JP2942960B2 - Radiation image conversion panel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a radiation image conversion panel having a stimulable phosphor layer, and more particularly to a high-sensitivity radiation image conversion panel.

[Conventional technology]

X-ray imaging directly from the phosphor layer instead of the conventional silver halide light-sensitive material for obtaining X-ray images used for disease diagnosis
A line image conversion method has been devised.

This method uses a stimulable phosphor layer (hereinafter abbreviated as a phosphor layer).
A radiation image conversion panel (hereinafter, abbreviated as a conversion panel) having the following is used. Radiation transmitted through a subject is applied to the phosphor layer of the conversion panel to accumulate radiation energy corresponding to the radiation transmittance of each part of the subject. A latent image is formed, and then the phosphor layer is scanned with stimulating light to emit the radiation energy stored in each part and convert it into light, and an image is formed by a light signal based on the intensity of the light. What you get.

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 phosphor layer of 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 problem, a method of providing a protective layer covering the phosphor layer surface on the support of the conversion panel, sealing the periphery of the conversion panel, and protecting the phosphor layer is a method. I have been.

In particular, in order to improve the moisture-proof property, a protective layer having a greater moisture-proof effect than the conventional protective layer is used, and a spacer structure is attached and sandwiched between the support and the protective layer by surrounding the phosphor layer with the phosphor layer. A conversion panel (Japanese Patent Application No. 63-141522) has been proposed.

In the shell structure, the phosphor layer may be bonded to the protective layer body, but it is preferable that the phosphor layer and the protective layer body are not in contact with each other, and a low refractive index layer is provided between the phosphor layer and the photostimulated excitation, There are proposals for improving the efficiency of stimulable light reading and sharpness.

On the other hand, the photoelectric conversion reading of the radiation image is performed by irradiating the phosphor layer with image radiation from the protective layer side and performing the photoelectric conversion reading again from the protective layer side. The radiation image of the subject is incident on the phosphor layer from the support side and copied onto the phosphor layer, without removing the attached conversion panel, and then directly stimulating excitation from the protective layer body side, which is configured with sufficient optical consideration, A continuous and one-way incident-read-out type radiation image reading apparatus for reading out a photostimulated image has been developed. According to this method, the operation time can be shortened, and the apparatus can be integrated and miniaturized.

This method is characterized in that image radiation is incident from the support side, so that the support absorbs radiation,
It is necessary that the reflection is low, that is, the radiation transmittance is high.

Further, since the support is the basis of the panel structure, mechanical strength such as surface hardness, toughness, and rigidity of the support is required in view of panel durability and operability.

Also, from the viewpoint of production technology, when a phosphor is vapor-deposited by vapor deposition or the like, when a crystal having a specific structure is generated in order to improve the sharpness of the generated phosphor layer, or when the phosphor on the panel is formed. When the body is heated, dried and sealed, the support is heated, so that it is necessary to have heat resistance enough to withstand the heating.

Materials currently used as supports include polymer resins, ceramics, glass, metals and the like.

A polymer resin is generally a preferable material having good workability and high radiation transmittance. On the other hand, mechanical strength and heat resistance may be difficult.

A ceramic plate, a glass plate, or a metal plate formed by sintering has sufficient heat resistance, but has poor radiation transmittance and lowers sensitivity. When thinner and more transparent, the required mechanical strength is lost.

As described above, it is difficult to form a support having good radiation permeability, mechanical strength, and heat resistance by simply using a conventional material.

[Object of the invention]

An object of the present invention is to provide a radiation image conversion panel having high sensitivity and high durability.

[Structure and operation and effect of the invention]

The object of the present invention is to provide a radiation image conversion panel in which a stimulable phosphor layer is formed on a support, wherein the support contains a material having a lower radiation absorptivity than the support. This is achieved by a radiation image conversion panel.

The so-called high radiation transmitting body according to the present invention refers to fine beads, hollow beads or core-shell particles containing a light coarse material as a core, short fibers, air bubbles, and the like, which have a low radiation absorptivity. A laminated sheet having an embossed surface on one side or both sides, and at least one of these is sandwiched by a reinforcing plate, a moisture-proof plate or the like, if necessary, and formed into a sheet to support the composite sheet according to the present invention. It is said.

It is preferable that the radiation absorptivity in the thickness direction of the composite sheet is uniformly adjusted everywhere on the composite sheet surface, more specifically, for each pixel of the radiation image.

In the present invention, for example, 50 vol
%, The X-ray absorptance is reduced to about 1/2, the incident amount to the phosphor layer is increased by that amount, and the stimulated emission is increased by at least 20%, resulting in an increase in sensitivity as a conversion panel. be able to.

Similarly, a support containing air bubbles as a high-permeability body has a vibration-proofing effect. This is because the conversion panel faces the subject (patient) across the front panel in the radiation image capturing / reading device, and is affected by vibrations such as when the subject moves or touches during capturing and image reading. The use of such a support that suppresses vibration is also effective as a measure against noise when reading a radiation image.

In the case where the phosphor is vapor-phase deposited, a fine-grain phosphor is grown on the surface of the composite sheet by adjusting the vapor-phase deposition conditions by using a fine-grained surface formed by beads or the like, A conversion panel with high sensitivity and high sharpness can be obtained.

Further, when the support is made of a porous material, crystals may be precipitated by impregnating the support with a saturated solution of the substance to be vapor-deposited, and the crystals may be grown using the nuclei as a nucleus. it can.

When the phosphor layer is provided by a coating method, an adhesive layer may be provided in advance.

Next, an embodiment of the composite sheet support according to the present invention will be described with reference to the drawings.

In FIG. 1 (a), reference numeral 1 denotes air bubbles as a light coarse material;
Is a support layer made of a commonly used material having a strength-retaining and moisture-proof effect, and 4 is a moisture-blocking layer. In FIG. 1B, reference numeral 1 denotes beads made of a light coarse material, and 4 denotes a moisture barrier layer. When a phosphor is vapor-deposited thereon under specific conditions, fine granular crystals having a honeycomb-like striae can be aggregated and formed.

Reference numeral 1 in FIG. 3C denotes hollow light coarse material beads. Reference numeral 1 in the figure (d) denotes a short fibrous light coarse material having a dense nonwoven fabric shape. 2 (e) is a thin support layer having embosses on both sides, which are laminated and bonded or sintered to form a layer. When the components of the support are moisture permeable, and when the pores in the support are not independent but continuous and have air permeability on the front and back sides of the support, the moisture barrier layer 4 is provided in the thickness direction of the support and in the peripheral portion. Those provided are preferred. The form is shown in FIGS. 2 (a), (b) and (c).

Note that the same reference numerals, which are not described, have the same meanings as the same reference numerals.

FIG. 3 illustrates a shell-type conversion panel having a support made of the composite sheet.

In the figure, 10 is a composite sheet support, 11 is a protective layer, 12 is a phosphor layer, 13 is a spacer, and 14 is a low refractive index layer.

The support 10, the protective layer 11 and the spacer 13 are adhered by an adhesive, and the phosphor layer 12 is sealed in a shell after drying.

In the conversion panel of the present invention, the image radiation transmitted through the subject from the support 10 enters the phosphor layer 12, and the stimulating excitation and reading of the stimulating image are performed in one direction from the protective layer 11 side. .

As the protective layer used in the present invention, a protective layer having good light projection and capable of being formed into a sheet is used. In order to transmit the stimulated excitation light and the stimulated emission efficiently, the protective layer preferably has a high light transmittance in a wide wavelength range, and the light transmittance is preferably 80% or more.

Examples of such a material include plate glass such as quartz, borosilicate glass, and chemically-strength glass, and organic polymer compounds such as PET, drawn polypropylene, and polyvinyl chloride. Borosilicate glass has a wavelength range of 330 nm to 2.6 μm
It shows a light transmittance of 80% or more, and quartz glass shows a high light transmittance even at shorter wavelengths.

Further, it is preferable to provide an anti-reflection layer such as MgF _{2 on} the surface of the protective layer body, because it has an effect of efficiently transmitting the stimulating light and the stimulating light and also has the effect of reducing the decrease in sharpness.

The thickness of the protective layer is 50 μm to 5 mm, and preferably 100 μm to 3 mm in order to obtain good moisture proofness.

After the phosphor layer is formed on the support, a spacer is provided between the support and the protective layer so as to surround the phosphor layer. As such a spacer, the phosphor layer is shielded from the external atmosphere. There is no particular limitation as long as it can be held in a state, and glass, ceramics, metal, plastic, and the like can be used.

Further, it is preferable that the spacer has a moisture proof of 30 g / m ² · 24 hr or less. If the moisture permeability is too large, the stimulable phosphor deteriorates due to moisture entering from the outside, which is not preferable.

The moisture permeability was measured based on the cup method (JIS, Z0208).

The thickness of the spacer is preferably equal to or greater than the thickness of the phosphor layer, and the width of the spacer is mainly determined by the moisture-proof property (the moisture permeability) of the contact portion between the spacer, the support and the protective layer. ) And is preferably 1 to 30 mm. If the width of the spacer is too small, it is not preferable from the viewpoints of the stability, strength, and moisture resistance of the spacer. If the size is too large, the size of the conversion panel becomes unnecessarily large, which is not preferable.

In addition, it is preferable that the moisture permeability of the contact portion between the spacer, the support and the protective layer is 30 g / m ² · 24 hr or less.

The spacer is required to be in close contact with the support and the protective layer in order to impart moisture-proof properties to the conversion panel and to keep the thickness of the low refractive index layer constant.

Here, for example, an adhesive or the like is used for bonding the spacer to the composite sheet support and the protective layer, and the adhesive is preferably one having moisture resistance. Specifically, epoxy resin, phenolic resin, cyanoacrylate resin, vinyl acetate resin, vinyl chloride resin, urethane resin, acrylic resin, ethylene vinyl acetate resin,
Organic polymer-based adhesives such as olefin-based resins, chloroprene-based rubbers, and nitrile-based rubbers; silicone-based adhesives; and inorganic-based adhesives mainly composed of alumina, silica, and the like. Among these, epoxy resins and silicone resins used for encapsulating semiconductors and electronic components are preferable because of their excellent moisture resistance, and epoxy adhesives are particularly suitable because they have low moisture permeability.

In order to improve the adhesion of the spacer and the support or the contact portion between the spacer and the protective layer, an undercoat layer may be provided on the contact surface of the spacer, the support and the protective layer with the other layer, or a rough layer may be provided. Surface treatment can also be performed.

The low-refractive-index layer according to the conversion panel of the present invention is preferably a gas layer or a vacuum layer because it has a high effect of preventing sharpness from decreasing.

The thickness of the low refractive index layer is practically 0.05 μm to 3 mm.

The stimulable phosphor used in the present invention, after being exposed to the first light or high-energy radiation,
Stimulation such as thermal, mechanical, chemical or electrical (stimulated excitation)
Is a phosphor that exhibits stimulated emission corresponding to the amount of the first light or high-energy radiation. However, from a practical viewpoint, it is preferably a phosphor that exhibits stimulated emission by excitation light of 500 nm or more. Is like that stimulable phosphor, for example BaSO are described in JP 48-80487 _4: AX, are described in JP-A-48-80489 SrSO _4: AX, JP 53
Of No. _{-39277 Li 2 B 4 O 7:} Cu, Ag , etc., in JP 54-47883 Li _{2
O · (B 2 O 2)} x: Cu and _{Li 2 O · (B 2 O} 2) x: Cu, Ag , etc., in U.S. Pat. No. 3,859,527 SrS: Ce, Sm, SrS : Eu, Sm, La 2 O 2 : Eu, Sm and (Zn, Cd) S: Mn.

Further, ZnS: Cu, Pb described in JP-A-55-12142
Phosphor, the general formula BaO · xAl ₂ O _3: barium aluminate phosphor represented by Eu, and the general formula M ^II O · xSiO _2: alkaline earth metal silicate phosphor represented by A are exemplified. Further, an alkaline earth fluoride halide phosphor represented by the general formula (Ba ₁ -x-yMgxCay) FX: eEu ²⁺ described in JP-A-55-12143 is disclosed in JP-A-55-12144. the listed formulas LnOX: phosphor represented by xA, the general formulas described in ^{_{JP-a-55-12145 (Ba 1 -xM II x)}} FX: phosphor represented by yA, JP 55 -84389, a phosphor represented by the general formula BaFX: xCe, yA, and a rare earth element activated 2 represented by a general formula M ^II FX.xA: yLn described in JP-A-55-160078. Valent metal fluorohalide phosphor, general formula ZnS: A, CdS: A, (Zn, Cd) S: A, S: A, ZnS: A,
X and CdS: a phosphor represented by A, X, any one of the following general formulas xM ₃ (PO ₄ ) ₂ .NX ₂ : yAM ₃ (PO ₄ ) ₂ described in JP-A-59-38278. phosphor represented by yA, either of the following general formula nReX that are described in _{JP-a-59-155487 3 · mAX '2: xEu} nReX 3 · mAX' 2: xEu, phosphor represented by YSM, following general are described in JP 61-72087 formula ^{M I X · aM II X '} 2 · bM III X "3:. alkali halide phosphor, etc. represented by cA can be mentioned in particular alkali halide phosphors It is preferable because the phosphor layer can be easily formed by a method such as vapor deposition or sputtering.

However, the stimulable phosphor used in the present invention is:
The phosphor is not limited to the above-described phosphor, and any phosphor may be used as long as it emits stimulating light when irradiated with stimulating excitation light after irradiation with radiation.

In the present invention, the stimulable phosphor layer is formed on the support by a coating method or a vapor deposition method.

Such a phosphor layer may be a phosphor layer group composed of one or more phosphor layers containing at least one kind of the stimulable phosphor. Further, the stimulable phosphor contained in each phosphor layer may be the same or different.

The thickness of the phosphor layer of the conversion panel is different depending on the sensitivity of the intended conversion panel to radiation, the type of stimulable phosphor, etc., but when no binder is contained, 10 μm to 1000 μm.
Range, preferably selected from the range of 20μm ~ 800μm, in the case of containing a binder in the range of 20μm ~ 1000μm,
Preferably it is selected from the range of 50 μm to 500 μm.

〔Example〕

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

Example 1 Commercially available porous ceramics (manufactured by Bridgestone, Kanebo Co., Ltd .: alumina (Al ₂ O ₃ ) milk mud poured into a urethane foam sheet or mixed with polymer beads and sintered as a plate) The cover glass was bonded to obtain a porous composite sheet support shown in FIG.
(Urethane foam or polymer beads are completely burned during the sintering process.) Comparative Example (1) A simple alumina plate was used as a comparative support. Assuming that the sensitivity obtained by using the comparative support is 100, the composite sheet support of Example 1 has a relative sensitivity of 130.

Here, the sensitivity was measured by the following method. RbBr as a stimulable phosphor on various supports: 0.0001Tl (numbers are RbBr
(Molar ratio), and after drying by heating, a panel as shown in FIG. 3 was prepared. Place this panel at a distance of 100 cm from the focal point of the X-ray tube, a tube voltage of 80 kVp, and a tube current of 10 mA.
X-rays are irradiated for 0.1 seconds, and then irradiated with semiconductor laser light (7
(80 nm, 10 mW), and the stimulated emission produced there was measured with a photodetector, and the intensity was used as the sensitivity.

Example 2 Lithium oxide (Li ₂ O) fine particles were pressure-formed into a plate shape, and a cover glass was adhered to the plate to obtain a bead-filled composite sheet support shown in FIG. 1 (b). When the same comparison was made, a relative sensitivity of 125 was obtained.

Example 3 A felt made of carbon fiber was bonded to a cover glass,
A composite sheet support shown in FIG. 1 (d) was obtained. Relative sensitivity
130 was obtained.

〔The invention's effect〕

According to the present invention, it is possible to provide a radiation image conversion panel having high durability and high sensitivity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a composite sheet support. FIG. 2 is a sectional view showing an example of an installation position of a moisture barrier layer of the composite sheet support. FIG. 3 is a sectional view of an embodiment of the conversion panel of the present invention. 1 ... high radiation transmitting body, 2 ... support layer, 3 ... reinforcing layer, 4 ... moisture blocking layer,

Claims (1)

(57) [Claims] 1. A radiation image conversion panel having a stimulable phosphor layer formed on a support, wherein the support comprises a material having a lower radiation absorptivity than the support. Conversion panel.