EP0003454A1 - Röntgenröhre mit einer Einrichtung zur Verminderung der Divergenz ihres Nutzstrahls - Google Patents

Röntgenröhre mit einer Einrichtung zur Verminderung der Divergenz ihres Nutzstrahls Download PDF

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Publication number
EP0003454A1
EP0003454A1 EP79400035A EP79400035A EP0003454A1 EP 0003454 A1 EP0003454 A1 EP 0003454A1 EP 79400035 A EP79400035 A EP 79400035A EP 79400035 A EP79400035 A EP 79400035A EP 0003454 A1 EP0003454 A1 EP 0003454A1
Authority
EP
European Patent Office
Prior art keywords
anode
ray
ray tube
blades
parallel
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.)
Granted
Application number
EP79400035A
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English (en)
French (fr)
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EP0003454B1 (de
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
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Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0003454A1 publication Critical patent/EP0003454A1/de
Application granted granted Critical
Publication of EP0003454B1 publication Critical patent/EP0003454B1/de
Expired legal-status Critical Current

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    • 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.
  • 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.
  • Uniform energy distribution radiating is linked to the shape of the anode.
  • the X-ray beam in the form of a flat fan with a substantially uniform energy distribution is obtained by the bombardment of a rectangular electron beam on the surface. cylindrical anode.
  • the cathode is placed so as to clear the space facing the rectangular focal point located on a generator of the cylindrical surface of the anode and so that the axis of the X-ray beam is normal to this cylindrical surface at the focal point .
  • a diaphragm outside the tube is used as collimator, comprising a rectangular slot oriented so as to select the rays emitted at the focal point in order to obtain a flat fan-shaped radiation, as described in French patent application no. 77.02456 requested in the name of "Compagnie i de Radiologie" on January 28, 1977 and published under the number 2.379 158.
  • the radiogenic tube with a rotary anode can also be provided with an anti-extra-focal device placed very close, parallel to the cylindrical surface of the anode and composed of two layers of different materials, one of which absorbs by braking on its external face the secondary electrons which rebound from the hearth and which, re-accelerated, would risk to cause in other points of the anode a radiation called extra-focal.
  • the second layer is the closest to the cylindrical surface of the anode and aims to absorb the extra-focal radiation from the node at points other than the hearth.
  • the X-ray emitting surface is placed in a well dug in the anode of a material such as copper, so as to serve as a target for an electron beam from 'a cathode and so that the resulting X-ray beam can be emitted through a second well connected to the previous one and dug perpendicular to it.
  • the extra-focal radiation is very limited by the fact that the focus of the anode is enclosed in a very thick copper well. Slit diaphragms outside the tube are also used in this case in order to obtain a flat and fan-shaped X-ray beam.
  • a radiology device (computed tomography) comprising one of these x-ray tubes associated with X-ray detectors, makes it possible to measure the absorption coefficients of a body placed between this tube and the detectors and therefore its internal observation on a certain slice.
  • the ideal would be to irradiate the body only in the desired area so that the detectors receive all of the radiation attenuated by it, that is to say by a useful beam of radiant energy, flat, fan of constant thickness.
  • Such a beam of strictly constant thickness, represents in the current state of the art only the ideal beam which must be imitated as best as possible. Indeed, the slit diaphragms which are placed close to the object to be observed, do not sufficiently eliminate the phenomena of divergence of radiation and allow only beams in range with non-parallel directions.
  • the radiation zones located on either side of the theoretical parallel directions cause an unnecessary irradiation of the object in zones which are not to be observed, as well as a harmful increase in the scattered radiation.
  • the area to be observed is therefore irradiated by radiation lower than that which would be used in the theoretical case of the fan beam of strictly flat shape.
  • the present invention relates to a device for reducing the divergence of the useful beam as a fan of an X-ray tube.
  • a tent diaphragm provided with parallel blades is placed inside the glass enclosure, vacuum tight, of the tube, near the focus of the anode.
  • This tube can be a fixed anode or a cylindrical rotating anode.
  • This diaphragm consists of a support in the form of a crown sector pierced with a slot facing 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 beam range 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 fan a rectangular section of height identical to the thickness of the desired beam.
  • X-ray opaque blades for example in Tantalum
  • Tantalum X-ray opaque blades
  • These blades make it possible to split the apparent focus of the anode into more.
  • 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, it is crossed by a reconstructed beam, flat and fan-shaped, with divergence identical to the divergence of a beam 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 with respect to the glassware of the tube on the one hand and with respect to residual extra-focal phenomena on the other hand, in the case of an X-ray tube with a cylindrical rotating anode than.
  • These thin metallic sheets for example nickel, also have a filtration 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.
  • the tube comprises a glass envelope 1 of cylindrical shape with an axis of revolution xx ′, the ends of which are united in an ultra-vacuum tight manner, to a cathode base 2 on the one hand and to a metal disc 3, support anode on the other hand.
  • These unions are provided in a known manner, by annular parts 4 and 5 made 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
  • X-ray emitting material for example tungsten
  • the vacuum-tight junction of the rotor 7 and the metal disc 3 is provided by a thin metallic rotor collar 8 as described in French patent application No. 77/23444, requested in the name of "Compagnie i de Radiologie" on July 29, 1977.
  • 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 earthed 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 kept at the same potential as the anode. It is made up of these 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 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 X-ray source is limited to the 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 1 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 at point P representing a focal point.
  • the useful X-ray beam therefore emerges from the generator of the cylindrical surface of the anode containing the 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 allows to reduce according to the value of the bias voltage, the concentration of the electric beams. fires generating homes or electronic blocking of transmitters. 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 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-cylindrical surface space. 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 of rays Fan-shaped X thus produced is 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 with axis zz 'and opening angleo ⁇ and thickness the length of the focal point almost linear.
  • the slot thus formed therefore also has as its axis of symmetry the axis zz 'and for opening, an opening of angle ⁇ having the point P at its apex.
  • 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 suitable 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 modes for producing 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 15 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 assumes only 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 may 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 field 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 ramp of detectors, only in the desired zone of my This means that 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.
EP79400035A 1978-01-24 1979-01-19 Röntgenröhre mit einer Einrichtung zur Verminderung der Divergenz ihres Nutzstrahls Expired EP0003454B1 (de)

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 true EP0003454A1 (de) 1979-08-08
EP0003454B1 EP0003454B1 (de) 1983-05-11

Family

ID=9203761

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79400035A Expired EP0003454B1 (de) 1978-01-24 1979-01-19 Röntgenröhre mit einer Einrichtung zur Verminderung der Divergenz ihres Nutzstrahls

Country Status (6)

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

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6600159B2 (en) 2000-08-10 2003-07-29 Koninklijke Philips Electronics N.V. Image correction method for an X-ray detector
US20220344121A1 (en) * 2021-04-23 2022-10-27 Oxford Instruments X-ray Technology Inc. X-ray tube anode

Families Citing this family (7)

* 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
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

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2638554A (en) * 1949-10-05 1953-05-12 Bartow Beacons Inc Directivity control of x-rays
FR1051495A (fr) * 1951-12-17 1954-01-15 Radiologie Cie Gle Perfectionnements aux appareils générateurs de rayonnement x
FR2038757A5 (en) * 1969-03-28 1971-01-08 Atome Ind Radiation collimator
FR2166540A5 (de) * 1971-12-29 1973-08-17 Aquitaine Petrole

Family Cites Families (5)

* 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
US2677069A (en) * 1951-05-26 1954-04-27 Charles H Bachman Device for producing x-rays
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
US3949229A (en) * 1974-06-24 1976-04-06 Albert Richard D X-ray scanning method and apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2638554A (en) * 1949-10-05 1953-05-12 Bartow Beacons Inc Directivity control of x-rays
FR1051495A (fr) * 1951-12-17 1954-01-15 Radiologie Cie Gle Perfectionnements aux appareils générateurs de rayonnement x
FR2038757A5 (en) * 1969-03-28 1971-01-08 Atome Ind Radiation collimator
FR2166540A5 (de) * 1971-12-29 1973-08-17 Aquitaine Petrole

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM TECHNICAL DISCLOSURE BULLETIN, Vol. 19, No. 6, November 1974 New York M.B. HERITAGE et al.: "Electron gun for generating X-rays" page 1823 * Article Integral * *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6600159B2 (en) 2000-08-10 2003-07-29 Koninklijke Philips Electronics N.V. Image correction method for an X-ray detector
US20220344121A1 (en) * 2021-04-23 2022-10-27 Oxford Instruments X-ray Technology Inc. X-ray tube anode
US11721514B2 (en) * 2021-04-23 2023-08-08 Oxford Instruments X-ray Technology Inc. X-ray tube anode

Also Published As

Publication number Publication date
US4217517A (en) 1980-08-12
EP0003454B1 (de) 1983-05-11
FR2415365B1 (de) 1980-09-19
DE2965335D1 (en) 1983-06-16
FR2415365A1 (fr) 1979-08-17
JPS54110793A (en) 1979-08-30
HU180766B (en) 1983-04-29

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