JP2884352B2 - Radiation image conversion panel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly, to radiation with reduced dead space from the panel edge to the stimulable phosphor layer. The present invention relates to an image conversion panel.

[Background of the Invention] Radiation images such as X-ray images are widely used for disease diagnosis and the like.

In order to obtain this X-ray image, an X-ray image conversion method for directly extracting an image from a phosphor layer instead of a silver halide photosensitive material has been devised.

This method uses radiation transmitted through the subject (generally X-rays)
Is absorbed by the phosphor, and thereafter, the phosphor is excited by, for example, light or heat energy, thereby radiating the radiation energy accumulated by the phosphor as the above-mentioned absorption as fluorescence. It is a method to become.

Specifically, for example, US Pat. No. 3,859,527 and JP-A-55-12144 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulating excitation light.

This method uses a radiation image conversion panel (hereinafter abbreviated as a conversion panel) in which a stimulable phosphor layer (hereinafter abbreviated as a stimulable layer) is formed on a support. A radiation image corresponding to the radiation transmittance of each part of the subject is accumulated by applying radiation transmitted through the subject to form a latent image, and thereafter, the stimulable layer is scanned with stimulating excitation light to accumulate the latent image. The radiation energy is emitted and converted into light, and an image is obtained by an optical signal based on the intensity of the light.

This final image may be reproduced as a hard copy or reproduced on a CRT.

The conversion panel used in this radiation image conversion method emits the stored energy by scanning the stimulating excitation light after accumulating the radiation image information, so that the radiation image can be accumulated again after the scanning, and can be used repeatedly. It is possible.

Therefore, it is desirable that the conversion panel has a performance that can withstand long-time use or repeated use many times without deteriorating the image quality of the obtained radiation image. For this purpose, the photostimulable layer in the conversion panel needs to be sufficiently protected from external physical or chemical stimuli.

In the conventional conversion panel, in order to solve the above-mentioned problem, a method of providing a protective layer for covering the stimulable layer surface on the support of the conversion panel has been adopted.

This protective layer is formed, for example, by directly applying a coating liquid for a protective layer on a stimulable layer, or stimulating a previously formed protective layer as described in JP-A-59-42500. It is formed by a method of bonding on a layer.

Generally, a thin protective layer made of an organic polymer is used. The thin protective layer has the advantage that the sharpness of the conversion panel is hardly reduced.

However, thin protective layers of commonly used organic polymers are somewhat permeable to moisture and / or moisture, and the stimulating layer absorbs moisture, resulting in reduced radiation sensitivity or stimulating excitation of the conversion panel. The stored energy is largely attenuated until receiving the light irradiation, which causes variation and / or deterioration in the image quality of the obtained radiation image.

For example, a polyethylene terephthalate film having a thickness of 10 μm (hereinafter simply referred to as “PET”) has a moisture permeability of about 60
(G / m ² · 24 hr), and permeate as much as 60 g of water per unit area per day. For OPP (stretched polypropylene) with a film thickness of 10 μm, the value is about 15 (g / m ² · 24 hr). The moisture permeability of the protective layer is preferably 1 (g / m ² · 24 hr) or less. To achieve this, about 600 μm or more for PET and about 1 μm for OPP
A thickness of 50 μm or more is required, leading to a decrease in sharpness.

In order to solve this, there is also known a means for providing a gas layer or a vacuum layer having a lower refractive index than the protective layer between the protective layer and the photostimulable layer to prevent the sharpness from lowering. In this case, usually the first
As shown in the figure, a method is employed in which spacers 4 are provided on the side edges of the conversion panel to maintain a constant thickness. If this is shown in the plan view of FIG. 5, 4a, 4b, 4c and 4d correspond to this.

In the conversion panel having such a structure, the photostimulable layer cannot be provided up to the end of the support and must be 1 to 2 c from the end.
m creates dead space. This is not only economically unfavorable, but also has a major drawback in that, in particular, when used for mammography (breast diagnosis), there are places where imaging cannot be performed.

[Object of the invention]

Therefore, an object of the present invention is to provide a radiation image conversion panel which can be used for mammography by shortening the distance from the panel edge to the photostimulable layer (capturable area).

[Configuration of the invention]

The object of the present invention is to provide a photostimulable phosphor having a stimulable phosphor layer and a protective layer on a support, surrounding the stimulable phosphor layer between the support and the protective layer. In a radiation image conversion panel provided with a spacer having a thickness of not less than the thickness, at least one side surrounding the stimulable phosphor layer has a structure in which a thin plate is provided outside the panel without using the spacer. Achieved by radiographic image conversion panel.

 Hereinafter, the present invention will be described in detail.

2, 3 and 4 are cross-sectional views of the conversion panel of the present invention, wherein 1 is a support, 2 is a photostimulable layer, 3 is a protective layer,
Is a spacer, and 5 is a thin plate of the present invention.

 Hereinafter, each component requirement will be described in more detail.

As the protective layer of the present invention, a layer having good light transmission and capable of being formed in a sheet shape can be used. For example, sheet glass such as quartz, borosilicate glass, chemically strengthened glass, PET, O
Organic polymers such as PP and polyvinyl chloride are exemplified.

The protective layer of the present invention may be a single layer, a multilayer, or may be composed of two or more types of layers having different materials. For example, a film in which two or more organic polymer films are combined can be used. Examples of a method for producing such a composite polymer film include methods such as dry lamination, extrusion lamination, and coextrusion coating lamination. Combinations of two or more protective layers are not limited to organic polymers, but include sheet glass or sheet glass and an organic polymer layer. For example, as a method of combining a sheet glass and a polymer layer, there is a method of directly applying a coating liquid for a protective layer on the sheet glass, or a method of bonding a separately formed polymer protective layer on the sheet glass. The two or more protective layers may be in close contact with each other or may be separated from each other.

The thickness of the protective layer of the present invention is practically 30 μm to 4 mm. In order to obtain good moisture resistance and impact resistance, the thickness of the protective layer is preferably 100 μm or more. In particular, when a protective layer of 200 μm or more is provided, a conversion panel having excellent durability and durability can be obtained. More preferred.

Further, when a sheet glass is used as the protective layer, it is extremely excellent in moisture resistance and is particularly preferable.

The protective layer desirably exhibits a high transmittance in a wide wavelength range in order to transmit the stimulating excitation light and the stimulating light efficiently, and the transmittance is preferably 80% or more. For example, quartz glass,
Borosilicate glass and the like can be mentioned. 330 nm for borosilicate glass
It shows a transmittance of 80% or more in the wavelength range of 2.62.6 μm, and quartz glass shows a high transmittance even at a shorter wavelength.

The stimulable phosphor used in the present invention may be stimulated (stimulated excitation) such as optically, thermally, mechanically, chemically or electrically after irradiation of the first light or high-energy radiation.
By the phosphor is a phosphor that shows stimulated emission corresponding to the irradiation amount of the first light or high-energy radiation, but is preferably a phosphor that shows stimulated emission by a stimulated excitation light of 500 nm or more from a practical viewpoint. . BaSO The stimulable phosphor, as described, for example JP-A-48-80487 _4: AX, JP 48-8
SrSO described in JP 0489 _4: AX, the JP 53-39277 Li ₂ B
₄ O _7: Cu, Ag, _{etc., Li 2 O · (B 2} O 2) of JP 54-47883 x: Cu and _{Li 2 O · (B 2 O} 2) x: Cu, Ag , etc., U.S. Patent SrS of 3,859,527:
Ce, Sm, SrS: Eu, Sm, La 2 O 2 S: Eu, Sm and (Zn, Cd) S: phosphor represented by Mn, is described in JP-A-55-12142 ZnS: C
u, Pb phosphor general formula BaO · xAl ₂ O _3: barium aluminate phosphor represented by Eu, the general formula M ^II O · xSiO _2: alkaline earth metal silicate phosphor represented by A, Japanese Patent Application Laid-Open No. 55-12143 discloses an alkaline earth fluoride halide represented by the general formula (Ba ₁ -x _- yMgxCay) FX: eEu ²⁺ described in JP-A-55-12143.
Formula LnOX described in JP: phosphor represented by xA, the general formulas described in ^{_{JP-A-55-12145 (Ba 1- xM III x)}} FX: yA
A phosphor represented by the general formula BaFX: xCe, yA described in JP-A-55-84389, a phosphor represented by the general formula M ^II FXxA described in JP-A-55-160078. : a rare earth element-activated divalent metal fluorohalide phosphor represented by: yLn, general formula ZnS: A, C
phosphors represented by dS: A, (Zn, Cd) S: A, S: A, ZnS: A, X and CdS: A, X, and the following general formula xM described in JP-A-59-38278.
_{3 (PO 4) 2 · NX} 2: yA and M ₃ (PO _{4) 2:} phosphor represented by yA, the following general formula nReX ₃ · mAX _'2: xEu and _{nReX 3 · mAX' 2: xEu} , y
Phosphor represented by Sm, and the following general formula ^{M I X · aM II X '} 2
BM ^III X ″ ₃ : an alkali halide phosphor represented by cA, etc. In particular, the alkali halide phosphor is deposited,
This is preferable because a stimulable layer can be easily formed by a method such as sputtering.

However, the stimulable phosphor used in the conversion panel according to the present invention is not limited to the above-described phosphor, and a phosphor that exhibits stimulable emission when irradiated with stimulating excitation light after being irradiated with radiation. Any phosphor may be used.

The conversion panel of the present invention may be a stimulable layer group comprising one or more stimulable layers containing at least one of the stimulable phosphors. Further, the stimulable phosphor contained in each stimulable layer may be the same or different.

The stimulable layer of the present invention may be formed by either a coating method or a vapor deposition method, but the vapor deposition method is advantageous from the viewpoint of sharpness.

As the support of the conversion panel of the present invention, various polymer materials, glass, ceramics, metals and the like are used.

Examples of the polymer material include films of cellulose acetate film, polyester film, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate and the like. Examples of the metal include a metal sheet or metal plate of aluminum, iron, copper, chromium, or the like, or a metal sheet or metal plate having a coating layer of the metal oxide. Examples of the glass include chemically strengthened glass and crystallized glass. Examples of the ceramic include a sintered plate of alumina or zirconia.

The layer thickness of the support varies depending on the material of the support to be used and the like, but is generally 80 to 2000 μm, and more preferably 80 to 1000 μm from the viewpoint of handling.

In the conversion panel of the present invention, the protective layer can also serve as a support. In that case, the support referred to in the present invention may not substantially have the ability to support the photostimulable layer.

As the spacer used for the conversion panel of the present invention, the same material as the material used for the protective layer or the support can be used. Its thickness is practically 1 to 30 mm, preferably 2 to 10 mm.

It is also preferable that the thin plate provided on the outside of the panel instead of the spacer is the same as the material used for the support.
Its thickness is practically 0.1-5 mm, preferably 0.5
~ 1.5mm.

As an embodiment of the present invention, at least one side of the four-sided spacers (4a, 4b, 4c, 4d in FIG. 5) of the conventional conversion panel may be removed, and a thin plate may be provided from the outside of the panel (see FIG. 6), and two, three, or all four sides may be removed to provide a thin plate. However, considering the easiness of processing, cost, ease of use for the user, and the like, the configuration shown in FIG. 7 in which two opposing sides are replaced with a thin plate attached is desirable.

As a method of providing a thin plate, adhesion or fusion may be used. As the adhesive to be used, an epoxy resin, a silicon resin, or the like is preferable. Further, as shown in FIG. 4, a type in which both the support and the protective layer are bonded on two surfaces is more preferable.

The conversion panel of the present invention is used in a radiation image conversion method schematically shown in FIG.

That is, in FIG. 8, 11 is a radiation generator, 12
Is a subject, 13 is a conversion panel according to the present invention, 14 is a stimulating excitation light source, 15 is a photoelectric conversion device for detecting stimulating fluorescence emitted from the conversion panel, and 16 is a signal reproduced at 15 as an image. Device for displaying, 17 is a device for displaying reproduced images,
Reference numeral 18 denotes a filter that separates stimulable excitation light from stimulable fluorescence and transmits only stimulable fluorescence. Note that after 15 the optical information from 13 can be reproduced in any form as an image, and is not limited to the above.

As shown in FIG. 8, the radiation from the radiation generator 11 enters the conversion panel 13 through the subject 12. The incident radiation is absorbed by the photostimulable layer of the panel 13 and its energy is accumulated, so that an accumulated radiation transmission image is formed.

Next, the accumulated image is excited by stimulating light from the stimulating light source 14 and emitted as stimulating light.

Since the intensity of the emitted photostimulated luminescence is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by a photoelectric conversion device 15 such as a photomultiplier tube, and reproduced as an image by an image reproduction device 16, and the image is reproduced. By displaying the image on the display device 17, a radiographic image of the subject can be observed.

〔Example〕

 Next, the present invention will be described with reference to examples.

COMPARATIVE EXAMPLE Alkali halide phosphor (RbBr; 0.0006Tl) was placed in a central portion of a crystallized glass support having a size of 20 cm × 30 cm and a thickness of 1 mm, and 300 μm of an alkali halide phosphor.
m was deposited to obtain a panel base A. Next, a 5 mm wide, 1 mm thick crystallized glass spacer (two 19 cm long and two 28 cm long) and 20 mm
A 1 mm thick soda glass protective layer of cm × 30 cm was provided on the panel base A using an epoxy adhesive (AV-138 / HV998, manufactured by Ciba Geigy) to obtain a conversion panel P. (FIG. 1) Example 1 Alkali halide phosphor (RbBr; 0.0006Tl) was 300 μm in the center of a crystallized glass support of 20 cm × 30 cm and 1 mm thick.
m was deposited to obtain a panel base B. Next, crystallized glass spacers of 5 mm width and 1 mm thickness (one 19 cm long, two 29 cm long), 20 cm
Soda glass protective layer of 1mm thickness at × 30cm and 1m at 3mm × 20cm
Epoxy adhesive for thin plate of soda glass with m thickness
Was applied to the panel base B to obtain a conversion panel Q. (FIG. 2) Example 2 A conversion panel R was obtained in the same manner as in Example 1 except that lid-like soda glass having a thickness of 1 mm was used as a thin plate.
(FIG. 4) Example 3 Alkali halide phosphor (RbBr; 0.0006Tl) 300 μm in the center of a crystallized glass support of 20 cm × 30 cm and 1 mm thick
m was deposited to obtain a panel base C. Next, a 5mm wide, 1mm thick crystallized glass spacer (2 x 30cm long), a 20cm x 30cm, 1mm thick soda glass protective layer and a 3mm x 20cm, 1mm thick soda glass thin plate are used as epoxy adhesive ( The conversion panel S was provided on the panel base C using the above-described method. (FIG. 3) The conversion panel Q of the present invention manufactured as described above,
The humidity resistance of R, S, and the comparative conversion panel P and the distance from the edge of the panel to the photographable area were examined. The results are shown in Table 1.

The moisture resistance was expressed as a ratio of sensitivity to radiation before and after storage at 30 ° C. and 80% relative humidity for 30 days.

[Effects of the Invention] The present invention has a stimulable phosphor layer and a protective layer on a support, and surrounds the periphery of the stimulable phosphor layer between the support and the protective layer to form a stimulable phosphor. In a radiation image conversion panel provided with a spacer having a thickness equal to or greater than the thickness of the body, at least one side surrounding the stimulable phosphor layer does not use the spacer, and a thin plate is attached outside the panel. As a result, the distance from the edge of the panel to the photostimulable layer photographable area can be shortened to provide an advantageous conversion panel for mammography.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional conversion panel, FIG. 2, FIG. 3 and FIG. 4 are sectional views of the conversion panel of the present invention, FIG. 5 is FIG. 1, FIG. 6 is FIG. FIG. 7 is a plan view of the conversion panel having the configuration shown in FIG. FIG. 8 is an explanatory diagram of a radiation image conversion method using a conversion panel. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Stimulation layer 3 ... Protective layer, 4 ... Spacer 5 ... Thin plate

Claims (1)

(57) [Claims] 1. A stimulable phosphor layer having a stimulable phosphor layer and a protective layer on a support, surrounding the stimulable phosphor layer between the support and the protective layer, In a radiation image conversion panel provided with a spacer having a thickness of at least one or more, at least one side surrounding the stimulable phosphor layer has a structure in which a thin plate is provided outside the panel without using the spacer. Characteristic radiation image conversion panel.