EP0088820A1 - Umwandlungsschirm für radiographisches Bild - Google Patents

Umwandlungsschirm für radiographisches Bild Download PDF

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Publication number
EP0088820A1
EP0088820A1 EP82104798A EP82104798A EP0088820A1 EP 0088820 A1 EP0088820 A1 EP 0088820A1 EP 82104798 A EP82104798 A EP 82104798A EP 82104798 A EP82104798 A EP 82104798A EP 0088820 A1 EP0088820 A1 EP 0088820A1
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EP
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Prior art keywords
phosphor
image conversion
radiographic image
layer
rare earth
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EP82104798A
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English (en)
French (fr)
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EP0088820B1 (de
Inventor
Hidehiko Maeoka
Etsuo Shimizu
Yujiro Suzuki
Keiji Shimiya
Norio Miura
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Kasei Optonix Ltd
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Kasei Optonix Ltd
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Priority claimed from JP57039310A external-priority patent/JPS58156899A/ja
Priority claimed from JP7943782A external-priority patent/JPS58196287A/ja
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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

Definitions

  • the present invention relates to a radiographic image conversion screen. More particularly, it relates to a radiographic image conversion screen, i.e. a radiographic intensifying screen (hereinafter referred to simply as "intensifying screen") or a fluorescent screen, which comprises double phosphor layers i.e. a green emitting rare earth phosphor layer and a blue emitting phosphor layer and which has a high speed and exhibits superior image forming characteristics (in this specification, the "radiographic image conversion screen” includes the intensifying screen and the fluorescent screen).
  • a radiographic image conversion screen i.e. a radiographic intensifying screen (hereinafter referred to simply as "intensifying screen") or a fluorescent screen, which comprises double phosphor layers i.e. a green emitting rare earth phosphor layer and a blue emitting phosphor layer and which has a high speed and exhibits superior image forming characteristics
  • the "radiographic image conversion screen” includes the intensifying screen and the fluorescent screen).
  • a radiographic image conversion screen is used for medical diagnosis and non-destructive inspection of industrial products, and it emits an ultraviolet ray or a visible ray upon absorption of radiation passed through an object, and thus converts a radiographic image to an ultraviolet image or a visible image.
  • the radiographic image conversion screen When the radiographic image conversion screen is used as an intensifying screen for radiography, it is fit on a radiographic film (hereinafter referred to simply as "film") so that a radiation image will be converted on the fluorescent surface of the intensifying screen to an ultraviolet image or a visible image which will then be recorded on the film.
  • film a radiographic film
  • the radiation image of the object converted on the fluorescent surface of the fluorescent screen to a visible image may be photographed by a photographic camera or may be projected on a television screen by means of a televison camera tube, or the visible image thus formed may be observed by naked eyes.
  • the radiographic image conversion screen comprises a support made of e.g. paper or a plastic sheet and a fluorescent layer formed on the support.
  • the fluorescent layer is composed of a binder and a phosphor dispersed in the binder and being capable of efficiently emitting light when excited by the radiation of e.g. X-rays, and the surface of the fluorescent layer is usually protected by a transparent protective layer.
  • a high speed radiographic system i.e. a combination of a film and an intensifying screen
  • a radiographic system which is capable of providing good image quality (i.e. sharpness, granularity and contrast) suitable for diagnosis by clinical photography.
  • the intensifying screen is desired to have a high speed and to provide superior sharpness, granularity and contrast.
  • a fluorescent screen it is desired to have a high speed and to provide particularly good contrast so that it is thereby possible to minimize the patients' dosage of radioactivity and at the same time to obtain an image having good image quality.
  • radiographic image conversion screens comprising a rare earth oxysulfide phosphor, such as one wherein a terbium-activated rare earth oxysulfide phosphor which is a green emitting phosphor and represented by the formula (Ln, Tb) 2° 2S where Ln is at least one selected from lanthanum, gadolinium and lutetium, is used (US Patent No. 3,725,704), and one wherein a terbium-activated yttrium oxysulfide which is a blue emitting phosphor and represented by the formula (Y, Tb) 2 0 2 5, is used (US Patent No. 3,738,856).
  • a rare earth oxysulfide phosphor such as one wherein a terbium-activated rare earth oxysulfide phosphor which is a green emitting phosphor and represented by the formula (Ln, Tb) 2° 2S where Ln is at least one selected from lanthanum, gad
  • intensifying screens using a green emitting rare earth phosphor particularly, a rare earth oxysulfide phosphor such as a terbium-activated gadolinium oxysulfide phosphor represented by the formula (Gd, Tb) 2 O 2 S or a terbium-activated lanthanum oxysulfide phosphor represented by the formula (La, Tb) 2 O 2 S, have a speed several times higher than the speed of commonly used conventional intensifying screens using a calcium tungstate phosphor represented by the formula CaWO 4 and they have relatively good granularity as compared to other high speed intensifying screens.
  • a rare earth oxysulfide phosphor such as a terbium-activated gadolinium oxysulfide phosphor represented by the formula (Gd, Tb) 2 O 2 S or a terbium-activated lanthanum oxysulfide phosphor represented by the formula (La, Tb) 2 O 2 S
  • a gadolinium oxysulfide phosphor is paticularly preferably used for a high speed intensifying screen.
  • the intensifying screen using it has drawbacks that the contrast thereby obtainable within the X-ray tube voltage range commonly used for medical diagnosis (i.e. from 60 to 140 KVp) is inferior due to the X-ray absorbing characteristics of such a phosphor, and the change of the speed of the intensifying screen depending on a change of the tube voltage tends to be great, thus leading to difficulties in setting the condition of radiography.
  • Another object of the present invention is to provide a radiographic image conversion screen which, when used as a fluorescent screen in association with a photographic camera or an X-ray television system, has a speed at least equal to the speed of a conventional fluorescent screen using a green emitting rare earth phosphor and is capable of providing an image having an improved contrast over the conventional fluorescent screen.
  • the present inventors have found that the above objects can be accomplished by using a combination of a rare earth phosphor capable of emitting green light upon exposure to radiation and a phosphor capable of emitting blue light upon exposure to radiation in such a manner as to form a double layer structure wherein a fluorescent layer composed of the green emitting rare earth phosphor is disposed on the surface side (i.e. the output side of the emitted light) and a fluorescent layer composed of the blue emitting phosphor is disposed on the side facing a support.
  • the present invention provides a radiographic image conversion screen which comprises a support, a first fluorescent layer formed on the support and consisting essentially of a blue emitting phosphor and a second fluorescent layer formed on the first fluorescent layer and consisting essentially of a green emitting rare earth phosphor.
  • the radiographic image conversion screen of the present invention has a fluorescent layer composed essentially of a blue emitting phosphor interposed between the support and the fluorescent layer composed essentially of a green emitting rare earth phosphor, and thus is capable of emitting blue and green lights, and it has a speed at least equal to the speed of the conventional radiographic image conversion screens comprising only the green emitting rare earth phosphor layer. Further, it provides an image having superior image quality, particularly superior contrast, as compared with the conventional radiographic image conversion screens, and when used as an intensifying screen in combination with an ortho-type film, it provides improved sharpness over the conventional intensifying screens and the dependability of its speed against the X-ray tube voltage is thereby improved.
  • the radiographic image conversion screen of the present invention can be prepared in the following manner.
  • a coating dispersion of the phosphor having an optimum viscosity.
  • the coating dispersion of the phosphor is applied onto a support made of e.g. paper or plastic by means of a doctor blade, roll coater or knife coater.
  • a reflective layer such as a white pigment layer, an absorptive layer such as a black pigment layer or a metal foil layer is interposed between the fluorescent layer and the support.
  • a reflective layer, an absorptive layer or a metal foil layer maybe preliminarily formed on a support and then a blue emitting phosphor layer may be formed thereon in the above mentioned manner.
  • a coating dispersion comprising a green emitting rare earth phosphor and a binder resin such as nitrocellulose, is prepared in the same manner as described above, and the coating dispersion thus prepared is applied onto the blue emitting phosphor layer to form a fluorescent layer composed essentially of the green emitting rare earth phosphor.
  • radiographic image conversion screens are usually provided with a transparent protective layer on the fluorescent layer. It is preferred also in the radiographic image conversion screens of the present invention to provide a transparent protective layer on the fluorescent layer composed essentially of the green emitting phosphor.
  • the process may advantageously be modified in such a manner that firstly a protective layer is formed on a flat substrate such as a glass plate or a plastic sheet, and then a coating dispersion composed of a mixture comprising the green emitting rare earth phosphor, the blue emitting phosphor and a binder resin, is coated on the protective layer and gradually dried at room temperature while controlling the ambient atmosphere.
  • the green emitting rare earth phosphor grains having a greater mean grain size or specific gravity will settle to form an under layer while the blue emitting phosphor grains having a smaller mean grain size or specific gravity are pushed upwardly to form a top layer, whereby two separate fluorescent layers, i.e. a top layer composed essentially of the blue emitting phosphor and an under layer composed essentially of the green emitting rare earth phosphor, are obtainable.
  • the integrally formed protective and fluorescent layers are peeled -off from the substrate, and placed on a support so that the top layer composed essentially of the blue emitting phosphor is brought in contact with and fixed to the support, whereby a radiographic image conversion screen of the present invention, is obtainable.
  • the separation between the green emitting rare earth phosphor grains and the blue emitting phosphor grains may not be complete, i.e. a certain minor amount of the green emitting rare earth phosphor grains may be present in the fluorescent layer composed essentially of the blue emitting phosphor and likewise a certain minor amount of the blue emitting phosphor grains may be present in the fluorescent layer composed essentially of the green emitting rare earth phosphor. It has been confirmed that so long as the first fluorescent layer, i.e. the layer adjacent to the support, is composed essentially of the blue emitting phosphor and the second fluorescent layer, i.e. the layer on the surface side (i.e.
  • the emission output side is composed essentially of the green emitting rare earth phosphor
  • the radiographic image conversion screen thereby obtainable has characteristics substantially equal to the characteristics of the above mentioned radiographic image conversion screen obtained by separately coating the blue emitting phosphor layer and the green emitting rare earth layer on the support.
  • Figure 1 shows a diagrammatic cross sectional view of a radiographic image conversion screen of the present invention prepared in the above mentioned manners.
  • a first fluorescent layer 12 consisting essentially of a blue emitting phosphor is provided on a support 11, and a second fluorescent layer 13 consisting essentially of a green emitting rare earth phosphor is formed on the first fluorescent layer 12.
  • Reference numeral 14 designates a transparent protective layer formed on the surface of the second fluorescent layer 13.
  • the blue emitting phosphor layer of the radiographic image conversion screen of the present invention may be formed in such a manner that firstly the blue emitting phosphor grains are classified into a plurality of groups having different mean grain sizes by means of a proper phosphor grain separation means such as levigation, and the groups of the phosphor grains thus classified are respectively dispersed in a proper binder resin and sequentially applied onto the support and dried so that the phosphor grains having a smaller mean grains are coated first, whereby the blue emitting phosphor layer is formed to have a grain size distribution of the phosphor grains such that the grain size becomes smaller gradually from the side facing the green emitting rare earth phosphor layer to the side facing the support.
  • FIG. 2 shows a diagrammatic cross sectional view of a radiographic image conversion screen of the present invention prepared in the above mentioned manner.
  • a first fluorescent layer 22 composed essentially of a blue emitting phosphor
  • a second fluorescent layer 23 composed essentially of a green emitting rare earth phosphor and a transparent protective layer 24 are laminated in this order on a support 21.
  • the blue emitting phosphor grains in the first layer 22 are arranged in such a manner that the phosphor grain size becomes smaller gradually from the side facing the green emitting phosphor layer 23 toward the side facing the support 21.
  • Such a radiographic image conversion screen provides substantially improved sharpness over the radiographic image conversion screen illustrated in Figure 1.
  • the green emitting rare earth phosphors which may be used in the radiographic image conversion screens of the present invention, include a phosphor composed of a terbium-activated rare earth oxysulfide of at least one rare earth element selected from yttrium, lanthanum, gadolinium and lutetium, a phosphor composed of an oxyhalide of the above rare earth elements (provided that the phosphor contains at least 0.01 mole of terbium per mole of the phosphor), a phosphor composed of a borate of the above rare earth elements, a phosphor composed of a phosphate of the above rare earth elements and a phosphor composed of a tantalate of the above rare earth elements.
  • the green emitting rare earth phosphors contain at least one lanthanide element or yttrium as the host material of the phosphors and are capable of emitting green light with high efficiency when excited by the X-rays.
  • Particularly preferred among them in view of the emission efficiency and granularity are a terbium activated or terbium-thulium activated rare earth oxysulfide phosphor represented by the formula (LN 1-a-b , Tb a , Tm b ) 2 0 2 S where Ln is at least one selected from lanthanum, gadolinium and lutetium, and a and b are numbers meeting the conditions of 0.0005 ⁇ a ⁇ 0.09 and 0 s b ⁇ 0.01, respectively, and a terbium activated or terbium-thulium activated rare earth oxysulfide phosphor represented by the formula (Y 1-i-a-b , Ln., Tb Tm b ) 2 O
  • any blue emitting phosphor may be used for the radiographic image conversion screens of the present invention so long as it is a phosphor capable of emitting blue light with high efficiency when excited by radiation such as X-ray radiation.
  • rMe"SO 4 mEu 2+ , nTb 3+
  • Me is at least one selected from magnesium, calcium, strontium and barium
  • each of Me' and Me is at least one selected from calcium, strontium and barium
  • each of X and X' is at least one selected from chlorine and bromine
  • p, q, r, m and n are numbers meeting the conditions of 0.80 ⁇ p ⁇ 1.5, 0 ⁇ q ⁇ 2.0, 0 ⁇ r ⁇ 1.0, 0.001 ⁇ m ⁇ 0.10 and 0 ⁇ n ⁇ 0.05, respectively
  • a rare earth oxyhalide phosphor represented by the formula (Ln' 1-x-y-z , Tb x , Tm y Yb z )OX where Ln' is at least one selected from lanthanum and gadolinium, X is at least one selected from chlorine and bromine, and x, y and z are numbers meeting the conditions of
  • the phosphor to be used for the blue emitting phosphor layer preferably has a mean grain size of from 2 to 10 11 , more preferably from 3 to 6 ⁇ , and a standard deviation of from 0.20 to 0.50, more preferably from 0.30 to 0.45, as represented by the quartile deviation
  • the phosphor to be used for the green emitting phosphor layer preferably has a mean grain size of from 5 to 20 ⁇ , more preferably from 6 to 12 ⁇ and a standard deviation of from 0.15 to 0.40, more preferably from 0.20 to 0.35, as represented by the quartile deviation.
  • the coating weight of the phosphor in the blue emitting phosphor layer and the coating weight of the phosphor in the green emitting phosphor layer are preferably from 2 to 100 mg/cm and from 5 to 2 2 1 00 mg/cm 2 , respectively and more preferably from 3 to 50 mg/cm and from 20 to 80 mg/cm 2 , respectively.
  • the mean grain size of the phosphor grains in the blue emitting phosphor layer is smaller than the mean grain size of the phosphor grains in the green emitting rare earth phosphor layer.
  • Figure 3 shows an emission spectrum according to a conventional radiographic image conversion screen comprising a single fluorescent layer composed solely of (Gd 0.995 , Tb 0.005 ) 2 O 2 S phosphor as one of green emitting rare earth phosphors.
  • Figures 4 and 5 show emission spectra obtained by the radiographic image conversion screens of the present invention.
  • the blue emitting phosphor layer (the coating weight of the phosphor: 20 mg/cm 2 ) is composed of (Y 0.998 , Tb 0.002 ) 2 O 2 S phosphor
  • the green emitting phosphor layer (the coating weight of the phosphor: 30 mg/cm 2 ) is composed of (GdO.
  • the blue emitting phosphor layer (the coating weight of the phosphor: 15 mg/cm 2 ) is composed of BaF 2 ⁇ BaCl 2 ⁇ 0.1 KCl ⁇ 0.1 BaS0 4 : 0 .06 Eu 2+ phosphor
  • the green emitting phosphor layer (the coating weight of the phosphor: 35 mg/cm 2 ) is composed of (Gd 0.995 , Tb 0.005 ) 2 O 2 S phosphor.
  • the broken line and the alternate long and short dash line indicate a spectral sensitivity curve of an ortho-type film and a spectral sensitivity curve of an image tube, respectively. It is apparent from the comparison of Figure 3 with Figure 4 or 5, that the radiographic image conversion screen of the present invention has a wide emission distribution ranging from the green region to the blue region or the near ultraviolet region and better matches the spectral sensitivities of the ortho-type film and the photocathode of the image tube than the conventional radiographic image conversion screen comprising a single fluorescent layer composed solely of the green emitting rare earth phosphor, and it is advantageous particularly in view of its high speed.
  • Figure 6 illustrates a relation between the ratio (represented by percentage) of the coating weight of the phosphor in the blue emitting phosphor layer to the coating weight of the total phosphor in the entire fluorescent layers in the radiographic image conversion screens of the invention and the speed of the radiographic image conversion screens thereby obtained.
  • the relative speed on the vertical axis indicates the speed obtained in combination with an ortho-type film, in a relative value based on the speed of the screen having no blue emitting phosphor layer (i.e. comprising only the green emitting rare earth phosphor layer) where the latter speed is set to be 100.
  • the curves a, b, c, d, e and f represent the cases where the blue emitting phosphor layer is composed of (Y 0.998 , Tb 0.002 ) 2 O s S phosphor, (Gd 0.5 , Y 0.495 , Tb 0.003 , Tm 0.002 ) 2 O 2 S phosphor, BaF2.
  • BaCl 2 ⁇ 0.1 KCl ⁇ 0.1 BaSO 4 0.06 Eu 2+ phosphor, (La 0.997 , Tb 0,003 )OBr phosphor, CdWO 4 phosphor, and CaWO 4 phosphor, respectively.
  • the total coating weight of the fluorescent layers is 50 mg/cm 2
  • the green emitting rare earth phosphor layer is composed of (Gd 0.995 , Tb 0 ⁇ 005 ) 2 O 2 S phosphor.
  • Figure 7 illustrates a relation between the ratio (represented by percentage) of the coating weight of the phosphor in the blue emitting phosphor layer to the total coating weight of the phosphors in the entire fluorescent layers of the radiographic image conversion screens of the present invention and the sharpness of the radiographic image conversion screen.
  • curves a, b, c, d, e and f represent the cases where the blue emitting phosphor layer is composed of (Y 0 ⁇ 998, Tb 0.002 ) 2 2 O 2 S phosphor, (Gd 0.5 , Y 0.495 , Tb 0.003 , Tm 0.002 ) 2 O 2 S phosphor, BaF 2 ⁇ BaCl 2 ⁇ 0. 1 KCl ⁇ 0.
  • each radiographic image conversion screen is determined by obtaining a MTF value at a film density of 1.5 and spatial frequency of 2 lines/mm, and the MTF value is indicated in a relative value based on the MTF value of the radiographic image conversion screen having no blue emitting phosphor layer (i. e. comprising only the green emitting rare earth phosphor layer) where the latter MTF value is set to be 100.
  • radiographic conversion screens of the present invention provided with a blue emitting phosphor layer beneath the green emitting phosphor layer have improved sharpness over the conventional screen having no such a blue emitting phosphor layer.
  • Figure 8 is a graph illustrating the dependency of the speeds of the radiographic image conversion screens of the present invention and the conventional radiographic image conversion screen, on the X-ray tube voltage.
  • curves a, b, c, d and e represent the speeds of the radiographic image conversion screens of the present invention in which the blue emitting phosphor layer is composed of (Y 0,998 , Tb 0.002 ) 2 O 2 S phosphor, BaF 2 ⁇ BaCl 2 ⁇ 0.1 KCl ⁇ 0.1 BaSO 4 : 0.06 Eu 2+ phosphor, (LaO.
  • the green emitting phosphor layer is (Gd 0.995 , Tb 0.005 ) 2 0 2 S phosphor in each case.
  • the coating weight of the green emitting phosphor is 30 mg/cm and the coating weight of the blue emitting phosphor is 20 mg/cm 2 .
  • Curve f represents the speed of the conventional radiographic image conversion screen wherein the fluorescent layer is composed solely of (Gd 0.995 , Tb 0,005 ) 2 O 2 S and the coating weight of the phosphor is 50 mg/cm 2 .
  • the vertical axis of Figure 8 indicates the speed obtained by a combination of each radiographic image conversion screen with an ortho-type film, as a relative value against the speed of the radiographic conversion screen comprising a single fluorescent layer of CaWO 4 phosphor (as combined with a regular-type film). The relative value is spotted for every X-ray tube voltage.
  • the radiographic image conversion screens thereby obtainable have a speed at least equal to the speed of the conventional screen comprising a single fluorescent layer composed solely of the green emitting rare earth phosphor, so long as the ratio of the coating weight of the phosphor in the blue emitting phosphor layer to the total coating weight of the entire phosphors falls within the specific range, as in the case of the radiographic image conversion screens illustrated in Figure 6, and the sharpness can be improved and the dependency of the speed on the X-ray tube voltage can be reduced as compared with the conventional radiographic image conversion screen comprising a single fluorescent layer composed solely of the green emitting rare earth phosphor, as in the cases of the radiographic image conversion screens illustrated in Figures 7 and 8.
  • the radiographic image conversion screens of the present invention provides improved contrast as compared with the conventional radiographic image conversion screen comprising only the green emitting rare earth phosphor layer.
  • the conventional radiographic image conversion screen comprising only the green emitting rare earth phosphor layer.
  • the radiographic image conversion screens of the present invention have a speed at least equal to the speed of the conventional radiographic image conversion screens comprising only a green emitting phosphor layer and they provide improved sharpness and contrast without degradation of the image quality, particularly the granularity, and their speed is less dependent on the X-ray tube voltage and thus provides an advantage that the condition for the operation of radiography can thereby be simplified.
  • the radiographic image conversion screens of the present invention have a high speed and provide an image having superior image quality, and their industrial value is extremely high.
  • Radiographic image conversion screens (1) to (26) were prepared in the following manner with use of the respective combinations of a green emitting rare earth phosphor and a blue emitting phosphor, as identified in Table 1 given hereinafter.
  • a green emitting rare earth phosphor 8 parts by weight of a green emitting rare earth phosphor and one part by weight of nitrocellulose were mixed with use of a solvent to obtain a coating dispersion of the phosphor.
  • This coating dispersion of the phosphor was uniformly coated by means of a knife coater on the above mentioned blue emitting phosphor layer so that the coating weight of the phosphor became as shown in Table 1 given hereinafter, whereby a green emitting rare earth phosphor layer was formed.
  • nitrocellulose was uniformly coated on the green emitting rare earth phosphor layer to form a transparent protective layer having a thickness of about 10u.
  • the coating dispersions were sequentially uniformly coated by a knife coater and dried on a polyethylene terephthalate support provided on its surface with an absorptive layer of carbon black and having a thickness of 250 ⁇ in such order that a group of the phosphor grains having smaller grain size was applied first, so that the coating weight of the phosphor of each group became 5 mg/cm 2 , whereby a plurality of fluorescent layers composed of (Y 0.998 , Tb 0.002 ) 2 O 2 S and having different phosphor grain sizes were formed.
  • nitrocellulose was uniformly coated on the (Gd 0.995 , Tb 0.005 ) 2 O 2 S phosphor layer and dried to form a transparent protective layer having a thickness of about 10 ⁇ .
  • a radiographic image conversion screen (27) was prepared.
  • Radiographic image conversion screens (28) to (30) were prepared in the following manner with use of the respective combinations of a green emitting rare earth phosphor and a blue emitting phosphor, as indicated in Table 1 given hereinafter.
  • the green emitting rare earth phosphor and the blue emitting phosphor were preliminarily mixed in the proportions corresponding to the respective coating weights of the green emitting rare earth phosphor layer and the blue emitting phosphor layer. Eight parts of the phosphor mixture and one part of nitrocellulose were mixed together with a solvent to obtain a coating dispersion of the phosphors.
  • a protective layer was coated on a smooth substrate and dried to have a thickness of 10 11 , and the above coating dispersion of the phosphors was then coated on the protective layer so that the total coating weight of the phosphors became 50 mg/cm 2 .
  • the coated phosphor layer was dried by leaving it to stand still at a constant temperature of 15°C for 10 hours while controlling the replacement of ambient air, whereby the green emitting phosphor grains and the blue emitting phosphor grains were settled to separate from one another.
  • the phosphor layer having the protective layer was peeled off from the flat substrate and heat laminated on a support coated with a thermoplastic binder, whereby a radiographic image conversion screen comprising a double phosphor layer structure, i.e. a first fluorescent layer composed essentially of the blue emitting phosphor and a second fluorescent layer composed essentially of the green emitting phosphor, was obtained.
  • Fluorometallic radiographic image conversion screens (31) to (33) were prepared with use of the respective combinations of a green emitting rare earth phosphor and a blue emitting phosphor, as indicated in Table 2 given hereinafter, in the same manner as in Examples 1 to 26 except that a paper support having a thickness of 250 11 and provided on its surface with a lead foil having a thickness of 30 11 was used.
  • a radiographic image conversion screen (R) was prepared in the same manner as in Examples 1 to 26 except that (Gd 0.995 , Tb 0.005 ) 2 O 2 S phosphor having a mean grain size of 8 11 , and a standard deviation (i.e. quartile deviation) of 0.30 was used and a single fluorescent layer having a coating weight of the phosphor of 50 mg/cm was formed on the support.
  • a radiographic image conversion screen (R') was prepared in the same manner as in Examples 31 to 33 except that the same phosphor as used in Refrerence Example R was used.
  • radiographic image conversion screens of the present invention are superior to the conventional radiographic image conversion screen (R) in the speed, sharpness and contrast, and no substantial degradation in their granularity was observed.
  • the radiographic image conversion screens of the invention were found to be superior to the conventional radiographic image conversion screen (R') in the speed and penetrameter sensitivity. Further, it has been confirmed that the radiographic image conversion screens (31) to (33) can effectively used also for high voltage radiography and cobaltgraphy in medical diagnosis.
  • each radiographic image conversion screen listed in the following Table 1 were obtained by radiography conducted with use of Ortho G Film (manufactured by Eastman Kodak Co.) and the X-rays generated at the X-ray tube voltage of 80 KVp and passed through a water-phantom having a thickness of 80 mm.
  • the respective values in the Tables indicate the following values.
  • Speed A relative value based on the speed of a radiographic image conversion screen comprising a fluorescent layer of CaWO 4 phosphor (KYOKKO FS, manufactured by Kasei Optonix, Ltd.) where the latter speed is set to be 100.
  • Sharpness A relative value of the MTF value obtained .
  • a MTF value was obtained at a spatial frequency of 2 lines/mm, and it was represented by a relative value based on the MTF value of a radiographic image conversion screen comprising a single fluorescent layer composed solely of (Gd 0.995 , Tb 0.005 ) 2 O 2 S phosphor, obtained at the same spatial frequency, where the latter MTF value was set to be 100.
  • Granularity A RMS value at a film density of 1. 0 and spatial frequency of 0. 5 to 5. 0 lines /mm.
  • Contrast Photographs were taken through Al having a thickness of 1 mm and Al having a thickness of 2 mm, and the respective contrasts were obtained from the differences of the film densities. Each contrast was represented by a relative value based on the contrast obtained by a radiographic image conversion screen comprising a fluorescent layer composed of CaWO 4 phosphor (KYOKKO FS, manufactured by Kasei Optonix, Ltd.) where the latter contrast was set to be 100.
  • KYOKKO FS CaWO 4 phosphor
  • the speed and penetrameter sensitivity were obtained by radiography conducted with use of Ortho G Film (manufactured by Eastman Kodak Co.) and a steel plate having a thickness of 20 mm as the object and with X-rays generated at the X-ray tube voltage of 200 KVp.
  • Speed A relative value based on the speed of the fluorometalic radiographic image conversion screen (R') where the latter speed is set to be 100.
  • Penetrameter sensitivity Represented by the following formula.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Luminescent Compositions (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)
EP82104798A 1982-03-15 1982-06-01 Umwandlungsschirm für radiographisches Bild Expired EP0088820B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP57039310A JPS58156899A (ja) 1982-03-15 1982-03-15 放射線像変換スクリ−ン
JP39310/82 1982-03-15
JP79437/82 1982-05-12
JP7943782A JPS58196287A (ja) 1982-05-12 1982-05-12 放射線像変換スクリ−ンの製造方法

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EP0088820A1 true EP0088820A1 (de) 1983-09-21
EP0088820B1 EP0088820B1 (de) 1987-02-04

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KR (1) KR900004329B1 (de)
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178592A2 (de) * 1984-10-17 1986-04-23 Kasei Optonix, Ltd. Verstärkungsschirme
EP0240053A1 (de) * 1986-03-19 1987-10-07 Koninklijke Philips Electronics N.V. Strahlungsumwandlungsschirm
EP0407890A2 (de) * 1989-07-12 1991-01-16 Minnesota Mining And Manufacturing Company Kassette mit Verstärkungsfolie zur Verwendung mit einem Röntgenfilm
EP0412730A2 (de) * 1989-08-09 1991-02-13 Minnesota Mining And Manufacturing Company Verbesserte Kassette und Röntgenfilm-Kombination
WO2010015955A2 (en) 2008-08-07 2010-02-11 Koninklijke Philips Electronics N.V. Scintillating material and related spectral filter
US20120049118A1 (en) * 2008-12-30 2012-03-01 Centre National De La Recherche Scientifique Ceramic scintilator body and scintillation device
US9316750B2 (en) 2012-03-12 2016-04-19 Fujifilm Corporation Radiation image detecting device and radiation image capturing system
US9638807B2 (en) 2008-08-07 2017-05-02 Koninklijke Philips N.V. Scintillating material and related spectral filter

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KR100426393B1 (ko) * 2002-01-14 2004-04-08 강희동 방사선영상 저장 형광체 및 그 제조방법
JP6077787B2 (ja) * 2012-08-22 2017-02-08 キヤノン株式会社 放射線撮像装置及び放射線撮像システム

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US3725704A (en) * 1971-01-28 1973-04-03 Lockheed Aircraft Corp Rare earth phosphors for x-ray conversion screens
FR2167011A5 (de) * 1971-12-31 1973-08-17 Agfa Gevaert
FR2167535A5 (de) * 1972-01-11 1973-08-24 United States Radium Corp
FR2205683A1 (de) * 1972-11-03 1974-05-31 Agfa Gevaert

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US3725704A (en) * 1971-01-28 1973-04-03 Lockheed Aircraft Corp Rare earth phosphors for x-ray conversion screens
FR2167011A5 (de) * 1971-12-31 1973-08-17 Agfa Gevaert
FR2167535A5 (de) * 1972-01-11 1973-08-24 United States Radium Corp
FR2205683A1 (de) * 1972-11-03 1974-05-31 Agfa Gevaert

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0178592A2 (de) * 1984-10-17 1986-04-23 Kasei Optonix, Ltd. Verstärkungsschirme
EP0178592A3 (en) * 1984-10-17 1986-11-20 Kasei Optonix, Ltd. Intensifying screens
US4696868A (en) * 1984-10-17 1987-09-29 Kasei Optonix, Ltd. Intensifying screens
EP0240053A1 (de) * 1986-03-19 1987-10-07 Koninklijke Philips Electronics N.V. Strahlungsumwandlungsschirm
EP0407890A3 (en) * 1989-07-12 1991-03-27 Minnesota Mining And Manufacturing Company Cassette with intensifying screens to be used with an x-ray film
EP0407890A2 (de) * 1989-07-12 1991-01-16 Minnesota Mining And Manufacturing Company Kassette mit Verstärkungsfolie zur Verwendung mit einem Röntgenfilm
EP0412730A2 (de) * 1989-08-09 1991-02-13 Minnesota Mining And Manufacturing Company Verbesserte Kassette und Röntgenfilm-Kombination
EP0412730A3 (en) * 1989-08-09 1992-03-25 Minnesota Mining And Manufacturing Company An improved cassette and radiographic film combination
WO2010015955A2 (en) 2008-08-07 2010-02-11 Koninklijke Philips Electronics N.V. Scintillating material and related spectral filter
WO2010015955A3 (en) * 2008-08-07 2011-01-20 Koninklijke Philips Electronics N.V. Scintillating material
US8492724B2 (en) 2008-08-07 2013-07-23 Koninklijke Philips Electronics N.V. Scintillating material and related spectral filter
US9638807B2 (en) 2008-08-07 2017-05-02 Koninklijke Philips N.V. Scintillating material and related spectral filter
US20120049118A1 (en) * 2008-12-30 2012-03-01 Centre National De La Recherche Scientifique Ceramic scintilator body and scintillation device
US8877093B2 (en) * 2008-12-30 2014-11-04 Saint-Gobain Ceramics & Plastics, Inc. Ceramic scintillator body and scintillation device
US9316750B2 (en) 2012-03-12 2016-04-19 Fujifilm Corporation Radiation image detecting device and radiation image capturing system

Also Published As

Publication number Publication date
KR840000948A (ko) 1984-03-26
DE3275420D1 (en) 1987-03-12
EP0088820B1 (de) 1987-02-04
KR900004329B1 (ko) 1990-06-22

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