JPH1144798A - Radiation intensifying screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of sensitivity and improve granularity and sharpness in a general medical photographic radiation intensifying screen or a mammographic radiation intensifying screen. SOLUTION: A general medical photographic radiation intensifying screen is provided with a powder layer 2 made of at least one kind of metal selected from W and Mo or a compound containing the metal and having the thickness in the range of 10-100 μm on a base 1. A phosphor layer 3 is formed on the powder layer 2, and a protective film 4 is provided on it. A mammographic radiation intensifying screen is provided with a powder layer made of at least one kind of metal selected from Y and Zr or a compound containing the metal and having the thickness in the range of 10-100 μm on a base. A phosphor layer is formed on the powder layer, and a protective film is provided on it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic intensifying screen used for radiography and the like, and more particularly to a radiographic intensifying screen for general medical radiography and mammography.

[0002]

2. Description of the Related Art In the field of medical diagnosis, radiography such as X-ray photography is used for examining parts such as the chest, abdomen, and head. X-ray photography is also applied. With the increasing trend of breast cancer in women, efforts have been made to detect breast cancer early, and X-ray imaging of the breast, which is effective for early detection of breast cancer, has been applied.

[0003] Here, for X-ray photography in medical diagnosis of general parts such as the chest, abdomen, and head, an X-ray tube having a tube voltage of about 50 to 120 kV is used as an X-ray source. On the other hand, in X-ray imaging of the breast, contrast must be obtained at a high resolution in a lime portion or an abnormal soft tissue. Therefore, an X-ray tube having a tube voltage of about 25 to 32 kV and using molybdenum as a target is used as an X-ray source. Such an X-ray source can efficiently generate characteristic X-rays of 17.4 keV and 19.5 keV.

In X-ray photography or the like used for medical diagnosis as described above, a radiation film is usually used in combination with a radiographic intensifying screen in order to improve the sensitivity of the radiography system. As a radiographic intensifying screen used for X-ray photography or the like, a phosphor intensifying layer and a relatively thin protective film for protecting the phosphor layer are sequentially formed on a support made of paper, plastic, or the like. . In addition, since an X-ray source different from that used for general medical imaging is used for X-ray imaging of the breast as described above, a radiographic intensifying screen for X-ray imaging of the breast (radiation intensifying screen for mammography) is compatible therewith. Characteristics are required.

[0005] In recent years, there has been an increasing demand for reduction of the radiation exposure of subjects in medical diagnosis and the like. Therefore, for example, in direct X-ray imaging, the radiation exposure of the subject is reduced by using a radiation film or a radiographic intensifying screen with high sensitivity. As a method of increasing the sensitivity, it is common to use a high-sensitivity film for a radiation film, and to use a phosphor with high luminous efficiency, increase the phosphor coating weight, and reflectivity for a radiographic intensifying screen. Techniques such as the use of a support have been applied.

However, when a high-sensitivity film is used,
A decrease in sharpness is small, but causes a decrease in graininess. On the other hand, when the sensitivity of the radiographic intensifying screen is increased, there is a problem in that the graininess or the sharpness is reduced by any of the above methods. The discriminating ability of a subject in X-ray imaging is related to both graininess and sharpness, and there is a problem that deterioration of graininess lowers discriminating ability of a subject having a particularly low contrast.

[0007]

As described above, increasing the sensitivity of a radiographic intensifying screen, particularly the use of a phosphor having high luminous efficiency, is effective for reducing the amount of exposure of a subject, but it is effective in reducing granular exposure. This leads to a problem of deteriorating properties and sharpness. Conversely, if a phosphor with low luminous efficiency is used, there is some reciprocity between the obtained photographic properties, such as improvement in graininess but decrease in sensitivity. It was difficult to satisfy both graininess and sharpness with paper. Such a decrease in granularity and sharpness is a problem because the diagnostic ability is reduced in both radiographic intensifying screens for general medical imaging and mammography.

The present invention has been made to address such a problem, and provides a radiographic intensifying screen capable of improving sharpness and graininess while suppressing a decrease in sensitivity. It is intended that, more specifically, in correspondence with the radiographic conditions, sensitivity, sharpness, radiographic intensifying screen that enables to improve the granularity, such as radiographic intensifying screen for general medical imaging and It is intended to provide a radiographic intensifying screen for mammography.

[0009]

Means for Solving the Problems The present inventors have studied the reduction in graininess when using a radiographic intensifying screen with high sensitivity, particularly a radiographic intensifying screen using a phosphor having high luminous efficiency. However, it has been found that the transmitted X-rays that have passed through the radiation intensifying screen are scattered, and a part of the transmitted X-rays is incident on the phosphor layer again to cause the phosphor layer to emit light, so that graininess and sharpness are reduced. Such a decrease in graininess and sharpness due to scattered X-rays is particularly remarkable in the case of a radiographic intensifying screen using a phosphor having high luminous efficiency.

[0010] The present invention has been made based on such knowledge, and the first radiographic intensifying screen in the present invention is formed on a support and on the support as described in claim 1. A fluorescent intensifying screen comprising a phosphor layer and a protective film provided on the phosphor layer, wherein at least one metal selected from tungsten and molybdenum is interposed between the support and the phosphor layer. Alternatively, a powder layer made of a compound containing the metal and having a thickness in the range of 10 to 100 μm is provided.

In the first radiographic intensifying screen, it is preferable that the powder layer is made of particles of the metal, for example, as described in claim 2. Such a first radiographic intensifying screen is, for example, an X-ray tube having a tube voltage of about 50 to 120 kV as an X-ray intensifying screen for general medical imaging, that is, as an X-ray source, as described in claim 3. This is used as an X-ray intensifying screen when is used.

The second radiographic intensifying screen according to the present invention is, as described in claim 4, a support, a phosphor layer formed on the support, and a protective layer provided on the phosphor layer. In a radiographic intensifying screen comprising a film, between the support and the phosphor layer, at least one metal selected from yttrium and zirconium, or a compound containing the metal, and a thickness of 10 to 10 It is characterized in that a powder layer in the range of 100 μm is provided.

In the second radiographic intensifying screen, the powder layer is preferably made of, for example, the metal compound particles as described in claim 5. Such a second radiographic intensifying screen is, for example, as an X-ray intensifying screen for mammography, that is, having a tube voltage of about 25 to 32 kV and using molybdenum as a target, as described in claim 6.
It is used as an X-ray intensifying screen when an X-ray tube generating characteristic X-rays of 7.4 keV and 19.5 keV is used as an X-ray source.

For example, when an X-ray tube having a tube voltage of about 50 to 120 kV is applied as an X-ray source, the first radiographic intensifying screen of the present invention used as an X-ray intensifying screen for general medical imaging, etc. Since a powder layer containing at least one kind of metal selected from tungsten and molybdenum having a large X-ray absorption capacity as described above is provided between the support and the phosphor layer, scattered X-rays are generated. It can be efficiently absorbed by the powder layer. Therefore, the probability that the scattered X-rays re-enter the phosphor layer is reduced, and a decrease in granularity and sharpness due to secondary light emission of the phosphor layer can be suppressed.

Further, when an X-ray tube having a tube voltage of about 25 to 32 kV is used as an X-ray source, for example, the second radiographic intensifying screen of the present invention used as an X-ray intensifying screen for mammography, etc. A powder layer containing at least one metal selected from the group consisting of yttrium and zirconium having a large absorption capacity for characteristic X-rays of 17.4 keV and 19.5 keV as described above, between the support and the phosphor layer. Scatter X
The wire can be efficiently absorbed by the powder layer. Therefore,
The probability that the scattered X-rays re-enter the phosphor layer is reduced, and a decrease in granularity and sharpness due to secondary emission of the phosphor layer can be suppressed.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing the structure of an embodiment of the first radiographic intensifying screen of the present invention. In FIG. 1, reference numeral 1 denotes a support made of a plastic film, a nonwoven fabric, or the like, and tungsten (W) is provided on one surface of the support 1.
And a powder layer 2 made of at least one metal selected from molybdenum (Mo) or a compound containing the metal and having a thickness of 10 to 100 μm.

A phosphor layer 3 is provided on the powder layer 2 described above. As the phosphor constituting the phosphor layer 3, general CaWO ₄ or the like may be used, but a rare earth phosphor such as Gd ₂ O ₂ S: Tb or LaOBr: Tb, which has particularly high luminous efficiency, is used. Is preferred. The radiographic intensifying screen of the present invention is suitable for improving the graininess and sharpness when using such a rare-earth phosphor having high luminous efficiency. The phosphor layer 3 is a layer containing such phosphor particles.

On the phosphor layer 3, there is provided a protective film 4 made of a plastic film or a plastic coating film, etc., thereby providing a radiation intensifying screen such as an X-ray intensifying screen 5 used for medical diagnosis or the like. Is configured. The X-ray intensifying screen 5 according to the first embodiment has a tube voltage of about 50 to 120 kV, and uses an X-ray tube that mainly generates continuous X-rays as an X-ray source, and uses a chest, abdomen, and a head. It is suitable as an intensifying screen for X-ray imaging of a general part such as a part for medical diagnosis. That is, it is suitable as an X-ray intensifying screen for general medical imaging.

As the particles constituting the powder layer 2 described above, at least one kind of metal particles selected from W and Mo or compound particles containing at least one kind of metal selected from W and Mo are used. These can be used as a mixture. Examples of the compound containing W and Mo include oxides, carbides, and intermetallic compounds. Although not particularly limited to the form of the compound, it is preferable to use a compound in which the amount of W or Mo is 50% by weight or more. Is preferred. When the amount of W or Mo in the compound is less than 50% by weight,
There is a possibility that the scattered X-ray absorption effect described later cannot be sufficiently obtained. In other words, the amount of W and Mo is 50 weight
% Or more of the compound can provide substantially the same effect as when W or Mo metal particles are used. However, it is preferable to use W or Mo metal particles from the viewpoint of the effect of absorbing scattered X-rays.

W and Mo have a large absorption capacity for X-rays emitted from the X-ray tube having a tube voltage of about 50 to 120 kV. Therefore, even if the X-rays irradiated from the support 1 side are scattered by the phosphor layer 3, the protective film 4, etc.
The scattered X-rays can be efficiently absorbed by the powder layer 2. As described above, by efficiently absorbing the scattered X-rays in the powder layer 2, the probability that the scattered X-rays re-enter the phosphor layer 3 is reduced, so that the granularity and sharpness can be improved. Become.

That is, as shown in FIG. 2A, in the conventional X-ray intensifying screen 5 'having no powder layer 3 containing W or Mo, the X-rays 6 incident from the support 1 side emit fluorescent light. The phosphor particles reach the body layer 3 and cause the phosphor particles in the phosphor layer 3 to emit light (7). At this time, the incident X-rays 6 are scattered (scattered X-rays 6 ′), and when the scattered X-rays 6 ′ are incident on the phosphor layer 3 again, the phosphor layer 3 further emits light (secondary light emission (7 ')) This secondary emission reduces the graininess and sharpness of the X-ray photograph. Secondary light emission due to the scattered X-rays 6 ′ is particularly problematic when a phosphor having high luminous efficiency such as Gd ₂ O ₂ S: Tb or LaOBr: Tb is used for the phosphor layer 3.

On the other hand, the X-ray intensifying screen 5 according to the present invention
Has a powder layer 2 containing W and Mo between the support 1 and the phosphor layer 3, so that the incident X-rays 6 are scattered as shown in FIG. However, this scattered X-ray 6 '
Can be efficiently absorbed by the powder layer 2 containing W and Mo. Accordingly, the probability that the scattered X-rays 6 ′ reenter the phosphor layer 3 is reduced, and the secondary light emission of the phosphor layer 3 is suppressed. As described above, by suppressing the secondary light emission of the phosphor layer 3, it is possible to improve the graininess and sharpness of the X-ray photograph.

The thickness of the powder layer 2 containing W and Mo is 10 to 100
μm range. If the thickness of the powder layer 2 exceeds 100 μm, the intensity itself of the X-ray 6 passing through the subject such as a human body and entering the X-ray intensifying screen 5 may be reduced. That is, there is a high possibility that the sensitivity is reduced. On the other hand, if the thickness of the powder layer 2 is less than 10 μm, the ability to absorb the scattered X-rays 6 ′ decreases, and the effect of improving graininess and sharpness cannot be sufficiently obtained. The thickness of the powder layer 2 containing W and Mo is 20-80μ
More preferably, it is within the range of m.

The powder layer 2 containing W and Mo described above can be easily formed in the same manner as the phosphor layer 3. That is, at least one metal particle (metal powder) selected from W and Mo, or a compound particle (compound powder) containing at least one metal selected from W and Mo,
An appropriate amount of a binder is mixed with the mixture, and an organic solvent is further added thereto to prepare a powder coating liquid having an appropriate viscosity. The powder coating liquid is applied to the support 1 by a knife coater, a roll coater, or the like, and dried. Thus, a desired powder layer 2 is obtained. According to such a coating method, the powder layer 2 having the above-described thickness can be easily and inexpensively obtained.

As described above, in the X-ray intensifying screen 5 of the present invention, the scattered X-rays 6 ′ can be efficiently absorbed by the powder layer 2 containing W and Mo, so that the scattered X-rays 'Becomes incident on the phosphor layer 3 again, so that the graininess and sharpness can be improved. The effect of improving the graininess and sharpness can be obtained by a simple structure in which the powder layer 2 containing W or Mo is provided between the support 1 and the phosphor layer 3, so that the graininess and sharpness are improved. X improved
The line intensifying screen 5 can be easily and inexpensively manufactured.

According to the X-ray intensifying screen 5 of this embodiment, even when a rare earth phosphor such as Gd ₂ O ₂ S: Tb having high luminous efficiency is used for the phosphor layer 2, W and Mo are contained. Since the granularity and sharpness can be improved by the powder layer 2, when this is used for medical imaging (X-ray imaging) of general parts such as the chest, abdomen, and the head, the powder layer 2 Good diagnostic ability can be obtained after reducing the X-ray exposure.

In a conventional intensifying screen, a structure in which a lead metal foil is stuck on a support and a phosphor layer is formed thereon has been studied and partially put into practical use. In addition to the many problems described above, since the incident X-rays themselves are largely absorbed, this is contrary to increasing the sensitivity of the radiographic intensifying screen. In the present invention, it is possible to efficiently absorb scattered X-rays without reducing the intensity of incident X-rays by using the powder layer 2 containing W or Mo having an appropriate thickness. In addition, the productivity of the intensifying screen itself has been greatly improved.

The X-ray intensifying screen 5 of the embodiment described above is produced, for example, as follows. That is, as described above, metal particles of W or Mo (metal powder) or compound particles containing W or Mo (compound powder) are mixed with a binder in an appropriate amount, and an organic solvent is further added thereto to obtain an appropriate viscosity. A powder coating solution is prepared, and the powder coating solution is coated on the support 1 by a knife coater, a roll coater, or the like, and dried to obtain W or Mo.
Is formed.

Examples of the binder used for preparing the powder coating solution include nitrated cotton, cellulose acetate, ethyl cellulose, polyvinyl butyral, cottony polyester, polyvinyl acetate, vinylidene chloride-vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, Polyalkyl (meth) acrylate, polycarbonate, polyurethane, cellulose acetate butyrate, polyvinyl alcohol and the like can be used. As the organic solvent, for example, ethanol, methyl ethyl ether, butyl acetate, ethyl acetate, ethyl ether, xylene and the like are used. In addition, a dispersing agent such as phthalic acid and stearic acid and a plasticizer such as triphenyl phosphate and diethyl phthalate can be added to the powder coating liquid as needed.

Examples of the support 1 include polyesters such as cellulose acetate, cellulose propionate, cellulose acetate butyrate, and polyethylene terephthalate, polystyrene, polymethyl methacrylate, polyamide, and the like.
A resin formed of a resin such as polyimide, vinyl chloride-vinyl acetate copolymer, or polycarbonate can be used.

On the other hand, an appropriate amount of a phosphor is mixed with a binder, and an organic solvent is added thereto to prepare a phosphor coating solution having an appropriate viscosity, and the phosphor coating solution is coated with a protective film using a knife coater or a roll coater. 4 and dried to form a phosphor layer 2. As the binder and the organic solvent used for preparing the phosphor coating solution, those similar to the powder coating solution can be used. The protective film 4 is made of polyethylene terephthalate, polyethylene, polyvinylidene chloride,
A transparent resin film such as polyamide can be used. If necessary, a dispersant such as phthalic acid and stearic acid and a plasticizer such as triphenyl phosphate and diethyl phthalate can be added to the phosphor coating solution.

Some intensifying screens have a structure in which a light reflecting layer, a light absorbing layer and the like are provided between the support 1 and the phosphor layer 3. In such a case, the support 1 A light reflecting layer, a light absorbing layer, and the like may be formed thereon.

Then, the powder layer 2 containing W and Mo described above
And the protective film 4 on which the phosphor layer 3 is formed.
By laminating the above, an intended X-ray intensifying screen (radiation intensifying screen) 5 is obtained. The phosphor coating solution is directly applied onto the powder layer 2 containing W or Mo and dried, and then a film-like protective film 4 is laminated thereon, or cellulose acetate, nitrocellulose, cellulose acetate butyrate, etc. A protective film coating solution having a suitable viscosity by dissolving a resin such as cellulose derivative, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polycarbonate, polyvinyl butyral, polymethyl methacrylate, polyvinyl formal, and polyurethane in a solvent. Is applied and dried to form an X-ray intensifying screen 5
Can also be prepared.

Further, the X-ray intensifying screen 5 can be manufactured by a method other than the above-described manufacturing method. That is, the protective film 4 is formed on a smooth substrate in advance, and the phosphor layer 3 and the powder layer 2 containing W and Mo are sequentially formed thereon. And a method of bonding the support 1 to the powder layer 2 again.

Next, an embodiment of the second radiographic intensifying screen of the present invention will be described.

FIG. 3 is a sectional view showing the structure of an embodiment of the second radiographic intensifying screen of the present invention. On one surface of the support 1 made of a plastic film, a nonwoven fabric or the like, at least one metal selected from yttrium (Y) and zirconium (Zr) or a compound containing the metal and having a thickness of 10 Powder layer 8 in the range of ~ 100μm
Is provided. On the powder layer 8, the first layer
A phosphor layer 3 similar to that of the embodiment is provided.

A protective film 4 made of a plastic film or a plastic coating film is provided on the phosphor layer 3 so that a radiation intensifying screen such as an X-ray intensifying screen 9 used for medical diagnosis can be provided. It is configured. The X-ray intensifying screen 9 according to the second embodiment has a tube voltage of 25 to 32 kV, uses molybdenum as a target, and uses 17.4 keV and 19.5 keV.
An X-ray tube that generates keV characteristic X-rays is used as an X-ray source, and is suitable as an intensifying screen for X-ray imaging of a breast for medical diagnosis. That is, it is suitable as an X-ray intensifying screen for mammography.

As the particles constituting the powder layer 8 described above, at least one kind of metal particles selected from Y and Zr, or compound particles containing at least one kind of metal selected from Y and Zr are used. These can be used as a mixture. As the compound containing Y or Zr, various stable inorganic compounds such as an oxide, a sulfate compound, an oxysulfide, an oxysulfate, a silicate, and a metal salt can be used.

Specific stable compounds containing Y include:
Yttrium oxide (Y ₂ O ₃ ), yttrium sulfate (Y
₂ (SO ₄ ) ₃ ), acid sulfated yttrium (Y ₂ O ₂ S
O ₄ ), yttrium oxysulfide (Y ₂ O ₂ S), yttrium silicate (Y ₂ SiO ₅ , Y ₂ Si ₂ O ₇ ), yttrium tantalate (YTaO ₄ ), yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂₎ ) And the like.
Examples of stable compounds containing Zr include zirconium oxide (ZrO ₂ ) and zirconium silicate (ZrSi
O ₄ ), calcium zirconate (CaZrO ₃ ), strontium zirconate (SrZrO ₃ ), and the like.

The powder layer 8 containing Y or Zr may be formed by using metal particles of Y or Zr as described above, but is particularly formed by using stable inorganic compound particles as described above. Is preferred.

Y and Zr are irradiated from the above-mentioned X-ray tube having a tube voltage of about 25 to 32 kV, 17.4 keV and 19.
It has a large absorption capacity for 5keV characteristic X-rays. Therefore, even if the X-rays irradiated from the support 1 side are scattered by the phosphor layer 3, the protective film 4, etc., the scattered X-rays can be efficiently absorbed by the powder layer 8. As described above, by efficiently absorbing the scattered X-rays in the powder layer 8, the probability that the scattered X-rays re-enter the phosphor layer 3 is reduced, so that the granularity and sharpness can be improved. Become. In principle, it is the same as FIG.

The thickness of the powder layer 8 containing Y or Zr is
The range is 10 to 100 μm. The thickness of the powder layer 8 is 100 μm
If it exceeds, the intensity itself of X-rays that pass through the subject such as the human body and enter the X-ray intensifying screen 9 may be reduced. On the other hand, if the thickness of the powder layer 8 is less than 10 μm, the above-mentioned ability to absorb scattered X-rays is reduced, and the effect of improving graininess and sharpness cannot be sufficiently obtained. The thickness of the powder layer 8 containing Y or Zr is more preferably in the range of 20 to 80 μm.

The powder layer 8 containing Y or Zr can be easily formed in the same manner as the phosphor layer 3. That is,
At least one kind of metal particles (metal powder) selected from Y and Zr or compound particles containing at least one kind of metal selected from Y and Zr (compound powder) are mixed together with an appropriate amount of a binder, and further mixed therewith. An organic solvent is added to prepare a powder coating solution having an appropriate viscosity, and this powder coating solution is applied to the support 1 by a knife coater, a roll coater, or the like, and dried to obtain a desired powder layer 8. According to such a coating method, the powder layer 8 having the above-described thickness can be easily obtained.

As described above, in the X-ray intensifying screen 9 of the second embodiment, since the scattered X-rays can be efficiently absorbed by the powder layer 8 containing Y and Zr, the scattered X-rays are again emitted. The probability of being incident on the phosphor layer 3 is reduced, so that the graininess and sharpness can be improved. The effect of improving the graininess and sharpness can be obtained by a simple structure in which the powder layer 8 containing Y or Zr is provided between the support 1 and the phosphor layer 3. -Ray intensifying screen 9 with improved image quality
Can be easily and inexpensively manufactured.

According to the X-ray intensifying screen 9 of the above-described embodiment, after using characteristic X-rays of 17.4 keV and 19.5 keV, Gd ₂ O ₂ S: Tb or the like having high luminous efficiency is used for the phosphor layer 3. In the case where the rare-earth phosphor is used, the granularity and sharpness can be improved by the powder layer 8 containing Y or Zr. Therefore, by using the X-ray intensifying screen 9 as a mammography radiographic intensifying screen for medical imaging (X-ray imaging) of the breast, the X-ray exposure dose to the subject can be reduced and good diagnostic performance can be obtained. Obtainable.

The mammography X-ray intensifying screen 9 according to the second embodiment can be manufactured in the same manner as in the first embodiment described above, and the constituent materials of each part are the same as those in the first embodiment. Is used.

[0048]

Next, specific examples of the present invention will be described.

Example 1 First, 10 parts by weight of a Gd ₂ O ₂ S: Tb phosphor powder having an average particle diameter of 6.0 μm was added to 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of acetic acid as an organic solvent. The mixture was mixed with ethyl to prepare a phosphor coating solution. The phosphor coating solution after drying was coated on a protective film made of a polyethylene terephthalate film having a thickness of 9 μm.
Apply evenly with a knife coater to 50 mg / cm ² ,
It was dried to form a phosphor layer.

On the other hand, 1 part by weight of tungsten metal particles having an average particle diameter of 3 μm, 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of ethyl acetate as an organic solvent were mixed, and a tungsten particle coating solution was prepared. Was prepared. This tungsten particle coating solution is applied on a support made of a polyethylene terephthalate film having a thickness of 250 μm into which carbon black has been kneaded, and has a coating thickness of 30 μm after drying.
Was uniformly applied with a knife coater and dried to form a tungsten particle layer.

Thereafter, the above-described protective film on which the phosphor layer has been formed and the support on which the tungsten particle layer has been formed are laminated so that the phosphor layer and the tungsten particle layer overlap each other. Paper was made. This X-ray intensifying screen was subjected to characteristic evaluation described later. Example 2 First, 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of ethyl acetate as an organic solvent were added to 10 parts by weight of a Gd ₂ O ₂ S: Tb phosphor powder having an average particle diameter of 6.0 μm. By mixing, a phosphor coating solution was prepared. The phosphor coating solution after drying was coated on a protective film made of a polyethylene terephthalate film having a thickness of 9 μm.
Apply evenly with a knife coater to 50 mg / cm ² ,
It was dried to form a phosphor layer.

On the other hand, 1 part by weight of molybdenum metal particles having an average particle diameter of 3.5 μm was mixed with 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of ethyl acetate as an organic solvent, and the molybdenum particles were coated. A liquid was prepared. The molybdenum particle coating liquid is uniformly applied to a 250 μm-thick polyethylene terephthalate film support, into which carbon black has been kneaded, with a knife coater so that the coating thickness after drying is 30 μm. A layer was formed.

Thereafter, the protective film on which the phosphor layer is formed and the support on which the molybdenum particle layer is formed are laminated so that the phosphor layer and the molybdenum particle layer overlap.
An intended X-ray intensifying screen was produced. This X-ray intensifying screen was subjected to characteristic evaluation described later.

Comparative Example 1 A particle layer (powder layer) of W or Mo between a support and a phosphor layer
An X-ray intensifying screen was prepared in the same manner as in Example 1 except that no X was formed, and subjected to the characteristic evaluation described later.

The sensitivity, sharpness, and granularity of each of the X-ray intensifying screens of Examples 1 and 2 and Comparative Example 1 were measured using an ortho-type film (Super HR-S, manufactured by Konica Corp.). ,evaluated. Table 1 shows the results. In addition,
The photographic performance of the intensifying screen was photographic sensitivity, sharpness, and graininess when photographed with a tube voltage of 80 kV X-ray through a 100 mm thick water phantom.
The relative value and the sharpness were determined by calculating the MTF value at the spatial frequency of 2 lines / mm. The relative value when the MTF value of the intensifying screen of Comparative Example 1 at the spatial frequency was set to 100, and the graininess was defined by the photographic density. 1.0, R at spatial frequency 0.1 to 0.5 lines / mm
MS value.

[0056]

[Table 1] As is clear from Table 1, the X-ray intensifying screens according to Examples 1 and 2 do not lower the sensitivity as compared with the intensifying screens having no W or Mo particle layer (powder layer). It can be seen that sharpness and granularity were significantly improved.

Example 3 First, 10 parts by weight of a Gd ₂ O ₂ S: Tb phosphor powder having an average particle diameter of 3.0 μm was added to 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of acetic acid as an organic solvent. The mixture was mixed with ethyl to prepare a phosphor coating solution. The phosphor coating solution after drying was coated on a protective film made of a polyethylene terephthalate film having a thickness of 9 μm.
Apply evenly with a knife coater to 35 mg / cm ² ,
It was dried to form a phosphor layer.

On the other hand, 1 part by weight of yttrium oxide particles having an average particle size of 3 μm, 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of ethyl acetate as an organic solvent were mixed, and the yttrium oxide particles were coated. A liquid was prepared. This yttrium oxide particle coating liquid is uniformly coated on a 250 μm-thick polyethylene terephthalate film support, into which carbon black has been kneaded, with a knife coater so that the coating thickness after drying is 30 μm, and then dried and oxidized. An yttrium particle layer was formed. After this,
The protective film on which the above-described phosphor layer is formed and the support on which the yttrium oxide particle layer is formed are laminated so that the phosphor layer and the yttrium oxide particle layer are overlapped to produce an intended X-ray intensifying screen. did. This X-ray intensifying screen was subjected to characteristic evaluation described later.

Example 4 First, 10 parts by weight of a Gd ₂ O ₂ S: Tb phosphor powder having an average particle diameter of 3.0 μm was added to 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of acetic acid as an organic solvent. The mixture was mixed with ethyl to prepare a phosphor coating solution. The phosphor coating solution after drying was coated on a protective film made of a polyethylene terephthalate film having a thickness of 9 μm.
Apply evenly with a knife coater to 35 mg / cm ² ,
It was dried to form a phosphor layer.

On the other hand, 1 part by weight of zirconium oxide particles having an average particle diameter of 3.5 μm, 1 part by weight of a vinyl chloride-vinyl acetate copolymer as a binder and an appropriate amount of ethyl acetate as an organic solvent were mixed, and the zirconium oxide particles were coated. A liquid was prepared. The coating solution of zirconium oxide particles is uniformly coated on a support made of a 250 μm thick polyethylene terephthalate film into which carbon black has been kneaded, using a knife coater so that the coating thickness after drying is 30 μm, and then dried and oxidized. A zirconium particle layer was formed. After this,
The protective film on which the above-described phosphor layer is formed and the support on which the zirconium oxide particle layer is formed are laminated so that the phosphor layer and the zirconium oxide particle layer are overlapped to produce an intended X-ray intensifying screen. did. This X-ray intensifying screen was subjected to characteristic evaluation described later.

Comparative Example 2 An X-ray intensifying screen was prepared in the same manner as in Example 3, except that a particle layer (powder layer) of yttrium oxide or zirconium oxide was not formed between the support and the phosphor layer. , And were subjected to the characteristic evaluation described later.

For each of the X-ray intensifying screens of Examples 3 and 4 and Comparative Example 2, the sensitivity, sharpness, and granularity were measured and evaluated using an ortho-type film (MinR, manufactured by Kodak Company). . Table 2 shows the results. The photographic performance of the intensifying screen is the photographic sensitivity, sharpness, and granularity when photographed with a tube voltage of 28 kV through X-ray through a molybdenum metal plate having a thickness of 30 μm. 100 paper
The relative value and the sharpness were determined by measuring the MTF value at a spatial frequency of 4 lines / mm, and the relative value when the MTF value of the intensifying screen of Comparative Example 2 at the spatial frequency was set to 100; 1.0, R at spatial frequency 0.1 to 0.5 lines / mm
MS value.

[0063]

[Table 2] As is evident from Table 2, the X-ray intensifying screens of Examples 3 and 4 were all compared with the intensifying screen of Comparative Example 2 having no particle layer (powder layer) of yttrium oxide or zirconium oxide. It can be seen that sharpness and graininess are greatly improved without lowering the sensitivity.

[0064]

As described above, according to the radiographic intensifying screen of the present invention, the sharpness and the graininess can be greatly improved while suppressing the decrease in sensitivity. Therefore, when the radiographic intensifying screen of the present invention is used for X-ray imaging for medical diagnosis, for example, good diagnostic performance can be obtained while reducing the radiation exposure of the subject.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an embodiment of a radiographic intensifying screen of the present invention.

FIG. 2 is a diagram for explaining the effect of improving the granularity and sharpness of the radiation intensifying screen of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of an embodiment of another radiographic intensifying screen according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Support 2 ... Powder layer containing W and Mo 3 ... Phosphor layer 4 ... Protective film 5 ... X-ray intensifying screen for general medical photography 8 ... Powder layer containing Y and Zr 9 X-ray intensifying screen for mammography

Claims (6)

[Claims] 1. A radiographic intensifying screen comprising a support, a phosphor layer formed on the support, and a protective film provided on the phosphor layer, wherein the support and the phosphor layer And at least one metal selected from tungsten and molybdenum, or a compound containing the metal, and has a thickness of 10 to 100 μm.
A radiation intensifying screen, wherein a powder layer in the range of m is provided. 2. The radiation intensifying screen according to claim 1, wherein the powder layer is made of the metal particles. 3. The radiographic intensifying screen according to claim 1, wherein the radiographic intensifying screen is an X-ray intensifying screen for general medical imaging. 4. A radiographic intensifying screen comprising a support, a phosphor layer formed on the support, and a protective film provided on the phosphor layer, wherein the support and the phosphor layer At least one metal selected from yttrium and zirconium, or a compound containing the metal, and having a thickness of 10 to 100.
A radiographic intensifying screen having a powder layer in the range of μm. 5. The radiation intensifying screen according to claim 4, wherein the powder layer is made of particles of the metal compound. 6. The radiation intensifying screen according to claim 4, wherein the radiation intensifying screen is an X-ray intensifying screen for mammography.