EP0121403B1 - Ecran renforçateur de rayons-X - Google Patents

Ecran renforçateur de rayons-X Download PDF

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Publication number
EP0121403B1
EP0121403B1 EP19840302092 EP84302092A EP0121403B1 EP 0121403 B1 EP0121403 B1 EP 0121403B1 EP 19840302092 EP19840302092 EP 19840302092 EP 84302092 A EP84302092 A EP 84302092A EP 0121403 B1 EP0121403 B1 EP 0121403B1
Authority
EP
European Patent Office
Prior art keywords
screen
support
light absorber
phosphor
underlayer
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
EP19840302092
Other languages
German (de)
English (en)
Other versions
EP0121403A2 (fr
EP0121403A3 (en
Inventor
William J. Zegarski
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.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
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Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Publication of EP0121403A2 publication Critical patent/EP0121403A2/fr
Publication of EP0121403A3 publication Critical patent/EP0121403A3/en
Application granted granted Critical
Publication of EP0121403B1 publication Critical patent/EP0121403B1/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
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens

Definitions

  • This invention relates to X-ray intensifying screens used with photographic film elements to record X-ray images thereon, and particularly to screens having improved imaging characteristics. Still more particularly, this invention relates to X-ray screens having controllable speed and to radiographs produced therefrom which exhibit good image sharpness and reduced noise.
  • X-ray intensifying screens made by incorporation of a luminescent phosphor in a binder and coated on a suitable support are well-known in the prior art. These X-ray screens absorb X-rays and emit energy in the form of light, which in turn exposes a photographic film associated therewith.
  • the phosphors used in these screens can be generally segregated into three classes: (1) broad band emitters (e.g. CaW0 4 ); (2) narrow band emitters (e.g. BaFCI:Eu); and (3) line emitters (e.g. LaOBr:Tm).
  • broad band emitters e.g. CaW0 4
  • narrow band emitters e.g. BaFCI:Eu
  • line emitters e.g. LaOBr:Tm
  • the X-ray screens made with these phosphors are used with radiographic, silver halide film to record X-ray images.
  • One method of increasing speed is to increase the thickness of the phosphor coating. As speed increases, however, there is usually a decrease in image sharpness and thus a decrease in the amount of medical information that can be generated by this system. Conventionally, the speed of an X-ray screen is reduced by lowering the thickness of the phosphor layer or by adding broad band absorbers (e.g. dyes or pigments) to the X-ray screen structure. Controlling screen speed by these prior art methods yields the desired higher sharpness but also increases the noise and mottle of the finished radiograph prepared therefrom.
  • broad band absorbers e.g. dyes or pigments
  • Radiographic noise is a grain or mottle pattern which results from the statistical nature of the imaging process.
  • a source of noise is the distribution of scintillation efficiencies of the individual phosphor crystals. Those crystals with low efficiency may only contribute minimally to the imaging process while those with high efficiency lead to increased density. The fluctuations in developed density appear as noise.
  • radiographic noise should be lowered, and broadening it will increase noise.
  • the addition of dyes or pigments to the screen structure effectively broadens the distribution of scintillation efficiencies, thus increasing the noise.
  • the X-ray screen structure conventionally consists of a phosphor-containing layer coated on a suitable support. It is also beneficial to use an underlayer (e.g. reflective or absorbing layer) coated between the phosphor and the support and to include a protective overcoat for the phosphor layer.
  • an underlayer e.g. reflective or absorbing layer
  • the present invention provides an X-ray intensifying screen comprising, in order, (1) a support, (2) optionally an underlayer, (3) an active layer comprising a phosphor exhibiting narrow or line band emission dispersed in a non-polyurethane containing binder, and (4) optionally an overcoat layer, characterised in that at least one of layers (2), (3) and (4) contains a non-fluorescing ultraviolet (UV) light absorber having absorbance maxima at about 400 nm or below and in that said active layer (3) comprises a said phosphor exhibiting narrow or line band emission selected from the group consisting of LaOBr:Tm, LaOBr:Tb, Y(Nb)Ta0 4 , LaOCI:Bi and BaFCI:Eu.
  • An X-ray screen made according to the invention, used with a photographic film, will produce a sharper image with lower noise and mottle, compared with a screen made without the UV absorber.
  • X-ray intensifying screens comprising (1) a support, (2) optionally an underlayer, (3) an active layer (comprising a phosphor exhibiting narrow or line band emission dispersed in a non-polyurethane binder, e.g. polyvinyl butyral) and (4) optionally an overcoat layer, but not containing UV absorber in layers (2), (3) or (4) are known, for example from US-A-4076897 (Joiner).
  • X-ray intensifying screens containing a UV absorber are also known from US-A-3743833 (Martic et al) but in such screens the phosphor is dispersed in a polyurethane binder. Furthermore the use of a UV absorber specifically with narrow or line band phosphor to greatly improve the image quality of these highly efficient materials has not been shown.
  • FR-A-2066273 discloses photographic film containing a UV absorber and provided on each face used with an X-ray intensifying screen.
  • This document in particular discloses in Example 2, product D, such a film provided with X-ray intensifying screens in which the phosphor is the broad band emitter Ba(Pb)S0 4 .
  • UV light absorbers that exhibit absorbance maxima at about 400 nm or below. All will function within the ambit of this invention. These include the following:
  • absorbers can be dissolved in any convenient organic solvent (e.g. acetone) and added either to layer (2), (3) or (4) in amounts which depend on the effect desired and the layer to which they may be added.
  • organic solvent e.g. acetone
  • Layer (1) is a support.
  • a number of elements can be used such as paper or metal foil, e.g., aluminum. It is preferred to use a macromolecular, hydrophobic organic polymer support.
  • Suitable polymeric supports include cellulose derivatives, e.g., cellulose acetate, cellulose propionate, cellulose acetate butyrate, and ethyl cellulose; polyethylene, polyvinyl chloride, poly(vinyl chloride covinyl acetate), polyvinylidene chloride, polyvinyl acetate, polyacrylonitrile, polystyrene, and polyisobutylene; and polyesters, e.g., polyethylene terephthalates and homologous polyesters obtainable by the process described in Whinfield et al., US-A-2,465,319.
  • Polyethylene terephthalate films are particularly useful because of their dimensional stability.
  • a particularly useful support is biaxially oriented polyethylene terephthalate coated with a subbing layer of vinylidene chloride - methylacrylate - itaconic acid copolymer as described in Alles et al., US ⁇ A ⁇ 2,779,684.
  • the thickness of the support may conveniently be anywhere from about 0.0025 inch to 0.03 inch (0.0064 cm to 0.0762 cm) with 0.01 inch (0.0254 cm) being preferred.
  • the support may contain or be coated with dyes or finely divided pigments, e.g., titanium oxide, lithopone, magnesium carbonate, aluminum oxide, carbon black, and colored pigments, e.g. tartrazine (C.I. No. 640), Victoria Green W.B. Base (C.I. No. 800), and Nubian Resin Black (C.I. No. 864), as opacifying or light-absorbing agents.
  • dyes or finely divided pigments e.g., titanium oxide, lithopone, magnesium carbonate, aluminum oxide, carbon black, and colored pigments, e.g. tartrazine (C.I. No. 640), Victoria Green W.B. Base (C.I. No. 800), and Nubian Resin Black (C.I. No. 864), as opacifying or light-absorbing agents.
  • the above mentioned dyes and pigments are particularly useful in reflective layers to vary the light output or block unwanted wavelengths.
  • the base support may be metallized to provide reflective action, e.g., the
  • a reflective layer comprising anatase grade Ti0 2 , dispersed in chlorosulfonated polyethylene (e.g., Hypalon 20, E. I. du Pont de Nemours and Company, Inc., Wilmington, DE), on the support.
  • chlorosulfonated polyethylene e.g., Hypalon 20, E. I. du Pont de Nemours and Company, Inc., Wilmington, DE
  • a number of other reflective pigments can also be used in the reflective layer. These include the potassium titanates of Brixner, US ⁇ A ⁇ 3,895,157, among others.
  • the phosphors are usually milled for several hours in a solvent/binder mixture and coated over the above referenced reflective layer.
  • a number of binders can be used in the active layer (3) of this invention. It is preferred to use polyvinyl butyral resins but there are a host of suitable polymers used in the prior art that can be used here.
  • Polyurethane elastomeric binders while particularly effective because of their adhesion to the conventional supports described above, are, however, subject to degradation by UV light. Many of the conventional phosphors emit substantial amounts of UV light which can further be reflected back into the active layer by the support; so steps must be taken to prevent this degradation (see Martic et al supra). Thus binders other can polyurethanes are used according to the invention.
  • a protective overcoat made according to any of the teachings of the prior art may be applied over the phosphor layer.
  • These top coats can be cellulose nitrate or acetate or a mixture of resins comprising poly(methylmethacrylate), poly(isobutyl methacrylate), and vinyl chloride/vinyl acetate copolymers as taught by Patten, US ⁇ A ⁇ 2,907,882.
  • An overcoat similar to that described in Brixner et al in U.S. 3,895,157 is particularly efficacious.
  • the overcoat layer can be from about 0.0001 inch to 0.005 inch (0.0003 cm to 0.013 cm) in thickness.
  • An X-ray screen prepared as described above, and in the examples that follow, is eminently useful in medical radiography, for example.
  • the addition of the UV light absorber permits one to control the speed of the screen in a predictable fashion.
  • these screens, when exposed in conjunction with X-ray photographic film will exhibit excellent image sharpness and, importantly, noise and mottle is reduced. This allows more information to be determined from the image. This is a considerable and surprising finding over the prior art which teaches thickness reduction in the phosphor layer to improve image sharpness with a concurrent rise in noise and mottle.
  • the invention provides an X-ray intensifying screen composed of, in order, (1) a film-forming polyester support, (2) an underlayer comprising Ti0 2 dispersed in chlorosulfonated polyethylene, (3) an active layer comprising LaOBr:Tm dispersed in polyvinyl butyral, and (4) an overcoat layer consisting essentially of a fluoroacrylate polymer, wherein at least one of layers (2), (3) and (4) contains an effective amount of a nonfluorescing UV light absorber having absorbance maxima below about 400 nm.
  • Three X-ray intensifying screens were made comprising, in order, a support (1), a a reflective layer (2), an active phosphor layer (3), and an overcoat layer (4).
  • the UV light absorber was placed in layer (4).
  • the reflective suspension was prepared by sandmilling a mixture of the following ingredients for about 4 hours:
  • the milled suspension was filtered through a filtering medium with an average pore-size of 30 microns.
  • the suspension was deaerated and then coated on a sheet of biaxially oriented polyethylene terephthalate film provided with a substratum of vinylidene chloride - methylacrylate - itaconic acid copolymer prepared as described in US-A-2,698,240.
  • a reflective layer was obtained which gave a Ti0 2 coating weight of about 0.029 g/inch 2 (0.0045 g/cm 2 ).
  • the phosphor layer was prepared from the following composition, milled for about 12 hours:
  • Screen I contained UV light absorber (A)
  • Screen II contained UV light absorber (B)
  • Screen III contained UV light absorber (C) at the levels shown above.
  • a screen was prepared without any UV light absorber.
  • UV light absorber to the overcoat layer (4) significantly reduces the mottle produced by the screen, improving the overall image quality of a film exposed thereto.
  • a screen was prepared as in Example 1 except that UV light asborber (B) was instead added to the active phosphor layer (3) at a level of 0.12% by weight of the phosphor (LaOBr:Tm). The following results were obtained:
  • Example 1 To test the efficiency of this invention when a UV-light absorber was added to the reflective layer, a screen was made as in Example 1 except that UV light absorber (B) was instead added directly to the reflective suspension at a level of 0.18% by weight of the Ti0 2 . The following results were obtained:
  • a UV light absorber may also be used in conjunction with a light absorbing underlayer.
  • an active phosphor suspension see Example 1 containing 0.53% of UV light absorber (B) was coated directly on a polyethylene terephthalate film support which contained sufficient carbon to yield an optical density greater than 8.0 (opaque base). This simulates the application of an absorbing underlayer (vs. reflective underlayer in the previous examples). The following results were obtained when this screen was used to expose a high speed X-ray film as taught in Example 1:
  • the dyed screens Prior art elements
  • the screen When coated at a thinner coating weight than the screen of this invention, the dyed screens (prior art elements) were ca. 40% higher in mottle, although somewhat sharper in resolution.
  • the screen When dye is added to a screen of comparable thickness, the screen is ca. 20% higher in mottle.
  • the screen which embodies this invention can greatly improve the signal/mottle ratio and yield an overall improved image on an X-ray film exposed therewith.
  • CaW0 4 is an example of a broad band-emitting phosphor outside the scope of this invention. Three screens were made employing the following structure:
  • the support (1) and reflective layer (2) were the same as described in Example 1.
  • the phosphor layer (3) contained CaW0 4 in place of LaOBr:Tm of Example 1.
  • the overcoat layer (4) was the same as Example 1 except for the UV light absorber.
  • Screen I contained no UV light absorber.
  • Screen II contained 0.52 weight % of UV light absorber (B) and Screen III contained 0.52 weight % of UV light absorber (A), based on cellulose acetate.
  • Example 6 was repeated substituting Ba(Pb)S0 4 (another broad band-emitting phosphor) with the following results:
  • the UV light absorber failed to significantly improve the image quality of the film exposed to a screen having the broad band-emitting Ba(Pb)S0 4 phosphor.
  • phosphor having a narrow emission band is LaOCI:Bi.
  • Two screens having this phosphor were prepared according to the teachings of Example 1. Screen I was prepared without a UV light absorber while Screen II contained 0.52 wt.% of UV light absorber (B) in the overcoat layer. The screens were used to expose high speed medical X-ray film with the following results:
  • Example 9 was repeated using BaFCI:Eu (narrow band emitter) as the phosphor and with 1.04wt.% of UV light absorber (B) in the overcoat layer. The following results were noted:
  • Example 10 was repeated using LaOBr:Tb (line emitter) as the phosphor and with 0.52 wt.% of UV light absorber (B) in the overcoat layer. The following results were noted:

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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)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Claims (11)

1. Un écran intensificateur de rayons X comprenant, dans cet ordre, (1) un support, (2) facultativement une sous-couche, (3) une couche active comprenant une substance fluorescente présentant une émission de bande étroite ou de raies dispersée dans un liant ne contenant pas de polyuréthane et (4) facultativement une couche supérieure de revêtement, caractérisé en ce que l'une au moins des couches (2), (3) et (4) contient un agent absorbeur de lumière ultraviolette non fluorescent qui présente des maxima d'absorption à environ 400 nm ou en-dessous et en ce que ladite couche active (3) comprend une substance fluorescente présentant une émission de bande étroite ou de raies choisie dans le groupe formé par LaOBr:Tm, LaOBr:Tb, Y(Nb)Ta04, LaOCI:Bi et BaFCI:Eu.
2. Un écran tel que revendiqué dans la revendication 1, dans lequel l'agent absorbeur de lumière ultraviolette est un membre du groupe formé par un 2 - (2' - hydroxy - 3',5' - dialkylphényl)benzotriazole, une 2,2' - dihydroxy - 5 - alcoxy - benzophénone et un dérivé de l'anilide oxalique.
3. Un écran tel que revendiqué dans l'une quelconque des revendications 1 et 2, dans lequel la substance fluorescente est LaOBr:Tm.
4. Un écran tel que revendiqué dans l'une quelconque des revendications 1 à 3, dans lequel le liant est du butyral polyvinylique.
5. Un écran tel que revendiqué dans l'une quelconque des revendications 1 à 4, dans lequel une sous-couche (2) est intercalée entre le support (1) et la couche active (3).
6. Un écran tel que revendiqué dans la revendication 5, dans lequel ladite sous-couche contient ledit agent absorbeur de lumière ultraviolette non fluorescent ayant des maxima d'absorption au-dessous de 40 nm.
7. Un écran tel que revendiqué dans l'une quelconque des revendications 1 à 6, dans lequel le support contient, ou est revêtu par, des colorants opacifiants, des colorants réfléchissants ou des pigments finement divisés.
8. Un écran tel que revendiqué dans l'une quelconque des revendications précédentes, dans lequel ledit support (1) est formé d'un polyester filmogène.
9. Un écran tel que revendiqué dans l'une quelconque des revendications précédentes, dans lequel une sous-couche (2) comprenant du Ti02 dispersé dans du polyéthylène chlorosulfoné est intercalée entre le support (1) et la couche active (3).
10. Un écran tel que revendiqué dans l'une quelconque des revendications précédentes, comportant une couche supérieure de revêtement (4) comprenant un polymère de fluoroacrylate.
11. Un écran tel que revendiqué dans la revendication 1, composé, dans cet ordre, (1) d'un support en polyester filmogène, (2) d'une sous-couche comprenant du Ti02 dispersé dans du polyéthylène chlorosulfoné, (3), d'une couche active comprenant du LaOBr:Tm dispersé dans du butyral polyvinylique, et (4) d'une couche supérieure de revêtement formée essentiellement d'un polymère de fluoroacrylate, dans lequel l'une au moins des couches (2), (3) et (4) contient un agent absorbeur de lumière ultraviolette non fluorescent ayant des maxima d'absorption au-dessous d'environ 400 nm.
EP19840302092 1983-03-29 1984-03-28 Ecran renforçateur de rayons-X Expired EP0121403B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US47994183A 1983-03-29 1983-03-29
US479941 1983-03-29

Publications (3)

Publication Number Publication Date
EP0121403A2 EP0121403A2 (fr) 1984-10-10
EP0121403A3 EP0121403A3 (en) 1984-11-21
EP0121403B1 true EP0121403B1 (fr) 1988-11-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19840302092 Expired EP0121403B1 (fr) 1983-03-29 1984-03-28 Ecran renforçateur de rayons-X

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EP (1) EP0121403B1 (fr)
JP (1) JPS59183400A (fr)
DE (1) DE3475240D1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4711827A (en) * 1986-02-24 1987-12-08 E. I. Du Pont De Nemours And Company X-ray intensifying screen with improved topcoat
JP2540370B2 (ja) * 1988-10-20 1996-10-02 富士写真フイルム株式会社 放射線像変換パネル
JPH0782118B2 (ja) * 1988-11-25 1995-09-06 富士写真フイルム株式会社 放射線像変換パネル
DE69213941T2 (de) * 1992-09-11 1997-03-20 Agfa Gevaert Nv Röntgenstrahlenverstärkungsschirm mit verbessertem Verhältnis voin Geschwindigkeit zur Bildqualität
US6413699B1 (en) 1999-10-11 2002-07-02 Macdermid Graphic Arts, Inc. UV-absorbing support layers and flexographic printing elements comprising same
US6815095B2 (en) 2001-12-03 2004-11-09 Agfa-Gevaert Binderless phosphor screen having a pigmented interlayer
EP1316972B1 (fr) * 2001-12-03 2012-09-19 Agfa HealthCare NV Ecran luminescent sans liant doté d'une couche intermédiaire pigmentée
JP2004138440A (ja) * 2002-10-16 2004-05-13 Konica Minolta Holdings Inc 放射線画像変換パネル

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE757816A (fr) * 1969-10-21 1971-04-01 Eastman Kodak Co Nouveau produit pour la radiographie
BE757815A (fr) * 1969-10-21 1971-04-01 Eastman Kodak Co Produit photosensible a ecran renforcateur pour la prise de vuephotographique
BE786323A (fr) * 1971-07-16 1973-01-15 Eastman Kodak Co Ecran renforcateur et produit radiographique le
US4259588A (en) * 1979-10-31 1981-03-31 Eastman Kodak Company Green-emitting X-ray intensifying screens

Also Published As

Publication number Publication date
DE3475240D1 (en) 1988-12-22
EP0121403A2 (fr) 1984-10-10
JPH0517517B2 (fr) 1993-03-09
JPS59183400A (ja) 1984-10-18
EP0121403A3 (en) 1984-11-21

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