JPS6255640A - Reading method for radiation image information - Google Patents

Abstract

PURPOSE:To always reproduce a radiation image having an observation read shadow aptitude by discriminating an area of each split block, based on information related to split photographing, deriving a read condition at every area which has been discriminated in this way, and setting the corresponding read condition to every area, respectively, when executing a regular read. CONSTITUTION:A signal which has been outputted from an amplifier 209 is digitized by an A/D converter 211, and inputted as a pre-read image signal Sp to a regular read control circuit 314 of a regular read use reading part 40. In case only one radiation image information is accumulated and recorded in an accumulative phosphor sheet 103a (namely, except the case when split photographing is being executed), the regular read control circuit 341 determines a read gain set value (a), a recording scale factor set value (b), and a reproducing image processing condition set value (c) by, for instance, a histogram analysis, etc., based on accumulation recording information shown by the pre-read image signal Sp from the whole area of a sheet 103. The accumulative phosphor sheet 103 which has completed the pre-read in this way is transferred to the regular read use reading part 40.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention is directed to irradiating excitation light to a stimulable phosphor sheet on which radiographic image information is accumulated and recorded, thereby excitation light emitted from the stimulable phosphor sheet. A radiation image information reading method of photoelectrically detecting stimulated luminescence light to read the radiation image information, in particular, prior to main reading for visible image reproduction,
Pre-reading is performed to grasp the outline of the accumulated recorded information in advance, and when reading radiation image information from a stimulable phosphor sheet on which segmented imaging has been performed, optimal reading conditions are set for each segmented imaging area. The present invention relates to a radiation image information reading method.

(Technical Background and Prior Art of the Invention) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a portion of this radiation energy is emitted by fluorescent light. It is known that when this phosphor is accumulated in the body and is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy; The fluorophore is called a storage fluorophore.

Using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily recorded on a stimulable phosphor sheet, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. A photostimulated luminescent light is generated, and the resulting stimulated luminescent light is read photoelectrically to obtain an image signal.Based on this image signal, a radiation image of the subject is displayed on a recording material such as a photographic light-sensitive material or a display device such as a CRT. The applicant has already proposed a radiation image information recording and reproducing system that outputs radiation images as visible images.

(JP-A-55-12429, JP-A-56-11395, etc.) This system has practical advantages in that it can record images over an extremely wide radiation exposure range compared to conventional radiographic systems using silver halide photography. It has advantages. In other words, in stimulable phosphors, it is recognized that the photoelectricity of the emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range. Therefore, depending on various imaging conditions, radiation exposure Even if a varies considerably, the photoelectricity of the stimulated luminescence light emitted from the stimulable phosphor sheet is read by a photoelectric conversion means with the reading gain set to an appropriate value and converted into an electrical signal. By outputting a radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT using an electric signal, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained.

Furthermore, according to this system, radiation image information accumulated and recorded on a stimulable phosphor sheet 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 a radiographic image as a visible image on a display device such as the above, it is possible to obtain a very large effect that a radiographic image with excellent observation and interpretation suitability (diagnosis suitability) can be obtained.

In this way, in a radiation imaging system that uses a stimulable phosphor sheet, the reading gain can be set to an appropriate value to photoelectrically convert the stimulated luminescence light and output it as a visible image, so the radiation source fluctuations in radiation exposure ω due to fluctuations in the tube voltage or MAS value, fluctuations in the sensitivity of the stimulable phosphor sheet, fluctuations in the sensitivity of the photodetector, changes in each exposure due to subject conditions, or changes in radiation transmittance depending on the subject. Even if the energy accumulated in the stimulable phosphor differs due to different factors, or even if the radiation exposure transmission is reduced, it is possible to obtain radiographic images that are not affected by fluctuations in these factors. becomes.

However, in order to eliminate the effects of fluctuations in imaging conditions or to obtain 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, Recording patterns (hereinafter collectively referred to as "accumulated recorded information") determined by the part of the subject such as the abdomen, the imaging method such as plain radiography or contrast radiography, etc. are visualized for observation and interpretation. This is determined prior to outputting the image, and the reading gain is adjusted to an appropriate value based on the acquired accumulated recording information, and the recording scale and lid are adjusted to optimize the resolution according to the contrast of the recording pattern. When image processing such as gradation processing is to be performed on the read image signal, it is necessary to optimally set the image processing conditions.

As a method for grasping the accumulated record information of radiographic images before outputting visible images, Japanese Patent Laid-Open No. 58-67240
The method disclosed in No. This method uses excitation light of a lower level than the excitation light that should be irradiated during the reading operation (hereinafter referred to as "main reading") to obtain a visible image for observation and interpretation. Perform reading operations (hereinafter referred to as "read ahead") to grasp the accumulated record information of radiographic images accumulated and recorded on the stimulable phosphor sheet, grasp the outline of accumulated records of radiographic images, and read the main reading. When performing this, the reading gain is appropriately adjusted, the recording scale factor is determined, or the image processing conditions are determined based on this pre-read information.

Note that the excitation light used for pre-reading is at a lower level than the excitation light used for main reading because the effective energy of the excitation light that the stimulable phosphor sheet receives per unit area during pre-reading is lower than the excitation light used for main reading. This means that it is smaller than the actual value. Methods for making the pre-reading excitation light lower than the main reading excitation light include reducing the output of the excitation light source such as a laser light source, and using an ND filter, AOM, etc. in the optical path of the excitation light emitted from the light source. A method of attenuation, a method of providing a light source for pre-reading and a light source for main reading separately and making the output of the former smaller than the output of the latter, and a method of increasing the beam diameter of the excitation light,
Examples include a method of increasing the scanning speed of excitation light and a method of increasing the transport speed of the stimulable phosphor sheet.

According to the above method, the recording state and recording pattern of the radiographic image information accumulated and recorded on the stimulable phosphor sheet can be known in advance before the actual reading, so the reading system has an exceptionally wide dynamic range. By appropriately adjusting the reading gain based on this recorded information, determining the recording scale factor, and applying signal processing according to this recording pattern to the electrical signal after reading, even without using It becomes possible to obtain radiographic images with excellent suitability for observation and interpretation.

By the way, when radiographic image information is stored and recorded (photographed) on the stimulable phosphor sheet described above, so-called divided photographing is often performed. This divided imaging is a transport method in which the recording area of the stimulable phosphor sheet is divided into a plurality of sections and radiation for the storage recording is irradiated to each section. According to this divisional imaging, for example, when photographing a small part on a large stimulable phosphor sheet, it is possible to record multiple parts on one stimulable phosphor sheet, which is economical. Furthermore, the processing speed for recording and reading radiation image information is also improved.

However, when reading radiation image information from a stimulable phosphor sheet that has been photographed in sections as described above, if the reading conditions are determined based on the above-mentioned pre-reading, the reading conditions may become inappropriate. be. That is, conventionally, the above-mentioned pre-reading has been performed on the entire recording area of the stimulable phosphor sheet or a partial area close to it, and therefore the reading conditions determined based on the pre-read image signal obtained by this pre-reading are , is determined to be appropriate for the entire radiographic image information that has been stored and recorded. However, in segmented imaging, the radiation dose irradiated to each segment may differ greatly from each other, and in such a case, the reading conditions determined as above may be It happens that the information becomes inappropriate. In an extreme example, for example, if a stimulable phosphor sheet is divided into two sections and each section is irradiated with radiation with a particularly high penetration and a particularly low ta amount, and radiological image information is stored and recorded, the above-mentioned method can be used. The reading conditions determined based on the read-ahead are optimal for image information that is intermediate between the two pieces of radiographic image information that are actually stored and recorded.
The information may become inappropriate for either of the two pieces of radiation image information. Such problems arise not only due to differences in the irradiation radiation dose, but also due to differences in the imaging sites and imaging methods in the Sendai divisions.

(Objective of the Invention) Therefore, an object of the present invention is to provide a radiation image information reading method that can eliminate the above-mentioned problems.

(Structure of the Invention) The radiographic image information reading method of the present invention is a radiation image information reading method that performs the above-mentioned main reading, and determines the reading conditions for performing the main reading based on the information obtained by this pre-reading. In the image information reading method, when reading radiation image information from a stimulable phosphor sheet with 1M divided shadows as described above, the area of each divided section is identified based on the information regarding divided imaging, and these The reading condition is determined for each identified area, and when performing the main reading, the corresponding reading condition is set for each area.

(Actual fMg) Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

FIG. 1 shows a radiation image information recording and reproducing system for reading radiation image information using a method according to one embodiment of the present invention. This radiation image information recording and reproducing system basically includes a radiation image capturing section 20, a prefetch reading section 30,
It is composed of a reading section 40 for actual reading and an image reproduction section 50. In the radiation image capturing section 20, for example,
A subject (subject) 101 from a radiation source 100 such as a radiation tube
Radiation 102 is irradiated toward. This subject 10
As described above, the stimulable phosphor sheet 103 that accumulates radiation energy is placed at the position where the radiation 102 that has passed through the stimulable phosphor sheet 10 is irradiated.
3, transmitted radiation image information of the subject 101 is accumulated and recorded.

The stimulable phosphor sheet 103 on which the radiation image information of the subject 101 has been recorded in this manner is sent to the pre-reading reading section 30 by sheet transport means 110 such as a transport roller. In the pre-reading reading section 30, the pre-reading laser light source 2
The laser beam 202 emitted from the laser beam 2
A filter 2 that cuts the wavelength range of stimulated luminescent light emitted from the stimulable phosphor sheet 103 by excitation of 02
03, the light is linearly deflected by a light deflector 204 such as a galvanometer mirror, and is incident on the stimulable phosphor sheet 103 via a plane reflecting mirror 205. Here, the laser light source 201 is selected so that the wavelength range of the laser light 202 as excitation light does not overlap with the wavelength range of the stimulated luminescence light emitted by the stimulable phosphor sheet 103. On the other hand, the phosphor sheet 103 is moved by a sheet transport device such as a transport roller.
The phosphor sheet 103 is transported by the step 210 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 the laser light 202 . Here, laser light source 2
01, the beam diameter of the laser beam 202, the scanning speed of the laser beam 202, and the transport speed of the stimulable phosphor sheet 103. It is selected to be smaller than that of the main reading performed at 40.

When the laser beam 202 is irradiated as described above, the stimulable phosphor sheet 103 emits stimulated luminescence light corresponding to the radiation energy stored therein, and this luminescent light is transmitted to the pre-reading light guide. 201. The stimulated luminescence light is guided through the light guide 207, exits from the exit surface, and is received by a photodetector 208 such as a photomultiplier. 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 light in the wavelength range of the excitation light, so that only the stimulated luminescence light is transmitted. It can be detected. The detected stimulated luminescence light is converted into an electrical signal carrying accumulated recording information and amplified by an amplifier 209. The signal output from the amplifier 209 is digitized by the A/D converter 211 and inputted to the main reading control circuit 314 of the main reading reading section 40 as a pre-read image signal Sp.

This book reading control circuit 314 controls the stimulable phosphor sheet 10
When only one radiographic image information is stored and recorded in 3a (that is, other than when the above-mentioned divided radiographs are performed)
In this step, the reading gain setting value a1 recording scale factor setting value b1 reproduction image processing condition setting value C is determined based on the accumulated recording information indicated by the prefetched image signal Sp from the entire area of the sheet 103, for example, by histogram analysis or the like.

The stimulable phosphor sheet 103 that has undergone pre-reading as described above is transferred to the main reading reading section 40.

In the main reading reading section 40, the main reading laser light source 301
The laser beam 302 emitted from this laser beam 302
A filter 303 that cuts the wavelength range of stimulated luminescence light emitted from the stimulable phosphor sheet 103 by excitation of the stimulable phosphor sheet 103.
After passing through, the beam diameter is strictly adjusted by a beam expander 304, linearly deflected by an optical deflector 305 such as a galvanometer mirror, and then passed through a flat reflector 306 to a stimulable phosphor sheet. 103. There is a distance f between the optical deflector 305 and the plane reflecting mirror 306.
A θ lens 301 is arranged so that the beam diameter of the laser beam 302 scanning the stimulable phosphor sheet 103 is made uniform. On the other hand, the stimulable phosphor sheet 103 is transported in the direction of the arrow 308 by a sheet transport means 320 such as a transport roller to perform sub-scanning, and as a result, the entire surface of the stimulable phosphor sheet 103 is irradiated with laser light. Ru. When irradiated with the laser beam 302 in this manner, the stimulable phosphor sheet 103 emits stimulated luminescence light with an amount of light corresponding to the radiation energy stored and recorded therein, and this luminescent light is directed to the main reading light guide 309. incident. Stimulated luminescent light guided through the main reading light guide 309 while undergoing repeated total reflection is emitted from its exit surface and is received by a photodetector 310 such as a photomultiplier. Photodetector 3
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.

The output of the photodetector 310 that photoelectrically detects the stimulated luminescent light representing the radiation image recorded on the stimulable phosphor sheet 103 has a read gain based on the read gain setting la determined by the control circuit 314. The electric signal is amplified to an appropriate level by the amplifier 311 set to . The amplified electrical signal is input to the A/D converter 312, and based on the recording scale factor setting value, it is converted into a digital signal with a recording scale factor suitable for the signal fluctuation width, and is input to the signal processing circuit 313. . The digital signal is subjected to signal processing (image processing) in the signal processing circuit 313 based on the reproduction image processing condition setting value C so as to obtain a radiation image with excellent observation and interpretation suitability, and is output.

The read image signal (actual read image signal) So output from the signal processing circuit 313 is transmitted to the optical modulator 401 of the image reproducing unit 50.
is input. In this image reproducing unit 50, a laser beam 403 from a recording laser light source 402 is transmitted to an optical modulator 40.
1, it is modulated based on the actual reading image signal So input from the signal processing circuit 313, and is transmitted to the scanning mirror 404.
The light beam is deflected by the light beam and scans over a photosensitive material 405 such as photographic film. The photosensitive material 405 is then transported in a direction perpendicular to the scanning direction (arrow 406 direction) in synchronization with the scanning, and a radiation image based on the actual reading image signal SO is output onto the photosensitive material 405. In addition to the method described above, various other methods can be used to reproduce the radiographic image, such as the above-mentioned display using CR.

Here, in the radiation image capturing section 20, the stimulable phosphor sheet 103 may have a split crystal shape as shown in FIG. 2, for example. Hereinafter, the reading conditions for reading radiation image information from the stimulable phosphor sheet 103 subjected to such divided imaging, that is, the determination of the reading gain setting value a and the recording scale factor setting value s, will be explained in detail.

The control circuit 314 includes, for example, the radiation image capturing unit 20
The divided shooting information Sd is transmitted from a terminal device etc. installed near the
is now entered. This divided shooting information Sd
is information indicating a division format in divisional photography. For example, the example shown in FIG. 2 is a four-division photograph, and when such a photograph is taken, division photographing information Sd indicating the four-division format is input to the control circuit 314. Divisional imaging is performed in accordance with a predetermined format (for example, in the case of four divisions, imaging is performed in each of the four equal divisions of the rice mold as shown in FIG. 2), and the force control circuit 314 is The area of each section is stored for each format, and based on the input divided shooting information Sd,
A pre-read image signal Sp is extracted for each area of each section. Then, for each set of extracted pre-read image signals Sp, the optimum reading gain setting value a and recording scale factor setting value S are determined. For example, when reading in advance the stimulable phosphor sheet 103 that has been photographed in divided sections as shown in FIG. , a3, am and recording scale factor setting values b1, b2, b3, b4 are determined.

The control circuit 314 uses the set value a l obtained as described above.
, a2 , a3 , a, and bl, b2, b3, b
4 is stored in the storage means in association with each section "1", "2", "3", and "4". Then read the book reading section 3.
The scraping control circuit 314 in which the main reading is performed at 0 receives a synchronization signal that is synchronized with the operation of the optical deflector 305 and the sheet transport means 320, and recognizes which section includes the area in which the main reading is being performed. Then, the reading gain setting value at, az, a3 or a4 corresponding to the partition (any of the partitions "1", "2", "3", or "4") and the recording scale factor setting value are set. , ,b
2, b3, or b4 are selectively read out from the storage means and sent to the amplifier 311 and the A/D converter 312, respectively. Therefore, the reading gain and the recording scale factor as reading conditions in the main reading can be set optimally for each of the accumulated recorded information of each divided section even if the accumulated recorded information is different for each divided section.

Here, the radiation image capturing section 20 and the prefetching reading section 3
0 are connected to each other via the sheet transporting means 110 or the like, and when the respective stimulable phosphor sheets 103 are transported to the pre-reading reading section 30 in the order of their appearance, the control circuit 314
It is sufficient to simply input the divided shooting information Sd in the shooting category. That is, for example, the control circuit 314 may be provided with a storage means for sequentially storing the divided photographing information Sd regarding each sheet 103, and the information Sd may be read out from the storage means in the order in which they are stored in synchronization with pre-reading. For example, each divided photographic information Sd corresponds correctly to each stimulable phosphor sheet 103 and is used for the signal extraction.

On the other hand, if the oil radiation image capturing section 20 and the pre-reading reading section 30 are independent from each other and the stimulable phosphor sheet 103 is not necessarily subjected to pre-reading during imaging, each stimulable phosphor sheet 103 identification codes (for example, barcodes, etc.) are input into the control circuit 314 together with the divided photographing information Sd, and the information Sd is stored in a storage means in association with the above identification code, so that the information Sd is stored in the storage means during pre-reading. The identification code may be read from the phosphor sheet 103, and the divided photographing information Sd corresponding to the code may be read from the storage means and used for signal extraction.

Of course, with respect to the stimulable phosphor sheet 103 in which one piece of radiation image information is stored and recorded over the entire recording area, the control circuit 314 is configured not to perform the above-described signal extraction. To do this, for example, for such a sheet 103, the divided shooting information Sd is not input to the control circuit 314, and in such a case, the control circuit 3
14 may determine one reading gain setting value a and one recording scale factor setting value S, respectively, based on all the pre-read image signals Sp.

As described above, based on the accumulated record information grasped by pre-reading, the read gain of the amplifier 311 and the A/D converter 312 are
Although we have described an actual mode of optimally setting the recording scale factor for each divided section, for example, the photodetector 310
When a photomultiplier or the like is used, the high voltage is also a reading condition that affects the reading sensitivity.
The method of the present invention can be similarly applied to optimally set other reading conditions such as the high voltage of the photomultiplier for each divided section.

In addition, in the example of divided imaging shown in Fig. 2, radiographic image information is accumulated and recorded (@shadow) in each divided section, but for example, as shown in Fig. 3, Some of them may not be filmed. Therefore, in addition to the above-mentioned division format, information indicating the division section in which the photograph was actually taken is inputted to the control circuit 314 as the divided photographing information Sd. It is also possible to configure the image forming apparatus so as to identify the sections that have not been created, and to set no particular reading conditions for the sections that have been identified. In such a case, it is meaningless to send the actual reading image signal SO regarding that section to the image reproduction section 50, so for the section for which no reading conditions have been set, for example, the A/D change W! The device 312 may automatically output a signal indicating the lowest concentration. This is preferable because it is possible to prevent black spots and the like due to noise components from occurring in areas where imaging has not been performed in the radiation image reproduced by the image reproduction unit 50. Further, in addition to the above case, actual reading may not be performed for sections for which reading conditions have not been set. By doing so, no time is wasted in reading the book, and the processing time for reading the book is shortened.

Furthermore, when the radiation irradiation field is narrowed down in each divided section, this irradiation field is recognized when determining the reading conditions for each divided section, and the pre-read image signal Sp only within the recognized area is
It is preferable to determine the reading conditions based on the following. In this way, the determined reading conditions will not be influenced by the pre-read image signal Sp from outside the field of radiation irradiation, and will be more appropriate for the accumulated recorded information regarding the subject. In order to recognize the radiation irradiation field, for example, a method such as that proposed by the present applicant in Japanese Patent Application No. 160355/1982 may be used.

Furthermore, the apparatus shown in FIG. 1 has separate reading systems for main reading and reading systems for pre-reading.
As shown in No. 67242, the reading system for main reading and the reading system for pre-reading are used together, and when the pre-reading is completed, the stimulable phosphor sheet is returned to the reading system by the sheet transport means and the main reading is performed. The excitation light energy adjusting means may be used to adjust the excitation light energy to be smaller than that during main reading, and the method of the present invention is also applicable when reading radiation image information using such an apparatus.

(Effects of the Invention) As explained in detail above, according to the radiation image information reading method of the present invention, when determining the reading conditions for main reading based on pre-reading, each accumulation of divided imaging areas of the stimulable phosphor sheet is Even if the recorded information is significantly different from each other, it is possible to set the optimum reading conditions for each piece of accumulated recorded information. Therefore, according to the method of the present invention, it is possible to always reproduce radiographic images with excellent suitability for observation and interpretation.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a radiation image information recording and reproducing system for reading radiation image information according to an embodiment method of the present invention. FIGS. FIG. 3 is a schematic diagram showing the state of recording radiation image information. 20... Radiographic image #1 imaging section 30... Reading section for pre-reading 40... Reading section for main reading 100...
・Radiation Q411 source 101...Subject 10
2... Radiation 103... Accumulative phosphor sheet 201... Laser light source for pre-reading 202... Laser light for pre-reading 204... Optical deflector for pre-reading 208... Photodetector for pre-reading 210 ... Sheet transport means for pre-reading 301 ... Laser light source for main reading 302 ... Laser light for main reading 305 ... Optical deflector for main reading 310 ... Photodetector for main reading 311 ...'IJ
I width unit 312...A/D converter 313...
Signal processing circuit 314...Control circuit 320...Actual reading sheet transport means a...Reading gain setting value b...Recording scale factor setting value sp...Pre-reading image signal SO...Actual reading image signal Sd ...Divided shooting information Figure 2 Figure 3

Claims (1)

[Claims] (1) Excitation light is irradiated onto a stimulable phosphor sheet on which radiation image information of the subject is stored and recorded, and the stimulated luminescence emitted from the sheet by the irradiation with excitation light is photoelectrically read by a photodetector. A summary of the image information accumulated and recorded on the sheet by irradiating the sheet with excitation light at a lower level than the excitation light used for this main reading in advance, prior to the main reading to obtain an image signal for visible image reproduction. In the radiation image information reading method, the radiation image information reading method performs pre-reading to read the radiation image, determines reading conditions for performing the main reading based on the information obtained by this pre-reading, and performs the main reading according to these conditions. When reading the radiation image information from a stimulable phosphor sheet that has been imaged separately by irradiating radiation to each of a plurality of sections when accumulating and recording information, , identifying each region, determining the reading conditions for each of the identified regions, and setting corresponding reading conditions for each region when performing the main reading. Image information reading method.