JPH02267679A - Method for recognizing division pattern of radiation image - Google Patents

Abstract

PURPOSE:To accurately recognize a division pattern by deciding an apex changed in upward or downward projection appearing on the profile of image data on each line segment in a direction to traverse a boundary as a boundary candidate point, and setting the line segment along the point as the boundary. CONSTITUTION:When a recording sheet is divided into plural parts and radiographing is performed at every divided part, the profile of image data on each line segment is found for each of a large number of line segments in the direction to traverse the boundary based on the image data in the neighborhood of an area where the boundary of each part exists. And the apex changed in the upward or downward projection appearing on each line segment on the profile is decided as the boundary candidate point, and furthermore, it is discriminated whether or not density at those boundary candidate points are different from another, and when the density at those boundary candidate points are remarkably higher or lower than another, a straight line is decided as the boundary. In such a way, the division pattern of the recording sheet can be accurately recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for recognizing a division pattern of a radiation image recorded on a recording sheet such as a stimulable phosphor sheet or an X-ray film.

(Prior Art) It is practiced in various fields to read a recorded radiation image to obtain image data, perform appropriate image processing on this image data, and then reproduce and record the image. For example, an X-ray image is recorded using an X-ray film with a low gamma value designed to be compatible with later image processing, and the X-ray image is read from the film on which it is recorded and converted into an electrical signal. By performing image processing on this electrical signal (image data) and then reproducing it as a visible image in a copy photograph, etc., it is possible to obtain a reproduced image with good image quality performance such as contrast, sharpness, and graininess. A system has been developed (see Japanese Patent Publication No. 81-5193).

In addition, the applicant has proposed radiation (X-rays, α-rays).

When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when irradiated with excitation light such as visible light, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. A radiation image of a subject such as a human body is photographed and recorded on a sheet of stimulable phosphor using a stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. The resulting stimulated luminescent light is read photoelectrically to obtain image data, and based on this image data, a radiation image of the subject can be recorded on a recording material such as a photographic light-sensitive material, a CRT, etc. Radiation image recording and reproducing systems that output visual images have already been proposed (Japanese Patent Application Laid-open Nos. 55-12429, 58-11395, 55-
No. 163472, No. 5B-104845, No. 55-1
No. 16340, etc.).

This system has the practical advantage of being able to record images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiation image into an electric signal and using this electric signal to output the 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, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. be able to.

In the above system, the stimulable phosphor sheet is scanned in advance with a low-level light beam before obtaining image data by reading it under optimal reading conditions depending on the dose of radiation irradiated on the stimulable phosphor sheet. Pre-reading is performed to read the outline of the radiation image recorded on this sheet, the pre-read image data obtained by this pre-reading is analyzed, and then the above sheet is irradiated with a light beam of a higher level than the light beam used during the above-mentioned pre-reading. There is also a system configured to perform main reading to obtain image data by scanning the radiation image and reading it under the optimum reading conditions for this radiation image (Japanese Patent Laid-Open No. 58-67240).
No. 5g-87241, No. 58-87242, etc.)
.

Here, reading conditions are a general term for various conditions that affect the relationship between the amount of stimulated luminescence light and the output of the reading device during reading, such as reading gain, scale factor, or , the power of excitation light during reading, etc.

Also, the high level and low level of the light beam are, respectively.
If the intensity of the light beam irradiated per unit area of the sheet or the intensity of stimulated luminescence light emitted from the sheet depends on the wavelength of the light beam (has a wavelength sensitivity distribution), It refers to the magnitude of the weighted intensity after weighting the intensity of the light beam irradiated per unit area of the sheet with the wavelength sensitivity.As a method of changing the level of the light beam, light beams of different wavelengths are used. methods to use, methods to change the intensity of the light beam itself emitted from a laser light source, methods to change the intensity of the light beam by inserting or removing an ND filter, etc. on the optical path of the light beam, methods to change the beam diameter of the light beam. How to change the scanning density,
Various known methods can be used, such as a method of changing the scanning speed.

In addition, regardless of whether the system performs this prefetching or the system that does not, the obtained image data (including prefetched image data) is analyzed to determine the optimal image processing conditions when performing image processing on the image data. Some systems let you decide. The method for determining the optimal image processing conditions based on this image data is not limited to systems using stimulable phosphor sheets, but for example, image data is obtained from a radiation image recorded on a recording sheet such as a conventional X-ray film. It is also applied to the system.

In addition, when recording radiation images on a recording sheet, it is important to avoid irradiating radiation to parts of the subject that are not necessary for observation, or to prevent radiation from being irradiated to parts that are unnecessary for observation. Scattered rays may enter some areas, reducing image quality. Therefore, use an irradiation field diaphragm to limit the radiation irradiation area so that only the necessary parts of the subject and part of the recording sheet are irradiated with radiation. Often. When analyzing image data to determine reading condition 1 image processing conditions as described above, if the image data used for analysis is image data obtained from a recording sheet photographed using an irradiation field aperture, this Even if the image data is analyzed while ignoring the existence of the irradiation field, the radiographic image taken and recorded will not be understood correctly, and incorrect reading conditions and image processing conditions will be required, resulting in the inability to reproduce and record a radiographic image that is suitable for observation. occurs. In order to solve this problem, before determining the reading condition 9 image processing conditions, it is necessary to recognize the irradiation field and determine the reading condition 1 image processing conditions based on the image data within the irradiation field.

(Question 8 to be solved by the invention) By the way, in each of the above-mentioned systems, different radiation images are taken one by one in a plurality of divided regions on - recording sheets (stimulable phosphor sheets, X-ray films, etc.). May be recorded. According to this divisional shooting, for example, when shooting a subject that is small compared to the area of the recording sheet, it is possible to record the shooting of multiple subjects on one recording sheet, which is economical. When reading a recording sheet to obtain image data, multiple images can be read at once, and the reading processing speed is also improved.

However, in a radiation image, there are the subject area where the subject was recorded, the direct radiation area where radiation is irradiated directly onto the recording sheet without going through the subject, and the scattering area outside the irradiation area when using an irradiation field aperture. Since there are scattered radiation areas where only radiation is recorded, when determining the reading conditions and image processing conditions mentioned above, it is necessary to consider the area corresponding to the object area that ultimately needs to be reproduced as a visible image with excellent observation characteristics. Even though it is necessary to extract only image data, these conditions are determined based on the premise that the only radiation image is recorded on the recording sheet without recognizing the division pattern of the recording sheet. Subject part.

There may be cases where the direct radiation part, the scattered radiation part, etc. cannot be separated well, and the image data corresponding to the subject part cannot be successfully extracted.

In order to avoid this, it is possible to record the division pattern at the time of shooting and manually input the division pattern into the device, for example, before obtaining image data from the recording sheet, but this method is time-consuming. This is very cumbersome and can lead to input errors.

In view of the above circumstances, the present invention provides more appropriate reading conditions and/or
Another object of the present invention is to provide a method of automatically recognizing a division pattern of a recording sheet so that image processing conditions can be determined.

(Means for Solving the Problems) The radiation image division pattern recognition method of the present invention is based on a recording sheet (stimulable phosphor sheet,
When the recording sheet is divided into a plurality of parts and imaging is performed for each divided part, among a large number of image data representing the radiographic image obtained from a radiographic film, etc. Based on the image data near the area where the boundary exists, for each of a number of line segments in the direction that crosses the boundary, the profile of the image data on each line segment is determined, and the upward or downward convexity that appears on the profile is calculated. The changed vertices are defined as boundary candidate points, and if the profile is upwardly convex, whether or not the value of image data at these boundary candidate points is greater than or equal to a first predetermined value;
If it is convex downward, it is determined whether or not it is less than or equal to a second predetermined value that is smaller than the first predetermined value, and the value of the image data at these boundary candidate points is greater than or equal to the first predetermined value or the second predetermined value. By defining the straight line as the boundary when the value is less than or equal to the value,
The present invention is characterized in that the division pattern of the recording sheet is recognized.

(Function) When recording a radiographic image on only a part of the recording sheet, the part outside of the recording sheet records another radiographic image or is already recorded, so there is no unnecessary information there. Radiation must be avoided. So, for example ′! As shown in figure a3, the radiation vAl of the recording sheet
Photographing is performed after placing a shield 6 that does not transmit radiation in the area other than the area where the i-image is recorded. When imaging is performed with shielding objects placed in this way, there are errors in the placement of the shielding objects, so for example, as shown in FIG. It usually happens that the areas overlap (double exposure area - area C), or that the plurality of radiographic images are somewhat separated (partition line - area D), as shown in FIG. 4B, for example. In addition, since the density of the image in these areas is greatly different from that of other image parts, in the case of area C, which is the 2ii exposure area, the profile of the image data on the line segment in the direction across the boundary is as shown in Figure 5A. In the case of a region that is a dividing line, the profile changes to a downward convex shape as shown in FIG. 5B. In addition, the image data values (corresponding to the density) at the vertices of these upwardly or downwardly convex profiles are greater than the image data values in the normal image area (area irradiated with radiation that has passed through the subject). Since the image data values at these vertices are significantly larger or smaller, the values of the image data at these vertices are the maximum value (Ssax) or the minimum value (S■) in the histogram of the entire image data as shown in FIG.
in ), the histogram width (Ssax −5sln
) inner value Thl, T
It has a value larger or smaller than h2.

The present invention has been made with this in mind, and for each of a large number of line segments in the direction that crosses the boundary, a profile of image data on each line segment is obtained, and the image data above or below that appears on the profile is calculated. The convex vertices are determined as boundary candidate points, and line segments along these boundary candidate points are determined as boundaries between a plurality of radiographic images, thereby recognizing the division pattern of the recording sheet. Furthermore, there is a possibility that a portion of the profile that is convex upward or downward exists other than the boundary. Therefore, in the present invention, it is determined whether the large number of boundary candidate points obtained as described above is larger than the predetermined value Thl or smaller than Th2, and Th
, the straight line is defined as the boundary when it is less than Th2.

As described above, the division patterns can be accurately recognized, image data corresponding to the subject portion can be extracted for each division pattern, and more appropriate reading conditions and image processing conditions can be determined.

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

FIG. 3 is a perspective view schematically showing an example of a radiation imaging apparatus constituting a system using the division pattern recognition method of the present invention. This system uses the aforementioned stimulable phosphor sheet as a recording sheet for photographing and recording radiation images.

Radiation 2 emitted from a radiation source 1 passes through a subject 3 and is irradiated onto a stimulable phosphor sheet 11 .

A region 5 (direct radiation area) is formed around the sheet 11 where the radiation that has passed through the subject 3 is irradiated, where the radiation is directly irradiated onto the sheet 11 without passing through the subject 3. Approximately half of the sheet 11 is used for each imaging session, and the other half is covered with a radiation shield 6 to prevent radiation from being irradiated. By performing such imaging on the left and right sides of the sheet 11, two radiation images are formed on one sheet 11.

FIGS. 4A and 4B are diagrams showing a state in which two radiation images A and B are formed on the left and right sides of one sheet 11 as described above. Each image A, B includes a subject part 3A, 3B in which a radiation image of the subject 3 is recorded, a direct radiation part 5A in which the sheet 11 is directly irradiated with radiation,
5B is formed.

The sheet 11 in FIGS. 4A and 4B has an overlapping area C where parts of the two images A and B overlap, and which of the two images A and B, respectively, depending on the placement position of the shielding object 6 at the time of photographing. There are unexposed areas where only scattered radiation is recorded, where no radiation is recorded. Theoretically, it is possible to form two images A and B so that they are exactly in contact with each other in a straight line, but in reality, this is extremely rare.
In rare cases, even when they are formed so that they are in contact with a straight line, the result is often the same as when two images A and B partially overlap due to the influence of scattered radiation.

Therefore, it can be considered that the overlapping region C or the unexposed region exists with a sufficiently high probability for practical purposes.

FIG. 7 is a perspective view showing an embodiment of a radiation image reading device using an example of the divided pattern recognition method of the present invention. This device uses the photographic device shown in FIG. 3 to photograph and record the stimulable phosphor sheet 11, for example,
This is a device that reads a radiation image as shown in Figure B, and is also a device that performs the above-mentioned pre-reading.

The stimulable phosphor sheet 11 on which the radiation image has been recorded is first placed at a predetermined position by a pre-reading means 100 which performs pre-reading by scanning with a weak light beam and emitting only a part of the radiation energy stored in the sheet 11. Set. The stimulable phosphor sheet 11 set at a predetermined position is conveyed (sub-scanned) in the direction of arrow Y by a sheet conveying means 13 such as an endless belt driven by a motor 12.

On the other hand, a weak light beam 1 emitted from a laser light source 14
5 is reflected and deflected by a rotating polygon mirror 16 that is driven by a motor 23 and rotates at high speed in the direction of the arrow, and after passing through a focusing lens 17 such as an fθ lens, the optical path is changed by a mirror 18 and enters the sheet 11 for sub-scanning. Main scanning is performed in the direction of arrow X, which is substantially perpendicular to the direction (direction of arrow Y). From the part of the sheet 11 irradiated with this light beam 15, stimulated luminescence light 19 of a light amount corresponding to the radiographic image information stored and recorded is emitted.
is emitted, and this stimulated luminescence light 19 is guided by a light guide 20 to a photomultiplier (photomultiplier tube) 2
1 is photoelectrically detected. The light guide 20 is made by molding a light guide material such as an acrylic plate, and the linear entrance end surface 20a is formed by a stimulable phosphor sheet l.
The light-receiving surface of the photomultiplier 21 is coupled to an annular output end surface 20b extending along the main scanning line on the photomultiplier 21. The stimulated luminescent light 19 that has entered the light guide 20 from the incident end surface 20a travels through the interior of the light guide 20 through repeated total reflection, and then travels through the light guide 20 through the exit end surface 20a.
0b and is received by the photomultiplier 21, and the amount of stimulated luminescence light 19 representing a radiation image is converted into an electrical signal by the photomultiplier 21.

The analog output signal S output from the photomultiplier 21 is logarithmically amplified by the logarithmic amplifier 2B, and digitized by the A/D converter 27 to obtain pre-read image data Sp. This pre-read image data Sp is data having a value proportional to the logarithm of the amount of stimulated luminescence light.

In the above-mentioned pre-reading, reading conditions such as the voltage value applied to the photomultiplier 21 and the amplification factor of the logarithmic amplifier 2B are determined so that the radiation energy accumulated in the stimulable phosphor sheet 11 can be read over a wide area. It is being

The obtained pre-read image data Sp is inputted into the storage means 28 and stored for a time. Thereafter, the pre-read image data Sp stored in the storage means 28 is read out and inputted to the calculation means 29, and the calculation means 29 first calculates the stimulable phosphor sheet 11 based on the input pre-read image data Sp. The division pattern when the top is divided into multiple regions and imaging is performed for each region is recognized, and then the optimal reading conditions for each divided region are determined, and the average of these reading conditions is determined. By determining the reading conditions, the reading conditions G for reading the book can be determined! ,
For example, the voltage applied to the photomultiplier 21', the amplification factor of the logarithmic amplifier 2B', etc. are determined.

The stimulable phosphor sheet 11' for which pre-reading has been completed is set at a predetermined position in the main reading means 100', and the sheet 11' is scanned by a light beam 15' which is stronger than the light beam used for the above-mentioned pre-reading. Image data is obtained according to the reading condition G1 determined by the main reading means 100.
Since the configuration of ' is different from the configuration of the above-mentioned pre-reading means 100, components corresponding to the respective components of the pre-reading means 100 are indicated by adding a dash to the number used in the pre-reading means 100, Explanation will be omitted.

The image data SQ obtained by being digitized by the A/D converter 27' is sent to the image processing means 50. The image processing means 50 performs appropriate image processing on the image data SQ. The image data subjected to this image processing is sent to the reproduction device 60, and a radiation image based on this image data is reproduced and displayed.

Here, a method for recognizing a division pattern using the calculation means 29 based on the pre-read image data Sp will be explained.

FIG. 1 is a diagram showing an example of a radiation image and an example of the profile of a pre-read image signal Sp obtained by reading this radiation image. This radiographic image is the same radiographic image as in FIG. 4A, and is given the same number as in FIG. 4A.

Two radiation images A and B arranged on the left and right sides of the sheet 11 are formed on this sheet 11, but in the system of this embodiment, the pattern for forming radiation images on the -th sheet 11 is When one image is to be formed on the entire surface of the sheet, it is divided into left and right parts approximately along the line E shown in the figure, so that two independent radiographic images arranged on the left and right as shown in Fig. 1 are photographed and recorded. There are four ways to do this: similarly, the area is divided vertically into two along the line segment F shown in the figure, and the area is divided into four areas divided by the two line segments E and F.

Therefore, the following calculation is performed here regarding the presence or absence of two boundary lines (line segments) E and F, which are the maximum division.

First, from the pre-read image signal Sp corresponding to the entire surface of C) 11,
The pre-read image data Sp near the area where the boundaries E and F exist, that is, the pre-read image data Sp corresponding to the vertically long area H and the horizontally long area ■ shown in FIG. Based on the pre-read image data Sp, for each of a large number of line segments in the direction crossing each boundary line E, F, that is, in the direction parallel to the ξ axis and the η axis, respectively, the pre-read image data Sp on each line segment is calculated. Profile required. FIG. 1 shows profiles J and K of pre-read image data Sp on the ξ-axis and η-axis among these many line segments.

Next, a search is made for the presence of upwardly or downwardly convex portions that appear on these profiles, and if any are present, their vertices are determined as boundary candidate points. The radiation image shown in FIG. 1 is the same image as the image shown in FIG.
(see figure) exists. Therefore, the profile J on the ξ-axis has an upwardly convex portion, and the apex thereof is taken as a boundary candidate point.

The profile K on the η-axis does not have any extremely upward or downward convex portions, and no boundary candidate points are determined.

If any of the profiles on a number of line segments parallel to the η-axis has an upwardly or downwardly convex portion similar to the image boundary, and its apex is determined as a contour candidate point,
These contour candidate points are determined at discrete positions by each line segment, and these candidate points are not lined up substantially on a straight line, and no boundaries are determined.

On the other hand, each profile corresponding to a large number of line segments parallel to the ξ-axis always has an upwardly convex portion, and contour candidate points are determined.

FIG. 2 is a diagram showing a large number of boundary candidate points (marks) found on the radiographic image shown in FIG. 1.

After a large number of boundary candidate points are determined as described above, it is determined whether these boundary candidate points are larger than the first predetermined value Thl. As shown in FIG. 2, a large number of boundary candidate points are lined up on the line segment E, and the line segment E is determined as the boundary of the image. On the other hand, there are fewer boundary candidate points in the direction of line segment F,
Moreover, these boundary candidate points are not lined up in a straight line. Therefore, line segment F is determined not to be a boundary line. Therefore, it is determined that two radiation images separated left and right by the boundary line E are recorded on the sheet l.

When the division pattern is obtained in this way, next, the pre-read image data Sp corresponding to the radiation image in each division area is
, the subject parts 3A and 3B of the image (Fig. 1A, 1B
The pre-read image data Sp corresponding to (see figure) is extracted, and the optimum reading conditions are determined for each divided area based on this.

However, with the device shown in Figure 7, the reading conditions for main reading are 1
Even if multiple images are recorded on one sheet 11, it is not possible to change the reading conditions for each image on one sheet 11, so this device calculates the reading conditions for each divided area as described above. After that, an average reading condition of these reading conditions is determined, and this average reading condition is set as the reading condition Gl for the main reading.

Furthermore, in the above embodiment, an example in which multiple images overlapped (see FIGS. 4A and 5A) was explained, but when multiple images are separated (see FIGS. 4B and 5B), the above embodiment is applicable. Instead of setting the apex of the convex shape on the profile as the boundary candidate point, the apex (bottom point) of the downwardly convex shape is set as the boundary candidate point, and the value of the image data at this point is the first
The boundary can be found in exactly the same way by determining whether or not it is smaller than a second predetermined value Th2, which is smaller than the predetermined value Th1.

Further, in the above embodiment, a case has been described in which the calculation means 29 calculates the reading condition Gl for main reading. 29, based on the pre-read image data Sp, the image processing condition G2 for performing image processing on the image data SQ in the image processing means 50 is determined, and the image obtained by the calculation means 29 is calculated as shown by the broken line in FIG. The processing conditions may be input to the image processing means 50,
Further, the calculation means 29 may calculate both the reading conditions and the image processing conditions.

Furthermore, in the above embodiment shown in FIG.
Although the pre-reading means 100 and the main reading means 100' are configured separately, as described above, the pre-reading means 100 and the main reading means 100' are configured in a parallel manner.
′ may be combined and used for the same purpose.

In this case, after pre-reading, the stimulable phosphor sheet 1
1 back once and scan again to read the book.

When the pre-reading means and the main reading means are used, it is necessary to switch the intensity of the light beam between the pre-reading and the main reading. Various methods can be used, such as a method of switching between the two.

Further, although the above embodiment is an example of a radiation image reading device that performs pre-reading, the present invention can also be applied to a radiation image reading device that performs reading equivalent to the above-mentioned main reading from the beginning without performing pre-reading. . In this case, upon reading, image data is obtained by reading under predetermined reading conditions, and based on this image data, a division pattern of the radiographic image is determined by the calculating means, and further, image processing conditions are determined. The obtained image processing conditions are taken into consideration when image processing is performed on the image data.

Furthermore, the present invention can be used not only for devices using stimulable phosphor sheets but also for devices using conventional X-ray films.

FIG. 8 is a perspective view of an embodiment of an X-ray image reading device that reads an X-ray image recorded on an X-ray film.

An X-ray film 30 on which an X-ray image is recorded, which is set at a predetermined position, is conveyed by a film conveyance means 31 in the direction of arrow Y'' shown in the figure.

Further, the reading light 33 emitted from the light source 32 which is elongated in the -dimensional direction is converged by the cylindrical lens 34, and irradiates the X-ray film linearly in the Y' direction which is substantially perpendicular to the force direction of the arrow Y'. Below the X-ray film 30 irradiated with the reading light 33, the above-mentioned light beam is placed at a position where the reading light 33 transmitted through the X-ray film 30 and whose intensity is modulated by the X-ray image recorded on the X-ray film 30 is received. A MOS sensor 35 is provided in which a large number of solid-state photoelectric conversion elements are linearly arranged in correspondence with each pixel interval in the Y' direction of the X-ray image. In this MOS sensor 35, the X-ray film 30 is connected to the reading light 33.
While being transported in the direction of arrow Y' while being irradiated by
The reading light transmitted through the line film 30 is received at predetermined time intervals corresponding to each pixel interval in the Y' direction of the X-ray image.

FIG. 9 is a circuit diagram showing an equivalent circuit of the MOS sensor 35.

Signals from photocarriers generated when the reading light 33 hits a large number of solid-state photoelectric conversion elements 36 are transferred to capacitors CI (i-1, 2°...) within the solid-state photoelectric conversion elements 36.
・ Accumulated in n). The accumulated photocarrier signals are sequentially read out by sequentially opening and closing the switch section 38 controlled by the shift register 37, thereby obtaining a time-series image signal. This image signal (image data) is then amplified by the amplifier 39 and output from its output terminal 40.

The output analog image data is sampled and converted into digital image data, and then, based on the image data, a division pattern is recognized in the same manner as in the embodiment described above. In this embodiment, instead of the MOS sensor 35, a CCD, CP D (Charge
Needless to say, it is possible to use a device such as PrIIllng Device). Furthermore, in reading the X-ray film, it is of course possible to scan the film two-dimensionally with a light beam in the same way as reading the stimulable phosphor sheet described above. Further, in the above embodiment, the light transmitted through the X-ray film 30 is received, but it is of course possible to be configured so that the light reflected from the X-ray film 30 is received.

As described above, the division pattern recognition method of the present invention can be widely used in so-called divided photographing systems in which a recording sheet is divided into a plurality of parts and photographing is performed for each divided part.

(Effects of the Invention) As explained in detail above, the radiation image division pattern recognition method of the present invention is effective when a recording sheet is divided into a plurality of parts and imaging is performed for each divided part. Based on the image data near the area where the boundary of each part exists, for each of the many line segments in the direction crossing the boundary,
A profile of the image data on each line segment is determined, vertices that appear on the profile that are convex upward or downward are determined as boundary candidate points, and whether the density at these boundary candidate points is significantly different from other points is determined. Since the straight line is determined as the boundary if the density at these boundary candidate points is extremely high or low, the dividing pattern of the recording sheet can be recognized accurately.

By recognizing this division pattern, more accurate reading condition 2 image processing conditions can be determined.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a radiographic image and pre-read image data obtained from this radiographic image, and FIG. 2 is a diagram showing a large number of boundary candidate points (・
Fig. 3 is a perspective view schematically showing an example of a radiation imaging device, and Fig. 4A and Fig. 4B show a state in which two radiation images are formed on the left and right sides of one sheet. Figure 5A, Figure 5
Figure B is a diagram showing an example of a profile of upwardly convex and downwardly convex image data, and Figure 6 is a diagram showing the threshold value Th1.
A diagram showing an example of Th2 on a histogram, FIG. 7 is a perspective view of an embodiment of a radiation image reading device using an example of the divided pattern recognition method of the present invention, and FIG. 8 is a diagram showing images recorded on X-ray film. FIG. 9 is a perspective view of an embodiment of an X-ray image reading device for reading X-ray images taken by M
FIG. 2 is a circuit diagram showing an equivalent circuit of an OS sensor. 1... Radiation source 2... Radiation 3... Subject 3A, 3B... Subject portion 5A, 5B
. . . Direct radiation section 6 . . . Shielding object 11.11' . . . Stormative phosphor sheet 19.19
'...Photostimulated light 21.21 '...Photo multiplier 28.28
'... Logarithmic amplifier 27.27 '... A/D converter 2B... Storage means 29... Arithmetic means 30
...X[film 35...MOS sensor 50
...Image processing means 60...Reproduction device 100.
... Pre-reading means 100'... Main reading means 2nd stage, Figure 5A, Figure 58, Figure 151:'. Figure 9

Claims (1)

[Scope of Claims] Among a large number of image data representing a radiation image obtained from a recording sheet on which a radiation image is recorded, the recording sheet is divided into a plurality of parts and each divided part is photographed. is performed, a profile of image data on each line segment is determined for each of a large number of line segments in a direction that crosses the boundary, based on image data near the area where the boundary of each part exists; Vertices that appear on the profile that have changed to convex upward or downward are defined as boundary candidate points, and if the profile is convex upward, determine whether the values of image data at these boundary candidate points are greater than or equal to a first predetermined value. ,
If it is convex downward, it is determined whether or not it is less than or equal to a second predetermined value that is smaller than the first predetermined value, and the value of the image data at these boundary candidate points is greater than or equal to the first predetermined value or the second predetermined value. By defining the straight line as the boundary when the value is less than or equal to the value,
A radiation image division pattern recognition method comprising recognizing a division pattern of the recording sheet.