JP2003140281A - Radiation image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image reader which improves the picture quality of a radiation image by effectively removing scattered rays. SOLUTION: The radiation image reader 10 is constituted of a base plate, a stimulated phosphorescent sheet 19 which is arranged on the opposite side of the base plate from a radiation irradiation side, and a read means which reads stimulated phosphorescence emitted by the stimulated phosphorescent sheet 19; and the base plate is formed of a grid 12 and the reader is equipped with the grid 12 and stimulated phosphorescent sheet 19 in contact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image reading device, and more particularly to a radiation image reading device used in a radiation image information recording / reproducing system using a stimulable phosphor sheet.

[0002]

2. Description of the Related Art Conventionally, a radiation image represented by an X-ray image has been widely used for disease diagnosis and the like. As a method for obtaining this radiographic image, the radiation transmitted through the subject is applied to a phosphor layer called an intensifying screen, and the visible light emitted from the phosphor layer is irradiated with visible light of the silver halide photographic material (hereinafter, A so-called radiographic method has been proposed and put into practical use, in which a visible image is obtained by irradiating a "photosensitive material") and developing the photosensitive material.

In recent years, in place of the above-mentioned radiographic method, the irradiated radiation energy is stored and recorded, and when excitation light is irradiated, it is stimulated to emit light according to the stored and recorded radiation energy. A radiation image recording / reproducing system using a "fluorescent substance" has been proposed. This method
By irradiating the sheet-shaped photostimulable phosphor with the radiation that has passed through the subject, radiation energy (hereinafter referred to as "image information") corresponding to the radiation transmission density of each part of the subject is accumulated in the photostimulable phosphor. After recording, the image information accumulated and stored in the stimulable phosphor by excitation light is emitted as stimulated emission light, and the intensity of this stimulated emission light is converted into an electric signal to form an image of a photosensitive material or the like. The image is reproduced as a visible image through an image display device such as a recording material or a CRT.

The sheet-shaped stimulable phosphor (hereinafter referred to as "stimulable phosphor sheet") 100 is fixed to a predetermined supporting plate 110 as shown in FIG.
It is often placed inside and used for radiographic imaging.
After the radiographic image capturing is completed, the radiographic image reading means (hereinafter referred to as “reading means”) provided in the housing 120.
The image information accumulated in the stimulable phosphor is read by 130. A radiographic image capturing apparatus including such a reading unit 130 is referred to as a “radiation image reading apparatus”.

As shown in FIG. 8, as the reading means 130, one arranged on the back surface side (the side opposite to the radiation source side) of the stimulable phosphor sheet 100 has been proposed and put into practical use. . The reading unit includes an excitation light source 131, a light guide unit 132, and a photoelectric conversion unit 133.
Photostimulable phosphor sheet 10 by excitation light irradiated from 1
The image information stored in 0 is emitted from the back side as stimulated emission light, and this stimulated emission light is guided to the photoelectric conversion means 133 via the light guide means 132 to be converted into an electric signal. This electric signal is transmitted to an image processing means (not shown), subjected to image processing, and then visualized.

[0006]

A radiation image reading apparatus having a reading means 130 for reading the stimulated emission light emitted from the back surface side (the side opposite to the radiation source side) of such a stimulable phosphor sheet 100. When using, there were the following problems.

That is, on the radiation source 200 side of the stimulable phosphor sheet 100, as shown in FIG.
The subject 300 and the front plate 1 of the housing 120 (in order from the 00 side)
21 and the support plate 110 exist, the stimulable phosphor sheet 100 also accumulates low-energy radiation (scattered rays) scattered when passing through these. If the accumulation of accurate image information is hindered by such scattered rays, various adverse effects such as deterioration of diagnostic performance may occur.

In particular, when the subject 300 is placed above such a radiographic image reading apparatus to perform radiography (that is, when the radiographing is performed in the "prone position"), the subject 3
00 and the front plate 121 of the housing 120, the subject 30
It is necessary to provide a top plate 400 that supports a weight of 0 (Fig. 1
Therefore, the adverse effect of scattered radiation on the radiation image was even greater.

As means for removing such scattered radiation, conventionally, a radiation absorbing layer made of lead or the like having a high radiation absorptivity, and aluminum, paper, or a like having a low radiation absorptivity,
A "grid" is used in which a laminated body in which radiation transmitting layers made of wood, synthetic resin, etc. are alternately provided is covered with a cover member having a low radiation absorption rate, and this grid is used as a stimulable phosphor. The scattered rays were removed by disposing the sheet 100 at a position closer to the subject 300 than the sheet 100.

However, the members that make up this grid,
Radiation may also be scattered by the grid itself, which may prevent accurate accumulation and recording of image information reaching the stimulable phosphor sheet.

An object of the present invention is to provide a radiation image reading apparatus capable of reducing the influence of scattered radiation and improving the quality of radiation images.

[0012]

In order to solve the above problems, the invention according to claim 1 provides a support plate and a stimulable phosphor sheet arranged on the side opposite to the radiation irradiation side of the support plate. A reading means for reading the stimulated emission light emitted from the stimulable phosphor sheet, and irradiating the stimulable phosphor sheet with radiation that has sequentially passed through the subject and the support plate. In a radiation image reading device for reading radiation image information recorded on the stimulable phosphor sheet as stimulable luminescent light according to energy of radiation, the support plate is formed by a scattered radiation removing grid, and the scattering The radiation removing grid and the stimulable phosphor sheet are provided in contact with each other.

According to the first aspect of the present invention, the scattered radiation removing grid supports and holds the stimulable phosphor sheet, and scatters low-energy radiation scattered on the stimulable phosphor sheet during radiography. Prevents image information based on (scattered rays) from being accumulated and recorded. In particular, by using the grid as a support plate, the support plate is no longer needed,
The scattered radiation generated on the support plate is reduced, and the influence of the scattered radiation can be further reduced. Further, since the grid and the stimulable phosphor sheet are in contact with each other, image information based on radiation can be accumulated and recorded in the stimulable phosphor sheet at a stage where scattering of scattered rays generated in the grid itself is smaller. By reading the accumulated and recorded image information, more accurate image information can be obtained.

According to a second aspect of the present invention, in the radiation image reading apparatus according to the first aspect, the stimulable phosphor sheet is covered with a moisture-proof protective film.

According to the invention of claim 2, it is needless to say that the same effect as that of the invention of claim 1 can be obtained. In particular, the stimulable phosphor sheet is covered with a moisture-proof protective film. The presence of moisture such as humidity and dirt can be prevented and the stimulable phosphor sheet itself can be prevented from being scratched.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the radiation image reading apparatus described above, the scattered radiation removing grid and the stimulable phosphor sheet are bonded via a resin film.

According to a fourth aspect of the present invention, in the radiation image reading apparatus according to any one of the first to third aspects, the photostimulable phosphor sheet is stimulated from a surface opposite to a surface irradiated with radiation. It is characterized by reading emitted light.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. In the present embodiment, a “radiation image information recording / reproducing system” in which X-rays transmitted through a subject are irradiated onto a stimulable phosphor sheet to accumulate and record image information.
The X-ray image reading apparatus (radiation image reading apparatus) used in the above will be described.

[First Embodiment] An X-ray image reading apparatus 10 according to the present embodiment is used for X-ray imaging in a standing position, as shown in FIG. 1 and FIG. A housing 11, a grid 12, an excitation light source 13, a light guide means 14, a photoelectric conversion means 15, an erasing means 16, an image processing means 17, an image output means 18, and a stimulable phosphor sheet 19 are provided. The excitation light source 13, the light guide means 14, and the photoelectric conversion means 15 are arranged on the back surface side (the side opposite to the X-ray irradiation side) of the stimulable phosphor sheet 19, and these are the back surface of the stimulable phosphor sheet 19. The reading means reads the stimulated emission light from the side.

The housing 11 protects various devices mounted therein and, after photographing, the stimulable phosphor sheet 19
It is intended to prevent the image information stored and recorded by being irradiated with light from disappearing from disappearing. For X-ray photography, X-ray source 3
The subject 40 and the front plate 11 of the housing 11 illuminated from 0
Since the stimulable phosphor sheet 19 is irradiated with X-rays that have passed through a, the front plate 11a of the housing 11 is made of a material having a high X-ray transmittance. The front plate 11a preferably has a thickness of about 1 to 5 mm so as not to hinder the transmission of X-rays. Moreover, it is preferable that the housing 11 is made of a material having relatively high rigidity so that various devices mounted therein can be surely protected.

Examples of the material having high X-ray transmittance and high rigidity include aluminum, carbon fiber reinforced resin, acrylic resin, phenol resin, polyimide resin, and composite material of these resins and aluminum. In the present embodiment, carbon fiber reinforced resin is used as the material of the housing 11.

The grid 12 is used as a means for removing low-energy radiation (scattered rays) scattered when passing through an object such as a subject. The grid 12 includes, for example, as shown in FIG. 3, a radiation absorption layer 12a made of lead or the like having a high radiation absorption rate and a radiation transmission layer 12b made of aluminum, paper, wood, a synthetic resin or the like having a low radiation absorption rate. The laminated body provided alternately is covered with the cover member 12c having a low radiation absorption rate. Grid 1
Of the radiation that is going to pass through 2, the rectilinear component is easily transmitted and the scattered radiation is difficult to be transmitted, so that the scattered radiation is removed. The grid 12 is fixed in the vicinity of the front plate 11a of the housing 11 and also has a function as a support for supporting the stimulable phosphor sheet 19 substantially perpendicularly to the X-ray irradiation direction. In, the stimulable phosphor sheet 19 is fixed to the surface of the grid 12 opposite to the X-ray irradiation side (see FIGS. 1 and 2).

The stimulable phosphor sheet 19 is formed by laminating a stimulable phosphor 19b on a sheet-like support 19a (see FIG. 2). The sheet-shaped support 19a is easy to handle.
It is preferably made of a flexible material such as wool, cotton, paper or plastic film. The stimulable phosphor 19b accumulates the irradiated X-ray energy and emits stimulated emission according to the accumulated X-ray energy when the excitation light is irradiated.

Examples of the stimulable phosphor 19b are rare earth-activated strontium sulfide-based or rare earth-activated lanthanum oxysulfide-based phosphors described in US Pat. No. 3,859,527, and US Pat. Rare earth activated alkaline earth metal fluorohalide phosphors described in Japanese Patent No. 265525;
No. 12144, a rare earth activated lanthanum oxyhalide type phosphor, and copper and / or lead activated zinc sulfide, rare earth activated alumina / barium oxide described in JP-A-55-12142. Examples thereof include silica-based or silica / alkaline earth metal-based phosphors.

The stimulable phosphor sheet 19 in the present embodiment has a grid (via an adhesive (not shown)) with both surfaces thereof covered with a moisture-proof protective film 20 as a moisture-proof protective film. It is bonded to 12 (see FIG. 2). The moisture-proof protective film 20 has a function of preventing moisture from entering the stimulable phosphor sheet. The moisture-proof protective film 20 is preferably transparent and has a high X-ray transmittance so as not to prevent transmission of X-rays, excitation light and stimulated emission light.

As the moisture-proof protective film 20 having such characteristics, polyethylene film, polypropylene film, vinyl chloride resin film, polyethylene terephthalate film, polymethacrylate film,
Examples thereof include resin films such as nitrocellulose film and cellulose acetate film, laminates thereof, and those obtained by vapor-depositing a thin film of metal oxide, silicon nitride or the like on these films. In the present embodiment, a polyethylene terephthalate film obtained by vapor-depositing a metal oxide is adopted as the moisture-proof protective film 20, which is arranged on both sides of the stimulable phosphor sheet 19 and heat-sealed on the outer edge thereof. There is. The protective film may be different on the X-ray irradiation side and the excitation light irradiation side.
An extremely thin metal thin film that does not interfere with X-ray transmission may be used on the radiation side.

The excitation light source 13 is a stimulable phosphor sheet 19
By irradiating with excitation light, it has a function of emitting stimulated emission light according to image information stored and recorded. The excitation light source 13 in the present embodiment can irradiate excitation light onto the stimulable phosphor sheet 19 while reciprocating in the direction of the arrow in FIG. 1 by a driving mechanism (not shown).

The light guide means 14 is a stimulable phosphor sheet 20.
The stimulated emission light emitted from the device functions so as to be guided to the photoelectric conversion means 15, and is made of a transparent acrylic plate. The light guide means 14 reciprocates in synchronization with the excitation light source 13. The photoelectric conversion means 15 detects the stimulated emission light emitted from the stimulable phosphor sheet 19 and generates an electric signal according to the amount of the stimulated emission light. In this embodiment, a photomultiplier is used as the photoelectric conversion means 15.

The erasing means 16 reads the image information from the stimulable phosphor sheet 19 by the reading means composed of the excitation light source 13, the light guide means 14 and the photoelectric conversion means 15, and then the stimulable phosphor sheet 19 is read. It serves to release the radiation energy remaining in 19. This erasing means 16 enables new X-ray imaging.

The image processing means 17 obtains a digital image signal by A / D converting the image information converted into an electric signal by the photoelectric conversion means 15. The image output means 18 outputs the digital image signal obtained by the image processing means 17 as an X-ray image. Examples of the image output unit 18 include a device for displaying an X-ray image such as a CRT or a liquid crystal display, and a device for hard-copying an X-ray image such as an inkjet printer.

The radiation image reading apparatus 10 having such a configuration
The X-ray image of the subject 40 and the front plate 11
a, the image information accumulated and recorded in the stimulable phosphor sheet 19 through the grid 12 can be read. In particular, since the grid and the stimulable phosphor sheet are in contact with each other, the image information based on radiation is accumulated and recorded in the stimulable phosphor sheet at a stage where the scattering of scattered rays generated in the grid itself is less, More accurate image information can be acquired by reading the stored and recorded image information.

Further, as described above, the stimulable phosphor sheet 1 is used.
More accurate image information can be obtained by reading the image information on the surface opposite to the surface irradiated with the radiation on 9. This is because there is a difference in the image information that is stored and recorded due to the energy difference of the radiation components. The direct component of the image information in the radiation is straight and relatively high energy radiation. On the other hand, the scattered radiation emitted when the radiation collides with the object is radiation of relatively low energy, and the image information is scattered and disturbed. Moreover, by disposing the grid 12, the energy of the scattered radiation is further reduced. Storing and recording the image information in the stimulable phosphor sheet 19 means that the energy of the radiation is absorbed in the stimulable phosphor sheet 19, so that the high-energy straight-through radiation is bright. The back side of the exhaustible phosphor sheet 19 can be reached, and image information can be accumulated and recorded on the back side. On the other hand, low-energy scattered radiation can accumulate and record image information on the front side of the stimulable phosphor sheet 19, but the energy is absorbed before reaching the back side, and few components reach the back side. Therefore, since the image information on the back side is information having many direct components of image information (small scattered rays), more accurate image information can be acquired.

[Second Embodiment] As shown in FIG. 4, the X-ray image reading apparatus according to the present embodiment is used for X-ray imaging in a supine position. A reading unit including the light guiding unit 14 and the photoelectric conversion unit 15; a configuration and a function of the erasing unit 16; the housing 11; the grid 12;
The material characteristics of the stimulable phosphor sheet 19 and the moisture-proof protective film 20 are substantially the same as those of the X-ray image reading apparatus according to the first embodiment, and therefore their explanations are omitted. Further, the image processing means 17 and the image output means 18 can be substantially the same, so that the illustration thereof is omitted.

In the present embodiment, a top plate 50 that supports the weight of the subject 40 is provided above the housing 11 of the X-ray image reading apparatus 10 (see FIG. 4). This top plate 50
It is made of a material having a rigidity that can bear the weight of the subject 40 and a high X-ray transmittance, and an acrylic plate is used in the present embodiment.

The radiation image reading apparatus 10 having such a configuration
By the X-ray photography in, it is possible to read the image information which is transmitted through the subject 40, the top plate 50, the front plate 11a, and the grid 12 and accumulated and recorded in the stimulable phosphor sheet 19. Further, similar to the first embodiment, more accurate image information can be obtained by reading the image information on the surface opposite to the surface on which the stimulable phosphor sheet 19 is irradiated with radiation.

[Third Embodiment] In the X-ray image reading apparatus according to the present embodiment, as shown in FIG. 6, the stimulable phosphor sheet 19 is not fixed to the grid 12 and the circulating and conveying means 21 is provided. The image information stored in the stimulable phosphor sheet 19 is read by the reading means provided in the circulation path and erased by the erasing means 16.

In the present embodiment, the configurations and functions of the erasing means 16, the image processing means 17 and the image output means 18, the material characteristics of the housing 11, the grid 12 and the stimulable phosphor sheet 19 will be described below. Since it is substantially the same as that of the X-ray image reading apparatus according to the first embodiment,
The description is omitted.

In the X-ray image reading apparatus according to this embodiment, the stimulable phosphor sheet 1 is provided behind the grid 12.
A pressing plate 22 is provided for pressing the grid 9 against the grid 12 and temporarily holding the grid 9. The pressing plate 22 is movable in the direction of the arrow shown in FIG. 6 by a driving mechanism (not shown), and the photostimulable phosphor is conveyed to the photographing position A between the grid 12 and the pressing plate 22. The sheet 19 can be temporarily held. Further, FIG. 7 shows a state in which the stimulable phosphor sheet 19 is held at the photographing position A by the grid 12 and the pressing plate 22.

As shown in FIG. 7, the photostimulable phosphor sheet 19 held at the photographing position A by the grid 12 and the pressing plate 22 is irradiated with X-rays that pass through the subject to complete the X-ray photographing. After that, the stimulable phosphor sheet 19 is conveyed to the reading position B by the circulation conveying means 21. In the present embodiment, the light guide means 14 and the photoelectric conversion means 15
Are arranged on the back surface side (the side opposite to the X-ray irradiation side) of the stimulable phosphor sheet 19 conveyed to the reading position B (FIG. 6).
It is possible to detect stimulated emission light emitted from the stimulable phosphor sheet 19 by the excitation light emitted by the excitation light source 13.

After the image information accumulated on the stimulable phosphor sheet 19 is read at the reading position B, the circulating and conveying means 21 is used.
Is again conveyed to the photographing position A. In the present embodiment, since the erasing means 16 is provided on the path from the reading position B to the photographing position A, the radiant energy remaining in the stimulable phosphor sheet 19 is released, It can be used for new X-ray photography.

By the X-ray photography in the radiation image reading apparatus having such a structure, the subject 40 and the front plate 11a,
Further, the stimulable phosphor sheet 19 is transmitted through the grid 12.
The image information stored and recorded in can be read.
Also, as in the first embodiment, the stimulable phosphor sheet 19 is used.
More accurate image information can be obtained by reading the image information on the surface opposite to the surface irradiated with the radiation. Further, in this measure, the image information on the surface irradiated with the radiation may be read.
It is possible by changing the layout such as 4.

In the above embodiments, an adhesive is used to bond the stimulable phosphor sheet 19 and the grid 12 to each other, but the present invention is not limited to this and the double-sided tape is used. It may be adhered by. Further, the radiation image reading apparatus may have any configuration, and it is needless to say that the specific detailed structure and the like can be appropriately changed.

[0043]

According to the present invention, image information based on scattered rays is accumulated and recorded on the stimulable phosphor sheet by a grid that removes scattered low-energy radiation (scattered rays) generated during radiography. Can be prevented. In particular, by using the grid as the support plate, the support plate is not required and the scattered rays generated on the support plate are reduced, so that the influence of the scattered rays can be further reduced. In addition, since the grid and the stimulable phosphor sheet are in contact with each other during radiography, image information based on radiation is accumulated and recorded in the stimulable phosphor sheet at a stage where scattering of scattered rays generated in the grid itself is less. By reading the stored and recorded image information, more accurate image information can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of an X-ray image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion II of FIG.

FIG. 3 is an enlarged cross-sectional view of the grit according to the embodiment of the present invention.

FIG. 4 is a schematic view of an X-ray image reading apparatus according to a second embodiment of the present invention.

5 is an enlarged cross-sectional view of a V portion of FIG.

FIG. 6 is a schematic view of an X-ray image reading apparatus according to a third embodiment of the present invention.

7 is an enlarged cross-sectional view of a VII part in FIG.

FIG. 8 is a schematic view of a conventional radiation image reading apparatus for standing.

9 is an enlarged cross-sectional view of a portion IX in FIG.

FIG. 10 is a schematic view of a conventional radiation image reading apparatus for lying down.

[Explanation of symbols]

10 X-ray image reader (radiation image reader) 11 housing 11a front plate 12 grid 13 Excitation light source 14 Light guiding means 15 Photoelectric conversion means 16 Erasing means 17 Image processing means 18 Image output means 19 Photostimulable phosphor sheet 19a Sheet-like support 19b Photostimulable phosphor 20 Moisture-proof protective film (moisture-proof protective film) 21 Circulating Conveyor 22 Press plate 30 X-ray source 40 subjects 50 top plate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiyuki Ishimitsu             591-7 Kamihirose, Sayama City, Saitama Konica Stock             In the company F-term (reference) 2G083 AA03 CC04 EE02                 2H013 AC01 AC03

Claims (4)

[Claims] 1. A support plate, a photostimulable phosphor sheet arranged on the side opposite to the radiation irradiation side of the support plate, and a reading means for reading the photostimulated luminescent light emitted from the photostimulable phosphor sheet. And irradiating the stimulable phosphor sheet with radiation that has sequentially passed through the subject and the support plate, and radiation image information recorded on the stimulable phosphor sheet according to the energy of the irradiated radiation. In the radiation image reading apparatus for reading as stimulated emission light, the support plate is formed by a scattered radiation removing grid, and the scattered radiation removing grid and the stimulable phosphor sheet are provided in contact with each other. A radiation image reading device characterized by: 2. The radiation image reading device according to claim 1, wherein the stimulable phosphor sheet is covered with a moisture-proof protective film. 3. The radiation image reading apparatus according to claim 1, wherein the scattered radiation removing grid and the stimulable phosphor sheet are bonded to each other via a resin film. apparatus. 4. The radiation image reading device according to claim 1, wherein the stimulated emission light is read from a surface of the photostimulable phosphor sheet opposite to a surface irradiated with radiation. A characteristic radiation image reading device.