JP3062280B2 - Radiation image reading method and radiation image conversion panel used in the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image reading method and a radiation image conversion panel used in the reading method.

[0002]

2. Description of the Related Art In the medical field, for example, radiation images such as X-ray images are often used for diagnosing diseases. As a method of forming such a radiation image, conventionally, X-rays transmitted through a subject are irradiated on a phosphor layer (fluorescent screen) to generate visible light, and this visible light is used in the same manner as when a normal photograph is taken. The so-called radiographic method of irradiating and developing a film using a silver salt has been generally used.

However, in recent years, as a method of directly taking out an image from a phosphor layer without using a film coated with a silver salt, radiation that has passed through a subject is absorbed by the phosphor, and then the phosphor is irradiated with light or heat, for example. A method has been proposed in which, by excitation with energy, radiation energy absorbed and accumulated in the phosphor is emitted as fluorescence, and the fluorescence is detected and imaged.

For example, US Pat. No. 3,859,527 and JP-A-55-12144 show a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulating excitation light. ing. In this method, a radiation image conversion panel having a stimulable phosphor layer formed on a substrate is used. A latent image is formed by accumulating radiation energy corresponding to the radiation transmittance of each part, and then the radiation energy accumulated in each part is stimulated by scanning the stimulable phosphor layer with stimulating excitation light. The light is emitted as light emission, and an optical signal based on the intensity of the light is photoelectrically converted, for example, and is imaged by an image reproducing apparatus. This final image is reproduced as a hard copy or on a CRT.

[0005] The conversion panel used in this radiation image conversion method accumulates radiation image information and then releases the stored energy by scanning with stimulating excitation light, so that the radiation image can be stored again after scanning. , Can be used repeatedly. Therefore, it is necessary for the conversion panel to have a performance that can be used repeatedly for a long time or many times without deteriorating the image quality of the radiation image. For that purpose, the stimulable phosphor layer in the conversion panel needs to be sufficiently protected from external physical or chemical stimuli.

Means for protecting the stimulable phosphor layer include:
Hitherto, means for providing a protective layer covering a stimulable phosphor layer provided on a support has been proposed. This protective layer,
For example, as described in JP-A-59-42500, a protective layer coating solution is formed by directly applying a coating solution for a protective layer on a stimulable phosphor layer, or a protective layer separately formed in advance is stimulated. It is formed by a method of bonding on the luminescent phosphor layer. The protective layer is generally formed using an organic polymer, and is formed as a thin layer so as not to lower the sharpness of an image.

However, since the thin protective layer made of an organic polymer shows a certain degree of moisture and / or moisture permeability, the stimulable phosphor layer absorbs the moisture, and as a result, the radiation of the conversion panel is reduced. The decrease in sensitivity or the decrease in stored energy until irradiation with stimulating excitation light is increased, leading to variation and / or deterioration in image quality of the obtained radiation image.

Further, in the conventional conversion panel, since the surface hardness of the protective layer is small, the protective layer surface may be damaged due to contact with a mechanical part such as a transport roller during transport, and a thin protective layer may have an impact resistance. Insufficient properties tend to cause cracks and breaks in the stimulable phosphor layer, and the quality of the obtained radiation image deteriorates with an increase in the number of repeated uses. On the other hand, if the protective layer is made thicker, defects caused by the thinner layer can be eliminated, but the sharpness is reduced as described above. Beyond this contradictory event, moisture proof without sacrificing sharpness,
Improvements in strength and impact resistance have been desired.

[0009] Under these circumstances, in a radiation image conversion panel having a stimulable phosphor layer on a support and at least one protective layer, a lower level than the protective layer is provided between the stimulable phosphor layer and the protective layer. A radiation image conversion panel provided with a layer having a refractive index has been proposed (see Japanese Patent Application No. 63-6474).

[0010]

[Problems to be solved by the invention]
The technique of -6474 still has a problem of low sharpness. Further, there is a problem that the range of choice of the constituent material of the support is small. That is, after the stimulable phosphor is vapor-deposited on the support, it is heat-treated. In this case, the support is required to have heat resistance. In addition, when the support is irradiated with radiation, it is required that the absorption of radiation be small. The material of the support that satisfies such requirements is limited, and has been an obstacle to practical use. Further, when the low-refractive-index layer is thick, the distance between the stimulable phosphor and the light-collecting system is large because the stimulable excitation light is applied to the stimulable phosphor layer via the low-refractive-index layer. Also, there is a problem that the sensitivity is lowered due to a reduction in the light collection efficiency.

Accordingly, a first object of the present invention is to provide a radiographic image reading method capable of reading a radiographic image without reducing sharpness and sensitivity. A second object of the present invention is to provide a radiation image conversion panel which has a wide selection range of constituent materials necessary for improving sharpness and sensitivity, and can be suitably used in the reading method.

[0012]

According to the present invention, there is provided a method for reading a radiographic image, comprising the steps of: providing at least a heat-treated stimulable phosphor layer and a second protective layer between a first protective layer and a second protective layer; Radiation transmitted through a subject is exposed to a radiation image conversion panel having a layer having a lower refractive index than the second protective layer provided on the side (hereinafter, appropriately referred to as a “low refractive index layer”). After accumulating the image information, the radiation image information is read by being excited by stimulating excitation light from the first protective layer side of the radiation image conversion panel. The radiation image conversion panel of the present invention is a radiation image conversion panel used in the above reading method, wherein the second protective layer has a light blocking layer.

[0013]

According to the present invention, since the low refractive index layer is provided on the side of the second protective layer, when the stimulable phosphor layer is subjected to the heat treatment, the second protective layer is subjected to the heat treatment atmosphere. You do not need to leave. Therefore, heat resistance is not required for the second protective layer, the range of choice of constituent materials is widened, and the second protective layer can be advantageously configured to improve sharpness and sensitivity. Further, since the low refractive index layer is provided on the second protective layer side, the stimulable phosphor layer is irradiated with the stimulating excitation light without passing through the low refractive index layer. Even so, the distance between the stimulable phosphor layer and the light-collecting system can be kept constant, and a decrease in sensitivity due to an increase in the distance can be prevented. According to the radiation image conversion panel in which the second protective layer has a light shielding layer, sharpness and sensitivity can be further improved.

Hereinafter, the radiation image reading method of the present invention and the radiation image conversion panel used in the method will be specifically described. FIG. 1 is a sectional view showing an example of a radiation image conversion panel used in the reading method of the present invention. 1 is a second protective layer, 2 is a low refractive index layer, 3 is a stimulable phosphor layer,
Denotes a first protective layer, which is formed in this order. FIG.
FIG. 4 is a cross-sectional view showing another example of the radiation image conversion panel used in the reading method of the present invention. This is an example in which a second low refractive index layer 5 is added between the stimulable phosphor layer 3 and the first protective layer 4 in the radiation image conversion panel of FIG.

In the reading method of the present invention, the radiation transmitted through the subject is exposed to the radiation image conversion panel shown in FIG. 1 or 2 to accumulate radiation image information, and then the first protection of the radiation image conversion panel is performed. The radiation image information is read by excitation with stimulating excitation light from the layer 4 side.

The stimulable phosphor layer 3 is preferably made of an alkali halide as described in detail later. The stimulable phosphor layer is preferably formed by a vapor deposition method. Examples of the vapor deposition method include a vapor deposition method, a sputtering method, and an ion plating method.

Although it is more preferable that the first protective layer 4 and the stimulable phosphor layer 3 are optically continuous, the refractive index is lower than that of the first protective layer 4 as shown in FIG. A layer with a refractive index (second low refractive index layer) 5 may be present. The low-refractive-index layer 2 or 5 is used to improve the sharpness of a radiation image, and is, for example, CaF ₂ (refractive index 1.23 to 1.26).
And the like, a layer made of a gas such as air, nitrogen, and argon, and a layer having a refractive index of substantially 1 such as a vacuum layer. It is preferable that the refractive index of the low refractive index layer 2 is small. As for the thickness of the low refractive index layer 2 or 5, the sharpness increases as the thickness increases, but it is usually preferably 0.05 to 5 mm. Low refractive index layer 2
Alternatively, 5 is preferably in close contact with the stimulable phosphor layer 3. Therefore, when the low-refractive-index layer is a gas layer or a vacuum layer, it may be left as it is, but the low-refractive-index layer is made of CaF _2. In such a case, the low refractive index layer is brought into close contact with the stimulable phosphor layer using, for example, an adhesive.

The first protective layer 4 and the second protective layer 1
It is provided to protect the stimulable phosphor layer 3 physically or chemically. As the first protective layer 4,
For example, those made of plate glass such as quartz, borosilicate glass, and chemically strengthened glass are used. It is preferable that the stimulable phosphor layer has heat resistance enough to withstand the heat treatment, and that the stimulable phosphor layer has a light transmittance of 80% or more for stimulating excitation light and stimulating light emission. For example, borosilicate glass is 330nm
It shows a light transmittance of 80% or more in a wavelength range of up to 2.6 μm, and quartz glass shows a high light transmittance even at a shorter wavelength. The refractive index of the first protective layer 4 is usually 1.4 to 2.
A range of 5 is preferred.

The second protective layer 1 can be formed by appropriately selecting from a wide range of materials such as various polymer materials, glass, and ceramics. Particularly, organic materials such as carbon and polyethylene terephthalate (PET) are preferably used. When using these materials, it is preferable to further coat a moisture-proof layer (for example, a metal foil) from the viewpoint of increasing the moisture resistance. In addition, since these organic materials have a higher X-ray transmittance than glass, a metal plate, or the like, it is preferable to make X-rays incident from the second protective layer side in terms of improving sensitivity.

The second protective layer 1 preferably has a light blocking layer. This is particularly important when the second protective layer 1 has high transparency to stimulating light. The light blocking layer is provided between the second protective layer 1 and the first low refractive index layer 2.

The light-blocking layer functions to absorb the stimulating excitation light (light absorbing layer) or reflect the light inside or on the surface of the layer (light reflecting layer) to prevent the transmission of the stimulating excitation light. This is a layer that exerts a light transmittance of preferably 10% or less, particularly preferably 2% or less. The light transmittance was measured using "557 Spectrophotometer" manufactured by Hitachi, Ltd., with air as 100%. As a constituent material of the light absorbing layer, for example, black ceramics such as titanium oxide, chromium oxide, a mixture of aluminum oxide and titanium oxide,
Carbon black, various colorants that absorb stimulating light, and the like are used.

The colorant used in the light-absorbing layer is a colorant that absorbs at least a part of the stimulating excitation light, and particularly depends on the type of the stimulable phosphor to be applied. It is preferable to have light absorption characteristics such that the average reflectance for light in the stimulating emission wavelength region is smaller than the average reflectance for light in the stimulating emission wavelength region. As the colorant, any of an organic or inorganic colorant may be used, but a blue or green colorant is useful. Organic colorants include Zapon Fast Blue 3
G (manufactured by Saechist) Estrol Brill Blue N-3R
L (Sumitomo Chemical), D & C Blue No. 1 (National Aniline), Spirit Blue (Hodogaya Chemical), Oil Blue No. 603 (Orient), Kitten Blue A
(Manufactured by Ciba-Geigy), Eizenkatilon Blue GLH
(Hodogaya Chemical), Lake Blue AFH (Kyowa Sangyo)
Primocyanin 6GX (product of Inabata Sangyo), prill acid green 6BH (product of Hodogaya Chemical), cyanine blue BN
RS (manufactured by Toyo Ink), Lionol Bruo-SL (manufactured by Toyo Ink) and the like are used.

In addition, color index No. 2441
1, 23160, 74180, 74200, 2280
0, 23150, 23155, 24401, 1488
0, 15050, 15706, 15707, 1794
1, 74220, 13425, 13361, 1342
0, 11836, 74140, 74380, 7435
Organic metal complex salt coloring agents such as 0, 74460 and the like are also included. Ultramarine, cobalt blue, cerulean blue, chromium oxide, TiO ₂ —ZnO—Co
O-NiO-based pigments are exemplified.

The method of forming the light absorbing layer is appropriately selected depending on the constituent materials. For example, when a black ceramic is used, a method such as a coating method and a thermal spraying method is applied. Examples of the thermal spraying method include a gas thermal spraying method using a gas high-temperature flame as a heat source, and an electric thermal spraying method using an arc or plasma as a heat source. When carbon black or various coloring agents are used, a method of dispersing or mixing and applying to an organic polymer material is applied. The thickness of the light-absorbing layer is preferably 10 to 100 μm when using a production method such as a thermal spraying method, and 0.5 to 80 μm when using a coating method.

The light reflecting layer has a function of reflecting and scattering stimulating light and / or stimulating light inside or on the surface. The thickness of the light reflecting layer is intended to prevent sharpness and reduction in sensitivity. Therefore, the thickness is preferably 100 μm or less. Further, the light reflectance is preferably 40% or more, particularly preferably 60% or more. Further, it is preferable that the light reflectance of the stimulated emission is larger than that of the excitation light. In addition, the light reflectance is 100% for a standard white plate (MgO).
The percentage is measured using "557 Spectrophotometer" manufactured by Hitachi, Ltd.

As a constituent material of the light reflecting layer, white pigments such as lead white, zinc sulfide and titanium oxide white, aluminum oxide,
Ceramics such as aluminum oxide-titanium oxide, aluminum oxide-silicon dioxide, zirconium oxide-magnesium oxide, aluminum, gold, silver, chromium, platinum,
Metals such as nickel and rhodium are used. When a metal is used as the light reflection layer, the light reflection layer may be formed of a multilayer film with a metal oxide. Particularly, a combination of a metal layer such as aluminum (Al) or chromium (Cr) and a CrO ₂ layer, a combination of the metal layer, a SiO ₂ layer and a ZrO ₂ layer, and a combination of the metal layer and S
A combination of an TiO ₂ layer and a TiO layer is preferred.

Since it is important that the light reflection layer is a layer that exhibits an effect of preventing the transmission of stimulating excitation light, the light reflection layer has a large light transmittance (particularly, a light transmittance of 10%). ), It may be used in combination with the light absorbing layer.
When the light absorbing layer and the light reflecting layer are used in combination, the positional relationship between the light absorbing layer and the light reflecting layer is such that the light absorbing layer 23 and the light reflecting layer are disposed on the second protective layer 1 as shown in FIG. Preferably, the layers 24 are provided in this order. The light blocking layer may be configured so that the second protective layer 1 has its function. In addition, as shown in FIG. 7, it is also possible to configure so that the moisture-proof layer provided on the second protective layer 1 as required has the function of a light shielding layer. The thickness of the first protective layer 4 and the second protective layer 1 is usually about 10 μm to 3 mm, but in order to obtain good moisture resistance and durability, 0.5
mm or more is preferable.

In the present invention, the term “stimulable phosphor” refers to a stimulus such as optical, thermal, mechanical, chemical, or electrical (stimulated excitation) after the first irradiation of light or high-energy radiation. ) Means a phosphor that exhibits stimulated emission corresponding to the amount of initial light or high-energy radiation, but from a practical point of view, a phosphor that exhibits stimulated emission by a stimulated excitation light having a wavelength of 500 nm or more. The body is preferred.

Examples of the stimulable phosphor constituting the stimulable phosphor layer include BaSO ₄ : AX described in JP-A-48-80487 and JP-A-48-80489. SrSO ₄ : AX, Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-53-39277, etc.
Li ₂ O · (B ₂ O) described in JP-A-54-47883
_{2) x:} Cu and _{Li 2 O · (B 2 O} 2) x: Cu,
Ag, et al., US Pat. No. 3,859,527, SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O
₂ S: Eu, Sm and (Zn, Cd) S: phosphor represented by Mn, and the like.

Further, a ZnS: Cu, Pb phosphor described in JP-A-55-12142, a general formula of BaO.xA
l ₂ O ₃ : barium aluminate phosphor represented by Eu;
And an alkaline earth metal silicate-based phosphor represented by the general formula M ^II O.xSiO ₂ : A. Also, an alkaline earth fluorohalide phosphor represented by the general formula (Ba _1-xy Mg _x C _ay ) FX: eEu ^{2+ described} in JP-A-55-12143 is disclosed. - formula is described in JP twelve thousand one hundred forty-four LnOX: phosphor represented by xA, the general formulas described in _{JP-a-55- 12145 (Ba 1-x M} II x) FX: Table in yA The phosphor represented by the formula BaFX: xCe, yA described in JP-A-55-84389, the phosphor represented by the general formula M ^II FX described in JP-A-55-160078 XA: a rare earth element-activated divalent metal fluorohalide phosphor represented by yLn, general formula ZnS: A, CdS: A, (Zn, Cd)
S: A, S: A, ZnS: A, X and CdS: A, X
And a phosphor represented by any of the following general formulas xM ₃ (PO ₄ ) ₂ .NX ₂ : yA M ₃ (PO ₄ ) ₂ : yA described in JP-A-59-38278. that phosphor, following any of formulas _{nReX 3 · mAX '2: xEu} nReX 3 · mAX' 2: xEu, phosphor represented by YSM, and the following general formula ^{M I X · aM II X '} 2 · bM ^And alkali halide phosphors represented by ^III X ″ ₃ : cA, etc. In particular, alkali halide phosphors are preferable because they can form a stimulable phosphor layer by a method such as vapor deposition or sputtering.

However, the stimulable phosphor used in the conversion panel according to the present invention is not limited to the above-described phosphor, and the stimulable phosphor emits stimulable light when irradiated with radiation and then irradiated with stimulating excitation light. Any phosphor may be used as long as it is the phosphor shown. The conversion panel according to the present invention may be a stimulable phosphor layer group including one or more stimulable phosphor layers containing at least one of the stimulable phosphors.
Also, the stimulable phosphor contained in each stimulable phosphor layer may be the same or different. In the present invention, the stimulable phosphor layer may be formed by either a coating method or a vapor phase growth method.

The thickness of the stimulable phosphor layer of the conversion panel according to the present invention varies depending on the sensitivity of the intended conversion panel to radiation, the type of stimulable phosphor, and the like. It is preferably selected from the range of 10 μm to 1000 μm, more preferably from the range of 20 μm to 800 μm, and in the case of containing a binder, the range of 20 μm to 1000 μm,
More preferably, it is preferably selected from the range of 50 μm to 500 μm.

FIG. 4 schematically shows a radiation image conversion apparatus used to carry out the radiation image reading method of the present invention, wherein 15 is a radiation generator, 16 is a subject, 17 is a radiation image conversion panel, and 18 is stimulating light. An excitation light source, 19 is a photoelectric conversion device for detecting stimulated emission emitted from the radiation image conversion panel 17, 20 is a reproducing device for reproducing a signal detected by the photoelectric conversion device 19 as an image, and 21 is a reproducing device 20.
A display device 22 for displaying an image reproduced by means of a filter 22 separates the photostimulated excitation light and the photostimulated light and transmits only the photostimulated light.

In this radiation image converter, radiation from the radiation generator 15 enters the radiation image conversion panel 17 through the subject 16. The incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 17 and its energy is accumulated, thereby forming an accumulated radiation transmission image. Next, this accumulated image is excited by stimulating light from the stimulating light source 18 and emitted as stimulating light.
Since the intensity of the emitted stimulating luminescence is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by a photoelectric conversion device 19 such as a photomultiplier tube, and reproduced as an image by a reproduction device 20, By displaying the image on the display device 21, a radiation transmission image of the subject 16 can be observed.

[0035]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. Examples 1 to 18 In each of the examples, the second protective layer, the first protective layer, and the low-refractive-index layer were prepared by using those shown in Tables 1 and 2 below.
A radiation image conversion panel of the present invention was produced as follows.

On the first protective layer, an alkali halide phosphor base material (RbBr) was deposited to a thickness of 300 μm by an evaporation method. This plate and RbBr: 5 × 10 ^-4 Tl
The mixed powder having the composition of Br was placed in the heat treatment container shown in FIG. 5 and heat treated at a temperature of 500 ° C. for 2 hours to form a stimulable phosphor layer. In FIG. 5, reference numeral 10 denotes a plate, 11 denotes a heater, 12 denotes a heat treatment furnace, 13 denotes an atmosphere powder containing at least an activator, and 14 denotes a heat treatment container. Next, as shown in FIG. 1, a low refractive index layer was provided on the stimulable phosphor layer side, and a second protective layer was further provided. Furthermore, after performing vacuum drying for 1 hour at a temperature of 80 ° C. and 10 ⁻³ Torr, the side edges of the first protective layer and the second protective layer are sealed with an epoxy resin adhesive. The radiation image conversion panel of the present invention was produced.

Using each of these radiation image conversion panels, X-rays transmitted through the subject are exposed from the second protective layer side of the radiation image conversion panel, and the radiation image information is accumulated. The radiation image information was read out by exciting with stimulating excitation light from the first protective layer side, and the radiation sensitivity and sharpness by MTF were evaluated as follows. The results are as shown in Table 4 below.

Sharpness After attaching the CTF chart to the radiation image conversion panel,
After irradiating X-rays with a tube voltage of 80 kV _PP at 10 mR (distance from the tube to the panel: 1.5 m), the semiconductor laser light (oscillation wavelength: 780 nm, beam diameter: 100 μm, power: 50 mW) is used to emit light. After excitation, the CTF chart image was read as stimulated emission emitted from the stimulable phosphor layer, and photoelectrically converted by a photodetector (photomultiplier) to obtain an image signal. Based on this signal value, the modulation transfer function (MTF) of the image was examined, and the sharpness of the radiation image was indicated by a relative value with the radiation image conversion panel obtained in Example 4 being 100. Note that MT
F is a value when the spatial frequency is 1 cycle / mm. Radiation sensitivity After the X-ray exposure, the amount of light emission when excited by a semiconductor laser beam was measured, and the relative value was set to 100 with the case of the radiation image conversion panel obtained in Example 4. The X-ray exposure conditions and the laser light irradiation conditions were the same as those for the evaluation of sharpness.

Example 19 As the second protective layer, the first protective layer, and the low refractive index layer, those shown in Table 2 below were used, and a particle size of 1 to 30 μm was formed on the first protective layer.
m granular stimulable phosphor BaFBr _0.8 I _0.2 : 0.0002
A radiation image conversion panel of the present invention was produced in the same manner as in Example 1 except that a dispersion containing Eu and an organic binder was applied and then dried without performing heat treatment. Using this radiation image conversion panel, radiation image information was read in the same manner as in Example 1, and the radiation sensitivity and sharpness by MTF were evaluated.
The results are as shown in Table 4 below.

[0040]

[Table 1]

However, in Table 1, crystallized glass + A
l ₂ O ₃ .TiO ₂ + Al ₂ O ₃ is obtained by providing a sprayed layer of Al ₂ O ₃ .TiO _{2 and} a sprayed layer of Al ₂ O ₃ in this order on a crystallized glass plate.

[0042]

[Table 2]

However, in Table 2, white PET + Al
The deposited film is made of PET (polyethylene terephthalate)
1 (aluminum) is deposited. Al plate + Cr + CrO ₂ is composed of Cr and CrO on Al plate.
_{The two} deposited films are provided in this order. Al plate + SiO ₂ + ZrO ₂ is made of SiO ₂
And ZrO ₂ deposited film in this order. The Al plate + SiO ₂ + TiO is obtained by providing a deposited film of SiO ₂ and TiO in this order on an Al plate. Crystallized glass + Al ₂ O ₃ · TiO ₂ + Al ₂ O ₃
Al ₂ O ₃ .TiO ₂ on the crystallized glass plate
₂ and an Al ₂ O ₃ coating layer in this order. The crystallized glass + Al ₂ O ₃ .TiO ₂ has an Al ₂ O ₃ coating layer provided on the crystallized glass plate on the side of excitation light irradiation.

Comparative Examples 1 to 5 In each of the comparative examples, the support, the protective layer, and the low refractive index layer were treated in the same manner as in Example 1 by using those shown in Table 3 below, and shown in FIG. A radiation image conversion panel for comparison of the configuration was produced. In FIG. 3, 6 is a support, 7 is a stimulable phosphor layer, 8 is a low refractive index layer, and 9 is a protective layer.
Using each of these comparative radiation image conversion panels, radiation image information was read in the same manner as in Example 1, and the radiation sensitivity and sharpness by MTF were evaluated. The results are as shown in Table 4 below.

Comparative Example 6 As the support, the protective layer and the low refractive index layer, those shown in Table 3 below were used, and a granular stimulable phosphor BaFBr _0.8 I _0.2 having a particle size of 1 to 30 μm was formed on the support: 0.0002. A radiation image conversion panel for comparison was produced in the same manner as in Example 1 except that a dispersion containing Eu and an organic binder was applied and then dried without performing heat treatment. Using this radiation image conversion panel, radiation image information was read in the same manner as in Example 1, and the radiation sensitivity and sharpness by MTF were evaluated. The results are as shown in Table 4 below.

[0046]

[Table 3]

However, in Table 3, crystallized glass + A
_{l 2 O 3 · TiO 2 +} Al 2 O 3 is a Al ₂ O ₃ · TiO ₂ coating layer on the side irradiated with the excitation light on the crystallized glass plate, A
A coating layer of l ₂ O ₃ is provided in this order. Al plate + Cr + CrO ₂ is composed of Cr and CrO on Al plate.
_{The two} deposited films are provided in this order. The crystallized glass + Al ₂ O ₃ .TiO ₂ has an Al ₂ O ₃ coating layer provided on the crystallized glass plate on the side of excitation light irradiation.

[0048]

[Table 4]

However, in Table 4, in Comparative Example 2, it was impossible to measure sharpness because Cr was eluted by the heat treatment.

Examples 20 and 21 In each of the examples, the second protective layer, the first protective layer, the second low refractive index layer, and the first low refractive index layer shown in Table 5 below were used. The radiation image conversion panel of the present invention having the configuration shown in FIG. However, after the second low refractive index layer and the stimulable phosphor layer were provided on the first protective layer, they were sealed with the second protective layer, and then processed in the same manner as in Example 1. . Using each of these radiation image conversion panels,
The radiation image information was read in the same manner as in Example 1, and the radiation sensitivity and sharpness by MTF were evaluated. The results are shown in Table 6 below.
As shown in FIG.

[0051]

[Table 5]

However, in Table 5, crystallized glass + A
l ₂ O ₃ .TiO ₂ + Al ₂ O ₃ is obtained by providing a sprayed layer of Al ₂ O ₃ .TiO _{2 and} a sprayed layer of Al ₂ O ₃ in this order on a crystallized glass plate.

[0053]

[Table 6]

As is clear from the above results, Example 1
In No. 1, since PET was used as the second protective layer, sensitivity was improved because X-ray absorption in the second protective layer was small. In Examples 13 to 15, the sensitivity and sharpness were improved because the multilayer light reflecting layer was provided on the second protective layer.
Examples 16 and 18 and Comparative Example 5 are examples in which only the light absorbing layer was used. In Example 19 and Comparative Example 6, BaF was used as the phosphor.
This is an example using Br _0.8 I _0.2 : 0.0002Eu.
As in the case of Br, the sharpness of the example was improved as compared with the comparative example. In Examples 20 and 21, the sharpness was improved as compared with Comparative Example 4 without the first low refractive index layer.

In order to evaluate the moisture proofness of the radiation image conversion panel, the sensitivity and the fading after being left for 48 hours under the condition of the temperature of 40 ° C. and the relative humidity of 90% were examined. No problem occurred in the radiation image conversion panel obtained in 1.

[0056]

As described in detail above, according to the present invention,
In this case, the low refractive index layer is provided on the second protective layer side.
When heat-treating the stimulable phosphor layer, the second protective layer
Need not be in an atmosphere of heat treatment, and
The heat resistance of the protective layer is not required, and the range of choice of constituent materials
In order to improve sharpness and sensitivity
Can be advantageously configured. Further , according to the radiation image reading method of the present invention, a radiation image can be read without a decrease in sharpness and a decrease in sensitivity. Further, according to the radiation image conversion panel of the present invention, the selection range of constituent materials necessary for improving sharpness and sensitivity is wide, and the panel can be suitably used for the radiation image reading method of the present invention.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a radiation image conversion panel according to the present invention.

FIG. 2 is a sectional view showing another example of the radiation image conversion panel according to the present invention.

FIG. 3 is a sectional view showing a conventional example of a radiation image conversion panel.

FIG. 4 is an explanatory view schematically showing a radiation image conversion apparatus.

FIG. 5 is a cross-sectional view illustrating an example of a heat treatment apparatus.

FIG. 6 is a sectional view showing another example of the radiation image conversion panel according to the present invention.

FIG. 7 is a sectional view showing another example of the radiation image conversion panel according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 second protective layer 2 low refractive index layer (first low refractive index layer) 3 stimulable phosphor layer 4 first protective layer 5 second low refractive index layer 6 support 7 stimulable phosphor Layer 8 Low refractive index layer 9 Protective layer 10 Plate 11 Heater 12 Heat treatment furnace 13 Atmospheric powder 14 Heat treatment container 15 Radiation generator 16 Subject 17 Radiation image conversion panel 18 Stimulation excitation light source 19 Photoelectric conversion device 20 Reproduction device 21 Display device 22 Filter 23 light absorption layer 24 light reflection layer 25 moisture proof layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-85800 (JP, A) JP-A-1-131499 (JP, A) JP-A-1-131498 (JP, A) JP-A-2-131 71200 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G21K 4/00 G03B 42/02

Claims (2)

(57) [Claims] 1. A photostimulable phosphor layer heat-treated between at least a first protective layer and a second protective layer, and a lower refractive index than a second protective layer provided on the second protective layer side. After the radiation transmitted through the subject is exposed to a radiation image conversion panel having a layer having a rate of radiation and the radiation image information is accumulated, the radiation image information is radiated from the first protective layer side of the radiation image conversion panel. A method for reading a radiation image, wherein the reading is performed by exciting with an excitation light. 2. A radiation image conversion panel used in the reading method according to claim 1, wherein the second protective layer has a light blocking layer.