JP2929030B2 - Digital radiographic image position determination device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital radiographic image capturing position discriminating apparatus, and more specifically, converts a radiographic image captured as a radiation dose transmitted through a subject into digital signals to generate various signals. The present invention relates to an apparatus for automatically determining a photographing position for determining processing conditions when performing processing.

<Prior Art> Radiation images such as X-ray images are widely used for medical purposes, and the following methods are available for obtaining this radiation image as an electric image signal.

That is, the radiation that has passed through the human body as a subject is absorbed by a certain kind of phosphor, and then the phosphor is excited by light or heat energy, so that the radiation energy that the phosphor has accumulated by the absorption is absorbed. Radiation is emitted as fluorescent light, and this fluorescent light is detected by a photoelectric conversion element to obtain radiation image information electrically.Then, the radiation image signal is digitized, and then subjected to gradation processing and spatial frequency processing to be applied to a CRT or the like. Processing and visualization (Japanese
See 3-189853, etc.).

By the way, in the processing stage before outputting a digital radiation image signal as a visible image as described above, it is necessary to perform a gradation process and a spatial frequency process as described above to obtain a visible image suitable for image interpretation. However, even if the image data is of the same part of the human body, when the image is taken while changing the photographing position (the direction of the human body as the subject), the density of the region of interest in the part in each reproduced image changes. Sometimes.

For example, in order to diagnose the thoracic vertebra, when the human chest is photographed from the front as shown in FIG. 5, the thoracic vertebra, which is the region of interest, overlaps the mediastinum, which is difficult to transmit radiation, as shown in FIG. When the image is taken from the side, it overlaps with the lung field where radiation is easily transmitted. Therefore, when such image data is processed under the same image processing conditions and then reproduced, the thoracic vertebrae portion has a relatively low density in the front image and a relatively high density in the side image.

Therefore, various methods and apparatuses have been proposed for performing optimal image processing for each position by automatically determining in which position the image data was taken.

As this method and apparatus, there are a method using a density histogram of image data and a method using a signal level distribution (hereinafter, referred to as a projection) in a predetermined direction of the image in the image data. (JP-A-63-262128, JP-A-63-262128)
262132, JP-A-63-262134, JP-A-63-2621
JP-A-63-262129, JP-A-63-262135, etc.), and those that perform function approximation (see JP-A-63-262135). No. 106642, JP-A-63-262130, JP-A-63-262131, JP-A-63-262137, JP-A-63-262138 and the like.

Further, a method for obtaining a representative value or a characteristic value from a density histogram (see Japanese Patent Application Laid-Open No. 63-106641, etc.), a method for obtaining a variance of the density histogram (see Japanese Patent Application Laid-Open No. 63-262133, etc.) A device for calculating the sum of signal values near the center in the direction (see Japanese Patent Application Laid-Open No. 63-262136) has been proposed.

<Problem to be Solved by the Invention> However, in the above method, even when using the density histogram, or even when using projection, the amount of calculation for automatically determining in which position the image was taken was calculated. Lots were a problem. For example, a standard pattern of front image data and a standard pattern of side image data are obtained from many pieces of image data, and the similarity between the standard pattern and subsequently input data is checked (Japanese Patent Laid-Open No. 63-262130). In JP-A-63-262137, a complicated method such as multiple regression analysis must be used to obtain a standard pattern, and the amount of calculation increases.

When the photographing position is determined by using the density histogram, the photographing position is determined by capturing the difference in shape of the density histogram. Since the shape difference between the density histogram and the density histogram is small, the number of erroneous determinations increases.

Furthermore, when the photographing position is determined using projection, if there is a lateral displacement of the human body within the photographing range, the projection pattern based on the image data changes even if the photographing position is the same. For this reason, there is a problem that the accuracy of determining the photographing position cannot be ensured.

The present invention has been made in view of the above problems, and has as its object to provide an apparatus that can accurately determine the photographing position of a subject in a digital radiation image with a small amount of calculation.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. 1, a level distribution detecting means for detecting a level distribution of a digital radiation image signal in a predetermined direction of an image, and the level distribution detecting means Comparing the detected signal level of the level distribution with a plurality of types of signal level thresholds, and calculating a magnitude change pattern of the signal level with respect to each of the thresholds along the image predetermined direction; Photographing position discriminating means for discriminating the photographing position of the subject in the digital radiation image signal based on the number of each type of magnitude change pattern for each threshold value detected by the magnitude change pattern detection means. A posture determination device is configured.

Here, the photographing position discriminating means can be configured to discriminate the photographing position of the subject by comparing the number of patterns that are the same as the reference magnitude change pattern stored in advance with a predetermined number.

Further, it is preferable that the photographing position determining means is configured to determine the photographing position of the subject by combining a plurality of determinations by comparing the number of specific magnitude change patterns with a predetermined number.

On the other hand, it is preferable that the level distribution detecting means detects the distribution of the signal levels by using the total value or the average value of the signal levels of the pixel rows substantially orthogonal to the predetermined direction of the image for which the level distribution is detected.

Further, the level distribution detecting means may be configured to detect the signal level distribution using the signal level of each of the pixel rows along the predetermined image direction for detecting the level distribution as it is.

Further, as shown by a dotted line in FIG. 1, a signal thinning means for reducing at least one of the number of pixels of the digital radiographic image and the number of quantization steps of the signal is provided. Preferably, the level distribution is detected based on a digital radiation image signal in which at least one of the number of pixels and the number of quantization steps of the signal is reduced.

Further, as shown by the dotted line in FIG. 1, the level distribution detecting means is provided with a contrast enhancement correcting means for performing a correction for enhancing the contrast so that the distribution of the density histogram of the digital radiographic image is expanded to the digital radiographic image signal. Preferably, the level distribution is detected based on the digital radiation image signal corrected by the contrast enhancement correction means.

Further, as shown by a dotted line in FIG. 1, a level distribution smoothing means for smoothing the level distribution detected by the level distribution detecting means is provided. It is preferable to obtain a large / small change pattern based on the level distribution smoothed by the above.

<Operation> According to the digital radiographic image capturing position determining apparatus having the above-described configuration, the state of the signal level distribution in the predetermined image direction, more specifically, the state of the change in the signal level in the predetermined image direction is determined by one Instead of making judgments with thresholds, it is possible to estimate two-dimensionally the undulations in the level distribution by cutting them with a plurality of types of thresholds. The photographing position is determined based on the number of each pattern type.

Here, in determining the photographing position of the subject based on the number of the size change patterns by type, a predetermined number is compared with the number of patterns that are the same as the reference size change pattern stored in advance. By knowing in advance the photographing position at the time of the level distribution that indicates many of the reference size change patterns, it is possible to determine whether or not the photographing position corresponds to the reference size change pattern. By combining the discrimination based on the comparison between the number of specific magnitude change patterns and a predetermined number, it is possible to accurately discriminate a plurality of types of photographing positions.

When detecting a level distribution of a digital image signal in a predetermined image direction, a total value or an average value of signal levels of respective pixel rows substantially orthogonal to the predetermined image direction may be used, or pixels along the predetermined image direction may be used. The signal level of each column may be used as it is.

Further, after reducing at least one of the number of pixels of the digital radiographic image and the number of quantization steps of the signal, or performing a correction for enhancing the contrast so that the distribution of the density histogram of the digital radiographic image is expanded, the level distribution is performed. Is detected, the magnitude change pattern can be detected based on a small amount of data, and the characteristics of the photographing position can be easily grasped.

In addition, if the detected level distribution is smoothed, it is possible to prevent the determination of the photographing position from being affected by a minute level change.

<Examples> Examples of the present invention will be described below.

FIG. 2 shows an embodiment of a digital radiation image radiographing position determining apparatus according to the present invention.

Here, the image input unit 1 scans a latent image of a radiation image stored (accumulated) on the stimulable phosphor with a laser beam and reads the latent image. Image scanner to signal, or
For example, a filing system in which a plurality of digital radiation image data are recorded.

Original digital radiation image data f (x, y) input from the image input unit 1 is temporarily stored in the frame memory 2 and passed to the image processing unit 3. The image data f (x, y) (x = 1, 2,..., Nx, y = 1, 2,..., Ny) is x, y
In this embodiment, a pixel column extending in the x direction (horizontal direction in FIG. 3) is defined as a “row”, and the y direction (vertical direction in FIG. 3). Are referred to as “columns”.

The image processing unit 3 includes a configuration necessary for the photographing posture determination device according to the present invention, and performs gradation conversion, frequency emphasis, and frequency conversion so that a visible image suitable for image interpretation is reproduced based on the determination result of the photographing posture. A processing image processing unit 4 for performing various image processing and analysis such as contour extraction is provided.

As will be described later in detail, the characteristic pattern storage unit 5 stores a reference pattern, which is data necessary for determining the photographing posture, a threshold value Th for determining the number of the patterns, a threshold value T for determining a signal level, and the like. I remember.

In the image output unit 6 to which the image data processed by the output image processing unit 4 is input, the image data (digital radiation image signal) after the image processing is recorded again in the filing system or reproduced on the CRT. Or recording on film by a printer. Here, when filing the image data after determining the photographing position of the subject (in this embodiment, the human body) into the filing system, the image data is taken together with the image information such as the patient name, the photographing site name, and the photographing date. If the body position is recorded in correspondence with the image data, it is convenient for later retrieval, and it is not necessary to repeatedly determine the photographing position.

Next, an embodiment of a digital radiographic image capturing position determination apparatus according to the present invention will be described along each of the processing units 11 to 16 included in the image processing unit 3.

Original digital radiation image data f (x, y) temporarily stored in the frame memory 2 is first input to a signal thinning unit (signal thinning means) 11 in the image processing unit 3.

The signal thinning unit 11 thins out the number of pixels and the number of gradations (the number of quantization steps) of the original digital image data f (x, y) to reduce the amount of image data used for the photographing position determination, and performs the following calculation. Try to reduce the volume.

Specifically, the original digital image data f (x,
y) is divided into a plurality of small areas, and the number of pixels and the number of gradations are reduced by calculating the average value and representative value of the signal values for each small area. For example, even if the processing of thinning out the original digital image data f (x, y) of 2048 × 2646 pixels and 1024 gradations to 128 × 154 pixels and 256 gradations is performed, the photographing posture determination according to the present invention is performed. Can be performed without any trouble.

It should be noted that the image data on which the number of pixels and the number of gradations have been decimated by the signal decimating unit 11 are represented by f ′ (x ′, y ′) (x ′ = 1, 2,
..., Nx ', y' = 1,2, ..., Ny ') (Nx'<Nx, Ny '
<Ny).

However, the above-described thinning-out processing is for further reducing the amount of calculation in the photographing posture determination apparatus according to the present invention, which requires a small amount of calculation, and the thinning-out processing may be omitted.

In the next contrast enhancement correction section (contrast enhancement correction means) 12, the image data f '(x',
y ′) is performed as necessary to obtain contrast-enhanced data f ″ (x ′, y ′). This is because the signal value (shade value) of the original image data has a very small difference in shading. In order to prevent the height difference between peaks and valleys drawn by a distribution curve from being reduced when a projection (signal level distribution along a predetermined image direction in image data) is created, This is a process to be performed, in which the contrast difference is emphasized to emphasize the density difference so that the characteristic of the shading change of the image data related to the photographing position determination is clearly shown.

The enhancement of the contrast is performed using, for example, the following known technique ("Introduction to Computer Image Processing"), supervised by Hideyuki Tamura, published by Soken Publishing Co., Ltd.).

Assuming that the level range of the signal before emphasis is [a _min , a _max ] and the signal range after emphasis is [b _min , b _max ], the signal value S _orig before emphasis is set to the contrast emphasis signal by the following equation or equation. Convert to value S _proc .

Here, when contrast enhancement is performed using the equation, the density is linearly converted, and the equation is nonlinearly converted.

Also, the signal value S _orig before emphasis is normalized so that the density histogram of the average density value m and the standard deviation σ is normalized to the density histogram of the average value m _norm and the standard deviation σ _norm as in the following equation.
_May be converted to a contrast enhancement signal value _Sproc .

Further, the contrast can be enhanced by flattening the density histogram so that the number of pixels in the entire density range becomes equal.

Next projection creation unit (level distribution detection means)
In 13, a projection p (x ') (level distribution along the image X direction) is created based on the image data f "(x', y ') on which the signal thinning process and the contrast enhancement correction process have been performed.

The projection p (x ′) is obtained by converting image data f ″
A distribution represented by the following expression in (x ', y') can be used (however, as shown in FIG. 3, 1 ≦ n1 ≦ n2
≤Ny ', the signal sampling range is n1≤y'≤n2
And ).

That is, the expression calculates the sum of the signal values of the image data f ″ (x ′, y ′) for each pixel row extending in the vertical direction (y direction) of the image. The expression calculates the image data f ″ (x ′, y ′) The average value of the signal values for each pixel row extending in the vertical direction of the image is calculated. In some cases, the image data f ″ (x ′, y ′)
The sum or average value of signal values for each pixel row extending in the left-right direction (x-direction) can also be used.

In the present embodiment, as described above, the projection is created based on the sum or average value of the signal values of the respective pixel columns. However, the signal value of each pixel in the specific pixel row is used as it is in the X direction of the image. A projection indicating a signal level change along the (left-right direction) may be created. However, it is necessary to appropriately select the specific pixel row so that the characteristics of the photographing position are clearly shown.

Since the projection p (x ') obtained by the projection unit 13 includes a small change in the signal value as shown in FIG. 4, when a large / small change pattern with respect to a threshold T described later is detected. The projection p (x ') is smoothed (smoothed) so that this small change is not regarded as a large or small change indicating the characteristic of the photographing position.
This processing is performed by the next smoothing processing unit (level distribution smoothing means) 14.

In the smoothing process, for example, the projection p
This can be performed by replacing the point of interest in (x ') with an average value in the vicinity thereof. As shown in FIG. 4, the horizontal position of each point in the projection p (x ') is x' and its signal value is a function of p (x '). When performing, the value p ′ (i) after the smoothing processing at the position i is By executing such processing a plurality of times, a small change in signal value as shown in FIG. 4 is smoothed. Note that the median value in the vicinity can be used for the smoothing processing in the smoothing processing unit 14.

Next, the change pattern detecting section (large / small change pattern detecting means) 15 sequentially compares each value of the smoothed projection p ′ (x ′) with a plurality of types of signal thresholds T, thereby obtaining each threshold value. A pattern of magnitude change of the signal level with respect to T is obtained, and the next photographing position discriminating section (photographing position discriminating means) 16 includes the number of the same patterns as the characteristic patterns characteristically present in the specific photographing position in this fluctuation pattern. The photographing position is determined according to the number.

That is, in the case of the front and the side of the human chest radiographic image, in the distribution of the signal lines in the horizontal direction of the image indicated by the straight line L in FIGS. There is a valley of the signal level representing the thoracic vertebra, which is hard to transmit radiation, there are peaks of the signal level indicating the lung field that is easy to transmit radiation on both sides, and furthermore, the thorax, which is hard to transmit radiation, at the left and right ends There is a trough of the signal level to represent. on the other hand,
In the side surface image, there are peaks of the signal level indicating the radiation-free portion at the left and right ends, a valley indicating the body side near the center, and a characteristic waveform hardly appears at the body side. This characteristic is substantially the same even when the distribution of the sum or average value of the signal values of each pixel row in the direction orthogonal to the straight line L is obtained.

Here, when the signal level of the projection is sequentially compared with the threshold value T while changing the signal level threshold value T, a portion where each value of the projection is smaller than the threshold value T continues, then changes to a large portion, and then decreases again. Patterns of fluctuations such as continuous portions are sampled by the number of thresholds T, and these fluctuation patterns largely differ depending on whether the photographing position is the front or the side, as is clear from FIGS.

As described above, since a pattern that appears frequently in the front image and a pattern that appears frequently in the side image are respectively specified, if characteristic patterns corresponding to these photographing positions are obtained in advance, the input image data The photographing position can be determined based on the number of patterns having the same pattern as the characteristic pattern among patterns corresponding to the threshold T obtained by comparing the projection with the threshold T.

Next, the detection of the magnitude change pattern and the determination of the photographing position will be specifically described.

Change pattern detector (large and small change pattern detection means) 15
Then, each point of the projection p '(x') is sequentially compared with a threshold T from the end, and for example, 1 is given if the value on the projection is larger than the threshold T, and 0 is given if the value is smaller than the threshold T. Here, the length that 1 or 0 continues, that is, 1 and 0
If the code 1 is assigned to the run 1 and the code 0 is assigned to the run 0, the repetition pattern of the codes 1 and 0 indicates how the waveform of the projection changes with respect to the threshold T. Will be. Further, if the threshold T is changed in a preset step and the above-mentioned setting of the 1,0 sign is performed over the entire range of the signal value, the waveform state in the projection can be two-dimensionally grasped. , Which is the feature of the projection 1,
Many change patterns of 0 appear.

For example, as shown in FIG. 7, the range t ₀ of the signal value
In until t _6, when the threshold value T went varied at intervals of [Delta] T, as shown in Table _{1, t n ≦ T <t} n + 1 (n = 0,1,
.., 5), the characteristic patterns in the order of code 0 and code 1 and the number of the characteristic patterns are obtained.

When such processing is performed for each of the radiation image data shown in FIGS. 8 to 12, the front image is (01010) in FIG. 8 which is a front image, and (101) is in FIG. In FIG. 10, the pattern (10101) is detected, and in FIG. 11, which is a laterally shifted image, (10), and in FIG. 12, which is a front image of a child or a thin person, the pattern (1010101) is frequently detected. In each image, there are only a few patterns other than the above. Therefore, (0101
0), (10101), and (1010101) are used as the feature pattern for the front image (the reference size change pattern of the front).
If the patterns (101) and (10) are stored in advance in the feature pattern storage unit 5 as feature patterns for side images (reference size change patterns of side surfaces), the projection of the input image data will By comparing the information indicating whether the human body has a large number of images with the information on the characteristic pattern corresponding to the photographing position stored in the characteristic pattern storage unit 5, the photographing position determining unit (photographing position determining means) 16 It is possible to determine whether the photographing position is an image photographed from the side or an image photographed from the side of a human body.

It is preferable that the threshold value T of the signal level used for the above-described projection waveform discrimination is obtained in advance for each characteristic pattern and stored in the characteristic pattern storage unit 5 together with the characteristic pattern. At the time of discrimination, as shown in the flowchart of FIG. 14, the number of each feature pattern in the input image data is sequentially compared with each threshold (Th1 to Th5), and the input image data is compared. The determination may be made based on whether or not the data has a certain number of characteristic patterns or more. Alternatively, as shown in the flowchart of FIG.
The photographing position may be determined in comparison with 7).

In the discrimination shown in the flowchart of FIG. 14, the standard front (see FIG. 8), standard side (see FIG. 9), front right shift (see FIG. 10), side right shift (see FIG. 11), front small (See FIG. 12.) The number of each feature pattern is determined individually, and the five types of photographing positions can be determined.

That is, the flowchart of FIG. 14 includes preprocessing for performing the photographing posture determination, in which the original image data is input in S1, the signal thinning processing is performed in S2, and the contrast is further enhanced in S3. I do. Then, a projection is created in S4 based on the image data subjected to these processes, and a process of smoothing the projection is performed in the next S5.

In S6, the signal level of the smoothed projection is compared with the threshold value T while changing the threshold value T, and a magnitude change pattern of the signal level is detected for each threshold value T.

As for the detected magnitude change pattern for each threshold T, the number of the same patterns is obtained, and is used for the photographing posture discrimination after S7.

In S7, the number of patterns that were the same as (01010), which is a pattern characteristically appearing in the standard frontal posture as shown in FIG. 8, is compared with the threshold number Th1 of the number of patterns. When the pattern of (01010) appears,
In S8, it is determined that the photographing position is the standard front as shown in FIG.

Similar determinations are made in steps S9 to S16. In step S9, the number of feature patterns (101) on the standard side face is determined. In step S11, the number of feature patterns (10101) on the right front side is determined. The number of feature patterns (10) is determined, and further, S1
In 5, the number of (1010101) which is the feature pattern of the front small is discriminated, and when each is larger than the threshold value Th2 to Th5, any one of the postures of the corresponding feature pattern (side standard, front right shift, side right shift, front small) It is determined that the image has been photographed in (1) (S10, 12, 14, 16).

Then, the number of patterns that are the same as the patterns characteristically appearing in the above five types of photographing positions is equal to the threshold value Th1 to Th5
If smaller, it is not any of the front standard, the side standard, the right front deviation, the right side deviation, and the small front, and it is determined in S17 that the photographing position is "other".

On the other hand, in the determination shown in the flowchart of FIG. 15, the determination is simplified, and the photographic position is determined into two types, the front and the side, regardless of the presence or absence of a positional shift. That is, S21 to S26 of the preprocessing
14 is the same as S1 to S6 in the flowchart of FIG. 14, but in S27 in the photographing posture determination, the number of patterns corresponding to the standard front, the number of patterns corresponding to the front right shift, and the pattern corresponding to the small front When the sum of the patterns appearing when the front is in any of the above cases exceeds a predetermined threshold Th6, the photographing position is not determined in S28 without distinguishing between the standard front, the front right shift, and the front small. It is determined that it is the front.

Then, when it is determined in S27 that the number of frontal patterns is equal to or smaller than the threshold Th6, in S29, the sum of the number of patterns corresponding to the standard side surface and the number of patterns corresponding to the right lateral shift is compared with the threshold Th7, and the threshold Th7 is compared. If Th7 is exceeded, it is determined in S30 that the photographing position is the side without discriminating between the standard side and the right side shift.

If it is determined in S29 that the photographing position is not the side, in S31, the photographing position is not "front" or "side".
Is determined.

Further, as shown in FIG. 13, for example, even in the case of image data of a special case in which one lung has been resected, the characteristic pattern (010) is added to the set of characteristic patterns in the characteristic pattern storage 5. Then, by comparing the number of characteristic patterns corresponding to the one-lung human body with a threshold value of the number of patterns, it is possible to determine the position of the one-lung human body photographed from the front.

When the photographing position is determined as described above, finally, a signal representing the result of the determination of the photographing position is transmitted to the photographing position determining unit 16.
Is output to the output image processing unit 4.

In the output image processing unit 4, the frame memory 2
Directly captures the original image data f (x, y)
The image data F (x, y) is obtained by performing processes such as gradation conversion and frequency emphasis by a conversion method suitable for the photographing position, and the image data F (x, y) is output to the image output unit 6.

The image output unit 6 records the image data F (x, y) processed by the output image processing unit 4 according to the photographing position in a filing system, reproduces the image data on a CRT,
It is recorded on an X-ray film by a printer. Here, in the image output unit 6, since the image data has been subjected to processing according to the photographing position of the image, the reproduced image can be made a visible image suitable for image interpretation.

<Effects of the Invention> As described above, according to the digital radiographic image photographing position determination apparatus according to the present invention, various image data over a wide range are not affected by the size and positional deviation of the subject in the digital radiographic image data. It is possible to easily and accurately determine the photographing position of the subject from the photographing position, and perform the optimal image processing for the photographing position based on the result of the determination of the photographing position to make the density of the region of interest in the reproduced image uniform. This makes it possible to enhance the medical diagnostic performance based on the radiographic image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a system block diagram showing one embodiment of the present invention, FIG. 3 is a diagram showing how image data is represented in the above embodiment, FIG. FIG. 5 is a diagram showing the state of the projection before the smoothing process in the embodiment, FIGS. 5 and 6 are diagrams for explaining the difference in the characteristic of the signal level distribution depending on the photographing position, and FIG. FIGS. 8 to 13 are diagrams showing the state of detection of the magnitude change pattern based on the projection in the example, and FIGS. 8 to 13 are diagrams for explaining the difference in the magnitude change pattern of the signal level depending on the photographing position, FIGS.
FIG. 15 is a flowchart showing the contents of the photographing posture determination based on the difference in the magnitude change pattern. DESCRIPTION OF SYMBOLS 1 ... Image input part, 2 ... Frame memory, 3 ... Image processing part, 4 ... Output image processing part, 5 ... Feature pattern storage part, 6 ... Image output part, 11 ... Signal thinning part , 12 ...
... Contrast enhancement correction section, 13 ... Projection creation section, 14 ... Smoothing processing section, 15 ... Change pattern detection section, 16 ... Photographing position determination section

────────────────────────────────────────────────── (5) References JP-A-63-262137 (JP, A) JP-A-63-262139 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) A61B 6/00-6/14

Claims (8)

(57) [Claims] 1. A level distribution detecting means for detecting a level distribution of a digital radiation image signal along a predetermined direction of an image, and a signal level of the level distribution detected by the level distribution detecting means and a plurality of signal level thresholds. Compare to each,
A magnitude change pattern detection means for determining a magnitude change pattern of a signal level with respect to each threshold along the predetermined direction of the image; and a number of types of magnitude change patterns for each threshold detected by the magnitude change pattern detection means. And a photographing position discriminating means for discriminating the photographing position of the subject in the digital radiation image signal based on the digital radiation image signal. 2. A photographing position discriminating means for discriminating a photographing position of a subject by comparing a predetermined number of patterns having the same size as a reference magnitude change pattern stored in advance. The digital radiographic image capturing position determining apparatus according to claim 1. 3. The photographing position of a subject is determined by combining a plurality of determinations by comparing the number of specific magnitude change patterns with a predetermined number, wherein the photographing position determining means determines the photographing position of the subject. The digital radiographic image capturing position discriminating apparatus according to claim 1. 4. The apparatus according to claim 1, wherein said level distribution detecting means detects a signal level distribution using a total value or an average value of signal levels of respective pixel rows substantially orthogonal to a predetermined direction of said image for detecting a level distribution. The digital radiographic image capturing position discriminating apparatus according to claim 1, 2 or 3. 5. The method according to claim 1, wherein said level distribution detecting means detects a signal level distribution by directly using a signal level of each pixel row along a predetermined direction of said image for detecting a level distribution. The digital radiographic image capturing position discriminating apparatus according to any one of 2 and 3. 6. A signal thinning means for reducing at least one of the number of pixels of a digital radiographic image and the number of quantization steps of a signal, wherein said level distribution detecting means includes a step of quantizing the number of pixels and a signal by said signal thinning means. The digital radiographic image position determination according to any one of claims 1, 2, 3, 4, and 5, wherein a level distribution is detected based on a digital radiographic image signal in which at least one of the numbers is reduced. apparatus. 7. A digital radiographic image signal comprising a contrast emphasis correction means for performing a correction for enhancing contrast so that the distribution of the density histogram of the digital radiographic image is widened, wherein the level distribution detecting means is corrected by the contrast emphasis correction means. The level distribution is detected based on the obtained digital radiation image signal.
7. The photographing posture discriminating apparatus for digital radiation images according to any one of 4, 5, and 6. 8. A level distribution smoothing means for smoothing a level distribution detected by said level distribution detecting means,
Wherein the magnitude change pattern detecting means obtains a magnitude change pattern based on the level distribution smoothed by the level distribution smoothing means.
8. The digital radiographic image capturing position discriminating apparatus according to any one of 3, 4, 5, 6, and 7.