JPH05207998A - Radiation image reader - Google Patents

Abstract

PURPOSE:To secure the same S/N and resolution on both end parts, as well, in the main scanning direction as the center by curving a stimulable phosphor, and always irradiating vertically the stimulable phosphor with an excitation light beam. CONSTITUTION:This reader is provided with plural pressing/carrying rollers 408 in which the diameter of the center part is increased successively as it approaches a scanning position 407 and the diameter of the center part is decreased as it goes away from the scanning position 407. A guide plate 409 is formed so that the curvature of the plate 409 becomes gradually larger as it approaches the scanning position 407, and also, its curvature is determined so that a laser beam is always made incident vertically on a stimulable phosphor sheet 401 moving in the direction A while pressed against its surface at the scanning position 407. In such a way, a positional deviation of an excited point and an expansion of the spot diameter are prevented irrespective of being the center part or both end parts in the main scanning direction. Both end parts of the stimulable phosphor sheet 401 can also obtain an image signal S of the same S/N as the center part, and accordingly, resolution of all positions becomes the same, and a satisfactory resolution is obtained over the whole of reproducing image.

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 apparatus using a photostimulable phosphor, and more particularly to a radiation image reading apparatus having a devised excitation light irradiation structure.

[0002]

2. Description of the Related Art In recent years, a radiographic image is recorded on an X-ray film or the like, and the film on which the radiographic image is recorded is used as it is for observation and diagnosis. The stimulated phosphor sheet (including the panel) is irradiated with radiation that has passed through the subject to store and record a radiation image in the stimulated phosphor, and then the radiation image is photoelectrically read to obtain an image signal, 2. Description of the Related Art A system for obtaining a reproduced image after subjecting an image signal to appropriate image processing has been used. The basic method of the system using this stimulable phosphor sheet is described in detail in US Pat. No. 3,859,527. Here, the stimulable phosphor means that when irradiated with radiation such as X-rays, α-rays, β-rays, and γ-rays, a part of the energy of the radiation is accumulated inside for a while, and infrared light, A phosphor that emits accumulated energy as stimulated emission light when irradiated with excitation light such as visible light or ultraviolet light. Depending on the type of the phosphor, the type of radiation that easily accumulates energy, stimulated emission light The wavelength of the excitation light that easily emits, the wavelength of the emitted stimulated emission light, and the like are different.

In the system using this stimulable phosphor sheet, the energy of the radiation applied to the stimulable phosphor sheet and the amount of the stimulated emission light emitted by the irradiation of the excitation light are in a wide energy range. It is recognized that they are proportional to each other, and this ratio can be changed depending on the light amount of the excitation light, so that a radiographic image that is not affected by fluctuations in the radiation exposure amount can be obtained. Further, in a system for obtaining an X-ray image of a human body, it is possible to reduce the exposure dose of the human body in X-ray photography.

FIG. 8 is a diagram schematically showing an example of a conventional device using a stimulated phosphor sheet. For example, an X-ray image of a chest of a human body is taken by an X-ray imaging apparatus (not shown), and the X-rays transmitted through the chest are irradiated to the photostimulable phosphor sheet 100, and the photostimulated phosphor sheet 100 is irradiated with the X-ray of the chest. The image is accumulated and recorded. The photostimulable phosphor panel 100 on which the X-ray image is accumulated and recorded is set at a predetermined position in the apparatus shown in FIG. 8 and conveyed (sub-scanning) in the arrow Y direction.

During this conveyance (sub-scanning), the laser beam 10 as the excitation light emitted from the laser beam 101 is also used.
2 is repeatedly reflected and deflected by a scanner 103 such as a galvanometer mirror or a rotary polygon mirror (polygon mirror), passes through a beam shape correction optical system 104 such as an fθ lens, and is further reflected by a reflection mirror 105. The sheet 100 is irradiated with the light, so that the photostimulable phosphor sheet 100 is repeatedly scanned (main scanning) in the arrow X direction by the laser beam 102. From each point of this scanning, stimulated emission light carrying the X-ray image accumulated and recorded on the stimulated phosphor sheet 100 is emitted. The stimulated emission light is condensed by a condenser 106 such as an optical fiber array, passes through an optical filter 107 that cuts the excitation light and transmits the stimulated emission light, and a photoelectric converter such as a photomultiplier tube. It is guided to 108 and converted into an electric signal. still,
An optical filter that transmits only the stimulated emission light is attached to the front surface without using the condenser 106, for example.
The light may be directly received using a CD optical sensor or the like.

The electric signal obtained by the photoelectric converter 108 is logarithmically amplified by the logarithmic amplifier 109 and then converted into a digital image signal S by the A / D converter 110. The digital image signal S is temporarily stored in the frame memory 111 and then stored in the storage medium 112 such as a magnetic disk or an optical disk. Then this storage medium 112
The image signal S stored in the
The image signal S input to the image processing unit 113 is subjected to image processing such as frequency processing. The image signal after the image processing is sent to the image display unit 114 such as a CRT display device, and the X-ray image as a visible image is reproduced and displayed on the image display unit 114. An image recording device such as a laser printer (not shown) is provided instead of or together with the image display unit 114 that displays an image, and an X-ray image is reproduced and recorded on, for example, a silver salt film. You may make it obtain the X-ray image as a visible image by developing.

[0007]

FIG. 9 is a schematic view showing how the stimulated phosphor sheet 100 is irradiated with the laser beam 102 in the conventional apparatus shown in FIG. The stimulable phosphor sheet 100 has a structure in which a stimulable phosphor layer 202 is formed on a base 201 such as a plastic sheet, and a protective film 203 is formed on the stimulable phosphor layer 202. .. Here, each block separated by broken lines shown in the stimulated phosphor layer 202 ... M, m + 1, ...
n, n + 1, ... Represent pixels corresponding to each image signal S obtained by the A / D converter 110 (see FIG. 8).

When the laser beam 102 irradiates the pixel n, the photostimulable phosphor sheet 100 is vertically irradiated. Therefore, the laser beam 102 irradiates only the pixel n. When irradiating m, the laser beam 102 is obliquely incident on the photostimulable phosphor sheet 100, so that the pixel m + 1 adjacent to the pixel m is also irradiated, whereby the pixel m is photostimulated from both the pixel m + 1 and the pixel m + 1. The light 301 is emitted, so that the position of the excited point is displaced, and the spot diameter of the laser beam is expanded. The positional displacement and the spread of the spot diameter are caused by the main scanning of the photostimulable phosphor sheet 100. It becomes larger as it gets closer to both ends of the direction. Due to this positional shift and the spread of the spot diameter, the amount of stimulated emission light 301 from a point other than the target point increases, and as a result, the S / N ratio decreases as it approaches both ends in the main scanning direction. It caused a decrease in resolution.

In view of the above circumstances, it is an object of the present invention to provide a radiographic image reading apparatus in which both end portions have the same S / N ratio and resolution as the central portion.

[0010]

FIG. 1 is a diagram showing the principle of the present invention. In this figure, each element corresponding to each element shown in FIG. 8 is given the same number as that given in FIG. 8, and only the differences will be described. The stimulable phosphor sheet 100 shown in FIG. 1 is curved so that any of the pixels, ..., M, m + 1, ..., N, n + 1 ,. The flexibility, hardness, etc. of the photostimulable phosphor sheet 100 can be freely adjusted by selecting the material used. By bending the stimulable phosphor sheet 100 in this manner, a constant S / N ratio and a constant resolution in the main scanning direction are always ensured.

That is, the radiation image reading apparatus of the present invention for achieving the above-mentioned object comprises a main scanning means for repeatedly scanning the stimulable phosphor on which a radiation image is stored and recorded in the main scanning direction with a main scanning means. An image signal for carrying the radiation image by receiving the stimulated emission light emitted from each scanning point by the excitation light beam and the sub-scanning means for relatively moving the stimulated phosphor or the excitation light in the sub-scanning direction. In a radiation image reading apparatus having a photoelectric reading means for obtaining the photoelectric conversion means, a bending means for bending the stimulable phosphor so that the excitation light beam always irradiates the stimulable phosphor vertically is provided. It is a feature.

The bending means is not limited to a specific structure in the present invention. For example, (1) the stimulable phosphor is formed into an endless belt or a part of the endless belt. When formed into a shape, the bending means gradually moves the photostimulable phosphor that is relatively moved in the sub-scanning direction from the upstream side toward the scanning position where the photostimulable phosphor scans the excitation light beam. It may be curved and gradually flattened from the scanning position toward the downstream side, or (2) when the stimulable phosphor is formed into a sheet, A pressing member that pushes the body from the front surface side where the excitation light beam is irradiated to the photostimulable phosphor, a guide member that supports the back surface of the photostimulable phosphor in an arc shape, and a main scanning direction of the photostimulable phosphor. Support both ends of the firefly The bending means may include a pressing and holding member that holds the body in a state of being pressed against the guide member, and (3) the stimulated phosphor is formed into a sheet having a magnetic layer. The bending means may be configured to include a guide member that supports the back surface of the photostimulable phosphor in an arc shape, and an electromagnet that draws the photostimulable phosphor to the guide member.

[0013]

Since the radiation image reading apparatus of the present invention is provided with the above-mentioned bending means, it is possible to prevent the positional deviation of the excited point regardless of whether it is at the center or both ends in the main scanning direction. The spread of the spot diameter is prevented, and as a result, a constant and good S / N ratio and resolution are always secured as described above.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram schematically showing the entire system for obtaining an X-ray image of a human body, which includes the X-ray image reading apparatus according to the first embodiment of the present invention. An imaging recording unit 2 of the X-ray image reading apparatus 2 between the X-ray generation apparatus 1 and the X-ray image reading apparatus 2.
An object 3 is placed in front of the object 1. In this state, X-rays 4 are emitted from the X-ray generator 1, and the X-rays that have passed through the subject 3 are applied to a photostimulable phosphor sheet (not shown) provided in the photographing and recording section 21. The X-ray image of the subject 3 is accumulated and recorded on the sheet.

Further, a reading unit (not shown) is provided in the X-ray image reading apparatus 2, and after the photographing, the photostimulable phosphor plate sheet is scanned by laser light as excitation light and emitted from each scanning point. The stimulated emission light thus generated is photoelectrically read and A / D converted to generate a digital image signal S. The image signal S is input to the image processing apparatus 5 and subjected to various image processing such as frequency enhancement processing, and then the CRT.
The visible image based on this image signal is reproduced and displayed by being input to the image display device 6 such as an image display device.

FIG. 3 is a perspective view showing a schematic internal structure of the X-ray image reading apparatus according to the first embodiment of the present invention. The radiation image reading apparatus 2 is provided with a photostimulable phosphor sheet 401 formed in an endless belt shape, and rollers 404, 404; 4 rotated by motors (not shown) incorporated in motor boxes 402, 403.
It has been passed over 05,405. When shooting is performed as shown in FIG. 2, the subject 3 on the front surface of the shooting / recording unit 21 is captured.
X-rays that have passed through (see FIG. 2) are stimulated phosphor sheet 401.
The part 401a arranged in the photographing and recording section 21 is irradiated with the X-ray image of the subject 3 in the part 401a. When shooting is done in this way,
The rollers 403 and 404 rotate, which causes the photostimulable phosphor sheet 401 to move in the direction of arrow A.

On the other hand, in the optical box 406, the laser light source 101 and the scanner 10 such as a rotary polygon mirror shown in FIG.
3, the beam shape correction optical system 105 such as an fθ lens and the like are provided, and the photostimulable phosphor sheet 401 is repeatedly scanned in the width direction by the laser beam 102 (see FIG. 8) at a predetermined scanning position 407. To be scanned. Here, in the radiation image reading apparatus 2, a plurality of pressing / conveying rollers 408 in which the diameter of the central portion gradually increases as the scanning position 407 approaches, and the diameter of the central portion decreases as the distance from the scanning position 407 increases. Is equipped,
The vicinity 401 of the scanning position 407 of the stimulated phosphor sheet 401
b is the guide plate 4 by these pressing and conveying rollers 408.
It is pressed against 09. The guide plate 409 is formed such that its curvature gradually increases as it approaches the scanning position 407, and at the scanning position 407, the photostimulable phosphor sheet 4 pressed against the surface thereof.
The curvature is set so that the laser beam 102 (refer to FIG. 8) is always vertically incident on 01.

The photostimulable phosphor sheet 401 is conveyed in the direction of arrow A, and the portion 40 arranged in the photographing / recording section 21 at the time of photographing.
When 1a reaches the scanning position 407, the stimulated emission sheet 401 emits stimulated emission light by the scanning of the laser beam 102, and the incident end face 410a is circled so as to be along the excitation phosphor sheet 401 at the scanning position 407. An image signal S is generated by being condensed by a condensing body 410 such as an optical fiber array formed in an arc shape and being received by a photoelectric reader 411 such as a photomultiplier tube. This image signal S is transmitted to the image processing device 5 as shown in FIG.

In the read portion, residual energy (afterimage) is erased by the erasing light emitted from the light source built in the erasing light source box 412, and the reusable state is restored. Thus, the X shown in FIG.
In the line image reading device 2, the photostimulable phosphor sheet 401 is formed in an endless belt shape, and the photostimulable phosphor sheet is conveyed in the direction of arrow A, and is guided by the guide plate 409 and the pressing conveyance roller 40.
8 is configured to gradually bend from the upstream side toward the scanning position 407 and to be gradually flattened from the scanning position 407 toward the downstream side, whereby the laser beam always vertically moves the stimulable phosphor sheet 401. Since the image signal S having the same S / N ratio as the central portion is obtained even at both end portions of the photostimulable phosphor sheet 401, the resolution on the end portion side is the central resolution. Therefore, a good resolution can be obtained over the entire reproduced image.

Although the photostimulable phosphor sheet 401 itself is formed as an endless belt here, the photostimulable phosphor sheet itself constitutes a part of the endless belt or the endless belt. Of course, it may be a sheet attached to a part. FIG. 4 shows the X according to the second embodiment of the present invention.
It is a perspective view showing the schematic structure inside a line image reading device.

The X-ray image reading apparatus 2'is provided with a photostimulable phosphor sheet 501. The photostimulable phosphor sheet 501 is first placed in the photographing and recording section 21 ', and an X-ray image of the subject is stored and recorded on the photostimulable phosphor sheet 501 (see FIG. 2). Then this stimulated phosphor sheet 501
Shows a state in which the conveying roller 503 rotated by a conveying means (not shown) and a motor built in the motor box 502, and the deflecting roller 504 are suspended from the deflecting roller 504 as shown by a chain line in FIG. Is moved in the direction of arrow A shown in FIG. 3B, is transferred to the pressing rotation roller 505, and is moved to the position of the photostimulable phosphor 501 shown by the solid line in the figure. The pressing rotation roller 505 is used for the motor box 5
The photostimulable phosphor sheet 501 is rotated by a motor built in the No. 07, and the arc-shaped guide surface 50 of the guide member 506.
6a is moved while being pressed.

When the photostimulable phosphor sheet 501 is conveyed to the position shown by the solid line in the figure, it is mounted on the optical box 508 having the pressing member 510 at the tip by the moving means (not shown), the condensing body 509, and the optical box 508. The erasing light source box 514 placed on the guide surface 50 of the guide member 506 moves the photostimulable phosphor sheet 501 in the direction of arrow C shown in the figure.
Push to the 6a side. After that, the screw rod 512 is rotated by the rotation of the motor built in the motor box 511, whereby the pressing holding member 513 is moved in the directions of the arrows B and B ′, whereby the photostimulable phosphor sheet 501 is guided to the guide surface. It is held in a state of being completely pressed against 506a.
After that, the pressing rotation roller 507 is further rotated in the direction of arrow D to be separated from the photostimulable phosphor sheet 501.

FIG. 5 shows a state in which the photostimulable phosphor sheet 501 is pressed against the guide surface 506a, which is shown in FIG.
It is the figure seen and shown from the direction. As shown in this figure, by pressing the stimulable phosphor sheet 501 against the arc-shaped guide surface 506a of the guide member 506, the excitation laser beam 102 always irradiates the stimulable phosphor sheet 501 vertically. ..

Returning to FIG. 4, the description will be continued. The optical box 508 is provided with a laser light source 101, a scanner 103 such as a rotating polygon mirror, a beam correction optical system 105 such as an fθ lens, and the like shown in FIG.
1 is repeatedly scanned in the width direction by a laser beam 102 (see FIG. 8). The optical box 508 and the light collector 509 first move upward in the figure to a position where the upper end of the photostimulable phosphor sheet 501 is scanned, and then move downward and the above scanning is repeatedly performed, which results in bright emission. The entire surface of the exhaust phosphor sheet 501 is scanned by the laser beam 102. When the stimulated phosphor sheet 501 is scanned by the laser beam 102, stimulated emission light is emitted from the stimulated phosphor sheet 501 and condensed by the light collector 509.
An image signal S is generated by being received by the photoelectric reader 515. This image signal S is generated by the image processing device 5 as shown in FIG.
Be transmitted to. When this reading is completed, the erasing light source built in the erasing light source box 514 mounted on the optical box 508 is turned on, and in that state, the optical box 508 is lit.
Etc. move upward, and as a result, the stimulated phosphor sheet 501
The energy (afterimage) remaining in is erased. When the erasing of the afterimage is completed, the pressing rotation roller 505 rotates in the direction opposite to the arrow D and comes into contact with the photostimulable phosphor sheet 501, and the optical box 508 and the like move in the direction opposite to the arrow C and hold by pressing. The member 513 moves in the direction opposite to the arrows B and B ′, the pressing rotation roller 505 rotates, moves the photostimulable phosphor sheet 501 upward, and transfers it to the conveyance roller 503. The photostimulable phosphor 501 is further transported through the state shown by the one-dot chain line in the figure, placed in the photographing recording section 21 ', and reused for the next photographing.

As described above, in the radiation image reading apparatus 2'shown in FIGS. 4 and 5, the photostimulable phosphor sheet 501 is pressed against the guide member 506 so that the laser beam 102 is always vertically irradiated. Since the reading is performed by bending the curved surface, the same S / N ratio as that of the central portion of the photostimulable phosphor sheet 401 is the same as that of the first embodiment (see FIG. 3). The image signal S is obtained, whereby the resolution on the edge side of the reproduced image becomes the same as the resolution at the center, and good resolution can be obtained over the entire reproduced image.

FIG. 6 is a view showing the structure of the photostimulable phosphor sheet according to the third embodiment of the present invention. In the stimulated phosphor sheet 800 shown in FIG. 6, a lead particle layer 801 is formed on a base 201 such as a plastic sheet, a stimulated phosphor layer 202 is formed thereon, and a protective film 201 is further formed thereon. Has been done. The formation of this lead particle layer 801 prevents halation of X-rays irradiated from above in the drawing. A magnetic film 802 is formed on the back surface side of the base 201.

FIG. 7 is a view corresponding to FIG. 5 in the second embodiment, which shows the characterizing portion of the third embodiment of the present invention. In FIG. 7, elements corresponding to those shown in FIG. 5 are designated by the same numbers as those given in FIG. 5 regardless of the difference in detailed structure. An electromagnet 515 is embedded along the arc-shaped guide surface 506a of the guide member 506 shown in FIG. 7. When electric power is applied to this electromagnet, the stimulated phosphor sheet 800 having the structure of FIG.
Are attracted to this electromagnet 515. In this state, the pressing holding member 513 moves in the directions of arrows B and B ′ to hold the photostimulable phosphor sheet 800 pressed against the guide surface 506a of the guide member 506. Since the other structures in the third embodiment are the same as those in the second embodiment described above, the duplicate description will be omitted here. in this way,
Instead of the pressing member 501 shown in FIG. 5, a magnetic force may be used.

[0028]

As described above in detail, in the radiation image reading apparatus of the present invention, the bending means for bending the stimulable phosphor so that the excitation light beam always irradiates the stimulable phosphor vertically. Therefore, the same S / N ratio and resolution as those of the central portion are secured at both ends in the main scanning direction. The bending means is not limited to a specific structure, but can be variously structured as described above.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is a diagram schematically showing the entire system for obtaining an X-ray image of a human body, which includes the X-ray image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a schematic configuration of the inside of the X-ray image reading apparatus according to the first embodiment of the present invention.

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

5 is a diagram showing a state in which a stimulated phosphor sheet 501 is pressed against a guide surface 506a as viewed in the XX direction shown in FIG.

FIG. 6 is a view showing a structure of a photostimulable phosphor sheet according to a third embodiment of the present invention.

FIG. 7 is a view showing a characteristic part of a third embodiment of the present invention and corresponding to FIG. 5 in the second embodiment.

FIG. 8 is a diagram showing an example of a conventional device using a stimulated phosphor sheet.

FIG. 9 is a schematic diagram showing how the stimulated phosphor sheet is irradiated with a laser beam in the conventional apparatus shown in FIG.

[Explanation of symbols]

 2, 2'X-ray image reading device 21, 21 'Imaging recording unit 100 Photostimulated phosphor sheet 102 Laser beam 201 Base 202 Photostimulated phosphor layer 203 Protective film 401 Endless belt-shaped photostimulable phosphor sheet 408 Pressing rotation roller 409 Guide plate 501 Photostimulated phosphor sheet 506 Guide member 510 Press member 513 Press holding member 802 Magnetic layer

Claims (4)

[Claims] 1. A main scanning means for repeatedly scanning an excitation light beam in a main scanning direction on a stimulable phosphor on which a radiation image is stored and recorded, and relative to the stimulable phosphor or the excitation light in a sub-scanning direction. In a radiographic image reading device comprising a sub-scanning unit for moving, and a photoelectric reading unit for receiving an image signal carrying the radiation image by receiving stimulated emission light emitted from each scanning point by the excitation light beam, A radiation image reading apparatus comprising bending means for bending the stimulable phosphor so that the excitation light beam always irradiates the stimulable phosphor vertically. 2. The stimulable phosphor is formed in an endless belt shape or a sheet shape on a part of the endless belt, and the bending means is configured to move the stimulable phosphor relatively in the sub-scanning direction. The stimulable phosphor is to be gradually curved from the upstream side toward the scanning position or the downstream side where the excitation light beam is scanned, and is gradually flattened from the scanning position toward the downstream side. The radiation image reading apparatus according to claim 1, wherein the radiation image reading apparatus is a feature. 3. The pressing member, wherein the photostimulable phosphor is formed in a sheet shape, and the bending means presses the photostimulable phosphor from the surface side where the photostimulable phosphor is irradiated with the excitation light beam. And a guide member that supports the back surface of the stimulated phosphor in an arc shape, and a pressing member that supports both ends of the stimulated phosphor in the main scanning direction and holds the stimulated phosphor in a state of being pressed against the guide member. The radiation image reading apparatus according to claim 1, further comprising a holding member. 4. The stimulated phosphor is formed into a sheet having a magnetic layer, and the bending means supports the back surface of the stimulated phosphor in an arc shape, and the stimulated phosphor. An electromagnet for attracting a body to the guide member is provided.
The radiographic image reading device described.