JPH06130199A - Radiation image conversion panel and radiation image recording and reproducing method - Google Patents

Abstract

PURPOSE:To obtain a new radiation image conversion panel and enable recording and reproducing of the radiation image by using a fluorescent body including alkali metal element having a specific composition, rare-earth element and fluorine. CONSTITUTION:A fluorescent body expressed by M<1>Ln3 F10:aAc is used (where M<1> is at least a kind of alkali metal element selected among a group of Li, Na, K, Pb and Cs; Ln is at least a kinds of rare-earth element selected among a group of Y, La, Gd, Yb and Lu; and Ac is at least a kinds of rare-earth metal selected among a group of Eu, Ce and Tb; and <a> is a value in the rage of 0<0.2). The radiation generated 11 from a subject 12 goes in a radiation image panel 13 and absorbed in stimulation luminescence layers in the panel 13. When electromagnetic wave in the wave length range of 450 to 800mm is irradiated to the panel 13 using the light source 14, the cumulative image of the radiation energy is radiated as accelerated luminescence. This image information is photoelectro converted 15 and the image is reproduced 16 and displayed 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion panel and a radiation image recording / reproducing method using a phosphor containing an alkali metal element, a rare earth element and fluorine.

[0002]

2. Description of the Related Art Conventionally, a so-called radiographic method has been used as a method for obtaining a radiographic image as an image by using a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen (intensifying screen). Is used.

On the other hand, in recent years, as one of the methods to replace the above radiographic method, a radiation image conversion utilizing a stimulable phosphor as described in JP-A-55-12145 and the like. A method (radiation image recording / reproducing method) was developed,
Has received attention. This method involves absorbing and accumulating radiation transmitted through a subject or radiation emitted from a subject in a stimulable phosphor, and then exciting this phosphor with electromagnetic waves (excitation light) such as visible light and infrared light. By
Radiation energy accumulated in a phosphor is emitted as fluorescence (stimulated luminescence), the fluorescence is photoelectrically read to obtain an electric signal, and the electric signal is visualized.

According to the above radiation image recording / reproducing method,
Compared with the case of using the conventional radiography, there is an advantage that a radiographic image having a large amount of information can be obtained with a much smaller exposure dose. Therefore, this radiographic image recording / reproducing method is very useful particularly in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

In the above-mentioned radiation image recording / reproducing method, a stimulable phosphor that emits light (stimulated luminescence) by being irradiated with radiation such as X-ray and then excited by electromagnetic waves in the visible to infrared region is used. As such a stimulable phosphor, conventionally, a divalent europium-activated alkaline earth metal fluorohalide phosphor (M ^II FX: Eu ²⁺ ; where M ^II is Mg, C
a and Ba and at least one alkaline earth metal selected from the group consisting of a and Ba, X is at least one halogen selected from the group consisting of Cl, Br and I); europium and samarium activated strontium sulfide phosphor (SrS : Eu, Sm); Europium and samarium activated lanthanum oxysulfide phosphor (La ₂
O ₂ S: Eu, Sm); Europium-activated aluminum barium oxide phosphor (BaO.Al ₂ O ₃ : Eu); Europium-activated alkaline earth metal silicate phosphor (M ²⁺
O.SiO ₂ : Eu; provided that M ²⁺ is Mg, Ca and B
at least one alkaline earth metal selected from the group consisting of a); cerium-activated rare earth oxyhalide phosphor (LnOX: Ce; where Ln is La, Y,
It is known that at least one rare earth element selected from the group consisting of Gd and Lu, and X is at least one halogen selected from the group consisting of Cl, Br, and I).

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation image conversion panel and a radiation image recording / reproducing method using a novel photostimulable phosphor.

[0007]

Means for Solving the Problems The present inventor has searched for a stimulable phosphor, and as a result, a phosphor containing an alkali metal element, a rare earth element and fluorine having a specific composition is stimulated to emit light. The present invention has been newly found to exhibit

A radiation image conversion panel comprising a support and a stimulable phosphor layer provided on one surface of the support, wherein the stimulable phosphor layer has the following composition formula: (I): M ^I Ln ₃ F ₁₀ : aAc (I) (where M ^I is at least one alkali metal element selected from the group consisting of Li, Na, K, Rb and Cs; Ln is Y, At least one rare earth element selected from the group consisting of La, Gd, Yb and Lu; Ac
Is at least one rare earth element selected from the group consisting of Eu, Ce and Tb; and a is 0 <a ≦ 0.2
The radiation image conversion panel is characterized by containing a phosphor represented by a numerical value in the range.

Radiation transmitted through a subject or emitted from a subject is absorbed and accumulated in the phosphor represented by the above composition formula (I), and then 450 to 800 is applied to the phosphor.
The radiation energy accumulated in the phosphor is emitted as stimulated light by irradiating an electromagnetic wave in the wavelength region of nm (preferably 500 to 700 nm), and this stimulated light is detected. Radiation image recording / reproducing method.

Among the phosphors belonging to the phosphor represented by the composition formula (I), M ^I is rubidium (Rb), Ln is gadolinium (Gd), and Ac is europium (Eu).
The fluorescent substance of Mat. Res. Bull. Vol. 1
8, pp. 135-140, 1983 (Pergamo
n Press, Inc. , USA), but this document only reports the results of studies on the emission mechanism of the phosphor, and there is no suggestion that this phosphor exhibits stimulability.

The radiation image storage panel of the present invention is characterized by the fact that the phosphor of the above composition formula (I) is newly stimulable, and therefore it is used as a stimulable phosphor. is there.

M ^I Ln ₃ F ₁₀ : aAc (I) The phosphor of the above composition formula (I) is similar to the usual phosphors:
A raw material compound (for example, a halide of an alkali metal and a halide of each of two types of rare earth elements) is mixed, and then the mixture is baked at a temperature of about 700 to 1000 ° C. under an inert gas atmosphere to produce the mixture. You can The phosphor can be subjected to known treatments such as crushing treatment, sieving treatment and washing treatment, if necessary.

The radiation image conversion panel of the present invention generally comprises a support and a stimulable phosphor layer comprising a binder which is provided on the support and contains the stimulable phosphor in a dispersed state. Composed. However, the stimulable phosphor layer may be composed of only phosphor particles, or a sintered body of phosphor or a vapor deposition layer, and a binder is not always necessary.

The most general radiation image conversion panel can be manufactured, for example, by the method described below. First, the stimulable phosphor particles and the binder are added to an appropriate solvent (for example, lower alcohol, chlorine atom-containing hydrocarbon, ketone, ester, ether), and they are thoroughly mixed to prepare a binder solution. A coating liquid in which the stimulable phosphor is uniformly dispersed is prepared. Examples of the binding agent include binding agents represented by proteins such as gelatin, polyvinyl acetate, nitrocellulose, polyurethane, polyvinyl alcohol, polyalkyl (meth) acrylate, and synthetic polymer substances such as linear polyester. be able to. The mixing ratio of the binder and the stimulable phosphor in the coating liquid is usually selected from the range of 1: 8 to 1:40 (weight ratio).

Next, the coating solution is uniformly coated on the surface of the support to form a coating film of the coating solution, and then the coating film is dried to form a stimulable phosphor layer on the support. Complete the formation of. The layer thickness of the stimulable phosphor layer is generally 50 to 50.
It is 0 μm. The support can be appropriately selected from various materials used as a support for an intensifying screen (or intensifying screen) in a conventional radiographic method or a support for a known radiation image conversion panel. Examples of such materials include films of plastic substances such as cellulose acetate, polyethylene terephthalate,
Examples include metal sheets such as aluminum foil, ordinary paper, baryta paper, and resin-coated paper. In addition,
An adhesiveness-imparting layer, a light-reflecting layer, a light-absorbing layer or the like may be provided on the surface of the support on which the phosphor layer is provided, and the support is provided with fine irregularities uniformly. (If the adhesion-providing layer, the light-reflecting layer, the light-absorbing layer, etc. are provided on the surface of the support on the side of the phosphor layer, these irregularities are formed on the surface).

A transparent protective film for physically and chemically protecting the phosphor layer may be provided on the surface of the stimulable phosphor layer opposite to the side in contact with the support. Examples of materials used for the transparent protective film include cellulose acetate,
Examples thereof include polymethylmethacrylate, polyethylene terephthalate, and polyethylene. The thickness of the transparent protective film is usually about 0.1 to 20 μm.

A radiation image conversion panel using the phosphor of the present invention is colored with a colorant as described in JP-A-55-163500, JP-A-57-96300 and the like. Also, see JP-A-55-14
White powder may be dispersed in the stimulable phosphor layer as described in Japanese Patent No. 6447.

When the radiation image recording / reproducing method of the present invention is used in the form in which the phosphor represented by the above composition formula (I) is contained in the radiation image conversion panel, the schematic diagram shown in FIG. 1 is used. It will be specifically described.

In FIG. 1, 11 is a generator of radiation such as X-rays, 12 is a subject, 13 is a radiation image conversion panel containing a phosphor, and 14 is an accumulated image of radiation energy on the radiation image conversion panel 13. An excitation source (light source) for emitting light as light, 15 is a photoelectric conversion device that detects photostimulated light emitted from the radiation image conversion panel 13, and 16 is an electric signal detected by the photoelectric conversion device 15 that is reproduced as an image. Device, 17 is a device for displaying the reproduced image, and 18
Is a filter for transmitting only the stimulated light emitted from the radiation image conversion panel 13 without transmitting the reflected light from the light source 14.

Although FIG. 1 shows an example of obtaining a radiation transmission image of a subject, when the subject 12 itself emits radiation (this is referred to as a subject in the present specification), It is not necessary to specifically install the radiation generator 11 of. In addition, the photoelectric conversion device 15 and the image reproduction device 1
6 and the image display device 17 may be replaced with other suitable devices capable of visualizing and reproducing the image information emitted from the radiation image conversion panel 13 as stimulating light in some way.

As shown in FIG. 1, when the subject 12 is irradiated with radiation such as X-rays from the radiation generator 11, the radiation passes through the subject 12 in proportion to the radiation transmittance of each part thereof. The radiation transmitted through the subject 12 is
The radiation enters the radiation image conversion panel 13 and is absorbed by the photostimulable layer of the radiation image conversion panel 13 in proportion to the intensity of the radiation. That is, an accumulated image of radiation energy (a kind of latent image) corresponding to a radiation transmission image is formed on the radiation image conversion panel 13.

Next, the light source 1 is attached to the radiation image conversion panel 13.
When the electromagnetic wave in the wavelength region of 450 to 800 nm is irradiated using the No. 4, the accumulated image of the radiation energy formed on the radiation image conversion panel 13 is emitted as stimulating light. The emitted photostimulable light is proportional to the intensity of the radiation energy absorbed in the photostimulant layer of the radiation image conversion panel 13. The image information composed of the intensity of the stimulated emission is converted into an electric signal by the photoelectric conversion device 15 such as a photomultiplier tube, reproduced as an image by the image reproduction device 16, and the image is displayed by the image display device 17. Is displayed.

The operation of reading the image information accumulated in the radiation image conversion panel as stimulable light is generally performed by scanning the panel in a time series with a laser beam, and the stimulable light emitted from the panel by this scanning is appropriately collected. It is carried out by detecting with a photodetector such as a photomultiplier tube through the optical body to obtain a time-series electric signal. This read-out may be composed of a pre-reading operation by irradiating low-energy excitation light and a main reading operation by irradiating high-energy excitation light in order to obtain an image having a better observation / interpretation performance (JP-A-58). -67
No. 240). By performing this pre-read operation, there is an advantage that the read condition in the main read operation can be set appropriately.

A solid-state photoelectric conversion element such as a photoconductor and a photodiode can be used as the photoelectric conversion device (see Japanese Patent Laid-Open No. 58-121874). In this case, a large number of solid-state photoelectric conversion elements are configured so as to cover the entire surface of the panel and may be integrated with the panel, or may be arranged in the state of being close to the panel. Further, the photoelectric conversion device may be a line sensor in which a plurality of photoelectric conversion elements are linearly connected, or may be composed of one solid-state photoelectric conversion element corresponding to one pixel.

In the above case, the light source may be a point light source such as a laser, or a line light source such as an array in which light emitting diodes (LEDs) or semiconductor lasers are connected in a row. By performing reading using such a device, it is possible to prevent the loss of photostimulated light emitted from the panel, and at the same time increase the light receiving solid angle to increase the S / N ratio. Further, the obtained electric signal is not time-sequentially irradiated with the excitation light but is time-sequentially processed by the electric processing of the photodetector, so that the reading speed can be increased.

The radiation image conversion panel from which the image information has been read out is irradiated with light in the wavelength region of the excitation light of the photostimulant or is heated.
The remaining radiation energy may be erased, and it is preferable to do so (see JP-A-56-11392 and JP-A-56-12599). By performing this erasing operation, it is possible to prevent generation of noise due to an afterimage when the panel is used next time. Further, by performing the erasing operation twice after the reading and immediately before the next use, it is possible to prevent the generation of noise due to natural radioactivity and perform the erasing more efficiently (see JP-A-57-116300). ).

In the radiation image recording / reproducing method of the present invention, as the radiation used for obtaining a radiation transmission image of the subject, a stimulable phosphor is excited by the electromagnetic wave after being irradiated with this radiation. Any radiation may be used as long as it can exhibit stimulated emission, and commonly known radiation such as X-rays, electron beams, and ultraviolet rays can be used. Further, the radiation emitted directly from the subject in the case of obtaining a radiation image of the subject may be any radiation as long as it is absorbed by the stimulable phosphor and becomes an energy source of stimulated luminescence. As an example thereof, radiation such as γ-ray, α-ray, β-ray and the like can be mentioned.

As a light source of excitation light for exciting the stimulable phosphor that has absorbed radiation from a subject or a subject, in addition to a light source that emits light having a band spectrum distribution in the wavelength region of 450 to 800 nm, For example, a laser such as an Ar ion laser, a Kr ion laser, a He-Ne laser, a ruby laser, a semiconductor laser, a glass laser and a dye laser, and a light source such as a light emitting diode can also be used. Among them, the laser can irradiate the radiation image conversion panel with a laser beam having a high energy density per unit area,
Various lasers are preferable as the excitation light source used in the present invention. Among them, the He—Ne laser is particularly preferable in terms of matching with the stimulable excitation spectrum of the stimulable phosphor of the present invention. In addition, the semiconductor laser has a small size and a small driving power,
It is preferable as a light source for excitation because it can be directly modulated and the laser output can be easily stabilized.

The light source used for erasing may be any one that emits light in the excitation wavelength region of the stimulable phosphor, and examples thereof include a tungsten lamp, a stimulant lamp,
Mention may be made of halogen lamps.

The radiation image recording / reproducing method of the present invention comprises a storage part for absorbing and accumulating radiation energy in the stimulable phosphor, and irradiating the stimulable phosphor with excitation light to stimulate the radiation energy. A light detection (reading) unit that emits as
Also, it can be applied to a built-in type radiation image conversion device in which an erasing unit for releasing the energy remaining in the stimulable phosphor is built in one device.

[0031]

【Example】

[Example _{1] RbGd 3 F 10: 0.01Ce} 3+ manufacturing rubidium fluoride (RbF) 1.63 g, gadolinium fluoride (GdF ₃₎ 10g, and cerium fluoride (C
eF ₃₎ was a 0.03g dry mixed. Next, the obtained mixture was filled in an alumina crucible and placed in a high temperature electric furnace for firing. Firing is 850 in a nitrogen atmosphere
It was carried out at a temperature of ° C for 2 hours. After firing was completed, the fired product was taken out of the furnace, cooled, loosened, and washed with methanol. In this way, the powdery phosphor (R
bGd ₃ F ₁₀ : 0.01Ce ³⁺ ) was obtained.

Next, the stimulated excitation spectrum and stimulated emission spectrum of the phosphor produced as described above were measured. The obtained stimulated excitation spectrum is shown in FIG. 2 and the stimulated emission spectrum is shown in FIG.

Example 2 Production of Radiation Image Conversion Panel 600 g of the powdered phosphor obtained in Example 1 and a polyurethane resin (manufactured by Sumitomo Bayer Urethane Co., Desmolac 42)
15) 15.8 g and 2.0 g of bisphenol A type epoxy resin are added to methyl ethyl ketone-toluene (1: 1).
It was added to the mixed solvent and dispersed by a propeller mixer to prepare a coating liquid having a viscosity of 20 to 30 PS. This coating solution was applied onto a polyethylene terephthalate sheet support with an undercoat layer using a doctor blade, and then at 100 ° C. for 1 hour.
It was dried for 5 minutes to form a stimulable phosphor layer. Next, a polyethylene terephthalate film with an adhesive layer (thickness:
10 μm) was adhered onto the stimulable phosphor layer to form a transparent protective film, and a radiation conversion panel composed of the support, the stimulable phosphor layer and the transparent protective film was produced.

[Example 3] RbLa ₃ F ₁₀ : 0.01C
Production of e ^{3+ As} a raw material compound, rubidium fluoride (RbF) 1.7 was used.
The same procedure as in Example 1 was performed except that 8 g, lanthanum fluoride (LaF ₃ ) 10 g, and cerium fluoride (CeF ₃ ) 0.033 g were used, and the powdery phosphor (RbLa ₃
F _10: 0.01Ce ³⁺⁾ was obtained. Next, the stimulated excitation spectrum and stimulated emission spectrum of the phosphor manufactured as described above were measured. The obtained stimulated emission spectrum is shown in FIG. The stimulated excitation spectrum was substantially the same as in FIG.

Example 4 RbYb ₃ F ₁₀ : 0.01E
Production of u ^{3+ As} a raw material compound, rubidium fluoride (RbF) 1.5
1 g, ytterbium fluoride (YbF ₃ ) 10 g, and europium fluoride (EuF ₃ ) 0.030 g were used, but the same procedure as in Example 1 was performed to obtain a powdery phosphor (RbYb ₃ F ₁₀ : 0.01Eu ^{3). +} ) Got. Next, the stimulated excitation spectrum and stimulated emission spectrum of the phosphor manufactured as described above were measured. The obtained stimulated emission spectrum is shown in FIG. Figure 2 shows the stimulated excitation spectrum.
Was substantially the same as.

[Example 5] NaGd ₃ F ₁₀ : 0.01E
Production of u ^{3+ As} raw material compound, sodium fluoride (NaF) 0.6
5 g, gadolinium fluoride (GdF ₃ ) 10 g, and europium fluoride (EuF ₃ ) 0.033 g were used in the same manner as in Example 1 except that powdered phosphor (N
aGd ₃ F ₁₀ : 0.01Eu ³⁺ ) was obtained. Next, the stimulated excitation spectrum and stimulated emission spectrum of the phosphor manufactured as described above were measured. The obtained stimulated emission spectrum is shown in FIG. The stimulated excitation spectrum was substantially the same as in FIG.

[Example 6] Measurement of stimulated luminescence amount The stimulated luminescence amount measured for various phosphors of the present invention according to the composition formula (I) manufactured by the same method is shown in Table 1 as a relative value. . The numerical values shown in Table 1 are the emission amounts of photostimulable photoluminescence generated when each phosphor powder was irradiated with X-rays at a tube voltage of 80 KVp and then excited with He-Ne laser light (633 nm), RbLa ₃ F ₁₀ : 0. The emission amount of 0.01 Ce ³⁺ is set to 10
It is a relative value converted as 0.

Table 1 ──────────────────────────────────── Fluorescent substance Relative stimulated emission amount ─ ─────────────────────────────────── LiLa ₃ F ₁₀ : 0.01Ce ³⁺ 50 LiLa ₃ F ₁₀ : 0.01Eu ³⁺ 52 NaLa ₃ F ₁₀ : 0.01Ce ³⁺ 43 NaLa ₃ F ₁₀ : 0.01Eu ³⁺ 35 KLa ₃ F ₁₀ : 0.01Ce ³⁺ 30 KLa ₃ F ₁₀ : 0.01Eu ³⁺ 29 RbLa ₃ F ₁₀ : 0.01Ce ³⁺ 100 RbLa ₃ F ₁₀ : 0.01Eu ³⁺ 39 CsLa ₃ F ₁₀ : 0.01Ce ³⁺ 24 CsLa ₃ F ₁₀ : 0.01Eu ³⁺ 34 LiGd ₃ F ₁₀ : 0.01Ce ³⁺ 48 LiGd ₃ F ₁₀ : 0.01Eu ³⁺ 41 NaLa ₃ F ₁₀ : 0.01Ce ³⁺ 37 NaGd ₃ F ₁₀ : 0.01Eu ³⁺ 26 KGd ₃ F ₁₀ : 0.01Ce ³⁺ 72 KGd ₃ F ₁₀ : 0.01Eu ³⁺ 51 RbGd ₃ F ₁₀ : 0.01Ce ³⁺ 39 RbGd ₃ F ₁₀ : 0.01Eu ³⁺ 62 CsGd ₃ F ₁₀ : 0.01Ce ³⁺ 61 CsGd ₃ F ₁₀ : 0.01Eu ³⁺ 57 LiYb ₃ F ₁₀ : 0.01Ce ³⁺ 29 LiYb ₃ F ₁₀ : 0.01Eu ³⁺ 52 NaYb ₃ F ₁₀ : 0.01Ce ³⁺ 25 NaYb ₃ F ₁₀ : 0.01Eu ³⁺ 38 KYb ₃ F ₁₀ : 0.01Ce ³⁺ 30 KYb ₃ F ₁₀ : 0.01Eu ³⁺ 31 RbYb ₃ F ₁₀ : 0.01Ce ³⁺ 24 RbYb ₃ F ₁₀ : 0.01Eu ³⁺ 36 CsYb ₃ F ₁₀ : 0.01Ce ³⁺ 23 CsYb ₃ F ₁₀ : 0.01Eu ³⁺ 39 ────────────────── ────────────────────

[0039]

Although some of the phosphors used in the present invention are already known, they are novel as stimulable phosphors, and are useful in a radiation image recording / reproducing method and the method thereof. It can be advantageously used for the radiation image conversion panel used.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a radiation image recording / reproducing method of the present invention.

FIG. 2 is a stimulated excitation spectrum of RbGd ₃ F ₁₀ : 0.01Ce ³⁺ .

FIG. 3 is a stimulated emission spectrum of RbGd ₃ F ₁₀ : 0.01Ce ³⁺ .

FIG. 4 is a stimulated emission spectrum of RbLa ₃ F ₁₀ : 0.01Ce ³⁺ .

FIG. 5: Photostimulated emission spectrum of RbYb ₃ F ₁₀ : 0.01Eu ³⁺ .

FIG. 6 is a stimulated emission spectrum of NaGd ₃ F ₁₀ : 0.01Eu ³⁺ .

[Explanation of symbols]

 11 Radiation Generation Device 12 Subject 13 Radiation Image Conversion Panel 14 Light Source 15 Photoelectric Conversion Device 16 Image Reproduction Device 17 Image Display Device 18 Filter

Claims (2)

[Claims] 1. A radiation image conversion panel comprising a support and a stimulable phosphor layer provided on one surface of the support,
As a stimulable phosphor in the stimulable phosphor layer, the following composition formula (I): M ^I Ln ₃ F ₁₀ : aAc (I) (wherein M ^I is Li, Na, K, Rb and Cs) Ac is at least one alkali metal element selected from the group; Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, Yb and Lu; Ac
Is at least one rare earth element selected from the group consisting of Eu, Ce and Tb; and a is 0 <a ≦ 0.2
The radiation image conversion panel is characterized by containing a phosphor represented by a numerical value in the range. 2. Radiation transmitted through a subject or emitted from a subject is expressed by the following composition formula (I): M ^I Ln ₃ F ₁₀ : aAc (I) (where M ^I is Li, Na, Ac is at least one alkali metal element selected from the group consisting of K, Rb and Cs; Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, Yb and Lu; Ac
Is at least one rare earth element selected from the group consisting of Eu, Ce and Tb; and a is 0 <a ≦ 0.2
The radiation energy stored in the phosphor is brightened by irradiating the phosphor with an electromagnetic wave in the wavelength region of 450 to 800 nm. Radiation image recording characterized by emitting as stimulus and detecting this stimulus
How to play.