JP2631741B2 - Radiation image division pattern recognition method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of 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) Reading a recorded radiation image to obtain image data,
After performing appropriate image processing on the image data, reproduction and recording of the image are performed in various fields. For example, an X-ray image is recorded using an X-ray film having a low gamma value designed to be compatible with later image processing, and this X-ray image is recorded.
The X-ray image is read from the film on which the line image is recorded, converted into an electric signal, the electric signal (image data) is subjected to image processing, and then reproduced as a visible image in a copy photograph or the like, so that the contrast and sharpness are improved. A system capable of obtaining a reproduced image having good image performance such as graininess has been developed (see Japanese Patent Publication No. 61-5193).

In addition, the applicant (X-ray, α-ray, β-ray,
A part of the radiation energy of irradiating with gamma rays, electron beams, ultraviolet rays, etc. is accumulated, and then, when irradiating with excitation light such as visible light, a stimulable phosphor (stimulated luminescence) that emits stimulated emission according to the accumulated energy Using a stimulable phosphor, a radiation image of a subject such as a human body is once photographed and recorded on a sheet-like stimulable phosphor, and the stimulable phosphor sheet is scanned with excitation light such as laser light to shine. Generating stimulated emission light, photoelectrically reading the resulting stimulated emission light to obtain image data, and based on the image data, a radiation image of the subject is converted into a visible image on a recording material such as a photographic photosensitive material or a CRT. A radiation image recording / reproducing system for outputting has already been proposed (Japanese Patent Laid-Open No. 55-1229).
Nos. 56-11395, 55-163472, 56-104645
No. 55-116340, etc.).

This system has the practical advantage of being able to record images over a very large radiation exposure area compared to conventional radiographic systems using silver halide photography. That is, in the case of the stimulable phosphor, it has been recognized that the amount of emitted light that is stimulated by excitation after accumulation is proportional to the radiation exposure amount over an extremely wide range. Even if fluctuates considerably, the amount of the stimulating light emitted from the stimulable phosphor sheet is read by the photoelectric conversion means with the reading gain set to an appropriate value and converted into an electric signal. By outputting a radiation image as a visible image on a display device such as a recording material of a photographic light-sensitive material or a CRT by using the method, it is possible to obtain a radiation image which is not affected by a change in radiation exposure dose.

In the above system, before obtaining image data by reading under optimal reading conditions according to the dose of radiation applied to the stimulable phosphor sheet, scan the stimulable phosphor sheet with a low-level light beam in advance. A pre-read for reading the outline of the radiation image recorded on the sheet is performed, the pre-read image data obtained by the pre-read is analyzed, and then the sheet is irradiated with a light beam having a higher level than the light beam at the time of the pre-read. There is also a system configured to perform a main reading in which scanning is performed to obtain image data by reading the radiation image under optimum reading conditions (Japanese Patent Laid-Open Nos. 58-67240 and 58-67240).
-67241, 58-67242, etc.).

The reading condition is a general term for various conditions that affect the relationship between the amount of stimulated emission light in reading and the output of the reading device. For example, a reading gain, a scale factor, or a scale factor that determines an input / output relationship. , And the power of the excitation light in reading.

Further, the high level / low level of the light beam means that the intensity of the light beam applied per unit area of the sheet is large / small, or the intensity of the stimulating light emitted from the sheet is the light beam. (Having a wavelength sensitivity distribution) means the magnitude / smallness of the weighted intensity after weighting the intensity of the light beam irradiated per unit area of the sheet by the wavelength sensitivity. Methods for changing the beam level include using a light beam of a different wavelength, changing the intensity of the light beam emitted from a laser light source, etc., and inserting or removing an ND filter or the like in the optical path of the light beam. Various known methods such as a method of changing the beam intensity, a method of changing the scanning density by changing the beam diameter of the light beam, and a method of changing the scanning speed can be used.

In addition, regardless of whether the system performs the pre-reading or the system which does not perform the pre-reading, the obtained image data (including the pre-reading image data) is analyzed, and the optimum image processing conditions for performing the image processing on the image data are determined. Some systems let you decide. The method for determining the optimum image processing conditions based on the image data is not limited to the system using the stimulable phosphor sheet. 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.

When capturing and recording a radiographic image on a recording sheet, it is necessary to prevent radiation from irradiating a part that is not necessary for observation of the subject, or to irradiate a part that is not necessary for observation with radiation necessary for observation from that part. Since scattered radiation enters the area and image quality performance deteriorates, use a field stop that limits the irradiation area of the radiation so that the radiation is irradiated only to the necessary part of the subject and a part of the recording sheet. Often. When the image data is analyzed as described above to obtain the reading conditions and the image processing conditions, if the image data used for the analysis is image data obtained from a recording sheet photographed using an irradiation field aperture, Even if the image data is analyzed ignoring the presence of the irradiation field, the radiographic image that has been captured and recorded is not correctly grasped, and incorrect reading conditions and image processing conditions are required, and a radiographic image selected for appropriate observation is not reproduced and recorded. Cases arise. In order to solve this, it is necessary to recognize the irradiation field and obtain the reading condition and the image processing condition based on the image data in the irradiation field before obtaining the reading condition and the image processing condition.

(Problems to be Solved by the Invention) Incidentally, in each of the above systems, different radiation images are photographed and recorded one by one in a plurality of divided areas on one recording sheet (a stimulable phosphor sheet, an X-ray film, etc.). May be. According to the divided photographing, for example, when photographing a subject smaller than the area of the recording sheet, photographing and recording of a plurality of subjects can be performed on one recording sheet, which is economical. When a sheet is read to obtain image data, a plurality of images can be read at a time, and the reading processing speed is improved.

However, in the radiographic image, the subject portion where the subject was photographed and recorded, the direct radiation portion where the recording sheet was directly irradiated with the radiation without passing through the subject, and the scattered radiation outside the irradiation field when the irradiation field aperture was used. Since there is a scattered radiation part or the like in which only an image is recorded, when the above-described reading conditions and image processing conditions are obtained, an image corresponding to an object part that needs to be finally reproduced as a visible image having excellent observation characteristics is obtained. Despite the need to extract only the data, if these conditions are determined on the assumption that only one radiation image is recorded on the recording sheet without recognizing the division pattern of the recording sheet, the subject Part, the direct radiation part, the scattered radiation part, etc., cannot be well separated, and image data corresponding to the subject part cannot be extracted well.

In order to avoid this, a method of recording the divided pattern at the time of photographing and manually inputting the divided pattern to the apparatus before obtaining image data from the recording sheet, for example, can be considered, but this method requires time and effort. It is time-consuming and very troublesome, and there is a possibility that an input error may occur.

The present invention has been made in view of the above circumstances, and has as its object to provide a method for automatically recognizing a division pattern of a recording sheet so that more appropriate reading conditions and / or image processing conditions can be obtained. is there.

(Means for Solving the Problems) A method for recognizing a divided pattern of a radiation image according to the present invention includes a recording sheet (accumulative phosphor sheet, X
Line film, etc.), the recording sheet is divided into a plurality of portions out of a large number of image data representing the radiographic images, and when each portion is photographed, Based on the image data in the vicinity of the area where the boundary exists, for each of a number of line segments in the direction crossing the boundary, a profile of the image data on each of the line segments is obtained. The changed vertices are determined as boundary candidate points, and the values of the image data at these boundary candidate points are equal to or greater than a first predetermined value when the profile is upwardly convex, and when the profile is downwardly convex, the first value is determined. It is determined whether the value of the image data at these boundary candidate points is not less than the first predetermined value or not more than the second predetermined value. To determine the boundaries Ri, is characterized in that to recognize the division pattern of the recording sheet.

(Operation) When a radiation image is recorded only on a part of the recording sheet,
Since the other part is a part on which another radiation image is recorded or already recorded, it is necessary to prevent unnecessary radiation from being irradiated there. Therefore, for example, as shown in FIG. 3, a portion of the recording sheet other than the portion where the radiation image is recorded is a shield 6 that does not transmit radiation.
The photographing is performed after placing the. When the imaging is performed with the shields arranged in this way, there is an error in the arrangement of the shields. For example, as shown in FIG. It usually occurs that the parts overlap (double exposure part-area C) and that a plurality of radiation images are slightly separated (partition line-area D), for example, as shown in FIG. 4B. These areas also
Since the density of the image differs greatly from that of the other image portions, in the case of the region C which is a double exposure portion, the profile of the image data on the line segment in the transverse direction changes upwardly convex as shown in FIG. 5A, In the case of region D which is a dividing line, the above profile
As shown in FIG. 5B, the shape changes downward. Further, the value of the image data (corresponding to the density) at the apex of the profile that changes upward or downward convexly is larger than the value of the image data in the normal image area (the area irradiated with the radiation transmitted through the subject). Because it ’s much larger or smaller,
The value of the image data at these vertices is a ratio of the histogram width (Smax-Smin) to the maximum value (Smax) or the minimum value (Smin) in the histogram of the entire image data as shown in FIG. It has a value larger or smaller than the inner values Th ₁ and Th ₂ (for example, about 10%).

The present invention has been made in view of this,
For each of a large number of line segments in the direction crossing the boundary, a profile of image data on each of the line segments is obtained, and vertices that change upward or downward in the profile image to be convex or downward are determined as boundary candidate points. By dividing a line segment along a point as a boundary between a plurality of radiation images, a division pattern of a recording sheet is recognized. In addition, there is a possibility that a portion that changes upward or downward on the profile exists other than at the boundary. In this invention to determine whether a number of boundary candidate points was thereby determined as described above whether the larger than the predetermined value Th _1, also or Th ₂ smaller, if Th ₁ or more, and Th ₂ or less The straight line is defined as a boundary.

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

(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 radiographic apparatus constituting a system using the divided pattern recognition method of the present invention. This system uses the above-described stimulable phosphor sheet as a recording sheet for capturing and recording a radiation image.

The radiation 2 emitted from the radiation source 1 passes through the subject 3 and is irradiated onto the stimulable phosphor sheet 11. An area 5 (direct radiation portion) is formed around the sheet 11 where the radiation transmitted through the subject 3 is irradiated and the sheet 11 is directly irradiated with the radiation without passing through the subject 3. About one half of the sheet 11 is used for one imaging in this imaging, and the other half is covered with a shielding member 6 that shields the radiation so as not to be irradiated. By performing such imaging on the left and right sides of the sheet 11, two radiation images are formed on one sheet 11.

4A and 4B show one sheet 11 as described above.
FIG. 5 is a diagram showing a state where two radiation images A and B are formed on the left and right at the top. In each of the images A and B, there are formed subject portions 3A and 3B in which a radiation image of the subject 3 is recorded, and direct radiation portions 5A and 5B in which the sheet 11 is directly irradiated with radiation.

4A and 4B, the sheet 6 for photographing
, An overlapping area C in which two images A and B partially overlap each other, and an unexposed area D in which only scattered radiation is recorded, in which none of the two images A and B are recorded.
Exists. Theoretically, it is conceivable that the two images A and B are formed so as to be in contact with a straight line. However, in reality, such a case is extremely rare, and in rare cases, the images are formed so as to be in contact with one straight line. Even when the two images A and B partially overlap due to the influence of the scattered radiation, it often happens. Therefore, it may be considered that the overlap region C or the unexposed region D exists with a sufficiently high efficiency for practical use.

FIG. 7 is a perspective view showing one embodiment of a radiation image reading apparatus using an example of the divided pattern recognition method of the present invention. This apparatus reads, for example, a radiation image as shown in FIGS. 4A and 4B, which is photographed and recorded on the stimulable phosphor sheet 11 by the photographing apparatus shown in FIG. It is a device that performs.

The stimulable phosphor sheet 11 on which the radiation image has been recorded is first scanned at a predetermined position of the pre-reading means 100 which scans with a weak light beam and releases only a part of the radiation energy stored in the sheet 11 to perform pre-reading. Set. The stimulable phosphor sheet 11 set at this predetermined position is conveyed (sub-scanning) in the direction of arrow Y by sheet conveying means 13 such as an endless belt driven by a motor 12. On the other hand, the weak beam 15 emitted from the laser light source 14 is reflected and deflected by the rotating polygon mirror 16 driven by the motor 23 and rotated at high speed in the direction of the arrow, and after passing through the focusing lens 17 such as an fθ lens, the optical path is changed by the mirror 18. Instead, the light is incident on the sheet 11 and is main-scanned in an arrow X direction substantially perpendicular to the sub-scan direction (arrow Y direction). From the portion of the sheet 11 to which the light beam 15 has been irradiated, a stimulating luminescent light 19 of a light amount corresponding to the accumulated and recorded radiation image information is diverged, and the stimulating luminescent light 19 is guided by a light guide 20. , Are photoelectrically detected by a photomultiplier (photomultiplier tube) 21. The light guide 20 is formed by molding a light-guiding material such as an acrylic plate, and is arranged such that a linear incident end face 20a extends along a main scanning line on the stimulable phosphor sheet 11. The light receiving surface of the photomultiplier 21 is connected to the emission end face 20b formed in an annular shape. The stimulated emission light 19 entering the light guide 20 from the incident end face 20a is
Of the photomultiplier 21 which is emitted from the emission end face 20b and received by the photomultiplier 21, and the amount of photostimulated light 19 representing a radiation image is determined by the photomultiplier 21.
Is converted into an electric signal.

The analog output signal S output from the photomultiplier 21 is logarithmically amplified by a logarithmic amplifier 26, and the A / D converter 2
Digitization is performed in step 7, and pre-read image data Sp is obtained.
The pre-read image data Sp is data having a value proportional to the logarithm of the amount of stimulated emission light.

In the pre-reading, reading conditions such as a voltage value applied to the photomultiplier 21 and an amplification factor of the logarithmic amplifier 26 are determined so that the radiation energy stored in the stimulable phosphor sheet 11 can be read over a wide area. Have been.

The obtained pre-read image data Sp is input to the storage means 28 and is temporarily stored. After that, the pre-read image data Sp stored in the storage means 28 is read and input to the calculating means 29, and based on the input pre-read image data Sp, the calculating means 29 first reads the stimulable phosphor sheet 11 The upper part is divided into a plurality of regions, and a division pattern in a case where the photographing is performed for each of the regions is recognized. Next, an optimum reading condition for each of the divided regions is obtained. By obtaining the reading conditions, the reading conditions G ₁ for the main reading, for example, the voltage applied to the photomultiplier 21 ′ and the logarithmic amplifier 26 ′
Is required.

The stimulable phosphor sheet 11 'for which pre-reading has been completed is set at a predetermined position of 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 pre-reading, as described above. image data is obtained by the condition G ₁ read defined Te, but the configuration of the reader in step 100 'because it is configured substantially the same as the destination reader in stage 100, corresponding to the components of the previous reader in stage 100 configured Elements are indicated by adding dashes to the numbers used in the look-ahead means 100, and descriptions thereof are omitted.

Image data S _Q obtained by being digitized by A / D converter 27 'is sent to the image processing unit 50. Appropriate image processing is performed on the image processing unit 50, image data S _Q. The image data subjected to the image processing is sent to the reproducing device 60, and a radiation image based on the image data is reproduced and displayed.

Here, a method of recognizing the division pattern based on the pre-read image data Sp by the calculating means 29 will be described.

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

On this sheet 11, two radiation images A and B arranged on the left and right sides of the sheet 11 are formed. In the system of this embodiment, as a pattern for forming a radiation image on one sheet 11, When one image is formed on the entire surface of the sheet 11, two independent radiation images arranged side by side as shown in FIG. 1 are divided into two substantially right and left along a line E shown in FIG. , The line segment F shown in FIG.
, And two cases where the image is divided into four regions divided by two of the line segments E and F.

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

First, from the pre-read image signal Sp corresponding to the entire surface of the sheet 11, the pre-read image data Sp in the vicinity of the region where the boundary lines E and F exist, that is, the oblong hatched region H and the horizontally long region I in FIG. Is read out, and based on these prefetched image data Sp, a number of line segments in the direction crossing each of the boundary lines E and F, that is, in the directions parallel to the ξ axis and the η axis, respectively. For each, a profile of the pre-read image data Sp on each line segment is obtained. FIG. 1 shows profiles J and K of the pre-read image data Sp on the ξ axis and η axis among these many line segments. Next, the presence or absence of a portion that changes upward or downwardly appearing on these profiles is searched, and if it does exist, its vertex is determined as a boundary candidate point. The radiation image shown in FIG. 1 is the same image as the image shown in FIG. 4A, and has an overlapping area C (see FIG. 4A) where two radiation images A and B overlap. For this reason, the profile J on the が axis has a portion that changes upwardly convex, and the vertex L thereof is set as a boundary candidate point.

In the profile K of the η-axis, there is no extremely upwardly or downwardly convex portion, and no boundary candidate point is determined.
If any of the profiles on a number of line segments parallel to the η axis has a portion that changes upward or downward similar to the boundary of the image, and the vertex is determined as a contour candidate point,
These outline candidate points are determined at different positions by each line segment, and these candidate points do not line up substantially on a straight line, and no boundary is determined.

On the other hand, in each profile corresponding to a number of line segments parallel to the 部分 axis, there is always a portion that changes to an upwardly convex shape, and a contour candidate point is determined.

FIG. 2 is a diagram showing a number of boundary candidate points (marks) obtained on the radiation image shown in FIG.

After a number of boundary candidate points are determined as described above,
It is determined whether these disclosure candidate points are greater than a _first predetermined value Th1. As shown in FIG. 2, a large number of boundary candidate points are arranged on the line segment E, and the line segment E is determined as the boundary of the image. On the other hand, the number of boundary candidate points is small in the direction of the line segment F,
In addition, these boundary candidate points are not arranged in a straight line. Therefore, it is determined that the line segment F is not a boundary line. Therefore, it is determined that two radiographic images separated left and right by the boundary line E are recorded on the sheet 11.

When the division pattern is obtained in this way, next,
Pre-read image data Sp corresponding to the radiation image in each divided area
From the object portions 3A and 3B of the image (see FIGS. 1A and 1B)
Is extracted, and based on this, the optimal reading condition is obtained for each divided area.

However, in the apparatus shown in FIG. 7, the reading conditions for the main reading cannot be changed for each image in one sheet 11 even if a plurality of images are recorded in one sheet 11.
In this apparatus, after the reading conditions for each of the divided areas are obtained as described above, an average reading condition of these reading conditions is obtained, and the average reading condition is determined as the reading condition G _{1 for} the main reading.
It is said.

Further, in the above embodiment, an example in which a plurality of images overlap (see FIGS. 4A and 5A) has been described. However, when a plurality of images are apart (see FIGS. 4B and 5B), Instead of defining a vertex having a convex shape on the profile as a boundary candidate point, a vertex (bottom point) having a downward convex shape is defined as a boundary candidate point, and the value of image data at this point is set to a first predetermined value Th. By judging whether or not it is smaller than a _second predetermined value Th2 that is smaller than _1, the boundary can be obtained in exactly the same manner.

In the above embodiment has described the case where the arithmetic unit 29 obtains the reading condition G ₁ during the real reading, during real reading is a reading at a predetermined reading condition regardless prefetching image data Sp, operation in means 29, on the basis of the preliminary read-out image data Sp, determined image processing conditions G ₂ when performing image processing on the image data S _Q in the image processing unit 50, by the operation means 29 as indicated by broken lines in FIG. 7 The obtained image processing condition may be input to the image processing means 50, or the arithmetic means 29 may obtain both the reading condition and the image processing condition.

Further, in the above embodiment shown in FIG.
And the main reading unit 100 'are separately configured, but since the configuration of the pre-reading unit 100 and the main reading unit 100' is substantially the same as described above, the pre-reading unit 100 and the main reading unit 100 ' May be integrated and shared. In this case, after pre-reading, the stimulable phosphor sheet 11 may be backed once and then scanned again to perform main reading.

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

Further, in the above-described embodiment, the radiation image reading apparatus which performs pre-reading is described. However, the present invention can be applied to a radiation image reading apparatus which performs reading corresponding to the above-mentioned main reading from the beginning without performing pre-reading. . in this case,
At the time of reading, image data is obtained by reading under predetermined reading conditions. Based on the image data, a division pattern of the radiation image is obtained by the calculating means, and further image processing conditions are obtained. The obtained image processing conditions are considered when performing image processing on the image data.

In addition, the present invention can be used not only for an apparatus using a stimulable phosphor sheet but also for an apparatus using a conventional X-ray film.

FIG. 8 is a perspective view of an embodiment of an X-ray image reading apparatus for reading an X-ray image recorded on an X-ray film.

An X-ray film 30 set at a predetermined position and having an X-ray image recorded thereon is conveyed by a film conveying means 31 in the direction of the arrow Y ″ shown in the figure.

Further, the reading light 33 emitted from the light source 32 extending one-dimensionally long is converged by a cylindrical lens 34,
The linear film is irradiated linearly in the X ″ direction substantially perpendicular to the arrow Y ″ direction. Below the X-ray film 30 illuminated with the reading light 33, the above-mentioned position is set at a position where the reading light 33 that transmits the X-ray film 30 and is intensity-modulated by the X-ray image recorded on the X-ray film 30 is received. Many solid-state photoelectric conversion elements corresponding to each pixel interval in the X ″ direction of the X-ray image are linearly arranged.
A MOS sensor 35 is provided. This MOS sensor 35 is
While the line film 30 is irradiated with the reading light 33, the arrow Y "
While being conveyed in the X direction, the reading light transmitted through the X-ray film 30 is received at a predetermined time interval 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.

A signal generated by a photocarrier generated when the reading light 33 irradiates a large number of fixed photoelectric conversion elements 36 is a solid-state photoelectric conversion element 36.
Are stored in the capacitors Ci (i = 1, 2,..., N). The accumulated photocarrier signals are sequentially read out by sequentially opening and closing the switch unit 38 controlled by the shift register 37, whereby time-sequential image signals are obtained. This image signal (image data) is then amplified by the amplifier 39 and output from the 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 above-described embodiment. In this embodiment, it goes without saying that a CCD, a charge priming device (CPD), or the like can be used instead of the MOS sensor 35. Further, in reading the X-ray film, it is a matter of course that reading may be performed by two-dimensionally scanning with a light beam similarly to the reading of the stimulable phosphor sheet described above. In the above embodiment, the light transmitted through the X-ray film 30 is received.
Of course, it can be configured to receive the light reflected from the X-ray film 30.

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

(Effects of the Invention) As described above in detail, the method for recognizing a divided pattern of a radiation image according to the present invention can be applied to a case where a recording sheet is divided into a plurality of portions and an image is taken for each of the divided portions. Based on the image data in the vicinity of the region where the boundary of each part exists, for each of a number of line segments in the direction crossing the boundary, a profile of image data on each of the line segments is obtained, and an upper or lower portion that appears on the profile is obtained. The vertices which have changed to convex are determined as boundary candidate points, and it is further determined whether or not the density at these boundary candidate points is significantly different from the others. If the density at these boundary candidate points is extremely high or low, the straight line Is determined as the boundary, so that the division pattern of the recording sheet is accurately recognized.

By recognizing the divided pattern, more accurate reading conditions and image processing conditions are obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a radiographic image and pre-read image data obtained from the radiographic image. FIG. 2 is a diagram showing a number of boundary candidate points obtained on the radiographic image shown in FIG. 3) is a perspective view schematically showing an example of a radiographic apparatus, and FIGS. 4A and 4B are states in which two radiographic images are formed on the left and right of one sheet. FIGS. 5A and 5B are diagrams showing examples of profiles of image data having an upward convex and a downward convex, and FIG. 6 is a diagram showing thresholds Th ₁ , Th ₂
FIG. 7 is a perspective view of an embodiment of a radiation image reading apparatus using an example of the divided pattern recognition method of the present invention, and FIG. 8 is a view recorded on an X-ray film. FIG. 9 is a perspective view of an embodiment of an X-ray image reading apparatus for reading an X-ray image, and FIG. 9 is a circuit diagram showing an equivalent circuit of a MOS sensor. 1 radiation source 2, radiation 3 subject, 3A, 3B subject part 5A, 5B direct radiation part 6, shielding object 11, 11 '... stimulable phosphor sheet 19, 19' Photostimulated light 21,21 'Photomultiplier 26,26' Logarithmic amplifier 27,27 'A / D converter 28 Storage means 29 Calculation means 30 X-ray Film 35, MOS sensor 50 Image processing means 60 Reproducing device 100 Pre-reading means 100 'Main reading means

Claims (1)

(57) [Claims] A plurality of image data representing a radiation image obtained from a recording sheet on which the radiation image is recorded;
When the recording sheet is divided into a plurality of portions, and when photographing is performed for each of the divided portions, a large number of directions in the direction crossing the boundaries are determined based on image data near an area where the boundaries of the respective portions exist. For each of the line segments, a profile showing a change along the line segment of the image data on each of the line segments is obtained by a curve, and a vertex of a changed portion that appears in a convex shape on the profile is determined as a boundary candidate point. The value of the image data at the boundary candidate point is larger than the first predetermined value when the value of the image data in the convex change portion is larger, or the value of the image data in the convex change portion Is smaller than the first predetermined value, it is determined whether the value is smaller than the second predetermined value. If the value of the image data at these boundary candidate points is smaller than the first value,
A straight line is set based on the boundary candidate point when the predetermined value is equal to or more than a second predetermined value, and the divided pattern of the recording sheet is recognized by defining the straight line as the boundary. A method for recognizing a division pattern of a radiation image.