EP0125962B1 - Röntgenbildverstärker und dessen Anwendung bei rechnergestützter Röntgenaufnahmetechnik - Google Patents

Röntgenbildverstärker und dessen Anwendung bei rechnergestützter Röntgenaufnahmetechnik Download PDF

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Publication number
EP0125962B1
EP0125962B1 EP84400799A EP84400799A EP0125962B1 EP 0125962 B1 EP0125962 B1 EP 0125962B1 EP 84400799 A EP84400799 A EP 84400799A EP 84400799 A EP84400799 A EP 84400799A EP 0125962 B1 EP0125962 B1 EP 0125962B1
Authority
EP
European Patent Office
Prior art keywords
screen
intensifier
thickness
center
luminescent
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
EP84400799A
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English (en)
French (fr)
Other versions
EP0125962A1 (de
Inventor
Jean Ricodeau
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 EP0125962A1 publication Critical patent/EP0125962A1/de
Application granted granted Critical
Publication of EP0125962B1 publication Critical patent/EP0125962B1/de
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/38—Photoelectric screens; Charge-storage screens not using charge storage, e.g. photo-emissive screen, extended cathode
    • H01J29/385—Photocathodes comprising a layer which modified the wave length of impinging radiation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2231/00—Cathode ray tubes or electron beam tubes
    • H01J2231/50—Imaging and conversion tubes
    • H01J2231/50005—Imaging and conversion tubes characterised by form of illumination
    • H01J2231/5001—Photons
    • H01J2231/50031—High energy photons
    • H01J2231/50036—X-rays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2231/00—Cathode ray tubes or electron beam tubes
    • H01J2231/50—Imaging and conversion tubes
    • H01J2231/50057—Imaging and conversion tubes characterised by form of output stage
    • H01J2231/50063—Optical

Definitions

  • the present invention relates to an intensifier of radiological images. It also relates to the application of this intensifier to a digital radiology system.
  • Radiological image intensifiers or I.I.R. are well known in the prior art. For example, see the article published in the technical journal THOMSON-CSF, volume 8, number 4, December 1976, entitled “Image intensification in medical and industrial radiology •.
  • the present invention relates more particularly to luminescent entry screens for I.I.R.
  • these screens are generally produced by vacuum deposition, on a concave substrate, of a luminescent material with a high atomic number, such as cesium iodide.
  • Known screens have either more often a greater thickness of luminescent material on the edges than in the center, or a substantially constant thickness, but rather greater on the edges than in the center.
  • Figure 1 shows a sectional view of a luminescent screen 1 whose thickness h b on the edges is greater than the thickness h c in the center.
  • the dotted curves a and b in FIG. 2 show that, for known screens, the variation in thickness, from the center towards the edges, of the layer of luminescent material as a percentage of its thickness at the center of the screen is either increasing - curve a - is substantially horizontal but rather increasing - curve b -.
  • the Applicant wishes to use I.I.R. for systems such as digital radiology systems in which the same image must be taken several times, using different energies of X-rays.
  • the various images thus obtained are converted to digital and processed on a computer, for example by weighted subtraction, which ultimately gives an image where certain organs stand out in relation to others.
  • the difference in thickness between the center and the edges of the luminescent layer of the I.I.R. results in a difference in X-ray absorption.
  • their probability of absorption decreases faster in the center than at the edges, because the edges are thicker than the center, and the sensitivity of the edges increases. compared to that of the center.
  • the Applicant has concluded that the I.I.R. known for a given X-ray energy, a substantially uniform edge-center sensitivity, but that when the X-ray energy varies, the sensitivity of the I.I.R. in the center of the screen and their sensitivity on the edges evolve very differently.
  • the I.I.R. known therefore are not very suitable for digital radiology systems.
  • the present invention proposes to solve the problem of designing a luminescent IIR screen, usable in particular in a digital radiology system, and the sensitivity of which on all points of the screen varies substantially in the same way, when the x-ray energy varies.
  • the luminescent input screen identical in all points for the X-rays, that is to say that it is sought to have a constant "apparent screen thickness for all incident X-rays. It is necessary to reduce the thickness of the edges of the screen relative to the center so that the length of the path in the luminescent material is substantially the same for all X-rays regardless of their angle of incidence on the screen. So when the energy of the X-rays varies, the length of the path in the incident material being the same for all the X-rays, the sensitivity at all points of the screen varies substantially in the same way.
  • the screen according to the invention is completely different from the known screens. It can be considered that, given the known screens, there was a technical prejudice dissuading those skilled in the art from designing luminescent screens of greater thickness in the center than at the edges. Calculation and experience have shown the advantage of these screens according to the invention.
  • the curve c is decreasing.
  • ⁇ e is substantially equal to - 20%.
  • the edge of the image control as follows. The projection of a screen, such as that shown in Figure 1, on a surface gives a circle of radius r. The edge of the image control consists of a ring of width r / 10 or r / 16 approximately which occupies the periphery of this circle.
  • Figure 3 is a sectional view of an embodiment of a screen according to the invention whose thickness h b on the edges is smaller than the thickness at the center h c .
  • the variation in screen thickness is radial.
  • Luminescent screens are generally produced by vacuum deposition, on a concave substrate, which is required for the proper functioning of electronic optics, of a luminescent material with a high atomic number such as cesium iodide.
  • This substrate can either be the entrance window of the I.I.R., or an attached part inside the I.I.R.
  • the thickness of the luminescent material layer must be as large as possible, but this is to the detriment of the resolution. A compromise must be found. When using cesium iodide deposited under vacuum, this compromise is currently between 200 and 500 micrometers thick.
  • FIG 4 there is shown schematically an intensifier of radiological images 2.
  • the luminescent screen 1 is located on the right side of the I.I.R. This screen receives the impact of X-rays produced by a source 3 placed on the axis 00 'of the I.I.R. at a distance F.
  • the luminescent screen is concave. It is assumed that in the example of FIG. 4 this screen is constituted by a spherical cap with a radius of curvature R.
  • the curvature of the screen can take various other forms; you can use concave luminescent screens, hyperbolic, parabolic ... etc.
  • the screen therefore consists of a quasi-spherical cap.
  • the screen arrow can take various values which are involved in the characteristics of electronic optics.
  • a and ⁇ denote the angles at which the point of impact P on the screen is viewed respectively from the center C of the sphere whose screen is a cap and from the source 3 of X-rays.
  • FIG. 5 is an enlargement of the region of the screen comprising the point of impact P.
  • d Denote by d the path in the luminescent material of the X-rays crossing the screen obliquely at the point P.
  • this path d must be equal to the thickness h c of the screen at its center, on the axis 00 ', which corresponds to the path in the luminescent material of the X-rays moving along the axis 00 '.
  • B 100 mm
  • P the point P defined by this distance B is located on the edges of the screen, at approximately 1/10 ° from the edge of the image control.
  • This means that the thickness of the luminescent layer is approximately 21% thinner at the edges, i.e. at 1/16 th or 1/10 th of the edge of the image field, than at the center of the screen.
  • Curve c in FIG. 2 can therefore have various shapes, while remaining decreasing from the center towards the edges. It can be noted that satisfactory results are obtained with a curve in which ⁇ e varies as the square of the distance from the center.
  • the screens according to the invention are particularly suitable for use in digital radiology systems using a computer to obtain a radiological image, for example by weighted subtraction of images obtained with different energies of X-rays.
  • X-rays are used, the average energy varies from approximately 20 to 30 KeV to 100 KeV.
  • the screens according to the invention can however be used in systems other than digital radiology systems, such as for example conventional radiology systems.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)

Claims (6)

1. Röntgenbildverstärker mit einem gekrümmten Leuchtschirm (1), dessen konkave Seite nach innen gerichtet ist und der die Umwandlung der auftreffenden Röntgenstrahlen in Leuchtphotonen bewirkt, wobei der Bildverstärker in einem digitalen Röntgensystem verwendet wird, in dem dasselbe Bild mehrfach mit unterschiedlicher Röntgenstrahlendosis aufgenommen wird, dadurch gekennzeichnet, daß die Dicke des Leuchtschirms an den Rändern (hb) geringer als in der Mitte (he) ist und daß die Dicke (h) des Leuchtschirms im wesentlichen mit der Dicke (he) in der Mitte über die Gleichung verknüpft ist : h = hc · cos θ wobei 8 = a + β gilt und a und β die Winkel sind. unter denen die Auftreffpunkte der Röntgenstrahlen auf dem Leuchtschirm (1) vom Krümmungsmittelpunkt (C) des Leuchtschirms bzw. von der Röntgenstrahlenquelle (3) aus gesehen werden.
2. Bildverstärker nach Anspruch 1, dadurch gekennzeichnet, daß die Dicke (hb) an den Rändern des Leuchtschirms (1) etwa 15 bis 25 % geringer als die Dicke (hc) in der Mitte des Leuchtschirms ist, je nach der Form der Leuchtschirmkrümmung und dem Wert der Durchbiegung.
3. Bildverstärker nach Anspruch 1, dadurch gekennzeichnet, daß die Formel h = hc · cos θ in jedem Punkt des Leuchtschirm gilt.
4. Bildverstärker nach Anspruch 1, dadurch gekennzeichnet, daß die Formel h = hc · cos 8 im wesentlichen an den Rändern des Leuchtschirms gilt.
5. Bildverstärker nach einem der Ansprüche 1, 3 oder4, dadurch gekennzeichnet, daß die Formel h = hc · cos 8 berechnet wird, indem ein mittlerer Wert im Variationsbereich des Abstands (F) zwischen dem Leuchtschirm und der Röntgenstrahlenquelle (3) gewählt wird.
6. Bildverstärker nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß der Empfindlichkeitsabfall an den Rändern des Leuchtschirms durch Veränderung eines oder mehrerer der folgenden Leuchtschirmparameter kompensiert wird, wobei die Liste nicht erschöpfend ist :
- Dotierungsgrad des Lumineszenzmaterials ;
- optische Kopplung der Photokathode des Bildverstärkers mit dem Leuchtschirm, indem der Oberflächenzustand der Lumineszenzschicht und/oder der Zustand des Trägers verändert wird, auf den die Schicht aufgebracht ist ;
- die Kennwerte der zur Elektronenoptik des Bildverstärkers gehörenden Elektroden, um die kissenförmige Verzerrung zu verringern.
EP84400799A 1983-04-29 1984-04-19 Röntgenbildverstärker und dessen Anwendung bei rechnergestützter Röntgenaufnahmetechnik Expired EP0125962B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8307183A FR2545270B1 (fr) 1983-04-29 1983-04-29 Intensificateur d'images radiologiques et application a un systeme de radiologie numerique
FR8307183 1983-04-29

Publications (2)

Publication Number Publication Date
EP0125962A1 EP0125962A1 (de) 1984-11-21
EP0125962B1 true EP0125962B1 (de) 1988-11-09

Family

ID=9288419

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84400799A Expired EP0125962B1 (de) 1983-04-29 1984-04-19 Röntgenbildverstärker und dessen Anwendung bei rechnergestützter Röntgenaufnahmetechnik

Country Status (5)

Country Link
US (1) US4645971A (de)
EP (1) EP0125962B1 (de)
JP (1) JPS59207551A (de)
DE (1) DE3475141D1 (de)
FR (1) FR2545270B1 (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0754675B2 (ja) * 1986-03-31 1995-06-07 株式会社東芝 Ｘ線イメ−ジインテンシフアイア
JP2514952B2 (ja) * 1987-03-13 1996-07-10 株式会社東芝 Ｘ線イメ−ジ管
JPH079796B2 (ja) * 1987-03-28 1995-02-01 東芝ライテック株式会社 放電ランプ
JP2758206B2 (ja) * 1989-05-23 1998-05-28 株式会社東芝 Ｘ線イメージ管
NL8901711A (nl) * 1989-07-05 1991-02-01 Philips Nv Stralingsdetector voor elementaire deeltjes.
JP3492777B2 (ja) * 1993-10-29 2004-02-03 株式会社東芝 放射線イメージ増強管及びその製造方法
US9066704B2 (en) * 2011-03-14 2015-06-30 Canon Kabushiki Kaisha X-ray imaging apparatus

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2820146A (en) * 1955-02-18 1958-01-14 Du Pont Intensifying screens
US2955219A (en) * 1959-02-16 1960-10-04 Rauland Corp Electron discharge device
US3716713A (en) * 1969-01-09 1973-02-13 Varian Associates Input screen for image devices having reduced sensitivity in the cental region
US3697795A (en) * 1970-11-20 1972-10-10 Machlett Lab Inc Image intensifier tube having a multi-radius photocathode
DE2134110B2 (de) * 1971-07-08 1978-09-14 Siemens Ag, 1000 Berlin Und 8000 Muenchen Eingangsschirm für elektronenoptischen Bildverstärker und Verfahren zur Herstellung einer verlaufenden Schicht des Eingangsschirms
FR2195841B1 (de) * 1972-08-11 1975-03-07 Thomson Csf
JPS5636541B2 (de) * 1973-10-22 1981-08-25

Also Published As

Publication number Publication date
DE3475141D1 (en) 1988-12-15
US4645971A (en) 1987-02-24
FR2545270A1 (fr) 1984-11-02
JPS59207551A (ja) 1984-11-24
EP0125962A1 (de) 1984-11-21
JPH0564413B2 (de) 1993-09-14
FR2545270B1 (fr) 1985-12-27

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