JPS5867242A - Apparatus for reading out radioactive image information - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] By irradiating a stimulable phosphor sheet with excitation light,
The present invention relates to a radiation image information reading device that causes radiation image information to be stimulated from a stimulable phosphor sheet and photoelectrically read by a photodetector that uses the resulting stimulated radiation.

When certain types of phosphors are irradiated with radiation (X-rays, alpha rays, beta rays, gamma rays, ultraviolet rays, etc.), a portion of this radiation energy is accumulated in the phosphor, causing the phosphor to emit visible light. It is known that when irradiated with excitation light such as .

This stimulable phosphor is used to record radiation image information of the human body, etc. on the stimulable phosphor provided on a sheet, and this phosphor sheet is scanned with excitation light such as a laser beam. The present applicant has proposed a radiation image recording and reading method in which the stimulated luminescent light Z is generated, the resulting stimulated luminescent light is read out photoelectrically to obtain an image signal 2, and the two peak signals are output as a visual image. The VC 4J has been proposed.

(JP-A-55-12492, JP-A No. 56-11395, etc.) Compared to radiographic systems that use conventional silver halide photography, this method records images over a single line exposure range with an extremely wide exposure. It has very practical advantages. In other words, in a stimulable phosphor, it is recognized that the photometer of the emitted light produced by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range, and therefore it can be used under various imaging conditions. Radiation exposure by…:
Even if the amount of light fluctuates considerably, the reading gain of the emitted light is set to an appropriate value, the photoelectric conversion means reads it and converts it into an electrical signal, and this electrical signal is used to convert recording materials such as photographic materials, etc. A radiation image that is not affected by fluctuations in radiation exposure by outputting it as a visible image on a display device such as C It l'? Obtainable.

Further, according to this system, radiation image information stored and recorded in a stimulable phosphor is converted into an electrical signal and then subjected to appropriate signal processing 2, and this electrical signal is used to record a recording material such as a photographic light-sensitive material.

By outputting the image as a visible image to a display device such as CI (, T, etc.), it is possible to obtain an extremely thick radiation image with excellent suitability for observation and interpretation (diagnosis).

In this way, in a radiation imaging system using a stimulable phosphor, the reading gain can be set to an appropriate value to perform photoelectric conversion of stimulated luminescence and output it as a visible image. Fluctuations in radiation exposure due to fluctuations in voltage or MAS value, variations in the sensitivity of stimulable phosphors, variations in sensitivity of photodetectors, changes in exposure due to subject conditions, or differences in radiation transmittance depending on the subject, etc. Even if the energy accumulated in the stimulable phosphor differs depending on the cause, and even if the amount of radiation exposure is reduced, it is possible to obtain radiographic images that are not affected by fluctuations in these factors. Moreover, by first converting the stimulated luminescent light into an electrical signal and then performing appropriate signal processing2 on this electrical signal, it is possible to obtain a radiation image suitable for diagnostic areas such as the chest and heart, making it suitable for observation and interpretation. However, in order to eliminate the effects of fluctuations in imaging conditions or to obtain radiographic images with excellent observation and interpretation aptitude, it is possible to improve the The recording pattern determined by the recording state of image information, or the chest/abdomen region of the subject, the imaging method such as simple or contrast imaging (hereinafter, when both are referred to collectively, it is simply referred to as "
"Accumulated record information". ) before outputting a visible image for observation and interpretation, and it is essential to adjust the reading gain to an appropriate value or perform appropriate signal processing 2 based on the accumulated recorded information. .

Furthermore, in order to obtain radiographic images that are well suited for observation and interpretation, it is necessary to determine the recording scale factor so that the resolution is optimized according to the contrast of the recording pattern.

In this way, radiographic image information is accumulated and recorded before outputting a visible image? As a method of understanding, Japanese Patent Application Laid-Open No. 55-501
The method disclosed in No. 80 is known. This method is based on the knowledge that when the stimulable phosphor sheet is irradiated with radiation, the amount of instantaneous light emitted from the stimulable phosphor sheet is proportional to the amount of energy stored and recorded in the stimulable phosphor sheet. Based on this, by detecting this instantaneous emitted light, the accumulated recorded information of radiation image information is grasped, and based on this information, appropriate signal processing is performed to obtain a radiation image with excellent suitability for observation and interpretation. It is. According to this method, it is possible to adjust the reading gain to an appropriate value, appropriately determine the recording scale factor, or perform appropriate signal processing. However, since the radiation QJ ray irradiation section and the radiation image information reading section are usually located apart,
In the meantime, a signal transmission system must be configured, and the device if
This method has two advantages: it does not become complicated, but it has the disadvantage of being unable to avoid an increase in costs.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 55-1.16340, a non-stimulable phosphor is provided in the vicinity of a stimulable phosphor sheet,
When radiographic image information is recorded, a photodetector detects the luminescence rate emitted by this non-stimulable phosphor and determines the recording state or recording pattern of the radiographic image information stored and recorded in the stimulable phosphor. There is also a method of guessing, but this method is
In addition to the shortcomings of the method disclosed in No. 5-50180, since the stimulable phosphor itself is not used as a detection means, it is difficult to record the image information stored in the stimulable phosphor. The disadvantage was that the information obtained was only indirect (C) inferences, and the reliability of the information obtained in this way was low.

The present invention provides a device that can easily and accurately detect radiographic image information accumulated and recorded in a stimulable phosphor prior to a reading operation to obtain a visible image 2 for observation and interpretation. The purpose is to

Another object of the present invention is to perform a reading operation for obtaining a visible image for observation and interpretation of radiation image information stored in a stimulable phosphor in a simple and accurate manner (detection). However, it is an object of the present invention to provide an apparatus that can reproduce radiographic images with excellent diagnostic performance based on this information.

As a result of extensive research to achieve this objective, the present inventor has determined that the energy of the excitation light of the irradiated knife during the reading operation (hereinafter referred to as "hon-reading") to obtain a visible image for observation and interpretation. A reading operation (hereinafter referred to as "pre-reading") for grasping the accumulated recorded information of radiation image information stored in the stimulable phosphor in advance prior to the actual reading using excitation light of lower energy than the above-mentioned main reading. ), grasp the accumulated recording information of radiographic image information, and then perform the actual reading, and adjust the reading gain or determine the recording scale factor based on the pre-read information (hereinafter, read gain and recording scale factor are combined) (referred to as "reading conditions") or appropriate image processing conditions? After determining this and performing signal processing 2, it was found that a radiographic image was obtained that was not affected by fluctuations in imaging conditions or had excellent suitability for observation and interpretation, thus achieving the above objective. Even if a stimulable fluorophore that is considered to have the highest sensitivity at present is selected, the accumulation of 111. The light of the stimulated luminescence emitted from the phosphor is extremely weak, and it has been considered an essential requirement for this system to detect as much light as possible by the FftY source detector. (Japanese Unexamined Patent Publications No. 55-12492, No. 55-4867)
1I, No. 55-87970, etc.),
It is nothing short of absurd to intentionally dissipate the radiation energy stored in the stimulable phosphor by performing a pre-reading before the actual reading (the above findings are extremely surprising).

The present invention is based on this knowledge, and includes an excitation light irradiation means, a means for transporting a stimulable phosphor sheet, and a photodetection means for photoelectrically reading the stimulated luminescence 1 from the stimulable phosphor sheet. A pre-read reading system whose excitation light energy is smaller than the excitation light energy in the main reading K is provided separately from the main reading reading system, and the reading conditions for the main reading and/or are determined based on the output of the light detection means of the pre-read reading system.
Alternatively, the present invention is characterized by providing a control means for setting image processing conditions.

In the present invention, the energy of excitation light refers to the effective energy of excitation light received per unit area of the stimulable phosphor sheet.

In the VC of the present invention, the energy of the excitation light to be irradiated to the stimulable phosphor during pre-reading is lower than the energy of the excitation light during main reading, and if the ratio of the energy of the main reading is close to IVC, the closer the Japanese book reading is. (However, if this ratio is less than 1, it is possible to obtain a radiation 041fdi1 image suitable for observation and interpretation by adjusting the reading gain value appropriately to N1'4.) However, in order to obtain radiographic images that are suitable for observation and interpretation, it is necessary to read in advance the accumulated recorded information of the radiographic image information stored in the stimulable phosphor. As long as the VC is maintained to a sufficient degree to be used for selecting the image processing conditions or the optimal image processing conditions, in other words, the stimulated luminescence emitted from the stimulable phosphor,)Th'Y is sufficiently detected in the above sense. As far as the vine is concerned, it is desirable that the energy ratio of the excitation light for pre-reading and main reading is small, less than 50%, preferably less than 10%, more preferably less than 3%. Lower limit of this ratio ff? However, it is determined by the accuracy of the pre-reading photostimulated luminescence detection system.

In the present invention, the energy of excitation light in look-ahead 2
The energy can be made smaller than the actual reading by reducing the output of the laser light source by 2, by increasing the beam diameter of the laser beam, by increasing the scanning speed of the laser beam, and by using a stimulable phosphor sheet. Known methods can be used, such as adjusting the transport speed to a constant speed.

In the present invention, it is desirable that the pre-reading be performed within one hour before the main reading. The radiation energy stored and recorded in the stimulable phosphor has the characteristic of attenuating (Fadlng) with time, so in order to effectively use the recorded information obtained by pre-reading for main reading, it is necessary to read the pre-reading thorough reading. It is desirable to keep the time as short as possible. However, according to the research of the present inventor, the attenuation of the radiation energy stored and recorded in the storage phosphor is greatest immediately after recording radiation image information on the storage phosphor (approximately 1 hour after recording). Approximately 10% of the radiation energy is lost due to attenuation, but it is recognized that the rate of attenuation decreases thereafter.On the other hand, the difference between the accumulated amount of radiation energy at the time of pre-reading and that at the time of main reading is less than 10 inches. In this case, the accumulated record information obtained by pre-reading is used to detect the accumulated record information of the radiation image information accumulated and recorded in the stimulable phosphor, and this is used to set the reading conditions for the main reading or to set the read condition after reading. It has been found that even when the signal part ITp f ;f is reached, a radiation image with sufficient suitability for observation and interpretation can be obtained for practical purposes. Therefore, if the time interval between pre-reading and main reading is set to 1 hour or less, It is preferable that the difference in the accumulated amount is always less than a factor of 10, which guarantees that a radiation image with practically sufficient suitability for observation and interpretation can be obtained.

According to the present invention, it is possible to know in advance the recording state of radiation image information stored in the stimulable phosphor, so there is no need to use a reading system with an exceptionally wide dynamic range. In addition, by appropriately adjusting the reading gain based on this recorded information, it is possible to obtain radiation image information that is always suitable for observation and interpretation even when the imaging conditions change.

Furthermore, according to the present invention, it is possible to know in advance the recording pattern of radiation image information stored and recorded in the stimulable phosphor, so that the electric signal after signal processing and reading according to the recording pattern can be By applying this method, it becomes possible to obtain radiographic images with excellent suitability for observation and interpretation.

Furthermore, according to the present invention, it is possible to know in advance the recording pattern of the radiographic image information stored and recorded in the stimulable phosphor, so it is possible to omit the actual reading of parts where the recording pattern does not exist. , it becomes possible to significantly shorten the reading time.

In the present invention, it is preferable that the wavelength region of the excitation light and the wavelength region of the stimulated luminescence light do not overlap in order to improve the S/N ratio, and the excitation power source and the storable fluorescent light are adjusted so as to satisfy such a relationship. It is preferable to choose a light body. Specifically, it is desirable that the excitation light wavelength is 600 to 700 rvnK and the stimulated emission light wavelength is 300 to 500 nm.

As described above, the stimulable Th body that emits stimulated luminescence light of 300 to 500 tLm and can be advantageously used in the VC of the present invention includes, for example, rare earth element-activated alkaline earth metal fluorohalide. Fluorescent material [specifically, JP-A-5
5-12143 (f3 al
−x −y + M g X + Ca y )FX:
aEu2+ (where LX is c7 and 1 juice), X and y are Q (xy≦0.6 and xy40, a is 10-6≦a≦5×10-2 ), □(1'la+-xM[1x)FX:yA (However, Mll
is Mg, C: I, Sr, Zn, and one or more of (sub);
I) y , I) r , II (1, N (+ , Yl) and t]
6, y is O≦y≦0.2), etc.]; JP-A-55-1
ZnS: Cu, Pb described in Publication No. 2142
, T3aO-xAll, , 03: Eu (however, 0.8
≦X≦10) and MIIO·xs io. :A (However, Mll is Mg, Ca, Sr, Zn, Cd or Ba, A is Ce, Tb, Eu, Tm, Pb, T, d, Bi
or Mn, and X is 0.5≦X≦2.5)
; and described in Japanese Patent Application Laid-Open No. 55-12144, 7.
z LnOX: . Barium fluorohalides are particularly preferred because they have excellent photostimulable luminescence.

Furthermore, barium fluorohalide phosphor was developed in Japanese Unexamined Patent Publication No. 56
As disclosed in Publication No. 2385 and No. 56-2386 (added with metal fluoride, or Japanese Patent Application No. 1983-
150873 (metal chloride, metal bromide, metal iodide) to which at least 1% Myx is added is preferable because stimulated luminescence is further improved.

In addition, as disclosed in Japanese Patent Application Laid-Open No. 55-163500 (C), the phosphor layer of a stimulable phosphor plate prepared using the above-mentioned stimulable phosphor is colored with a pigment or dye. As a result, the sharpness of the final image will improve, and the
Ushii.

The signal processing used in the present invention is as follows:
No. 5-87970, No. 56-11038, Patent application 1972
-151398, No. 54-151400, No. 54-
151402, 5/l-168937, etc., and floors disclosed in JP-A-55-116339, JP-A-55-1.163/10, JP-A-55-88740, etc. Examples include processing.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

The drawing is a schematic diagram of an X-ray image information recording system including an X-ray image information reading device that is an embodiment of the present invention.

In the drawings, ■ indicates a photographing section, 2 a pre-reading reading section, 3 a main reading reading section, and 4 a reproduction/recording section.

In the imaging unit IVC, the object 102 is
After the X-rays irradiated towards the object 102 pass through the object 102,
The X-ray image information of the subject is absorbed by the stimulable phosphor sheet 103 and stored and recorded in the phosphor sheet 103.

The phosphor sheet 10 on which X-ray image information has been accumulated and recorded in this way
3 is sent to the prefetch reading unit 2.

In the pre-reading reading section 2, a pre-reading laser light source 201
The laser beam 202 emitted from the stimulable phosphor sheet 103 is excited by the laser beam 202, passes through a filter 203 that cuts the wavelength region of the stimulated luminescent light emitted from the stimulable phosphor sheet 103, and is then deflected by an optical deflector 204 such as a galvanometer mirror. The light is one-dimensionally deflected and incident on the stimulable phosphor sheet 103 via the plane reflecting mirror 205. Here, the laser light source is selected so that the wavelength range of the excitation light does not overlap with the wavelength range of the stimulated luminescence light from the stimulable phosphor.

On the other hand, the phosphor sheet 103 is moved in the direction of the arrow 206 to perform sub-scanning, and as a result, the entire surface of the phosphor sheet 1o3 is irradiated with laser light.
. Here, the power of the laser light source 201, the laser light 202
The beam diameter of the laser beam 202, the scanning speed of the laser beam 202, and the transport speed of the phosphor sheet 103 are selected so that the energy of the pre-reading light 202 is smaller than that of the main reading. When the laser beam 202 is irradiated in this manner, the stimulable phosphor sheet 103 emits stimulated luminescence light with an amount proportional to the accumulated and recorded X-ray energy, and this luminescent light is transmitted to the pre-reading light guide sheet. 1, o This light guiding sheet 1-207 has a linear incident surface and is arranged adjacent to and opposite to the scanning line on the stimulable phosphor sheet 103. The surface is brought into close contact with the light-receiving surface of the photodetector 208, such as an annular vinyl or photomultiply. This light guide sheet 207 is made by processing a transparent thermoplastic resin sheet such as acrylic resin, and is configured so that the light incident from the incident surface is transmitted to the exit surface while being totally reflected inside. The stimulated luminescent light from the stimulable phosphor sheet 103 is guided through the light guiding sheet 207,
The light is emitted from the exit surface and is received by the photodetector 208.

The preferred shape, material, etc. of the light guide sheet are disclosed in Japanese Patent Application Laid-Open No. 55-8
It is disclosed in No. 7970, No. 56-11397, etc.

A filter is attached to the light-receiving surface of the photodetector 208, which transmits only the source of the wavelength range of the stimulated luminescent light and cuts the amount of light in the wavelength range of the excitation light, and detects only the stimulated luminescent light. It has become so. The output of the photodetector 208 is sent to the amplifier 209
The signal is amplified and input to the control circuit 314 of the reading unit 3 for main reading. The control circuit 314 outputs an amplification factor setting value a1, a recording scale factor setting value 1), and a reproduction image processing condition setting value C'aj according to the obtained accumulated recording information. The stimulated luminescence light detected by the photodetector 208 in the main reading is converted into an electrical signal, and after being amplified to an electrical signal at an appropriate level by an amplifier whose sensitivity is set by the amplification factor setting value a: 311 K, the A/D It is input to converter 312 . A
l1) Recording scale factor setting value 1 in converter 312
) is converted into a digital signal using a scale factor suitable for the signal fluctuation width, and is input to the signal processing circuit 313. In the signal processing circuit, the playback image processing condition setting value cVC
Based on this signal, signal processing is performed to obtain an X-ray image with excellent suitability for observation and interpretation, and the signal is transmitted to the recording unit 4.

In the main reading reading section 3vc, the main reading laser light source 3
The laser beam 302 emitted from the laser beam 30
Emitted from the stimulable phosphor sheet 103 by excitation of 1-
Filter 3 that cuts the wavelength range of photostimulated light
03, the beam diameter is strictly adjusted by a beam expander 304, and the beam is flattened by an optical deflector 305 such as a galvanometer mirror.

The light is deflected and incident on the stimulable phosphor sheet 103 through the reflecting mirror 306. An fθ lens 307 is disposed between the optical deflector 305 and the plane reflecting mirror 306, and even when the laser beam 302 scans the phosphor sheet 103, the beam diameter is always uniform. It has been set to 5. On the other hand, the phosphor sheet 103 is conveyed in the direction of arrow 308 for sub-scanning, and as a result, the entire surface of the phosphor sheet 103 is irradiated with laser light. In this way, the photometer emits stimulated luminescence light which is proportional to the energy, and this emitted light is incident on the guide sheet 309 for book reading. The light-guiding sheet 309 for main reading has the same material and structure as the light-guiding sheet 207 for pre-reading. Book reading dokusei sheet 30
9 is emitted from its exit surface, and a photodetector 310
The light is received by. A filter that selectively transmits only the wavelength range of the stimulated luminescence light is attached to the light receiving surface of the photodetector 3]0, and the photodetector 310 is designed to detect only the stimulated luminescence light. ing. The output of the photodetector k 310 is amplified by an amplifier 311, and the output is amplified by an A-/D converter 3.
12), the signal processing circuit 313
The image is subjected to signal processing so that an X-ray image with excellent suitability for observation and interpretation can be obtained. Amplification factor of amplifier 311, A/
The recording scale factor of the D converter 312 and the signal processing circuit in the signal processing circuit 313 are
Based on the accumulated record information obtained in the control circuit 31
4K Therefore, as described above (set to the most appropriate conditions).

The image signal output from the signal processing circuit 313 is sent to the recording section 4.
It is input to the optical modulator 401 of.

In the recording unit 4, a laser beam 403 from a recording laser light source 402 is modulated by an optical modulator 401 based on an image signal, and scanned by a scanning mirror 404 over a photosensitive material 405 such as a photographic film. At this time, since the photosensitive material 405 is transported in a direction perpendicular to the scanning direction (arrow 406) in synchronization with the VC scanning, the photosensitive material 405
5. The upper KX-ray image is output.

It goes without saying that the present invention is not limited to the embodiment on μ, and various modifications can be made.

For example, in the embodiment described above, the reading conditions and image processing conditions in the main reading are all set based on the accumulated record information obtained by pre-reading, about,
It is also possible to provide a separate auxiliary input device for input.

Furthermore, the recording method in the recording section 4Vc does not have to be a direct recording method using a laser light source.
It may be displayed on a display device such as Clt i'', etc., and the final radiation image displayed on Clt Various known recording methods can be employed.

Furthermore, the laser light source as an excitation light source in the pre-reading reading section and the main reading reading section can be replaced with a 1-rJI+E',I) Array having a wave extension region different from that of stimulated luminescence light. In this case, an optical deflector such as a galvanometer mirror can be omitted.

In addition, the photodetector does not have to be a single one with a light-guiding sheet, but it is also possible to use a plurality of transistors arranged in a straight line in the main scanning direction. It is.

Furthermore, it is also possible to uniformly expose the entire surface of the stimulable phosphor sheet and use a two-dimensional photodetector (RSY) such as a television camera that can capture the light.

Furthermore, the laser light sources 201 and 301 in the pre-reading reading section 2 and the main reading reading section 3 do not necessarily have to be separate (it is possible to use a single laser light source and divide it with a half mirror, etc.). You may also use it.

In addition, the reading gain can be adjusted by changing the amplification factor of the amplifier of the photodetector as explained in the above embodiment, or by changing the voltage applied to the photomultiply when a photomultiplier is used as a photodetector. The gain of the photodetector may be directly changed by changing . This has the advantage that only the signal is amplified and the noise is not amplified.

Further, in the embodiments described above, the pre-reading is performed over the entire surface of the stimulable phosphor sheet, but it is not necessarily necessary to perform the pre-reading over the entire surface of the phosphor sheet. usually,
In the case of an X-ray photograph, there is no image information to be observed and interpreted at the periphery of the phosphor sheet, so for example, the pre-reading can be omitted for a few blocks around the periphery, and the necessary radiographic images can be omitted in advance. If the information storage recording area is known, it is sufficient to pre-read only that area, and by pre-reading only the valid area, the reading time can be significantly shortened.゜

[Brief explanation of the drawing]

The drawing is a schematic diagram of an X-ray image information recording system including an X-ray image information reading device that is an embodiment of the present invention. 1... Photography section 101... X-ray source 102
...Subject 103...Request? Incredible phosphor sheet 2...Reading section for pre-reading 201...Kyuan first 1] Rate source 202...Laser light 203...
Filter 204... Light deflector 205... Plane reflecting mirror 206... Transfer direction 207... Light guiding sheet for pre-reading 208... Photo detector 2 ()
9... Amplifier 3... Reading unit for main reading 30
]... First reading ■ Roots f source 302... Laser light
303...Filter 304...Beam expander 305...Original deflector 306...Plane reflecting mirror 307...Fθ lens 308...Transfer direction 309...Light guiding property for main reading Seat 310...
・Photodetector 311...Amplifier 312...A/
D converter 313...Signal processing circuit 314...Control circuit 4...Reproduction/recording unit 401...Light modulator 402...Recording laser light source 403...
404...scanning mirror 405...
Photosensitive material 29-12

Claims (2)

[Claims] (1) Excitation light irradiation means for irradiating excitation light onto a stimulable phosphor sheet on which radiographic image information is accumulated and recorded; means for transporting the stimulable phosphor sheet; A radiation image information reading device including a photodetector for photoelectrically reading stimulated luminescence light that carries radiation image information emitted from a sheet, an excitation light irradiation means, a means for transporting the stimulable phosphor sheet, and an excitation light It includes a photodetection means for photoelectrically reading the stimulated luminescent light carrying radiation image information emitted from the stimulable phosphor sheet upon irradiation, and the energy of the excitation light is smaller than the energy of the excitation light in main reading. A radiation image characterized in that a pre-reading reading system is provided separately from the main reading reading system, and a control means is provided for setting reading conditions and/or image processing conditions for the main reading based on the output of the light detection means of the pre-reading reading system. Information reading device. (2) The excitation light irradiation means in the main reading reading system and the pre-reading reading system scan the excitation light over the stimulable phosphor? A radiation image information reading device according to claim 1, characterized in that: