JP2509812B2 - Storage device for radiation image conversion panel - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a means for storing a radiation image conversion panel having a stimulable phosphor, and more particularly to an apparatus for preventing deterioration of sensitivity and fading due to moisture.

BACKGROUND OF THE INVENTION

Radiation images such as X-ray images are often used for disease diagnosis. In order to obtain this X-ray image, X-rays that have passed through the subject are irradiated onto the phosphor layer (fluorescent screen) to generate visible light, which is the same as when taking a normal photograph. A so-called radiograph in which a film using a silver salt is irradiated and developed is used. However, in recent years, a method of directly taking out an image from the phosphor layer without using a film coated with silver salt has been devised. As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy, and the radiation energy accumulated by the phosphor is absorbed as fluorescence. This is a method of irradiating and imaging this fluorescence. Specifically, for example, U.S. 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 stimulated excitation light. This method uses a radiation image conversion panel (hereinafter referred to as a conversion panel) in which a stimulable phosphor layer is formed on a support. Radiation transmitted through an object in the stimulable phosphor layer of this conversion panel is used. The radiation energy corresponding to the radiation transmittance of each part of the subject is applied to form a latent image, and thereafter, this stimulable phosphor layer is scanned with the stimulable excitation light to accumulate the respective parts. Radiation energy is emitted and converted into light, and an image is obtained by an optical signal depending on the intensity of the light. This final image may be reproduced as a hard copy or may be reproduced on a CRT. The conversion panel used in this radiation image conversion method releases the stored energy by scanning the excitation light after storing the radiation image information, so that the radiation image can be stored again after the scanning and can be used repeatedly. is there. Therefore, it is desirable that the conversion panel has a performance that can be used for a long time or repeated many times without deteriorating the image quality of the obtained radiation image. For that purpose, the photostimulable phosphor layer in the radiation image conversion panel must be sufficiently protected from external physical or chemical stimuli. In particular, when the stimulable phosphor layer absorbs water, the radiation sensitivity of the radiation image conversion panel is lowered, or the holding time of the stored energy before receiving the excitation light is shortened, and the radiation image obtained is Since it causes deterioration of image quality, it has been desired to protect the photostimulable phosphor layer from moisture. In order to solve the above problems in the conventional conversion panel, a method of providing a protective layer for covering the stimulable phosphor layer on the support of the conversion panel has been adopted. This protective layer is formed, for example, as described in JP-A-59-42500, by directly applying a coating solution for a protective layer on the stimulable phosphor layer, or a protective layer separately formed in advance. Is adhered onto the stimulable phosphor layer. The inventors of the present invention have disclosed in JP-A-61-176900 that a resin material that is cured by polycondensation or crosslinking reaction by irradiation with radiation and / or heating, that is, a monomer, an oligomer, or a polymer (hereinafter, these are radiation-cured resins. Or a thermosetting resin) is applied onto the stimulable phosphor, and then the resin material is cured by irradiation with radiation and / or heating to form a protective layer. is suggesting. Furthermore, the present inventors have proposed in Japanese Patent Application No. 60-156346 a method of reducing the moisture permeability of a protective layer by a radiation image conversion panel having at least two layers having different hygroscopic properties. In order to achieve a longer life of the radiation image conversion panel as described above, further improvement is desired, particularly in terms of moisture resistance, but the measures for the conversion panel so far are not sufficient. It became clear that there is.

[Object of the invention]

The present invention has been made in view of the above-mentioned present situation relating to the conversion panel, and the purpose thereof is to prevent deterioration of the stimulable phosphor due to moisture, and enable use in a good state for a long period of time. The purpose is to provide a storage device for the conversion panel.

Configuration of the Invention

To achieve the above object, the present invention has a stimulable phosphor layer on a support, irradiation of radiation, reading of a radiation image,
In a storage device for a radiation image conversion panel that temporarily stores at least one of the radiation image conversion panels that are repeatedly used after erasing the afterimage, and the storage device is adsorbed to the radiation image conversion panel. The configuration is characterized in that a water removing means for removing water is provided. As the water removing means in the storage device of the present invention, the storage container for the conversion panel, that is, the storage part for the conversion panel in the storage device is made into an atmosphere which is shielded from the outside and sealed, and in the atmosphere, solid such as activated alumina or silica gel, or lithium chloride. , A method of dehumidifying by filling a hygroscopic substance composed of a liquid such as triethylenediglycol, a method of providing a portion for cooling and condensing moisture in the atmosphere, a drying method in which the air in the atmosphere is obtained by an external dehumidifier. The air in the atmosphere to remove moisture by vacuuming or depressurizing the atmosphere, dry the air in the atmosphere to an inert gas such as He, Ne, Ar or other dry gas such as N _2. A method of substituting may be considered. It is desirable that the water removing means keep the amount of water per container in the storage portion of the conversion panel at 25 mg / or less, more preferably at 15 mg / or less. That is, when the water content is more than this, the sensitivity of the stimulable phosphor is deteriorated and the fading in the dark (which is the phenomenon of regression of the latent image in the dark after the X-ray irradiation) is significantly accelerated. This is because the reading operation cannot be performed in time, and if the water content is more than this for a long period of time, the phosphor itself may be decomposed and may not be usable for a long period of time. Next, the conversion panel storage device of the present invention will be described with reference to the drawings. FIG. 1 illustrates various modes of the storage device. In either case, the storage part of the device is shut off from the outside,
The atmosphere of the sealed storage portion is affected by the moisture removing means. In the figure, reference numeral 132 is a water removing means for keeping the amount of water in the atmosphere at a constant value. FIG. 7A shows a case where a hygroscopic agent 133 such as activated alumina or silica gel is installed in the atmosphere sealed by the storage section 131. The hygroscopic agent 133 is preferably one that can be repeatedly used by removing moisture adsorbed by the hygroscopic agent by heat or the like. FIG. 2B shows a case where a compression type cooling and dehumidifying device 134 is provided outside the storage part 131. In this case, the air in the storage unit 131 is cooled to condense and remove moisture. FIG. 7C shows a case where the air in the storage unit 131 is dried by the external dehumidifier 135. The external dehumidifying device 135 may be a device using a hygroscopic agent such as activated alumina, silica gel, lithium chloride, triethylene diglycol, or the like.
Further, it may be a compression cooling type dehumidifier or the like. FIG. 1D shows a device 1 for vacuuming or depressurizing the inside of the housing 131.
This is the case when 36 is provided. In the same figure (e), the inside of the storage part 131 is filled with an inert gas such as He, Ne, Ar or other dry gas 137 such as N ₂ . The conversion panel storage device of the present invention may have a mechanism such as a shelf or a rack in which the conversion panel is stored, and unused conversion panels are preferably stored in the device of the present invention. When the conversion panel is housed in the storage device of the present invention, the moisture adsorbed on the phosphor is removed and the sensitivity is restored. The recovery rate depends on the amount of adsorbed water. Next, the water removal effect of the storage device of the present invention will be described. FIG. 2 shows the situation when the sensitivity is forcibly degraded at 40 ° C. and 90% relative humidity by using RbBr: 0.0015Tl ⁺ as the photoconductor. This figure shows an example of the amount of water adsorbed on the phosphor and the sensitivity.
It can be seen that the sensitivity becomes about 1/5 when it becomes about% or more.
Further, it was found that when BaFBr: Eu ²⁺ was used as a photoreceptor, the composition was decomposed when the sensitivity was forcibly deteriorated and no stimulated emission was shown. Fading in the dark also differs depending on the amount of moisture in the atmosphere. This state is shown in FIG. This figure shows RbB
r: 0.0015Tl ⁺ phosphor is dispersed in resin, coated on a support, and then a radiation image is recorded on a conversion panel laminated with a protective layer, and the stimulated emission is immediately read, and the signal intensity at that time is set to 1. The ordinate shows the stimulated emission intensity ratio, and the abscissa shows the time of leaving the storage device of the present invention in an atmosphere in which the amount of water is changed. Here, the curve (a) is the moisture content of the atmosphere.
If it is 50 mg /, (b) is 25 mg /
(C) is the case of 20 mg /. From this result, it can be seen that in (a), the reading is difficult because the attenuation is extremely fast. (B) and (c) can be read, and attenuation correction due to fading may be performed at this time. The photostimulable phosphor used in the phosphor layer of the radiation image conversion panel of the present invention has a photo-, thermal-, mechanical-, chemical-, electrical-, etc. after being irradiated with initial light or high-energy radiation. It refers to a phosphor that shows stimulated emission corresponding to the dose of the first light or high-energy radiation upon stimulation (stimulated excitation). Such a phosphor is described in, for example, JP-A-48-80487. BaSO ₄ : Ax (where A is D
At least one of y, Tb and Tm, and x is 0.001 ≦
x <1 mol%. ), A phosphor represented by
A phosphor represented by MgSO ₄ : Ax (where A is either Ho or Dy, 0.001 ≦ x ≦ 1 mol%) described in 80488, and described in JP-A-48-80489. SrSO ₄ : A
x (where A is at least one of Dy, Tb and Tm,
x is 0.001 ≦ x <1 mol%. ), Na ₂ SO ₄ , CaSO described in JP-A-51-29889
₄ and BaSO _{4 and the} like, a phosphor obtained by adding at least one of Mn, Dy and Tb, Be described in JP-A-52-30487.
Phosphors such as O, LiF, MgSO ₄ and CaF ₂ , phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-53-39277, JP-A-54-4
7883 No. Li ₂ O · (B ₂ O ₂ ) x: Cu (however, x
Is 2 <x ≦ 3), and Li ₂ O · (B ₂ O ₂ ) x: Cu, Ag (however,
x is a phosphor such as 2 <x ≦ 3), SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S described in US Pat. No. 3,859,527. : Mn, X (provided that X is a halogen). Further, ZnS is described in JP-A-55-12142: Cu, Pb phosphor general formula BaO · xAl ₂ O _3: Eu
(Provided that 0.8 ≦ x ≦ 10), and a barium aluminate phosphor represented by the general formula: M ^II O · xSio ₂ : A (where M ^II is Mg, C
a, Sr, Zn, Cd or Ba, A is at least one of Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn, and x is 0.5 ≦ x <2.5. ), An alkaline earth metal silicate-based phosphor represented by the formula: Further, the general formula is (Ba ₁ −x−yMgxCay) FX: eEu ²⁺ (where X is at least one of Br and Cl, x,
y and e are 0 <x + y ≦ 0.6, xy ≠ 0 and 10 ⁻⁶ ≦, respectively
It is a number that satisfies the condition of e ≦ 5 × 10 ^-2 . Alkaline earth fluoride halide phosphor represented by the formula:
The general formula described in No. 4 is LnOX: xA (where Ln is at least one of La, Y, Gd and Lu, and X is C
l and / or Br, A is Ce and / or Tb, x is 0 <x
Represents a number that satisfies <0.1. ), The general formula described in JP-A-55-12145 is (Ba ₁ −xM ^II x) FX: yA (where M ^II is Mg, Ca, Sr, Zn or Cd). At least one of them, X is at least one of Cl, Br and I, A
Is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er, and x and y are numbers satisfying the conditions 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2 . Phosphor) represented by
-84389 has the general formula of BaFX: xCe, yA (where X is at least one of Cl, Br and I, A
Is at least one of In, Tl, Gd, Sm and Zr,
x and y are 0 <x ≦ 2 × 10 ⁻¹ and 0 <y ≦ 5 ×, respectively.
10 ^-2 . ), The general formula described in JP-A-55-160078 is M ^II FX xA: yLn (where M ^II is at least Mg, Ca, Ba, Sr, Zn and Cd). A, BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O ₃ , Y ₂ O ₃ , La
₂ O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and
At least one of ThO ₂ , Ln is Eu, Tb, Ce, Tm, Dy, Pr,
Ho, Nd, Yb, Er, Sm and at least one of Gd,
X is at least one of Cl, Br and I, and x and y are numbers satisfying the conditions of 5 × 10 ⁻⁵ ≦ x ≦ 0.5 and 0 <y ≦ 0.2, respectively. Rare earth element activation 2)
Valence metal fluorohalide phosphor, with general formulas ZnS: A, CdS:
A, (Zn, Cd) S: A, ZnS: A, X and CdS: A (where A is Cu,
It is Ag, Au, or Mn, and X is halogen. ), Any one of the following general formulas described in JP-A-57-148285 xM ₃ (PO ₄ ) ₂ · NX ₂ : yA M ₃ (PO ₄ ) ₂ : yA (wherein M and N are at least one of Mg, Ca, Sr, Ba, Zn and Cd, X is at least one of F, Cl, Br and I, and A is Eu, Tb, Ce, Tm, Dy, Pr, Ho. , Nd, Yb, Er, Sb, Tl, Mn
And at least one of Sn. Further, x and y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. )
The phosphor represented by the general formula nReX ₃ · mAX ₂ ′: xEu nReX ₃ · mAX ₂ ′: xEu, ySm (wherein Re is at least one of La, Gd, Y and Lu, and A is Alkaline earth metal, at least one of Ba, Sr and Ca, and X and X'represent at least one of F, Cl and Br.
x and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ⁻⁴ <y <
It is a number that satisfies the condition 1 × 10 ^-1 , and n / m is 1 × 10 ^-3 <n
The condition of / m <7 × 10 ^{-1 is} satisfied. ), A phosphor represented by
And the following general formula _{^{M I X · aM II X 2}} '· bM III X 3 ": cA ( where, M ^I is at least one alkali metal selected Li, Na, K, from Rb and Cs, M ^II is BE, Mg, Ca, Sr, Ba, Zn, C
It is at least one divalent metal selected from d, Cu and Ni. M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
It is at least one trivalent metal selected from r, Tm, Yb, Lu, Al, Ga and In. X, X'and X "are at least one halogen selected from F, Cl, Br and I. A is Eu, Tb, C
e, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and M
It is at least one metal selected from g. A is a numerical value in the range of 0 ≦ a <0.5, and b is 0
It is a numerical value in the range of ≦ b <0.5, and c is a numerical value in the range of 0 <c ≦ 0.2. ) Alkali halide phosphors represented by). Among them, the alkali halide phosphor is preferable because the stimulable phosphor layer can be formed by a method such as vapor deposition and sputtering. Alkaline earth fluoride phosphors are also preferable. However, the stimulable phosphor used in the radiation image conversion panel of the present invention is not limited to the above-mentioned phosphor, and fluorescence that exhibits stimulated emission when irradiated with stimulated excitation light after irradiation with radiation. Any phosphor may be used as long as it is a body. As the light source for exciting excitation according to the present invention, a halogen lamp, a tungsten lamp, a fluorescent lamp, a sodium lamp,
Examples thereof include a xenon lamp, an electrodeless discharge lamp that uses microwaves, and a laser. As a laser, He
-Ne laser, the He-Cd laser, Ar ion laser, Kr ion laser, N ₂ laser, YAG laser and its second high long-wave, a ruby laser, a semiconductor laser, various dye lasers, copper vapor laser and the like metal vapor laser, etc. There is. When the light from the light source includes a portion overlapping the stimulated emission spectrum, it is preferable to use a filter that cuts the spectrum portion. Further, it is preferable to use a filter that transmits stimulated emission and cuts stimulated excitation light together in the photoelectric converter. Next, a radiation image reading method according to the present invention will be described with reference to the drawings. FIG. 4 is a schematic view showing an example of a radiation image reading apparatus using the conversion panel stored according to the present invention, which is an example in which an image recording unit and an image reading unit are integrated. Radiation source 10
The radiation emitted from 1 toward the subject 102 is the subject 102.
After being transmitted, the light is absorbed by the conversion panel 103, and the radiation image of the subject is accumulated and recorded therein. This conversion panel 103
Of the stimulable phosphor 104 at a position facing the surface of the stimulable phosphor 104, an excitation light source 105 that emits excitation light such as a laser beam, and the excitation light emitted from the excitation light source in the width direction of the conversion panel 103, for example, Optical polarizer 10 such as a nomometer mirror
6, a photodetector 107 for reading the stimulated emission light emitted by the stimulable phosphor 104 excited by the excitation light, and a light transfer means 108 for guiding the stimulated emission light to the photodetector 107 is a common carrier stage It is installed on 109. The photodetector 107 is composed of, for example, a photomultiplier tube, a photoelectron amplification channel plate, and the like, and photoelectrically detects the stimulated emission light guided by the light transmitting means 108. Further, an erasing light source 110 is provided at a position facing the phosphor-side surface of the conversion panel 103, and the erasing light source 110 is conveyed together with the conveying stage 109 in the direction of the arrow in the figure. The erasing light source 110
Is a light source that emits light including the excitation wavelength region of the phosphor to the stimulable phosphor 104, such as a halogen lamp and a tungsten lamp as shown in JP-A-56-11392.
An infrared lamp, an LED, a laser light source, or the like can be arbitrarily selected and used. The image-erased conversion panel 103 is taken out from the image reading device and stored in the storage device of the present invention. After the subject 102 is placed between the conversion panel 103 and the radiation source 101, when the radiation source 101 is turned on, a transmission radiation image of the subject 102 is recorded and accumulated in the stimulable phosphor 104 of the conversion panel 103. It After that, the conversion panel 103 is scanned by a photostimulable excitation light source such as a laser, and the photostimulable luminescence emitted from the photostimulable phosphor 104 is turned on by turning on the switch of the photodetector 107 and the photodetector via the light transmission means 108. Detected by 107. At this time, the transport stage 109 detects the stimulated emission of light of the entire panel 103 which is sub-scanned downward from above. This time-series stimulated emission electric signal is amplified by the amplifier 111, processed by the image information processing circuit 112, and then sent to the storage means 113. In this radiation image reading or the like, the conversion panel 103 has its moisture removed by the moisture removing means 132 of the storage device of the present invention, so that the sensitivity of the stimulable phosphor layer is improved and the subject 102 is exposed to radiation. The dose can be reduced.

【The invention's effect】

As described above, as in the present invention, a radiation having a stimulable phosphor layer on a support, irradiation of radiation, reading of a radiation image, and erasing of an afterimage are sequentially performed, and radiation is repeatedly used. The storage device for the radiation image conversion panel, which temporarily stores at least one of the image conversion panels, is provided with the water removal means for removing the water adsorbed to the radiation image conversion panel, so that Since deterioration can be suppressed and moisture adsorbed on the radiation image conversion panel can be removed, the sensitivity of the stimulable phosphor layer is restored, it can be used for a long time, and the retention time of accumulated energy can be extended. It has an excellent effect that it becomes possible.

[Brief description of drawings]

1 (a) to 1 (e) are schematic views showing a typical example of a storage device having a water removing means of the storage device of the present invention. FIG. 2 is a graph showing the relationship between the amount of water adsorbed on the phosphor and the sensitivity.
The figure is a graph showing the difference in fading in the dark depending on the atmospheric moisture content. FIG. 4 is a schematic view showing an example of the radiation image reading apparatus used in the present invention. 101 ... Radiation source, 102 ... Subject 103 ... Conversion panel, 104 ... Photostimulable phosphor 105 ... Excitation light source, 106 ... Polarizer 107 ... Photodetector, 108 ... Optical transmission means 109 ... … Conveyance stage, 110 …… Erasing power supply 131 …… Storage section, 132 …… Water removal means

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Claims (1)

(57) [Claims] 1. At least one radiation image conversion panel having a stimulable phosphor layer on a support, which is sequentially used for irradiation of radiation, reading of a radiation image, and erasing of an afterimage, and which is repeatedly used. In a storage device for a radiation image conversion panel for temporarily storing the above, the storage device is provided with a water removing means for removing water adsorbed on the radiation image conversion panel. apparatus.