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EP0003454B1 - Tube à rayons X comportant un dispositif de réduction de la divergence de son faisceau utile - Google Patents

Tube à rayons X comportant un dispositif de réduction de la divergence de son faisceau utile Download PDF

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Publication number
EP0003454B1
EP0003454B1 EP79400035A EP79400035A EP0003454B1 EP 0003454 B1 EP0003454 B1 EP 0003454B1 EP 79400035 A EP79400035 A EP 79400035A EP 79400035 A EP79400035 A EP 79400035A EP 0003454 B1 EP0003454 B1 EP 0003454B1
Authority
EP
European Patent Office
Prior art keywords
anode
diaphragm
ray tube
tube according
rays
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.)
Expired
Application number
EP79400035A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0003454A1 (fr
Inventor
Jacques Delair
Jacques Le Guen
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.)
Thales SA
Original Assignee
Thomson CSF SA
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 Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0003454A1 publication Critical patent/EP0003454A1/fr
Application granted granted Critical
Publication of EP0003454B1 publication Critical patent/EP0003454B1/fr
Expired 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
    • G21K1/025—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/24—Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof
    • H01J35/26—Tubes wherein the point of impact of the cathode ray on the anode or anticathode is movable relative to the surface thereof by rotation of the anode or anticathode

Definitions

  • the present invention relates to an X-ray tube comprising a device for reducing the divergence of its useful beam and fitted in particular to tomography devices.
  • These X-ray tubes make it possible to generate in conjunction with collimation means, such as a slit diaphragm, a flat X-ray beam, of constant thickness, and in a fan shape with a large opening with a substantially uniform distribution of energy. radiant in a plane and in all directions inside this opening.
  • tubes consist of a cathode emitting an electron beam of rectangular section and an anode, fixed or rotating, bombarded by this beam, both being placed in the same vacuum-tight glass enclosure.
  • the bombarded surface of the anode emits an X-ray beam which, using collimation means such as a slit diaphragm external to the tube, is flat and fan-shaped.
  • the uniform distribution of radiant energy is related to the shape of the anode.
  • This diaphragm is unsuitable for providing a flat beam of radiation since the raster blades lining the tube are focused on the focal point of radiation. In addition, being placed outside the tube, this weft diaphragm does not pick up the X-rays that come out of the X-ray tube out of the mouth of the diaphragm.
  • French Patent No. 2,304,320 describes an X-ray collimator adapted to give the radiation a flat fan shape and in which the X-ray passage slot is materialized by two flat plates of X-ray absorbing material, parallel to the plane desired range and limiting the radius to it.
  • the thickness of the fan beam therefore depends in principle on the spacing of the plates forming two walls of the collimator. Oblique rays which risk irradiating (in the case of use in tomography) parts of the body outside the cutting plane, meet said plates and are absorbed.
  • the effectiveness of such a system is limited and a certain divergent radiation rate cannot be prevented because the oblique rays which are the most slightly diverging from the plane of the fan can pass through the space defined between the two plates without meet them.
  • the object of the invention is to further reduce the rate of divergent radiation in such a type of collimator used in connection with an X-ray tube.
  • the two aforementioned opaque walls are materialized by two opposite surfaces of the slot defined in the thickness of said crown or of said crown sector, which slot houses said opaque blades.
  • the main application of the invention is a so-called rotation type X-ray apparatus consisting of a source and a multi-detector; it requires a source emitting a flat fan beam, the opening of which makes it possible to cover all the detectors placed opposite.
  • a source emitting a flat fan beam the opening of which makes it possible to cover all the detectors placed opposite.
  • This diaphragm in the form of a crown or crown sector faces the focal point of the anode, so that the plane of the range of the beam perpendicular to the focal point passes through it.
  • This slot therefore has in the plane of the range of the beam a section in the form of an opening ring sector identical to that of the desired beam and in the plane normal to the plane of the range a rectangular section of height identical to the thickness of the desired beam.
  • the plates opaque to X-rays allow the apparent focal point of the anode to be divided into several small focal points at the level of the slit diaphragm. It is as if these small apparent foci generated very weak diverging fan-shaped X-ray beams.
  • the beam of X-rays emitted from the focus is therefore divided into a number of very thin beams of fan-shaped X-rays equal to the number of plates plus one.
  • This phenomenon takes place directly at the outlet of the diaphragm and is due to the shadow of the opaque blades with respect to the X-rays.
  • the divergence of the beams, small but existing, and the large distance from the diaphragm to the object to be irradiated, due to its position inside the glass enclosure of the tube, will blur these shadow phenomena. Indeed, thanks to the large distance separating the diaphragm from the object to be irradiated, the latter is crossed by a reconstituted beam, flat and fan-shaped, with divergence identical to the divergence of a beam coming from the space between two blades and consequently with very small divergence.
  • the edges of the opaque blades are hidden by thin metallic sheets in order to avoid their harmful field effects vis-à-vis the glassware of the tube on the one hand and vis-à-vis residual extra-focal phenomena on the other part, in the case of an X-ray tube with a cylindrical rotating anode.
  • These thin metallic sheets for example nickel, also have a filtering role, because they have the property of absorbing low energy X-rays. They therefore make it possible to filter the residual extra-focal radiation which is of very low energy compared to that of the useful beam as a fan.
  • Figures 1 and 2 show an embodiment of the device according to the invention in an X-ray tube with a cylindrical rotating anode, respectively in axial and transverse section.
  • the tube comprises a glass envelope 1 of cylindrical shape with an axis of revolution.
  • XX ' the ends of which are united in a sealed manner to the ultrahigh vacuum, to a cathode base 2 on the one hand and to a metal disc 3, anode support on the other hand.
  • These unions are provided in known manner, by annular parts 4 and 5 of a metal alloy having a coefficient of thermal expansion close to that of glass.
  • the rotating anode 6 has the shape of a flat cylinder whose cylindrical surface is made of X-ray emitting material (for example tungsten) and is connected to a rotor 7 whose axis of rotation yy 'is off-center with respect to the axis xx 'of the X-ray tube.
  • the vacuum-tight junction of the rotor 7 and the metal disc 3 is provided by a thin metallic rotor neck 8 as described in French patent application No. 77/23444, requested in the name of “Compagnie embl de Radiologie on July 29, 1977 , publication no.2.399.124.
  • This rotor 7 is arranged in a rotating field generated by a stator 9 at the same potential as the anode which can be either grounded or at high positive voltage as described in the patent application cited above.
  • An anti-extra-focal device 12 which has the shape of a crown sector centered on the axis of rotation of the anode 6, is placed very close to the cylindrical surface of this anode. It is integral with the metal disc 3 and is maintained at the same potential as the anode. It is composed of two layers A and B and is hollowed out in its center so as to allow the free passage of the electron beams 15 and 15 'on the one hand, as well as the free passage of the beam of energy radiating from the focus d 'somewhere else.
  • Its layer A made of a light material such as graphite, titanium or any other suitable material, absorbs by braking the secondary electrons which, re-accelerated, would bombard the anode at points other than the focus and cause extra-focal radiation.
  • Its layer B made of a material of high atomic mass such as tungsten, attached to layer A, absorbs the extra focal radiation emitted at other points of the anode than the hearth.
  • this anti-extra-focal device is such that it covers the projection onto itself of the interval delimited by the two tangents aa 'and bb' at the anode 6.
  • the only possible source of X-rays is limited to dimension 1.
  • a field distributor 11 parallel to the circular faces of the anode is integral with the cathode base 2, and carries perpendicularly to its face opposite the anode, a support 10 consisting of a sector-shaped part 13 crown centered on the axis xx 'of revolution of the glassware 1 of the X-ray tube.
  • This part 13 is made of metal of very high atomic mass so as to absorb X-rays and assumes both the functions of carrier of the slit diaphragm according to the invention and of carrier of two cathode emitters 16 and 16 '.
  • These two cathode emitters 16 and 16 ' are provided with two concentration pieces 14 and 14' oriented in such a way that the electron beams 15 and 15 ', rectangular and elongated, of almost linear section in the plane perpendicular to the plane of Figure 2, reach the cylindrical surface of the anode in a line which projects at point P of Figure 2.
  • the useful beam of X-rays therefore emerges from the generatrix of the cylindrical surface of the anode containing point P.
  • the two cathode emitters 16 and 16 ' are electrically isolated from the concentration pieces 14 and 14' so as to allow the application of a negative bias voltage to these concentration pieces with respect to the potential of the emitters.
  • This cathode device makes it possible to reduce, depending on the value of the bias voltage, the concentration of the electron beams generating the foci or the electronic blocking of the emitters.
  • the reduction of the beams, therefore of the focal points, is carried out on the smallest dimension of the rectangular section.
  • the two emitters therefore supply two electron beams allowing a wide range of focal points of different dimensions, starting from the initial dimensions, that is to say without any polarization being applied to the concentration pieces. These initial dimensions may be the same or different.
  • the two transmitters are never used simultaneously.
  • these cathode emitters 16 and 16 ' are placed symmetrically on the part 13 in the form of a crown sector, so as to balance the field lines in the cathode-surface space.
  • cylindrical of the anode and so as to clear the space opposite the rectangular focal point produced by one of the two electron beams, coinciding with a generatrix of the cylindrical surface of the anode so that the axis of the beam Fan-shaped X-rays thus produced are normal to the cylindrical surface at the focal point.
  • Part 13 is hollowed out in its center, facing the focal point of the anode so as to allow free passage of the beam of radiant energy of axis zz ′ with an opening angle a and a thickness equal to the length of the foyer.
  • the slot thus formed therefore also has as its axis of symmetry the axis zz 'and for opening, an angle opening a having the point P at its apex.
  • Grooves 17 and 17 ′ are machined in the walls parallel to the axis xx ′ delimiting this slot so that blades 18 parallel to one another can be deposited therein. These blades can be parallel to the plane of the range of the X-ray beam normal to the focus of the anode.
  • the diaphragm 13 itself being made of a material with high absorbency of X-rays, can also stop divergent rays passing between the pack of parallel blades 18 and the faces of the slit made in the diaphragm.
  • These blades are made of tantalum or any other material opaque to X-rays and are intended to avoid too great a divergence of the useful beam of X-rays.
  • the divergence will depend on the spacing of the blades and their length in the direction of propagation of the useful beam, the closer they are, the greater the division into apparent foci and the more the divergence is limited.
  • edges of these X-ray opaque blades are hidden by thin sheets of nickel or any other appropriate material 19 and 20, in order to avoid the field effects harmful to the glassware 1 of the tube and to the anti-extra-focal device. 12.
  • Figures 3 and 4 show two embodiments of the anti-divergence device according to the invention, in an X-ray tube with a fixed anode.
  • the tube shown in axial section in FIG. 3 comprises a casing 1 of cylindrical shape, of axis of revolution xx ′, the ends of which are united in the same manner as for the tube with the preceding rotating anode, to a cathode 16 d 'on the one hand and to an anode 6 on the other hand.
  • This anode is dug by two wells, one in the direction xx 'and the other perpendicularly. The intersection of these two wells reveals an inclined surface 6 ′, emitting X-rays, which is bombarded by an electron beam of rectangular section coming from the cathode 16.
  • a support 10 connected to the anode has the same potential as the latter and is composed of a part 13 in the form of a crown sector centered on the axis xx 'which only assumes the role of slit diaphragm conforming to the invention.
  • this slot is placed very close to the focal point of the anode and provided with opaque blades 18, thanks to the grooves 17 and 17 ' .
  • blades are parallel to each other, and can be parallel to the plane of the range of the useful beam of X-rays. They have their cutting edges hidden by thin sheets of nickel or any other suitable material 19 and 20, in order to avoid the effects harmful to the glassware of the tube and to absorb extra-focal low energy radiation already very limited in this kind of X-ray tube.
  • FIG. 4 represents a cross section of a tube with a fixed anode similar to that of FIG. 3, but with a modification in the shape of the part 13.
  • the latter still hollowed out with a slot provided with opaque blades, surrounds the anode 6 completely.
  • This new shape allows a better distribution of the field in the glass enclosure 1 and in no way affects the proper functioning of the anti-divergence device.
  • the anti-divergence device also has the advantage of being inside the glass enclosure of the X-ray tube, whether it is with a fixed or rotating cylindrical anode. Indeed, one adjusts once and for all its position, and the arrangement of the opaque blades, so as to have the best flat beam with constant thickness and fan possible. The position of the diaphragm therefore remains immutable, unlike slit diaphragms external to the tube, which require renewed adjustments.
  • X-ray tubes with a fixed or cylindrical rotating anode equipped with the device according to the invention are used in particular in transverse axial tomography devices comprising a ramp composed of numerous radiation detectors, all lit simultaneously by a wide-opening fan beam.
  • the small divergence of the tubes thus equipped makes it possible to irradiate the body to be observed, placed between the tube and the detector ramp, only in the desired area so that the detectors receive almost all of the attenuated direct radiation.
  • This device therefore improves detection and reduces the harmful effects of irradiating zones due to the divergence of the useful beam of X-rays in a fan.

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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)
  • Analysing Materials By The Use Of Radiation (AREA)
EP79400035A 1978-01-24 1979-01-19 Tube à rayons X comportant un dispositif de réduction de la divergence de son faisceau utile Expired EP0003454B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7801878A FR2415365A1 (fr) 1978-01-24 1978-01-24 Dispositif de reduction de la divergence du faisceau utile d'un tube a rayons x, et tube ainsi equipe
FR7801878 1978-01-24

Publications (2)

Publication Number Publication Date
EP0003454A1 EP0003454A1 (fr) 1979-08-08
EP0003454B1 true EP0003454B1 (fr) 1983-05-11

Family

ID=9203761

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79400035A Expired EP0003454B1 (fr) 1978-01-24 1979-01-19 Tube à rayons X comportant un dispositif de réduction de la divergence de son faisceau utile

Country Status (6)

Country Link
US (1) US4217517A (hu)
EP (1) EP0003454B1 (hu)
JP (1) JPS54110793A (hu)
DE (1) DE2965335D1 (hu)
FR (1) FR2415365A1 (hu)
HU (1) HU180766B (hu)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2498376B1 (fr) * 1981-01-16 1985-09-13 Thomson Csf Anode tournante a faible rayonnement extrafocal et tube radiogene comportant une telle anode
US4837794A (en) * 1984-10-12 1989-06-06 Maxwell Laboratories Inc. Filter apparatus for use with an x-ray source
DE10039002A1 (de) 2000-08-10 2002-02-21 Philips Corp Intellectual Pty Bildkorrekturverfahren für einen Röntgendetektor
US6542576B2 (en) 2001-01-22 2003-04-01 Koninklijke Philips Electronics, N.V. X-ray tube for CT applications
CN103945633B (zh) * 2014-05-12 2016-05-18 重庆大学 一种双柱面电子直线加速器有效焦点尺寸调节装置及方法
JP2016033862A (ja) * 2014-07-31 2016-03-10 株式会社東芝 固定陽極型ｘ線管
JP6320898B2 (ja) * 2014-10-27 2018-05-09 株式会社日立ハイテクサイエンス Ｘ線発生源及び蛍光ｘ線分析装置
US10373792B2 (en) 2016-06-28 2019-08-06 General Electric Company Cathode assembly for use in X-ray generation
US11721514B2 (en) * 2021-04-23 2023-08-08 Oxford Instruments X-ray Technology Inc. X-ray tube anode

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE406067C (de) * 1923-02-16 1924-11-14 Phoenix Roentgenroehrenfabrike Gluehkathoden-Roentgenroehre mit hohem Vakuum
US2638554A (en) * 1949-10-05 1953-05-12 Bartow Beacons Inc Directivity control of x-rays
US2677069A (en) * 1951-05-26 1954-04-27 Charles H Bachman Device for producing x-rays
FR1051495A (fr) * 1951-12-17 1954-01-15 Radiologie Cie Gle Perfectionnements aux appareils générateurs de rayonnement x
US3018398A (en) * 1958-10-27 1962-01-23 Dunlee Corp X-ray generator
US3435211A (en) * 1966-01-04 1969-03-25 Stanford Research Inst Gaseous glow discharge tube with cathode means surrounding anode means
FR2038757A5 (en) * 1969-03-28 1971-01-08 Atome Ind Radiation collimator
BE793444A (fr) * 1971-12-29 1973-04-16 Aquitaine Petrole Procede et appareillage d'analyse spectrometrique a rayons x
US3949229A (en) * 1974-06-24 1976-04-06 Albert Richard D X-ray scanning method and apparatus

Also Published As

Publication number Publication date
FR2415365B1 (hu) 1980-09-19
FR2415365A1 (fr) 1979-08-17
HU180766B (en) 1983-04-29
JPS54110793A (en) 1979-08-30
EP0003454A1 (fr) 1979-08-08
US4217517A (en) 1980-08-12
DE2965335D1 (en) 1983-06-16

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