JPS61267751A - Reading method for radiation picture - Google Patents

Abstract

PURPOSE:To utilize the titled reading method for the converting formation of a fine and purposeful radiation visible picture by detecting afterglow generated by a stimulable phosphor sheet after the irradiation of radiant rays, discriminating the characteristics of the radiation picture and adjusting the picture at the time of reading stage on the basis of the discriminated result. CONSTITUTION:A subject 202 e.g. is arranged between a conversion panel 202 and a radiant ray source 201 and the radiant ray source 201 is turned on, so that the transmitted radiation picture of the subject 202 is recorded and accumulated on the stimulable phosphor sheet 204 formed on a panel 203. Then, the afterglow generated by the phosphor 204 is detected through an optical transmission means 208 by turning on a switch of a photodetector 207. At that time, a carrying stage 209 is sub-scanned from upward to downward to detect the afterglow of the whole panel 203. The sequenced electric signals of the afterglow are amplified by an amplifier 211 and sent to a MAX/MIN value discriminating means 212 to discriminate the maximum and minimum luminance values on the picture. Since the quantity of afterglow is proportional to the accumulated capacity of energy to the phosphor 204, the maximum and minimum values of the afterglow are converted into the maximum and minimum values of energy on the basis of previously found conditions and stored in a storage means 214.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for reading a radiation image, and more specifically, it detects the afterglow emitted by a stimulable phosphor after irradiation with radiation and determines the characteristics of the radiation image in advance. , and relates to a radiation image reading method that performs an image adjustment operation at the reading stage based on this.

[Background of the invention]

Radiographic images such as X6 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 is combined with an intensifying screen. However, in recent years, with the advancement of radiographic image diagnostic technology, methods of obtaining radiographic images without using radiographic films made of silver salt photosensitive materials have been devised.

Such a method uses radiation that has passed through the subject (X
il, α rays, β rays, γ rays, ultraviolet rays, etc.) are absorbed by a certain type of phosphor, and then this phosphor is excited by, for example, light or thermal energy, so that the phosphor accumulates due to the absorption. There is a method of emitting the radiation energy as fluorescence, detecting this fluorescence, and creating an image. Specifically, for example, British Patent No. 1.462.769 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 in which a heat-stimulable phosphor layer is formed on a support, and the radiation transmitted through the subject is absorbed by the heat-stimulable phosphor layer of this radiation image conversion panel. 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 the radiation, and the latent image is accumulated in each part of the radiation image conversion panel. The radiation energy is extracted as a light signal, and a radiation image is obtained based on the intensity of this light.

Further, for example, U.S. Pat. No. 3,859,527 and Japanese Patent Application Laid-open No. 12144/1983 disclose a method of using a photoluminescent phosphor as the phosphor. This method uses a radiation image conversion panel with a photoluminescent phosphor layer formed on a support. After forming a latent image as described above, this photoluminescent phosphor layer is exposed to stimulated excitation light. By irradiating the panel, 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.
You can play it on top.

These methods have the very practical advantage of being able to image over a much wider range of radiation exposures than conventional radiographic systems using silver halide photography. In other words, it is recognized that in a radiation image conversion panel, the amount of radiation exposure and the intensity or amount of stimulated luminescence emitted by stimulated excitation after radiation accumulation are proportional to each other over a very wide range. Even if the amount of radiation exposure fluctuates significantly, the reading gain of the stimulated luminescence is set to an appropriate value, read by the charge conversion means and converted into an electrical signal, and this electrical signal is used to convert the photosensitive material, etc. By outputting the image as a visible image on a recording material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure can be obtained.

Furthermore, according to these methods, after converting the radiation image stored and recorded in the radiation image conversion panel into an electrical signal, appropriate signal processing is performed, and this electrical signal is used to convert recording materials such as photographic light-sensitive 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 radiation #I may be affected due to changes in radiation exposure amount due to changes in M and A S values, 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.
Even if the radiation energy stored in the image conversion panel fluctuates, and even if the radiation exposure dose is reduced, it is possible to obtain a radiation image that is not affected by fluctuations in these factors. In addition, 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. becomes.

However, in order to eliminate the influence of fluctuations in imaging conditions, etc., or to obtain radiographic images with excellent diagnostic suitability, it is necessary to change Information such as the imaging method (simple, contrast-enhanced, etc.) is grasped before outputting a visible image for observation and interpretation, and the reading gain is adjusted to an appropriate value based on the accumulated recorded information, or an appropriate signal is Treatment is essential.

A method disclosed in Japanese Patent Application Laid-Open No. 55-50180 is known as a method for grasping the accumulated record information of radiation images recorded on a radiation image conversion panel prior to outputting such visible images. This method is based on the knowledge that when the radiation image conversion panel is irradiated with radiation, the light intensity or amount of instantaneous light emitted from the radiation image conversion panel is proportional to the radiation energy stored and recorded in the stimulable phosphor. By detecting instantaneous light emission, accumulated recorded information on radiographic images is grasped, and appropriate signal processing is performed based on this information to obtain radiographic images with excellent diagnostic suitability. According to this method, it is possible to set the reading gain to an appropriate value or perform appropriate signal processing, thereby eliminating the influence of fluctuations in imaging conditions, or producing radiographic images with excellent diagnostic suitability. However, in general, the radiation irradiation department is spatially dispersed into multiple functional areas, and the radiation irradiation department and the radiation image reading department are usually separated in location. In the meantime, a signal transmission system must be constructed, which results in a complicated device and an unavoidable increase in cost.

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 disadvantages of the method disclosed in JP-A No. 55-50180 mentioned above, this method does not use the stimulable phosphor itself as a detection means, so the image is recorded on a radiation image conversion panel. The disadvantage is that the radiation image information is only estimated indirectly, and the reliability of the information obtained in this way is low.

Furthermore, a method disclosed in Japanese Patent Application Laid-Open No. 58-67240 is also known as a method for grasping the accumulated record information of a radiation image recorded on a radiation image conversion panel prior to outputting a visible image. In this method, prior to a 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 "prereading") for grasping the accumulated record 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, if the ratio of the stimulated excitation light energy in the pre-reading to that in the main reading is close to 1, the amount of residual and accumulated radiation energy during the near-preliminary reading will be small.
Therefore, the energy of the stimulated excitation light in the pre-reading must be lower than that in the main reading.To do this, the spot diameter of the stimulated excitation light in the pre-reading must be increased, the output of the photostimulated excitation light should be reduced, and the It is necessary to take measures such as increasing the scanning speed of light or increasing the moving speed of the radiation image conversion panel, which has the disadvantage that the structure of the radiation image reading device becomes extremely complicated.

1 In this method, for the reasons mentioned above,
It is necessary to make the stimulated excitation light energy in pre-reading significantly lower than that in main reading, and the stimulated luminescence produced by pre-reading is very weak. For this reason,
Radiation I by looking ahead! It may be difficult to grasp the accumulated record information of the radiation image recorded on the image conversion panel with a sufficiently high degree of accuracy, or in order to grasp the accumulated record information mentioned above with a sufficiently high degree of precision, it may be necessary to detect stimulated luminescence in the look-ahead. There were drawbacks such as the need to significantly improve the detection ability of the system. Furthermore, in this method, even if the stimulated excitation light energy in pre-reading is made sufficiently lower than that in main reading, it is inevitable that the accumulated radiation energy will dissipate, and as a result, it will be emitted during main reading by pre-reading. The disadvantage is that the stimulated luminescence intensity or amount of light decreases, and the sensitivity of the system decreases.

In addition, when the image information recording section and the image information reading section are integrated, that is, built-in type, which reads radiation image information immediately after recording and accumulating it, recording accumulation and reading are continuous, and in this case, after radiation irradiation, This has the disadvantage that the image is read before the afterglow has sufficiently attenuated, and the influence of the afterglow on the read image becomes large.

[Purpose of the invention]

The present invention was made in view of the above-mentioned drawbacks in the radiographic image conversion method using a radiographic image conversion panel (hereinafter abbreviated as conversion panel), and an object of the present invention is to improve the observation and interpretation of radiographic images. 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 detected simply and with high accuracy prior to the actual reading to obtain a visible image for the radiation image.

Another object of the present invention is that even if pre-reading is performed to detect accumulated record information of the radiation S image prior to the actual reading to obtain a visible image for observation and interpretation of the radiation image, it is possible to 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 provide a radiation image reading method that performs pre-reading without the influence of afterglow during main reading.

[Structure of the invention]

In order to achieve the above object, the present inventors have conducted extensive research on radiation image conversion methods using stimulable phosphors. As a result, they discovered that the stimulable phosphor emits part of the absorbed radiation energy as an afterglow, and the amount of this afterglow is proportional to the amount of energy stored in the stimulable phosphor. Ta. Therefore, in a radiation image reading method that reads an image from a stimulable phosphor irradiated with radiation imagewise, the afterglow emitted by the stimulable phosphor after irradiation with radiation is detected, and information regarding the characteristics of the radiation image is obtained. Thus, the present invention has been completed, which is a radiation image reading method characterized in that, in the step of reading the radiation image from the stimulable phosphor, a conversion is applied to the read signal based on the information.

The present invention will be explained in detail below.

In the present invention, afterglow refers to the light that is emitted after stimulating a photostimulable phosphor with radiation without photostimulation excitation, as shown in Figure 1.It is clearly defined as the instantaneous light that is emitted during photostimulation. It's different. In the present invention, after recording a radiation image on a stimulable phosphor, by detecting this afterglow, information regarding the characteristics of this image can be obtained from the above-mentioned image analysis using the afterglow.
This information can be applied in a later readout step from the stimulable phosphor to store the entire readout image information in a storage device at the same time as the readout, or to use this signal without having to wait until the readout of the entire image is complete. It is possible to obtain a desirable image by adding a conversion to the image.

Furthermore, the afterglow emitted as extra entropy until the record storage potential reaches an equilibrium state is utilized as status information of the record, and the image record is stored in a place where no damage is caused to the record. It has yet another advantage.

In the conversion panel used in the present invention, the stimulable phosphor refers to a stimulable phosphor that is stimulated by prior stimulation, thermal, mechanical, chemical, or electrical (stimulable excitation) after being irradiated with the first light or high-energy radiation. ) refers to a phosphor that exhibits stimulated luminescence corresponding to the amount of initial light or high-energy radiation irradiation, but from a practical standpoint, it is preferably a phosphor that exhibits stimulated luminescence by stimulated excitation light of 500 nm or more. It is. As the stimulable phosphor used in the present invention, for example, JP-A Darken-8
Baco4' AX described in No. 0487 (where A is at least one of py, 'rb, and addition, and X is 0.001≦x (1 mol%); Mg5O described in JP-A-48-80488
+ ' A phosphor represented by AX (where A is either HO or Dy, and 0.001≦X≦1 mole), SrSO4 described in JP-A-48-80489 : Ax (However, A is Dy, 'r
b and), and X is 0.001
4 x (excluding 1 mole), Na described in JP-A No. 51-29889;
Be09Li'F, a phosphor prepared by adding at least one of Ca5O, BaSO4, etc., to SO, lCa5O, and BaSO4, and at least one of DY and Tb, described in JP-A No. 52-30487.
MgS04 and car! Phosphors such as, JP-A-53-39
Li, B, O, :Cu described in No. 277,
Phosphors such as Ag, Li described in JP-A No. 54-47883, O. (B, O,) x : Cu (where X is 2<X≦3), and LixO.
: Cu, Ag (where X is a phosphor such as 2 (x≦3), s described in U.S. Patent No. 3.859.527)
rs: ('e, 8m% srs: Eu.

Sm % Lato, s: Eu, Sm and (Z
n, Cd) S: Mn, X (however, X is halogen)
Examples include phosphors represented by Also, JP1118
ZnS described in No. 55-12142: Cu
, pb phosphor, BaO x Al, o, :Eu(
However, 0.8! barium aluminate phosphor represented by z 41Q ) and yFo-xsxot:h<However,
l is Mg, Ca, Sr, Zn, Cd or Ba
And A is Ce, 'l'b.

Eu, Tm, Pb, TI, Bi and Mn
At least one rice among them, X is Q, 5 OtsuX, t
; 2.5. ) is an alkaline earth metal silicate ring type phosphor.

Also, (B”1-z-yMg)(Cay) FX
: eEu'' (However, X is at least one of Br and CI, and Xt'l and e are each Q (x+y≦
0.6, xy + 0, and a number that satisfies the following conditions: 10≦e≦5×10. ), an alkaline earth fluorohalide phosphor, LnOX described in JP-A-55-12144:
a, Y, Gd and Lu, X is C
I and/or Br, A &i Ce and/or Tb, and X represents a number satisfying O<X<0.1. ), described in JP-A-55-12145 (Ba, MI) FX: yA-x
X (where MI [ is Mg lca , Sr , Zn and cd), X is at least one of CI, Br and E, and A is Eu , Tb , ('e
, Tm ID)' IPr , Ho , Nd , Th
and Er, X and y are 0≦X
It represents a number that satisfies the conditions of ≦0.6 and 0≦y≦0.2. ), BaFX described in JP-A No. 55-84389:
, TI, Gd, sm and Zr.
, and X and y are each O〈X≦2
and 0<y≦5X10-"), M described in JP-A-55-160078
IFX ・xA: yLn (However, MI
+ Ca HBa + Sr + at least one of Zn and Cd, A is BeOHMg01 cao t
S rog BaO+ ZnOHA”*Os +Y
tOs, Lavas, IntOs-SfO*
, Ti1t, Zr0t, Ge0t.

5nOt l Nb2O2r Taxes and Th02
At least one of them, Ln is Eu, Tb, Ce
, Tm, Dy, Pr, Ho, Nd.

At least one of Yb, Er, 3m, and [Yes], X is at least one of CI, Br, and Eng, and X and y are each 5 X 105 ≦X≦
0.5 and O<y≦0.2.

) rare earth element-activated divalent metal fluorohalide phosphor, ZnS::A, CZn, Cd', ), S,
:A;, CdS, :A, Z'nS:A, X and C
dS: A, X (However, A is Cu.

Ag, Au or pigeon, and X is halogen. ), 2, xMs (PO4)t・NX, : yAMs (PO
a) t・yA (where M and N are respectively Mg lca , Sr ,
Ba.

At least one of Zn and Cd, and X is F or CI.

At least one of Br and E, A is Eu, Tb
.

Ce, Thin, Dy IPr, Ho, Nd, Er,
At least one of Sb, TI, Mn and Sn
Represents a species. Also, -X and y are 0 (x≦6, o≦y
This is a number that satisfies the condition of ≦1. ), generally nReX5 * mAX't ' xE”
'nReX, -mAX', : xEu, ysm
(In the formula, Re is La, Gd, Y, Lu (7) 61 kinds, A is alkaline earth metal B
at least one of a, Sr, ca, X and X'
represents at least one of F, CI, and Br.

, and X and y are 1xlO-4(x(3Xl0-1
% I X1O-4(y(I
The condition of X 10″″1 is satisfied. ), and MIX-aMI[X', ・bMNX'3:c
A (However, MI is Li, Na, K, Rh and C
s is at least one alkali metal selected from Be tMg , Ca , Sr , Ba
, Zn + Cd , Cu, and Ni. MI [is Sc, Y, La
, Ce , pr tNd, pm , 3m , Eu r
Gd + Tb + Dy t) (O + Er, Tm + Yb
, Lu + AI , Ga, and In. x, x' and X''are;F
, CI, Br, and at least one kind of halogen. A is Eu, Tb, ('e.

Tm +Dy, pr, Ho +Na, Th, E
r rGd, Lu, Sm, y.

It is at least one metal selected from Tl tNa +Ag +Cu and Pigeon. Further, a is a numerical value in the range of o=a<o, s, b is a numerical value in the range of O≦b(0,5), and C is a numerical value in the range of O(c≦0.2). ), etc. Alkali halide phosphors are particularly preferred when a stimulable phosphor layer is formed by a method such as vacuum evaporation or sputtering.

However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphors, but can be any phosphor that exhibits stimulable fluorescence when irradiated with radiation and then irradiated with stimulable excitation light. It may also be a phosphor.

The conversion panel used in the present invention may be a stimulable phosphor layer group consisting of one or more stimulable phosphor layers containing at least one kind of the above-mentioned stimulable phosphors. Furthermore, the stimulable phosphors contained in each stimulable phosphor layer may be the same or different.

The stimulable phosphor layer is formed by forming the stimulable phosphor into a layered portion that does not contain a binder by using a method such as vapor deposition or sputtering as described in Japanese Patent Application No. 196365/1983. It may be formed on a support, or it may be formed by dispersing the stimulable phosphor in a suitable binder to prepare a coating solution and coating it on the support. In the conversion panel of the present invention, when a binder is used, for example, a protein such as gelatin, a polysaccharide such as dextran or gum arabic, polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, [vinylidene dichloride-hinyl chloride polymer], Polymethyl methacrylate, hinyl chloride-vinyl acetate polymer, polyurethane, cellulose acetate butyrate,
Binders commonly used in layer construction are used, such as polyvinyl alcohol and the like.

However, for the conversion panel used in the present invention, it is preferable that the stimulable phosphor layer has a structure that does not contain a binder, as proposed in Japanese Patent Application No. 59-196365.

The layer thickness of the stimulable phosphor layer of the conversion panel used in the present invention varies depending on the radiation sensitivity of the intended conversion panel, the type of stimulable phosphor, etc., but it is 10μWL in the case of not containing a binder. -1000μm, more preferably 20μm-800μm, and when containing a binder, 10μrIL-10
00 μm range, more preferably 20 μm to 500 μm
O is preferably selected from the range of m. In the conversion panel used in the present invention, various polymeric materials, glass, metals, etc. are used as the support. In particular, materials that can be processed into flexible sheets or webs are suitable for handling as information recording materials, and from this point of view, for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. Preferred are plastic films such as films, metal sheets of aluminum, iron, copper, quam, etc., or metal sheets having a coating layer of the metal oxide.

In addition, the layer thickness of these supports varies depending on the material of the support used, but is generally 80μ? FL~1000μm
From the viewpoint of handling, more preferably 80μ
rrL~500 μm.

The surfaces of these supports may be smooth or matte for the purpose of improving adhesion to the stimulable phosphor layer. Further, the surface of the support may be an uneven surface, or may have a structure in which isolated micro tile-like plates are laid out.

Furthermore, these supports may be provided with a subbing layer on the surface on which the stimulable phosphor layer is provided for the purpose of improving adhesion to the stimulable phosphor layer.

Further, in the conversion panel used in the present invention, a stimulable phosphor layer as described in Japanese Patent Application No. 59-266912 is provided on the support surface for the purpose of improving the sharpness of the obtained radiation image. A structure with a fine columnar block structure extending almost perpendicular to the
A support having a large number of fine uneven patterns on its surface as described in No. 13, and a stimulable phosphor layer having a fine columnar block structure on which the surface structure is inherited as it is on the support. Structure with, patent application No. 59-266
914, a support having a surface structure in which a large number of micro tile-like plates are laid out and separated from each other by minute gaps, and a micro column-shaped support having the surface structure inherited as it is on the support. Professional.

A structure having a stimulable phosphor layer having a structure of A structure having a fine wire network and a stimulable phosphor layer having a fine columnar block structure of stimulable phosphor extending in the thickness direction on the micro tile-like plate, Japanese Patent Application No. 59-266916
Distributed in large numbers on the surface of the support as described in the issue, and also with gaps? The stimulable phosphor layer deposited in the thickness direction from the surfaces of the micro tiles that are separated from each other is subjected to a coating treatment, thereby depositing the stimulable phosphor layer from the gaps between the micro tiles toward the layer surface. It may also be a structure in which a stimulable phosphor layer having a fine columnar block structure with developed flares is provided.

Furthermore, for the purpose of improving the sharpness of radiation images obtained in the conversion panel used in the present invention, white powder may be contained in the stimulable phosphor layer, or the stimulable phosphor layer may be stimulable. It may be colored with a coloring agent that absorbs excitation light. Alternatively, a light reflecting layer containing a white pigment may be provided between the support and the stimulable phosphor layer.

The photodetector for detecting the afterglow of the stimulable phosphor uses a single 7'-optometer (photomultiplier tube) with a light guide such as an acrylic sheet or optical fiber bundle used during reading. Alternatively, it is also possible to use a seven-dimensional array or a plurality of phototransistors arranged in the main scanning direction. Further, the photodetectors may be arranged in a matrix to detect the light emitted from each part of the conversion panel used in the present invention. In this case, the number of photodetectors may be sufficient to detect the characteristics of the image, for example, one photodetector per 1cI7IL-25CI11 of image area.

Stimulating excitation light sources that can be used in the present invention include Ar'' laser, He-Cd laser, He4e laser, Kr laser)
There are lamps such as ye lasers, YAG lasers, COt lasers, semiconductor lasers, L]lIDs, and tungsten lamps, but lasers and LEDs are particularly preferable because they are excellent in terms of light convergence and light intensity.

The present invention will be explained below based on the drawings.

FIG. 2 is a schematic diagram of a radiation image reading device that is an embodiment of the present invention. In this embodiment, the radiation emitted from the radiation source 201 toward the subject 202
After passing through, the radiation is absorbed by the conversion panel 203, and a radiation image of the subject is stored and recorded.

At a position facing the surface of the conversion panel 203 facing the stimulable phosphor 204, there is an excitation light source 205 that emits excitation light, such as a laser beam, and an excitation light source 205 that emits excitation light such as a laser beam, and the excitation light emitted from this excitation light source is scanned in the width direction of the conversion panel 203. For example, a light polarizer 206 such as a carbacmeter mirror, a photodetector 207 that reads the stimulated luminescent light emitted by the photostimulable phosphor 204 excited by the excitation light, and a photodetector 207 that guides the stimulated luminescent light to the photodetector 207. A light transmission means 208 is provided on a common transport stage 209.

The photodetector 207 is, for example, a photomultiplier tube, a channel plate for photoelectron amplification, or the like, and photoelectrically detects the stimulated luminescence light guided by the light transmission means 208.

Further, an erasing light source 210 is provided at a position facing the phosphor side surface of the conversion panel 203, and is transported together with the transport stage in the direction of the arrow in the figure. The above erasing light source 21
0 is a light source that emits light including the excitation wavelength range of the stimulable phosphor 204, and is disclosed in, for example, Japanese Patent Laid-Open No. 56-1139.
A halogen lamp, a tungsten lamp, an infrared lamp, an LED, a laser light source, etc. as shown in No. 2 can be arbitrarily selected and used.

The operation of the apparatus of this embodiment having the above structure will be explained below. After the subject 202 is placed between the conversion panel 203 and the radiation source 201, when the radiation source 201 is turned on, a transmitted radiation image of the subject 202 is recorded and accumulated on the stimulable phosphor 204 of the conversion panel 203. . After this,
Afterglow emitted by the stimulable phosphor 204 is detected by the photodetector 207 via the light transmission means 208 by turning on the switch of the photodetector 207 . At this time, the conveyance stage 209 is sub-scanned from above to below to detect the afterglow of the entire panel 203. This time-series afterglow electrical signal is transmitted to an amplifier,
After being amplified in step 211, it is sent to maximum and minimum value discrimination means 212, where the maximum and minimum brightness on the image is discriminated.

As mentioned above, the amount of afterglow is exactly proportional to the amount of energy stored in the stimulable phosphor. (depending on the structure of the device, reading time, etc.) can be automatically converted into the maximum and minimum values of energy storage. This conversion operation is performed by the conversion means 213 and the result is stored in the storage means '2.14. remembered by.

FIG. 3 shows a schematic diagram of a radiation image reading device which is another embodiment of the present invention. From radiation source 301 to subject 3
After the radiation irradiated toward 02 passes through the subject 302, it is absorbed by the conversion panel 303, and a radiation image of the subject is recorded and accumulated. Then the phosphor side 30 of the conversion panel
Afterglow emitted by the stimulable phosphor is detected by a photodetector 305 arranged at 4.

As the photodetector 305, a photomultiplier tube, a silicon detector, a solar cell, etc. can be used in a two-dimensional arrangement.

The output of the photodetector 305 is amplified by an amplifier 306 and then sent to maximum/minimum value discriminating means 307, where the maximum/minimum value on the image is discriminated. The amount of afterglow light is automatically converted into the maximum value and minimum value of energy by the conversion means 308 in the same manner as described in FIG. 2 above, and the results are stored in the storage means 309.

After the afterglow of the conversion panel is read by the method shown in FIGS. 2 and 3, the panel is scanned by the above-mentioned stimulated excitation light source, preferably a laser beam.

Taking FIG. 4 as an example, stimulated luminescence emitted by laser beam scanning passes through a light transmission means 406 to a photodetector 40.
Detected by 7. Sub-scanning is performed on a conveyance stage 408, and the image recording portion of the conversion panel 401 is illuminated with a laser beam 40.
Scan by 9. At this time, it is not necessarily necessary to scan the entire surface of the panel. After the necessary image part is read,
It is erased by the disappearing light source 405. At this time, the light transmission means 4
In front of 06, a shutter 4'IO may be provided to prevent the erasing light from entering the photodetector.

The radiation image signal converted into an electric signal by the photodetector 407 is amplified by the amplifier circuit 411, and the control circuit 412
It is displayed on the CRT 413 after being modulated by. Alternatively, the illumination of the light source 414 for obtaining the hard copy 415 may be controlled.

At this time, when the signal amplified by the amplifier circuit 411 is recorded on an octocopy, the control circuit 412 controls the light source 414 to a brightness that provides the optimum density range.
When displaying on T413, the display is controlled to be in the optimum brightness range for easy viewing.

This control is performed, for example, by setting the maximum and minimum values of the radiation energy storage amount determined from the afterglow stored in the storage means 214.309 in the optimum density range on the hard copy or the optimum brightness range on the CRT. This can be done by making them correspond to the maximum value and minimum value, respectively, and assuming that there is a linear relationship between them.

Next, the influence of afterglow will be explained with reference to FIGS. 5 and 6.

Figure 5 shows the relationship between irradiated X-ray dose and afterglow after X-ray irradiation.
This is after seconds, 10 seconds, and 15 seconds have elapsed.

From FIG. 5, it can be seen that the relationship between the irradiated X-ray dose and the amount of afterglow is a linear relationship. It can also be seen that by detecting this afterglow, it is possible to set a reading start time that is not affected by the afterglow.

Figure 6 shows the relationship between irradiation xsm and the amount of stimulated luminescence.
From this figure, it can be seen that there is a linear relationship between the irradiated X-ray dose and the stimulated luminescence amount. Therefore, it can be seen that the amount of energy accumulated in the conversion panel can be measured by detecting the amount of afterglow.

〔Effect of the invention〕

By clarifying the direct proportional relationship between the afterglow generated in a stimulable phosphor by radiation irradiation and the state quantity of the radiation image recorded and accumulated in the stimulable phosphor, we will be able to realize long-term vision that was previously unnecessary. This opens the door to the use of afterglow as a useful means of converting it into high-quality and purposeful radiographic images.

[Brief explanation of drawings]

FIG. 1 is a time-series explanatory diagram of a luminescent phenomenon of a phosphor, and FIGS. 2 and 3 are schematic diagrams of a radiation image reading apparatus according to the present invention, respectively. FIG. 4 is an explanatory diagram of the mechanism of the present invention. FIG. 5 is a diagram showing the relationship between the irradiation x weight and the amount of afterglow generation, and FIG. 6 is a diagram showing the relationship between the amount of stimulated luminescence. 201 and 301... Radiation sources 202 and 30
2... Subject 203, 303 and 401... Conversion panel 20
7, 305 and 407... photodetector 211.
306 and 411...Amplifiers 212 and 307
...Maximum and minimum discrimination means 214 and 309...
...Storage means applicant: Konishi Rokushako Kogyo Co., Ltd.

Claims (1)

[Claims] In a radiation image reading method of reading an image from a stimulable phosphor irradiated with radiation in an imagewise manner, an afterglow emitted by the stimulable phosphor after irradiation with radiation is detected to obtain information regarding the characteristics of the radiation image. . A radiation image reading method, characterized in that, in the step of reading the radiation image from the stimulable phosphor, a conversion is applied to the read signal based on the information.