JPH0454217B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention causes radiation image information to be stimulated to emit light by irradiating excitation light to a stimulable phosphor sheet that stores and records radiation image information. The present invention relates to a radiation image information reading method and apparatus for optically reading the obtained stimulated luminescence light using a photodetector.

(Prior art) Radiographic image information of a human body, etc. is once recorded on a stimulable phosphor sheet, and this phosphor sheet is scanned with excitation light such as a laser beam to generate stimulated luminescence light. A radiation image information recording and reproducing system is known in which an image signal is obtained by photoelectrically reading out the exhaustion light, and based on this image signal, it is output as a visible image to a recording material such as a photographic light-sensitive material, a CRT, etc. No. 55-12429, No. 56-11395, No. 55-163472
No. 55-116340, etc.).

On the other hand, in an X-ray imaging apparatus, an irradiation field diaphragm such as a collimator is sometimes provided near an X-ray source in order to control the X-ray irradiation range of a subject.
This irradiation field aperture not only has a humane effect on medical diagnosis by preventing X-rays from being irradiated to areas unrelated to diagnosis, but also prevents X-rays from being scattered by objects located outside the area to be diagnosed or observed. The scattered X-rays
It also serves to prevent the X-ray image from entering the area to be diagnosed or observed and being recorded on the recording material, thereby reducing the contrast and image quality of the X-ray image of this area.

Using an irradiation field aperture in this way prevents the above-mentioned deterioration in image quality because the X-rays are irradiated only on the area of the subject that you want to photograph, but conversely, the irradiation field is narrowed down to be narrower than the size of the recording material. At times, scattered X-rays scattered by objects within the irradiation field are recorded at the outer edge of the recording material outside the irradiation field, and noise is likely to be formed. Particularly when using wide latitude recording materials such as stimulable phosphor sheets, the noise caused by this scattered X-ray becomes much more noticeable than in traditional film/screen systems, causing The appearance of the item is damaged.

This problem does not occur if a stimulable phosphor sheet that matches the size of the irradiation field is selected and used for each photograph, but such operations are cumbersome and impractical.
In particular, a system that incorporates one type of relatively large stimulable phosphor sheet into the device to photograph and read any body part (see Japanese Patent Application No. 57-84436 (Japanese Unexamined Patent Publication No. 58-200269)) Since it is not possible to change the size of the stimulable phosphor sheet each time an image is taken, the above problem had to be solved by other means.

(Object of the Invention) An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an excellent radiation image information reading method and apparatus that is not affected by noise caused by scattered radiation scattered in the irradiation field. .

(Structure of the Invention) The radiation image information recording and reading method according to the present invention includes:
Receives irradiation field information including the aperture size of the irradiation field diaphragm set at the time of recording and the distance from the radiation source to the irradiation field diaphragm and the stimulable phosphor sheet, and irradiates the image information reading area based on the information. The radiation image information recording/reading device according to the present invention is characterized by being provided with means for receiving irradiation field information at the time of recording and narrowing down the reading area to within the irradiation field based on the information. do.

(Effects of the Invention) According to the radiation image information recording and reading method and apparatus of the present invention, when image information is recorded on a stimulable phosphor sheet using an irradiation field aperture, the image information reading area is within the irradiation field. Since the light is narrowed down, noise components due to scattered radiation recorded outside the irradiation area of the stimulable phosphor sheet are not read out, making it possible to obtain an excellent final image. Furthermore, by narrowing down the reading area, it is possible to shorten the reading time or increase the reading density. Furthermore, since these effects are achieved, the troublesome operation of selecting a stimulable phosphor sheet according to the size of the irradiation field for each photographing is no longer necessary. Therefore, a significant improvement in image quality can be achieved, particularly in a system in which a relatively large stimulable phosphor sheet of one kind is incorporated into the device for photographing and reading.

(Embodiments) Hereinafter, the present invention will be described in detail based on the drawings.

The drawing is a schematic diagram showing a radiation image information recording/reproducing system including a radiation image information recording/reading device according to a preferred embodiment of the present invention.

In the drawings, 1 indicates a photographing section, 4 a reading section, 5 a reproduction/recording section, and 6 an overall control section.

In the imaging unit 1, the irradiation field of the X-rays irradiated from the X-ray source 101 toward the subject 102 is narrowed down by an irradiation field diaphragm 110 such as a collimator.
After passing through the subject 102, it is absorbed by the stimulable phosphor sheet 103, and the stimulable phosphor sheet 1
During 03, X-ray image information of the subject is accumulated and recorded. The irradiation field aperture 110 is the irradiation field aperture control device 11
5, the stimulable phosphor sheet 103
An irradiation field 103A indicated by diagonal lines is formed above. The irradiation field diaphragm control device 115 also controls the aperture size d of the irradiation field diaphragm 110, the respective distances l and L from the X-ray source 101 to the irradiation field diaphragm 110 and the stimulable phosphor sheet 103, and further controls the X-rays. In the case of oblique irradiation, the angle θ formed by the X-ray source 101 and the stimulable phosphor sheet 103 (more specifically, the angle θ formed by the vertical line from the focal point of the X-ray source 101, the focal point and the aperture of the irradiation field stop) The overall control device 604 transmits information about the angle formed by the line connecting the centers of the
Output to. Here, the "size" of the aperture of the irradiation field diaphragm 110 means the diameter if the aperture of the diaphragm is circular;
In the case of a rectangle, it represents the length of the side or diagonal. The overall control device 604 calculates the size of the irradiation field 103A based on the information output from the irradiation field aperture control device 115. Here, the size D of the irradiation field is D = dL/l when the X-ray source 101 is not tilted with respect to the phosphor sheet 103, and D=dL/l. When irradiating X-rays from an angle, D=dL/l×1+tan ² θ/1−(d/2l) ² tan
Determined by ² θ.

Further, the calculation of the size D of the irradiation field 103A may be performed in the irradiation field aperture control device 115, and the result may be output to the overall control device 604.

In this embodiment, the relative positional relationship between the X-ray source 101 and the stimulable phosphor sheet 103 is such that, for example, the center of the stimulable phosphor sheet is aligned with a line passing through the center of the X-ray source 101. Therefore, once the size of the irradiation field 103A is determined, the stimulable phosphor sheet 10 of the irradiation field 103A
3 can be uniquely determined (that is, the position information is included in the size information). On the other hand, if the positional relationship between the X-ray source 101 and the stimulable phosphor sheet is not constant, this positional relationship is detected in the imaging unit and the information is output to the reading control device 414 via the overall control device 604. All you have to do is do it.

This photographing section may be separate from the reading section, or may be configured integrally with the reading section.

In the reading section 4, a laser beam 402 emitted from a laser light source 401 is passed through a filter 4 that cuts out the wavelength range of stimulated luminescence light emitted from the stimulable phosphor sheet 103 by excitation of the laser 402.
After passing through 03, beam expander 404
The diameter of the beam is precisely adjusted, and the beam is deflected onto the stimulable phosphor sheet 103 via a plane reflecting mirror 406 by an optical deflector 405 such as a galvano mirror. An fθ lens 407 is disposed between the optical deflector 405 and the plane reflecting mirror 406, so that even when the laser beam 402 scans the phosphor sheet 103, it always has a uniform beam diameter. On the other hand, the phosphor sheet 103 is
08 direction to perform sub-scanning,
As a result, the entire surface of the phosphor sheet 103 is irradiated with laser light. When the laser beam 402 is irradiated in this way, the stimulable phosphor sheet 103 emits stimulated luminescent light with an amount proportional to the accumulated and recorded X-ray energy, and this emitted light is transmitted to the light guiding sheet for book reading. 409. The light guide sheet 409 has a linear incident surface and is disposed adjacent to the scanning line on the stimulable phosphor sheet 103, and has an annular exit surface and is arranged to oppose the scanning line on the stimulable phosphor sheet 103. It is brought into close contact with the light receiving surface of the photodetector 410. This light guide sheet 409
is made by processing a transparent thermoplastic resin sheet such as acrylic resin, and is constructed so that the light that enters from the incident surface is transmitted to the exit surface while being totally reflected inside, and has no accumulation property. Fluorescent sheet 10
The stimulated luminescent light from the photodetector 410 is guided through the light guide sheet 409, exits from the exit surface, and is received by the photodetector 410. Preferred shapes, materials, etc. of the light-guiding sheet are disclosed in Japanese Patent Laid-Open Nos. 55-87970 and 56-11397. A filter that selectively transmits only the wavelength range of stimulated luminescence light is attached to the light receiving surface of the photodetector 410.
0 is designed to detect only stimulated luminescence light.

Here, in order to narrow down the image information reading area to the irradiation field 103A on the stimulable phosphor sheet 103, the following scanning is performed. That is, the reading control device 414 uses the next signal determined based on the size information including the position information of the irradiation field 103A inputted from the overall control device 604, or the position and size information, that is, the irradiation field on the main scanning line. The optical deflector driver 417 receives an on-off signal that drives the optical deflector driver 417 only while 103A is present, and an amplitude signal that limits the main scanning amplitude to the length in the width direction of the irradiation field.
send to When the irradiation field 103A is not on the main scanning line, the optical deflector is stopped at a position where it reflects the laser beam in a direction that does not hit the stimulable phosphor sheet, but when the drive ON signal is input, , the stimulable phosphor sheet is scanned with an amplitude commanded by the amplitude signal, and the scanning is terminated in accordance with the drive off signal. By doing this, the irradiation field 10
Laser light is irradiated only on the inside of 3A.
Note that in the above case, the optical deflector driver 417 is used to narrow down the reading area in the main scanning direction to the irradiation field 103A.
However, instead of this, a shutter may be provided in the optical path of the laser beam, and this shutter may be opened only while the irradiation field 103A is on the main scanning line.

In the present invention, it is preferable that the wavelength region of the excitation light and the wavelength region of the stimulated luminescent light do not overlap in order to improve the S/N ratio, and the excitation light source and the stimulable fluorescent light are selected so as to satisfy such a relationship. It is preferable to choose a light body. Specifically, Japanese Patent Application Publication No. 1983-
As disclosed in Publication No. 12429, the excitation light wavelength is 600 to 700 nm, and the stimulated emission light wavelength is 300 to 700 nm.
It is desirable to set the wavelength to 500 nm.

The stimulable phosphor that can be preferably used in the present invention is JP-A No. 55-12142, No. 55-14143, No. 55-
It is described in No. 14144, No. 55-14145, etc.

The stimulated luminescent light detected by the photodetector 410 is converted into an electrical signal and amplified to an appropriate level electrical signal by the amplifier 411 whose sensitivity is set by the amplification factor setting value a. 412. The A/D converter 412 converts the digital signal into a digital signal using a scale factor suitable for the signal fluctuation width according to the recording scale factor setting value b, and inputs the digital signal to the signal processing circuit 413. In the signal processing circuit, signal processing is performed to obtain an X-ray image excellent in suitability for observation and interpretation based on the reproduction image processing condition setting value c, and the signal is transmitted to the reproduction recording section and input to the optical modulator 501.

In the reproducing/recording section 5, a recording laser light source 5
A laser beam 503 from 02 is modulated by an optical modulator 501 based on an image signal, and a scanning mirror 504 outputs a light-sensitive material 50 such as a photographic film.
5 is scanned over. At this time, since the photosensitive material 505 is transported in a direction perpendicular to the scanning direction (arrow 506) in synchronization with scanning, the photosensitive material 505
An X-ray image is output above.

In this embodiment, the optical modulator control device 50
7 is provided, and an image recording area 505A is formed on the photosensitive material 505 based on the size information (including position information) or the size and position information of the irradiation field 103A inputted from the overall control device 604.
By outputting image information so as to form a field and displaying only the image inside the irradiation field,
I'm trying to get a clearer final image.

The overall control unit 6 consists of the overall control device 604 and the console 603, and not only calculates the size including the position information of the irradiation field 103A, or both the size and the position, but also calculates the reading density and speed, as well as the Amplification factor setting value a, recording scale factor setting value b, reproduction image processing condition setting value c, etc. can be set.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications are possible.

For example, JP-A-58-67240, JP-A No. 58-67242,
As disclosed in No. 58-67243, etc., prior to the reading operation in the reading unit 4, a reading operation ("pre-reading") is performed to grasp the image information in advance using low-energy excitation light, Based on the result of this pre-reading, the amplification factor setting value a, the recording scale factor setting value b, and the reproduction image processing condition setting value c
etc. may be set.

Further, as shown in Japanese Patent Application Laid-Open No. 58-89244, a desensitizing section may be provided between the photographing section and the pre-reading section.

Furthermore, the laser light source that is the excitation light source in the reading section has a wavelength range different from that of the stimulated luminescence light.
The optical deflector can also be omitted by replacing it with an LED array.

Furthermore, the photodetector is not limited to a single one with a light-guiding sheet, but may be one in which a plurality of phototransistors or phototransistors are arranged in a straight line in the main scanning direction.

The recording method in the reproducing/recording section 5 is not limited to the direct recording method using a laser light source, but may also be a method of displaying on a CRT, video printer, etc., for example.

[Brief explanation of the drawing]

The drawing is a schematic diagram of an X-ray image information recording/reading system including an X-ray image information recording/reading apparatus which is an embodiment of the present invention. 1... Photography department, 101... X-ray source, 102...
Subject, 103...Storage phosphor sheet, 103
A...Radiation field, 110...Irradiation field aperture, 1
15...Irradiation field aperture control device, 4...Reading section, 4
01... Laser light source, 402... Laser light, 40
3...Filter, 404...Beam expander, 405...Light deflector, 406...Plane reflecting mirror, 407...Fθ lens, 408...Transfer direction,
409...Light guide sheet, 410...Photodetector,
411...Amplifier, 412...A/D converter, 4
13... Signal processing circuit, 414... Read control device, 417... Optical deflector driver, 5... Reproduction/recording section, 501... Optical modulator, 502... Laser light source for recording, 503... Laser light, 504...Scanning mirror, 505...Photosensitive material, 505A...Image recording area, 507...Light modulator control device, 6...
Overall control unit, 603... Console, 604...
Overall control device.

Claims (1)

[Claims] 1. Radiation image information is accumulated and recorded on a stimulable phosphor sheet by applying an irradiation field aperture, and excitation light is irradiated to the stimulable phosphor sheet, and the stimulable phosphor sheet is In a method for recording and reading radiation image information in which radiation image information stored in a storage medium is stimulated to emit light and the obtained stimulated light is optically read to obtain image information for observation and interpretation, the irradiation field aperture is Receives irradiation field information including the aperture size of the irradiation field diaphragm set at the time of application and the distance from the radiation source to the irradiation field diaphragm and the stimulable phosphor sheet, and calculates the image information based on the information. A radiation image information recording and reading method characterized in that the reading area is narrowed down to a radiation irradiation field during image recording of the stimulable phosphor sheet. 2. An imaging unit having an irradiation field aperture for accumulating and recording radiation image information on a stimulable phosphor sheet, and irradiating excitation light onto the stimulable phosphor sheet, thereby recording the radiation image information emitted from the sheet. In a radiation image information recording/reading device having a reading unit that photoelectrically reads the stimulated luminescence light to obtain an image signal, the size of the aperture of the irradiation field diaphragm is set when applying the irradiation field diaphragm in the imaging unit. receiving field information including a distance from a radiation source to the field stop and the stimulable phosphor sheet;
A radiation image information recording/reading apparatus characterized by comprising means for narrowing down the reading area of the image information to within the irradiation field based on the information.