JP3832974B2 - Irradiation area extraction method, irradiation area extraction apparatus, and computer-readable storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an irradiation area extraction method, an irradiation area extraction apparatus, and a computer-readable storage medium, and is particularly suitable for extracting an irradiation area irradiated with radiation from image data acquired by radiography. It is a thing.
[0002]
[Prior art]
With recent advances in digital technology, a radiation image is converted into a digital image signal, and the digital image signal is processed and displayed on a CRT or the like or printed out. In radiographic imaging, for reasons of humanitarian reasons, in order to prevent scattering from unnecessary areas and prevent reduction of contrast, it is common to perform irradiation squeezing that irradiates only the necessary areas. . In performing image processing, it is common to determine processing parameters from the distribution of density values and perform image processing based on the determined parameters. However, when the irradiation area is not limited, so-called unnecessary information outside the region of interest is used for determination of the image processing parameter, which causes a problem that appropriate image processing cannot be performed.
[0003]
Therefore, it is necessary to extract an irradiation region and determine an image processing parameter from information on only the region of interest. As a method for extracting the irradiation region, for example, an image density value is differentiated and an irradiation end is determined from the value, and as shown in Japanese Examined Patent Publication No. 6-90412, an area of the base field outside the irradiation region is assumed. A method is known in which the base is approximated by a primary approximation formula, and the irradiation end is determined from the difference between the actual density value and the value of the primary approximation formula. However, each of the above-described irradiation end extraction methods is a method that is based on the assumption that there is irradiation squeezing, and in order to use each irradiating end extraction method, it is necessary to determine whether or not there is squeezing of irradiation as preprocessing.
[0004]
As a method for determining the presence or absence of irradiation squeeze, as shown in US Pat. No. 5,091,970, the density average and intermediate value of the center of the image are compared with the average density and intermediate value of the edge of the image. If the density value of the part is below a certain value, there is a method of irradiating with irradiation.
[0005]
[Problems to be solved by the invention]
FIG. 10 is an X-ray image of the lung front. a represents the entire surface of the image, b represents an irradiation region directly hitting the X-ray, and a black portion of the region b is a portion hitting the sensor directly by the X-ray. A is an area used for determining whether or not there is irradiation, for example, in the above-mentioned US Pat. No. 5,091,970.
[0006]
As in the above-mentioned US Pat. No. 5,091,970, the method for determining the presence / absence of irradiation based on whether or not the image edge A in FIG. It is not possible to determine whether For this reason, there is a problem that information on the rough irradiation area is unknown, processing for extracting the irradiation area from all areas must be performed, and calculation time is required. Furthermore, there is a problem that even if the irradiation region is extracted, the rough irradiation region is unknown, and thus the extracted irradiation region cannot be verified.
[0007]
Also, as shown in FIG. 10, when there are few regions where X-rays directly contact the sensor, the density change is larger in the lung periphery than in the irradiation end, and thus the problem of erroneously extracting the irradiation region to the lung periphery, etc. There is.
[0008]
Further, in the method of US Pat. No. 5,091,970, when an imaging region is applied to the edge of the image when no irradiation is performed on the edge of the region image, the area of the imaging region applied to the image edge and the radiation transmittance As a result, the average density at the edge of the image varies. Therefore, there is a problem in that it is erroneously determined that there is irradiation even though irradiation is not performed. In addition, when the irradiation dose is small, there is a problem that there is no difference in density between the center of the image and the edge of the image, and there is a problem of erroneous determination that there is irradiation even though there is no irradiation.
[0009]
The present invention has been made for the purpose of solving the above-described problems, and determines whether or not a designated area in an image is an irradiation area.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an irradiation region extraction method according to the present invention is an irradiation region extraction method for extracting a region irradiated with radiation as an irradiation region from image data acquired by radiography. A first characteristic value calculating step for calculating a first characteristic value representative of the data; and dividing the image data into a plurality of image data areas; and a second characteristic value representing each of the plurality of image data areas. A second characteristic value calculating step for calculating, a second characteristic value representing each of the plurality of image data regions, and the first characteristic value are compared, and a second characteristic value greater than the first characteristic value is shown; A determination step of determining whether or not at least a part of the irradiation region is included in the image data region in which the characteristic value is calculated; and at least a portion of the irradiation region in the determination step among the regions of the image data With reference to the image data area that is determined to include a part of the area, characterized in that it comprises an extraction step of extracting the irradiated region.
[0011]
The computer-readable storage medium according to the present invention is a computer-readable storage medium representative of image data for extracting an irradiation area corresponding to an area irradiated with radiation from image data acquired by radiography. A first characteristic value calculating means for calculating one characteristic value; and a second characteristic value for dividing the image data into a plurality of image data areas and calculating a second characteristic value representing each of the plurality of image data areas. The characteristic value calculating means compares the first characteristic value with a second characteristic value representing each of the plurality of image data areas, and calculates a second characteristic value that is larger than the first characteristic value. Determination means for determining whether or not at least a part of the irradiation area is included in an image data area; and at least of the irradiation area by the determination means among the areas of the image data Referring to the image data area that is determined to contain a region parts and characterized by storing a computer program for functioning as the extraction means for extracting the irradiation region.
[0012]
An irradiation area extraction apparatus according to the present invention is an irradiation area extraction apparatus that extracts an irradiation area corresponding to an area irradiated with radiation from image data acquired by radiography, and represents the image data. A first characteristic value calculating means for calculating one characteristic value; and a second characteristic value for dividing the image data into a plurality of image data areas and calculating a second characteristic value representing each of the plurality of image data areas. The characteristic value calculating means compares the first characteristic value with a second characteristic value representing each of the plurality of image data areas, and calculates a second characteristic value that is larger than the first characteristic value. Determination means for determining whether or not at least a part of the irradiation area is included in the image data area; and at least a part of the irradiation area by the determination means in the image data area. Referring to the image data region determined to include characterized by comprising an extraction means for extracting the irradiation region.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
First, a first embodiment will be described.
FIG. 2 shows an image of a hand that has been X-rayed without squeezing, and a represents the area of the entire image.
FIG. 3 shows a case where the entire image area a is divided into, for example, ten designated areas 1 to 10. The numbers at the bottom of the figure indicate the coordinates.
FIG. 4 shows the relationship between the hand image (region b) that has been X-rayed with irradiation and the designated region in FIG.
FIG. 5 shows a case where the entire image area a is divided into, for example, 50 instruction areas.
FIG. 6 shows the relationship between the lung image (region b) taken by irradiation and the indication region of FIG.
[0017]
FIG. 1 is a flock diagram showing a configuration of an irradiation area determination apparatus according to the first embodiment.
In FIG. 1, 101 is a first characteristic value calculation unit that calculates a first characteristic value from the entire image, 102 is an area instruction unit that indicates a designated area for calculating a second characteristic value, and 103 is an area instruction unit 102. 2nd characteristic value calculation means for calculating the density value of the area instructed as the second characteristic value, 104 is a determination means for determining the presence or absence of an irradiation area in the designated area from the second characteristic value, and 105 is the area The storage unit stores the area information of the instruction unit 102 and the determination result of the determination unit 104 together.
[0018]
Next, the operation of the irradiation area determination apparatus having the above configuration will be described with reference to the flowchart of FIG. Here, for example, the flow of processing for determining whether the designated area is an irradiation area will be described with reference to FIG.
The first characteristic value calculation unit 101 calculates the MAX value of the density of the entire image. The MAX value here may be the upper part of the cumulative histogram of the entire image, for example, the 5% point, or the image density values may be sorted and used as the upper part.
[0019]
Then, the density value d1 represented by the equation (1) is set as the first characteristic value (step S201). Here, ratio is a constant, for example, 0.5.
d1 = MAX × ratio (1)
Next, the area instruction means 102 sequentially designates the designated areas 1 to 10 shown in FIG. 3, and passes the coordinate information of the designated area to the second characteristic value calculation means 103 (step S202).
[0020]
Next, the second characteristic value calculation means 103 calculates the density average value from the designated area as the second characteristic value d2 (step S203). Next, the determination unit 104 compares the magnitude relationship between the first characteristic value d1 and the second characteristic value d2,
d2> d1 (2)
If so, it is determined that the designated region is an irradiation region, otherwise it is determined that it is not an irradiation region (step S204).
[0021]
The storage unit 105 stores the coordinates of the designated area together with the determination result of the determination unit 104 (step S205). If the second characteristic value has been calculated for all the designated areas, the process ends. If not, the process returns to step S202, and the processes of steps S203 to S205 are performed for the other designated areas.
[0022]
As described above, by comparing the first characteristic value with the second characteristic value of the designated area, it is possible to extract the designated area that is the irradiation area.
[0023]
For example, in the case of FIG. 4, the determination unit 104 determines that the irradiation area covers the designated areas 4, 5, 6, and 7. Therefore, it is estimated that the left end portion of the irradiation region is between coordinates 3 and 4, and the right end portion is between coordinates 6 and 7. For this reason, the process for obtaining the left end portion of the irradiation region only needs to be performed between the coordinates 3 and 7, and there is an effect that the calculation time is shortened compared to the process of all the coordinates.
[0024]
Further, when the irradiation region is extracted by some irradiation region extraction method, the left irradiation end portion is in the designated region 4, so that it can be verified that the extraction is performed in the case other than the designated region 4. Furthermore, when it is determined that the extraction is incorrect, another irradiation area extraction method can be used.
[0025]
For example, in the case of FIG. 6, since there are few portions where the X-rays are directly applied to the sensor, the edge around the lung is easily misextracted as the irradiation end. However, according to the present embodiment, it is determined that at least the designated areas 1, 2, 3, and 4 in FIG. Therefore, it is possible to determine erroneous extraction even when the lung edge portion is mistakenly extracted as the irradiation end portion, and a new irradiation region is extracted based on the region information of the designated regions 1, 2, 3, and 4. It is possible.
[0026]
Although the maximum density value of the entire image is used as the first characteristic value here, an average value, an intermediate value, or the like of the entire image may be used. Further, the average value and the intermediate value of the designated area may be used as the second characteristic value.
[0027]
As described above, according to the first embodiment, by performing the irradiation area extraction process with reference to the presence or absence of the irradiation area of the designated area, it is not necessary to process the entire area, and the calculation time can be reduced. There is.
Also, by referring to the presence or absence of the irradiation area of the designated area, the extraction result of the irradiation area extraction process can be verified, and if the irradiation area extraction is incorrect, the irradiation area extraction can be performed again, Irradiation area extraction also has the effect of increasing accuracy.
Furthermore, in the case of erroneous extraction, other irradiation area extraction methods can be used, and combining a plurality of irradiation area methods has the effect of further improving the accuracy of irradiation area extraction.
[0028]
Next, a second embodiment will be described.
In the present embodiment, the characteristic value calculation method of the second characteristic value calculation unit 103 in FIG. 1 and the determination method of the determination unit 104 are different from those of the first embodiment. Here, the flow of processing for determining the presence or absence of an irradiation area will be described with reference to FIGS.
First, the first characteristic value calculation unit 101 calculates the MAX value of the entire image. The MAX value here may be the upper part of the cumulative histogram of the entire image, for example, the 5% point, or the image density values may be sorted and used as the upper part (step S201).
[0029]
Next, the area instruction means 102 sequentially designates the designated areas 1 to 10 shown in FIG. 3, and passes the coordinate information of the designated area to the second characteristic value calculation means 103 (step S202).
The second characteristic value calculation unit 103 calculates the appearance frequency of a certain value of the MAX value calculated by the first characteristic value calculation unit 101 from the specified area, for example, a density value of 90% or more (step S203).
[0030]
Next, when the appearance frequency calculated by the second characteristic value calculation unit 103 is larger than a certain value Th1 (for example, Th1 = 0.05), the determination unit 104 determines the designated region as an irradiation region, and is equal to or less than Th1. If so, it is determined that it is not an irradiation region (step S204). The storage unit 105 stores the coordinates of the designated area together with the determination result of the determination unit 104 (step S205). If the second characteristic value has been calculated for all the designated areas, the process ends. If not, the process returns to step S202, and the processes of steps S203 to S205 are performed on the other designated areas.
[0031]
As described above, according to the second embodiment, even when a metal piece is contained in the indication area, the appearance frequency is used instead of the concentration average value as the second characteristic value. Stable determination can be performed without being affected by the density value of the piece. Further, since the appearance frequency is used, stable determination can be performed without being affected by high density or low density noise.
[0032]
Next, a third embodiment will be described.
FIG. 8 is a flowchart showing the flow of the first characteristic value calculation processing calculated by the first characteristic value calculation means 101 in the first and second embodiments. FIG. 9 shows a density value histogram of the entire image, where the horizontal axis indicates density values and the vertical axis indicates appearance frequency.
[0033]
Next, the operation will be described according to the flow of FIG.
First, a histogram as shown in FIG. 9 is created (step 401). Next, the density value Th3 indicating the density lower limit of the missing area (the area where the X-ray directly hits the sensor) is extracted from the created histogram. Here, the most depressed point of the first recess from the high density value side on the histogram of FIG. 9 is set to Th3 (step 402). This Th3 is taken as the value of MAX calculated by the first characteristic value calculation means 101. Subsequent processing is performed in the same manner as in the first and second embodiments.
[0034]
As described above, according to the third embodiment, when there is a void area, the void density can be calculated stably, and the characteristic value calculated in the void density and the specified area can be calculated. By using this, there is an effect that a designated area which is a through area can be stably extracted.
[0035]
Next, the storage medium according to the present invention will be described.
When the system comprising the blocks shown in FIG. 1 is constituted by a computer system including a memory such as a CPU and a ROM, the memory constitutes a storage medium according to the present invention. This storage medium stores a program for executing the processing procedure for controlling the operation described above with reference to the flowcharts of FIGS.
[0036]
As the storage medium, a semiconductor memory such as ROM or RAM, an optical disk, a magneto-optical disk, a magnetic medium, or the like may be used. These may be a CD-ROM, a floppy disk, a magnetic medium, a magnetic card, a nonvolatile memory card, or the like. It may be configured and used.
[0037]
Therefore, the storage medium is used in other systems and apparatuses other than the systems and apparatuses shown in the above drawings, and the system or computer reads out and executes the program code stored in the storage medium as described above. Functions equivalent to those in each embodiment can be realized, and equivalent effects can be obtained, and the object of the present invention can be achieved.
[0038]
Also, when the OS running on the computer performs part or all of the processing, or the program code read from the storage medium is an extension function board inserted in the computer or an extension connected to the computer Even when the CPU or the like provided in the extended function board or the extended function unit performs part or all of the processing based on the instruction of the program code after being written in the memory provided in the functional unit, While equivalent functions can be realized, equivalent effects can be obtained, and the object of the present invention can be achieved.
[0039]
【The invention's effect】
According to the present invention, when the second characteristic value representing the plurality of image data areas into which the image data is divided is larger than the first characteristic value representing the image data, the second characteristic value is calculated. It is determined whether or not at least a part of the irradiation area is included in the image data area. Then, the irradiation area is extracted with reference to an image data area determined to include at least a part of the irradiation area. Thereby, it is not necessary to perform the process for extracting the irradiation region for the entire region of the image data, and the calculation time can be shortened.
[0040]
Further, since it is determined whether or not the divided image data area is an irradiation area, the extraction result of the irradiation area can be verified, and if the extraction of the irradiation area is wrong, the extraction of the irradiation area is performed again. It is possible to improve the extraction accuracy of the irradiation area.
Furthermore, in the case of erroneous extraction, other irradiation area extraction methods can be used, and combining a plurality of irradiation area extraction methods has the effect of further improving the accuracy of irradiation area extraction.
[0041]
According to another feature of the invention, since the appearance frequency of the first characteristic value representing the image data is used as the second characteristic value, a metal piece is included in the image data area. Even in this case, stable determination can be performed without being affected by the concentration value of the metal piece. Further, since the appearance frequency is used, stable determination can be performed without being affected by high density or low density noise.
[0042]
According to another feature of the present invention, since the first characteristic value is obtained from the shape of the histogram of the pixel values of the image data, there is an effect that a void area can be stably extracted.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an irradiation area determination apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing an image of a hand taken by X-ray imaging without squeezing irradiation;
FIG. 3 is a configuration diagram showing a designated area.
FIG. 4 is a configuration diagram showing an image of a hand that has been X-rayed with a designated area and irradiation.
FIG. 5 is a configuration diagram showing a designated area.
FIG. 6 is a configuration diagram illustrating a designated region and an image of a lung that has been X-rayed with irradiation.
FIG. 7 is a flowchart showing a processing procedure according to the first and second embodiments.
FIG. 8 is a flowchart showing a processing procedure according to the third embodiment.
FIG. 9 is a characteristic diagram showing a histogram of density values of the entire image.
FIG. 10 is a configuration diagram showing an image of a lung taken by X-ray imaging with irradiation narrowing.
[Explanation of symbols]
101 First characteristic value calculation means 102 Region instruction means 103 Second characteristic value calculation means 104 Determination means 105 Storage means

Claims (9)

An irradiation region extraction method for extracting a region irradiated with radiation as an irradiation region from image data acquired by radiography,
A first characteristic value calculating step of calculating a first characteristic value representing the image data;
A second characteristic value calculating step of dividing the image data into a plurality of image data areas and calculating a second characteristic value representing each of the plurality of image data areas;
The second characteristic value representing each of the plurality of image data areas is compared with the first characteristic value, and the second characteristic value indicating a value larger than the first characteristic value is calculated in the image data area. A determination step of determining whether or not at least a part of the irradiation region is included;
An extraction step of extracting the irradiation region with reference to the image data region determined to include at least a part of the irradiation region in the determination step among the regions of the image data. Irradiation region extraction method. The second characteristic value is an appearance frequency of the first characteristic value in each of the plurality of image data regions,
2. The determination step according to claim 1, wherein the determination step determines that the image data area in which the second characteristic value is calculated is an irradiation area when the second characteristic value is larger than a predetermined value. Irradiation area extraction method.   3. The irradiation region extraction method according to claim 1, wherein the first characteristic value is any one of a value determined from a maximum value of pixel values in the image data region, an average value, and an intermediate value. .   The irradiation area extraction method according to claim 1, wherein the second characteristic value is one of an average value and an intermediate value of pixel values for each of the plurality of image data areas.   5. The first characteristic value calculating step creates a histogram of pixel values of the entire image data, and obtains the first characteristic value from the shape of the created histogram. 2. The irradiation area extraction method according to item 1.   The irradiation area extraction method according to claim 5, wherein the first characteristic value is the most depressed point of the first recess from the high pixel value side of the histogram.   The irradiation region extraction method according to claim 1, wherein the plurality of image data regions are regions obtained by dividing the entire image data into rectangular shapes. In order to extract an irradiation area corresponding to an area irradiated with radiation from image data acquired by radiography, a computer is used.
First characteristic value calculating means for calculating a first characteristic value representing the image data;
A second characteristic value calculating means for dividing the image data into a plurality of image data areas and calculating a second characteristic value representing each of the plurality of image data areas;
The second characteristic value representing each of the plurality of image data areas is compared with the first characteristic value, and the second characteristic value indicating a value larger than the first characteristic value is calculated in the image data area. Determining means for determining whether or not at least a part of the irradiation area is included;
A computer program for functioning as extraction means for extracting the irradiation area with reference to the image data area determined by the determination means to include at least a part of the irradiation area among the image data areas A computer-readable storage medium characterized by storing the above. An irradiation area extraction device that extracts an irradiation area corresponding to an area irradiated with radiation from image data acquired by radiography,
First characteristic value calculating means for calculating a first characteristic value representing the image data;
A second characteristic value calculating means for dividing the image data into a plurality of image data areas and calculating a second characteristic value representing each of the plurality of image data areas;
The second characteristic value representing each of the plurality of image data areas is compared with the first characteristic value, and the second characteristic value indicating a value larger than the first characteristic value is calculated in the image data area. Determining means for determining whether or not at least a part of the irradiation area is included;
Extracting means for extracting the irradiation area with reference to the image data area determined to include at least a part of the irradiation area by the determination means in the image data area. An irradiation area extraction apparatus.

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