Patent Description:
In general, an object of interest, such as a breast cancer, in the breast has been diagnosed on the basis of a radiographic image of the breast of a subject captured by a so-called mammography apparatus. However, in the case of the breast with a high percentage of mammary glands, an image of the object of interest in the radiographic image may be hidden by the mammary glands and may be difficult to see. Therefore, a technique has been known which derives the percentage of the mammary glands. For example, <CIT> discloses a technique that estimates a fat image obtained in a case in which the entire breast is assumed to be composed of only the fat tissues and derives the percentage of the mammary glands, using the pixel value of the fat image and an attenuation coefficient of radiation.

<CIT> discloses an image processing apparatus adapted to acquire plural radiographic images of the same breast which have been captured in plural different states of compression of the breast. A derivation unit derives a percentage of mammary glands of a breast image on the basis of an amount of incident radiation. Such amount is derived from a value of a fat tissue pixel in the radiographic image. To this end, a fatty reference point is found in the image.

<CIT> discloses a system for calculating a breast density on the basis of a single digital mammographic image. Threshold values may be obtained for distinguishing fatty breast tissue as background.

According to a first aspect of the present invention, there is provided an image processing apparatus as set out in independent claim <NUM>. According to further aspects of the invention, there is provided an image processing method as set out in independent claim <NUM>, and a non-transitory recording medium recording an image processing program as set out in independent claim <NUM>.

In the technique disclosed in <CIT>, the value of a fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only the fat tissues in the radiographic image is used. However, for example, in some cases, the fat tissue pixel is not included in the radiographic image according to the compressed state of the breast which varies depending on an imaging direction. In this case, there is room for improvement in the technique disclosed in <CIT>.

The present disclosure has been made in view of the above-mentioned problems and an object of the present disclosure is to provide an image processing apparatus, an image processing method, and an image processing program that can derive the percentage of the mammary glands with high accuracy even in a case in which a fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only fat tissues is not included in a radiographic image of the breast.

In order to achieve the object, according to a first aspect of the present disclosure, there is provided an image processing apparatus comprising: an acquisition unit that acquires a plurality of radiographic images of the same breast which have captured in a plurality of different states related to compression of the breast; and a derivation unit that derives, on the basis of an amount of incident radiation derived from a value of a fat tissue pixel in a radiographic image in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only fat tissues is included in a breast image among the plurality of radiographic images acquired by the acquisition unit, a percentage of mammary glands of a breast image in a radiographic image different from the radiographic image used to derive the amount of incident radiation.

According to a second aspect of the present disclosure, in the image processing apparatus according to the first aspect, the derivation unit may derive the percentage of the mammary glands for each pixel.

According to a third aspect of the present disclosure, in the image processing apparatus according to the first or second aspect, the plurality of radiographic images may include a plurality of radiographic images in which compression directions of the breast are different from each other.

According to a fourth aspect of the present disclosure, in the image processing apparatus according to the first or second aspect, the plurality of radiographic images may include a radiographic image captured in a craniocaudal direction and a radiographic image captured in a mediolateral-oblique direction.

According to a fifth aspect of the present disclosure, in the image processing apparatus according to any one of the first to fourth aspects, the acquisition unit may further acquire information indicating a thickness of each breast in the capture of the plurality of radiographic images and the derivation unit may derive the percentage of the mammary glands on the basis of a difference between the thicknesses of the breast.

According to a sixth aspect of the present disclosure, in the image processing apparatus according to any one of the first to fourth aspects, the derivation unit may derive the percentage of the mammary glands on the basis of a ratio of an amount of incident radiation derived on the basis of a pixel value of a direct region corresponding to radiation which is directly emitted without passing through the breast in the radiographic image including the fat tissue pixel and an amount of incident radiation derived on the basis of a pixel value of a direct region corresponding to radiation which is directly emitted without passing through the breast in the radiographic image different from the radiographic image used to derive the amount of incident radiation.

According to a seventh aspect of the present disclosure, in the image processing apparatus according to any one of the first to sixth aspects, in a case in which the plurality of radiographic images do not include the radiographic image including the fat tissue pixel, the derivation unit may derive the percentage of the mammary glands on the basis of a value of a mammary gland tissue pixel obtained by a portion of the breast which is estimated to be composed of only mammary gland tissues.

According to an eighth aspect of the present disclosure, the image processing apparatus according to any one of the first to sixth aspects may further comprise a determination unit that determines a type of the breast on the basis of the plurality of radiographic images. In a case in which the type of the breast determined by the determination unit is a type predetermined to be a breast with a relatively high mammary gland density, the derivation unit may derive the percentage of the mammary glands on the basis of a value of a mammary gland tissue pixel obtained by a portion of the breast which is estimated to be composed of only mammary gland tissues.

According to a ninth aspect of the present disclosure, there is provided an image processing method comprising: acquiring a plurality of radiographic images of the same breast which have captured in a plurality of different states related to compression of the breast; and deriving, on the basis of an amount of incident radiation derived from a value of a fat tissue pixel in a radiographic image in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only fat tissues is included in a breast image among the acquired plurality of radiographic images, a percentage of mammary glands of a breast image in a radiographic image different from the radiographic image used to derive the amount of incident radiation.

According to a tenth aspect of the present disclosure, there is provided an image processing program that causes a computer to perform: acquiring a plurality of radiographic images of the same breast which have captured in a plurality of different states related to compression of the breast; and deriving, on the basis of an amount of incident radiation derived from a value of a fat tissue pixel in a radiographic image in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only fat tissues is included in a breast image among the acquired plurality of radiographic images, a percentage of mammary glands of a breast image in a radiographic image different from the radiographic image used to derive the amount of incident radiation.

According to the present disclosure, it is possible to derive the percentage of the mammary glands with high accuracy even in a case in which a fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only fat tissues is not included in a radiographic image of the breast.

Exemplary Embodiments of the present disclosure will be described in detail with reference to the following figures, wherein:.

Hereinafter, embodiments of the disclosure will be described in detail with reference to the drawings. The embodiments do not limit the invention.

First, an example of the overall configuration of a radiography system according to this embodiment will be described. <FIG> is a configuration diagram illustrating an example of the overall configuration of a radiography system <NUM> according to this embodiment.

The radiography system <NUM> according to this embodiment has a function of capturing radiographic images in response to an operation of a user, such as a doctor or a radiology technician, on the basis of a command (imaging order) input from an external system (for example, a radiology information system (RIS)) through a console <NUM>.

As illustrated in <FIG>, the radiography system <NUM> according to this embodiment comprises the console <NUM> and a mammography apparatus <NUM>. <FIG> is a block diagram illustrating an example of the configuration of the console <NUM> and the mammography apparatus <NUM> according to this embodiment.

The console <NUM> according to this embodiment has a function of controlling the mammography apparatus <NUM> using, for example, an imaging order or various kinds of information acquired from an external system through a wireless communication local area network (LAN). The console <NUM> according to this embodiment is an example of an image processing apparatus according to the present disclosure.

For example, the console <NUM> according to this embodiment is a server computer. As illustrated in <FIG>, the console <NUM> includes a control unit <NUM>, a storage unit <NUM>, an interface (I/F) unit <NUM>, a display unit <NUM>, and an operation unit <NUM>. The control unit <NUM>, the storage unit <NUM>, the I/F unit <NUM>, the display unit <NUM>, and the operation unit <NUM> are connected to each other through a bus <NUM>, such as a system bus or a control bus, such that they can transmit and receive various kinds of information.

The control unit <NUM> according to this embodiment controls the overall operation of the console <NUM>. The control unit <NUM> according to this embodiment includes a central processing unit (CPU) 40A, a read only memory (ROM) 40B, and a random access memory (RAM) 40C. For example, various programs including a mammary gland percentage derivation processing program (which will be described below) executed by the CPU 40A are stored in the ROM 40B in advance. The RAM 40C temporarily stores various kinds of data.

For example, the image data of a radiographic image captured by the mammography apparatus <NUM> and various other kinds of information are stored in the storage unit <NUM>. Examples of the storage unit <NUM> include a hard disk drive (HDD) and a solid state drive (SSD). The I/F unit <NUM> transmits and receives various kinds of information to and from the mammography apparatus <NUM> or external systems, such as an RIS and a picture archiving and communication system (PACS), using at least one of wireless communication or wired communication.

The display unit <NUM> displays, for example, information related to imaging and the captured radiographic image. The operation unit <NUM> is used by a user to input, for example, a command to capture a radiographic image and a command related to image processing for the captured radiographic image. For example, the operation unit <NUM> may have the form of a keyboard or various types of switches or the form of a touch panel integrated with the display unit <NUM>.

The mammography apparatus <NUM> according to this embodiment is an apparatus that irradiates the breast of a subject, which is an object, with radiation X (X-rays) to capture the radiographic image of the breast. As illustrated in <FIG>, the mammography apparatus <NUM> comprises an imaging unit <NUM> and a base portion <NUM> that supports the imaging unit <NUM>.

The imaging unit <NUM> comprises an imaging table <NUM> having a planar imaging surface <NUM> that come into contact with the breast of the subject, a compression plate <NUM> that compresses the breast against the imaging surface <NUM> of the imaging table <NUM>, and a holding portion <NUM> that supports the imaging table <NUM> and the compression plate <NUM>. In addition, a member that transmits the radiation X is used as the compression plate <NUM>. In addition, the imaging unit <NUM> according to this embodiment is rotated by an imaging unit rotating unit <NUM> in a state in which the imaging unit <NUM> holds the imaging table <NUM>, which will be described in detail below.

The holding portion <NUM> supports the imaging table <NUM> and a radiation source <NUM> such that the imaging surface <NUM> and the radiation source <NUM> are separated by a predetermined distance. In addition, the holding portion <NUM> holds the compression plate <NUM> such that the compression plate <NUM> is slid to change the distance between the compression plate <NUM> and the imaging surface <NUM>.

In a case in which the mammography apparatus <NUM> captures the radiographic image of the breast of the subject, for example, a user positions the subject and the breast placed on the imaging surface <NUM> of the imaging table <NUM> is compressed between the compression plate <NUM> and the imaging surface <NUM> and is fixed.

A radiation detector <NUM> that detects the radiation X transmitted through the breast and the imaging surface <NUM> is provided in the imaging table <NUM>. A radiographic image is generated on the basis of the radiation X detected by the radiation detector <NUM>. However, the type of radiation detector <NUM> according to this embodiment is not particularly limited. For example, the radiation detector <NUM> may be an indirect-conversion-type radiation detector that converts the radiation X into light and converts the converted light into charge or a direct-conversion-type radiation detector that directly converts the radiation X into charge. In this embodiment, image data indicating the radiographic image output from the radiation detector <NUM> of the mammography apparatus <NUM> is transmitted to the console <NUM>.

The mammography apparatus <NUM> according to this embodiment can perform both craniocaudal (CC) imaging in which an imaging direction is a craniocaudal direction and mediolateral-oblique (MLO) imaging in which the imaging direction is a mediolateral-oblique direction for the breast. In the following description, in radiography, the position of the radiation source <NUM> in a case in which the radiation source <NUM> emits the radiation X to the imaging table <NUM> is referred to as an "imaging position".

In a case in which the CC imaging is performed, the imaging table <NUM> is adjusted to a state in which the imaging surface <NUM> faces the upper side (the head of the subject) of the mammography apparatus <NUM>, that is, a state in which a normal direction to the imaging surface <NUM> is vertical. In this case, the position of the radiation source <NUM> is adjusted to an imaging position where the radiation source <NUM> faces the imaging surface <NUM> of the imaging table <NUM>. Specifically, the position of the radiation source <NUM> is adjusted to an imaging position where the radiation source <NUM> is vertical with respect to a normal line CL (see <FIG> and <FIG>) to the imaging surface <NUM> (that is, the angle formed between the normal line CL (see <FIG> and <FIG>) and the radiation source <NUM> is <NUM> degrees). Therefore, the radiation X is emitted from the radiation source <NUM> to the breast in a direction from the head to the foot of the subject and the CC imaging is performed.

In a case in which the MLO imaging is performed, the imaging unit rotating unit <NUM> adjusts the position of the imaging table <NUM> to a state in which the imaging surface <NUM> is rotated to a predetermined angle in the range that is equal to or greater than <NUM> degrees and less than <NUM> degrees, as compared to the case in which the CC imaging is performed. Specifically, in a case in which the image of the left breast of the subject is captured, for example, as represented by a dashed line in <FIG>, the imaging unit rotating unit <NUM> rotates the imaging table <NUM> such that the imaging surface <NUM> is inclined to the right. In addition, the image of the right breast of the subject is captured, as represented by a dashed line in <FIG>, the imaging unit rotating unit <NUM> rotates the imaging table <NUM> such that the imaging surface <NUM> is inclined to the left. Then, the position of the radiation source <NUM> is adjusted to an imaging position where the radiation source <NUM> faces the imaging surface <NUM> of the imaging table <NUM>. Therefore, the radiation X is emitted from the radiation source <NUM> to the breast in a direction from the center to the outside of the body of the subject (from a part between the breasts to the arm of the subject) and the MLO imaging is performed.

As such, in the mammography apparatus <NUM> according to this embodiment, in both the CC imaging and the MLO imaging, the radiation source <NUM> faces the imaging surface <NUM> at the imaging position. Hereinafter, a radiographic image obtained by the CC imaging is referred to as a "CC image" and a radiographic image obtained by the MLO imaging is referred to as an "MLO image". In addition, in a case in which the CC image and the MLO images are generically referred to, they are simply referred to as "radiographic images".

As illustrated in <FIG>, the mammography apparatus <NUM> according to this embodiment comprises the radiation detector <NUM>, the imaging unit rotating unit <NUM>, a radiation emitting unit <NUM> including the radiation source <NUM>, a control unit <NUM>, a storage unit <NUM>, an I/F unit <NUM>, and an operation panel <NUM>. The radiation detector <NUM>, the imaging unit rotating unit <NUM>, the radiation emitting unit <NUM>, the control unit <NUM>, the storage unit <NUM>, the I/F unit <NUM>, and the operation panel <NUM> are connected to each other through a bus <NUM>, such as a system bus or a control bus, such that they can transmit and receive various kinds of information.

The control unit <NUM> according to this embodiment controls the overall operation of the mammography apparatus <NUM>. In addition, in a case in which a radiographic image is captured, the control unit <NUM> according to this embodiment controls the radiation detector <NUM> and the radiation emitting unit <NUM>. The control unit <NUM> according to this embodiment comprises a CPU 30A, a ROM 30B, and a RAM 30C. For example, various programs including a program for controlling the capture of a radiographic image which are executed by the CPU 30A are stored in the ROM 30B in advance. The RAM 30C temporarily stores various kinds of data.

For example, the image data of the radiographic image captured by the radiation detector <NUM> and various other kinds of information are stored in the storage unit <NUM>. Examples of the storage unit <NUM> include an HDD and an SSD. The I/F unit <NUM> transmits and receives various kinds of information to and from the console <NUM> using wireless communication or wired communication. For example, the operation panel <NUM> is provided as a plurality of switches in the imaging table <NUM> of the mammography apparatus <NUM>. In addition, the operation panel <NUM> may be provided as a touch panel.

Next, the operation of the radiography system <NUM> according to this embodiment will be described. <FIG> is a flowchart illustrating an example of the flow of an imaging operation of capturing the radiographic image of the breast of the subject in the entire radiography system <NUM> according to this embodiment.

In Step S10 illustrated in <FIG>, the mammography apparatus <NUM> performs the CC imaging in response to a command input from the user through the console <NUM>. In a case in which the user positions the subject, the mammography apparatus <NUM> starts a radiography operation in response to a command from the user. <FIG> is a flowchart illustrating an example of the flow of the radiography operation in the mammography apparatus <NUM> according to this embodiment.

In Step S100 illustrated in <FIG>, the control unit <NUM> compresses the breast placed on the imaging surface <NUM> of the imaging table <NUM> with the compression plate <NUM>.

In a case in which the breast is compressed and fixed by the compression plate <NUM>, in Step S102, the control unit <NUM> acquires the height of the compression plate <NUM>, specifically, the distance between the imaging surface <NUM> and the compression plate <NUM>. A method for acquiring the height of the compression plate <NUM> in the control unit <NUM> is not particularly limited. For example, the control unit may detect the amount of movement of the compression plate <NUM> from a predetermined initial position in order to compress the breast and acquire the height of the compression plate <NUM> on the basis of the initial position and the amount of movement. In the radiography system <NUM> according to this embodiment, the height of the compression plate <NUM> in imaging is regarded as the thickness of the breast in imaging.

Then, in Step S104, the control unit <NUM> directs the radiation source <NUM> to irradiate the breast of the subject with the radiation X in response to a command from the user and directs the radiation detector <NUM> to capture the radiographic image of the breast. In addition, the image data of the radiographic image captured by the radiation detector <NUM> is transmitted to the console <NUM> in a state in which it is associated with information indicating the height of the compression plate <NUM> at a predetermined time, such as the time immediately after the imaging ends or the time when image data is received from the console <NUM>.

Then, in Step S106, the control unit <NUM> releases the compression of the breast by the compression plate <NUM>. Specifically, the control unit <NUM> moves the compression plate <NUM> in a direction in which the compression plate <NUM> becomes far away from the imaging table <NUM> (a direction in which the compression plate <NUM> becomes close to the radiation source <NUM>) to release the compression of the breast. The radiography operation of the mammography apparatus <NUM> is ended by the end of this step.

In a case in which the CC imaging in Step S10 (see <FIG>) ends in this way, in Step S12, the mammography apparatus <NUM> performs the MLO imaging in response to a command from the console <NUM>. In a case in which the MLO imaging is performed following the CC imaging, in the mammography apparatus <NUM>, the imaging unit rotating unit <NUM> rotates the imaging unit <NUM> as described above (see <FIG> and <FIG>).

Then, in a case in which the user positions the subject, the mammography apparatus <NUM> performs the radiography operation to capture a radiographic image (MLO image) of the breast of the subject as described above with reference to <FIG>.

In a case in which the mammography apparatus <NUM> captures the CC image and the MLO image in this way, in Step S14, the console <NUM> performs a mammary gland percentage derivation process, whose example will be described with reference to <FIG>, to derive the percentage of the mammary glands of the breast from the radiographic image. Then, the imaging operation in the entire radiography system <NUM> ends.

As such, the console <NUM> according to this embodiment has a function of deriving the percentage of the mammary glands of the breast from the radiographic image of the breast. Here, the principle of deriving the percentage of the mammary glands of the breast from the radiographic image will be described. The percentage of the mammary glands means the volume ratio of the mammary gland tissues to the breast tissues. The percentage of the mammary glands indicates the percentage of the mammary glands in a thickness direction of the breast which is the emission direction of the radiation X. In a case in which there are no mammary glands and only fat is present, the percentage of the mammary glands is <NUM>. As the density of the mammary glands becomes higher, the percentage of the mammary glands becomes higher.

As illustrated in <FIG>, since the radiation X passes through the breast which is an object W and is attenuated, the amount of radiation reaching the radiation detector <NUM> (hereinafter, referred to as "the amount of incident radiation") varies. In <FIG>, (A) schematically illustrates a case in which the radiation X emitted from the radiation source <NUM> directly reaches the radiation detector <NUM> without passing through the breast and (B) schematically illustrates a case in which the radiation X emitted from the radiation source <NUM> passes through the breast and reaches the radiation detector <NUM>. A difference ((A)-(B)) between the amount of incident radiation in the case of (A) and the amount of incident radiation in the case of (B) is equal to the attenuation of the radiation X by the breast. The attenuation of the radiation X by the breast is determined by the thickness T of the breast and the composition (the percentage R of the mammary glands) of the breast. In a case in which the tissues of the breast include the mammary gland tissues and fat tissues, specifically, the attenuation ((A)-(B)) by the breast is derived by the following Expression (<NUM>). In the following Expression (<NUM>), R indicates the percentage (a numerical value in the range of <NUM> to <NUM>) of the mammary glands.

In the above-mentioned Expression (<NUM>), µa × (<NUM> - R) × T indicates the attenuation of the radiation X by the fat tissues.

In addition, µg × R × T indicates the attenuation of the radiation X by the mammary gland tissues.

The percentage R of the mammary glands is derived for each pixel of the radiographic image (breast image) by the following Expression (<NUM>) from the above-mentioned Expression (<NUM>).

In the above-mentioned Expression (<NUM>), I<NUM> is the amount of incident radiation on a direct region (so-called directly irradiated region) corresponding to the radiation X that is directly emitted without passing through the breast in the radiographic image and I<NUM> is the amount of incident radiation on a breast region.

The percentage R of the mammary glands derived for each pixel by the above-mentioned Expression (<NUM>) is integrated in the entire breast image (breast region) of the radiographic image to derive the volume of the mammary glands in the entire breast and the percentage of the mammary glands with respect to the volume of the entire breast.

For example, the method disclosed in <CIT> is known as the method for deriving the percentage of the mammary glands for each pixel of the breast image. In the method disclosed in <CIT>, a fat image A obtained in a case in which it is assumed that the entire breast is composed of only the fat tissues is estimated in order to derive the percentage of the mammary glands from only information obtained from the radiographic image. Since the following Expression (<NUM>) is obtained for the fat image A, the percentage of the mammary glands is derived by the following Expression (<NUM>) obtained by removing the thickness T of the breast from the above-mentioned Expression (<NUM>) using the following Expression (<NUM>). <MAT> <MAT>.

The above-mentioned method uses the values of the fat tissue pixels obtained by a portion of the breast which is estimated to be composed of only the fat tissues from the breast image of the radiographic image of the breast. However, in some cases, the fat tissue pixel is not included in the breast image. For the type of breast, a fatty type, a mammary gland scattered type, a non-uniform high-concentration type, and a high-concentration type are generally known, which are described in the mammary gland density classification of the mammographic quality control manual. Among these types, in the non-uniform high-concentration type and the high-concentration type into which the breast with a relatively high mammary gland density is classified, that is, in a so-called dense breast, the fat tissue pixels have a higher tendency not to be included in the breast image than those in other types. In a case in which the fat tissue pixel is not included in the breast image and the above-mentioned method is applied, there is a concern that the accuracy of deriving the percentage of the mammary glands will be reduced.

Of the CC image and the MLO image, in the CC image, the fat tissue pixels have a higher tendency not to be included in the breast image than those in the MLO image. The method for compressing the breast varies depending on the type of imaging as described above with reference to <FIG> and <FIG>. Therefore, as illustrated in <FIG>, the appearances of the breast, that is, a breast image <NUM>CC and a breast image <NUM>MLO are different in a CC image <NUM>CC and an MLO image <NUM>MLO. For example, in the high-concentration-type breast, in many cases, the mammary gland tissues are included in the breast image <NUM>CC of the CC image <NUM>CC as a whole. In contrast, in many cases, the fat tissues are included in a portion in the vicinity of a boundary <NUM> between the breast and the pectoralis major in the breast image <NUM>MLO of the MLO image <NUM>MLO.

Therefore, in a case in which the fat tissue pixel is not included in the breast image of the CC image, the console <NUM> according to this embodiment derives the percentage of the mammary glands in the CC image using the analysis result of the MLO image. Then, the console <NUM> according to this embodiment converts the value of the fat tissue pixel included in the breast image of the MLO image into the value of the fat tissue pixel estimated to be included in the CC image. Specifically, the console <NUM> converts the value AMLO of the fat tissue pixel included in the breast image of the MLO image into the value ACC of the fat tissue pixel estimated to be included in the CC image, using the following Expression (<NUM>).

In the above-mentioned Expression (<NUM>), I0CC is the amount of incident radiation on the direct region of the CC image, I0MLO is the amount of incident radiation on the direct region of the MLO image, TCC is the thickness of the breast in the CC imaging, and TMLO is the thickness of the breast in the MLO imaging.

In the above-mentioned Expression (<NUM>), conversion is performed using the thickness of the breast. An error in the thickness of the breast acquired in imaging varies depending on, for example, the type of the compression plate <NUM>, the thickness of the compression plate <NUM>, and compression force. However, in a case in which the breast is the same, for example, the type of the compression plate <NUM>, the thickness of the compression plate <NUM>, and compression force may be the same in the CC imaging and the MLO imaging. An error in the thickness of the breast in the CC imaging is considered to be equal to an error in the thickness of the breast in the MLO imaging. Therefore, it is considered that the difference between the thickness TCC of the breast and the thickness TMLO of the breast in the above-mentioned Expression (<NUM>) does not include an error and is close to a true value.

Next, the mammary gland percentage derivation process performed by the console <NUM> will be described with reference to <FIG> is a flowchart illustrating an example of the flow of the mammary gland percentage derivation process performed by the control unit <NUM> of the console <NUM> according to this embodiment. In addition, for example, in the mammary gland percentage derivation process according to this embodiment, the high-concentration-type breast is used as the breast with a relatively high mammary gland density.

For example, in a case in which the mammography apparatus <NUM> ends the MLO imaging (Step S12 in <FIG>), in the console <NUM> according to this embodiment, the CPU 40A of the control unit <NUM> executes a mammary gland percentage derivation processing program stored in the ROM 40B to perform the mammary gland percentage derivation process illustrated in <FIG>. In a case in which the mammary gland percentage derivation process is performed, the control unit <NUM> functions as an example of an acquisition unit, a derivation unit, and a determination unit according to the present disclosure.

As illustrated in <FIG>, in Step S200, the control unit <NUM> acquires the CC image and the height of the compression plate <NUM>. Specifically, the control unit <NUM> acquires image data of the CC image and the height of the compression plate <NUM> associated with the image data of the CC image. In addition, the acquisition destination of the CC image is not particularly limited as long as it is, for example, a device in which a desired CC image is stored and may be, for example, any one of the mammography apparatus <NUM> or the storage unit <NUM> of the host apparatus.

Then, in Step S202, the control unit <NUM> determines whether the fat tissue pixel is included in the breast image of the CC image. The term "fat tissue pixel" is a pixel corresponding to a portion of the breast which is estimated to be composed of only the fat tissues. For example, the "fat tissue pixel" may be a pixel corresponding to a portion of the breast in which the percentage of the fat tissues is higher than that of at least the mammary gland tissues and is greater than a predetermined threshold value for regarding a portion of the breast as being composed of only the fat tissues.

In a case in which the fat tissue pixel is included in the breast image, the determination result in Step S202 is "Yes" and the control unit <NUM> proceeds to Step S204. In Step S204, the control unit <NUM> derives the percentage R of the mammary glands on the basis of the value of the fat tissue pixel in the CC image, using the above-mentioned Expression (<NUM>), and proceeds to Step S218. In this embodiment, the percentage of the mammary glands in the entire breast is derived. However, the invention is not limited to this embodiment. For example, the percentage of the mammary glands may be derived in a portion, such as a portion in which the density of the mammary glands seems to be high or a portion in which the density of the mammary glands seems to be low.

On the other hand, in a case in which no fat tissue pixels are included in the breast image of the CC image, the determination result in Step S202 is "No" and the control unit <NUM> proceeds to Step S206. In Step S206, the control unit <NUM> acquires the MLO image and the height of the compression plate <NUM>. Specifically, the control unit <NUM> acquires image data of the MLO image and the height of the compression plate <NUM> associated with the image data of the MLO image. In addition, the acquisition destination of the MLO image is not particularly limited as in Step S200.

Then, in Step S208, the control unit <NUM> determines whether the type of breast is the high-concentration type. A method for determining whether the type of breast is the high-concentration type in the control unit <NUM> is not particularly limited. For example, a method may be used which detects a breast region and a skin line from a breast image, calculates a first index value indicating the degree of a single composition of the breast region, detects the boundary between the fat tissues and the mammary gland tissues in a predetermined range from the skin line to the breast region in the breast image, calculates a second index value indicating the degree of the clogging of the mammary glands with respect to the breast region on the basis of at least one of the strength of the boundary or the distance from the skin line, and identifies the type of breast on the basis of the first index value and the second index value.

In a case in which the type of breast is not the high-concentration type, the determination result in Step S208 is "No" and the control unit <NUM> proceeds to Step S210. In this case, since the breast is not a so-called dense breast, the fat tissue pixel is included in the breast image of the MLO image.

Then, in Step S210, the control unit <NUM> converts the value of the fat tissue pixel in the MLO image into the value of the fat tissue pixel in the CC image using the above-mentioned Expression (<NUM>).

Then, in Step S212, the control unit <NUM> derives the percentage of the mammary glands using the value of the fat tissue pixel in the CC image converted in Step S210 as described above and proceeds to Step S218.

In contrast, in a case in which the type of breast is the high-concentration type, the determination result in Step S208 is "Yes" and the control unit <NUM> proceeds to Step S214. In this case, since the breast is a so-called dense breast, the possibility that the fat tissue pixel will not be included in the breast images of both the MLO image and the CC image is high.

Then, in Step S214, the control unit <NUM> detects the mammary gland tissue pixel included in the breast image of at least one of the CC image or the MLO image. As described above, in the case of the so-called dense breast, the mammary gland tissue pixels obtained by a portion of the breast which is estimated to be composed of only the mammary gland tissues are included in the breast image. The term "mammary gland tissue pixel" is a pixel corresponding to a portion of the breast which is estimated to be composed of only the mammary gland tissues. For example, the "mammary gland tissue pixel" may be a pixel corresponding to a portion of the breast in which the percentage of the mammary gland tissues is higher than that of at least the fat tissues and is greater than a predetermined threshold value for regarding a portion of the breast as being composed of only the mammary gland tissues. In addition, whether to use the CC image or the MLO image may be predetermined or may be selected by the user.

Then, in Step S216, the control unit <NUM> derives the percentage of the mammary glands using the value of the mammary gland tissue pixel detected in Step S214 and proceeds to Step S218. A method for deriving the percentage of the mammary glands from the value of the mammary gland tissue pixel in the control unit <NUM> is not particularly limited. For example, the percentage R of the mammary glands may be derived using the following Expression (<NUM>) in a case in which the value of the mammary gland tissue pixel is G.

In a case in which the value G of the mammary gland tissue pixel detected from the MLO image is used, the control unit <NUM> applies an expression obtained by replacing "A" and "a" in the above-mentioned Expression (<NUM>) with "G" and "g" to convert the value G of the mammary gland tissue pixel of the MLO image into the value of the mammary gland tissue pixel of the CC image and then derives the percentage of the mammary glands.

In Step S218, the control unit <NUM> displays the radiographic image and the derived percentage of the mammary glands on the display unit <NUM> and ends the mammary gland percentage derivation process. In addition, the radiographic image displayed on the display unit <NUM> by the control unit <NUM> is not particularly limited. It is preferable to display at least the CC image.

As described above, in the console <NUM> according to this embodiment, the control unit <NUM> functions as an acquisition unit that acquires a CC image and an MLO image as a plurality of radiographic images of the same breast which have been captured in a plurality of different states related to the compression of the breast and a derivation unit that derives, on the basis of the amount of incident radiation derived from the value of a fat tissue pixel in a radiographic image in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only the fat tissues is included in a breast image among the plurality of radiographic images acquired by the acquisition unit, the percentage of the mammary glands of a breast image in a radiographic image different from the radiographic image used to derive the amount of incident radiation.

As such, in the console <NUM> according to this embodiment, in a case in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only the fat tissues is not included in the radiographic image of the breast, the percentage of the mammary glands in the breast image is derived using the fat tissue pixels in the radiographic images of the same breast which are captured under different conditions related to compression.

Therefore, according to the console <NUM> of this embodiment, even in a case in which the fat tissue pixel obtained by a portion of the breast which is estimated to be composed of only the fat tissues is not included in the radiographic image of the breast, it is possible to derive the percentage of the mammary glands with high accuracy.

In this embodiment, the aspect in which the plurality of radiographic images captured in a plurality of different states related to the compression of the breast are the CC image and the MLO image has been described above. However, the invention is not limited to this embodiment. The plurality of radiographic images may include radiographic images including different fat tissue pixels. For example, in a case in which the positioning of the subject is changed, the state related to the compression of the breast is changed. Therefore, a plurality of radiographic images in which the positions of the subject are different from each other may be used.

In the mammary gland percentage derivation process performed by the console <NUM> according to this embodiment, in a case in which the breast is determined to be a dense breast (in the case of Y in Step S208 of <FIG>), the value of the mammary gland tissue pixel is used to derive the percentage of the mammary glands. However, the following aspect may be used. Instead of the determination in Step S208, as in Step S209 in another example of the mammary gland percentage derivation process illustrated in <FIG>, it is determined whether the fat tissue pixel is included in the breast image of the MLO image. In a case in which the fat tissue pixel is not included in the breast image, the determination result is "No" and the process proceeds to Step S214. In a case in which the fat tissue pixel is included in the breast image, the determination result is "Yes" and the process proceeds to Step S210.

In this embodiment, the aspect in which the value of the fat tissue pixel of the MLO image is converted into the value of the fat tissue pixel of the CC image by the above-mentioned Expression (<NUM>) has been described above. However, the aspect of the conversion is not limited to the aspect using the above-mentioned Expression (<NUM>).

In a case in which the percentage of the mammary glands is derived using the MLO image, the control unit <NUM> of the console <NUM> may further derive the percentage of the mammary glands in the MLO image, using the value of the fat tissue pixel (or the mammary gland tissue pixel) of the MLO image, and may display both the percentage of the mammary glands in the MLO image and the percentage of the mammary glands in the CC image on the display unit <NUM>.

In the above-described embodiment, the aspect in which the high-concentration-type breast is used as the breast with a relatively high mammary gland density has been described. What kind of breast the breast with a relatively high mammary gland density is is not limited to the above-described embodiment. For example, one of the non-uniform high-concentration-type breast and the high-concentration-type breast may be used as the breast with a relatively high mammary gland density. In addition, for example, the breasts corresponding to classification by the United States Breast Imaging Reporting and Data System (BI-RADS) evaluation system may be used. In BI-RADS, the breasts are classified into any of four categories (a to d) according to the density of the mammary glands. However, the breasts classified into category d or categories c and d may be used as the breast with a relatively high mammary gland density. In addition, the breast defined as a so-called dense breast may be used as the breast with a relatively high mammary gland density. In addition, the specific breast defined as the dense breast may be based on predetermined criteria, such as a mammographic quality control manual and an operating system BI-RADS. Specifically, which criteria the breast with a relatively high mammary gland density is based on can vary depending on, for example, the country in which the technology of the present disclosure is operated and the standard at that time. In addition, what kind of breast the breast with a relatively high mammary gland density is and which criteria the definition of the dense breast is based on may be preset in the console <NUM> or may be set by the user.

In the above-described embodiment, various processors other than the CPU may perform the mammary gland percentage derivation process performed by the execution of software (program) by the CPU. In this case, examples of the processor include a programmable logic device (PLD), such as a field-programmable gate array (FPGA), whose circuit configuration can be changed after manufacture and a dedicated electric circuit, such as an application specific integrated circuit (ASIC), which is a processor having a dedicated circuit configuration designed to perform a specific process. In addition, the mammary gland percentage derivation process may be performed by one of the various processors or may be performed by a combination of two or more processors of the same type or different types (for example, a combination of a plurality of FPGAs and a combination of a CPU and an FPGA). Specifically, the hardware structure of the various processors is an electric circuit obtained by combining circuit elements such as semiconductor elements.

In the above-described embodiment, the aspect in which various programs, such as the programs stored in the control unit <NUM> of the mammography apparatus <NUM> and the mammary gland percentage derivation processing program stored in the control unit <NUM> of the console <NUM>, are stored (installed) in the ROMs (30B and 40B) of the control unit <NUM> and the control unit <NUM> in advance has been described. However, the invention is not limited thereto. Each of the various programs may be recorded on a recording medium, such as a compact disk read only memory (CD-ROM), a digital versatile disk read only memory (DVD-ROM), or a universal serial bus (USB) memory, and then provided. In addition, each of the various programs may be downloaded from an external apparatus through the network.

In the above-described embodiment, the radiation X is not particularly limited. For example, X-rays or γ-rays may be applied.

Claim 1:
An image processing apparatus (<NUM>) comprising:
an acquisition unit (<NUM>), adapted to acquire a first radiographic image (<NUM>CC, <NUM>CC) which has been captured in a first state related to a first compression of a breast, and a second radiographic image (<NUM>MLO, <NUM>MLO) which has been captured in a second state related to a second compression of the same breast, the second state related to the second compression being different from the first state related to the first compression; and
a derivation unit (<NUM>) adapted to derive a percentage of mammary glands of a breast image in the first radiographic image, characterized in that in a case in which the breast image of the fist radiographic image does not include a fat tissue pixel, the percentage of mammary glands in the first radiographic image is derived on the basis of an amount of incident radiation derived from a value of a fat tissue pixel in the second radiographic image, with the fat tissue pixel of the second radiographic image being obtained by a portion of the breast which is estimated to be composed of only fat tissues.