JPH0535400B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a radiation image conversion method, and more specifically, the invention relates to a method for converting a radiation image, and more specifically, by irradiating a radiation image conversion panel having a photostimulable phosphor layer with photostimulable excitation light, the radiation image can be converted into a radiation image. The present invention relates to a radiation image reading method in which a radiation image stored and recorded on a conversion panel is stimulated to emit light and then read photoelectrically. (Prior Art) Radiographic images such as X-ray images are often used for medical purposes. Conventionally, in order to obtain this radiographic image, a so-called radiographic method has been used in which a radiographic film made of a silver salt photosensitive material and an intensifying screen are combined. However, in recent years, with the advancement of diagnostic techniques for radiographic images, methods of obtaining radiographic images without using radiographic films made of silver salt photosensitive materials have been devised. Such a method involves causing the radiation transmitted through the object to be absorbed by some type of phosphor, and then exciting the phosphor with, for example, light or thermal energy, so that the phosphor absorbs the radiation due to the absorption. There is a method in which the accumulated radiation energy is emitted as fluorescent light, and this fluorescent light is detected and imaged.
Specifically, for example, British Patent No. 1462769 and Japanese Unexamined Patent Publication No. 51-29889 disclose a method of using a heat-stimulable phosphor as the phosphor. This method uses a radiation image conversion panel with a heat-stimulable phosphor layer formed on a support.The heat-stimulable phosphor layer of this radiation image conversion panel absorbs the radiation that has passed through the subject. Then, radiation energy corresponding to the radiation transmittance of each part of the subject is accumulated to form a latent image, and then this heat-stimulable phosphor layer is heated to excite it, and the radiation energy is accumulated in each part of the panel. The accumulated radiation energy is extracted as a light signal, and a radiation image is obtained by varying the intensity of this light. Also, for example, U.S. Patent No. 3,859,527 and
No. 12144 discloses a method of using a photostimulable phosphor as the phosphor. This method uses a radiation image conversion panel in which a photostimulable phosphor layer is formed on a support. After forming a latent image as described above, this photostimulable phosphor layer is photostimulated. By irradiating it with light, the radiation energy accumulated in each part of the panel is extracted as a light signal and a radiation image is obtained. This final image may be reproduced as a hard copy or on a CRT. These methods have the very practical advantage of being able to image over a much wider range of radiation exposures compared to radiographic systems using conventional silver halide photography. In other words, it is recognized that in a radiation image conversion panel, the amount of radiation exposure is proportional to the intensity or amount of stimulated luminescence emitted by stimulated excitation after accumulation of radiation, and therefore, Even if the amount of radiation exposure fluctuates significantly due to various photographing conditions, the reading gain of the stimulated luminescence is set to an appropriate value, the photoelectric conversion means reads it and converts it into an electrical signal, and this electrical signal is used to perform photographic sensitization. A radiation image that is not affected by fluctuations in radiation exposure can be obtained by outputting it as a visible image on a recording material such as a recording material or a display device such as a CRT. Furthermore, according to these methods, the radiation image stored and recorded on the radiation image conversion panel is converted into an electrical signal and then subjected to appropriate signal processing, and this electrical signal is used to convert recording materials such as photographic materials, CRTs, etc. By outputting the image as a visible image on a display device, a very large effect can be expected in that a radiation image with excellent diagnostic suitability can be obtained. As mentioned above, in a radiation imaging system using a radiation image conversion panel, the tube voltage of the radiation source is reduced by setting the reading gain to an appropriate value, photoelectrically converting stimulated luminescence, and outputting it as a visible image. or fluctuations in radiation exposure due to fluctuations in MAS values;
Even if the radiation energy accumulated in the radiation image conversion panel fluctuates due to factors such as variations in the sensitivity of the radiation image conversion panel, changes in exposure amount due to subject conditions, or differences in radiation transmittance depending on the subject, the radiation Even if the exposure dose is reduced,
It becomes possible to obtain radiographic images that are not affected by variations in these factors. Furthermore, by converting stimulated luminescence into an electrical signal and applying appropriate signal processing to this electrical signal, it is possible to obtain radiographic images suitable for diagnostic areas such as the chest and heart, improving diagnostic suitability. It becomes possible. However, in order to eliminate the effects of fluctuations in imaging conditions, etc., or to obtain radiation images with excellent diagnostic suitability, it is necessary to , information such as imaging methods such as contrast imaging is grasped before outputting visible images for observation and interpretation, and based on this grasped accumulated recorded information, the reading gain is adjusted to an appropriate value, or appropriate signal processing is performed. It is essential to do so. A method disclosed in Japanese Patent Application Laid-Open No. 55-50180 is known as a method of grasping the accumulated recording information of the radiation image recorded on the radiation image conversion panel prior to outputting such a visible image. This method is based on the knowledge that when the radiation image conversion panel is irradiated with radiation, the instantaneous light intensity or amount of light emitted from the radiation image conversion panel is proportional to the radiation energy stored and recorded in the photostimulable phosphor.
By detecting this instantaneous light emission, the accumulated recorded information of the radiation image is grasped, and appropriate signal processing is performed based on this information to obtain a radiation image with excellent suitability for diagnosis. According to this method,
Since it is possible to set the reading gain to an appropriate value or perform appropriate signal processing, it is possible to eliminate the effects of fluctuations in imaging conditions, or to obtain radiographic images with excellent diagnostic suitability. Generally speaking, the radiation irradiation department is spatially dispersed into multiple functional locations, and since the radiation irradiation department and the radiation image reading department are usually separated in position, a signal transmission system is constructed between them. However, the disadvantage is that the equipment becomes complicated and the cost inevitably increases. Furthermore, in JP-A-55-116340, a non-stimulable phosphor is provided near a radiation image conversion panel, and a photodetector detects the light emitted by the non-stimulable phosphor when recording a radiation image. A method for estimating accumulated record information of radiation images recorded on a radiation image conversion panel is disclosed. However, in addition to the drawbacks of the method disclosed in JP-A No. 55-50180 mentioned above, this method does not use the photostimulable fluorophore itself as a detection means, so it cannot be recorded on the radiation image conversion panel. The drawback is that the information obtained in this way is only indirectly estimated, and the reliability of the information thus obtained is low. Furthermore, a method disclosed in Japanese Patent Application Laid-Open No. 67240/1983 is also known as a method of grasping the accumulated record information of the radiation image recorded on the radiation image conversion panel prior to outputting the visible image. In this method, prior to the reading operation (hereinafter referred to as "main reading") to obtain a visible image for observation and interpretation of the accumulated record information of the radiation image recorded on the radiation image conversion panel, the radiation image used in the actual reading is used. A reading operation (hereinafter referred to as "pre-reading") for grasping the accumulated recorded information of the radiation image recorded on the radiation image conversion panel using stimulated excitation light having an energy lower than that of the exhaustion excitation light. The aim is to perform appropriate signal processing based on this information to obtain radiographic images with excellent diagnostic suitability. However, in this method, the closer the ratio of the photostimulated excitation light energy in the pre-reading to that in the main reading is to 1, the smaller the amount of radiation energy remaining and accumulated during the main reading. The light energy needs to be lower than that in the main reading,
To achieve this, it is necessary to increase the spot diameter of the stimulated excitation light in read-ahead, reduce the output of the stimulated excitation light, increase the scanning speed of the stimulated excitation light, or increase the moving speed of the radiation image conversion panel. Therefore, the structure of the radiation image reading device becomes extremely complicated. In addition, in this method, for the reasons mentioned above, it is necessary to make the stimulated excitation light energy in the pre-reading significantly lower than that in the main reading, and the stimulated luminescence produced by the pre-reading is extremely weak. . For this reason, it may be difficult to grasp the accumulated record information of radiographic images recorded on the radiographic image conversion panel with a sufficiently high precision by reading ahead, or it may be difficult to grasp the accumulated record information of the radiographic image recorded in the radiographic image conversion panel with a sufficiently high precision. However, this method had drawbacks such as the need to significantly improve the detection ability of the stimulated luminescence detection system in pre-reading. Furthermore, in this method, even if the stimulated excitation light energy in the pre-reading is made sufficiently lower than that in the main reading, it is inevitable that the accumulated radiation energy will dissipate, and as a result, the radiation energy will be emitted during the main reading due to the pre-reading. This method has the disadvantage that the stimulated luminescence intensity or amount of light emitted decreases, and the sensitivity of the system decreases. In addition, in the conventional method, a radiographic image conversion panel containing radiographic image information is selected from among a large number of stored files, and the re-examination area is used for reading operations (hereinafter referred to as It lacks the convenience of being able to perform post-reading. (Object of the Invention) The present invention has been made in view of the above-mentioned drawbacks in the radiation image conversion method using a radiation image conversion panel. It is an object of the present invention to provide a radiation image reading method that performs pre-reading that allows the accumulated recorded information of the radiation image to be easily and accurately detected prior to the actual reading to obtain a visual image. Another object of the present invention is to perform pre-reading to detect accumulated record information of the radiation image prior to actual reading to obtain a visible image for observation and interpretation of the radiation image. It is an object of the present invention to provide a radiation image reading method that performs pre-reading without reducing the stimulated luminescence intensity or light amount in the main reading performed. Another object of the present invention is to simply and accurately detect accumulated record information of the radiation image prior to actual reading to obtain a visible image for observation and interpretation of the radiation image, and to determine diagnostic suitability based on this information. An object of the present invention is to provide a radiation image reading method that performs pre-reading that can reproduce excellent radiation images. Still another object of the present invention is to provide a radiation image reading method that allows post-reading by picking up a radiation image conversion panel from an accumulated storage file and checking the image in order to compare and review accumulated recorded information of radiation images. be. (Structure of the Invention) In order to achieve the above object, the inventors have
A radiation image is accumulated and recorded on a radiation image conversion panel in which second stimulable phosphor layers are laminated next to each other, and the accumulated and recorded radiation image is transferred to each stimulable phosphor layer of the radiation image conversion panel. Produce photostimulated luminescence by sequentially stimulating photostimulation,
In a radiation image reading method in which this is read photoelectrically, the radiation image information accumulated and recorded in the second stimulable phosphor layer is grasped from the reading result of the first stimulable phosphor layer; A radiation image reading method characterized in that reading conditions for the second stimulable phosphor layer are set based on the information, and reading of the second stimulable phosphor layer is performed. It will be achieved. In an embodiment of the present invention, it is preferable that the thickness of the second stimulable phosphor layer of the radiation image conversion panel is thicker than the thickness of the first stimulable phosphor layer; In a preferred embodiment, the thickness of the first stimulable phosphor layer of the image conversion panel is 1/2 or less and 1/200 or more of the thickness of the second stimulable phosphor layer. In the present invention, the sublayer referred to below refers to at least the stimulable phosphor layer (functional unit layer), which is a layered structure that expresses the desired quality and quantity of functions (functional unit). This sub-layer is referred to as a layer of constituent personnel in charge of some functions, and each sub-layer constitutes a functional unit in which the functional unit layer is expressed synergistically or additively. Further, in an embodiment of the present invention, it is preferable to apply the reading conditions and/or the processing conditions applied to one photostimulable unit layer to other photostimulable unit layers to simplify device reading and operation. In addition, other photostimulable units may be added so as not to interfere with absorption of radiation, absorption of photostimulated excitation light, and stimulated luminescence of the photostimulable unit layer for practical observation and interpretation of radiographic images, which is the final objective of the present invention. The thickness of the layer is preferably thinner than the thickness of the photostimulable unit layer used for observation and interpretation. Further, a block is provided to block the photostimulated excitation light specifically allocated to the photostimulated unit layer so that the radiation energy accumulated in each of the photostimulated unit layers is not consumed by the photostimulated excitation light of other photostimulated unit layers. Preferably, the layer is provided adjacent to the side on which it serves the purpose of isolation. In the present invention, the chronological reading of the photostimulable unit layer is carried out in the above-mentioned pre-reading, main reading, and post-reading if necessary. That is, prior to actual reading of a visible image for full-scale observation and interpretation from a photostimulation unit layer provided for actual reading using photostimulation excitation light specifically allocated for actual reading, the radiation is The radiation image information stored in the image conversion panel is pre-read from the photostimulation unit layer provided for pre-reading using photostimulation excitation light that is specified and allocated for pre-reading, and the radiation image is converted into the radiographic image. By grasping the accumulated recorded information, then performing the main reading, and appropriately adjusting the reading gain based on the pre-read information, or by performing appropriate signal processing, it is possible to avoid the influence of fluctuations in photographing conditions. Alternatively, radiographic images with excellent observation and interpretability can be obtained. Further, for post-reading, the post-reading stimulable unit layer and specifically allocated stimulable excitation light may be set exclusively, or a pre-reading operation may be used instead. In the present invention, specifying and allocating the photostimulated excitation light to the photostimulated unit layer means that the photostimulated excitation light for reading each photostimulated unit layer is within a preferable range for reading the photostimulated unit layer. , and the range should be selected so as not to affect other unread stimulable unit layers. In order to specify and allocate photostimulable excitation light to the photostimulable unit layer, the photostimulable fluorophores in each photostimulable unit layer are provided with different photostimulable fluorophores whose photostimulable efficiency depends on photostimulative excitation energy. The wavelength of the photostimulable excitation light in each photostimulable unit layer may be changed by selecting and using the photoluminescent material from among the various photostimulable phosphors described below. By providing a photostimulation excitation light blocking layer, the photostimulation excitation light specifically allocated to one photostimulation unit layer may be prevented from being irradiated to other photostimulation unit layers. Combinations of methods may also be used. In addition, in the case of using the above-mentioned photostimulable phosphors whose stimulated luminescence efficiencies differ in the dependence of stimulated excitation energy, the term "stimulable phosphors whose stimulated luminescence efficiencies differ in their dependence on stimulated excitation energy" broadly refers to These are phosphors that require different types of stimulation to cause the stimulable luminescence of the stimulable phosphors, and narrowly speaking, the peak of the stimulable excitation spectrum is 50
Refers to fluorophores that differ from each other by mm or more. The present invention will be explained in detail below. As an example of an embodiment of the radiation image conversion panel according to the present invention, the second photostimulable unit layer on the radiation incident side is used for main reading to obtain a visible image for observation and interpretation of a radiation image (hereinafter referred to as main reading layer). ), the first photostimulable unit layer on the radiation emission side is used for pre-reading to obtain accumulated record information of the radiation image prior to actual reading (hereinafter referred to as pre-reading layer). The film thickness of the main reading layer of the radiation image conversion panel according to the present invention varies depending on the sensitivity required of the main reading layer, but is preferably selected from a range of 10 to 800 μm for practical purposes. The film thickness of the pre-reading layer of the radiation image conversion panel differs depending on the sensitivity required of the pre-reading layer as well as the main reading layer, and also depends on the film thickness of the main reading layer. Even though it's different. Comparing cases where the film thickness of the main reading layer is thick and thin,
When it is thick, the amount of radiation absorbed by the main reading layer increases and the amount of radiation reaching the pre-reading layer decreases, so it is necessary to increase the thickness of the pre-reading layer accordingly. Further, in general, the pre-reading layer that obtains accumulated recording information of radiographic images does not need to have higher sensitivity than the main reading layer that obtains visible images for observation and interpretation of the radiographic images, and therefore may be thinner than the main reading layer. . According to the present inventors, even if the thickness of the pre-reading layer is 1/2 or less of the thickness of the main reading layer, the accumulated recorded information of the radiation image can be obtained without any problem. However, if the thickness of the pre-reading layer is less than 1/200 of the thickness of the main reading layer, it becomes difficult to sufficiently grasp the accumulated recorded information of the radiation image, and this is not practical. Furthermore, if the read-ahead layer is thicker than necessary, the overall thickness of the radiation image conversion panel increases, making handling such as automatic transportation difficult, and the amount of phosphor used increases significantly. This is not preferable because it has drawbacks such as increased manufacturing cost. From the above, the thickness of the pre-reading layer of the radiation image conversion panel according to the present invention may be thinner than the main reading layer, preferably the thickness of the pre-reading layer is 1/2 or less of the thickness of the main reading layer, More preferably, the thickness is 1/2 to 1/200 of the thickness of the main reading layer. In the radiation image conversion panel according to the present invention, the stimulable phosphor means that after being irradiated with the first light or high-energy radiation,
A phosphor that exhibits stimulated luminescence corresponding to the amount of initial light or high-energy radiation irradiated by chemical or electrical stimulation (photostimulation excitation), but from a practical standpoint it is preferably a phosphor with a wavelength of 500 nm or more. It is a phosphor that exhibits stimulated luminescence by stimulated excitation light. Examples of the photostimulable phosphor used in the radiation image conversion panel of the present invention include BaSO ₄ :Ax (where A is Dy, Tb, and Tm) described in JP-A-48-80487.
At least one of the following, and x is 0.001≦x<
It is 1 mol%. ), a phosphor represented by JP-A-Sho
48-80488, a phosphor represented by MgSO ₄ :Ax (where A is either Ho or Dy, and 0.001≦x≦1 mol%), JP-A-48-80488
SrSO ₄ :Ax (However, A is
At least one of Dy, Tb and Tm,
x is 0.001≦x<1 mol%. ) is described in Japanese Patent Application Laid-open No. 51-29889.
Mn, Dy and Tb in Na ₂ SO ₄ , CaSO ₄ and BaSO ₄ etc.
A phosphor containing at least one of the following, JP-A-Sho
BeO, LiF, described in No. 52-30487,
Fluorescent substances such as MgSO ₄ and CaF ₂ , JP-A-53-39277
Li ₂ B ₄ O ₇ described in JP-A-54-47883: Fluorescent material such as Cu, Ag, Li ₂ O.
(B ₂ O ₂ )x:Cu (where x is 2<x≦3), and
Li ₂ O・(B ₂ O ₂ )x: Cu, Ag (however, x is 2<x≦
3), SrS:Ce, Sm, SrS:Eu, Sm, etc. described in US Pat. No. 3,859,527.
La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X
Examples include phosphors represented by (where X is halogen). Also, the ZnS:Cu,Pb phosphor described in JP-A-55-12142, whose general formula is BaO.
xAl ₂ O ₃ : Barium aluminate phosphor represented by Eu (however, 0.8≦x≦10) and whose general formula is M〓O・
xSiO ₂ :A (However, M〓 is Mg, Ca, Sr, Zn, Cd or
Ba and A is Ce, Tb, Eu, Tm, Pb, Tl, Bi
and Mn, and x is 0.5≦
x≦2.5. ) are alkaline earth metal silicate-based phosphors. In addition, the general formula is (Ba _1-xy Mg _x Ca _y )FX:eEu ²⁺ (However, X is at least one of Br and Cl, and x, y, and e are each 0<x+y≦0.6,
The number satisfies the following conditions: xy≠0 and 10 ^-6 ≦e≦5×10 ^-2 . ), the general formula of the alkaline earth fluorohalide phosphor described in JP-A-55-12144 is LnOX:xA (where Ln is at least one of La, Y, Gd, and Lu).
X represents Cl and/or Br, A represents Ce and/or Tb, and x represents a number satisfying 0<x<0.1. ), the general formula described in JP-A-55-12145 is (Ba _1-x M〓x)FX:yA (where M〓 is Mg, Ca, Sr, Zn and Cd). X is at least one of Cl, Br, and A is Eu, Tb, Ce, Tm, Dy,
At least one of Pr, Ho, Nd, Yd and Er
x and y represent numbers satisfying the conditions 0≦x≦0.6 and 0≦y≦0.2. ), the general formula described in JP-A No. 55-84389 is BaFX: xCe, yA (where X is at least one of Cl, Br, and A is In, Tl, at least one of Gd, Sm and Zr, x and y
are 0<x≦2×10 ^-1 and 0<y≦5×, respectively.
10 ^-2 . Fluorescent substance represented by
The general formula described in No. 160078 is M〓FX・xA:yLn (where M〓 is at least one of Ba, Mg, Ca, Sr, Zn, and Cd, and A is BeO, MgO, CaO,
SrO, BaO, _ZnO , _{Al2O3 , Y2O3} , _{La2O3 ,}
In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ ,
At least one of Nb ₂ O ₅ , Ta ₂ O ₅ and ThO ₂
Species, Ln are Eu, Tb, Ce, Tm, Dy, Pr, Ho,
At least one of Nd, Yb, Er, Sm and Gd
species, X is at least one of Cl, Br and I, and x and y are each 5×10 ^-5 ≦x
This is a number that satisfies the conditions of ≦0.5 and 0<y<0.2. ) Rare earth element-activated divalent metal fluorohalide phosphor, whose general formula is ZnS:A, CdS:
A, (Zn, Cd)S: A, ZnS: A, X and CdS:
A, X (However, A is Cu, Ag, Au or Mn,
X is halogen. ), the general formula described in JP-A-57-148285 []
Or [], General formula [] xM ₃ (PO ₄ ) ₂・NX ₂ :yA General formula [] M ₃ (PO ₄ ) ₂ :yA (In the formula, M and N are respectively Mg, Ca, Sr, Ba,
At least one of Zn and Cd, X, C, Cl,
At least one of Br and I, A is Eu, Tb,
Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb,
Represents at least one of Tl, Mn and Sn.
Furthermore, x and y are numbers that satisfy the conditions 0<x≦6 and 0≦y≦1. ), and the general formula [] or [] General formula [] nReX ₃・mAX′ ₂ : xEu General formula [] nReX′ ₃・mAX ₂ : xEu, ySm (in the formula, Re is La, At least one of Gd, Y, and Lu; A represents an alkaline earth metal; and at least one of Ba, Sr, and Ca; X and X' represent at least one of F, Cl, and Br; and y
are 1×10 ^-4 <x<3×10 ^-1 , 1×10 ^-4 <y<1
It is a number that satisfies the condition ×10 ^-1 , and n/m is 1 ×
The condition 10 ^-3 <n/m<7×10 ^-1 is satisfied. ) can be mentioned. however,
The photostimulable phosphor used in the radiation image conversion method of the present invention is not limited to the above-mentioned phosphor,
Needless to say, any phosphor may be used as long as it exhibits stimulated luminescence when irradiated with radiation and then irradiated with stimulated excitation light. The average particle size of the stimulable phosphor used is appropriately selected within the range of 0.1 to 100 μm, taking into consideration the sensitivity and granularity of the radiation image conversion panel.
More preferably, those having an average particle size of 1 to 30 μm are used. In the radiation image conversion panel according to the present invention,
Generally, the stimulable phosphors described above are dispersed in a suitable binder and applied in a uniform layer by conventional coating techniques. Examples of binders include proteins such as gelatin, polysaccharides such as dextran, or gum arabic, polyvinyl butyral,
Binders commonly used for layer formation such as polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride-vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, etc. used. Generally, the binder is used in an amount of 0.01 to 1 part by weight per 1 part by weight of the stimulable phosphor. However, from the viewpoint of the sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and from the viewpoint of ease of coating, it is more preferably in the range of 0.03 to 0.2 parts by weight. Furthermore, in the radiation image conversion panel according to the present invention, the photostimulable phosphor used in the main reading layer and the photostimulable phosphor used in the pre-reading layer may be the same or different as necessary. Good too. Further, each of the main reading layer and the pre-reading layer may consist not only of a single layer of stimulable unit layers but also of stimulable unit layers of two or more sublayers. Further, the photostimulable unit layer may have a distribution arrangement of the particle size of the phosphor particles in the layer thickness direction. The photostimulation excitation light blocking layer used in the radiation image conversion panel according to the present invention can be any material as long as it reflects and/or absorbs photostimulation excitation light, but how to handle it as a radiation image conversion panel A flexible material is preferred. From this point of view, for example, Al, Pb, Ni, Cu, Zn, Ag, Au,
Various sheets such as metal sheets made of metals such as Pt and Fe and their alloys, plastic film sheets such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film, and paper. Examples include shaped materials. However, when using a plastic film sheet or paper as a photostimulation excitation light blocking layer, these sheets themselves have almost no ability to block photostimulation excitation light. It is necessary to color the sheet itself so that it forms a layer. In order for the sheet to become an exhaustion excitation light reflecting layer, the sheet may be colored with a white pigment or the like, and in order to make it become an exhaustion excitation light absorption layer, the sheet may be made to become an exhaustion excitation light absorption layer. It may be colored with a pigment that absorbs light or a black pigment. Instead of coloring the sheet itself, a stimulated excitation light reflecting layer or an absorbing layer may be provided on one or both sides of the sheet. As the stimulated excitation light reflection layer, a metal reflection layer may be provided on the surface of the sheet by a method such as vapor deposition or sputtering, or a white pigment layer or the like may be provided by a method such as coating. As the photostimulation excitation light absorption layer, a pigment or a black pigment that absorbs photostimulation excitation light may be provided on the surface of the sheet by a method such as coating. Furthermore, if necessary, after coloring the sheet, a photostimulation excitation light reflection layer or an absorption layer may be provided on the surface thereof, or a photostimulation excitation light reflection layer may be provided on one side of the sheet and a photostimulation excitation light reflection layer is provided on the other side. An excitation light absorption layer may also be provided. Further, the photostimulation excitation light blocking layer may be formed by dispersing white powder, black powder, or the like in a resin and applying the same in addition to the sheet-like material. The film thickness of the stimulated excitation light blocking layer varies depending on the intensity of the stimulated excitation light used and the stimulated excitation light transmittance of the stimulated excitation light blocking layer, but it is practically 1 mm or less, preferably 400 μm or less. selected from a range. In the radiation image conversion panel according to the present invention, the photostimulation excitation light blocking layer can generally serve as a support for supporting the photostimulation unit layer. However, if the photostimulation excitation light blocking layer is thin or has great flexibility, a support may be provided. It is more preferable that the support is provided on the surface of the pre-reading layer opposite to the surface on which the main reading layer or the stimulation excitation light blocking layer is provided so as not to interfere with the main reading. As the support, sheet materials made from various materials such as various polymers and glass can be used.
In terms of handling as a radiation image conversion panel, it is preferable to use a material that can be processed into a flexible sheet or roll. From this point of view, plastic films such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film are particularly preferred. Further, in the radiation image conversion panel according to the present invention, a protective layer is generally provided to physically or chemically protect the surfaces of the main reading layer and the pre-reading layer. As the material for the protective layer, usual materials for the protective layer such as nitrocellulose, ethyl cellulose, cellulose acetate, polyester, and polyethylene terephthalate are used. The protective layer mentioned above is selected because it transmits stimulated luminescence and stimulated excitation light. Further, in the radiation image conversion panel according to the present invention, an adhesive layer is provided between the photostimulable phosphor layer group such as the main reading layer or the pre-reading layer and the photostimulable light blocking layer, the protective layer or the support. There is. Furthermore, in the radiation image conversion panel according to the present invention, for the purpose of improving sharpness,
146447, white powder may be dispersed in the photostimulable unit layer of the radiation image conversion panel, or the brightness of the radiation image conversion panel may be dispersed as disclosed in JP-A-55-136500. The exhaust unit layer may be colored with a colorant that absorbs photostimulation excitation light. Stimulated excitation light sources that can be preferably used for the main reading, pre-reading, and post-reading of the present invention include Aγ ⁺ laser, He-Cd laser, He-Ne laser, Kγ laser, Dye laser, YAG laser, CO ₂ laser, and There are lasers such as semiconductor lasers, LEDs, and lamps such as tungsten lamps, but lasers and LEDs are particularly preferable because they are excellent in terms of light convergence, light intensity, etc. Note that the wavelengths of the photostimulation excitation light specifically allocated to each photostimulation unit layer may be the same or different, and any combination may be used as required. The present invention will be explained below based on the drawings. FIG. 1 is a schematic diagram of a radiation image recording system including a radiation image reading device that is an embodiment of the present invention. In order to clearly indicate the chronological order during the explanation, the first and second words are added. In FIG. 1, 1 is a photographing section, 2 is a pre-reading section,
3 indicates a main reading section, and 4 indicates a reproduction recording section. In the imaging unit 1, the radiation emitted from the radiation source 101 toward the subject 102
2, the radiation image is absorbed by the radiation image conversion panel 103, and a radiation image of the subject is stored and recorded. The radiation image conversion panel 103 that has accumulated and recorded this radiation image is sent to the prereading section 2. In the pre-reading unit 2, the first stimulated excitation light 202 from the pre-read stimulated excitation light source 201 is passed through a filter 20 that selectively transmits only this stimulated excitation light.
After passing through the optical deflector 2, such as a galvano mirror,
04, the radiation is one-dimensionally deflected and incident on the first photostimulated unit layer of the radiation image conversion panel 103 via the plane reflecting mirror 205. Here, the pre-reading stimulated excitation light source 201 is selected so that the wavelength of the first stimulated excitation direction 202 and the wavelength range of stimulated luminescence from the first stimulated unit layer of the radiation image conversion panel 103 do not overlap. be done. On the other hand, radiation image conversion panel 103
is sub-scanned in the direction of the arrow 206, and as a result, the entire surface of the first stimulable unit layer of the radiation image conversion panel 103 is irradiated with the first stimulable excitation light. When irradiated with the first stimulated excitation light 202 in this way, the first stimulated unit layer of the radiation image conversion panel 103 emits stimulated luminescence in an amount proportional to the accumulated and recorded radiation energy, and this luminescence is incident on the pre-reading light guide 207. This light guide 207
has a linear entrance surface and is placed adjacent to the scanning line on the radiation image conversion panel 103, and has a circular exit surface and is placed on the light receiving surface of the photodetector 208 such as a photo-maru. Being close. A filter is attached to the light receiving surface of the photodetector 208, which transmits only light in the wavelength range of stimulated luminescence and cuts out the wavelength of the first stimulated excitation light 202.
It is designed to detect only stimulated luminescence. The output of the photodetector 208 is amplified by an amplifier 209,
The image is output as a visible image on an output device 210 such as a CRT. By visually observing this visible image, it becomes possible to grasp the accumulated recording information of the radiation image, that is, the recording state or recording pattern, in advance of the actual reading. The radiation image conversion panel 103 that has finished pre-reading is sent to the main reading section 3. In the main reading section 3, the second photostimulation excitation light 302 emitted from the main reading photostimulation excitation light source 301 is used.
After passing through a filter 303 that selectively transmits only this stimulated excitation light, the beam diameter is strictly adjusted by a beam expander 304, and a flat reflecting mirror 306 is used by an optical deflector 305 such as a galvanometer mirror. through the radiation image conversion panel 103
is incident on the second photostimulated unit layer in a one-dimensionally deflected manner. An f lens 307 is disposed between the optical deflector 305 and the plane reflecting mirror 306, and the second photostimulation excitation direction 302 scans the second photostimulation unit layer of the radiation image conversion panel 103. Also, the beam diameter is always uniform. Here, the stimulation excitation light source 301 for main reading is selected so that the wavelength range of the stimulated emission from the second stimulation unit layer of the radiation image conversion panel 103 of the wavelength of the second stimulation excitation direction 302 does not overlap. be done. On the other hand, the radiation image conversion panel 1
03 is sub-scanned in the direction of arrow 308, and as a result, the entire surface of the second stimulable unit layer of the radiation image conversion panel 103 is irradiated with the second exhaustion excitation light. When the second photostimulation excitation light 302 is irradiated in this way, the second photostimulation unit layer of the radiation image conversion panel 103 emits stimulated luminescence in an amount proportional to the accumulated and recorded radiation energy. The emitted light enters the main reading light guide 309 . This light guide 30
The stimulated luminescence guided by 9 is emitted from its exit surface and is received by photodetector 310. A filter that selectively transmits only light in the wavelength range of stimulated luminescence is attached to the light receiving surface of the photodetector 310, and the photodetector 310 is designed to detect only stimulated luminescence. There is. The output of the photodetector 310 is amplified by an amplifier 311, A/D converted by an A/D converter 312, and then an X-ray image with excellent diagnostic suitability is obtained by a signal processing circuit 313. The signal is processed as follows. Photodetector 31
0 and the amplification factor of the amplifier 311, A/D converter 3
The optimum conditions for the 12 recording scale factors and the signal processing conditions in the signal processing circuit 313 are selected by manually operating the control circuit 314 based on the visible image obtained in the look-ahead section 2. I can do it. In addition, when using a superimposition method or a subtract method that requires high-precision positioning, the radiation image in the radiation image reading device is Since the relative position of the conversion panel 103 can be found,
By providing a control zone in front of the main reading section, the relative position of the radiation image conversion panel can be precisely determined. The output from the signal processing circuit 313 is electrically transmitted to the recording section 4. In the reproducing/recording section 4, light 403 from a recording light source 402 is modulated by a light modulator 401 based on an image signal, and is scanned by a scanning mirror 404 over a photosensitive material 405 such as a photographic film. Further, since the photosensitive material 405 is sub-scanned in the direction of the arrow 406 in synchronization with the scanning of the light 403, the photosensitive material 405
A radiation image is output on 05. FIG. 2 shows another embodiment of the present invention, in which reading conditions and image processing conditions in main reading are used, using accumulated record information of radiation images recorded on the photostimulable phosphor obtained by pre-reading. This embodiment is the same as the embodiment shown in FIG. 1, except that the components are automatically controlled. That is, the accumulated record information of the radiation image obtained by pre-reading is input to the control circuit 314 of the main reading section 3. The control circuit 314 sets the amplification factor of the amplifier 311 according to the obtained accumulated recording information,
Outputs signals for setting the recording scale factor of the A/D converter and setting the reproduction image processing conditions of the signal processing circuit. The stimulated luminescence detected by the photodetector 310 during the main reading is converted into an electrical signal,
The signal is then amplified to an appropriate level by an amplifier 311 whose amplification factor is automatically set. A/D converter 312
Then, the signal is A/D converted using a scale factor suitable for the fluctuation range of the signal, and the signal processing circuit 313 automatically processes the signal so as to obtain a radiation image with excellent diagnostic suitability. Output. It goes without saying that the embodiments of the present invention are not limited to those described above, and various modifications are possible. For example, in the embodiment shown in FIG. 1, the main reading conditions are set by manually operating the control circuit based on the visible image obtained by pre-reading. depending on
A CRT control system may be provided in which the visible image displayed on the output device 210, such as a CRT, changes to one that is more suitable for diagnosis, and in this way, the conditions of the control circuit can be set more easily. be able to. Furthermore, the recording method in the reproducing/recording section 4 does not have to be a direct recording method using a recording light source; for example, the final signal obtained in the main reading section may be displayed as it is on an output device such as a CRT. Furthermore
A radiation image displayed on a CRT or the like may be output to a video printer or the like. Further, the photodetector does not have to be a single one with a light guide, but a plurality of phototransistors or phototransistors arranged in the main scanning direction can also be used. Furthermore, a reading section for pre-reading and main reading may be shared, and a single reading device may be used for pre-reading and main reading. Furthermore, in the embodiments described above, pre-reading is performed over the entire surface of the radiation image conversion panel, but it is not necessarily necessary to perform the pre-reading over the entire surface of the radiation image conversion panel. Furthermore, readout and gain adjustments can be made by changing the voltage applied to the photomultiply when a photomultiplier is used as a photodetector, in addition to changing the amplification factor of the amplifier as explained in the previous embodiment. Therefore, the gain of the photodetector may be changed directly, or the reading gain may be changed by controlling the laser light energy of the laser light source. (Effects of the Invention) As explained above, according to the present invention, it is not necessary to lower the photostimulation excitation light energy in pre-reading than that in main reading, so radiation image reading can be performed without requiring any special device for pre-reading. It becomes possible to reduce the cost of the device. Further, according to the present invention, by performing pre-reading, there is no reduction in the accumulated radiation energy that should be emitted during main reading, so it is possible to prevent a decrease in system sensitivity caused by pre-reading. Further, according to the present invention, the energy of the stimulable excitation light in the pre-reading does not need to be lower than that in the main reading, and can be determined arbitrarily, so that the radiation recorded on the stimulable phosphor panel by the pre-reading can be set arbitrarily. It becomes possible to accurately grasp the storage and recording state of images. Furthermore, according to the present invention, it is possible to accurately grasp in advance the accumulation and recording state of radiation images recorded on the photostimulable phosphor panel, so there is no need to use a reading system with an exceptionally wide dynamic range. In both cases, by appropriately adjusting the reading gain based on this accumulated record information, it is possible to always obtain radiographic images with excellent diagnostic suitability even if the imaging conditions etc. change. Further, according to the present invention, since the recording pattern of the radiation image recorded on the photostimulable phosphor panel can be known in advance, signal processing according to the recording pattern can be applied to the electrical signal after reading. , it becomes possible to obtain radiographic images with excellent diagnostic suitability. It also provides convenience in picking up and confirming radiographic images that have been filed by post-reading. The present invention has the above-mentioned effects and is industrially very useful. (Example) Next, the present invention will be explained in more detail with reference to Examples. Example 1 BaFBr: 8 parts by weight of Fu photostimulable phosphor and 1 part by weight of polyvinyl butyral resin were mixed and dispersed using 5 parts by weight of a solvent (cyclohexanone) to form a coating solution for a photostimulable phosphor layer. It was adjusted. Next, this coating solution was uniformly applied onto a horizontally placed transparent polyethylene terephthalate support having a thickness of 200 μm and air-dried to form a first photostimulable unit layer having a thickness of about 50 μm. In the same way, 50 μm of coating liquid was placed horizontally.
It was uniformly coated on black polyethylene terephthalate as a photostimulated light shear layer with a thickness of m and air-dried to form a second photostimulated unit layer with a thickness of about 300 μm. Note that an Al opposite layer was previously provided by vacuum deposition on the side opposite to the side on which the photostimulable unit layer of black polyethylene terephthalate was applied. Next, the first photostimulable unit layer above and the Al reflective layer side of black polyethylene terephthalate were bonded together. Furthermore, a solution of 1 part by weight of polymethyl methacrylate dissolved in 6 parts by weight of triol was applied to the opposite side of the second photostimulable unit layer from the side with the black polyethylene terephthalate, and air-dried to form a protective layer with a thickness of 5 μm. Formed. The thickness and structure of each layer of the radiation image conversion panel according to the present invention thus obtained are as shown below. Polymethyl methacrylate 5μm Second stimulable unit layer 300μm Black polyethylene terephthalate 50μm Al reflective layer <1μm First exhaustion unit layer 50μm Transparent polyethylene terephthalate 200μm This radiographic image conversion panel can be used to perform plain chest radiography with 100KVp X-rays. Then, the signals were read by a device used in the radiation image conversion method shown in FIG. 1, and the magnitudes of signals obtained by pre-reading and main reading were examined. The results are shown in Table 1. In Table 1, the signals obtained by pre-reading are expressed as (◎, ○, △, ×) according to the level at which the accumulated record information of X-rays recorded on the radiation image conversion panel can be grasped. ◎ indicates a case where it was understood well enough, and × indicates a case where it was not possible to grasp it well. Further, in Table 1, the signals obtained by the main reading are expressed as relative values, with the signal magnitude when only the main reading is performed without performing the pre-reading in this example as 1. In FIG. 1, a He--Ne laser (633 nm, 20 mW) was used as the stimulated excitation light source for pre-reading, and a He--Ne laser (633 nm, 20 mW) was used as the stimulated excitation light source for main reading. photodetector
A photo multiplier was used as 208310. The signal obtained by looking ahead is the photodetector 2.
08 was used, and the output signal of the photodetector 310 was used as the signal obtained by the main reading. Example 2 In Example 1, the thickness of the first photostimulated unit layer was
Example 1 except that the diameter was 1 μm and an Ar ⁺ laser (515 nm, 100 mW) was used as the stimulated excitation light source for look-ahead.
The study was conducted in the same manner. The results are also listed in Table 1. Example 3 In Example 1, the second photostimulated unit layer was 0.1YF ₃ ,
150μm of photostimulated sublayer consisting of 0.9BaFBrFu
An investigation was carried out in the same manner as in Example 1 except that two photostimulated sublayers of BaFBriFu with a thickness of 150 μm were used.
The results are also listed in Table 1. Example 4 A coating solution for a photostimulable phosphor layer prepared in the same manner as in Example 1 was uniformly applied onto transparent polyethylene terephthalate placed horizontally, and air-dried for about 10 minutes.
A second photostimulated unit layer with a thickness of 300 μm was formed. Next, 8 parts by weight of BaFCl:Eu,Tl photostimulable phosphor and polyvinibutyral resin were mixed and dispersed using 5 parts by weight of a solvent (cyclohexanone), and a coating solution for other photostimulable phosphor layer was added. This was applied to the opposite side of the transparent polyethylene terephthalate from the side on which the second photostimulable unit layer was formed, and air-dried to form a first photostimulable unit layer with a thickness of about 100 μm. . The radiation image conversion panel according to the present invention thus obtained uses a semiconductor laser (1000 μm, 30 m
The study was carried out in the same manner as in Example 1 except that W) was used. The results are also listed in Table 1. Comparative Example 1 In the same manner as in Example 1, 8 parts by weight of BaFBR:Eu photostimulable phosphor and 1 part by weight of polyvinyl butyral resin were mixed and dispersed using 5 parts by weight of a solvent (cyclohexane) to produce photostimulable fluorophores. A coating solution for the light body layer was prepared. Next, this coating solution was uniformly applied onto a 200 μm thick polyethylene terephthalate support placed horizontally and air dried to form a stimulable phosphor layer about 300 μm thick. Furthermore, a solution of 1 part by weight of polymethyl methacrylate dissolved in 6 parts by weight of triol was applied to the opposite side of the stimulable phosphor layer from the support side, and air-dried to form a protective layer with a thickness of 5 μm. Using this comparison radiographic image conversion panel
A plain chest image was taken using 100 KVp X-rays, and then reading was performed using the method disclosed in Japanese Patent Application Laid-Open No. 58-67240, and the magnitude of the signal obtained by pre-reading and main reading was examined. The results are also listed in Table 1. The evaluation method is the same as in Example 1. Further, in this comparative example, a He--Ne laser (633 mm, 15 mW) was used as the stimulated excitation light source for pre-reading, and a He--Ne laser (633 mm, 20 mW) was used as the stimulated excitation light source for main reading. Comparative Example 2 In Comparative Example 1, an investigation was carried out in the same manner as in Comparative Example 1, except that a He--Ne laser (633 mm, 0.5 mW) was used as the pre-reading stimulated excitation light source. The results are also listed in Table 1.

[Table] From Table 1 above, the radiation image conversion panel of the present invention shown in Examples 1 to 4 can grasp the accumulated record information of the radiation image recorded in the radiation image conversion panel with high precision by pre-reading. Moreover, even if the pre-reading is performed, the signal strength read by the main reading does not decrease as much as when the pre-reading is not performed. On the other hand, in the radiation image conversion panels shown in Comparative Examples 1 and 2, when the accumulated record information of the radiation images recorded on the radiation image conversion panel is grasped with high precision by pre-reading, the signal strength in the main reading is significantly increased. Furthermore, if the reduction in signal strength in main reading is prevented, it is almost impossible to grasp the accumulated recorded information of the radiation image in pre-reading, so it is not put to practical use.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of a radiation image recording system including a radiation image reading device according to the present invention, respectively. 1... Photography department, 101... X-ray source, 102...
Subject, 103... Stimulable phosphor panel, 2...
Reading section for pre-reading, 201... laser light source for pre-reading, 202... laser light, 203... filter, 204... optical deflector, 205... plane reflecting mirror, 206... transport direction, 207... light for pre-reading Guide, 208...Photodetector, 209...Amplifier, 210...Output device, 3...Reading unit for main reading, 301...Laser light source for main reading, 302...
Laser light, 303... Filter, 304... Beam expander, 305... Light deflector, 306...
...Flat reflector, 307...f〓lens, 308...
Transfer direction, 309... Laser light source for book reading, 31
0...Photodetector, 311...Amplifier, 312...
A/D converter, 313...Signal processing circuit, 314
...Control circuit, 4...Recording section.

Claims (1)

[Scope of Claims] 1. A radiation image is accumulated and recorded on a radiation image conversion panel in which first and second stimulable phosphor layers are laminated next to each other, and the accumulated and recorded radiation image is transferred to the radiation image conversion panel. In a radiation image reading method in which each photostimulable phosphor layer is sequentially stimulated and excited to cause stimulated luminescence, and this is read photoelectrically, The radiation image information accumulated and recorded in the second stimulable phosphor layer is grasped, and the reading conditions for the second stimulable phosphor layer are set based on this information, and the second stimulable phosphor layer is read. A radiation image reading method characterized in that an exhaustible phosphor layer is read. 2. The method according to claim 1, wherein the thickness of the second stimulable phosphor layer of the radiation image conversion panel is thicker than the thickness of the first stimulable phosphor layer. Radiographic image reading method. 3. The thickness of the first stimulable phosphor layer of the radiation image conversion panel is 1/2 or less and 1/200 or more of the thickness of the second stimulable phosphor layer. A radiation image reading method according to claim 2.