EP0056552A2 - X-ray tube containing a universal limiter for secondary radiation - Google Patents

X-ray tube containing a universal limiter for secondary radiation Download PDF

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Publication number
EP0056552A2
EP0056552A2 EP81402080A EP81402080A EP0056552A2 EP 0056552 A2 EP0056552 A2 EP 0056552A2 EP 81402080 A EP81402080 A EP 81402080A EP 81402080 A EP81402080 A EP 81402080A EP 0056552 A2 EP0056552 A2 EP 0056552A2
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Prior art keywords
limiter
radiation
ray tube
secondary radiation
tube
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EP81402080A
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German (de)
French (fr)
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EP0056552B1 (en
EP0056552A3 (en
EP0056552B2 (en
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Emile Gabbay
Jean-Marie Penato
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Thales SA
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Thomson CSF SA
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    • 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
    • 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

Definitions

  • the present invention relates to a universal secondary radiation limiter in an X-ray tube. It finds its application both in classical radiology and in radiotherapy.
  • a suitable target When a suitable target is bombarded by a fast flow of electrons, it emits a certain flow of photons in a spectral band related to the nature and the geometry of the target and related to the speed of the electrons.
  • Such generating devices are called X-ray tubes. They emit more particularly in the X-ray or ⁇ -band. It is also possible to use secondary photonic emissions. In all cases, the focal point is the material area emitting radiation.
  • a ray belonging to the primary ray can be defined as a direct ray which is carried by a straight line cutting the central axis of the solid angle of the useful radiation at a point common to all the primary rays on the central axis of the primary radiation.
  • a secondary ray is carried by any straight line coming from the transmitting focus. This radiation, often of weak energy relati the primary radiation, generates poor images in Radiology and parasitic irradiation causes in Radiotherapy. It should therefore be deleted as completely as possible.
  • the present invention proposes placing a secondary radiation limiter in the X-ray tube in the immediate vicinity of the emitting focus.
  • the collimators whose cross section is in the form of a grid or a grid, leave a trace by absorbing primary radiation in the field of the useful beam.
  • the present invention to remedy these disadvantages of the prior art, is a secondary radiation limiter of simple conical shape, one end of which is fixed to the window of exit from the tube and the other near the source of the radiation.
  • Secondary radiation may not be emitted only from the home. Indeed, the focus is the area bombarded by the electrons incident on the anode. A certain amount of electrons is emitted from the hearth. These electrons are called secondary electrons. They are expelled from the hearth with a certain kinetic energy and undergo an attraction due to the anode potential. They therefore fall on it outside the focus, with an energy such that they also produce a secondary corn radiation outside the focus, that is to say extrafocal.
  • the exemplary embodiments are more particularly drawn from. Radiology but also find their application in Radiotherapy.
  • the X-ray tube shown has a rotating anode 1 included in a sealed or empty envelope 2. It also includes inside the envelope 2, a photon exciter which is here an electron gun not shown. The flow of electrons strikes the rotating anode 1, at the focal point 4 emitting the flow of photons.
  • the secondary radiation limiter 5 comprises a divergent conical envelope 6 of axis of symmetry aligned with the axis 7 of the useful field selected. This limiter 5 has an inlet opening 8 for the photon flux and an outlet opening 9 for the useful radiation.
  • the outlet opening is mechanically linked to the outlet window 10 of the tube.
  • This may include an additional filtration window 11 made of a thin sheet of aluminum or beryllium. This additional filtration has a cumulative effect with the limiter, by absorbing less energetic rays therefore by further depleting the rate of secondary radiation relative to the useful radiation.
  • the mechanical connection means 12 of the outlet opening 9 to the outlet window 10, here comprise a ring 13 brazed or welded to a fold in the wall of the envelope 2.
  • the inlet opening 8 is placed in the immediate vicinity of the emitting focus 4 of the photon flux.
  • the projection of the opening 8 - on the anode 1 can contain or be contained by the surface of the hearth 4. This characteristic can make it possible to reduce the extent of the emitting hearth or to select, by construction of the tube, an area good broadcast.
  • the limiter To be absorbing X photons, the limiter must be made of a material based on a chemical element with a high atomic number. The material must be electrically insulating so as not to induce potential differences with the anode and therefore modify the field lines in the tube. It must also be refractory, since it is placed near the hearth which is a very hot source.
  • the limiter according to the invention consists of a material based on uranium, hafnium or thorium which meet the three qualities mentioned. ''
  • the material can be an oxide of the three chemical elements mentioned above. It can also consist of a substrate covered with such oxides.
  • the mechanical connection means comprise a ring 13 made of an alloy such as for example the Dilver P or the Vacrion 10 in the case of an envelope made of stainless steel or copper.
  • FIG. 2 a focal point emitting photons AB is shown in the half-space to the right of the line carrying the focal point AB.
  • the mediating line X is the axis of symmetry of the figure.
  • a schematic representation of a secondary radiation limiter CDEF is shown, the inlet and outlet openings of which are CD and EF respectively.
  • the primary radiation is Indu in the space limited by the lines GY and GZ, the point G being a point of the axis X of symmetry.
  • a primary radius is therefore defined as a line of this space passing through G.
  • the lines GY and GZ are the lines which carry the sides CE and DF of the limiter. They. intercept the edges A and B of the hearth AB in the figure but they can also cut the interior of the hearth by selecting a fraction.
  • the secondary radiation comprises all the rays carried by the straight lines coming from the focal point AB and which do not pass through the point G. If the walls CE and DF are absorbing the secondary radiation, the two zones of the space included between the straight lines BC .and BE and the wall CE. On the one hand, and the lines AD and AF and the wall DF on the other hand, are empty of any secondary radiation. On the other hand, the zones of the space comprised between the lines BA and BC on the one hand and the lines AB and AD on the other hand each comprise secondary radiation. To reduce it, the CD inlet opening of the CDEF limiter should be brought closer to the AB hearth.
  • the extrafocal X-ray radiation is also considerably reduced.
  • an electron is re-emitted on the curve e. It hits the target at point H, outside the focus.
  • the rays of the sector of the space between the HD and HF rays emitted by the point H, called extrafocal rays are intercepted and absorbed by the wall DF of the limiter.
  • the approximation of the entry face CD of the focal point AB, as well as the enlargement of the limiter on the axis GX make it possible to reduce the share of extrafocal radiation in the useful X-ray beam.
  • FIG. 3 a tube with a fixed well anode has been shown.
  • the tube comprises a cathode 15 provided with a filament 16 and a concentrator 17.
  • An electron beam 18 penetrates into the well 19 of a fixed anode 20.
  • This anode comprises a target 21. emitting photons and is pierced by a window 22 for the exit of radiation.
  • a limiter 23 according to the invention is arranged in a neck 24 of the casing 14 of the tube. Its inlet opening is arranged opposite the window 22 of the fixed anode 20 and its outlet opening is linked as previously indicated to the radiation outlet window 25 with or without an additional filter.
  • the well 19 of the anode also participates in the reduction of the secondary radiation. It may therefore be useful to cover the well 19 externally with a material as previously described to absorb the secondary radiation.
  • An X-ray tube provided with such a secondary radiation limiter has the advantage of bringing the emitting focus closer to the irradiated object without the intermediary of an external collimation chamber as described in the prior art.
  • the reduction in secondary radiation is considerably improved by bringing the input face of the limiter closer to the emitting focus.
  • the emitting focal point can be constituted by an electron target but also by a target bombarded by incident photons which by Compton effect induce a new flux of photons in an improved spectral band according to a given emission diagram.
  • the limiter according to the invention has been described of the divergent type. He . it is possible to realize it in the form of a cone converging the opening inlet then being larger than the outlet opening without the main characters of the invention being changed.
  • the limiter according to the invention can therefore be adapted to any type of small focal tube, thus being a universal limiter of secondary radiation.

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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)
  • Radiation-Therapy Devices (AREA)

Abstract

Limiteur universel pour tout type de tube radiogène tant en Radiologie qu'en Radiothérapie. Le limiteur comporte une enveloppe (6) de forme cônique, d'axe l'axe de symétrie (7) du faisceau utile de rayonnements, réalisé en un matériau opaque au rayonnement secondaire dont l'ouverture d'entrée (9) est à proximité immédiate du foyer émetteur (4) et dont l'ouverture de sortie (10) est liée mécaniquement à la fenêtre de sortie (11) du tube.Universal limiter for all types of X-ray tube in both Radiology and Radiotherapy. The limiter comprises an envelope (6) of conical shape, with an axis of symmetry (7) of the useful beam of radiation, made of a material opaque to secondary radiation, the inlet opening (9) of which is nearby. immediate of the emitting focus (4) and whose outlet opening (10) is mechanically linked to the outlet window (11) of the tube.

Description

La présente invention concerne un limiteur universel de rayonnement secondaire dans un tube radiogène. Elle trouve son application tant en Radiologie classique qu'en Radiothérapie.The present invention relates to a universal secondary radiation limiter in an X-ray tube. It finds its application both in classical radiology and in radiotherapy.

Quand une cible convenable est bombardée par un flux d'électrons rapides, elle émet un certain flux de photons dans une bande spectrale liée à la nature et à la géométrie de la cible et liée à la vitesse des électrons. De tels dispositifs générateurs sont dits tubes radiogènes. Ils émettent plus particulièrement dans la bande des rayons X ou α . Il est aussi possible d'utiliser des émissions photoniques secondaires. Dans tous les cas, on appelle foyer la zone matérielle émissive des rayonnements.When a suitable target is bombarded by a fast flow of electrons, it emits a certain flow of photons in a spectral band related to the nature and the geometry of the target and related to the speed of the electrons. Such generating devices are called X-ray tubes. They emit more particularly in the X-ray or α-band. It is also possible to use secondary photonic emissions. In all cases, the focal point is the material area emitting radiation.

Dans la répartition géométrique du flux des photons engendrés, il est connu d'isoler par des moyens divers un angle solide divergent ou non, dont une section contient le foyer émetteur et qui comporte le rayonnement caractérisé d'utile soit qu'il y soit particulièrement monochromatique soit qu'il y soit d'énergie plus élevée que n'importe où ailleurs. Du fait que la source émissive est un foyer étendu, il vient que le rayonnement utile comporte deux parties :

  • - un rayonnement primaire,
  • - un rayonnement secondaire.
In the geometrical distribution of the flux of the photons generated, it is known to isolate by various means a diverging solid angle or not, one section of which contains the emitting focal point and which comprises the radiation characterized as useful either because it is particularly monochromatic either that there is higher energy than anywhere else. Because the emissive source is an extended focus, the useful radiation may have two parts:
  • - primary radiation,
  • - secondary radiation.

Un rayon appartenant au rayonnemènt primaire peut être défini comme un rayon direct qui est porté par une droite coupant l'axe central de l'angle solide du rayonnement utile en un point commun à tous les rayons primaires sur l'axe central du rayonnement primaire.A ray belonging to the primary ray can be defined as a direct ray which is carried by a straight line cutting the central axis of the solid angle of the useful radiation at a point common to all the primary rays on the central axis of the primary radiation.

Un rayon secondaire est porté par une droite quelconque issue du foyer émetteur. Ce rayonnement, souvent d'énergie faible relativement au rayonnement primaire, est générateur de mauvaises images en Radiologie et de causes d'irradiation parasites en Radiothérapie. Il convient donc de le supprimer le plus complètement possible.A secondary ray is carried by any straight line coming from the transmitting focus. This radiation, often of weak energy relati the primary radiation, generates poor images in Radiology and parasitic irradiation causes in Radiotherapy. It should therefore be deleted as completely as possible.

Dans l'art antérieur, il a été proposé des dispositifs limiteurs du rayonnement secondaire adaptés aux tubes radiogènes: Ces dispositifs, dits collimateur, sélectionnent en fait le champ d'éclairement c'est-à-dire l'angle solide contenant le rayonnement utile.In the prior art, secondary radiation limiting devices have been proposed which are suitable for X-ray tubes: These devices, called collimators, in fact select the field of illumination, that is to say the solid angle containing the useful radiation. .

Dans le brevet français n° 1.051.495 déposée au nom de la Compagnie Générale de Radiologie on a décrit un dispositif collimateur qui réduit le rayonnement secondaire. Mais il consiste en une grille ou trame de forme conique dirigée vers le foyer qui laisse donc une trace dans le champ éclairé en absorbant aussi du rayonnement primaire. De plus, il est situé en dehors du tube radiogène à sa fenêtre de sortie.In French patent n ° 1.051.495 filed in the name of the Compagnie Générale de Radiologie, a collimator device has been described which reduces secondary radiation. However, it consists of a conical grid or frame directed towards the focal point which therefore leaves a trace in the illuminated field while also absorbing primary radiation. In addition, it is located outside the X-ray tube at its exit window.

Dans le brevet français n° 69.09249 publié sous le n° 2.038.757 déposé le 28 mars 1969 au nom de l'Atome Industriel S.A., il est décrit un collimateur de rayonnement à symétrie axiale de révolution dirigée selon l'axe central du faisceau utile. En coupe transversale, le collimateur est ainsi une grille. Il est aussi extérieur à la source radiogène.In French patent n ° 69.09249 published under n ° 2.038.757 filed on March 28, 1969 in the name of Atom Industriel SA, there is described a radiation collimator with axial symmetry of revolution directed along the central axis of the useful beam . In cross section, the collimator is thus a grid. It is also external to the X-ray source.

. Cette disposition extérieure du collimateur est désavantageuse quand il s'agit de réduire le rayonnement secondaire. En effet, l'espace compris entre le foyer et l'entrée du collimateur est libre au rayonnement secondaire. Pour remédier à cet inconvénient, la présente invention propose de placer un limiteur de rayonnement secondaire dans le tube radiogène à proximité immédiate du foyer émetteur.. This external arrangement of the collimator is disadvantageous when it comes to reducing secondary radiation. In fact, the space between the focal point and the entrance to the collimator is free to secondary radiation. To remedy this drawback, the present invention proposes placing a secondary radiation limiter in the X-ray tube in the immediate vicinity of the emitting focus.

De plus, les collimateurs dont une section transversale est en forme de grille ou de trame, laissent une trace en absorbant du rayonnement primaire dans le champ du faisceau utile.In addition, the collimators whose cross section is in the form of a grid or a grid, leave a trace by absorbing primary radiation in the field of the useful beam.

La présente invention, pour porter remède à ces inconvénients de l'art antérieur, est un limiteur de rayonnement secondaire de forme conique simple dont une extrémité est fixée à la fenêtre de sortie du tube et l'autre à proximité du foyer émetteur du rayonnement.The present invention, to remedy these disadvantages of the prior art, is a secondary radiation limiter of simple conical shape, one end of which is fixed to the window of exit from the tube and the other near the source of the radiation.

Le rayonnement secondaire peut ne pas être émis seulement par la foyer. En effet, le foyer est la zone bombardée par les électrons incidents sur l'anode. Une certaine quantité d'électrons est émis par le foyer. Ces électrons sont dits électrons secondaires. Ils sont expulsés du foyer avec une certaine énergie cinétique et subissent une attraction du fait du potentiel d'anode. Ils retombent donc sur celle-ci hors du foyer, avec une énergie telle qu'ils produisent eux aussi un rayonnement secondaire maïs hors du foyer c'est-à-dire extrafocal.Secondary radiation may not be emitted only from the home. Indeed, the focus is the area bombarded by the electrons incident on the anode. A certain amount of electrons is emitted from the hearth. These electrons are called secondary electrons. They are expelled from the hearth with a certain kinetic energy and undergo an attraction due to the anode potential. They therefore fall on it outside the focus, with an energy such that they also produce a secondary corn radiation outside the focus, that is to say extrafocal.

C'est un but de la présente invention d'absorber aussi un tel rayonnement.It is an object of the present invention to also absorb such radiation.

Pour mieux cerner l'invention il est proposé la description de quelques tubes radiogènes équipés de tels limiteurs.To better understand the invention, a description is given of a few X-ray tubes fitted with such limiters.

Les figures annexées représentent :

  • - la figure 1 : un tube radiogène à anode tournante,
  • - la figure 2 : un schéma explicatif des avantages de l'invention,
  • - la figure 3 : un tube radiogène à anode fixe à puits.
The attached figures represent:
  • FIG. 1: an X-ray tube with a rotating anode,
  • FIG. 2: an explanatory diagram of the advantages of the invention,
  • - Figure 3: an X-ray tube with a fixed well anode.

Les exemples de réalisation sont plus particulièrement tirés de .la Radiologie mais trouvent aussi leur application en Radiothérapie.The exemplary embodiments are more particularly drawn from. Radiology but also find their application in Radiotherapy.

A la figure 1, le tube radiogène représenté comporte une anode tournante 1 incluse dans une enveloppe 2 étanche ou vide. Il comporte aussi à l'intérieur de l'enveloppe 2, un excitateur de photons qui est ici un canon à électron non représenté. Le flux d'électrons frappe l'anode tournante 1, au foyer 4 émetteur du flux de photons.In Figure 1, the X-ray tube shown has a rotating anode 1 included in a sealed or empty envelope 2. It also includes inside the envelope 2, a photon exciter which is here an electron gun not shown. The flow of electrons strikes the rotating anode 1, at the focal point 4 emitting the flow of photons.

Le limiteur 5 de rayonnement secondaire comporte une enveloppe conique divergente 6 d'axé de symétrie aligné avec l'axe 7 du champ utile sélectionné. Ce limiteur 5 comporte une ouverture d'entrée 8 du flux de photons et une ouverture de sortie 9 du rayonnement utile.The secondary radiation limiter 5 comprises a divergent conical envelope 6 of axis of symmetry aligned with the axis 7 of the useful field selected. This limiter 5 has an inlet opening 8 for the photon flux and an outlet opening 9 for the useful radiation.

L'ouverture de sortie est liée mécaniquement à la fenêtre de sortie 10 du tube. Celle-ci peut comporter une fenêtre de filtration additionnelle 11 constituée d'une mince feuille d'aluminium ou de béryllium. Cette filtration additionnelle a un effet cumulé avec le limiteur, en absorbant les rayons moins énergétiques donc en appauvrissant encore le taux de rayonnement secondaire relativement au rayonnement utile. Les moyens de liaison mécanique 12 de l'ouverture de sortie 9 à la fenêtre de sortie 10, ici comportent une bague 13 brasée ou soudée à un repli de la paroi de l'enveloppe 2.The outlet opening is mechanically linked to the outlet window 10 of the tube. This may include an additional filtration window 11 made of a thin sheet of aluminum or beryllium. This additional filtration has a cumulative effect with the limiter, by absorbing less energetic rays therefore by further depleting the rate of secondary radiation relative to the useful radiation. The mechanical connection means 12 of the outlet opening 9 to the outlet window 10, here comprise a ring 13 brazed or welded to a fold in the wall of the envelope 2.

L'ouverture d'entrée 8 est placée à proximité immédiate du foyer émetteur 4 du flux de photons. La projection de l'ouverture 8 - sur l'anode 1 peut contenir ou être contenue par la surface du foyer 4. Cette caractéristique peut permettre de réduire l'étendue du foyer émetteur ou d'en sélectionner, par construction du tube, une zone de bonne émission.The inlet opening 8 is placed in the immediate vicinity of the emitting focus 4 of the photon flux. The projection of the opening 8 - on the anode 1 can contain or be contained by the surface of the hearth 4. This characteristic can make it possible to reduce the extent of the emitting hearth or to select, by construction of the tube, an area good broadcast.

Un limiteur universel de rayonnement secondaire placé à l'intérieur d'un tube à décharge doit répondre à trois qualités. Il doit être :

  • - absorbant des photons X,
  • - isolant électriquement,
  • - réfractaire.
A universal secondary radiation limiter placed inside a discharge tube must meet three qualities. He must be :
  • - absorbing X photons,
  • - electrically insulating,
  • - refractory.

Pour être absorbant des photons X, le limiteur doit être constitué d'un matériau à base d'un élément chimique à haut numéro atomique. Le matériau doit être isolant électriquement pour ne pas induire de différences de potentiel avec l'anode et donc modifier les lignes de champ dans le tube. Il doit être aussi réfractaire, puisqu'il est placé à proximité du foyer qui est une source très chaude.To be absorbing X photons, the limiter must be made of a material based on a chemical element with a high atomic number. The material must be electrically insulating so as not to induce potential differences with the anode and therefore modify the field lines in the tube. It must also be refractory, since it is placed near the hearth which is a very hot source.

Le limiteur selon l'invention est constitué d'un matériau à base d'uranium, de hafnium ou de thorium qui répondent aux trois qualités citées. 'The limiter according to the invention consists of a material based on uranium, hafnium or thorium which meet the three qualities mentioned. ''

Le matériau peut être un oxyde des trois éléments chimiques cités plus haut. Il peut aussi être constitué d'un substrat recouvert de tels oxydes.The material can be an oxide of the three chemical elements mentioned above. It can also consist of a substrate covered with such oxides.

Les moyens de liaison mécanique comportent une bague 13 réalisée en un alliage comme par exemple le Dilver P ou le Vacrion 10 dans le cas d'une enveloppe réalisée en inox ou en cuivre.The mechanical connection means comprise a ring 13 made of an alloy such as for example the Dilver P or the Vacrion 10 in the case of an envelope made of stainless steel or copper.

A la figure 2, on a représenté un foyer émetteur de photons AB dans le demi-espace à droite de la ligne portant le foyer AB. La droite médiatrice X est axe de symétrie de la figure. On a schématiquement représenté un limiteur de rayonnement secondaire CDEF dont les ouvertures d'entrée et de sortie sont respectivement CD et EF.In FIG. 2, a focal point emitting photons AB is shown in the half-space to the right of the line carrying the focal point AB. The mediating line X is the axis of symmetry of the figure. A schematic representation of a secondary radiation limiter CDEF is shown, the inlet and outlet openings of which are CD and EF respectively.

Le rayonnement primaire est Indu dans l'espace limité par les droites GY et GZ, le point G étant un point de l'axe X de symétrie. Un rayon primaire est donc défini comme une droite de cet espace passant par G. Les droites GY et GZ sont les droites qui portent les côtés CE et DF du limiteur. Elles. interceptent les bords A et B du foyer AB sur la figure mais elles peuvent aussi couper l'intérieur du foyer en en sélectionnant une fraction.The primary radiation is Indu in the space limited by the lines GY and GZ, the point G being a point of the axis X of symmetry. A primary radius is therefore defined as a line of this space passing through G. The lines GY and GZ are the lines which carry the sides CE and DF of the limiter. They. intercept the edges A and B of the hearth AB in the figure but they can also cut the interior of the hearth by selecting a fraction.

Le rayonnement secondaire comporte l'ensemble des rayons portés par les droites issues du foyer AB et qui ne passent pas par le point G. Si les parois CE et DF sont absorbantes du rayonnement secondaire, les deux zones de l'espace compris entre les droites BC .et BE et la paroi CE.d'une part, et les droites AD et AF et la paroi DF d'autre part, sont vides de tout rayonnement secondaire. Par contre les zones de l'espace compris entre les droites BA et BC d'une part et les droites AB et AD d'autre part comportent chacune du rayonnement secondaire. Pour le réduire il convient de rapprocher l'ouverture d'entrée CD du limiteur CDEF du foyer AB.The secondary radiation comprises all the rays carried by the straight lines coming from the focal point AB and which do not pass through the point G. If the walls CE and DF are absorbing the secondary radiation, the two zones of the space included between the straight lines BC .and BE and the wall CE. On the one hand, and the lines AD and AF and the wall DF on the other hand, are empty of any secondary radiation. On the other hand, the zones of the space comprised between the lines BA and BC on the one hand and the lines AB and AD on the other hand each comprise secondary radiation. To reduce it, the CD inlet opening of the CDEF limiter should be brought closer to the AB hearth.

C'est aussi le cas des zones limitées par les droites ET et EY d'une part et FZ et FU d'autre part, qui ont été hachurées sur la figure 2. Pour que ces zones de rayonnement secondaire soient réduites, il faut éloigner l'ouverture de sortie EF du limiteur selon l'invention du foyer AB, les droites ET et FU se rapprochant respectivement des droites EY et FZ qui limitent le faisceau utile.This is also the case of the zones limited by the lines ET and EY on the one hand and FZ and FU on the other hand, which have been hatched in FIG. 2. For these zones of secondary radiation to be reduced, it is necessary to move away the outlet opening EF of the limiter according to the invention of the focus AB, the lines ET and FU approaching respectively the lines EY and FZ which limit the useful beam.

Le rayonnement extrafocal de rayons X est aussi considérablement réduit. Dans le foyer, un électron est réémis sur la courbe e. Il frappe la cible au point H, hors du foyer. Les rayons du secteur de l'espace entre les rayons HD et HF émis par le point H, dits rayons extrafocaux sont interceptés et absorbés par la paroi DF du limiteur. Le rapprochement de la face d'entrée CD du foyer AB, ainsi que le grandissement du limiteur sur l'axe GX permettent de réduire la part du rayonnement extrafocal dans le faisceau de rayons X utile.The extrafocal X-ray radiation is also considerably reduced. In the focus, an electron is re-emitted on the curve e. It hits the target at point H, outside the focus. The rays of the sector of the space between the HD and HF rays emitted by the point H, called extrafocal rays are intercepted and absorbed by the wall DF of the limiter. The approximation of the entry face CD of the focal point AB, as well as the enlargement of the limiter on the axis GX make it possible to reduce the share of extrafocal radiation in the useful X-ray beam.

A la figure 3, un tube à anode fixe à puits à été représenté. Dans l'enveloppe 14, le tube comprend une cathode 15 munie d'un filament 16 et d'un concentrateur 17. Un faisceau d'électrons 18 pénètre dans le puits 19 d'une anode fixe 20. Cette anode comporte une cible 21. émissive de photons et est percée d'une fenêtre 22 de sortie du rayonnement. Un limiteur 23 selon l'invention est disposé dans un col 24 de l'enveloppe 14 du tube. Son ouverture d'entrée est disposée en regard de la fenêtre 22 de l'anode fixe 20 et son ouverture de sortie est liée comme il a été précédemment indiqué à la fenêtre de sortie de rayonnement 25 munie ou non d'un filtre additionnel.In FIG. 3, a tube with a fixed well anode has been shown. In the envelope 14, the tube comprises a cathode 15 provided with a filament 16 and a concentrator 17. An electron beam 18 penetrates into the well 19 of a fixed anode 20. This anode comprises a target 21. emitting photons and is pierced by a window 22 for the exit of radiation. A limiter 23 according to the invention is arranged in a neck 24 of the casing 14 of the tube. Its inlet opening is arranged opposite the window 22 of the fixed anode 20 and its outlet opening is linked as previously indicated to the radiation outlet window 25 with or without an additional filter.

Dans une telle disposition, le puits 19 de l'anode participe aussi à la diminution du rayonnement secondaire. Il peut donc être utile de recouvrir extérieurement le puits 19 d'un matériau comme précédemment décrit pour absorber le rayonnement secondaire.In such an arrangement, the well 19 of the anode also participates in the reduction of the secondary radiation. It may therefore be useful to cover the well 19 externally with a material as previously described to absorb the secondary radiation.

Un tube radiogène muni d'un tel limiteur de rayonnement secondaire présente l'avantage de rapprocher le foyer émetteur de l'objet irradié sans l'intermédiaire d'une chambre de collimation extérieure comme décrit dans l'art antérieur. De plus, la diminution du rayonnement secondaire est considérablement amélioré grâce au rapprochement de la face d'entrée du limiteur du foyer émetteur.An X-ray tube provided with such a secondary radiation limiter has the advantage of bringing the emitting focus closer to the irradiated object without the intermediary of an external collimation chamber as described in the prior art. In addition, the reduction in secondary radiation is considerably improved by bringing the input face of the limiter closer to the emitting focus.

Le foyer émetteur peut être constitué par une cible à électrons mais aussi par une cible bombardée par des photons incidents qui par effet Compton induisent un nouveau flux de photons dans une bande spectrale améliorée selon un diagramme d'émission donné.The emitting focal point can be constituted by an electron target but also by a target bombarded by incident photons which by Compton effect induce a new flux of photons in an improved spectral band according to a given emission diagram.

Le limiteur selon l'invention a été décrit de type divergent. Il . est possible de le réaliser sous forme de cône convergent l'ouverture d'entrée étant alors plus grande que l'ouverture de sortie sans que les caractères principaux de l'invention soient changés.The limiter according to the invention has been described of the divergent type. He . it is possible to realize it in the form of a cone converging the opening inlet then being larger than the outlet opening without the main characters of the invention being changed.

Le limiteur selon l'invention peut donc être adapté à n'importe quel type de tube à foyer de petite étendue, étant ainsi un limiteur universel de rayonnement secondaire.The limiter according to the invention can therefore be adapted to any type of small focal tube, thus being a universal limiter of secondary radiation.

Claims (8)

1. Limiteur universel de rayonnement secondaire dans un tube radiogène comportant un foyer émetteur (4) et une fenêtre de sortie (11) d'un faisceau utile de rayonnement, caractérisé en ce qu'il comporte une enveloppe (6) d'épaisseur prédéterminée, de forme cônique dont l'axe de symétrie est aligné sur l'axe central (7) du faisceau utile de rayonnements, dont l'ouverture d'entrée (9) est située à proximité immédiate du foyer émetteur (4), dont l'ouverture - de sortie (10) est liée par des moyens de liaison (12) à la fenêtre de sortie (11) du faisceau utile de rayonnements, et en ce qu'il est réalisé en un matériau comportant au moins un élément à haut numéro atomique de façon à absorber le rayonnement secondaire.1. Universal limiter of secondary radiation in an X-ray tube comprising an emitting focus (4) and an outlet window (11) of a useful beam of radiation, characterized in that it comprises an envelope (6) of predetermined thickness , conical in shape, the axis of symmetry of which is aligned with the central axis (7) of the useful beam of radiation, the inlet opening (9) of which is located in the immediate vicinity of the emitting focus (4), opening - exit (10) is linked by connecting means (12) to the exit window (11) of the useful beam of radiation, and in that it is made of a material comprising at least one element at high atomic number to absorb secondary radiation. 2. Limiteur selon la revendication 1, caractérisé en ce que l'enveloppe (6) du limiteur comporte un substrat recouvert d'au moins une couche d'oxydes d'un élément à haut numéro atomique.2. Limiter according to claim 1, characterized in that the casing (6) of the limiter comprises a substrate covered with at least one layer of oxides of an element with a high atomic number. 3. Limiteur selon la revendication 1, caractérisé en ce que l'enveloppe (6) est de forme conique divergente.3. Limiter according to claim 1, characterized in that the envelope (6) is of divergent conical shape. 4. Limiteur selon la revendication 1, caractérisé en ce que les moyens de liaison (12) comportent une bague (13) soudée à l'enveloppe (2) du tube.4. Limiter according to claim 1, characterized in that the connecting means (12) comprise a ring (13) welded to the casing (2) of the tube. 5. Limiteur selon la revendication 1, caractérisé en ce que l'enveloppe (6) est de forme conique convergente.5. Limiter according to claim 1, characterized in that the casing (6) is of converging conical shape. 6. Tube radiogène, caractérisé en ce qu'il comporte à l'intérieur d'une enveloppe (2) étanche au vide, un limiteur universel (6) selon l'une des revendications 1 à 5.6. X-ray tube, characterized in that it includes, inside a vacuum-tight envelope (2), a universal limiter (6) according to one of claims 1 to 5. 7. Tube radiogène du type à anode fixe, selon la revendication 6, caractérisé en ce que l'anode (20) est munie d'un puits (19) recouvert d'un matériau à haut numéro atomique.7. X-ray tube of the fixed anode type, according to claim 6, characterized in that the anode (20) is provided with a well (19) covered with a material with a high atomic number. 8. Tube radiogène selon la revendication 6, caractérisé en ce que le foyer émetteur (4) est du type à émission Compton.8. X-ray tube according to claim 6, characterized in that the emitting source (4) is of the Compton emission type.
EP81402080A 1981-01-16 1981-12-28 X-ray tube containing a universal limiter for secondary radiation Expired - Lifetime EP0056552B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8100775 1981-01-16
FR8100775A FR2498375A1 (en) 1981-01-16 1981-01-16 UNIVERSAL LIMITER OF SECONDARY RADIATION IN A RADIOGENIC TUBE AND RADIOGENIC TUBE COMPRISING SUCH A LIMITER

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EP0056552A2 true EP0056552A2 (en) 1982-07-28
EP0056552A3 EP0056552A3 (en) 1982-08-04
EP0056552B1 EP0056552B1 (en) 1987-02-11
EP0056552B2 EP0056552B2 (en) 1990-09-12

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EP (1) EP0056552B2 (en)
DE (1) DE3175923D1 (en)
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EP0582508A1 (en) * 1992-08-04 1994-02-09 Framatome Method and apparatus for treatment of lesion by high energy radiation
EP0654684A2 (en) * 1993-11-19 1995-05-24 Picker International, Inc. Nuclear camera systems
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US5033074A (en) * 1989-12-04 1991-07-16 Gte Laboratories Incorporated X-ray colllimator for eliminating the secondary radiation and shadow anomaly from microfocus projection radiographs
US6320936B1 (en) * 1999-11-26 2001-11-20 Parker Medical, Inc. X-ray tube assembly with beam limiting device for reducing off-focus radiation
DE10320700A1 (en) * 2003-05-08 2004-12-02 Siemens Ag Vacuum housing for x-ray tube esp. rotating anode tube having a protective layer made of a material which compensates for thermal shock wear effect on the tube material
DE102004025119B4 (en) * 2004-05-21 2012-08-02 Siemens Ag X-ray
EP1941516A2 (en) * 2005-09-06 2008-07-09 Honeywell International Inc. Radio-opaque coatings used as shielding for radiation sources
US9601223B2 (en) 2009-07-21 2017-03-21 Analogic Corporation Anti-scatter grid or collimator
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EP2661736B1 (en) 2011-01-06 2014-04-30 Koninklijke Philips N.V. Imaging system for imaging an object
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Also Published As

Publication number Publication date
EP0056552B1 (en) 1987-02-11
FR2498375A1 (en) 1982-07-23
EP0056552A3 (en) 1982-08-04
US4472827A (en) 1984-09-18
DE3175923D1 (en) 1987-03-19
FR2498375B3 (en) 1983-09-16
EP0056552B2 (en) 1990-09-12

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