EP0900450A1 - Envelope for electromagnetic radiation source and method for eliminating extrafocal electromagnetic radiation - Google Patents

Envelope for electromagnetic radiation source and method for eliminating extrafocal electromagnetic radiation

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Publication number
EP0900450A1
EP0900450A1 EP97925103A EP97925103A EP0900450A1 EP 0900450 A1 EP0900450 A1 EP 0900450A1 EP 97925103 A EP97925103 A EP 97925103A EP 97925103 A EP97925103 A EP 97925103A EP 0900450 A1 EP0900450 A1 EP 0900450A1
Authority
EP
European Patent Office
Prior art keywords
radiation
chamber
opaque
source
envelope
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97925103A
Other languages
German (de)
French (fr)
Inventor
Edmond Chambron
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GE Medical Systems SCS
Original Assignee
GE Medical Systems SCS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GE Medical Systems SCS filed Critical GE Medical Systems SCS
Publication of EP0900450A1 publication Critical patent/EP0900450A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/16—Vessels; Containers; Shields associated therewith
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/16—Vessels
    • H01J2235/165—Shielding arrangements
    • H01J2235/166—Shielding arrangements against electromagnetic radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/18—Windows, e.g. for X-ray transmission

Definitions

  • the present invention relates to an envelope for a source of electromagnetic radiation, in particular an X-ray source, which has a window allowing the elimination of extrafocal radiation.
  • the invention applies very particularly in the medical field, to the X-ray imaging device.
  • the X-ray source comprises a cathode 10 and an anode 11 contained in an envelope 12 transparent to X-rays.
  • the assembly constituted by the cathode 10, the anode 11 and the envelope 12 is in turn contained in an envelope 13 opaque to X-rays, with the exception of a part located opposite the beam of X-rays emitted.
  • the anode 11 which is constituted by a window 15 made of material transparent to X-rays.
  • the space between the transparent envelope 12 and the opaque envelope 13 is filled with oil 16 serving for insulation and upon cooling of the X-ray source.
  • the cathode 10 emits electronic radiation which strikes the rotating anode 1 1 which re-emits an X-ray beam from a focal surface.
  • the beam of X-rays emitted by the anode 1 1 is constituted by a radiation from this focal surface, but also by extrafocal parasitic radiation. This extrafocal parasitic radiation must be eliminated, preferably as close as possible to the emission source.
  • the diameter of the opening 31 is a compromise between obtaining a large field and eliminating the extrafocal radiation.
  • the diameter of the opening 31 is no longer adapted to the beam of X-rays emitted and in particular no longer ensures the elimination of the extrafocal radiation.
  • the present invention therefore aims to provide an envelope for a source of electromagnetic radiation, in particular X-rays, which allows the removal of the conical element or diaphragm and extrafocal fingers for the elimination of extrafocal radiation.
  • an envelope for a source of electromagnetic radiation in particular X-rays, which comprises a window made of a material transparent to electromagnetic radiation, the window comprising at least one chamber in which can moving an opaque material to electromagnetic radiation, this chamber being configured so that the opaque material can be introduced from outside the chamber and that inside the chamber this opaque material surrounds a passageway of an electromagnetic radiation beam in such a way that the surface of the radiation passage area varies as a function of the volume of opaque material in the chamber, by means of which extraneous focal radiation is removed from the beam.
  • the chamber comprises a first pipe wound on itself in the form of a spiral.
  • the chamber comprises a second spiral-shaped pipe, juxtaposed with the first pipe in a direction perpendicular to the planes on which the openings of the first and second pipes, this first and this second pipes being offset with respect to each other so that the turns of a spiral cover the space between the turns of the other spiral, so as to ensure total opacity to radiation in the part of the spirals which is crossed by the opaque material.
  • the present invention also relates to a method of removing extrafocal radiation from an electromagnetic radiation beam by means of an electromagnetic radiation source envelope window as defined above.
  • the electromagnetic radiation beam is an X-ray beam and the source is an X-ray source.
  • Figure 1 - a partial view of the window area of an X-ray source, as well as the crosstalk and the extrafocal radiation elimination system, of an X-ray source of the prior art;
  • Figure 2 - a sectional view of an embodiment of an X-ray source envelope window according to the present invention
  • Figure 3 a schematic view of a spiral channel of an X-ray source window chamber according to the invention.
  • FIG. 4 a schematic view of a spiral channel of an X-ray source envelope window according to the invention, connected to a device for controlling the movement of the material opaque to X-rays.
  • FIG. 1 shows the part of X-ray emission from an X-ray source of the prior art as well as the part of the diaphragm of this source.
  • the X-ray source comprises a cathode 10 and a rotating anode 11 contained in an envelope 12 transparent to X-rays.
  • the assembly is itself enclosed in an envelope 13 provided with a jacket 14 made of opaque material X-ray, for example lead, with the exception of an area located opposite the anode 11 which is constituted by a window 15 made of a material transparent to X-rays.
  • the interval between the envelope 12 and the protective casing 13 and the window 15 is filled with oil ensuring the cooling and the high voltage electrical isolation of the source X-rays. Consequently, the envelope 13 must both seal against the oil contained in the gap between this envelope 13 and the envelope 12 and ensure that the X-ray will not be emitted only through the window 15.
  • the cathode 10 emits an electron beam which strikes the focal track of the rotating anode 1 1 which in turn emits a beam of X-rays in the direction of window 15.
  • the X-ray beam emitted by the anode 1 1 is shaped by means of a diaphragm 30 of material opaque to X-rays whose opening 31 is dimensioned to obtain a beam of X-ray from the anode focus and intercept the X-ray emitted by the source outside the focus or extrafocal radiation.
  • Extrafocal, parasitic radiation must be eliminated because it affects the quality of the image subsequently obtained. It is also desirable to be able to vary the dimension of the focal surface of the anode and therefore the geometry of the X-ray beam.
  • the diaphragm 30 being a separate part from the window 15, must be placed outside this window and it is therefore not possible to eliminate the extrafocal radiation as close as possible to the focal emission surface of the beam for the quality of the final image obtained, it is particularly advantageous to be able to eliminate the extrafocal radiation as close as possible to the focal surface of the source.
  • the use of opaque fingers 32 requires a complex mechanical linkage 33 to size the opening 31 of the diaphragm of the X-ray beam.
  • FIG. 2 shows a window 15 of an X-ray source envelope according to the invention.
  • This window 15 generally has the shape of a frustoconical cup and has a bottom wall 17, a side wall 18 ending in a flange 19 for mounting in the protective envelope 13.
  • This window 15 is made up of X-ray transparent material.
  • this window 15 comprises an internal chamber configured to allow the movement of an opaque material which is introduced from outside the chamber in such a way that the area of the passage area of the X-ray beam varies in as a function of the volume of the opaque material in the chamber, thus eliminating the extraneous extraneous focal radiation.
  • this chamber comprises an annular cavity 20 formed in the side wall 18 and connected at its lower end to a control means 25 for moving material opaque to X-rays.
  • This annular chamber 20 is connected at its upper end to the outermost turn of each of two spiral pipes 22, 23 arranged in the bottom wall 17 of the window by means of pipes 21.
  • the spiral pipes 22 and 23 are arranged in the bottom wall 17 in juxtaposed planes parallel to the bottom wall 17. As shown, the turns of the two pipes 22, 23 are offset from one another so as to jointly practically cover the entire surface of the bottom wall 17.
  • one could use a single spiral line, preferably a spiral line with contiguous turns, as shown in Figure 3. would urge also use more than two stacked spiral lines.
  • each of these spiral pipes 22 and 23 is also connected by a pipe 24 formed in the window to the device for controlling the opaque material.
  • the material opaque to X-rays for example mercury, is introduced by means of the control device 25 into the annular chamber 20, then into the external turns of the spiral pipes 22 and 23 in the direction of the center of these spiral pipes so leaving a central passage of appropriate size for the X-ray beam.
  • the turns of the spiral conduits 22 and 23 forming the central passage for the X-ray beam are filled, also by means of the control device 25, with a liquid transparent to X-rays, for example alcohol.
  • the diaphragm function being performed in the window of the external envelope of the X-ray source itself, it is possible to eliminate this extrafocal radiation very close to the focal surface of the source.
  • FIG. 4 shows schematically a spiral pipe connected to a device for controlling the movement of the opaque material 25 which is particularly recommended for the present invention.
  • This control device 25 comprises an enclosure in which is disposed a piston 26 movable in translation dividing the enclosure into a first chamber 27 and a second chamber 28.
  • the first chamber 27 is connected by a pipe 21 to the external coil, for example of the spiral pipe 22.
  • the second chamber 28 is itself connected by a pipe 24 to the innermost turn, by example of the spiral pipe 22.
  • the chamber 27 is filled with material opaque to X-rays, for example mercury, while the chamber 28 is filled with a material transparent to X-rays, for example alcohol.
  • the piston 26 may for example be a piston displaceable by means of a magnet 29.
  • the piston 26 comprises two magnetically displaceable plates, spaced from one another, to define a space generally filled with air in the purpose of absorbing thermal expansions.
  • the piston 26 is also moved, either to the right or to the left, thus introducing more or less into the spiral pipe 22 X-ray opaque product.
  • it is easy to size the central passage of the X-ray beam and eliminate the extrafocal stray radiation according to the intended use for the X-ray source. It can also be used as a movement control device of the material opaque to X-rays a peristaltic pump in place of the device described above.

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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)
  • X-Ray Techniques (AREA)

Abstract

The envelope comprises a window made of material transparent to the radiation emitted by the source that comprises at least one chamber (20, 22, 23) in which can be moved a material impervious to the electromagnetic radiation, the chamber being shaped such that the material impervious to the radiation can be inserted from outside the chamber and that inside the chamber the material impervious to the radiation surrounds a radiation beam passage zone, such that the surface of the beam passage zone vaires according to the volume of the impervious material in the chamber, thus eliminating the extrafocal stray radiation. The invention is useful in X-ray imaging apparatus.

Description

Enveloppe pour source de rayonnement électromagnétique et procédé pour l'élimination du rayonnement électromagnétique extrafocal.Enclosure for source of electromagnetic radiation and method for eliminating extrafocal electromagnetic radiation.
La présente invention concerne une enveloppe pour source de rayonnement électromagnétique, en particulier une source de rayons X, qui comporte une fenêtre permettant l'élimination du rayonnement extrafocal. L'invention s'applique tout particulièrement dans le domaine médical, au dispositif d'imagerie par rayons X.The present invention relates to an envelope for a source of electromagnetic radiation, in particular an X-ray source, which has a window allowing the elimination of extrafocal radiation. The invention applies very particularly in the medical field, to the X-ray imaging device.
Comme le montre la figure 1, qui représente la partie de la fenêtre d'une source de rayons X de l'art antérieur, la source de rayons X comprend une cathode 10 et une anode 1 1 contenues dans une enveloppe 12 transparente aux rayons X. L'ensemble constitué par la cathode 10, l'anode 11 et l'enveloppe 12 est à son tour contenu dans une enveloppe 13 opaque aux rayons X, à l'exception d'une partie située en face du faisceau de rayons X émis par l'anode 1 1, qui est constituée par une fenêtre 15 en matériau transparent aux rayons X. L'intervalle entre l'enveloppe transparente 12 et l'enveloppe opaque 13 est rempli par de l'huile 16 servant à l'isolation et au refroidissement de la source de rayons X.As shown in FIG. 1, which represents the part of the window of an X-ray source of the prior art, the X-ray source comprises a cathode 10 and an anode 11 contained in an envelope 12 transparent to X-rays. The assembly constituted by the cathode 10, the anode 11 and the envelope 12 is in turn contained in an envelope 13 opaque to X-rays, with the exception of a part located opposite the beam of X-rays emitted. by the anode 11, which is constituted by a window 15 made of material transparent to X-rays. The space between the transparent envelope 12 and the opaque envelope 13 is filled with oil 16 serving for insulation and upon cooling of the X-ray source.
Comme cela est bien connu, la cathode 10 émet un rayonnement électronique qui vient frapper l'anode tournante 1 1 qui réémet un faisceau de rayons X à partir d'une surface focale. Le faisceau de rayons X émis par l'anode 1 1 est constitué par un rayonnement issu de cette surface focale, mais également par des rayonnements parasites extrafocaux. Ces rayonnements parasites extrafocaux doivent être éliminés, de préférence aussi près que possible de la source d'émission.As is well known, the cathode 10 emits electronic radiation which strikes the rotating anode 1 1 which re-emits an X-ray beam from a focal surface. The beam of X-rays emitted by the anode 1 1 is constituted by a radiation from this focal surface, but also by extrafocal parasitic radiation. This extrafocal parasitic radiation must be eliminated, preferably as close as possible to the emission source.
De manière classique, pour éliminer ces rayonnements extrafocaux, on disposait comme le montre la figure 1 un élément conique 30 ou diaphragme en matériau opaque aux rayons X, par exemple en plomb, pourvu d'une ouverture centrale 31 pour le passage du faisceau de rayons X. Le diamètre de l'ouverture 31 est un compromis entre l'obtention d'un grand champ et l'élimination du rayonnement extrafocal. Toutefois, dans certains cas, il était souhaitable d'obtenir des champs plus petits, par exemple, en utilisant une surface focale plus petite. Mais, dans ce cas, le diamètre de l'ouverture 31 n'est plus adapté au faisceau de rayons X émis et en particulier n'assure plus l'élimination du rayonnement extrafocal. On utilisait alors classiquement pour éliminer le rayonnement extrafocal des doigts extrafocaux 32, en matériau opaque aux rayons X, par exemple en plomb, qui étaient amenés en position à la fois latéralement et longitudinalement par une tringlerie 33, conformément au champ voulu. Un tel système est mécaniquement complexe, coûteux, et d'autre part, ne permet pas d'effectuer la collimation aussi près que possible du foyer du faisceau de rayons X.Conventionally, to eliminate these extrafocal radiation, there was, as shown in FIG. 1, a conical element 30 or diaphragm made of an material opaque to X-rays, for example lead, provided with a central opening 31 for the passage of the beam of rays. X. The diameter of the opening 31 is a compromise between obtaining a large field and eliminating the extrafocal radiation. However, in some cases it was desirable to obtain smaller fields, for example, using a smaller focal area. However, in this case, the diameter of the opening 31 is no longer adapted to the beam of X-rays emitted and in particular no longer ensures the elimination of the extrafocal radiation. It was then conventionally used to eliminate the extrafocal radiation from the extrafocal fingers 32, made of material opaque to X-rays, for example lead, which were brought into position both laterally and longitudinally by a linkage 33, in accordance with the desired field. Such a system is mechanically complex, expensive, and on the other hand, does not allow collimation to be carried out as close as possible to the focus of the X-ray beam.
La présente invention a donc pour but de fournir une enveloppe pour source de rayonnement électromagnétique, en particulier de rayons X, qui permet la suppression de l'élément conique ou diaphragme et des doigts extrafocaux pour l'élimination du rayonnement extrafocal.The present invention therefore aims to provide an envelope for a source of electromagnetic radiation, in particular X-rays, which allows the removal of the conical element or diaphragm and extrafocal fingers for the elimination of extrafocal radiation.
On atteint le but ci-dessus selon l'invention, en réalisant une enveloppe pour source de rayonnement électromagnétique, en particulier de rayons X, qui comprend une fenêtre en un matériau transparent au rayonnement électromagnétique, la fenêtre comprenant au moins une chambre dans laquelle peut se déplacer un matériau opaque au rayonnement électromagnétique, cette chambre étant configurée pour que le matériau opaque puisse être introduit à partir de l'extérieur de la chambre et qu'à l'intérieur de la chambre ce matériau opaque entoure une zone de passage d'un faisceau de rayonnement électromagnétique de telle manière que la surface de la zone de passage du rayonnement varie en fonction du volume de matériau opaque dans la chambre, grâce à quoi on élimine du faisceau le rayonnement extrafocal parasite.The above object is achieved according to the invention, by producing an envelope for a source of electromagnetic radiation, in particular X-rays, which comprises a window made of a material transparent to electromagnetic radiation, the window comprising at least one chamber in which can moving an opaque material to electromagnetic radiation, this chamber being configured so that the opaque material can be introduced from outside the chamber and that inside the chamber this opaque material surrounds a passageway of an electromagnetic radiation beam in such a way that the surface of the radiation passage area varies as a function of the volume of opaque material in the chamber, by means of which extraneous focal radiation is removed from the beam.
Dans une réalisation recommandée, la chambre comprend une première canalisation enroulée sur elle-même en forme de spirale.In a recommended embodiment, the chamber comprises a first pipe wound on itself in the form of a spiral.
De préférence, la chambre comprend une seconde canalisation en forme de spirale, juxtaposée à la première canalisation dans une direction perpendiculaire aux plans sur lesquels sont situées les ouvertures des première et seconde canalisations, cette première et cette seconde canalisations étant décalées l'une par rapport à l'autre de sorte que les spires d'une spirale couvrent l'espace entre les spires de l'autre spirale, de façon à assurer l'opacité totale au rayonnement dans la partie des spirales qui est traversée par le matériau opaque.Preferably, the chamber comprises a second spiral-shaped pipe, juxtaposed with the first pipe in a direction perpendicular to the planes on which the openings of the first and second pipes, this first and this second pipes being offset with respect to each other so that the turns of a spiral cover the space between the turns of the other spiral, so as to ensure total opacity to radiation in the part of the spirals which is crossed by the opaque material.
La présente invention concerne également un procédé d'élimination du rayonnement extrafocal d'un faisceau de rayonnement électromagnétique au moyen d'une fenêtre d'enveloppe de source de rayonnement électromagnétique telle que définie ci-dessus. De préférence, le faisceau de rayonnement électromagnétique est un faisceau de rayons X et la source une source de rayons X.The present invention also relates to a method of removing extrafocal radiation from an electromagnetic radiation beam by means of an electromagnetic radiation source envelope window as defined above. Preferably, the electromagnetic radiation beam is an X-ray beam and the source is an X-ray source.
La suite de la description se réfère aux figures annexées qui représentent respectivement :The following description refers to the appended figures which respectively represent:
Figure 1 - une vue partielle de la zone de la fenêtre d'une source de rayons X, ainsi que du diaphgrame et du système d'élimination du rayonnement extrafocal, d'une source de rayons X de l'art antérieur;Figure 1 - a partial view of the window area of an X-ray source, as well as the crosstalk and the extrafocal radiation elimination system, of an X-ray source of the prior art;
Figure 2 - une vue en coupe d'une réalisation d'une fenêtre d'enveloppe de source de rayons X selon la présente invention;Figure 2 - a sectional view of an embodiment of an X-ray source envelope window according to the present invention;
Figure 3 - une vue schématique d'une canalisation en spirale de chambre de fenêtre de source de rayons X selon l'invention; etFigure 3 - a schematic view of a spiral channel of an X-ray source window chamber according to the invention; and
Figure 4 - une vue schématique d'une canalisation en spirale de fenêtre d'enveloppe de source de rayons X selon l'invention, reliée à un dispositif de commande de déplacement du matériau opaque aux rayons X. On a représenté à la figure 1 la partie d'émission des rayons X d'une source de rayons X de l'art antérieur ainsi que la partie du diaphragme de cette source. De manière classique, la source de rayons X comprend une cathode 10 et une anode tournante 1 1 contenues dans une enveloppe 12 transparente aux rayons X. L'ensemble est lui-même enfermé dans une enveloppe 13 pourvue d'une chemise 14 en matériau opaque aux rayons X, par exemple en plomb, à l'exception d'une zone située en face de l'anode 1 1 qui est constituée par une fenêtre 15 en un matériau transparent aux rayons X. L'intervalle entre l'enveloppe 12 et l'enveloppe de protection 13 et la fenêtre 15 est rempli d'huile assurant le refroidissement et l'isolement électrique haute tension de la source de rayons X. Par conséquent, l'enveloppe 13 doit à la fois assurer l'etanchéite vis-à-vis de l'huile contenue dans l'intervalle entre cette enveloppe 13 et l'enveloppe 12 et assurer que le rayonnement X ne sera émis qu'à travers la fenêtre 15. Comme cela est bien connu, la cathode 10 émet un faisceau d'électron qui vient frapper la piste focale de l'anode tournante 1 1 qui émet à son tour un faisceau de rayons X en direction de la fenêtre 15.Figure 4 - a schematic view of a spiral channel of an X-ray source envelope window according to the invention, connected to a device for controlling the movement of the material opaque to X-rays. FIG. 1 shows the part of X-ray emission from an X-ray source of the prior art as well as the part of the diaphragm of this source. Conventionally, the X-ray source comprises a cathode 10 and a rotating anode 11 contained in an envelope 12 transparent to X-rays. The assembly is itself enclosed in an envelope 13 provided with a jacket 14 made of opaque material X-ray, for example lead, with the exception of an area located opposite the anode 11 which is constituted by a window 15 made of a material transparent to X-rays. The interval between the envelope 12 and the protective casing 13 and the window 15 is filled with oil ensuring the cooling and the high voltage electrical isolation of the source X-rays. Consequently, the envelope 13 must both seal against the oil contained in the gap between this envelope 13 and the envelope 12 and ensure that the X-ray will not be emitted only through the window 15. As is well known, the cathode 10 emits an electron beam which strikes the focal track of the rotating anode 1 1 which in turn emits a beam of X-rays in the direction of window 15.
Comme le montre la figure 1 , de façon classique, le faisceau de rayons X émis par l'anode 1 1 est conformé au moyen d'un diaphragme 30 en matériau opaque aux rayons X dont l'ouverture 31 est dimensionnée pour obenir un faisceau de rayonnement X issu du foyer de l'anode et intercepter le rayonnement X émis par la source hors du foyer ou rayonnement extrafocal. Le rayonnement extrafocal, parasite, doit être éliminé car il nuit à la qualité de l'image ultérieurement obtenue. Il est en outre souhaitable de pouvoir faire varier la dimension de la surface focale de l'anode et par conséquent la géométrie du faisceau de rayons X. De ce fait, afin d'éliminer le rayonnement extrafocal, il est nécessaire de modifier la dimension de l'ouverture du diaphragme 30 en fonction de la dimension de la surface focale ainsi que la collimation du faisceau de rayons X. De manière classique, afin d'adapter l'ouverture du diaphragme 30 au faisceau de rayons X et pouvoir éliminer le rayonnement extrafocal, on prévoit des doigts mobiles 32 en matériau opaque aux rayons X qui sont manoeuvres au moyen d'une tringlerie complexe 33 afin de dimensionner l'ouverture 31 en fonction de la surface focale et de la surface voulue pour l'image finale. Cet agencement de l'art antérieur que l'on vient de décrire présente plusieurs inconvénients. Tout d'abord, le diaphragme 30 étant une pièce distincte de la fenêtre 15, doit être placé extérieurement à cette fenêtre et il n'est donc pas possible d'éliminer le rayonnement extrafocal au plus près de la surface focale d'émission du faisceau de rayons X. Pour la qualité de l'image finale obtenue, il est particulièrement intéressant de pouvoir éliminer le rayonnement extrafocal au plus près de la surface focale de la source. D'autre part, l'emploi de doigts opaques 32 nécessite une tringlerie mécanique complexe 33 pour dimensionner l'ouverture 31 du diaphragme du faisceau de rayons X.As shown in Figure 1, conventionally, the X-ray beam emitted by the anode 1 1 is shaped by means of a diaphragm 30 of material opaque to X-rays whose opening 31 is dimensioned to obtain a beam of X-ray from the anode focus and intercept the X-ray emitted by the source outside the focus or extrafocal radiation. Extrafocal, parasitic radiation must be eliminated because it affects the quality of the image subsequently obtained. It is also desirable to be able to vary the dimension of the focal surface of the anode and therefore the geometry of the X-ray beam. Therefore, in order to eliminate the extrafocal radiation, it is necessary to modify the dimension of the aperture of the diaphragm 30 as a function of the dimension of the focal surface as well as the collimation of the X-ray beam. Conventionally, in order to adapt the aperture of the diaphragm 30 to the X-ray beam and to be able to eliminate the extrafocal radiation , mobile fingers 32 made of material opaque to X-rays are provided, which are operated by means of a complex linkage 33 in order to size the opening 31 as a function of the focal area and the area desired for the final image. This arrangement of the prior art which has just been described has several drawbacks. First of all, the diaphragm 30 being a separate part from the window 15, must be placed outside this window and it is therefore not possible to eliminate the extrafocal radiation as close as possible to the focal emission surface of the beam for the quality of the final image obtained, it is particularly advantageous to be able to eliminate the extrafocal radiation as close as possible to the focal surface of the source. On the other hand, the use of opaque fingers 32 requires a complex mechanical linkage 33 to size the opening 31 of the diaphragm of the X-ray beam.
Selon l'invention, on remédie à ces inconvénients en prévoyant une fenêtre servant également de diaphragme pour l'élimination du rayonnement extrafocal. Du fait que la fenêtre elle-même assure la fonction de diaphragme, il est possible de placer ce diaphragme plus près de la surface focale du faisceau de rayons X. D'autre part, la nouvelle fenêtre selon l'invention permet simplement de dimensionner l'ouverture de passage du faisceau de rayons X sans nécessiter un système mécanique de tringlerie complexe. On a représenté à la figure 2 une fenêtre 15 d'enveloppe de source de rayons X selon l'invention. Cette fenêtre 15 a de manière générale la forme d'une coupelle tronconique et comporte une paroi de fond 17, une paroi latérale 18 se terminant par une bride 19 pour son montage dans l'enveloppe de protection 13. Cette fenêtre 15 est constituée d'un matériau transparent aux rayons X.According to the invention, these drawbacks are remedied by providing a window also serving as a diaphragm for the elimination of extrafocal radiation. Because the window itself performs the diaphragm function, it is possible to place this diaphragm closer to the focal surface of the X-ray beam. On the other hand, the new window according to the invention simply makes it possible to size the opening passage of the X-ray beam without requiring a complex mechanical linkage system. FIG. 2 shows a window 15 of an X-ray source envelope according to the invention. This window 15 generally has the shape of a frustoconical cup and has a bottom wall 17, a side wall 18 ending in a flange 19 for mounting in the protective envelope 13. This window 15 is made up of X-ray transparent material.
Selon l'invention, cette fenêtre 15 comprend une chambre interne configurée pour permettre le déplacement d'un matériau opaque qui est introduit depuis l'extérieur de la chambre de telle manière que la surface de la zone de passage du faisceau de rayons X varie en fonction du volume du matériau opaque dans la chambre pour ainsi éliminer du faisceau le rayonnement extrafocal parasite.According to the invention, this window 15 comprises an internal chamber configured to allow the movement of an opaque material which is introduced from outside the chamber in such a way that the area of the passage area of the X-ray beam varies in as a function of the volume of the opaque material in the chamber, thus eliminating the extraneous extraneous focal radiation.
Dans la réalisation représentée, cette chambre comprend une cavité annulaire 20 ménagée dans la paroi latérale 18 et reliée à son extrémité inférieure à un moyen de commande 25 de déplacement de matériau opaque aux rayons X. Cette chambre annulaire 20 est reliée à son extrémité supérieure à la spire la plus externe de chacune de deux canalisations en spirale 22, 23 disposées dans la paroi de fond 17 de la fenêtre au moyen de tubulures 21. Les canalisations en spirale 22 et 23 sont disposées dans la paroi de fond 17 dans des plans juxtaposés parallèles à la paroi de fond 17. Comme représenté, les spires des deux canalisations 22, 23 sont décalées les unes par rapport aux autres de manière à conjointement pratiquement recouvrir la totalité de la surface de la paroi de fond 17. Bien évidemment, on pourrait utiliser une seule canalisation en spirale, de préférence une canalisation en spirale à spires jointives, comme représentée à la figure 3. On pourrait également utiliser plus de deux canalisations en spirale superposées. La spire la plus interne de chacune de ces canalisations en spirale 22 et 23 est également reliée par une conduite 24 ménagée dans la fenêtre au dispositif de commande du matériau opaque. Bien évidemment, on peut si on le souhaite supprimer la cavité annulaire 20 et la remplacer par deux conduites. Le matériau opaque aux rayons X, par exemple du mercure, est introduit au moyen du dispositif de commande 25 dans la chambre annulaire 20, puis dans les spires externes des canalisations en spirale 22 et 23 en direction du centre de ces canalisations en spirale de manière à laisser un passage central de dimension appropriée pour le faisceau de rayons X. Les spires des canalisations en spirale 22 et 23 formant le passage central pour le faisceau de rayons X sont remplies, également au moyen du dispositif de commande 25, d'un liquide transparent aux rayons X, par exemple de l'alcool. Les spires des canalisations en spirale 22 et 23 remplies de matériau opaque, et entourant les spires centrales remplies de matériau transparent aux rayons X, forment donc un diaphragme opaque aux rayons X permettant d'éliminer le rayonnement extrafocal. En fonction de la quantité de matériau opaque introduit dans les spires des canalisations 22 et 23, on peut donc dimensionner le passage central transparent aux rayons X et éliminer facilement le rayonnement extrafocal en fonction de la dimension de la surface focale de la source de rayons X. D'autre part, la fonction de diaphragme étant réalisée dans la fenêtre de l'enveloppe externe de la source de rayons X elle-même, il est possible de réaliser cette élimination du rayonnement extrafocal très près de la surface focale de la source.In the embodiment shown, this chamber comprises an annular cavity 20 formed in the side wall 18 and connected at its lower end to a control means 25 for moving material opaque to X-rays. This annular chamber 20 is connected at its upper end to the outermost turn of each of two spiral pipes 22, 23 arranged in the bottom wall 17 of the window by means of pipes 21. The spiral pipes 22 and 23 are arranged in the bottom wall 17 in juxtaposed planes parallel to the bottom wall 17. As shown, the turns of the two pipes 22, 23 are offset from one another so as to jointly practically cover the entire surface of the bottom wall 17. Obviously, one could use a single spiral line, preferably a spiral line with contiguous turns, as shown in Figure 3. would urge also use more than two stacked spiral lines. The innermost turn of each of these spiral pipes 22 and 23 is also connected by a pipe 24 formed in the window to the device for controlling the opaque material. Obviously, it is possible, if desired, to remove the annular cavity 20 and replace it with two pipes. The material opaque to X-rays, for example mercury, is introduced by means of the control device 25 into the annular chamber 20, then into the external turns of the spiral pipes 22 and 23 in the direction of the center of these spiral pipes so leaving a central passage of appropriate size for the X-ray beam. The turns of the spiral conduits 22 and 23 forming the central passage for the X-ray beam are filled, also by means of the control device 25, with a liquid transparent to X-rays, for example alcohol. The turns of the spiral pipes 22 and 23 filled with opaque material, and surrounding the central turns filled with material transparent to X-rays, therefore form an opaque diaphragm to X rays making it possible to eliminate the extrafocal radiation. Depending on the quantity of opaque material introduced into the turns of the lines 22 and 23, it is therefore possible to size the transparent central passage with X-rays and easily eliminate the extrafocal radiation as a function of the dimension of the focal surface of the X-ray source. On the other hand, the diaphragm function being performed in the window of the external envelope of the X-ray source itself, it is possible to eliminate this extrafocal radiation very close to the focal surface of the source.
On a représenté à la figure 4, schématiquement, une canalisation en spirale reliée à un dispositif de commande de déplacement du matériau opaque 25 particulièrement recommandé pour la présente invention. Ce dispositif de commande 25 comprend une enceinte dans laquelle est disposé un piston 26 mobile en translation divisant l'enceinte en une première chambre 27 et une seconde chambre 28. La première chambre 27 est reliée par une conduite 21 à la spire externe, par exemple de la canalisation en spirale 22. La seconde chambre 28 est elle-même reliée par une conduite 24 à la spire la plus interne, par exemple de la canalisation en spirale 22. La chambre 27 est remplie du matériau opaque aux rayons X, par exemple du mercure, cependant que la chambre 28 est remplie avec un matériau transparent aux rayons X, par exemple de l'alcool. Le piston 26 peut être par exemple un piston déplaçable au moyen d'un aimant 29. Comme représenté, le piston 26 comporte deux plaques magnétiquement déplaçables, écartées l'une de l'autre, pour définir un espace généralement rempli d'air dans le but d'absorber les dilatations thermiques. Comme cela apparaît immédiatement, en déplaçant l'aimant, soit vers la droite, soit vers la gauche, on déplace également le piston 26, soit vers la droite, soit vers la gauche, introduisant ainsi dans la canalisation en spirale 22 plus ou moins de produit opaque aux rayons X. Ainsi, on peut aisément dimensionner le passage central du faisceau de rayons X et éliminer le rayonnement parasite extrafocal en fonction de l'utilisation envisagée pour la source de rayons X. On peut également utiliser comme dispositif de commande de déplacement du matériau opaque aux rayons X une pompe péristaltique à la place du dispositif décrit ci- dessus. FIG. 4 shows schematically a spiral pipe connected to a device for controlling the movement of the opaque material 25 which is particularly recommended for the present invention. This control device 25 comprises an enclosure in which is disposed a piston 26 movable in translation dividing the enclosure into a first chamber 27 and a second chamber 28. The first chamber 27 is connected by a pipe 21 to the external coil, for example of the spiral pipe 22. The second chamber 28 is itself connected by a pipe 24 to the innermost turn, by example of the spiral pipe 22. The chamber 27 is filled with material opaque to X-rays, for example mercury, while the chamber 28 is filled with a material transparent to X-rays, for example alcohol. The piston 26 may for example be a piston displaceable by means of a magnet 29. As shown, the piston 26 comprises two magnetically displaceable plates, spaced from one another, to define a space generally filled with air in the purpose of absorbing thermal expansions. As it immediately appears, by moving the magnet, either to the right or to the left, the piston 26 is also moved, either to the right or to the left, thus introducing more or less into the spiral pipe 22 X-ray opaque product. Thus, it is easy to size the central passage of the X-ray beam and eliminate the extrafocal stray radiation according to the intended use for the X-ray source. It can also be used as a movement control device of the material opaque to X-rays a peristaltic pump in place of the device described above.

Claims

REVENDICATIONS
1. Enveloppe pour source de rayonnement électromagnétique, comprenant une fenêtre (15) en un matériau transparent au rayonnement émis par la source, caractérisée en ce que la fenêtre comprend au moins une chambre (20, 22, 23), dans laquelle peut se déplacer un matériau opaque au rayonnement électromagnétique, cette chambre (20, 22, 23) étant configurée pour que le matériau opaque au rayonnement puisse être introduit à partir de l'extérieur de la chambre et qu'à l'intérieur de la chambre ce matériau opaque au rayonnement entoure une zone de passage d'un faisceau de rayonnement de telle manière que la surface de la zone de passage du faisceau varie en fonction du volume du matériau opaque dans la chambre, grâce à quoi on élimine du faisceau le rayonnement extrafocal parasite.1. Enclosure for source of electromagnetic radiation, comprising a window (15) made of a material transparent to radiation emitted by the source, characterized in that the window comprises at least one chamber (20, 22, 23), in which can move a material opaque to electromagnetic radiation, this chamber (20, 22, 23) being configured so that the material opaque to radiation can be introduced from outside the chamber and that inside this chamber this opaque material to the radiation surrounds a zone of passage of a beam of radiation in such a way that the surface of the zone of passage of the beam varies as a function of the volume of the opaque material in the chamber, thanks to which the parasitic extrafocal radiation is eliminated from the beam.
2. Enveloppe selon la revendication 1 , caractérisée en ce que la chambre comprend une première canalisation (22) enroulée sur elle- même en forme de spirale.2. Envelope according to claim 1, characterized in that the chamber comprises a first pipe (22) wound on itself in the form of a spiral.
3. Enveloppe selon la revendication 2, caractérisée en ce que la chambre comprend une seconde canalisation (23) en forme de spirale, juxtaposée à la première canalisation (22) dans une direction perpendiculaire aux plans sur lesquels sont situées les ouvertures des première et seconde canalisations, cette première et cette seconde canalisations étant décalées l'une par rapport à l'autre de sorte que les spires d'une spirale couvrent l'espace entre les spires de l'autre spirale, de façon à assurer l'opacité totale au rayonnement dans la partie des spirales qui est traversée par le matériau opaque. 3. Envelope according to claim 2, characterized in that the chamber comprises a second pipe (23) in the form of a spiral, juxtaposed with the first pipe (22) in a direction perpendicular to the planes on which the openings of the first and second are located pipes, this first and this second pipes being offset with respect to each other so that the turns of a spiral cover the space between the turns of the other spiral, so as to ensure total opacity at radiation in the part of the spirals which is crossed by the opaque material.
4. Enveloppe selon l'une quelconque des revendications 1 à 3, caractérisée en ce qu'une partie du volume de la chambre (20, 22, 23) est occupée par le matériau opaque au rayonnement et le volume restant est occupé par un fluide transparent au rayonnement.4. Envelope according to any one of claims 1 to 3, characterized in that part of the volume of the chamber (20, 22, 23) is occupied by the material opaque to radiation and the remaining volume is occupied by a fluid transparent to radiation.
5. Enveloppe selon la revendication 4, caractérisée en ce que le matériau opaque au rayonnement est contenu à la périphérie de la chambre (20, 22, 23) et le fluide transparent au rayonnement en son centre.5. Envelope according to claim 4, characterized in that the material opaque to radiation is contained at the periphery of the chamber (20, 22, 23) and the fluid transparent to radiation at its center.
6. Enveloppe selon l'une quelconque des revendications 1 à 5, caractérisée en ce que le matériau opaque au rayonnement est du mercure liquide.6. Envelope according to any one of claims 1 to 5, characterized in that the material opaque to radiation is liquid mercury.
7. Enveloppe selon la revendication 4 ou 5, caractérisée en ce que le fluide transparent au rayonnement est de l'alcool. 7. Envelope according to claim 4 or 5, characterized in that the fluid transparent to radiation is alcohol.
8. Enveloppe selon l'une quelconque des revendications précédentes, caractérisée en ce que la fenêtre a la forme d'une coupelle tronconique ayant une paroi de fond (17) et une paroi latérale (18), ladite chambre (20, 22, 23) comprenant au moins une canalisation enroulée en spirale (22) disposée dans la paroi de fond (17) et une cavité annulaire (20) disposée dans la paroi latérale (18) et communiquant avec la (ou les) canalisation(s) en spirale (22, 23).8. Envelope according to any one of the preceding claims, characterized in that the window has the shape of a frustoconical cup having a bottom wall (17) and a side wall (18), said chamber (20, 22, 23 ) comprising at least one spirally wound pipe (22) arranged in the bottom wall (17) and an annular cavity (20) arranged in the side wall (18) and communicating with the pipe (s) in a spiral (22, 23).
9. Enveloppe selon l'une quelconque des revendications précédentes, caractérisée en ce que la source de rayonnement électro¬ magnétique est une source de rayons X. 9. Envelope according to any one of the preceding claims, characterized in that the source of electro-magnetic radiation is a source of X-rays.
10. Procédé pour éliminer le rayonnement extrafocal d'un faisceau de rayonnement électromagnétique émis par une source, caractérisé en ce qu'il consiste à munir l'enveloppe de la source de rayonnement électromagnétique d'une fenêtre selon l'une quelconque des revendications 1 à 9 et introduire dans la chambre (20, 22, 23) la quantité voulue de matériau opaque au rayonnement pour absorber le rayonnement extrâfocal. 10. Method for eliminating extrafocal radiation from a beam of electromagnetic radiation emitted by a source, characterized in that it consists in providing the envelope of the source of electromagnetic radiation with a window according to any one of claims 1 to 9 and introducing into the chamber (20, 22, 23) the desired quantity of material opaque to the radiation to absorb the extra-focal radiation.
EP97925103A 1996-05-20 1997-05-20 Envelope for electromagnetic radiation source and method for eliminating extrafocal electromagnetic radiation Withdrawn EP0900450A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9606228A FR2748848B1 (en) 1996-05-20 1996-05-20 ENCLOSURE FOR ELECTROMAGNETIC RADIATION SOURCE AND METHOD FOR ELIMINATION OF EXTRAFOCAL ELECTROMAGNETIC RADIATION
FR9606228 1996-05-20
PCT/FR1997/000880 WO1997044809A1 (en) 1996-05-20 1997-05-20 Envelope for electromagnetic radiation source and method for eliminating extrafocal electromagnetic radiation

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EP0900450A1 true EP0900450A1 (en) 1999-03-10

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EP (1) EP0900450A1 (en)
JP (1) JP2000511335A (en)
DE (1) DE19781787T1 (en)
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US6185279B1 (en) 2001-02-06
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DE19781787T1 (en) 1999-06-17
FR2748848B1 (en) 2003-03-07

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