JPH0693076B2 - Radiation image information reading method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to radiation for performing main reading for reading an image signal for reproducing a visible image from a recording medium such as a stimulable phosphor sheet on which radiation image information is recorded. Regarding the image information reading method,
Particularly in detail, in a visible image (reproduced image) reproduced based on a read image signal, it is possible to prevent the density of a region of interest in the subject from changing depending on the photographing position of the subject. It is about the method.

(Prior Art) When a certain kind of phosphor is irradiated with radiation (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet ray, etc.), a part of this radiation energy is accumulated in the phosphor, It is known that when a phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated emission depending on the stored energy, and a phosphor having such a property is a stimulable phosphor (luminescent material). Exhaustible phosphor).

Using this stimulable phosphor, the radiation image information of a subject such as a human body is once recorded on a stimulable phosphor sheet, and the stimulable phosphor sheet is scanned with excitation light such as laser light to stimulate emission. Perform the main reading to generate light and photoelectrically read the obtained stimulated emission light to obtain the image signal for reproducing the visible image, perform the image processing on the main reading image signal obtained by this main reading, and The applicant has already proposed a radiation image information recording / reproducing system that outputs a radiation image of a subject as a visible image on a recording material such as a photographic photosensitive material or a display device such as a CRT based on the processed image signal. . (JP-A-55-12429, JP-A-56-11395, etc.) In the above-mentioned system, data is accumulated and recorded on the sheet for each individual image due to fluctuations in the subject or imaging region or fluctuations in radiation exposure. Variations in the radiation energy level range occur.

However, in the above system, the recorded image information accumulated and recorded on the sheet in each image in advance, in particular, the range of the radiation energy level accumulated and recorded in the sheet in each of the above images is grasped, and the individual image is recorded. By performing the main reading in accordance with the reading conditions such as the reading gain and the recording scale factor that are appropriately determined based on the recorded image information, the adverse effects such as the fluctuation of the radiation energy level range accumulated and recorded in each image are affected. It is possible to obtain a visible image excellent in aptitude for observation and interpretation, that is, a visible image in which, for example, necessary object image information is displayed in a density range suitable for observation and interpretation.

In addition, in the above system, the imaging region (head, chest, abdomen, etc.) of each image is acquired for each image so that a visible image suitable for a diagnostic purpose can be obtained with respect to the main reading image signal obtained by the main reading. Image processing is performed according to image processing conditions such as gradation processing conditions determined based on a shooting method (simple shooting, contrast shooting, etc.). However, for example, when the main reading is not performed according to the reading conditions appropriately determined based on the recorded image information of each image as described above,
It is desirable to determine the image processing conditions in consideration of not only the imaged region and the image capturing method as described above but also the recorded image information of the individual images that have been grasped in advance. By doing so, it is suitable for diagnostic purposes, for example. At the same time, it is possible to obtain a visible image excellent in observation / interpretation aptitude in which necessary image information is displayed in an appropriate density range.

A method disclosed in Japanese Patent Laid-Open No. 58-67240 is known as a method of grasping the recorded image information prior to the main reading and the image processing. This method uses excitation light of a lower level than the excitation light to be irradiated in the main reading for reading the image signal for reproducing the visible image, and is stored and recorded in advance in the stimulable phosphor sheet prior to the main reading. Pre-reading is performed to read the recorded image information, and the reading condition or the image processing condition is determined based on the recorded image information grasped by the pre-reading, that is, the pre-reading image signal obtained by the pre-reading.

The excitation light used in the pre-reading here is at a lower level than the excitation light used in the main reading means that the effective energy of the excitation light that the stimulable phosphor sheet receives per unit area during the pre-reading is in the main reading. Means smaller than that of.

Further, when determining only the image processing condition based on the recorded image information, it is sufficient that the recorded image information is known before the image processing. In this case, the main reading image signal, which is the recorded image information itself, is already obtained. Therefore, the image processing condition may be determined based on the main reading image signal, and it is not always necessary to perform the prefetching as described above.

(Problems to be Solved by the Invention) However, when the reading condition and / or the image processing condition of the radiation image information is determined as described above, when the same subject is photographed in different photographing positions, the respective reproductions are performed. The density of the region of interest in the subject may change in the image. Hereinafter, this will be described in detail. For example, consider a case where the chest is photographed from the front as shown in FIG. 2A and a case where the chest is photographed from the side as shown in FIG. 2B in order to diagnose the thoracic spine. In frontal imaging, the thoracic vertebra K, which is the region of interest, overlaps the mediastinum where it is difficult for radiation to pass through, so the accumulated radiation dose in the thoracic vertebra part of the stimulable phosphor sheet is low, and this part is the low luminescence amount part. (See the histogram of the read image signal shown in Figure 3A). On the other hand, in lateral imaging, the thoracic vertebra K overlaps the lung field where radiation easily penetrates, so the accumulated radiation dose in the thoracic vertebra part is high in the stimulable phosphor sheet, and this part is the high luminescence amount part (the histogram in Fig. 3B). reference). The maximum value Smax and the minimum value Smin of the read image signal from the stimulable phosphor sheet do not change much in the case of both frontal shooting and side shooting, so the conventional determination method based on the recorded image information is used. Of 1
The read condition and / or the image processing condition determined by the method based on the maximum value Smax and the minimum value Smin of the read image signal are substantially the same in both cases. Therefore, when an image is read under such a reading condition and / or an image processing condition to obtain a reproduced image, the thoracic vertebra part has a relatively low density in the front image, while it has a relatively low density in the lateral image. It becomes a high concentration.

Such development is not limited to the above-mentioned parts and photographing positions,
A portion having particularly high or low radiation absorptivity generally occurs when a region of interest overlaps or does not overlap with a region of interest due to a difference in imaging body position.

As described above, when the region of interest varies depending on the imaging position of the subject, it becomes difficult to make a diagnosis using a radiation image.

Such a problem may also occur when a reproduced image is obtained by reading the image information from a recording medium other than the stimulable phosphor sheet on which the radiation image information is recorded.

Therefore, the present invention reads the radiation image information from the recording medium such as different stimulable phosphor sheets in which the subject is recorded while changing the photographing position, and reproduces the radiation image to read the density of the region of interest in the reproduced image. It is an object of the present invention to provide a radiation image information reading method capable of uniformly aligning with each other irrespective of the imaging position.

(Means for Solving Problems) In the radiation image information reading method of the present invention, as described above, the recording medium is mainly read, and the reading conditions and / or the reading are performed when the main reading is performed. Image processing conditions when image processing the main reading image signal,
In a radiation image information reading method, which is determined based on an image signal for condition determination obtained by reading image information recorded on the recording medium, the image signal plays a role from the image signal for condition determination. It is characterized in that whether or not the image has line symmetry is discriminated, and the reading condition and / or the image processing condition is determined according to the discrimination result.

The "recording medium" in the above means a medium on which radiation image information can be recorded, and the above-mentioned stimulable phosphor sheet can be mentioned as a specific example, but it is not necessarily limited thereto.

Further, the “main reading” in the above means reading an image signal for reproducing a visible image from a recording medium, and is also used in this sense in the case of a recording medium other than the stimulable phosphor sheet.

Further, the "reading condition" in the above means the relationship between the input and the output in the reading means, for example, when the recording medium is a stimulable phosphor sheet, the input (stimulated luminescence) and the output (image signal level) in the photoelectric reading means. ) Is a general term for various conditions that affect the relationship with the above, and means, for example, a read gain (sensitivity), a recording scale factor (latitude), or the like.

Further, the "image processing condition" in the above is a general term for various conditions that affect the relationship between the input and the output in the image processing means, and means, for example, the gradation processing condition and the spatial frequency processing condition.

Further, the “image signal for condition determination” in the above is an image signal used as a material when determining the reading condition and / or the image processing condition, and is obtained by reading the image information recorded on the recording medium. The obtained image signal is meant and, for example, the above-mentioned pre-reading image signal or main-reading image signal can be used as this condition determining image signal, but the image signal is not necessarily limited thereto. Note that when the preread image signal is used as the condition determining image signal, the reading condition and / or the image processing condition can be determined based on it, but when the main reading image signal is used, only the image processing condition can be determined.

The term “determined in accordance with the determination result” means that the determination is made only in accordance with the determination result, and in addition to that, it is determined in accordance with other factors such as the above-described imaging region, imaging method, or appropriate characteristic value of recorded image information. It is meant to include the case of making a decision.

Further, the "determination of the reading condition and / or the image processing condition" may be determined by any method depending on the determination result, that is, as long as the determination result is used. No specific method is specified.

(Operation) Images that include a specific region of interest and have different image-capturing positions usually have unique patterns. That is, referring to the example of FIGS. 2A and 2B, in the front view image of FIG. 2A, the thoracic vertebra K extends in the vertical direction at the center portion in the left-right direction of the image, and the image is substantially line-symmetric with respect to the center line of the thoracic vertebra K. Has become. On the other hand, in the side view image of FIG. 2B, the above-mentioned line symmetry is not recognized. Therefore, in such an image, it is possible to indirectly determine whether the imaging body position is the front or the side by determining the presence or absence of the line symmetry. Therefore, in the above example, the reading condition and / or the image processing condition are set so that the density of the reproduced image is increased when the line symmetry is recognized and the density of the reproduced image is decreased when the line symmetry is not recognized. If set, it is possible to make the densities of the thoracic spine portion, which is the region of interest, equal in the front and side images.

(Effect of the invention) Therefore, as described above, it is determined whether or not the image carried by this image signal has line symmetry from the image signal for condition determination, and the reading condition and / or Alternatively, according to the present invention for determining the image processing condition, it is possible to make the densities of the regions of interest in the reproduced image constant with each other regardless of the photographing position.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a radiation image information recording / reproducing system adopting an embodiment of the radiation image information reading method according to the present invention. This radiation image information recording / reproducing system basically includes a radiation image capturing unit 20, a read-ahead reading unit 30,
The reading unit 40 for main reading and the image reproducing unit 50 are included. In the radiation image capturing unit 20, radiation 102 is emitted from a radiation source 100 such as an X-ray tube toward a subject (examinee) 101. Radiation transmitted through this subject 101
As described above, the stimulable phosphor sheet 103 that accumulates the radiation energy is arranged at the position where the 102 is irradiated, and the transmitted radiation image information of the subject 101 is stored and recorded in the stimulable phosphor sheet 103. .

The stimulable phosphor sheet 103 on which the radiation image information of the subject 101 is recorded in this manner is sent to the prereading reading unit 30 by the sheet transfer means 110 such as a transfer roller. The laser light 202 emitted from the laser light source 201 for pre-reading in the pre-reading reading section 30 passes through the filter 203 that cuts the wavelength region of the stimulated emission light emitted from the stimulable phosphor sheet 103 by the excitation of this laser light 202. After that, it is linearly deflected by an optical 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 the excitation light does not overlap with the wavelength range of the stimulated emission light emitted by the stimulable phosphor sheet 103. On the other hand, the stimulable phosphor sheet 103 is transferred in the direction of arrow 206 by the sheet transfer means 210 such as a transfer roller to be sub-scanned, and as a result, the entire surface of the stimulable phosphor sheet 103 is irradiated with the laser beam 202. . Here, the emission intensity of the laser light source 201, the beam diameter of the laser light 202, the laser light
The scanning speed of 202, the transfer speed of the stimulable phosphor sheet 103,
The energy of the pre-reading excitation light (laser light 202) is selected to be smaller than that of the main reading performed by the main reading reading unit 40 described later.

When the laser light 202 is irradiated as described above, the stimulable phosphor sheet 103 emits stimulated emission light of a light amount corresponding to the radiation energy stored and recorded in the stimulable phosphor sheet 103. Incident on. The stimulated emission light is guided through the light guide 207, emitted from the emission surface, and received by a photodetector 208 such as a photomultiplier.
On the light receiving surface of the photodetector 208, a filter that transmits only light in the wavelength range of stimulated emission light and cuts light in the wavelength range of excitation light is attached, and detects only stimulated emission light. Is ready to go. The detected stimulated emission light is converted into an electric signal which carries the image information stored and recorded, and is amplified by the amplifier 209.
Is amplified by. The signal output from the amplifier 209 is A / D
The pre-read image signal Sp is digitized by the converter 211.
Is input to the main reading control circuit 314 of the main reading reading unit 40. The main reading control circuit 314 uses, for example, a histogram analysis or the like based on the preread image signal Sp to set a gradation processing condition set value which is one of a read gain set value a, a recording scale factor set value b, and an image processing condition set value. Determine c.

The stimulable phosphor sheet that has been read ahead as described above
103 is transferred to the reading unit 40 for main reading. Book reader 4
The laser light 302 emitted from the main reading laser light source 301 at 0 passes through the filter 303 that cuts the wavelength region of the stimulated emission light emitted from the stimulable phosphor sheet 103 by the excitation of the laser light 302, and then the beam The beam diameter is strictly adjusted by the expander 304, is linearly deflected by the optical deflector 305 such as a galvanometer mirror, and the stimulable phosphor sheet 1 is passed through the plane reflecting mirror 306.
03 incident on. An fθ lens 307 is arranged between the light deflector 305 and the plane reflecting mirror 306 so that the beam diameter of the laser light 302 scanning the stimulable phosphor sheet 103 becomes uniform. On the other hand, the stimulable phosphor sheet 103 is transferred in the direction of arrow 308 by the sheet transfer means 320 such as a transfer roller to be sub-scanned, and as a result, the stimulable phosphor sheet 10 is transferred.
The entire surface of 3 is irradiated with laser light. When the laser light 302 is thus irradiated, the stimulable phosphor sheet 103 emits stimulated emission light in an amount corresponding to the radiation energy stored and recorded therein, and this emission light is incident on the main reading light guide 309. To do. The stimulated emission light guided by repeating the total reflection in the main reading light guide 309 is emitted from the emission surface and is received by the photodetector 310 such as a photomultiplier. A filter that selectively transmits only the wavelength region of the stimulated emission light is attached to the light receiving surface of the photodetector 310,
The photodetector 310 is adapted to detect only stimulated emission light.

The output of the photodetector 310 that photoelectrically detects stimulated emission light indicating the radiation image recorded on the stimulable phosphor sheet 103 is the read gain based on the read gain set value a determined by the control circuit 314. Is amplified to an appropriate level electric signal by the amplifier 311 in which is set. The amplified electric signal is input to the A / D converter 312, converted into a digital signal with a recording scale factor suitable for the signal fluctuation width based on the recording scale factor setting value b, and the signal processing circuit 31.
Entered in 3. In the signal processing circuit 313, the digital signal, that is, the main reading image signal is subjected to gradation processing (signal processing) based on the gradation processing condition setting value c so as to obtain a radiographic image excellent in observation and interpretation, and output. To be done.

The read image signal (main read image signal) So output from the signal processing circuit 313 is input to the optical modulator 401 of the image reproducing unit 50. In the image reproducing section 50, the recording laser light source
The laser light 403 from 402 is modulated by the optical modulator 401 based on the main reading image signal So input from the signal processing circuit 313, deflected by the scanning mirror 404, and scanned on the photosensitive material 405 such as photographic film. . And photosensitive material 4
Reference numeral 05 is transferred in a direction (arrow 406 direction) orthogonal to the scanning direction in synchronization with the scanning, and a radiation image based on the main reading image signal So is output onto the photosensitive material 405. As a method for reproducing the radiation image, various methods such as the above-described CRT display can be adopted in addition to such a method.

Next, a characteristic part of the method of the present invention that allows the densities of the regions of interest to be made uniform in the reproduced image even if the photographing position of the subject 101 changes will be described. The pre-reading image signal Sp output from the A / D converter 211 is input to the main reading control circuit 314 as described above, and also the density correction control circuit 5
Entered in 00. FIG. 4 shows the structure of the density correction control circuit 500 in detail, which will be described below with reference to FIG. The signal extraction unit 501 of the density correction control circuit 500 is
From the input pre-read image signal Sp, the stimulable phosphor sheet
Only the image signal relating to the pixel column L along the predetermined direction on 103 is extracted. The pixel row L is as shown in FIGS. 2A and 2B. For example, in the case of the radiation image of the thoracic vertebra K as described above, the pixel row setting unit 502 causes the stimulable phosphor sheet 103 to move over the stimulable phosphor sheet 103. It is supposed to extend in the left-right direction.
Hereinafter, a case corresponding to the image of the thoracic vertebra K will be described as an example. The extracted prefetch image signal Sp ′ relating to only the pixel column L is sent to the calculation unit 504. The calculation unit 504 obtains the difference between the signals of the pre-read image signals Sp ′ which are associated with the pixels at the same distance in the opposite direction from the central position Xo of the pixel row L, and obtains the cumulative value of the absolute values of these differences. .
That is, the calculation unit 504 represents the position of each pixel as x with reference to the central position Xo of the pixel row L as shown in FIG. 5A or FIG. 5B (plus in one direction, minus in the other direction),
The image signal for the pixel at each position x is f (x), and the pixel column L
Let N be the number of pixels in Find the value of. Here, xi represents the i-th pixel position in the plus direction from the reference point x _o , and −xi similarly represents the i-th pixel position in the minus direction. This cumulative value Q is calculated by the comparison unit 50.
5, the comparison unit 505 compares the reference value R input from the reference value setting unit 506 with the cumulative value Q, and when the cumulative value Q exceeds the reference value R, the correction signal T is read. Send to the correction circuit 507. Upon receiving the correction signal T, the correction circuit 507 corrects the read gain setting value a determined by the main read control circuit 314 as described above so as to reduce the read gain. The distribution states of the pre-read image signals Sp '= f (x) extracted in the front image and the side image of the thoracic spine K are as shown in FIGS. 5A and 5B, respectively. That is, as described above, since the front photographed image has line symmetry, the distribution of the image signal f (x) in the front photographed image naturally also has line symmetry. It is not allowed. Therefore, the cumulative value Q takes a very small value in the front side imaged image and a considerably large value in the side face imaged image. As described above, if the image reading condition and the image processing condition are constant, the density of the portion of the thoracic vertebra K in the reproduced image of the lateral photographing becomes higher than that in the front photographing. Therefore, when the cumulative value Q is relatively large as described above, that is, when the reading gain is lowered when reading the side face image, the main reading image signal So becomes a low level as a whole, and the reproduction radiation reproduced on the photosensitive material 405. Image density is low overall. As a result, the density of the portion of the thoracic spine K in the reproduced image of the side surface of the thoracic vertebra becomes equal to the density of the thoracic vertebra in the reproduced image of frontal photography. The proper correction amount of the reading gain can be obtained based on experiments or experience.

In the above-described embodiment, the front view image is read with the read gain determined by the main reading control circuit 314 as it is, and the read gain is corrected to a low value when reading the side view image. The captured image may be read with the read gain determined by the main reading control circuit 314 as it is, and the read gain may be corrected to be high when the front captured image is read. In the above embodiment,
Although the reading gain determined by the main reading control circuit 314 is corrected, the reading gain setting value a determined by the main reading control circuit 314 may be increased or decreased according to the cumulative value Q. . In order to adjust the density of the reproduced image, the reading gain is changed as described above, the condition of the recording scale factor in the A / D converter 312 is changed, and the condition of the gradation processing in the signal processing circuit 313 is changed. You may do the same. Further, these density adjusting methods may be used together.

The gradation processing condition is usually represented by a non-linear gradation curve. For example, when the gradation processing condition determined by the main reading control circuit 314 is corrected by the correction signal T, the gradation curve is corrected by the correction signal. Depending on T, it may be shifted up and down, left and right, or may be rotated around a predetermined position on the gradation curve so as to correct the densities of the regions of interest in the reproduced image.

In the signal extraction unit 501, the stimulable phosphor sheet 103
It is not necessary to extract the pre-reading image signal Sp for all the pixels along the above predetermined line, and the pre-reading image signal Sp may be extracted for an appropriate number of pixels in a scattered manner.

In the embodiment described above, it is determined whether or not the read image has line symmetry depending on the magnitude of the cumulative value Q. However, the presence or absence of the line symmetry is determined by other methods. It is also possible to determine. Another embodiment of the present invention will be described below with reference to FIG. 6 in which the presence or absence of line symmetry is determined regardless of the cumulative value Q. This FIG. 6 shows a density correction control circuit 5 used in place of the density correction control circuit 500 shown in FIG.
It shows 00 '. In FIG. 6, elements that are the same as the elements in FIG. 4 are given the same numbers, and descriptions thereof are omitted. In this control circuit 500 ′, the prefetch image signal Sp ′ extracted by the signal extraction unit 501 is sent to the analysis unit 503. The analysis unit 503 approximates the relationship between the prefetched image signals Sp ′ as a function f (x) of the position x of each pixel in the pixel row L, and a secondary expression f (x) = px ² + qx + r Find the formula. Then, the analyzing unit 503 sends the value of −q / 2p to the calculating unit 504 ′ after obtaining the above approximate expression. The calculation unit 504 'calculates the difference Q'between the center position x _o of the pixel row L and the value of -q / 2p. The value of this difference Q ′ is input to the comparison unit 505. The comparing section 505 compares the reference value R'input from the reference value setting section 506 with the Q'value, and when the Q'value exceeds the reference value R ', the correction signal T is read to correct the gain. Send to circuit 507. Upon receiving the correction signal T, the correction circuit 507 corrects the read gain setting value a determined by the main read control circuit 314 so as to reduce the read gain.

The value of −q / 2p indicates the pixel position where the above-described quadratic expression has the maximum value or the minimum value. The quadratic curve shown by this quadratic equation is as shown in FIG. 7A and FIG. 7B in the case of a front image of the thoracic vertebra and a side image of the thoracic spine, respectively. That is, since the front photographed image has the above-mentioned line symmetry, in this case, the pixel position −q / 2p at which the quadratic expression has the minimum value is extremely close to the center position x _o of the pixel row L (see FIG. 7A). ). On the other hand, in the side view image, the pixel position −q / 2p at which the quadratic expression has the maximum value is far from the center position x _o of the pixel row L. Therefore, the above-mentioned difference Q'exceeds the reference value R'when reading a side-view image. At this time, by lowering the reading gain as described above, the density of the reproduced image is entirely reduced, and The density of the part is lowered and becomes equal to the density of the thoracic vertebra part in the front reproduced image.

As described above, in the front and side images of the thoracic spine,
The case of aligning the densities of the thoracic spine, which is the region of interest, has been described as an example, but the method of the present invention is a stimulable phosphor sheet in which other regions such as the lumbar spine are recorded, and other different imaging positions such as front and oblique positions. The same can be applied to the case where the radiation image information is read from the stimulable phosphor sheet on which the subject has been recorded. That is, in the case where the images of one of the different postures have line symmetry and the images of the other posture do not have line symmetry among the images of the different photographing positions, the presence or absence of the above-mentioned line symmetry is determined by the method described above. Can be determined, and the density of the reproduced image can be appropriately increased or decreased according to the determination result.

The position of the pixel row L and the reference values R and R'can be manually set according to the photographing region of the image to be read and the photographing position, or these information are input to the reading device as a photographing menu. In this case, the pixel column setting unit 502 and the reference value setting unit 506 described above can automatically set the values based on this input information.

The apparatus shown in FIG. 1 has a reading system for main reading and a reading system for pre-reading separately.
As shown in No. 67242, the reading system for main reading is also used as the reading system for pre-reading.When the pre-reading is completed, the sheet transporting means returns the stimulable phosphor sheet to the reading system to perform the main reading, and the excitation light is read during the pre-reading. The excitation light energy may be adjusted to be smaller than that during the main reading by the energy adjusting means, and the method of the present invention can be applied even when the radiation image information is read by such an apparatus.

In addition, in the above-mentioned embodiment, one stimulable phosphor sheet has one
Although the case where one image exists is dealt with, for example, in the case of divided photographing in which one sheet is divided into two or more sections and the image is photographed for each section, the present invention can be applied to each section. good.

In the radiation image information recording / reproducing system, the image signal for condition determination is obtained by pre-reading, and the reading condition and the image processing condition are determined based on the determination result of the presence or absence of the line symmetry obtained from this signal. In a system that does not perform prefetching, the main reading image signal may be used as the image signal for condition determination. In this case, the main reading image signal is temporarily stored in an appropriate storage means, and on the other hand, the image processing condition is determined based on the result of determination of the presence or absence of line symmetry obtained by the same method as the above-mentioned case based on the main reading image signal. After that, the main reading image signal may be read from the storage unit, and the main reading image signal may be subjected to image processing according to the image processing conditions.

As described in detail above, according to the radiographic image information reading method of the present invention, the densities of the regions of interest in the reproduced image can be made uniform even if the imaging position of the subject is different, and the diagnostic performance of the radiographic image is greatly increased. It is possible to raise it.

The present invention can be modified in various ways within the range of the paper and is not limited to the above-mentioned embodiments.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a radiation image information recording / reproducing system for reading radiation image information according to an embodiment of the present invention, and FIGS. 2A and 2B are examples of radiation images in which the subject has different imaging positions. 3A and 3B are graphs showing an example of a histogram of a read image signal from a stimulable phosphor sheet which is photographed by changing a photographing position of a subject, and FIG. 4 is a graph of FIG. A block diagram showing a part of the apparatus in detail, FIGS. 5A and 5B are graphs showing an example of distribution of an extracted image signal according to the present invention, and FIG. 6 is another diagram of a density correction control circuit for carrying out the method of the present invention. A block diagram showing an example, FIGS. 7A and 7B are graphs showing the relationship between the image signal distribution and the approximate expression according to the present invention. 20: Radiation image capturing unit, 30: Pre-reading reading unit 40: Main reading reading unit, 100: Radiation source 101: Subject, 102: Radiation 103: Accumulative phosphor sheet 201: Pre-reading Laser light source 202 …… Pre-reading laser light 204 …… Pre-reading light deflector 208 …… Pre-reading light detector 210 …… Pre-reading sheet transfer means 301 …… Main reading laser light source 302 …… Main reading laser light 305 …… Main reading light deflector 310 …… Main reading light detector, 311 …… Amplifier 312 …… A / D converter, 313 …… Signal processing circuit 314 …… Control circuit 320 …… Main reading sheet transfer means 500, 500 ′ …… Density correction control circuit 507 …… Read gain correction circuit a …… Read gain set value b …… Recording scale factor set value c …… Image processing condition set value, L …… Pixel row R …… Reference value, Sp… … Pre-reading image signal Sp ′ …… Extracted pre-reading image signal So …… Main reading image Signal, T ...... correction signal

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Claims (3)

[Claims] 1. A main reading for reading an image signal for reproducing a visible image from a recording medium on which radiation image information is recorded, and reading conditions for the main reading and / or a main reading image read by the main reading. In the radiation image information reading method, the image processing condition for image-processing the signal is determined based on the image signal for condition determination obtained by reading the image information recorded on the recording medium, From the image signal for determination, it is determined whether or not the image carried by the image signal has line symmetry, and the reading condition and / or the image processing condition is determined according to the determination result. Radiation image information reading method. 2. A signal relating to a pixel row along a predetermined direction on the recording medium is extracted from the image signal for condition determination, and these extracted signals are opposite to each other from the central position of the pixel row. The difference between the signals of pixels at the same distance in the direction is calculated, and it is determined that the line symmetry exists when the cumulative value of the absolute values of these differences is less than or equal to a predetermined value, and the line symmetry does not exist when the accumulated value exceeds a predetermined value. The radiation image information reading method according to claim 1, wherein 3. A signal relating to a pixel row along a predetermined direction on the recording medium is extracted from the image signal for condition determination, and a position x of each pixel of the pixel row and the pixel relating to the position x are extracted. The relationship between the extracted signal value f (x) is approximated to a quadratic expression f (x) = px ² + qx + r, and the difference between the value −q / 2p and the central position x _o of the pixel row is The radiographic image information reading method according to claim 1, wherein it is determined that the line symmetry is present when the value is a predetermined value or less, and the line symmetry is not present when the value exceeds the predetermined value.