsfenster der Beschleunigungsröhre und dem Target. Dieses wiederum beeinflußt die Baugröße des Beschleunigers in unerwünschter Weise.While it is in the use for reducing the low-energy x-ray portion of the above-mentioned DE-PS 27 27 275 underlying device known in the electron beam a deflecting these to 270 0 and the electrons of predetermined energy-focusing deflection magnet. In this way, the target is only hit by electrons of the respectively set acceleration energy. However, such a deflecting magnet is extremely complex in its construction and also requires a correspondingly large space between the radiation exit window of the acceleration tube and the target. This in turn affects the size of the accelerator in an undesirable manner.

Der Erfindung liegt daher die Aufgabe zugrunde, bei einem Elektronenbeschleuniger, bei dem kein Umlenkmagnet verwendet wird, eine Aufhärtung der Röntgenstrahlung mit möglichst einfachen Mitteln zu erreichen.The invention is therefore based on the object of achieving a hardening of the X-rays with the simplest possible means in an electron accelerator in which no deflection magnet is used.

Bei einem Elektronenbeschleuniger der eingangs genannten Art ist daher erfindungsgemäß dem Elektronenabsorber eine aus Schwermetall, z.B. aus Blei, gefertigte Filterplatte nachgeschaltet und ist der Ausgleichskörper dafür aus einem Material vergleichsweise niedriger Ordnungszahl, vorzugsweise aus Aluminium, gefertigt. Dabei wird die Tatsache ausgenützt, daß die Elemente höherer Ordnungszahl Röntgenquanten niedriger Energie verhältnismäßig stärker schwächen als Röntgenquanten höherer Energie, d.h., daß über den gesamten Strahlenquerschnitt hinweg verstärkt jene Röntgenquanten absorbiert werden, deren Energie im Absorptionsmaximum des Materials der Filterplatte liegt. Bei den für die Filterplatte in Frage kommenden Schwermetallen, wie z.B. Uran, Wolfram, Tantal, Gold und Blei, werden auf diese Weise insbesondere jene Röntgenquanten mit Energien zwischen 1 und 3 MeV verstärkt absorbiert. Diese Lösung bringt den besonderen Vorteil mit sich, daß durch den aus Aluminium gefertigten Ausgleichskörper selbst keinerlei Aufhärtung der Strahlung, wie das der Fall gewesen wäre, wenn dieser aus einem Material höherer Ordnungszahl, wie z.B. Kupfer oder gar Blei, gefertigt worden wäre, erfolgt. Eine Aufhärtung der Röntgenstrahlung durch den Ausgleichskörper hätte wegen der unterschiedlichen Dicke des Ausgleichskörpers zu einer unerwünschten, im Strahlenkegel radial abnehmenden Aufhärtung geführt.In the case of an electron accelerator of the type mentioned at the outset, a filter plate made of heavy metal, for example lead, is therefore connected downstream of the electron absorber and the compensating body for this is never made of one material third atomic number, preferably made of aluminum. This takes advantage of the fact that the elements of higher atomic numbers weaken X-ray quanta of lower energy comparatively more strongly than X-ray quanta of higher energy, ie that X-ray quanta whose energy lies in the absorption maximum of the material of the filter plate are increasingly absorbed over the entire radiation cross-section. In the case of the heavy metals that are suitable for the filter plate, such as uranium, tungsten, tantalum, gold and lead, in particular those X-ray quanta with energies between 1 and 3 MeV are more strongly absorbed in this way. This solution has the particular advantage that the compensation body made of aluminum does not itself harden the radiation, as would have been the case if it had been made of a higher atomic number material, such as copper or even lead. Hardening of the X-ray radiation by the compensating body would have led to an undesired hardening which decreases radially in the beam cone because of the different thickness of the compensating body.

Eine besonders zweckmäßige Weiterbildung der Erfindung wird erreicht, wenn die Filterplatte zwischen dem Elektronenabsorber und dem Ausgleichskörper eingesetzt ist. Dies hat den Vorteil, daß die Filterplatte wegen des in Strahlenrichtung vorgeschalteten Elektronenabsorbers nicht mehr von Elektronen getroffen werden kann und daher selbst nicht als konkurrierendes Target in Erscheinung tritt. Unter dieser Voraussetzung kann die Wahl des Filtermaterials ausschließlich auf seine Eignung zur Aufhärtung der Röntgenstrahlung abgestellt werden. Darüber hinaus wird der der Filterplatte in Strahlenrichtung nachgeschaltete Ausgleichskörper von Röntgenstrahlung getroffen, die durch die vorgeschaltete Filterplatte weitgehend homogenisiert ist.A particularly expedient development of the invention is achieved if the filter plate is inserted between the electron absorber and the compensating body. This has the advantage that the filter plate can no longer be hit by electrons due to the upstream electron absorber and therefore does not itself appear as a competing target. Under this condition, the choice of filter material can only be based on its suitability for hardening the X-rays. In addition, the compensation downstream of the filter plate in the beam direction body hit by X-rays, which is largely homogenized by the upstream filter plate.

Eine besonders einfache Konstruktion ergibt sich, wenn das Target in vorteilhafter Weiterbildung der Erfindung auf der der Beschlenigungsröhre zugewandten Seite des Elektronenabsorbers angebracht ist. In diesem Fall stützt der Elektronenabsorber, der in seinen Abmessungen deutlich stärker gehalten werden muß als das im allgemeinen nur aus einer ca. 3 mm starken Bleifolie bestehende Target, dieses ab. Außer der verbesserten mechanischen Schutzfunktion legt diese Lösung zugleich die Basis für eine weitere Verbesserung der Konstruktion.A particularly simple construction results if, in an advantageous further development of the invention, the target is attached to the side of the electron absorber facing the coating tube. In this case, the electron absorber, which must be kept much stronger in its dimensions than the target, which generally consists only of an approximately 3 mm thick lead foil, supports this. In addition to the improved mechanical protection function, this solution also lays the foundation for a further improvement of the construction.

Die Strahlenbelastung des Targets läßt sich nämlich bedeutend erhöhen, wenn der Elektronenabsorber in besonders zweckmäßiger Ausgestaltung der Erfindung gekühlt ist. In diesem Fall dient der Elektronenabsorber nicht nur als schützende Unterlage für das Target, sondern zugleich auch als Kühlkörper, an dessen massiver Wand leicht Kühlmittel angeschlossen werden können.The radiation exposure of the target can namely be significantly increased if the electron absorber is cooled in a particularly expedient embodiment of the invention. In this case, the electron absorber not only serves as a protective base for the target, but also as a heat sink, on the solid wall of which coolant can be easily connected.

Weitere Einzelheiten der Erfindung werden anhand eines in der Figur gezeichneten Ausführungsbeispiels erläutert.Further details of the invention will be explained with reference to an embodiment shown in the figure.

Die Figur zeigt eine Schnittdarstellung durch die beiden letzten Hohlraumresonatoren einer Beschleunigungsröhre, durch das Target und durch den Kollimator.The figure shows a sectional view through the last two cavity resonators of an acceleration tube, through the target and through the collimator.

In der Figur sind die beiden letzten,scheibenförmig aufeinander gesetzten Hohlraumresonatoren 1, 2 einer Beschleunigungsröhre 3 eines Linearbeschleunigers längs ihrer Symmetrieachse 4 aufgeschnitten dargestellt. Die Symmetrieachse der Hohlraumresonatoren fällt mit dem Elektronenstrahl 5 zusammen. Die Austrittsöffnung 6 des letzten Hohlraumresonators 2 ist durch eine Metallplatte hoher Wärmeleitfähigkeit, dem Elektronenabsorber 7, im Ausführungsbeispiel eine 20 mm starke Kupferplatte, abgeschlossen. Dieser Elektronenabsorber 7 ist auf den letzten Hohlraumresonator 2 gasdicht aufgelötet. An der Stelle des Elektronenabsorbers 7, auf der der Elektronenstrahl 5 auftreffen würde, ist dieser mit einer scheibenförmigen Einsenkung versehen, in die ein nur wenige Zehntel mm dickes Target 8 aufgelötet ist. Zugleich,ist der Elektronenabsorber 7 mit Kühlkanälen (nicht dargestellt) versehen, die zum Anschluß an ein der Übersichtlichkeit halber hier nicht dargestelltes Kühlsystem in Schlauchanschlüssen 9, 10 enden. Der Elektronenabsorber 7 trägt auf der dem Target 8 abgewandten Seite eine Filterplatte 11. In Strahlenrichtung hinter dem Elektronenabsorber 7 und der auf dem Elektronenabsorber aufgeschraubten Filterplatte ist der Kollimator 12 mit einer kegelförmigen Öffnung 13 für den Durchtritt des maximal zur Anwendung kommenden Röntgenstrahlenfeldes 14 angeordnet. Am Kollimator 12 ist ein Ausgleichskörper 15 befestigt, durch den der einer Gauß'schen Verteilungskurve folgende Intensitätsverlauf der Röntgenstrahlung über den gesamten Querschnitt des maximal zur Anwendung kommenden Röntgenstrahlenfeldes 14 ausgeglichen wird.In the figure, the two last, cavity-shaped cavity resonators 1, 2 of an acceleration tube 3 of a linear accelerator shown cut along its axis of symmetry 4. The axis of symmetry of the cavity resonators coincides with the electron beam 5. The outlet opening 6 of the last cavity 2 is closed by a metal plate with high thermal conductivity, the electron absorber 7, in the exemplary embodiment a 20 mm thick copper plate. This electron absorber 7 is soldered onto the last cavity 2 in a gas-tight manner. At the location of the electron absorber 7 where the electron beam 5 would strike, it is provided with a disk-shaped depression, into which a target 8 only a few tenths of a millimeter thick is soldered. At the same time, the electron absorber 7 is provided with cooling channels (not shown) which end in hose connections 9, 10 for connection to a cooling system (not shown here for the sake of clarity). The electron absorber 7 carries a filter plate 11 on the side facing away from the target 8. In the beam direction behind the electron absorber 7 and the filter plate screwed onto the electron absorber, the collimator 12 is arranged with a conical opening 13 for the passage of the X-ray field 14 that is maximally used. A compensating body 15 is fastened to the collimator 12, by means of which the intensity profile of the X-ray radiation following a Gaussian distribution curve is compensated for over the entire cross-section of the X-ray field 14 that is maximally used.

Beim Betrieb des Elektronenbeschleunigers treffen die durch die Beschleunigungsröhre 3 beschleunigten Elektronen unmittelbar auf das die Austrittsöffnung 6 der Beschleunigerröhre 3 abschließende Target 8 auf. Dabei wird im Target Röntgenbremsstrahlung erzeugt. Die im Target entstehende Abwärme wird über die Lötverbindung zwischen Target 8 und Elektronenabsorber 7 hindurch an den Elektronenabsorber abgegeben und fließt dort an ein Kühlmittel ab. Die durch das Target hindurchgehenden Elektronen werden im Material des dahinter befindlichen Elektronenabsorbers 7 abgebremst und absorbiert. Aus diesem Grund kann in der in Strahlenrichtung hinter dem Elektronenabsorber 7 angeordneten Filterplatte 11 auch keine weitere Röntgenstrahlung mehr erzeugt werden. Für die Filterplatte 11 ist daher ein Material verwandt worden, das allein aufgrund seiner Absorptionseigenschaften - einem möglichst großen Absorptionsfaktor im Bereich der niederenergetischen Röntgenquanten von 1 bis 3 MeV und einem möglichst kleinen Absorptionsfaktor im Bereich der höherenergetischen Röntgenquanten oberhalb von 3 MeV - ausgewählt worden ist. Für diesen Zweck eignen sich besonders die Schwermetalle Blei, Tantal, Gold, Wolfram und Uran. Im vorliegenden Fall ist bei einer zur Anwendung kommenden Elektronenenergie von ca. 4 MeV eine 2 mm dicke Filterplatte aus Blei verwandt worden. Da die Filterplatte 11 über den gesamten maximalen zur Anwendung kommenden Strahlenquerschnitt hinweg gleich stark ist, ist der Aufhärtungseffekt für die Strahlung auch über diesen gesamten Strahlenquerschnitt hinweg gleichmäßig. Der in Strahlenrichtung nachfolgende Ausgleichskörper braucht und soll daher keinerlei Aufhärtungseffekt mehr zeigen. Er kann daher aus einem Material niedriger Ordnungszahl gefertigt sein, bei dem die Absorption über das gesamte vorkommende Röntgenenergiespektrum etwa gleich groß ist. Hierfür ist Aluminium besonders gut geeignet.During operation of the electron accelerator, the electrons accelerated by the acceleration tube 3 strike the target 8 which closes the exit opening 6 of the accelerator tube 3. X-ray brake radiation is generated in the target. The waste heat generated in the target is via the solder joint tion between target 8 and electron absorber 7 passed through to the electron absorber and flows there to a coolant. The electrons passing through the target are braked and absorbed in the material of the electron absorber 7 located behind them. For this reason, no further X-ray radiation can be generated in the filter plate 11 arranged behind the electron absorber 7 in the beam direction. A material has therefore been used for the filter plate 11, which has been selected solely on the basis of its absorption properties - the largest possible absorption factor in the range of low-energy X-ray quanta of 1 to 3 MeV and the smallest possible absorption factor in the range of higher-energy X-ray quanta above 3 MeV. The heavy metals lead, tantalum, gold, tungsten and uranium are particularly suitable for this purpose. In the present case, a 2 mm thick filter plate made of lead was used for an electron energy of approx. 4 MeV. Since the filter plate 11 has the same strength over the entire maximum radiation cross section that is used, the hardening effect for the radiation is also uniform over this entire radiation cross section. The compensating body following in the beam direction therefore does not need and should no longer show any hardening effect. It can therefore be made of a material with a low atomic number, in which the absorption is approximately the same over the entire X-ray energy spectrum that occurs. Aluminum is particularly well suited for this.

Der Vorteil dieser Bauweise ist insbesondere darin zu sehen, daß die mit dem Weglassen des aufwendigen und sperrigen 270°-Umlenk- und Fokussierurgsmagneten für den Elektronenstrahl 5 verbundenen Nachteile hinsichtlich der Strahlenqualität weitgehend aufgefangen werden können, indem der Ausgleichskörper 15 aus einem Material niedriger Ordnungszahl, z.B. Aluminium, gefertigt und dafür hinter dem Elektronenabsorber 7 eine Filterplatte 11 eingesetzt wird, die Röntgenquanten niedrigerer Energie bevorzugt absorbiert. Die Bauweise ist nicht nur entschieden preiswerter, sondern sie führt außerdem noch zu wesentlich kleineren und in der medizinischen Anwendung leichter zu positionierenden Geräten.The advantage of this design can be seen in particular in the fact that the omission of the complex and bulky 270 ° deflection and focusing magnet for The disadvantages associated with the electron beam 5 with regard to the radiation quality can largely be compensated for by the compensating body 15 being made from a material of low atomic number, for example aluminum, and a filter plate 11 being used behind the electron absorber 7, which preferably absorbs lower-energy X-ray quanta. The design is not only decidedly cheaper, it also leads to devices that are much smaller and easier to position in medical applications.

Claims (8)

1. Elektronenbeschleuniger mit einer evakuierten Beschleunigungsröhre, mit einem dem Elektronenstrahl ausgesetzten Target, mit einem dem Target in Strahlenrichtung nachgeschalteten Elektronenabsorber, mit einem Kollimator und mit einem zentriert zur Symmetrieachse der Ausblendöffnung des Kollimators angeordneten Ausgleichskörper, dadurch gekennzeichnet , daß dem Elektronenabsorber (7) eine aus Schwermetall, z.B. aus Blei, gefertigte Filterplatte (11) nachgeschaltet ist und der Ausgleichskörper (15) dafür aus einem Material vergleichsweise niedriger Ordnungszahl, vorzugsweise aus Aluminium, gefertigt ist.1. electron accelerator with an evacuated acceleration tube, with a target exposed to the electron beam, with an electron absorber downstream of the target in the beam direction, with a collimator and with a centering body arranged to the axis of symmetry of the aperture of the collimator, characterized in that the electron absorber (7) made of heavy metal, e.g. made of lead, filter plate (11) is connected downstream and the compensating body (15) is made of a material of comparatively low atomic number, preferably aluminum. 2. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet , daß die Filterplatte (11) zwischen dem Elektronenabsorber (7) und dem Ausgleichskörper (15) eingesetzt ist.2. Electron accelerator according to claim 1, characterized in that the filter plate (11) between the electron absorber (7) and the compensating body (15) is used. 3. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet, daß die Filterplatte (11) bei einer Elektronenenergie von 2 bis 10 MeV einen Blei-Gleichwert von mindestens 1 mm aufweist.3. Electron accelerator according to claim 1, characterized in that the filter plate (11) at an electron energy of 2 to 10 MeV has a lead equivalent of at least 1 mm. 4. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet , daß das Target (8) auf der der Beschleunigungsröhre (3) zugewandten Seite des Elektronenabsorbers (7) angebracht ist.4. Electron accelerator according to claim 1, characterized in that the target (8) on the acceleration tube (3) facing side of the electron absorber (7) is attached. 5. Elektronenbeschleuniger nach Anspruch 4, dadurch gekennzeichnet , daß der Elektronenabsorber (7) gekühlt ist.5. Electron accelerator according to claim 4, characterized in that the electron absorber (7) is cooled. 6. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet , daß die Filterplatte (11) auf der dem Target (8) abgewandten Seite des Elektronenabsorbers (7) befestigt ist.6. Electron accelerator according to claim 1, characterized in that the filter plate (11) on the side facing away from the target (8) of the electron absorber (7) is attached. 7. Elektronenbeschleuniger nach Anspruch 4, dadurch gekennzeichnet , daß der Elektronenabsorber (7) die Beschleunigungsröhre (3) auf der Strahlenaustrittsseite vakuumdicht abschließt.7. Electron accelerator according to claim 4, characterized in that the electron absorber (7) seals the acceleration tube (3) on the radiation exit side in a vacuum-tight manner. 8. Elektronenbeschleuniger nach Anspruch 1, dadurch gekennzeichnet , daß das Target (8) die Beschleunigungsröhre (3) auf der Strahlenaustrittsseite vakuumdicht abschließt.8. Electron accelerator according to claim 1, characterized in that the target (8), the acceleration tube (3) on the radiation exit side closes vacuum-tight.
EP80103661A 1979-07-03 1980-06-27 Electron accelerator for x-ray therapy Expired EP0021441B1 (en)

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DE2926883 1979-07-03
DE2926883A DE2926883A1 (en) 1979-07-03 1979-07-03 ELECTRONIC ACCELERATOR

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EP0021441A2 true EP0021441A2 (en) 1981-01-07
EP0021441A3 EP0021441A3 (en) 1981-01-14
EP0021441B1 EP0021441B1 (en) 1985-04-17

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FR2558327A1 (en) * 1984-01-17 1985-07-19 Cgr Mev MULTIREGIMUM PARTICLE ACCELERATOR
FR2728472A1 (en) * 1994-12-27 1996-06-28 Ge Medical Syst Sa X-ray radiotherapy equipment for medical treatment of tumours
FR2926924A1 (en) * 2008-01-25 2009-07-31 Thales Sa RADIOGENIC SOURCE COMPRISING AT LEAST ONE ELECTRON SOURCE ASSOCIATED WITH A PHOTOELECTRIC CONTROL DEVICE
WO2016023950A1 (en) * 2014-08-13 2016-02-18 Nikon Metrology Nv X-ray beam collimator

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DE3138731A1 (en) * 1981-09-29 1983-04-07 Siemens AG, 1000 Berlin und 8000 München MONITORING ARRANGEMENT FOR THE ACCELERATION ENERGY OF AN ELECTRON ACCELERATOR
NL9000896A (en) * 1990-04-17 1991-11-18 Philips Nv ROENTGEN RADIATION ABSORBENT FILTER.
WO2001007939A1 (en) * 1999-07-21 2001-02-01 Jmar Research, Inc. Collimator and focusing optic
WO2001007940A1 (en) 1999-07-21 2001-02-01 Jmar Research, Inc. High collection angle short wavelength radiation collimator and focusing optic
CN1822239B (en) * 2005-02-17 2010-06-23 Ge医疗系统环球技术有限公司 Filter and X-ray imaging device
US7483518B2 (en) * 2006-09-12 2009-01-27 Siemens Medical Solutions Usa, Inc. Apparatus and method for rapidly switching the energy spectrum of diagnostic X-ray beams
CN101303909B (en) * 2007-05-11 2013-03-27 Ge医疗系统环球技术有限公司 Filter unit, X ray tube unit and X ray imaging system
CN101658429A (en) * 2008-08-29 2010-03-03 Ge医疗系统环球技术有限公司 Regulating device for scattered X-ray blocking vane
CN101853710B (en) * 2009-03-31 2014-11-19 Ge医疗系统环球技术有限公司 Filter and X ray imaging device using same
US20140264065A1 (en) * 2013-03-15 2014-09-18 Varian Medical Systems, Inc. Energy degrader for radiation therapy system
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Cited By (8)

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Publication number Priority date Publication date Assignee Title
FR2558327A1 (en) * 1984-01-17 1985-07-19 Cgr Mev MULTIREGIMUM PARTICLE ACCELERATOR
EP0149571A2 (en) * 1984-01-17 1985-07-24 C.G.R. MeV Multi-operational accelerator
EP0149571A3 (en) * 1984-01-17 1985-08-21 C.G.R. Mev Multi-operational accelerator
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FR2728472A1 (en) * 1994-12-27 1996-06-28 Ge Medical Syst Sa X-ray radiotherapy equipment for medical treatment of tumours
FR2926924A1 (en) * 2008-01-25 2009-07-31 Thales Sa RADIOGENIC SOURCE COMPRISING AT LEAST ONE ELECTRON SOURCE ASSOCIATED WITH A PHOTOELECTRIC CONTROL DEVICE
WO2016023950A1 (en) * 2014-08-13 2016-02-18 Nikon Metrology Nv X-ray beam collimator
US10283228B2 (en) 2014-08-13 2019-05-07 Nikon Metrology Nv X-ray beam collimator

Also Published As

Publication number Publication date
JPS6312280B2 (en) 1988-03-18
EP0021441B1 (en) 1985-04-17
DE2926883A1 (en) 1981-01-22
EP0021441A3 (en) 1981-01-14
US4300055A (en) 1981-11-10
JPS5614199A (en) 1981-02-10
CA1139022A (en) 1983-01-04
DE3070505D1 (en) 1985-05-23

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