US3643092A - Combined luminescent screen and antidiffusion grid and method of making same - Google Patents

Combined luminescent screen and antidiffusion grid and method of making same Download PDF

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Publication number
US3643092A
US3643092A US15820A US3643092DA US3643092A US 3643092 A US3643092 A US 3643092A US 15820 A US15820 A US 15820A US 3643092D A US3643092D A US 3643092DA US 3643092 A US3643092 A US 3643092A
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strips
screen
ray
grid
flat
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US15820A
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English (en)
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Willem H Van Der Feyst
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Optische Industrie de Oude Delft NV
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Optische Industrie de Oude Delft NV
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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
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens

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  • ABSTRACT A combined X-ray luminescent screen and antidifinsion grid
  • the invention relates to X-ray luminescent screens and, more particularly, to screens of the compartmented type.
  • the phosphor layer is usually subdivided into a large number of small dots which are optically separated from each other by thin walls, usually metallic, which are strongly light reflective and extend substantially parallel to the primary X-rays.
  • compartmenting is to confine light generated in a phosphor particle and propagated as stray light in all directions, to the space enclosed by the adjacent light reflecting walls.
  • the compartmentedscreens may thus be made thicker and, with a given resolving power or definition, may have a better energy conversion efficiency.
  • compartmented screens according to the invention in the broadest aspect thereof, is characterized in that at least a part of the separating walls are formed by evenly spaced apart substantially flat strips which, in addition to being highly light reflective, consist of a material having relatively high absorption for X-rays, the spaces between adjacent strips containing luminescent material along part of their height only, and along the remainder of their height which is a multiple of the spacing distance between adjacent strips, either being empty or containing a material which has relatively low absorption for X-rays.
  • the phosphor side of the screen is turned toward the observer, or to the lens of an X-ray fluorographic camera, as the case may be.
  • the other side is thus facing the X-ray source. Due to their X-ray absorbing properties, the narrowly spaced strips will only give passage to those rays which are directed substantially along the primary X-ray beam. Diffused X-rays, such as manifesty radiation coming from the patient under examination, are stopped by the strips and are thus prevented from spoiling the delicate contrasts of the primary X-ray image formed in the screen. As is well known, it is common practice to use separate antidiffusion grids or Buckygrids for this purpose.
  • Bucky-grids are flat panels placed before the X-ray screen and made up of thin heavy-metal strips spaced apart by spacer strips of nonabsorbing material, such as pertinax.
  • Another well-known type of antidiffusion grids has a circular form and is made by winding a thin heavy-metal strip together with a spacer strip in the fashion of a spiral.
  • Antidiffusion or Bucky-grids are presently being manufactured in large quantities in accordance with well-mastered production methods.
  • the combined luminescent screen and antidiffusion grid according'to the invention in its simplest form, may be made in a manner similar to a conventional antidiffusion grid, the spacers, however, being given a height somewhat less than that of the absorbing strips and the empty spaces thus left between the absorbing strips being filled with the phosphor afterwards.
  • the double-function panel thus obtained compared to a continuous screen with separate antidiffusion grid, has the advantage of being compartmented in one direction, which may sufficiently improve the performance of the screen for certain purposes.
  • the screen according to the invention will be compartmented in two directions in that between adjacent flat strips highly light-reflective waved or corrugated strips are inserted acting as spacers between the flat strips.
  • corrugated strips have the same height as the plane strips and are made of an X-ray absorbing material, e.g., the same material as the flat strips. then the antidiffusion properties of the resulting assembly will be similar to those of a pair of crossed Bucky-grids. If, however, the corrugated strips have a much smaller height, more particularly one that does not exceed the thickness of the phosphor layer envisaged, then the screen will act upon stray X-rays in much the same way as a single conventional Bucky-grid.
  • the panel or disc thus obtained is placed with one side in an easily impressible layer of a solvable matter with a thickness equal to that of the phosphor layer to be applied.
  • the interspaces not filled by the solvable matter are filled with a self-hardening liquid.
  • the solvable matter is removed with a suitable solvent and the phosphor is brought into the compartments.
  • FIG. 1 a perspective view, partly in cross section, of a small portion of a first screen according to the invention, using solid strips as spacers between the X-ray absorbing strips;
  • FIG. 2 a top view of a grid for a second type of screen according to the invention, during its formation this screen being circular and using a corrugated strip to provide the required spacing between the X-ray absorbing strips and to form compartments;
  • FIG. 3 a similar top view as FIG. 2 of a rectangular grid during its formation
  • FIG. 4 a cross-sectional view of a portion of a completed screen using grids according to FIG. 2 or 3;
  • FIG. 5 a perspective view of the strip configuration as used in the screen of FIG. 4;
  • FIG. 6 a similar perspective view of a different strip configuration
  • FIG. 7 a cross-sectional view of an arrangement which may be used for producing screens having their X-ray absorbing strips directed to the X-ray focus;
  • FIG. 8 a cross-sectional view of a screen produced by means of the arrangement of FIG. 7.
  • the screen partly shown in FIG. 1 is made up of thin metallic strips I spaced apart by solid strips 2 ofa material which is transparent for X-rays in a manner similar to conventional antidiffusion grids.
  • the strips 2 are of somewhat less height than the strips 1 and, in addition, the material of the latter strips is so selected that they not only absorb the secondary X-rays incident thereon but also have a highly lightreflective surface.
  • narrow grooves having reflective sidewalls are formed which are filled with the phosphor 3.
  • the material of strips 2 is also light reflective, e.g., white, in order to have as much of the light emanating from the phosphor emitted from the screen.
  • the walls 1 confine the luminescent light to the groove in which it is formed and this results in a markedly improved definition of the screen in the direction transverse to the strips 1, compared to a continuous screen of equal conversion efficiency. In certain cases such a one-directional compartmenting of the screen may be desirable therefore.
  • FIGS. 2 to 6 which make use of corrugated strips as a means of spacing apart the flat strips.
  • a circular screen with a fully compartmented phosphor layer can be obtained by winding together in a spiral a long flat strip 4 and a corrugated or waved strip 5 until a disc 6 of the desired diameter has been formed.
  • This disc contains a large number of compartments 7 having substantially equal dimensions and shape.
  • the luminescent material can be brought.
  • FIG. 3 a compartmented rectangular screen 10 can be made by placing alternatingly against each other flat strips 8 and corrugated strips 9, each having the length of the screen, until the desired breadth has been reached.
  • FIG. 4 shows on a larger scale that the interspaces 12 between the flat strips 11 and the corrugated strips 16 are filled with the phosphor 13 along a small portion of their height only. Along the remaining height they are filled with a solid material 14 giving the required mechanical strength to the screen. This material should have a good transparency to X-rays in order to attenuate the primary X- rays as little as possible. To protect the strip edges the upper side of the screen is covered with a thin layer of the same material.
  • the ratio of the height of the spaces filled with the material 14 and the mutual distance of the strips 11 determines the effi' ciency of the assembly as an antidiffusion grid.
  • this ratio as with the conventional Bucky-grids, can be varied between wide limits, but preferably it is made to exceed three.
  • the corrugated strips I6 have the full height of the screen, thus defining prismatic compartments 12 of which only the lower part will be filled with the phosphor.
  • the corrugated strips 16 are much lower than the flat strips 11. Only the interspaces 12" will be filled with the phosphor, whereas the remaining spaces 12' between the flat strips 11 will be left empty or will be filled with a supporting material transparent for X-rays. The latter form may be compared in effect to a single Bucky-grid.
  • the metal strips to be used should of course absorb the depoty X-rays as completely as possible, at least as far as the flat strips are concerned. However, it is also desirable to use strip which is as thin as possible in order to keep the useful area of the screen large. It is desirable therefore to apply metals of high atomic weight which thus have a high specific absorption for X-rays.
  • Gold and silver in a thickness of 0.03 to 0.04 mm. for instance have shown to be suitable, also because of their high reflection for light and their suitability to be transformed to a corrugated or waved strip. It will be clear, though, that the objects of the present invention will be achieved already to a high degree if, in the embodiments illustrated in FIGS. 4 and 5, only the flat strips are made of such a heavy metal, and the other is made e.g., of a lighter metal. Also, the strips may consist of a suitable alloy of light and heavy metals or may have a stratified combination of such different materials.
  • the transverse dimensions of the compartments depend mainly on the desired resolving power of the screen. For many applications a distance between the flat strips of 0.3 to 1 mm. appears to be sufficiently small to avoid any disturbing influence of the grid structure on the X-ray image.
  • the most favorable thickness of the phosphor layer depends on the penetrating power of the primary X-rays and on the light diffusing and light absorbing properties of the phosphor. Preferably, the thickness at which optimal light conversion efficiency is achieved, is determined by some experimentation. It appeared, for instance, that in the case ofa certain medical X-ray image intensifier camera a thickness of 0.6 to 0.7 mm. was best suitable. In either case, the phosphor thickness is of no influence, in a fully compartmented screen, on the resolving power ofthe screen, as the latter is completely determined by the transverse dimensions of the compartments.
  • the screen concerned is a so-called focused screen whose separating walls are directed to the focus of the X-ray tube to be used in conjunction with the screen.
  • the use of focused screens is desirable in order that the separating walls cause as little shadowing in the X-ray image as possible.
  • This surface may be spherical for a circular screen, or cylindrical for a rectangular screen.
  • a layer 19 of an easily impressible and solvable matter has been applied to the surface .
  • Layer I9 has the thickness of the phosphor layer envisaged.
  • the originally flat disc or panel 17 is carefully pressed until it bears on the table 18 throughout its surface. During this step adjacent windings or strips of the grid will slide somewhat alongside each other but they remain strictly vertical.
  • thermosetting plastics such as an epoxy resin known under the trade name Araldite
  • Araldite an epoxy resin known under the trade name Araldite
  • screen 17 is taken up from table 18 and disposed upside down in a trough containing a suitable solvent for the material 19, such as petrol. At the same time, however, the screen is pressed to flatness again, as seen in FIG. 8. Thereby a slight deformation of the screen windings or strips occurs which produces the focused position of the strips. In this condition the plastic can be left to finish setting.
  • a suitable solvent for the material 19 such as petrol.
  • Matter 19 in the meantime is washed out of the compartments. These are now to be filled with the phosphor. This can conveniently be done by strawing the phosphor into the same solvent so that it will be sedimented in the compartments. Finally, the screen can be taken out and dried, after a possible excess of phosphor has been removed. To prevent dropout of phosphor particles the relevant side of the screen can be fixed e.g., by means of a thin layer 15 of polyvinyl alcohol (see FIG. 3).
  • the outer strip may be constantly pressed during winding onto the foregoing strip by means of a roller which is supported by a rod journaled in a point in the optical axis of the screen, at a distance equal to the focal distance.
  • X-ray luminescent screen comprising a large number of compartments containing luminescent material which are separated from one another by thin light-reflective walls extending substantially parallel to the primary X-rays, characterized in that at least part of the separating walls are formed by evenly spaced apart substantially flat strips which consist of a material having relatively high absorption for X-rays, the spaces between adjacent strips containing luminescent material along part of their height only, and along the remainder of their height, which is a multitude of the spacing distance between adjacent strips, either being empty or containing a material which has relatively low absorption for X-rays.
  • X-ray luminescent screen as claimed in claim 1 wherein between said flat strips light-reflective corrugated strips are inserted which act as spacers between such flat strips and define additional walls for said compartments.
  • X-ray luminescent screen as claimed in claim 2 wherein said corrugated strips have the same height as said flat strips and consist likewise of a material having relatively high absorption for X-rays.
  • X-ray luminescent screen as claimed in claim 2, wherein said corrugated strips have a height substantially equal to the thickness of the luminescent layer.
  • X-ray luminescent screen as claimed in claim 1 wherein the remainder of the spaces between said flat strips contain a material which is light reflecting.
  • Method of making an X-ray luminescent screen comprising the steps of: forming a grid of substantially flat high X-ray absorbing strips spaced by light reflecting corrugated strips, placing said grid with one side in an easily impressible layer of a solvable matter having a thickness equal to that of the luminescent layer to be formed, filling the remaining interspaces over said solvable matter with a self-hardening liquid. removing said solvable matter after solidification of said liquid. and bringing luminescent material into the compartments vacated by said solvable matter.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)
  • Luminescent Compositions (AREA)
US15820A 1969-03-05 1970-03-02 Combined luminescent screen and antidiffusion grid and method of making same Expired - Lifetime US3643092A (en)

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NL6903366A NL6903366A (de) 1969-03-05 1969-03-05

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US (1) US3643092A (de)
DE (1) DE2010519A1 (de)
FR (1) FR2037687A5 (de)
GB (1) GB1299664A (de)
NL (1) NL6903366A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4414679A (en) * 1982-03-01 1983-11-08 North American Philips Corporation X-Ray sensitive electrophoretic imagers
US4560882A (en) * 1984-08-31 1985-12-24 Regents Of The University Of California High-efficiency X-radiation converters
US5302423A (en) * 1993-07-09 1994-04-12 Minnesota Mining And Manufacturing Company Method for fabricating pixelized phosphors
US5418377A (en) * 1993-07-09 1995-05-23 Minnesota Mining And Manufacturing Company Pixelized phosphor
US6683409B2 (en) * 2000-12-27 2004-01-27 Mitsubishi Chemical Corporation Structured lighting material, method to generate incoherent luminescence and illuminator

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2034148B (en) * 1978-08-30 1983-06-15 Gen Electric Multi element high resolution scintillator structure
DE2840965C2 (de) * 1978-09-20 1982-11-11 Siemens AG, 1000 Berlin und 8000 München Strahlendiagnostikgerät für die Erzeugung von Schichtbildern eines Aufnahmeobjekts
JPS58204400A (ja) * 1982-05-24 1983-11-29 富士写真フイルム株式会社 放射線像変換パネル

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4414679A (en) * 1982-03-01 1983-11-08 North American Philips Corporation X-Ray sensitive electrophoretic imagers
US4560882A (en) * 1984-08-31 1985-12-24 Regents Of The University Of California High-efficiency X-radiation converters
US5302423A (en) * 1993-07-09 1994-04-12 Minnesota Mining And Manufacturing Company Method for fabricating pixelized phosphors
US5418377A (en) * 1993-07-09 1995-05-23 Minnesota Mining And Manufacturing Company Pixelized phosphor
US6683409B2 (en) * 2000-12-27 2004-01-27 Mitsubishi Chemical Corporation Structured lighting material, method to generate incoherent luminescence and illuminator

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Publication number Publication date
GB1299664A (en) 1972-12-13
NL6903366A (de) 1970-09-08
FR2037687A5 (de) 1970-12-31
DE2010519A1 (de) 1970-09-24

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