JP2952453B2 - Double-sided condensing phosphor sheet reading method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided condensing phosphor reading method for a stimulable phosphor sheet.

[0002]

2. Description of the Related Art Radiation (X-ray, α-ray,
(β-rays, γ-rays, ultraviolet rays, electron beams, etc.), a part of the energy of this radiation is accumulated in the phosphor, and then, when the phosphor is irradiated with excitation light such as visible light, the energy is accumulated. The phosphor emits stimulated emission according to the energy. Phosphors exhibiting such properties are called stimulable phosphors (stimulable phosphors), and by utilizing this stimulable phosphor, radiation image information of a subject such as a human body is temporarily stored in a stimulable phosphor sheet ( (Hereinafter referred to as a stimulable phosphor sheet), and scans it with excitation light to emit stimulated light. The stimulated emission light is photoelectrically read to obtain an image signal, and the image signal is processed. Methods for obtaining a radiation image of a subject having good diagnostic suitability are widely known (for example, JP-A-55-12429 and JP-A-55-116340,
No. 55-163472, No. 56-11395, No. 56-104645). This final image can be played back as a hard copy or on a CRT.

As a method of reading the stimulated emission light, a photoelectric reading means for photoelectrically reading the stimulated emission light is disposed only on the side on which the excitation light is scanned, so that the light is emitted from one surface of the stimulable phosphor sheet. A method of photoelectrically reading the stimulated luminescent light is known. In addition to this method, the photoelectric reading means as described above is disposed on both surfaces of the stimulable phosphor sheet, thereby emitting light from both surfaces. A double-sided condensing reading method for photoelectrically reading the stimulated emission light is known (see, for example, JP-A-55-87970 and JP-A-56-11397).

The method of photoelectrically reading the stimulated emission light from both sides of the stimulable phosphor sheet as described above has the advantage that the overall light-collecting efficiency is improved and the S / N ratio is improved. .

On the other hand, by forming the protective layer of the radiation image conversion panel (storage phosphor sheet) from a material having a fine light guide structure extending substantially perpendicular to the phosphor layer surface, A radiation image conversion panel capable of obtaining an image with improved image quality has been proposed (Japanese Unexamined Patent Publication No.
No. 112800). However, the above publication does not describe nor suggest double-sided condensing reading for photoelectrically reading stimulated emission light emitted from both sides of the panel.

[0006]

In the double-sided condensing reading method described above, the scanned excitation light passes through the stimulable phosphor sheet, reaches the photoelectric reading means disposed on the back surface of the sheet, and is reflected there. The problem arises. That is, the reflected and diffused excitation light excites the stimulable phosphor in the portion other than the scanning points of the stimulable phosphor sheet,
Unnecessary image information is photoelectrically read from both sides by the stimulated emission light emitted by the excitation light, and the sharpness of the finally obtained image is reduced.

In view of the above circumstances, an object of the present invention is to provide a double-sided condensing reading method for a stimulable phosphor sheet that can efficiently improve the sharpness of an image.

[0008]

According to a second aspect of the present invention, there is provided a double-sided reading method of a radiation image provided on a stimulable phosphor layer and on one side of the stimulable phosphor layer, which transmits only vertically incident light. Scanning the excitation light from the side opposite to the optical layer to the stimulable phosphor sheet on which the radiation image is accumulated and recorded by irradiating radiation carrying radiation image information. Stimulating emission light emitted from both sides of the stimulable phosphor sheet by excitation light scanning is photoelectrically read from both sides of the stimulable phosphor sheet to obtain an image signal of the radiation image. It is.

In the present invention, the optical layer that transmits only vertically incident light means a crystal such as urexite or a fiber optics plate (FO.
P. ), Light entering from the input surface at an angle smaller than a specific angle (maximum acceptance angle) with the normal to the input surface is confined in a fine light guide path to the output surface. And a layer made of a material that transmits. These have the property of transmitting light incident from the input surface at an angle smaller than a specific angle (maximum acceptance angle) with the normal to the input surface to the output surface while being confined in a fine light guide path. doing.

Urexite is a hydrated borate mineral of sodium and calcium, which is a triclinic crystal and has the above optical properties.

A fiber optics plate (F.
O. P. ) Is a thin fiber (core diameter 6 μm to 25 μm) in which a high refractive index core glass is coated with a low refractive index cladding glass.
μm) are fused optical elements.

[0012] Both of the above materials can be used in the present invention, but urexite is difficult to obtain, and is disadvantageous in terms of durability because it is brittle and slightly soluble in water. Therefore, it is preferable to use a fiber optics plate for the present invention.

This material can also transmit light incident on the output surface by reflection or the like to the input surface while being confined in the light guide path. This material is described in detail in JP-A-2-112800.

The optical layer of the stimulable phosphor sheet used in the double-sided condensing reading method of the present invention is provided with the above-mentioned materials.

[0015]

According to the double-sided condensing reading method of the present invention, the excitation light is scanned from the side opposite to the optical layer of the stimulable phosphor sheet when reading the radiation image.
Only the excitation light that has passed through the stimulable phosphor layer and entered the optical layer at an angle other than the maximum acceptance angle is emitted from the sheet without spreading while being confined in the fine light guide path. Furthermore, since the photoelectric detection means for reading the stimulated emission light emitted from the sheet is disposed on the back surface of the sheet at a position facing the excitation light source via the sheet, the emitted light is reflected by the photoelectric detection means. And is reflected and tries to enter the optical layer of the sheet again. However, a component exceeding the maximum acceptance angle of the optical layer due to the excitation light reflected by the photoelectric detection means and spread to the surroundings does not enter the back surface again and reach the stimulable phosphor layer. Therefore, it is possible to prevent a decrease in sharpness due to the excitation light re-entering by reflection from the back surface.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view showing an example of a stimulable phosphor sheet used in the double-sided condensing phosphor reading method of the stimulable phosphor sheet of the present invention.

On one side of the stimulable phosphor layer 12, a protective layer 14 is provided.
The other surface is provided with an optical layer 16 made of a material having a fine light guide path structure extending substantially perpendicularly to the surface of the stimulable phosphor layer 12. Also,
A protective layer or a support may be provided further outside the optical layer 16. In this embodiment, the optical layer 16 comprises
Although provided so as to be in contact with the stimulable phosphor layer 12, a support or a protective layer, or an adhesive layer for bonding the optical layer 16 and the stimulable phosphor layer 12 may be provided therebetween. . The stimulable phosphor sheet used in the present invention is
Any structure may be used as long as the optical layer as described above is provided on one side of the stimulable phosphor layer.

FIG. 2 is a schematic view of the fiber optics plate constituting the above-mentioned second protective layer as viewed from the direction of the input (output) force surface.

As shown in FIG. 2, a plurality of fibers having a low-refractive-index cladding glass 24 surrounding a high-refractive-index core glass 22 are adjacent via an absorber (EMA) glass 26. ing. The absorber glass 26 absorbs light that escapes from the core glass 22 to the outside through the clad glass 24 or light that has entered the clad glass 24. That is, one
The light incident on the input surface of one fiber is transmitted to the output surface in a state of being confined in a fine light guide (fiber) without escaping to the other fiber. Is output.

Accordingly, the light incident on the fiber optics plate does not spread since it is split for each fiber and transmitted to the output surface and output.

Next, the manner of storing and recording an X-ray image of a subject on the above-described stimulable phosphor sheet will be described.

The stimulable phosphor sheet is usually housed in a cassette for shielding excitation light such as visible light and used for X-ray photography. X-ray imaging is performed in a state where the X-ray source and the cassette containing the stimulable phosphor sheet are opposed to each other via the subject on the imaging table. At this time, in the stimulable phosphor sheet accommodated in the cassette, the optical layer may be located on either the front side or the back side of the stimulable phosphor layer. Here, X-rays are radiated from the X-ray source toward the subject, and X-rays transmitted through the subject are radiated on the stimulable phosphor sheet accommodated in the cassette, so that a transmitted X-ray image of the subject is accumulated. It is stored and recorded on the phosphor sheet.

FIG. 3 is a schematic view showing an example of an X-ray image reading apparatus for reading the X-ray image from the stimulable phosphor sheet 10 on which the X-ray image is stored as described above.

The stimulable phosphor sheet 10 is rotated by a motor (not shown) into endless belts 49a and 49a.
b On top of the optical layer (fiber optics plate)
Are arranged on the lower side. Above the sheet 10, a laser light source 41 that emits excitation light, a rotary polygon mirror 43 that reflects and deflects the laser light and performs main scanning on the sheet 10,
A motor 42 for rotating the rotary polygon mirror 43 is provided. Further, above the position where the laser light is scanned, a light guide 45a that condenses stimulated emission light emitted by the scanning of the laser light from above is disposed in close proximity, and below the position, A light guide 45b for concentrating the stimulating light from below is arranged perpendicular to the sheet 10.
Each of the light guides 45a and 45b is a photomultiplier (photomultiplier) 46a that photoelectrically detects stimulated emission light.
, 46b are connected. This photo multiplier 4
6a and 46b are connected to logarithmic amplifiers 47a and 47b, and the logarithmic amplifiers 47a and 47b are connected to a storage device 48.

Next, how the X-ray image reading apparatus reads an X-ray image from the stimulable phosphor sheet 10 will be described with reference to FIG. By the X-ray photography as described above, an X-ray image of the subject is accumulated and recorded on the stimulable phosphor sheet 10. The stimulable phosphor sheet 10 on which the X-ray image is recorded is set on endless belts 49a and 49b. The stimulable phosphor sheet 10 set at the predetermined position is conveyed (sub-scan) in the direction of the arrow Y by the endless belts 49a and 49b. On the other hand, the light beam emitted from the laser light source 41 is reflected and deflected by the rotary polygon mirror 43 driven by the motor 42 and rotated at a high speed in the direction of the arrow, enters the sheet 10 and is substantially perpendicular to the sub-scanning direction (the direction of the arrow Y). Main scanning in the direction of arrow X. From the portion of the sheet 10 irradiated with the light beam, the stimulated emission light 44a, 44b (here, the stimulated emission light 44a, 44a,
44b indicates those radiated from above and below the sheet 10, respectively). The stimulated emission light 44a is guided by a light guide 45a and is photoelectrically detected by a photomultiplier (photomultiplier tube) 46a. The light guide 45a is formed by molding a light-guiding material such as an acrylic plate, and is arranged such that a linear incident end face extends along a main scanning line on the stimulable phosphor sheet 10. The photomultiplier 46a is provided on the emission end face formed in an annular shape
Are coupled to each other. Light guide from the incident end face
The stimulated emission light 44a incident on the inside of the light guide 45a travels inside the light guide 45a by repeating total internal reflection, exits from the exit end face, is received by the photomultiplier 46a, and is received by the photomultiplier 46a. Light quantity is photomultiplier 46a
Is converted into an electric signal. Similarly, stimulating light 44
b is guided by a light guide 45b and is photoelectrically detected by a photomultiplier (photomultiplier) 46b.

Here, in the stimulable phosphor sheet of the present embodiment, the optical layer is configured to transmit only light substantially perpendicular to the surface of the stimulable phosphor layer, and is used for double-sided condensing reading. The optical layer is located on the lower side, and the excitation light is scanned from the protective layer side. At this time, the excitation light emitted from the laser light source 41 and transmitted through the protective layer, the stimulable phosphor layer, and the optical layer is reflected by the light guide 45b disposed adjacent to the optical layer, and is again reflected on the optical layer. The excitation light that reaches the optical layer exceeds the maximum acceptance angle of the optical layer, but does not reach the stimulable phosphor layer.

Next, the analog output signal S1 output from the photomultiplier 46a is logarithmically amplified by the logarithmic amplifier 47a and input to the storage device 48. Here, the analog output signal S1 is digitized by an A / D converter in the storage device 48, and a first image signal is obtained. Similarly, the analog output signal S2 output from the photomultiplier 46b is logarithmically amplified by the logarithmic amplifier 47b and input to the storage device 48. Here, the analog output signal S2
Is digitized by the A / D converter in the storage device 48 and the second
Is obtained. These two image signals are added by the arithmetic unit of the storage device 48 to obtain a final image signal. The signal level of this final image is
It is proportional to the logarithm of the amount of stimulated emission light emitted from each pixel of the sheet 10. In this manner, the photostimulated light emitted by the irradiation of the excitation light is condensed from both surfaces, so that the light condensing efficiency is increased and the S / N ratio of the obtained image is improved. In particular, since the light guide 45b collects the stimulated emission light from which the influence of the excitation light reflected and diffused by the light guide 45b has been removed as described above, the double-sided condensing reading from the conventional stimulable phosphor sheet is performed. Thus, an image with improved sharpness can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a stimulable phosphor sheet used in a double-sided condensing phosphor sheet reading method of the present invention.

FIG. 2 is a schematic view of a fiber optics plate viewed from a direction of an input (output) force surface.

FIG. 3 is a schematic diagram illustrating an example of an X-ray image reading device.

[Explanation of symbols]

 10 stimulable phosphor sheet 12 stimulable phosphor layer 14 protective layer 16 optical layer 20 fiber optics plate 22 core glass 24 clad glass 26 absorber glass 40 X-ray image reader 44 photostimulated light 45 light guide 46 photo Multiplier 47 Logarithmic converter 48 Storage device 49 Endless belt

Claims (1)

(57) [Claims] 1. A stimulable phosphor layer, and an optical layer provided on one side of the stimulable phosphor layer, which allows only vertically incident light to pass therethrough. By irradiating the stimulable phosphor sheet on which the radiation image is accumulated and recorded by irradiation, the excitation light is scanned from the side opposite to the optical layer, and the excitation light scan emits light from both surfaces of the stimulable phosphor sheet. A method for converging and reading both sides of a stimulable phosphor sheet, wherein the stimulated emission light is photoelectrically read from both sides of the stimulable phosphor sheet to obtain image signals of the radiation image.