JPH0886900A - Stimulable phosphor sheet and method for reading radiation image - Google Patents

Abstract

PURPOSE: To reduce the reflection loss of stimulated emission light due to the reflection on the back of a sheet of the stimulated emission light emitted from the sheet when the back or both sides of the sheet are read. CONSTITUTION: The stimulable phosphor sheet 1 is constituted by laying a phosphor layer 3 which emits stimulated emission light due to the radiation of exciting light and a protective layer 4 on the front surface of a transparent support 2 and placing a reflection preventing film 5 on the back of the support 2 to prevent the reflection of the stimulated emission light and the exciting light. When both sides of the sheet 1 where radiation images are stored and recorded, are read, it prevents the stimulated emission light emitted from the back of itself from reflecting on the interface to the air, and improves the condensing efficiency of the stimulated emission light on the back side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stimulable phosphor sheet for accumulating and recording a radiation image, and more particularly to a stimulable phosphor sheet suitable for double-sided reading and a radiation image reading method using the sheet. It is a thing.

[0002]

2. Description of the Related Art An image signal is obtained by reading a recorded radiation image, and after subjecting this image signal to appropriate image processing,
Image reproduction and recording are performed in various fields.
For example, an X-ray image is recorded using a film having a low gamma value designed to be suitable for later image processing, and the X-ray image is read from the film on which the X-ray image is recorded and converted into an electric signal. By performing image processing on this electric signal (image signal) and reproducing it as a visible image on a copy photograph or the like, there is provided a system capable of obtaining a reproduced image having good image quality performance such as contrast, sharpness, and graininess. It has been developed (see Japanese Patent Publication No. 61-5193).

In addition, the applicant of the present invention has proposed radiation (X-ray, α
Radiation, β rays, γ rays, electron rays, ultraviolet rays, etc.), a part of this radiation energy is accumulated, and when excitation light such as visible light is then irradiated, the stimulated emission light of a light amount corresponding to the accumulated energy is emitted. Stimulable phosphor that emits light (stimulable phosphor)
Using, the radiographic image of a subject such as a human body is once photographed and recorded on a sheet-shaped stimulable phosphor, and the stimulable phosphor sheet is scanned with excitation light such as laser light to generate stimulated emission light.
A radiation recording / reproducing system that photoelectrically reads the obtained stimulated emission light to obtain an image signal, and outputs a radiation image of a subject as a visible image on a recording material such as a photographic light-sensitive material or a CRT based on the image signal. Have already been proposed (JP-A-55-12429, etc.).

On the other hand, as a method of photoelectrically reading the above-described stimulated emission light, the photoelectric reading means described above is arranged on both sides of the stimulable phosphor sheet so that excitation light is emitted only on both sides or one side of the stimulable phosphor sheet. And a double-sided condensing reading method for photoelectrically reading the stimulated emission light emitted by this excitation light scanning from both sides of the stimulable phosphor sheet has been proposed (for example, JP-A-55-87970). . In such a double-sided condensing reading method, one radiation image is accumulated and recorded on the stimulable phosphor sheet, and the stimulated emission light is condensed from both sides of the stimulable phosphor sheet. The light collection efficiency is improved and the S / N ratio is further improved.

In the double-sided condensing reading method disclosed in Japanese Patent Laid-Open No. 55-87970, a stimulable phosphor sheet is formed by laminating a stimulable phosphor sheet on the surface of a transparent support to form a transparent stimulable phosphor sheet. A stimulable phosphor sheet on which a radiation image is stored and recorded is mounted on a holder, and photoelectric reading means are arranged above and below the stimulable phosphor sheet. That is, in the photoelectric reading means arranged above the holder, the stimulated emission light emitted from the surface of the stimulable phosphor sheet is read, and in the photoelectric reading means arranged below the holder, the back surface of the stimulable phosphor sheet is read. The stimulated emission light emitted from the device is read.

[0006]

However, in the above-mentioned double-sided reading method, when the excitation light is irradiated from the front surface of the stimulable phosphor sheet, the stimulated emission light emitted to the back surface side of the sheet causes the support of the sheet. At the interface between the body and the air, about 4% of the light is reflected, and the stimulated emission light is lost, so that the light collection efficiency of the photoelectric reading unit on the back side is reduced, and the light collection efficiency of the double side reading is reduced. The improvement and the S / N ratio will not be achieved.
This is not limited to double-sided reading, but is a problem that similarly occurs when a radiation image is read only from the surface opposite to the surface of the sheet irradiated with the excitation light.

In view of the above-mentioned circumstances, the present invention has a reflection loss of stimulated emission light due to reflection of the stimulated emission light emitted from the sheet when reading from the back surface of the sheet or double-sided reading, on the back surface of the sheet. It is an object of the present invention to provide a stimulable phosphor sheet with reduced emission and a radiation image reading method using the sheet.

[0008]

The stimulable phosphor sheet according to the present invention is transparent to a stimulable phosphor layer which stores and records a radiation image and emits stimulated emission light which carries the radiation image upon irradiation with excitation light. In the stimulable phosphor sheet laminated on the surface of the support, an antireflection film for preventing reflection of the stimulated emission light is provided on the back surface of the support.

Further, in the stimulable phosphor sheet, it is preferable that the antireflection film also prevents reflection of the excitation light.

Further, the radiation image reading method according to the present invention is a reading method using the above-mentioned stimulable phosphor sheet according to the present invention, wherein the stimulable fluorescent sheet of the stimulable phosphor sheet on which a radiation image is stored and recorded. Irradiating excitation light to the surface on which the body layer is provided, and carrying the radiation image emitted from the surface on the antireflection film side of the sheet or both surfaces of the sheet by irradiation of the excitation light. An image signal representing the radiation image is obtained by photoelectrically detecting the stimulated emission light.

[0011]

The stimulable phosphor sheet according to the present invention is provided with an antireflection film for preventing reflection of stimulated emission light on the back surface, so that from the back surface of the sheet, that is, the surface on which the antireflection film is provided. When reading or reading from both sides of the sheet, the stimulated emission light emitted from the back surface of the stimulable phosphor sheet is transmitted to the back surface side without being reflected at the interface between the support and air. Therefore, the stimulated emission light emitted on the back side of the sheet can be efficiently detected by the photoelectric detection means provided on the back side without loss.

Further, since the antireflection film also prevents the reflection of the excitation light, the excitation light transmitted through the stimulable phosphor layer will not be reflected on the back surface of the sheet, so that the excitation light will not be reflected on the sheet. The other side of the stimulable phosphor is excited by being reflected on the back surface of the and the scattered light is not emitted (flare phenomenon). Therefore, it is possible to prevent the contrast of the radiation image obtained from this sheet from being lowered and to prevent the loss of the radiation image accumulated and recorded in the stimulable phosphor.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a stimulable phosphor sheet according to an embodiment of the present invention. As shown in FIG. 1, a stimulable phosphor sheet 1 according to an embodiment of the present invention has a transparent support 2 on which a phosphor layer 3 composed of a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state is laminated. A protective layer 4 for protecting the phosphor layer 3 is provided on the surface of the phosphor layer 3 opposite to the support 2, and the support layer 2 on the opposite side of the support 2 is provided. An antireflection film 5 is provided on the back surface to prevent reflection of excitation light described below and stimulated emission light emitted from the phosphor layer 3 by irradiation of the excitation light.

The stimulable phosphor contained in the phosphor layer 3 is, for example, BaFBr: 0.001 Eu which emits stimulated emission light of 300 to 700 nm by excitation of He-Ne laser light having a wavelength of 632.8 nm. ²⁺ shall be used.

The details of the antireflection film will be described below.

The material used for the antireflection film in the stimulable phosphor sheet of the present invention has a reflection characteristic for stimulated emission light and excitation light emitted when the stimulable phosphor contained in the panel is irradiated with excitation light. Is low. That is, the reflectance of the stimulable phosphor with respect to light in the excitation wavelength region and light in the wavelength region of stimulated emission light is small. Examples of such materials include inorganic fluorides such as magnesium fluoride, calcium fluoride and cryolite; and inorganic oxides such as aluminum oxide, zirconium dioxide, titanium dioxide and silicon monoxide.

The antireflection film 5 can be provided by forming a thin film made of the above material on the back surface of the stimulable phosphor sheet 1 by a method such as vacuum deposition or sputtering. The film thickness of the antireflection film 5 is
The wavelength is preferably on the order of the wavelength of the excitation light, and in particular, its optical thickness is an odd multiple of 1/4 of the wavelength of the excitation light (where the wavelength is λ
Then, it is preferable that the film thickness = nλ / 4, n = 1, 3, 5 ...) Since the reflectance becomes low. Further, the reflectance can be further reduced by forming the antireflection film 5 as a multilayer film. In this case, the film thickness of each layer is basically an odd multiple of 1/4 wavelength, but a multilayer transmission film slightly deviated from an odd multiple of 1/4 wavelength may be used. Generally, it is desirable that the thickness of the antireflection film 5 be about 0.1 to 10 μm.
In the present embodiment, reflection of light having a wavelength of 300 nm to 700 nm is prevented. Magnesium fluoride (MgF ₂ )
Approximately 1580 angstroms (H to be described later)
The antireflection film 5 was provided by adhering it to a thickness of 1/4 of the wavelength of 632.8 nm of the e-Ne laser light.

Next, reading of a radiation image from the stimulable phosphor sheet according to this embodiment will be described.

The stimulable phosphor sheet on which a radiation image is recorded by a radiation image recording device (not shown) is set at a predetermined position of the radiation image reading device shown in FIG.

FIG. 2 is a diagram showing a radiation image reading apparatus for performing double-sided reading.

The stimulable phosphor sheet 1 is arranged on endless belts 9a and 9b which are rotated by a motor (not shown). Above the sheet 1, a He-Ne laser light source 10 which emits a light beam 11 as excitation light, and a rotary polygon mirror which is reflected and deflected by the light beam 11 and is rotated by a motor (not shown) for main-scanning the sheet 1 Twelve are arranged. Furthermore, above the position where the light beam 11 is scanned,
A condensing guide 14a for concentrating the stimulated emission light emitted from the scanning of the light beam 11 from above is arranged in proximity, and a condensing guide for concentrating the stimulated emission light from below is arranged below that position. 14b is arranged perpendicular to the seat 1. The light collecting guides 14a and 14b are photomultipliers (photomultiplier tubes) 15a and 15 for photoelectrically detecting stimulated emission light, respectively.
b is connected. This photomultiplier 15a,
15b is connected to logarithmic amplifiers 16a and 16b, and the logarithmic amplifiers 16a and 16b are connected to A / D converters 17a and 17b, and the A / D converters 17a and 17b are connected to a storage device 18. .

The stimulable phosphor sheet 1 on which the radiation image of the subject is stored and recorded is set on the endless belts 9a and 9b. At this time, the sheet 1 is set so that the surface on the side where the phosphor layer is provided faces upward. The stimulable phosphor sheet 4A set at this predetermined position is an endless belt.
By 9a and 9b, it is conveyed (sub-scanning) in the arrow Y direction. On the other hand, the light beam 11 emitted from the laser light source 10 is reflected and deflected by a rotary polygon mirror 12 driven by a motor (not shown) and rotating at a high speed in the arrow direction, and is incident on the sheet 1 and is substantially in the sub-scanning direction (arrow Y direction). The main scanning is performed in the vertical arrow X direction. From the portion of the sheet 1 irradiated with the light beam 11, stimulated emission lights 13a and 13b (here, stimulated emission lights 13a and 13b) having a light amount corresponding to the stored and recorded radiation image information.
Indicates the sheet emitted from above and below the sheet 1). This stimulated emission light 13a is a light guide.
14a, and photoelectrically detected by a photomultiplier (photomultiplier) 15a. The stimulated emission light 13a that has entered the focusing guide 15a from the entrance end face travels through the inside of the focusing guide 14a by repeating total reflection, exits from the exit end face, is received by the photomultiplier 15a, and represents a radiation image. The photomultiplier 15a converts the amount of the stimulated emission light 13a into an electric signal. Similarly, the stimulated emission light 13b is guided by the light collecting guide 14b and photoelectrically detected by the photomultiplier (photomultiplier tube) 15b.

Here, in the case of the conventional stimulable phosphor sheet, as shown in FIG. 3A, the stimulated emission light 13b emitted from the back surface of the sheet 1 is generated between the support 2 of the sheet 1 and the air. About 4% of the light is reflected at the interface of, and as a result, the amount of stimulated emission light detected by the photomultiplier 15b is reduced, resulting in a decrease in light collection efficiency. On the other hand, the stimulable phosphor sheet 1 according to the present invention
Since the antireflection film 5 is provided on the back surface of the support 2, the stimulated emission light 13b emitted to the back surface side of the sheet 1 is reduced in reflection level to about 1.5%.
The loss due to the reflection of b is reduced and the photomultiplier 15
The light collection efficiency of b can be improved.

Since the antireflection film 5 also has a property of preventing reflection of excitation light, the excitation light is reflected on the back surface of the sheet 1 to excite other portions of the phosphor to emit scattered light ( Since the flare phenomenon) is eliminated, it is possible to prevent the contrast of the radiation image obtained from the sheet 1 from being lowered and to prevent the radiation image accumulated and recorded in the phosphor from being lost.

The analog output signal SA output from the photomultiplier 15a is logarithmically amplified by the logarithmic amplifier 16a and input to the A / D converter 17a, where it is converted into a digital image signal S ₁ and stored in the storage medium 18. Entered in. Similarly, the analog output signal SB output from the photomultiplier 15b is logarithmically amplified by the logarithmic amplifier 16b and input to the A / D converter 17b, where it is converted into the digital image signal S ₂ and stored in the storage medium. Entered in 18. These two
The two image signals S ₁ and S ₂ are subjected to predetermined image processing by an image processing means (not shown) and reproduced as a visible image by a reproducing means such as a laser printer or a CRT.

In the double-sided reading embodiment described above,
The stimulable phosphor sheet 1 is scanned by the laser light generated from one laser light source 10. However, the present invention is not limited to this, and as shown in FIG. Laser light source 10 on the front side and the back side respectively
a, 10b and rotating polygon mirrors 12a, 12b may be provided respectively, and both surfaces of the stimulable phosphor sheet 1 may be scanned with the light beams 11a, 11b to read the stimulated emission light and obtain two image signals. . The protective layer 4 used in the sheet 1 prevents the reflection of the excitation light, and since the excitation light is prevented from being reflected by the sheet 1, the above-mentioned flare phenomenon does not occur, and good radiation without noise is obtained. The image can be read.

Further, in the above-mentioned embodiment, the apparatus for reading the radiation images from both sides of the stimulable phosphor sheet is explained, but the invention is not limited to this.
Irradiation with excitation light from the surface of the stimulable phosphor sheet, and also to a radiation image reading device that detects stimulated emission light only from the back surface,
The stimulable phosphor sheet according to the present invention is applicable. Also in this case, similarly to the above-mentioned embodiment, since the stimulated emission light emitted from the stimulable phosphor sheet is prevented from being reflected on the back surface of the sheet, there is no loss due to reflection of the stimulated emission light. It is possible to read a radiation image with high light efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a stimulable phosphor sheet according to the present invention.

FIG. 2 is a diagram showing a radiographic image reading apparatus that performs double-sided reading.

FIG. 3 is a diagram showing a cross section of a stimulable phosphor sheet according to the present invention.

FIG. 4 is a diagram illustrating another embodiment of a radiation image reading apparatus that performs double-sided reading.

[Explanation of symbols]

 1 stimulable phosphor sheet 2 transparent support 3 phosphor layer 4 protective layer 5 antireflection film 10 laser light source 11 laser light 12 mirror 13a, 13b stimulated emission light 14a, 14b light guide 15a, 15b photomultiplier 16a, 16b Logarithmic converter 17a, 17b A / D converter 18 Storage medium

Claims (3)

[Claims] 1. A stimulable phosphor sheet comprising a transparent support, and a stimulable luminescent layer that emits stimulated emission light for carrying the radiation image when the radiation image is accumulated and recorded and is irradiated with excitation light. 2. The stimulable phosphor sheet according to claim 1, wherein an antireflection film for preventing reflection of the stimulated emission light is provided on the back surface of the support. 2. The antireflection film is an antireflection film that also prevents reflection of the excitation light.
The stimulable phosphor sheet described. 3. The excitation light is applied to the surface of the stimulable phosphor sheet according to claim 1 or 2 on which the stimulable phosphor layer is provided, in which a radiation image is stored and recorded, and the excitation light is applied. By photoelectrically detecting the stimulated emission light carrying the radiation image emitted from the surface of the sheet on which the antireflection film is provided or both surfaces of the sheet, an image signal representing the radiation image is obtained. A method for reading a radiation image, which comprises: