JPH0246931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention causes radiation image information to be stimulated to emit light from a stimulable phosphor sheet by irradiating the stimulable phosphor sheet storing 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.

Certain types of fluorophores are exposed to radiation (X-rays, α-rays, β-rays,
When irradiated with γ-rays, ultraviolet rays, etc., a part of this radiation energy is accumulated in the phosphor, and when this phosphor is irradiated with excitation light such as visible light, the phosphor increases depending on the accumulated energy. is known to exhibit stimulated luminescence, and phosphors exhibiting this property are called stimulable phosphors.

Using this stimulable phosphor, radiation image information of the human body, etc. is recorded once on the stimulable phosphor provided on the sheet, and this phosphor sheet is scanned with excitation light such as a laser beam. A radiation image in which stimulated luminescence is generated, the resulting stimulated luminescence is read out photoelectrically to obtain an image signal, and based on this image signal, it is output as a visible image to a recording material such as a photographic light-sensitive material, CRT, etc. An information reading method has already been proposed by the applicant. (JP-A-55-12429, JP-A No. 56-11395, etc.) This method is extremely capable of recording images over an extremely wide radiation exposure range compared to conventional radiographic systems that use silver halide photography. It has practical advantages. In other words, in stimulable phosphors, 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. Even if the amount of radiation exposure varies considerably depending on the photographing conditions, the amount of light emitted is read by the photoelectric conversion means by setting the reading gain to an appropriate value and converted into an electrical signal, and this electrical signal is used to perform photographic exposure. A radiation image that is not affected by fluctuations in radiation exposure can be obtained by outputting it as a visible image on a recording material such as a recording material or a display device such as a CRT.

In addition, according to this system, the radiation image information accumulated and recorded in the stimulable phosphor is converted into an electrical signal, then subjected to appropriate signal processing, and this electrical signal is used to produce recording materials such as photographic light-sensitive materials, CRTs, etc. By outputting the radiation as visible light to a display device, a very large effect can be obtained in that a radiation image with excellent suitability for observation and interpretation (diagnosis) can be obtained.

In this way, in a radiation imaging system using a stimulable phosphor, the reading gain can be set to an appropriate value to photoelectrically convert the stimulated luminescence light and output it as a visible image. tube voltage or
Fluctuations in radiation exposure due to fluctuations in MAS values, 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. In addition, by first converting the stimulated luminescence light into an electrical signal and 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, improving the suitability for observation and interpretation. It becomes possible to do so.

However, in order to eliminate the influence of fluctuations in imaging conditions or to obtain radiographic images with excellent observation and interpretability, 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 imaging, etc. (hereinafter referred to collectively as "accumulated recorded information") can be It is essential to understand this prior to outputting the image, and to adjust the reading gain to an appropriate value or perform appropriate signal processing based on the accumulated recorded information thus obtained.

Furthermore, in order to obtain radiographic images that are highly suitable 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 recorded pattern.

A method disclosed in Japanese Patent Laid-Open No. 55-50180 is known as a method of grasping accumulated recorded information of radiation image information prior to outputting a visible image.
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, we can grasp the accumulated recording information of radiation image information, and based on this information, we perform appropriate signal processing to obtain radiation images that are highly suitable for observation and interpretation. It is something. 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, thereby eliminating the influence of fluctuations in imaging conditions. Alternatively, it is possible to obtain radiographic images that are suitable for observation and interpretation, but
Since the radiation irradiation section and the radiation image information reading section are usually located at a distance, a signal transmission system must be constructed between them, making the equipment complicated and increasing costs. The disadvantage is that it 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. A method of estimating the recording state or recording pattern of the radiographic image information that has been used is also considered, but in addition to the drawbacks of the method disclosed in JP-A No. 55-50180, this method Since it is not used as a detection means, it can only indirectly infer the accumulated recorded information of image information accumulated and recorded in the stimulable phosphor.
The drawback was that the reliability of the information obtained in this way was low.

The present invention provides a method for easily and accurately detecting accumulated 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 easily and accurately detect radiographic image information stored in a stimulable phosphor prior to a reading operation to obtain a visible image for observation and interpretation. The object of the present invention is to provide a method for reproducing 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 excitation light energy that should be Using low-energy excitation light, a reading operation (hereinafter referred to as "pre-reading") is performed to grasp the accumulated recorded information of radiation image information stored in the stimulable phosphor in advance prior to the main reading. After reading the accumulated radiographic image information and then performing the actual reading, the reading gain was appropriately adjusted based on the pre-read information, or appropriate signal processing was performed. Obtain radiographic images with no effects or excellent suitability for observation and interpretation.
It has been found that the above objectives are achieved. Even if one selects a stimulable phosphor that is considered to have the highest sensitivity at present, the amount of stimulated luminescence emitted by the stimulable phosphor upon excitation light irradiation is extremely weak, so it is important to Until now, it was considered an essential requirement for this system that the amount of light should be detected by a photodetector (Japanese Patent Application Laid-Open No.
(No. 12492, No. 55-48674, No. 55-87970, etc.)
In light of this, the above findings are extremely surprising, as it is nothing short of absurd to intentionally dissipate the radiation energy stored in the storage phosphor by pre-reading the book before reading the book. .

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 images that are suitable for observation and interpretation, it is necessary to adjust the reading gain or set the optimal signal processing conditions so that the radiological image information accumulated and recorded in the stimulable phosphor through pre-reading must be adjusted. As long as it can be grasped to a sufficient extent to be used for selection, in other words, as long as the stimulated luminescence light emitted from the stimulable phosphor can be sufficiently detected in the above sense, the ratio of the energy of the excitation light of the pre-reading and the main reading. The smaller the value, the better, 50%
or less, preferably 10% or less, more preferably 3%
The following are desirable. The lower limit of this ratio is determined by the accuracy of the pre-read stimulated luminescence light detection system.

In the present invention, methods for making the energy of the excitation light in pre-reading smaller than the energy in main reading include methods of reducing the output of the laser light source, increasing the beam diameter of the laser light, and increasing the scanning speed of the laser light. Any known method can be used, such as a method of 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 stimulable phosphor has a characteristic of fading over time. Therefore, in order to effectively use the recorded information obtained by pre-reading for main reading, It is desirable to minimize the time it takes to read the book. 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 decreases approximately 1 hour after recording. Approximately 10% of radiation energy is lost due to attenuation, but it is recognized that the rate of attenuation decreases after that. In this case, the accumulated record information obtained by pre-reading is used to detect the accumulated record information of the radiographic 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 signal processing is performed, a radiation image with sufficient suitability for observation and interpretation can be obtained for practical use. 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% or less, and it is guaranteed that radiological images with sufficient suitability for observation and interpretation for practical purposes will be obtained. ,preferable.

According to the present invention, since it is possible to know in advance the recording state of radiographic image information stored and recorded in the stimulable phosphor, it is possible to read the recorded information without using a reading system having an exceptionally wide dynamic range. By appropriately adjusting the reading gain based on the information, it is possible to obtain radiographic images that are 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 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 shorten the reading time.

In the present invention, it is preferable that the wavelength range of the excitation light and the wavelength range 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. Preferably, the light body is selected. Specifically, Japanese Unexamined Patent Publication No. 1983-
As disclosed in Publication No. 12492, 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.

As described above, examples of stimulable phosphors that emit stimulated luminescent light of 300 to 500 nm and can be preferably used in the present invention include rare earth element-activated alkaline earth metal fluorohalide phosphors [specifically, ,
(Ba _1-x-1 , Mg _x , Ca _y )FX described in JP-A-55-12143: aEu ²⁺ (X is Cl
and Br, x and y are 0<x+y0.6 and xy≠0, and a is
10 ^-6 a5×10 ^-2 ), - JP-A-55-12145
(Ba _1-x , M〓 _x ) FX described in the publication:
yA (However, M〓 is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce, Tm,
At least one of Dy, Pr, Ho, Nd, Yb and Er, x is 0x0.6, y is 0y0.2), etc.; ZnS described in Japanese Patent Application Laid-Open No. 12142/1982: Cu, Pb, BaO・xAl ₂ O ₃ :Eu (however, 0.8
x10) and M〓O・xSiO ₂ :A (however, M〓 is
Mg, Ca, Sr, Zn, Cd or Ba, A is
Ce, Tb, Eu, Tm, Pb, Tl, Bi or Mn, and x is 0.5x2.5); and JP-A-55
−LnOX described in Publication No. 12144: xA (However, Ln
is at least one of La, Y, Gd and Lu
1, X is at least one of Cl and Br,
A is at least one of Ce and Tb, x is 0<x<0.1); and the like. Among these, rare earth element-activated alkaline earth metal fluorohalide phosphors are preferred, and among these, barium fluorohalides shown as specific examples are particularly preferred because of their excellent stimulable luminescence.

Furthermore, metal fluorides are added to barium fluorohalide phosphors as disclosed in JP-A-56-2385 and JP-A-56-2386, or as disclosed in JP-A-56-74,175. It is preferable to add at least one of a metal chloride, a metal bromide, and a metal iodide as described above because the stimulated luminescence is further improved.

Further, as disclosed in JP-A No. 55-163500, when the phosphor layer of the stimulable phosphor prepared using the above-mentioned stimulable phosphor is colored with a pigment or dye, the final This is preferable because the sharpness of the image can be improved.

The signal processing used in the present invention includes:
JP-A-55-87970, JP-A-56-11038, JP-A-56-
No. 75137, No. 56-75139, No. 56-75141, No. 56
−Frequency processing disclosed in JP-A No. 104645, etc., JP-A No. 55-116339, JP-A No. 55-116340, JP-A No. 55-88740
For example, the gradation processing disclosed in No.

Hereinafter, embodiments of the present invention will be described 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 is a photographing section, 2 is a pre-reading reading section, 3 is a main reading reading section, and 4 is a reproduction/recording section.

In the imaging unit 1, X-rays emitted from an X-ray source 101 toward a subject 102 are absorbed by a stimulable phosphor sheet 103 after passing through the subject 102, and the phosphor sheet 103 absorbs the X-ray image information is accumulated and recorded. The phosphor sheet 103 on which the X-ray image information has been stored and recorded in this way is sent to the pre-reading section 2.

In the pre-reading reading unit 2, the laser beam 202 emitted from the pre-reading laser light source 201 is passed through a filter 203 which cuts out the wavelength range of stimulated luminescence light emitted from the stimulable phosphor sheet 103 by excitation of the laser beam 202. After passing through the plane reflecting mirror 205 by an optical deflector 204 such as a galvano mirror,
The light is incident on the stimulable phosphor sheet 103 through one-dimensionally deflected. 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 moved 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 laser light source 20
1, 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 laser beam 202 for pre-reading is smaller than that for 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. 20
7. This light guide sheet 207 has a linear incident surface, and the stimulable phosphor sheet 1
The light emitting surface is arranged adjacent to and facing the scanning line 03, and its exit surface is annular, and is brought into close contact with the light receiving surface of a photodetector 208 such as a photodetector. This light guiding 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 guide sheet 207, exits from the exit surface, and is received by the photodetector 208. The preferred shape, material, etc. of the light-guiding sheet are disclosed in Japanese Patent Application Laid-Open No. 1986-
It is disclosed in No. 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 the stimulated luminescence light and cuts out light in the wavelength range of the excitation light, and detects only the stimulated luminescence light. It's getting wet. The output of the photodetector 208 is amplified by an amplifier 209 and
The image is output as a visible image on an output device 210 such as the following. 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 reading section 3 for main reading, a laser beam 302 emitted from a laser light source 301 for main reading is passed through a filter that cuts out the wavelength range of stimulated luminescence light emitted from the stimulable phosphor sheet 103 by excitation of the laser beam 302. After passing through 303, the beam
The size of the beam diameter is strictly adjusted by an expander 304, and an optical deflector 3 such as a galvano mirror is used.
05, the light is deflected onto the stimulable phosphor sheet 103 through a plane reflecting mirror 306, and then enters the stimulable phosphor sheet 103. An fθ lens 307 is arranged between the optical deflector 305 and the plane reflecting mirror 306, and the phosphor sheet 103
Even when the laser beam 302 scans the top, it always has a uniform beam diameter. On the other hand, the phosphor sheet 103 is moved in the direction of arrow 308 to perform sub-scanning, and as a result, the entire surface of the phosphor sheet 103 is irradiated with laser light. When the laser beam 302 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 light guide sheet for book reading. 3
It is incident on 09. The light guide sheet 309 for main reading has the same material and structure as the light guide sheet 207 for prereading. The 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. On the light receiving surface of the photodetector 310,
A filter that selectively transmits only the wavelength range of the stimulated luminescent light is attached, and the photodetector 310 is designed to detect only the stimulated luminescent light. The output of the photodetector 310 is amplified by an amplifier 311, A/D converted by an A/D converter 312, and then processed by a signal processing circuit 313 so that an X-ray image excellent in observation and interpretation is obtained. undergo signal processing. Amplification factor of amplifier 311, A/D converter 31
2 recording scale factor and signal processing circuit 3
The signal processing conditions in 13 are as follows:
Input device 315 based on the visible image obtained in
By manually operating the control circuit 314, the most appropriate conditions can be selected. Furthermore, by observing the visible image output on the output device 210 such as a CRT, the stimulable phosphor sheet 10 in the radiation image information reading device can be
Therefore, when using the overlay method or subtract method, which requires highly accurate positioning, by providing a control zone in front of the main reading system, it is possible to find the relative position of 3. The relative position of the light sheet 103 can be determined with high precision. The image signal output from the signal processing circuit 313 is input to the light modulation section 401 of the recording section 4.

In the recording section 4, a recording laser light source 402
A laser beam 403 is modulated by a light modulation unit 401 based on an image signal, and a laser beam 403 is transmitted to a scanning mirror 404.
A photosensitive material 405 such as a photographic film is scanned by the . 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, an X-ray image is output on the photosensitive material 405.

FIG. 2 is a schematic diagram of an X-ray image information recording system including an X-ray image information reading device according to another embodiment of the present invention.

In FIG. 2, the reading conditions for the main reading operation are determined using the accumulated record information of the X-ray image information accumulated and recorded in the stimulable phosphor obtained by pre-reading.
No. 1 in that it automatically controls image processing conditions, etc.
This differs from the embodiment according to the figures. That is,
The stimulated luminescent light detected by the photodetector 208 by pre-reading is converted into an electrical signal, and further transmitted to the amplifier 2.
09. The accumulated recording information of the X-ray image information output from the amplifier 209 is input to the control circuit 314 of the main reading reading section 3. Control circuit 3
14 outputs an amplification factor setting value a, a recording scale factor setting value b, and a reproduction image processing condition setting value c 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 the amplifier 311 whose sensitivity is set by the amplification factor setting value a, /D converter 312. The A/D converter 312 converts the digital signal into a digital signal using a scale factor suitable for the signal fluctuation width according to the recorded scale factor setting value b, and inputs the digital signal to the signal processing circuit 313. The signal processing circuit performs signal processing to obtain an X-ray image excellent in suitability for observation and interpretation based on the reproduction image processing condition setting value c, and outputs it to the recording unit 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.

Incidentally, the amount of radiation exposure generally varies by about two orders of magnitude depending on the commonly used imaging method or imaging conditions, and furthermore, depending on the subject, the radiation image accumulated and recorded on a single stimulable phosphor sheet may vary. The current value obtained as a result of photoelectric conversion of information is approximately 2
Since the amount of stimulated luminescence can vary by more than an order of magnitude, a reading system that can detect a light amount range of more than four orders of magnitude as a whole is required at least in the look-ahead section, but it is necessary to have a reading system that can handle such a large dynamic range. Reading is actually very difficult. Also,
In look-ahead reading, only low-level excitation light is originally irradiated, and the amount of stimulated luminescence light is small.
The photomal's dark current, the influence of weak external light that cannot be prevented from entering even though it is shielded, and the filter installed in front of the photomal cannot completely cut it out (the power of the excitation light is due to stimulated luminescence). There was a problem in that it was difficult to read accurate radiographic image information due to the influence of the excitation light (because it is several orders of magnitude larger than the excitation light).

To solve this problem, it is necessary to install a material with almost the same reflectance as the stimulable phosphor in a part of the excitation light scanning line and detect light other than stimulated luminescence light, or to detect radiation images. A stimulable phosphor sheet that stores and records radiographic image information to be read by installing a phosphor sheet whose stored energy level is known in advance in the reading section before reading the phosphor sheet on which information is stored and recorded. This can be solved by detecting light emitted from other sources and subtracting this detected value as a correction value from the value obtained by reading the stimulable phosphor sheet.

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

That is, when measuring a correction value, the switching circuit 212 is connected to the contact 214, and the correction value detected by the photodetector 208 and further amplified by the amplifier 209 is input to the correction value storage circuit 211.
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 the output device 210 such as a CRT is connected.
so that the output of amplifier 209 is transmitted.
The current corresponding to the image information obtained by the photodetector 208 is subtracted by the current corresponding to the correction value before reaching the amplifier 209. Specifically, the LED 216 emits light of a level 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. This is done by The reason for performing this correction before inputting the signal to the amplifier 209 is that band compression such as log conversion is normally required to obtain 4-digit information, so a log amplifier is used as the amplifier 209. This is to be done. In other words, it is difficult to perform correction after log conversion is performed because the amount of correction changes depending on the signal level, and it is desirable to perform correction in a linear region before 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 photomal. 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 it is preferable to increase the gain of the amplifier 209 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 according to FIG.
The conditions for main reading are set by manually operating the control circuit based on the visible image obtained by pre-reading.
A control system may be provided so that the visible image displayed on the output device 210, such as a CRT, is suitable for observation and interpretation. Conditions can be set to perform this.

Furthermore, the recording method in the recording unit 4 does not have to be a direct recording method using a laser light source; for example, the final signal obtained by the prefetch reading unit may be displayed as is on an output 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. Furthermore, various known recording methods such as recording using heat rays using a photosensitive recording material 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 an LED array having a wavelength range different from that of the stimulated emission light. In this case, an optical deflector such as a galvano mirror can be omitted.

Further, the photodetector does not have to be a single one with a light guide sheet, but it is also possible to use a plurality of photodetectors 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 sheet 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. Normally, in the case of an X-ray photograph, there is no image information to be observed and interpreted at the peripheral edge of the phosphor sheet, so for example, in a few centimeters of the peripheral area, pre-reading can be omitted, and if necessary in advance, When the storage recording area of radiation image information is known, it is sufficient to pre-read only that area, and by pre-reading only the effective area in this way, the reading time can be shortened.

Furthermore, 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 the photodetector. By doing so, the gain of the photodetector may be directly changed. This has the advantage that only the signal is amplified and the noise is not amplified.

[Brief explanation of drawings]

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 showing an embodiment of the present invention.
FIG. 3 is a correction circuit diagram used in a prefetch reading section. 1... Photography department, 101... X-ray source, 102...
Subject, 103...Storage phosphor sheet, 2...
Pre-reading reading unit, 201... Laser light source for pre-reading, 202... Laser light, 203... Filter, 204... Optical deflector, 205... Plane reflecting mirror, 206... Transfer direction, 207... Pre-reading guide Optical sheet, 208...Photodetector, 209...Amplifier, 210...Output device, 211...Correction value storage circuit, 212...Switching circuit, 213, 214...
...Contact, 215...Photocoupler, 216...
LED, 217...Photodiode, 3...Reading unit for main reading, 301...Laser light source for main reading,
302... Laser light, 303... Filter, 30
4...Beam expander, 305...Light deflector, 306...Plane reflecting mirror, 307...Fθ lens, 308...Transfer direction, 309...Light guide sheet for main reading, 310...Photodetector , 311...Amplifier, 312...A/D converter, 313...Signal processing circuit, 314...Control circuit, 315...Input device, 4...Recording unit, 401...Optical modulator, 40
2... Recording laser light source, 403... Laser light,
404...Scanning mirror, 405...Photosensitive material, 4
06...transfer direction.

Claims (1)

[Scope of Claims] 1. Radiation image information accumulated and recorded on the stimulable phosphor sheet is irradiated with excitation light to the stimulable phosphor sheet on which radiographic image information is accumulated and recorded. In a radiation image information reading method of emitting light and photoelectrically reading the obtained stimulated luminescence light, prior to main reading to obtain a visible image for observation interpretation, an energy lower than the energy of excitation light used in the main reading is used. 1. A method for reading radiation image information, comprising performing pre-reading of the radiation image information stored and recorded on the stimulable phosphor sheet using excitation light. 2. The radiation image information reading method according to claim 1, wherein the main reading and pre-reading are performed by scanning the excitation light over the stimulable phosphor sheet. 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.