JP2004212524A - Radiography reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiography reader capable of accurately reading an image while image quality is not affected by vibration or the like generated by a scanning means. <P>SOLUTION: The radiography reader where the recording surface of a stimulable phosphor sheet or a stimulable phosphor plate on which the radiography is recorded is scanned with stimulating light and stimulated luminescence generated on the stimulable phosphor plate by the stimulating light is read is provided with a carriage for holding the stimulable phosphor sheet or the stimulable phosphor plate in a horizontal direction, a subscanning means for moving the carriage by a driving roller while linearly guiding the carriage in the horizontal direction by a guide means, and a stimulating means for stimulating and emitting radiation image information accumulated and recorded on the stimulable phosphor plate by radiating the stimulating light to scan in the horizontal direction nearly orthogonal to a subscanning direction on the stimulable phosphor sheet or the stimulable phosphor plate. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation image reading apparatus that reads radiation image information as stimulated emission, and more particularly, to a radiation image reading apparatus that can read with high accuracy.
[0002]
[Prior art]
Radiation images such as X-ray images are often used for diagnosis of diseases. Conventionally, in order to obtain such a radiation image, X-rays transmitted through a subject are irradiated on a phosphor layer (fluorescent screen) to generate visible light, and this visible light is irradiated on a silver halide film, This silver halide film was developed and used as a radiograph.
[0003]
However, in recent years, techniques have been devised for directly taking an image from the phosphor layer without using a film coated with a silver salt.
[0004]
That is, by irradiating the subject with X-rays emitted from the X-ray source and further causing the X-rays transmitted through the subject to enter the stimulable phosphor plate, the latent image of the image of the subject is converted to the stimulable phosphor plate. Formed. Then, the recording surface of the stimulable phosphor plate on which the radiation image is recorded is excited by light or heat so that the accumulated radiation energy is emitted as fluorescence, and the fluorescence is detected and imaged. Has been devised. This type of technique is described in U.S. Pat. No. 3,585,527 and JP-A-55-12144.
[0005]
The technique described in these documents uses a stimulable phosphor plate having a stimulable phosphor layer formed on a support, and irradiates the phosphor layer of the stimulable phosphor plate with radiation. To form a latent image. Then, the phosphor layer is irradiated with excitation light to generate stimulated emission according to the latent image, and the stimulated emission is photoelectrically converted by a photomultiplier or the like to generate image data to obtain a radiation image. ing.
[0006]
The radiation image is visualized by outputting the image data of the radiation image thus obtained to a silver halide film or displaying it on a CRT display. It is also possible to store the image data in various storage devices and take it out as needed to visualize it.
[0007]
By the way, when scanning the stimulable phosphor plate with the excitation light, the excitation light must be precisely moved relative to the stimulable phosphor plate at a constant speed. For this reason, in the prior art, Japanese Patent Application Laid-Open Nos. 62-2770 and 11-305362 (Patent Document 1) disclose excitation light in the main scanning direction using a deflecting means such as a polygon mirror or a galvanometer mirror. There has been proposed a method of driving in a sub-scanning direction by using a ball screw while scanning and guiding an excitation light source and a stimulated emission light receiving unit by a linear motion guide.
[0008]
[Patent Document 1]
JP-A-11-305362 (pages 4 to 7, FIG. 12)
[0009]
[Problems to be solved by the invention]
In the drive using the linear motion guide and the ball screw as described above, there is a known problem that it is difficult to move at a constant speed unless the parallelism between the linear motion guide and the ball screw is made precise. If high-precision parts (motor, drive mechanism, etc.) are used to solve such a problem, there is a problem that the apparatus becomes expensive.
[0010]
Therefore, Japanese Patent Application Laid-Open No. 2002-277999 discloses a method in which a stimulable phosphor plate and a counterweight of the same weight are driven vertically in a sub-scanning direction via a belt (hereinafter referred to as a vertical suspension driving method). Is described.
[0011]
In this vertical suspension drive system, the total weight can be more than ten kilograms due to the stimulable phosphor plate and the adsorption plate that holds the stimulable phosphor plate while adsorbing the same, and the counterweight of the same weight. is there. When these are driven in a vertical direction at a low speed via a belt, vibration occurs.
[0012]
Then, this vibration affects the irradiation of the excitation light, and the reading of the stimulated emission is included as image unevenness. In particular, in a low-speed conveyance state of 10 mm / s or less, the belt vibration becomes remarkable, and as a result, a problem arises that the image unevenness included in the radiation image information becomes remarkable.
[0013]
Note that the vibration generated in the belt is generated as a natural vibration according to the weight of the stimulable phosphor plate, the suction plate, and the counterweight. Further, there is a problem that this image unevenness occurs in a region having a relatively high visibility.
[0014]
The present invention has been made in view of the above problems, and realizes a radiation image reading apparatus capable of reading an image with high accuracy without being affected by image quality due to vibration or the like generated by a scanning unit. The purpose is to:
[0015]
[Means for Solving the Problems]
That is, the present invention that solves the above-described problems is described below.
[0016]
(1) The invention according to claim 1 is to scan a recording surface of a stimulable phosphor sheet or a stimulable phosphor plate on which a radiation image is recorded by excitation light, and to stimulate the stimulable phosphor plate by the excitation light. A radiation image reading apparatus that reads stimulable luminescence generated in a stimulable phosphor sheet or a stimulable phosphor plate in a horizontal direction by a guide that holds the stimulable phosphor sheet or the stimulable phosphor plate in a horizontal direction by guide means. A sub-scanning means for moving the transfer table by a driving roller while guiding the sheet, and scanning the stimulable phosphor sheet or the stimulable phosphor plate in a horizontal direction substantially orthogonal to the sub-scanning direction. An excitation means for irradiating the excitation light and causing the radiation image information stored and recorded on the stimulable phosphor plate to emit stimulating light, .
[0017]
According to the present invention, the recording surface of the stimulable phosphor sheet or the stimulable phosphor plate on which the radiation image is recorded is scanned by the excitation light, and the stimulable luminescence generated on the stimulable phosphor plate by the excitation light is read. At this time, the stimulable phosphor sheet or the stimulable phosphor plate is held in the horizontal direction by the carrier, and the carrier is guided linearly in the horizontal direction by the guide means, while being driven in the sub-scanning direction by the drive roller. Move. Then, along with the movement in the sub-scanning direction, the stimulable phosphor sheet or the stimulable phosphor plate is irradiated with excitation light that scans in a horizontal direction substantially perpendicular to the sub-scanning direction, thereby stimulating the stimulable phosphor sheet. The radiation image information stored and recorded on the body plate is stimulated to emit light.
[0018]
In this radiation image reading apparatus, as the sub-scanning, the stimulable phosphor sheet or the stimulable phosphor plate is conveyed in the horizontal direction by the driving roller, so that vibration such as a ball screw does not occur, and There is no need to strictly control the parallelism between the linear motion guide and the ball screw. Further, since the counterweight required for the vertical suspension driving method is not required, the frequency of natural vibration increases, and image unevenness occurs at a spatial frequency with low visibility. As a result, it is possible to read an image with high accuracy without being affected by the vibration or the like generated by the scanning means.
[0019]
(2) The radiation image reading apparatus according to (1), wherein the driving roller of the sub-scanning means has an elastic member at least on a surface portion in contact with the transport table. .
[0020]
According to the present invention, in the above (1), by having an elastic member on the surface portion as the drive roller, it is possible to further reduce vibration and suppress the influence on image quality. Note that rubber is preferably used as the elastic member. In addition, not only the surface of the drive roller, but also the entire or most of the drive roller is made of an elastic member such as rubber, so that it has a sufficient frictional force for driving, and further reduces vibration to improve image quality. Can be suppressed.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the contents and numerical values of the specific examples described in the embodiments below.
[0022]
<Radiation image reading apparatus according to first embodiment>
FIG. 1 is a block diagram illustrating functional blocks of a radiation image reading apparatus 100 according to a first embodiment of the present invention.
[0023]
FIG. 2 is a side view showing a mechanical configuration of a main part of the radiation image reading apparatus 100 according to the present embodiment.
[0024]
In FIGS. 1 and 2, for convenience, the main scanning direction perpendicular to the paper surface is the y direction, the horizontal sub-scanning direction is the x direction, and the direction perpendicular to both the main scanning direction and the sub-scanning direction (upper side). Is described in the z direction.
[0025]
1 and 2, light-shielding members and the like for shielding the entire device from light are omitted, and the inside is shown.
[0026]
In the radiation image reading apparatus 100, reference numeral 101 denotes a control unit for controlling the entire radiation image reading apparatus 100, and 110 denotes a stimulable phosphor that absorbs radiation from a radiation source that has passed through a subject, thereby obtaining radiation image information. This is a stimulable phosphor plate for storing and recording.
[0027]
Reference numeral 111 denotes a transfer table serving as a table for transferring the stimulable phosphor sheet or the stimulable phosphor plate. Here, it is desirable that the stimulable phosphor plate 110 is positioned and held and fixed in the horizontal direction on the carrier 111 by a rubber magnet or the like.
[0028]
It should be noted that the stimulable phosphor sheet for storing and recording radiation image information has no rigidity by itself and is difficult to handle. Therefore, it is rare to handle it alone. Therefore, it is often handled while being held, for example, by being adhered to a supporting member such as a metal plate or a resin plate, or to a back plate of a cassette for storage. In this specification, the stimulable phosphor sheet held by any member will be referred to as a stimulable phosphor plate. However, in the present embodiment, the stimulable phosphor sheet can be transported while being held on the transport table 111.
[0029]
Reference numeral 120 denotes an optical unit in which excitation means 140 for generating excitation light and photoelectric conversion means 150 for reading stimulated emission are integrally formed. In this embodiment, the optical unit 120 is fixed.
[0030]
A sub-scanning unit 130 moves the excitation unit 140 and the photoelectric conversion unit 150 in the sub-scanning direction (x direction). The sub-scanning means 130 includes a sub-scanning linear motion guide rail 131 serving as a guide means for guiding the transport table 111 for performing sub-scanning, and a sub-scanning linear motion guide 132 moving on the sub-scanning linear motion guide rail 131. It is composed of The transfer table 111 is mounted on the sub-scanning linear motion guide 132.
[0031]
The sub-scanning unit 130 performs sub-scanning while rotating the driving roller 133 by rotation of the motor 134 driven by the driver 135 and moving the conveyance table 111 at a constant speed. In this embodiment,
The stimulable phosphor plate 110 is held in a horizontal direction by a carrier 111, and the carrier 111 is moved in a sub-scanning direction by a driving roller 133 while being guided linearly in a horizontal direction by guide means.
[0032]
Here, by having an elastic member on the surface as the drive roller 133, it becomes possible to further reduce the vibration when driving the carriage 111, and to suppress the influence on the image quality. Note that it is preferable to use rubber as the elastic member from the viewpoints of vibration reduction and frictional force. In addition, not only the surface of the driving roller 133 but also the entire or most of the driving roller is made of an elastic member such as rubber, so that the driving roller has a sufficient frictional force for driving, and further reduces vibration. The effect on image quality can be suppressed.
[0033]
Further, the drive roller 133 and the motor 134 may be a direct drive that is directly connected, or may use various transmission mechanisms (mechanisms using gears, belts, and the like).
[0034]
140 is an excitation unit that irradiates the stimulable phosphor plate 110 with excitation light, and irradiates with excitation light that scans in the z direction. The excitation unit 140 may generate excitation light for scanning in the main scanning direction by a deflecting unit such as a polygon mirror or a galvanometer mirror, or may be configured to move a light source in the main scanning direction. The excitation means 140 irradiates excitation light so as to repeat the main scanning finely during the sub-scanning.
[0035]
Reference numeral 150 denotes a photoelectric converter 154 such as a photomultiplier, which photoelectrically converts stimulated emission from the stimulable phosphor plate 110 to generate pixel data serving as a source of a radiation image signal corresponding to radiation image information. It is a photoelectric conversion unit.
[0036]
Note that a light collector 152 such as an optical fiber for collecting excitation light generated in the main scanning direction is disposed between the stimulable phosphor plate 110 and the photoelectric converter 154. The excitation light collected in step (1) is collected in the photoelectric converter 154 by the condenser tube 153.
[0037]
Reference numeral 170 denotes an image generation unit which generates a radiation image signal from the pixel data obtained by the photoelectric conversion unit 150.
[0038]
Hereinafter, the operation of the radiation image reading apparatus 100 according to the embodiment of the present invention will be described.
[0039]
When a reading instruction is given to the control unit 101 from an operation unit (not shown) or the like, the control unit 101 gives a radiation image reading command to each unit.
[0040]
The excitation unit 140 that has received the reading instruction starts irradiating the stimulable phosphor plate 110 with excitation light that scans in the main scanning direction (the direction perpendicular to the paper surface of FIGS. 1 and 2).
[0041]
Further, in the sub-scanning means 130 which has received the reading instruction, the driving roller 133 is rotated by the motor 134 so that the main scanning can be repeatedly performed at a predetermined pitch while the main scanning is repeated. As a result, the sub-scanning linear guide 132 performs sub-scanning while moving on the sub-scanning linear guide rail 131 at a constant speed.
[0042]
By performing such main scanning and sub-scanning in parallel, the excitation light in the main scanning direction is repeatedly irradiated on the stimulable phosphor plate 110 in the sub-scanning direction. By repeating such main scanning and sub-scanning of the excitation light, the light collector 152 of the photoelectric conversion unit 150 collects the stimulable light emission of each line, and according to the excitation light, the stimulable phosphor. The stimulated emission generated from the plate 110 can be read. Then, the image generation unit 170 generates radiation image information from the pixel data read and generated by the photoelectric conversion unit 150 and outputs the radiation image information to the outside.
[0043]
In this embodiment, since the suction plate and the counterweight as in the conventional vertical suspension drive system are not used, the weight of the moving body can be reduced. The frequency f of the natural vibration is
f = (1 / 2π) √ (K / M).
Here, K is the rigidity of the moving body, and M is the weight of the moving body.
[0044]
When a stimulable phosphor plate equivalent to that of the related art is used, an adsorption plate and a counterweight are not required. In the present embodiment, the moving body, which was conventionally about 12 to 13 kg, is reduced to about 5 kg. can do.
[0045]
As a result, the frequency of the natural vibration, which is about 35 Hz, can be increased to about 50 Hz at the sub-scanning speed equivalent to that of the related art (see FIG. 3). When the frequency of the natural vibration increases in this way, the spatial frequency of image unevenness generated in the radiation image information also increases in proportion. Since the visibility level at which a human perceives image unevenness tends to decrease on the high frequency side as shown in FIG. 4, the effect of reducing the image unevenness due to the increase in the frequency of image unevenness according to the present embodiment is obtained. Is obtained.
[0046]
Further, in the present embodiment, since the driving roller 133 having an elastic member on the surface is used, the belt does not vibrate as in the vertical suspension driving method, and the vibration in the case where a ball screw is used is not generated. Vibration does not occur, and the level of the generated natural vibration can be made smaller than before (FIG. 3). Accordingly, the level at which image unevenness occurs due to unevenness in the sub-scanning speed is also reduced.
[0047]
In addition, not only the surface of the driving roller but also the entire or most of the driving roller is formed of an elastic member such as rubber as an elastic member of the driving roller 133, thereby further reducing vibration and suppressing an effect on image quality. Becomes possible. Further, by using an elastic member such as rubber, it is possible to obtain a necessary frictional force at the time of driving.
[0048]
As described above, due to the synergistic effect of the two effects that the spatial frequency of the image unevenness is increased to make it difficult to visually recognize the image and that the level of the image unevenness is reduced, the image unevenness generated in the radiation image information is further felt. It becomes difficult.
[0049]
For this reason, image unevenness does not become a problem, and the radiation image information can be used as a good diagnostic image.
[0050]
Further, the present invention can be applied not only to the radiation image reading apparatus in the medical field but also to the printing field.
[0051]
Further, the radiation image reading apparatus has an advantage that it can be configured at a low cost because the configuration is not complicated as compared with the conventional apparatus, although the performance is improved. Further, it is not necessary to strictly control the parallelism required when the linear motion guide and the ball screw are used.
[0052]
【The invention's effect】
As described in the above embodiment, the following effects can be obtained.
[0053]
(1) In the invention according to claim 1, the recording surface of the stimulable phosphor sheet or the stimulable phosphor plate on which the radiation image is recorded is scanned by excitation light, and the stimulable phosphor plate is stimulated by the excitation light. When reading the stimulable luminescence generated in the, the stimulable phosphor sheet or stimulable phosphor plate is held in the horizontal direction by the carrier, and the carrier is guided linearly in the horizontal direction by the guide means, It is moved in the sub-scanning direction by a driving roller. Then, along with the movement in the sub-scanning direction, the stimulable phosphor sheet or the stimulable phosphor plate is irradiated with excitation light that scans in a horizontal direction substantially perpendicular to the sub-scanning direction, thereby stimulating the stimulable phosphor sheet. The radiation image information stored and recorded on the body plate is stimulated to emit light.
[0054]
In this radiation image reading apparatus, as the sub-scanning, the stimulable phosphor sheet or the stimulable phosphor plate is conveyed in the horizontal direction by the driving roller, so that vibration such as a ball screw does not occur, and There is no need to strictly control the parallelism between the linear motion guide and the ball screw. Further, since the counterweight required for the vertical suspension driving method is not required, the frequency of natural vibration increases, and image unevenness occurs at a spatial frequency with low visibility. As a result, it is possible to read an image with high accuracy without being affected by the vibration or the like generated by the scanning means.
[0055]
(2) According to the second aspect of the present invention, in the above (1), since the driving roller has an elastic member on a surface portion, vibration can be further reduced, and influence on image quality can be suppressed. become.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an electrical configuration of a radiation image reading apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a mechanical configuration of a main part of the radiation image reading apparatus according to the embodiment of the present invention.
FIG. 3 is a characteristic diagram illustrating a state of a frequency of natural vibration according to the embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 100 radiation image reading apparatus 101 control means 110 stimulable phosphor plate 120 optical unit 130 sub-scanning means 140 excitation means 150 photoelectric conversion means 170 image generation means

Claims (2)

A radiation image reading apparatus that scans a recording surface of a stimulable phosphor sheet or a stimulable phosphor plate on which a radiation image is recorded with excitation light and reads stimulable luminescence generated on the stimulable phosphor plate by the excitation light. And
A carrier for holding the stimulable phosphor sheet or the stimulable phosphor plate in a horizontal direction,
Sub-scanning means for moving the transfer table by a driving roller while linearly guiding the transfer table in the horizontal direction by guide means,
Irradiating the stimulable phosphor sheet or the stimulable phosphor plate with excitation light that scans in a horizontal direction substantially perpendicular to the sub-scanning direction, and the radiation accumulated and recorded on the stimulable phosphor plate; Excitation means for stimulating the image information to emit light,
A radiation image reading apparatus, comprising: The drive roller of the sub-scanning means has an elastic member at least on a surface portion in contact with the conveyance table,
The radiographic image reading device according to claim 1, wherein:

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