JPS5867240A - System 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 The present invention produces photostimulated luminescence from a stimulable phosphor sheet that records all radiation image information by fully irradiating the stimulable phosphor sheet that stores all of the radiation image information with excitation light. The present invention relates to a radiation image information reading method for photoelectrically reading the obtained stimulated luminescence light using a photodetector.

When certain types of phosphors are irradiated with radiation (X-rays, alpha rays, beta rays, gamma rays, ultraviolet rays, etc.), some of this radiation energy is accumulated in the phosphor, causing it to emit visible light. It is known that when fully irradiated with excitation light such as, a phosphor exhibits stimulated luminescence depending on the accumulated energy, and a phosphor exhibiting this property is called a stimulable phosphor.

By making full use of this stimulable phosphor, radiation image information of the human body, etc. is recorded on the stimulable phosphor provided on the -H sheet, and this phosphor sheet is scanned with excitation light from a laser source, etc. The resulting photostimulated luminescent material is photoelectrically read out to obtain an image signal, and based on this image signal, it is output as a visible image on a recording material such as a photographic light-sensitive material, CR, T, etc. The present applicant has already proposed a radiographic image recording and reading method that allows
1i395 etc. ) This method has the very practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range. Radiation exposure amount is quite wide 11'l: Even if the amount of radiation exposure fluctuates, the amount of light emitted by the reading gain is set to an appropriate value, and the photoelectric conversion means reads it and converts it into an electrical signal. A radiation image that is unaffected by fluctuations in radiation exposure can be obtained by outputting it as a visible image to a recording material such as a photographic light-sensitive material or to a human device such as a CRT.

In addition, according to this system, after converting the radiation image information accumulated and recorded in the stimulable phosphor into an electric signal, all appropriate signal processing is performed, and this electric signal sound is used to produce a recording material such as a photographic light-sensitive material, C1 ( By outputting the image as a visible image to a human foot device such as T, an extremely large effect can be obtained in that a complete radiation image with excellent suitability for observation and interpretation (diagnosis) can be obtained.

In this way, in a radiographic imaging system that uses all stimulable phosphors, it is possible to set the reading gain to an appropriate value, convert the photostimulated luminescence source to the source, and output it as a visible image. Fluctuations in radiation exposure amount due to fluctuations in tube voltage or IVIAS value, fluctuations in sensitivity of stimulable phosphors, fluctuations in sensitivity of photodetectors, changes in exposure amount due to subject conditions, or radiation transmittance depending on the subject. Even if the stored energy stored in the stimulable phosphor differs due to differences in factors, or even if the total radiation exposure is reduced, radiographic images that are not affected by fluctuations in these factors can be obtained. Furthermore, by first converting the stimulated luminescent light into an electrical signal and then applying appropriate signal processing to this electrical signal, it is possible to obtain radiographic images suitable for diagnostic areas such as the chest and heart. , it becomes possible to completely improve the aptitude for observation and interpretation.

However, in order to eliminate the influence of fluctuations in imaging conditions or to record all radiographic images that are suitable for observation and interpretation, it is necessary to change the recording state of the radiographic image information accumulated and recorded on the stimulable phosphor sheet, or the chest and abdomen. Recording patterns (hereinafter referred to collectively as "accumulated recorded information") determined by the part of the subject, imaging method such as simple or contrast-enhanced, etc., are used to record visible images for observation and interpretation. It is essential to understand the information prior to output, and to adjust the reading gain to an appropriate value based on the accumulated recorded information thus obtained, or to perform appropriate signal processing.

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

In this way, as a method for grasping all accumulated recorded information of radiation image information before outputting a visible image, 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 entire accumulated record of radiographic image information is grasped, and appropriate signal processing is performed based on this information to produce radiographic image information that is highly suitable for observation and interpretation. . 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, so that it is possible to obtain a line image influenced by changes in imaging conditions. However, since the radiation irradiation section and the radiation image information reading section are usually located apart, a signal transmission system must be constructed between them, which makes the device complicated. However, it has the disadvantage that an increase in costs cannot be avoided.

Also, as disclosed in Japanese Patent Application Laid-Open No. 55-116340,
A non-storage phosphor is provided near the stimulable phosphor sheet, and a photodetector detects the light emitted by the non-storage phosphor when recording radiation image information, and the light is stored and recorded in the stimulable phosphor. It is also possible to consider a method of estimating the entire recording state or recording pattern of radiographic image information.
In addition to the shortcomings of the method disclosed in No. 50180, since the stimulable fluorescer itself is not used as a detection means, it is difficult to use the stimulable phosphor itself to detect the stored image information. The drawback was that the information obtained in this way was not reliable, as it was only an indirect guess.

The present invention provides a method for easily and accurately detecting radiographic image information stored in a stimulable phosphor prior to a reading operation to obtain a visible image for observation and interpretation. The purpose is to

Another object of the present invention is to detect radiographic image information stored in a stimulable phosphor simply and accurately prior to a reading reverse operation to obtain a visible image for full observation and interpretation. However, it is an object of the present invention to provide a method that can reproduce radiographic images with excellent diagnostic performance based on this information.

As a result of extensive research in order to achieve this objective, the present inventor has discovered that the excitation light to be irradiated during the reading reverse operation (hereinafter referred to as "real reading") to obtain a visible image for 1st interpretation. A reading reverse operation (hereinafter referred to as "first 9 - 8 - "reading") to understand the accumulated recorded information of radiation image information, and then perform actual reading, and adjust the reading gain appropriately based on the pre-read information, or perform appropriate signal processing. As a result, it has been found that radiographic images that are not affected by fluctuations in imaging conditions or have excellent suitability for observation and interpretation are obtained, and that the above object is achieved. Even if a stimulable phosphor that is considered to have the highest sensitivity at present is selected, the amount of stimulated luminescence emitted by the stimulable phosphor when irradiated with excitation light is extremely weak, so it is important to increase the amount as much as possible. Until now, it was considered essential for this system that the amount of light should be detected by a photodetector (Japanese Patent Laid-Open Nos. 55-12492 and 55-4867).
No. 4, No. 55-87970, etc.),
The above findings are extremely surprising, as it is nothing short of unreasonable to intentionally dissipate the radiation energy stored in the stimulable phosphor by performing pre-reading before the actual reading.

-in- 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 present invention, it is sufficient that the energy of the excitation light to be applied to the stimulable phosphor during pre-reading is lower than the energy of the excitation light during main reading. The closer the ratio of the excitation light energy of the pre-reading to that of the main reading is to 1, the smaller the amount of radiation energy remaining and accumulated during the main reading, but if this ratio is less than 1, the value of the reading gain should be adjusted appropriately. It has been found that radiological images suitable for observation and interpretation can be obtained by adjusting the However, in order to obtain radiographic image information that is highly suitable for observation and interpretation, it is necessary to use the accumulated recording information of the radiographic image information stored in the stimulable phosphor by read-ahead to adjust the reading gain or select the optimal signal processing conditions. The limit ratio that can be grasped to a sufficient extent for use, in other words, the limit ratio that can sufficiently detect stimulated luminescence light emitted from a stimulable phosphor in the above sense, is preferably as small as possible; Preferably it is 10% or less, more preferably 3 or less. The lower limit of this ratio is determined by the accuracy of the pre-read stimulated luminescence light detection system.

In the present invention, the energy of the excitation light in pre-reading can be made smaller than the energy of full-length reading by reducing the output of the laser light source, by increasing the beam diameter of the laser light, and by increasing the scanning speed of the laser light. All known methods can be used, such as increasing the transport speed of the stimulable phosphor sheet and increasing the transport speed of the stimulable phosphor sheet.

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 storage phosphor fades over time (Fading).
Therefore, in order to effectively use all of the recorded information obtained by pre-reading for main reading, it is desirable to make the total time until pre-reading complete reading as short as possible. However, according to the research of the present inventor, the attenuation of the radiation energy stored and recorded in the stimulable phosphor is greatest immediately after recording radiation image information on the stimulable phosphor, and 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%. In this case, the accumulated recorded information obtained by pre-reading is used to detect all accumulated recorded 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 reading conditions after reading. It has been found that even if signal processing is performed, 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, the difference in accumulated amount will always be 10 inches or less, and it is guaranteed that radiological images with sufficient suitability for observation and interpretation will be obtained for practical purposes, which is preferable. It's scary.

According to the present invention, since it is possible to know in advance the recording state of radiographic image information stored and recorded in a stimulable phosphor, this recorded information can be obtained without using a reading system having an exceptionally wide dynamic range. By appropriately adjusting the reading gain based on the above, it is possible to obtain radiographic images that are always suitable for observation and interpretation even when the imaging conditions vary.

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 signal processing according to the recording pattern is applied to the electrical signal after reading. 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 reduce the total reading time.

In the present invention, in order to improve the S/N ratio, it is preferable that the wavelength range of the excitation light and the wavelength range of the stimulated luminescent light do not overlap, and the excitation light source and the storage property are adjusted so as to satisfy such a relationship. Preferably, a phosphor is selected. Specifically, as disclosed in JP-A-55-12492, it is desirable that the excitation light wavelength be 600 to 700 nm and the stimulated emission light wavelength be 300 to 500 nm.

As described above, examples of stimulable phosphors that emit stimulated luminescence light of 300 to 500 nm and can be preferably used in the present invention include rare earth element-activated alkaline earth metal fluoronide phosphors [specifically In JP-A-55-1.2
It is described in Publication No. 143 (Bat-x -y
, Mgx, Cay) PX: aEu2+ (where X is at least one of C6 and Br, X and y are 0 and X+M, /: 0.6 and x y'<
O, a is 10 a, /; 5 X 10
), □ described in Japanese Patent Application Laid-Open No. 55-1214'5 (Ba1-x).

Mllx )FX:yA (However, Mll is Mg, Ca
, Sr, Zn and Cd, X is at least one of C1, Br and ■, A is Eu, 'rb, Ce, Tm, Dy,
At least one of Pr, Ho, Nd, Yb and Er, X is Ol x l O,6, y is 01y
10.2 'l:r) etc.]; JP-A-55-12142
ZnS described in the publication: Cu, Pb, Ba
0=xAlzo3:Eu (However, 0.8 l x! 1
0) OyoU MIIOxsioz:A (However, L M
IIFiMg, Ca, Sr, Zn, cc+ or Ba, A is Ce%Tb, Eu, Tm, P
b, Tl, Bi i or Mn, X is Q,
5 l x l 2.5); and JP-A-1988-
LnOX:xA described in Publication No. 12144 (Ln is at least one of La, Y, Gd and Lu, X is at least one of CI and Br, A is at least one of Ce and Tb) and X is 0 (x < 0.1). Among these, rare earth element-activated alkaline earth metal fluoronide phosphors are preferable, but among these, barium fluorolides, shown as a specific example, are particularly excellent in stimulable luminescence. preferable.

Furthermore, Japanese Patent Application Publication No. 1987 (1982) was published on barium fluorohalide phosphor.
-2385 Publication, 56-2386 Publication to which metal fluoride is added, or Japanese Patent Application No. 1984-
The addition of at least one of a metal chloride, a metal bromide, and a metal iodide as disclosed in No. 150873 is preferable because the stimulated luminescence is further improved.

Furthermore, as disclosed in JP-A-55-1.63500, the phosphor layer of a stimulable phosphor plate prepared using the above-mentioned stimulable phosphor is colored with a pigment or dye. This improves the sharpness of the finally obtained image, which is preferable.

The signal processing used in the present invention is as follows:
No. 5-87970, No. 56-11038, Patent application 1972
-151398, 54-151400, 54-
Frequency processing disclosed in JP-A-1.51402 and JP-A-54-168937, gradation processing disclosed in JP-A-55-116339, JP-A-5S-116340, JP-A-55-88740, etc. It will be done.

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

FIG. 1 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 Fig. 1, 1.1 is a photographing section, 2 is a pre-reading section,
Reference numeral 3 indicates a reading section for actual reading, and numeral 4 indicates a reproduction/recording section.

In the imaging unit 1, X@ irradiated from an X-ray source 101 toward a subject 102 passes through the subject 102 and is absorbed by the stimulable phosphor sheet 103, and the phosphor sheet 103 absorbs the X-ray one-plane image information is accumulated and recorded.

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 and passes through a filter 203 that cuts the entire wavelength range of the stimulated luminescent light emitted from the stimulable phosphor sheet 103.Then, the laser beam 202 is passed through a filter 203, which cuts the entire wavelength range of the stimulated luminescent light emitted from the stimulable phosphor sheet 103. The light is one-dimensionally deflected and incident on the stimulable phosphor sheet 103 via the multi-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 emission light from the stimulable phosphor. On the other hand, the phosphor sheet 103 is conveyed in the direction of the arrow 206 for sub-scanning, and as a result, the entire surface of the phosphor sheet 103 is irradiated with laser light. Here, the power of the laser light source 201, the beam diameter of the laser light 202,
The scanning speed of the laser beam 202 and the transport speed of the phosphor tube 103 are selected so that the energy of the laser beam 202 for pre-reading is smaller than that for main reading. When the laser beam 202 is irradiated in this way, the stimulable phosphor sheet 103 emits a stimulable luminescent light, and this luminescent light is incident on the pre-reading light guide sheet 207. The light guide zone 207 has a linear incident surface and is disposed adjacent to and opposite to the scanning line on the stimulable phosphor sheet 1o3, and an annular exit surface and a photomultiplier or the like. It is brought into close contact with the light receiving surface of the photodetector 208. 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 1o3 is guided through the light guide sheet 207, exits 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. 55-87970.
No. 56-11397, etc.

A filter is attached to the light-receiving surface of the photodetector 208, which transmits only light in the wavelength range of stimulated luminescence light and cuts light in the wavelength range of excitation light, and detects only stimulated luminescence light. It's getting wet. The output of the photodetector 208 is sent to the amplifier 209
The signal is amplified and output as a visible image onto an output device 210 such as a CRT. By visually observing this visible image, it becomes possible to grasp the accumulated recording information of the X-ray image information, that is, the recording state or recording pattern, in advance of the actual reading. The stimulable phosphor sheet 103 on which the pre-reading has been completed is transferred to the reading section 3 for main reading.

In the main reading reading unit 3, a main reading laser light source 30
The laser beam 302 emitted from 1 is this laser beam 302
After passing through a filter 303 that cuts the wavelength region of the stimulated luminescence light emitted from the stimulable phosphor 7-t 103 by excitation, the beam expander 304 strictly adjusts the beam diameter, The light is deflected onto the stimulable phosphor sheet 103 via a plane reflecting mirror 306 by a light deflector 305 such as -, and then enters the stimulable phosphor sheet 103. Source side 21 - A Jθ lens 307 is disposed between the inner device 305 and the plane reflecting mirror 306, and the laser beam 30 passes over the phosphor sheet 103.
2 is configured to always have a uniform beam diameter even when the beam is scanned. 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, stimulated luminescent light is emitted with an amount of light proportional to the energy, and this luminescent light is incident on the main reading light guiding sheet 309. The light guide sheet 309 for main reading has the same material and structure as the light guide sheet 207 for prereading. Stimulated luminescent light guided through the light guiding sheet 309 for main reading while undergoing repeated total reflection is emitted from its exit surface and is received by the photodetector 310. A filter that selectively transmits only the wavelength range of the stimulated luminescent light is attached to the light receiving surface of the photodetector 310, so that the photodetector 310 detects only the stimulated luminescent light. . Photodetector 31
The output of 0 is amplified by an amplifier 311, A/D converted by an A/D converter 312, and then sent to a signal processing circuit 31.
3, signal processing is performed to obtain an X-ray image with excellent suitability for observation and interpretation. Amplifier 31] amplification factor, A/D
The recording scale factor of the converter 312 and the signal processing conditions in the signal processing circuit 313 are determined to be the most appropriate by manually operating the control circuit 314 using the input device 315 based on the visible image obtained in the prefetch reading section 2. conditions can be selected. However, the relative position of the stimulable phosphor sheet 103 in the radiation image information reading device can be found by observing the entire visible image output on the output device 210 such as a CRT. When using the overlay method or subtract method that requires position alignment, it is possible to accurately determine the position by providing a control zone in front of the main reading system.The image signal output from the signal processing circuit 313 can be recorded. The light is input to the optical modulator 401 of the section 4.

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 scanning, the photosensitive material 405
An X-ray image is output above.

FIG. 2 shows X#i! which includes an X-ray image information reading device which is another embodiment of the present invention! FIG. 1 is a schematic diagram of an image information recording system.

In FIG. 2, xfj! is accumulated and recorded in the layered phosphor obtained by pre-reading. The embodiment differs from the embodiment shown in FIG. 1 in that the reading conditions, image processing conditions, etc. of the main reading operation are automatically controlled using the accumulated record information of the image information, that is, the photodetector 208 is
The stimulated luminescence light detected by is converted into an electrical signal and further amplified by an amplifier 209. The accumulated record information of the X-win image information outputted from the amplifier 209 is input to the control circuit 314 of the main reading reading section 3. The control circuit 3]4 is
Depending on the obtained accumulated recording information, the amplification factor setting value a, the recording scale factor setting value b, and the reproduction image processing condition setting value C are set.
Output.

The stimulated luminescent light detected by the photodetector 208 in the main reading is converted into an electrical signal, and after being amplified to an appropriate level electrical signal by the amplifier 311 whose sensitivity is set according to the amplification factor setting value a, A, /D conversion is performed. 312.

The A/D converter 312 converts the digital signal into a digital signal with a scale factor suitable for the signal fluctuation width according to the recording scale factor setting value, and inputs the digital signal to the signal processing circuits 3 and 3. The signal processing circuit performs signal processing based on the reproduction image processing condition setting value C so as to obtain an X-ray image excellent in suitability for observation and interpretation, and outputs it to the self-recording section 4.

In the recording section 4, X-ray image information is output and recorded as a visible image in the same manner as in the embodiment described above.

By the way, the amount of radiation exposure generally varies by about two orders of magnitude depending on the imaging method or imaging conditions that are normally used, and furthermore, depending on the subject, all of the radiation image information accumulated and recorded on a single stimulable phosphor sheet may vary. Since the current value obtained as a result of photoelectric conversion can vary by more than two orders of magnitude, a reading system that can detect a light amount range of stimulated luminescence light of about four orders of magnitude or more is required at least in the look-ahead section. In reality, it is very difficult to perform reading that corresponds to such a large dynamic range. In addition, in look-ahead reading, only low-level excitation light is originally irradiated, and the amount of stimulated luminescence light is also small, so ■ photomal dark current, ■
The influence of weak external light that cannot be prevented from entering even though the light is blocked, ■The filter installed on the front of the Photomul could not cut it completely (the power of the excitation light is much higher than that of the stimulated luminescence light). There was a problem in that it was difficult to read accurate radiographic image information due to the influence of the excitation light (because of the large number of orders of magnitude).

This problem can be solved by installing a material that has almost the same reflectance as the stimulable phosphor in a part of the scanning line of the total excitation light.
Before detecting light other than stimulated luminescence light or reading a phosphor sheet on which radiation image information is stored and recorded, a phosphor sheet whose stored energy level is known should be installed in the reading unit and read. This problem is solved by detecting the light sound emitted from sources other than the stimulable phosphor sheet that stores radiation image information, and subtracting this detected value as a correction value from the value obtained by reading the stimulable phosphor sheet. can do.

As a specific circuit, the one shown in FIG. 3 can be used.

That is, when measuring a correction value, the correction value detected by the switch 208 and further amplified by the amplifier 209 is input to the correction value storage circuit 211, and this correction value is held in the correction value storage circuit 211. When reading radiation image information, the switching circuit 212 is connected to the contact 214, and C1l
, T, etc., so that the output of the amplifier 209 is transmitted to an output device 210 such as. The current corresponding to the image information obtained by the photodetector 208 is subtracted by a current p corresponding to the correction value before reaching the amplifier 209. Specifically, the '1 LED 216 emits light with a level of light emission corresponding to the correction value held in the correction value storage circuit 211, the photodiode 217 receives the emitted light, and leaks a current corresponding to the correction value. It is done. The reason for performing the correction before inputting the signal to the amplifier 209 is that band compression such as log conversion is normally required to obtain four-digit vehicle information, so the amplifier 209
This is because a g amplifier is used. That is, after the log conversion is performed, it is difficult to perform correction because the amount of correction changes depending on the n level, and it is desirable to perform the correction in a linear region before the log conversion. The photocoupler 215 is used because it is resistant to noise and is suitable for processing weak signals. The photodiode 217 constituting the photocoupler 215 can also be replaced with a photomultiplier. Further, it is preferable that the gain of the amplifier 209 can be changed when detecting a correction value and when detecting radiographic image information. In other words, since the correction value itself is a very small value, in that case, the amplifier 20
It is preferable to increase the gain of 9 so that the correction value can be measured accurately.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made.

For example, in the embodiment shown in FIG. A control system may be provided so that the visible image displayed on the output device 210 such as T is suitable for observation and interpretation, and in this way, the control circuit can more easily perform appropriate processing. Conditions can be set to perform this.

Furthermore, the recording method in the recording section 4 does not have to be a direct recording method using a sensor light source. For example, the final signal obtained by the reading section for main reading may be displayed as it is on a recording device such as a CRT. Furthermore, the final radiation image displayed on a CRT or the like may be displayed on a video printer or the like. Further, various known recording methods such as recording with heat rays using a heat-sensitive recording material can be employed.

Furthermore, the V-za light source as an excitation light source in the pre-reading reading section and the main reading reading section can be replaced with an LED array having a wavelength range different from that of stimulated luminescence light.

In this case, an optical deflector such as a galvanometer mirror can be omitted.

Further, the photodetector does not have to be a single one with light-guiding sorting, but it is also possible to use a plurality of photomultiples or phototransistors arranged in a straight line in the main scanning direction.

Furthermore, it is also possible to uniformly expose the entire surface of the stimulable phosphor sorta and use a photodetector capable of two-dimensionally capturing the light, such as a television camera.

Furthermore, the pre-reading and the main reading may be performed by using a common reading section, using a single reading device, and changing the scanning conditions of the excitation light, etc.

Further, in the embodiment described above, pre-reading is performed over the entire surface of the stimulable phosphor sheet, but it is not necessarily necessary to perform over the entire surface of the phosphor sheet. usually,
In the case of X-ray photography, it is possible to omit pre-reading for a few areas around the periphery of the phosphor sheet, and the area where necessary radiation image information is stored and recorded is known in advance. In this case, it is sufficient to read ahead all of that area,
In this way, by pre-reading only the valid area, the total reading time can be reduced.

Furthermore, the reading gain can be adjusted by changing the total 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.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing another embodiment of the present invention, and FIG. 3 is a diagram of a correction circuit used in a prefetch reading section.

Claims (5)

[Claims] (1) By fully irradiating the stimulable phosphor sheet on which the radiation image information is stored and recorded with excitation light, the radiation image information stored on the stimulable phosphor sheet is fully stimulated to emit light. In a radiation image information reading method in which the obtained stimulated luminescence light is read photoelectrically, prior to the main reading to obtain a visible image for observation and interpretation, excitation with energy lower than the energy of the excitation light used in the main reading is performed. 1. A method for reading radiographic image information, which is characterized in that pre-reading is performed to read the radiographic image information that has been stored and recorded on the stimulable phosphor sheet using the stimulable phosphor sheet. (2) The radiation image information reading method according to claim 1, wherein the main reading and pre-reading are performed by scanning the entire surface of the stimulable phosphor sheet with the excitation light. (3) The radiation image information reading method according to claim 1 or 2, wherein the pre-reading is performed within one hour before the main reading. (4) The radiation image information reading method according to claim 2 or 3, wherein the scanning speed in the pre-reading is higher than the scanning speed in the main reading. (5) The radiation image information reading method according to claim 2 or 3, wherein the beam diameter of the excitation light in the pre-reading is larger than the beam diameter of the excitation light in the main reading. .