JPH06130523A - Both side light condensing and reading method for stimulable phosphor sheet - Google Patents

Abstract

PURPOSE:To efficiently improve the sharpness of images in the both side light condensing and reading method for stimulable phosphor sheets. CONSTITUTION:The one surface of the stimulative phosphor layer 12 of the stimulable phosphor sheet 10 is provided with a protective layer 14 and the other surface is provided with a colored layer 16 contg. coloring agents which selectively absorb exciting light. This sheet 10 is so disposed that the colored layer 16 exists on lower side. The sheet is then scanned with the exciting light from the side of the protective layer 14. A photodetecting system disposed on the protective layer 14 side photoelectrically detects the stimulating light emitted from the surface of the sheet 10 by scanning with the exciting light and a photodetecting system disposed on the colored layer 16 side photoelectrically detects the stimulating light emitted from the rear surface. The output signals of the respective photodetecting systems are then added.

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 reading method for a stimulable phosphor sheet.

[0002]

2. Description of the Related Art Radiation (X rays, α rays,
When irradiated with β rays, γ rays, ultraviolet rays, electron beams, etc.), a part of the energy of this radiation is accumulated in the phosphor, and when the phosphor is subsequently irradiated with excitation light such as visible light, it is accumulated. The phosphor emits stimulated emission depending on energy. A phosphor exhibiting such a property is called a stimulable phosphor (stimulable phosphor), and by using 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) is recorded, scanned with excitation light to cause stimulated emission, and the stimulated emission light is photoelectrically read to obtain an image signal, and the image signal is processed. A method for obtaining a radiation image of a subject with good diagnostic suitability is widely known (for example, JP-A-55-12429 and JP-A-55-116340,
55-163472, 56-11395, 56-104645, etc.). This final image can be played as a hard copy or on a CRT.

As a method of reading the above-mentioned stimulated emission light, by providing photoelectric reading means for photoelectrically reading the stimulated emission light only on the side that scans the excitation light, light is emitted from one side of the stimulable phosphor sheet. There is known a method for photoelectrically reading the stimulated emission light obtained, but in addition to this method, by arranging the photoelectric reading means as described above on both sides of the stimulable phosphor sheet, the light is emitted from both sides. A double-sided condensing reading method for photoelectrically reading the generated stimulated emission light is known (for example, see JP-A-55-87970 and JP-A-56-11397).

In the method of photoelectrically reading the stimulated emission light from both sides of the stimulable phosphor sheet as described above, there are advantages that the light collection efficiency as a whole is improved and the S / N ratio is improved. .

On the other hand, it has been proposed to obtain an image with high sharpness by coloring the radiation image conversion panel (storable phosphor sheet) with a coloring agent that selectively absorbs the excitation light. (See JP-A-55-163500). The above-mentioned publication describes various embodiments in which each layer constituting the radiation image conversion panel such as a phosphor layer, a protective layer, and a support is colored. There is no mention or suggestion of how to color the.

[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 arranged on the back surface of the sheet, and is reflected there. The problem arises that That is, by the reflected and diffused excitation light, the stimulable phosphor in a portion other than the scanning point of the stimulable phosphor sheet is excited,
Excited emission light is emitted by the excitation light, and unnecessary image information is photoelectrically read from both sides, and the sharpness of the finally obtained image is lowered.

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

[0008]

A double-sided reading method of a stimulable phosphor sheet of the present invention comprises a stimulable phosphor layer, excitation light for exciting the stimulable phosphor layer, and excitation by the excitation light. Including a coloring agent that selectively absorbs the excitation light of the stimulated emission light emitted from the stimulable phosphor layer, consisting of a colored layer provided on one side of the stimulable phosphor layer, A stimulable phosphor sheet on which a radiation image is accumulated and recorded by irradiating radiation carrying radiation image information is scanned with the excitation light from the side opposite to the colored layer, and the accumulation is performed by this excitation light scanning. The photostimulable light emitted from both sides of the phosphor sheet is photoelectrically read from both sides of the stimulable phosphor sheet to obtain an image signal of the radiation image.

Here, the excitation light for exciting the stimulable phosphor layer and the excitation light of the stimulated emission light emitted from the stimulable phosphor layer by the excitation light are selectively absorbed. The colorant means a colorant which must absorb absorption of excitation light, and whose absorption is weaker than absorption of excitation light even when absorbing stimulated emission light.

The colored layer in the above-mentioned stimulable phosphor sheet may be provided in contact with the stimulable phosphor layer, or may be provided via another layer. The colored layer, for example, even if provided as a support or a protective layer in contact with the stimulable phosphor layer, it is provided as an adhesive layer for adhering the support or protective layer to the stimulable phosphor layer. Alternatively, it may be provided further outside the support or the protective layer. That is, the stimulable phosphor sheet used in the present invention may be any one as long as the colored layer is provided on one side of the stimulable phosphor layer.

[0011]

The double-sided condensing reading method of the stimulable phosphor sheet of the present invention is a stimulable phosphor sheet comprising a stimulable phosphor layer and a coloring layer containing a coloring agent that selectively absorbs excitation light. By scanning the excitation light from the side opposite to the colored layer of this sheet for double-sided condensing reading, the excitation light transmitted through the stimulable phosphor sheet is absorbed by the colored layer and is transferred to the back surface of the sheet. The component reaching the photoelectric reading means arranged is reduced, and even if a part of the excitation light is reflected by the photoelectric reading means and is incident on the sheet again, it is absorbed again in the colored layer. The component reaching the layer becomes extremely small, and it is possible to prevent the stimulable phosphor in a portion other than the scanning point of the stimulable phosphor sheet from being excited. That is, according to the method of the present invention, the sharpness of the obtained image can be efficiently improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings.

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

A protective layer 14 is provided on one surface of the stimulable phosphor layer 12, and a colored layer 16 containing a coloring agent that selectively absorbs excitation light is provided on the other surface. The arrow indicated by X in the drawing indicates the direction in which the excitation light is scanned. Here, the colored layer 16 may be a support or a protective layer depending on its thickness, function or use. The colorant contained in the colored layer 16 selectively absorbs excitation light.

FIG. 2 is a sectional view showing another example of the stimulable phosphor sheet used in the double-sided collective reading method of the stimulable phosphor sheet of the present invention.

A protective layer 24 is provided on one surface of the stimulable phosphor layer 22, a colored layer 28 containing a coloring agent that selectively absorbs excitation light is provided on the other surface, and the colored layer 28 is provided on the colored layer 28. Further, a protective layer (or support) 26 is laminated. The arrow indicated by X in the drawing indicates the direction in which the excitation light is scanned. Here, the coloring layer 28 is a protective layer (or a support).
It may be provided as an adhesive layer for adhering 26 to the stimulable phosphor layer 22 or as an intermediate layer only. Alternatively, as another embodiment of the stimulable phosphor sheet, the colored layer 28 may be provided on the surface of the protective layer (or support) 26 opposite to the stimulable phosphor layer 22.

Next, how the X-ray image of the subject is accumulated and recorded on the above-mentioned stimulable phosphor sheet will be described.

The stimulable phosphor sheet is usually housed in a cassette that shields excitation light such as visible light and is used for X-ray photography. X-ray imaging is performed with the X-ray source and the cassette containing the stimulable phosphor sheet facing each other through the object on the imaging table. At this time, in the stimulable phosphor sheet contained in the cassette, the colored 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 onto the stimulable phosphor sheet housed in the cassette, so that the 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 device for photoelectrically reading the X-ray image from the stimulable phosphor sheet 10 on which the X-ray image is stored and recorded as described above.

The stimulable phosphor sheet 10 has endless belts 49a, 49 which are rotated by a motor (not shown).
The colored layer is arranged on the upper side of b. A laser light source 41 that emits excitation light is provided above the sheet 10.
And a rotary polygon mirror 43 that reflects and deflects the laser light to perform main scanning of the sheet 10, and a motor that rotates the rotary polygon mirror 43.
42 and are arranged. Furthermore, above the position where the laser light is scanned, a light guide 45a for concentrating the stimulated emission light emitted by the scanning of the laser light from above is arranged closely, and below the position, A light guide 45b for collecting the stimulated emission light from below is arranged vertically to the sheet 10. Photomultipliers (photomultiplier tubes) 46a and 46b for photoelectrically detecting stimulated emission light are connected to the light guides 45a and 45b, respectively. The photomultipliers 46a and 46b are connected to logarithmic amplifiers 47a and 47b, and the logarithmic amplifiers 47a and 47b are connected to the storage device 48.
It is connected to the.

Next, the manner of reading an X-ray image from the stimulable phosphor sheet by this X-ray image reading device will be described with reference to FIG. The X-ray imaging as described above is performed, and the 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 the endless belts 49a and 49b. The stimulable phosphor sheet 10 set at this predetermined position is conveyed (sub-scanned) in the arrow Y direction by its endless belts 49a and 49b. On the other hand, the light beam emitted from the laser light source 41 is reflected and deflected by a rotary polygon mirror 43 driven by a motor 42 and rotating at a high speed in the arrow direction, and enters the sheet 10 and is substantially perpendicular to the sub-scanning direction (arrow Y direction). The main scanning is performed in the arrow X direction. From the portion of the sheet 10 irradiated with this light beam, the stimulated emission light 44a, 44b (here, the stimulated emission light 44a, 44b) is emitted in a quantity of light according to the accumulated and recorded X-ray image information.
44b indicates the light emitted from above and below the seat 10). This stimulated emission light 44a is guided by a light guide 45a and photoelectrically detected by a photomultiplier (photomultiplier tube) 46a. The light guide 45a is formed by molding a light guide material such as an acrylic plate, and is arranged so that the linear incident end face extends along the main scanning line on the stimulable phosphor sheet 10. , The photomultiplier 46a is formed on the emission end face formed in an annular shape.
The light receiving surfaces of are combined. Light guide from the incident end face
The stimulated emission light 44a incident on the inside of the light guide 45a travels through the inside of the light guide 45a by repeating total reflection, is emitted from the emission end face and is received by the photomultiplier 46a, and the stimulated emission light 44a representing the radiation image is emitted. Light multiplier is photomultiplier 46a
Is converted into an electric signal by. Similarly, stimulated emission light 44
b is guided by a light guide 45b and photoelectrically detected by a photomultiplier (photomultiplier tube) 46b.

Here, the stimulable phosphor sheet 10 used in the present invention has a coloring layer 16 containing a coloring agent that selectively absorbs excitation light. This stimulable phosphor sheet 10
Is arranged so that the colored layer 16 is on the lower side in order to scan the excitation light from the side opposite to the colored layer of the sheet 10. Therefore, the excitation light emitted from the laser light source 41 and transmitted through the protective layer 14 and the stimulable phosphor layer 12 is the sheet 10
Is absorbed by the colored layer 16 of. Further, even if the excitation light is emitted to the back side of the sheet 10 and reflected by the photoelectric reading means arranged on the back side of the sheet, it is absorbed by the coloring layer when it is incident on the sheet again.

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 the A / D converter in the storage device 48 to obtain the first image signal. Here again, 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
The image signal of 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 way, the stimulated emission light emitted by the irradiation of the excitation light is collected from both sides, so that the light collection 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 in which the influence of the excitation light reflected and diffused by the light guide 45b is removed as described above, the double-sided collective reading from the conventional stimulable phosphor sheet is performed. An image with improved sharpness can be obtained as compared with.

Incidentally, conventionally, a stimulable phosphor sheet obtained by coloring the stimulable phosphor layer with the above colorant has been widely put to practical use, but when performing double-sided condensing reading using this stimulable phosphor sheet. When comparing the present invention with the present invention, in the former case, the colored stimulable phosphor layer absorbs the excitation light transmitted through the stimulable phosphor sheet, and reduces the influence of the excitation light reflection in the photoelectric reading means, and thus is obtained. Although the sharpness of the image is improved to the same level as in the present invention, the colorant in the stimulable phosphor layer also reduces the excitation light that is directly incident on the stimulable phosphor layer by scanning, and thus stimulated emission The amount of light is reduced, and the S / N ratio is lower than that of the image obtained by the double-sided condensing reading method of the present invention.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing an example of a stimulable phosphor sheet used in the double-sided collective reading method of the stimulable phosphor sheet of the present invention.

FIG. 3 is a schematic diagram showing an example of an X-ray image reading apparatus.

[Explanation of symbols]

 10, 20 stimulable phosphor sheet 12, 22 stimulable phosphor layer 14, 24, 26 protective layer 16, 28 colored layer 40 X-ray image reading device 44 stimulated emission light 45 light guide 46 photomultiplier 47 logarithmic converter 48 storage device 49 endless belt

Claims (1)

[Claims] 1. A stimulable phosphor layer, and excitation light for exciting the stimulable phosphor layer, and the excitation of stimulated emission light emitted from the stimulable phosphor layer by excitation by the excitation light. It comprises a coloring layer provided on one side of the stimulable phosphor layer containing a coloring agent that selectively absorbs light, and a radiation image is accumulated and recorded by irradiating radiation carrying radiation image information. The stimulable phosphor sheet is scanned with the excitation light from the side opposite to the colored layer, and the stimulated emission light emitted from both sides of the stimulable phosphor sheet by this excitation light scanning is accumulated. Double-sided condensing reading method for a stimulable phosphor sheet by photoelectrically reading from both sides of the luminescent phosphor sheet to obtain the image signal of the radiation image.