Patent Description:
A technology of performing contrast imaging of capturing a low-energy image and a high-energy image by irradiating a subject into which a contrast medium has been injected with radiation having different energies to generate a difference image showing a difference between the high-energy image and the low-energy image. For example, in <CIT>, a technology of performing energy sub-moving image capturing in an angiography method is known.

By the way, the difference image showing the difference between the high-energy image and the low-energy image is an image in which the contrast medium is clearly reflected and from which a lesion in which a contrast medium has permeated or a body tissue other than a region of interest is removed. However, the contrast medium also permeates a normal body tissue that is not the lesion or the like, although the amount is relatively small as compared with the lesion or the like. For example, in the contrast imaging for a tumor of a breast, the contrast medium mainly permeates the tumor, but the contrast medium also permeates a normal mammary gland structure or fat tissue, although the amount is relatively small. Therefore, in the difference image between the high-energy image and the low-energy image, it may be difficult to see the region of interest. Both disclosures <CIT> and also <CIT> teach to use dual energy x-ray imaging with contrast agent at different times. Solution to Problem.

The present disclosure is made in view of the above circumstances, and provides an image processing apparatus, an image processing method, and a non-transitory storage medium storing an image processing program capable of making it easier to see a region of interest in which a contrast medium has permeated in a radiation image.

A first aspect of the present disclosure relates to an image processing apparatus comprising at least one processor, in which the processor acquires a low-energy image captured by a radiography apparatus by emitting radiation having first energy to a subject into which a contrast medium has been injected, and a plurality of high-energy images captured by the radiography apparatus by emitting radiation having second energy higher than the first energy at a plurality of different imaging timings after the injection of the contrast medium, and generates a second difference image showing a difference between a plurality of first difference images showing a difference of the low-energy image and each of the plurality of high-energy images to remove a pixel value corresponding to the contrast medium that has permeated outside a region of interest.

In an embodiment, the processor identifies a coefficient at which a sum of pixel values of the second difference image is the smallest, and generates the second difference image by subtracting image data obtained by multiplying one first difference image among the plurality of first difference images by the coefficient from image data of the other first difference image for each corresponding pixel.

In an embodiment, the processor identifies a coefficient at which a sum of pixel values outside the region of interest in the second difference image is the smallest, and generates the second difference image by subtracting image data obtained by multiplying one first difference image among the plurality of first difference images by the coefficient from image data of the other first difference image for each corresponding pixel.

In an embodiment, the processor generates the second difference image after matching contrasts of the plurality of first difference images with each other.

In an embodiment, the processor matches contrasts of at least one of a mammary gland structure or a region other than a region of interest in the first difference image.

In an embodiment, the processor normalizes the second difference image based on an interval of the plurality of imaging timings.

In an embodiment, the processor performs image processing of enhancing the region of interest on the second difference image.

In an embodiment, the processor acquires, as the low-energy image, a plurality of low-energy images captured by the radiography apparatus by emitting the radiation having the first energy at the imaging timing of each of the plurality of high-energy images, and generates, for each imaging timing, a first difference image showing a difference of each of the plurality of low-energy images and each of the plurality of high-energy images.

In an embodiment, the processor acquires, as the low-energy image, a plurality of low-energy images captured by the radiography apparatus by emitting the radiation having the first energy at the imaging timing of each of the plurality of high-energy images, generates a third difference image showing a difference between the plurality of high-energy images and a fourth difference image showing a difference between the plurality of low-energy images, and generates the second difference image by generating an image showing a difference between the third difference image and the fourth difference image.

In an embodiment, the processor generates the plurality of first difference images by using a common low-energy image.

Another aspect of the present disclosure provides an image processing method executed by a computer, as defined by claim <NUM>.

A twelfth aspect of the present disclosure relates to a non-transitory storage medium storing a program causing a computer to execute an image processing, as defined by claim <NUM>.

According to the present disclosure, it is possible to make it easier to see the region of interest in which the contrast medium has permeated in the radiation image.

In the following, an embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that the present embodiment does not limit the present invention.

First, an example of an overall configuration of a radiography system according to the present embodiment will be described. <FIG> shows a configuration diagram showing an example of an overall configuration of a radiography system <NUM> according to the present embodiment. As shown in <FIG>, the radiography system <NUM> according to the present embodiment comprises a mammography apparatus <NUM> and a console <NUM>. The mammography apparatus <NUM> according to the present embodiment is an example of a radiography apparatus according to the present disclosure. In addition, the console <NUM> according to the present embodiment is an example of an image processing apparatus according to the present disclosure.

First, the mammography apparatus <NUM> according to the present embodiment will be described. <FIG> shows a side view showing an example of an appearance of the mammography apparatus <NUM> according to the present embodiment. It should be noted that <FIG> shows the example of the appearance of the mammography apparatus <NUM> as viewed from a right side of an examinee.

The mammography apparatus <NUM> according to the present embodiment is an apparatus that uses a breast of the examinee as a subject and captures a radiation image of the breast by irradiating the breast with radiation R (for example, X-rays). It should be noted that the mammography apparatus <NUM> may be an apparatus that images the breast of the examinee in a state in which the examinee is sitting on a chair (including a wheelchair) or the like (sitting state) in addition to a state in which the examinee is standing (standing state).

In addition, the mammography apparatus <NUM> according to the present embodiment has a function of performing two types of imaging of so-called contrast imaging in which the imaging is performed in a state in which a contrast medium has been injected into the breast of the examinee and general imaging. It should be noted that, in the present embodiment, the imaging to be performed in a state in which the contrast medium has been injected into the breast of the examinee refers to the "contrast imaging", and the imaging that is not the contrast imaging refers to the "general imaging".

As shown in <FIG>, the mammography apparatus <NUM> according to the present embodiment comprises a control unit <NUM>, a storage unit <NUM>, and an interface (I/F) unit <NUM> inside the imaging table <NUM>. The control unit <NUM> controls an overall operation of the mammography apparatus <NUM> under the control of the console <NUM>. The control unit <NUM> comprises a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM) (all not shown). The ROM stores, in advance, various programs, including an imaging processing program for performing control related to radiation image capturing, which is executed by the CPU. The RAM transitorily stores various data.

The storage unit <NUM> stores the image data of the radiation image captured by the radiation detector <NUM> or various types of other information. Specific examples of the storage unit <NUM> include a hard disk drive (HDD) and a solid state drive (SSD). The I/F unit <NUM> performs communication of various types of information with the console <NUM> by wireless communication or wired communication. The image data of the radiation image captured by the radiation detector <NUM> in the mammography apparatus <NUM> is transmitted to the console <NUM> via the I/F unit <NUM> by wireless communication or wired communication.

In addition, an operation unit <NUM> is provided as a plurality of switches on an imaging table <NUM> of the mammography apparatus <NUM>, for example. It should be noted that the operation unit <NUM> may be provided as a touch panel type switch, or may be provided as a foot switch operated by a user, such as a doctor or an engineer with a foot.

The radiation detector <NUM> detects the radiation R that has passed through the breast which is the subject. In addition, as shown in <FIG>, the radiation detector <NUM> is disposed inside the imaging table <NUM>. In the mammography apparatus <NUM> according to the present embodiment, the user positions the breast of the examinee on an imaging surface 30A of the imaging table <NUM> in a case of performing the imaging.

The radiation detector <NUM> detects the radiation R transmitted through the breast of the examinee and the imaging table <NUM>, generates a radiation image based on the detected radiation R, and outputs image data representing the generated radiation image. A type of the radiation detector <NUM> according to the present embodiment is not particularly limited. For example, a radiation detector of an indirect conversion method that converts the radiation R into light and converts the converted light into a charge may be used, and a radiation detector of a direct conversion method that directly converts the radiation R into a charge may be used.

A radiation emitting unit <NUM> comprises the radiation source 37R. As shown in <FIG>, the radiation emitting unit <NUM> is provided in an arm part <NUM> together with the imaging table <NUM> and the compression unit <NUM>. As shown in <FIG>, a face guard <NUM> is attachable and detachable at a position near the examinee on the arm part <NUM> below the radiation emitting unit <NUM>. The face guard <NUM> is a protective member for protecting the examinee from the radiation R emitted from the radiation source 37R.

It should be noted that, as shown in <FIG>, the mammography apparatus <NUM> according to the present embodiment comprises the arm part <NUM>, a base <NUM>, and a shaft part <NUM>. The arm part <NUM> is held by the base <NUM> to be movable in a vertical direction (Z-axis direction). The shaft part <NUM> connects the arm part <NUM> to the base <NUM>. In addition, the arm part <NUM> is rotatable relative to the base <NUM> with the shaft part <NUM> as a rotation axis.

The arm part <NUM>, the imaging table <NUM>, and the compression unit <NUM> can be separately rotated relative to the base <NUM> with the shaft part <NUM> as a rotation axis. In the present embodiment, the base <NUM>, the arm part <NUM>, the imaging table <NUM>, and the compression unit <NUM> are each provided with an engaging part (not shown), and each of the arm part <NUM>, the imaging table <NUM>, and the compression unit <NUM> is connected to the base <NUM> by switching a state of the engaging part. One or two of the arm part <NUM>, the imaging table <NUM>, or the compression unit <NUM>, which are connected to the shaft part <NUM>, are integrally rotated around the shaft part <NUM>.

The compression unit <NUM> is provided with a compression plate driving unit (not shown) that moves the compression plate <NUM> in the vertical direction (Z-axis direction). The compression plate <NUM> according to the present embodiment has a function of compressing the breast of the examinee. A support part <NUM> of the compression plate <NUM> is attachably and detachably attached to the compression plate driving unit, is moved in the vertical direction (Z-axis direction) by the compression plate driving unit, and compresses the breast of the examinee with the imaging table <NUM>.

On the other hand, the console <NUM> according to the present embodiment has a function of controlling the mammography apparatus <NUM> by using an imaging order and various types of information acquired from a radiology information system (RIS) <NUM> via a wireless communication local area network (LAN) and the like, and an instruction performed by the user by an operation unit <NUM> and the like.

The console <NUM> according to the present embodiment is, for example, a server computer. As shown in <FIG>, the console <NUM> comprises a control unit <NUM>, a storage unit <NUM>, an I/F unit <NUM>, the operation unit <NUM>, and a display unit <NUM>. The control unit <NUM>, the storage unit <NUM>, the I/F unit <NUM>, the operation unit <NUM>, and the display unit <NUM> are connected to each other via a bus <NUM>, such as a system bus or a control bus, such that various types of information can be exchanged.

The control unit <NUM> according to the present embodiment controls an overall operation of the console <NUM>. The control unit <NUM> comprises a CPU 50A, a ROM 50B, and a RAM 50C. The ROM 50B stores, in advance, various programs including an irradiation control processing program 51A and an image processing program 51B, which are executed by the CPU 50A and will be described below. The RAM 50C transitorily stores various data. The CPU 50A according to the present embodiment is an example of a processor according to the present disclosure. The image processing program 51B according to the present embodiment is an example of an image processing program according to the present disclosure.

The storage unit <NUM> stores the image data of the radiation image captured by the mammography apparatus <NUM> or various types of other information. Specific examples of the storage unit <NUM> include an HDD and an SSD.

The operation unit <NUM> is used by the user to input the instruction, various types of information, and the like related to the radiation image capturing and the like, including an irradiation instruction of the radiation R. The operation unit <NUM> is not particularly limited, and examples thereof include various switches, a touch panel, a touch pen, and a mouse. The display unit <NUM> displays various types of information. It should be noted that the operation unit <NUM> and the display unit <NUM> may be integrated to form a touch panel display.

The I/F unit <NUM> performs communication of various types of information between the mammography apparatus <NUM> and the RIS <NUM> by wireless communication or wired communication. The console <NUM> according to the present embodiment receives the image data of the radiation image captured by the mammography apparatus <NUM> from the mammography apparatus <NUM> via the I/F unit <NUM> by wireless communication or wired communication.

Further, <FIG> shows a functional block diagram of an example of the configuration of the console <NUM> according to the present embodiment. As shown in <FIG>, the console <NUM> comprises a control unit <NUM>. As an example, in the console <NUM> according to the present embodiment, the CPU 50A of the control unit <NUM> functions as the control unit <NUM> by the CPU 50A executing the irradiation control processing program 51A stored in the ROM 50B.

The control unit <NUM> has a function of performing control related to the irradiation with the radiation R in the mammography apparatus <NUM> in the contrast imaging. In the present embodiment, in a case of performing the contrast imaging, the radiation image is captured by emitting the radiation having the first energy from the radiation source 37R to the breast in a state in which the contrast medium has been injected. In addition, the radiation image is captured by emitting the radiation having the second energy higher than the first energy from the radiation source 37R to the breast in a state in which the contrast medium has been injected. It should be noted that, in the present embodiment, the radiation image captured by emitting the radiation R having the first energy is referred to as a "low-energy image", and the radiation image captured by emitting the radiation R having the second energy is referred to as a "high-energy image". In addition, in a case in which the images captured by the mammography apparatus <NUM> are collectively referred to without distinction between types, such as the low-energy image and the high-energy image, the images are simply referred to as the "radiation image".

For example, an iodine contrast medium with a k-absorption edge of <NUM> keV is generally used as the contrast medium for the contrast imaging. In the contrast imaging in this case, the low-energy image is captured by emitting the radiation R having the first energy lower than the k-absorption edge of the iodine contrast medium. In addition, the high-energy image is captured by emitting the radiation R having the second energy higher than the k-absorption edge of the iodine contrast medium.

Therefore, in the contrast imaging, the control unit <NUM> according to the present embodiment performs control of emitting the radiation R having the first energy from the radiation source 37R and control of emitting the radiation R having the second energy. In other words, the control unit <NUM> performs control of causing the mammography apparatus <NUM> to capture the low-energy image and control of causing the mammography apparatus <NUM> to capture the high-energy image.

A body tissue, such as a mammary gland, and the contrast medium have different absorption characteristics of the radiation. Therefore, the contrast medium is clearly reflected in the high-energy image captured as described above. In addition, in the low-energy image, almost no contrast medium is reflected, and the body tissue, such as the mammary gland, is clearly reflected. Therefore, the difference image showing a difference between the low-energy image and the high-energy image can be made to be an image in which a mammary gland structure is removed and the contrast medium is clearly reflected. The contrast amount with the contrast medium appears in the pixel value of the difference image.

In addition, in the contrast imaging, capturing of the low-energy image and the high-energy image is regarded as capturing of a set of difference images, and the difference images are captured at a plurality of different imaging timings. In the example shown in <FIG>, the low-energy image <NUM> (see <FIG>, <NUM><NUM>) and the high-energy image <NUM> (see <FIG>, <NUM><NUM>) are captured at a first imaging timing. In addition, the low-energy image <NUM> (see <FIG>, <NUM><NUM>) and the high-energy image <NUM> (see <FIG>, <NUM><NUM>) are captured at a second imaging timing after a predetermined time has elapsed from the first imaging timing.

It should be noted that the predetermined time from the first imaging timing to the second imaging timing is not limited. For example, the predetermined time may be a time determined depending on a contrast condition, for example, in consideration of the type of the object of interest, or may be a time determined in consideration of a thickness, a composition, or the like of the breast which is the subject.

In addition, the console <NUM> according to the present embodiment comprises an acquisition unit <NUM>, a generation unit <NUM>, and a display control unit <NUM>. As an example, in the console <NUM> according to the present embodiment, the CPU 50A of the control unit <NUM> also functions as the acquisition unit <NUM>, the generation unit <NUM>, and the display control unit <NUM> by the CPU 50A executing the image processing program 51B stored in the ROM 50B.

The acquisition unit <NUM> has a function of acquiring the low-energy image and the high-energy image captured by the mammography apparatus <NUM>. Specifically, the acquisition unit <NUM> acquires image data representing the low-energy image and image data representing the high-energy image captured by the radiation detector <NUM> of the mammography apparatus <NUM> via the I/F unit <NUM> and the I/F unit <NUM>. The acquisition unit <NUM> outputs the acquired low-energy image and high-energy image to the generation unit <NUM>.

The generation unit <NUM> has a function of generating a second difference image showing a difference between a plurality of difference images showing a difference of the low-energy image and each of a plurality of high-energy images to remove a pixel value corresponding to the contrast medium that has permeated outside a region of interest. As shown in <FIG>, the generation unit <NUM> according to the present embodiment includes a first generation unit <NUM> and a second generation unit <NUM>.

The first generation unit <NUM> has a function of generating the plurality of difference images showing a difference between the low-energy image and each of the plurality of high-energy images captured at each imaging timing. It should be noted that, hereinafter, the difference image showing the difference between the high-energy image and the low-energy image is referred to as a first difference image. The difference image generated by the first generation unit <NUM> according to the present embodiment is the first difference image, and is an example of a first difference image according to the present disclosure. The first generation unit <NUM> outputs the plurality of generated first difference images to the second generation unit <NUM>.

As an example, in the present embodiment, the first difference image is generated by deriving the difference between the low-energy image and each high-energy image. In the example shown in <FIG>, the first generation unit <NUM> generates a first difference image <NUM><NUM> between the low-energy image <NUM><NUM> captured at the first imaging timing and the high-energy image <NUM><NUM>. Specifically, the first generation unit <NUM> generates the image data representing the first difference image in which the mammary gland tissue is removed and the contrast medium is enhanced, by subtracting image data obtained by multiplying the low-energy image <NUM><NUM> by a predetermined coefficient from image data obtained by multiplying the high-energy image <NUM><NUM> by a predetermined coefficient for each corresponding pixel. Similarly, the first generation unit <NUM> generates a first difference image <NUM><NUM> between the low-energy image <NUM><NUM> and the high-energy image <NUM><NUM> captured at the second imaging timing.

The second generation unit <NUM> has a function of generating a difference image showing the difference between the plurality of first difference images generated by the first generation unit <NUM>. It should be noted that, hereinafter, the difference image showing the difference between the first difference images will be referred to as a second difference image. The difference image generated by the second generation unit <NUM> according to the present embodiment is the second difference image, and is an example of a second difference image according to the present disclosure. The second generation unit <NUM> outputs the generated second difference image to the display control unit <NUM>.

As an example, in the present embodiment, the second difference image showing the difference between the first difference image between the high-energy image and the low-energy image captured at the second imaging timing and the first difference image between the high-energy image and the low-energy image captured at the first imaging timing is generated. In the example shown in <FIG>, the second generation unit <NUM> generates a second difference image <NUM> showing the difference between the first difference image <NUM><NUM> generated at the second imaging timing and the first difference image <NUM><NUM> generated at the first imaging timing.

The second difference image (second difference image <NUM> in <FIG>) generated by the second generation unit <NUM> will be described with reference to <FIG>. In other words, the second difference image, which is generated by the generation unit <NUM> and output to the display control unit <NUM>, will be described.

As shown in a graph <NUM> showing a correspondence relationship between the time and the contrast amount in <FIG>, the contrast medium more easily permeates a lesion, such as a tumor, than a normal mammary gland (see "normal" in the graph <NUM>). Also, as the lesion is more malignant (see "malignant" in the graph <NUM>), the contrast medium tends to permeate faster and the contrast medium tends to be washed out faster than in a case in which the lesion is benign (see "benign" in the graph <NUM>). In addition, as shown in the graph <NUM>, the contrast medium also permeates fat (see "fat" in the graph <NUM>), although the amount is smaller than that of the lesion or the mammary gland.

Therefore, the first difference image showing the difference between the high-energy image and the low-energy image may be an image in which the contrast medium that has permeated fat or the mammary gland structure is reflected. In the example shown in <FIG>, in the first difference image <NUM><NUM> obtained at the first imaging timing, the contrast medium is reflected in both a normal region <NUM><NUM> corresponding to the normal mammary gland and a region of interest <NUM><NUM> in a breast <NUM><NUM>. In addition, in the first difference image <NUM><NUM> obtained at the second imaging timing, the contrast medium is reflected in both a normal region <NUM><NUM> corresponding to the normal mammary gland and a region of interest <NUM><NUM> in a breast <NUM><NUM>.

As can be seen from the graph <NUM> in <FIG>, the contrast amount of the normal region <NUM><NUM> in the first difference image <NUM><NUM> is larger than the contrast amount of the normal region <NUM><NUM> in the first difference image <NUM><NUM>. In addition, the contrast amount of the region of interest <NUM><NUM> in the first difference image <NUM><NUM> is larger than the contrast amount in the region of interest <NUM><NUM> in the first difference image <NUM><NUM>. In addition, an amount of change from the contrast amount of the region of interest <NUM><NUM> to the contrast amount of the region of interest <NUM><NUM> is larger than an amount of change from the contrast amount of the normal region <NUM><NUM> to the contrast amount of the normal region <NUM><NUM>.

Therefore, by generating the second difference image <NUM> showing the difference between the first difference image <NUM><NUM> obtained at the second imaging timing and the first difference image <NUM><NUM> obtained at the first imaging timing, the second difference image <NUM> can be made to be an image in which the contrast medium that has permeated a normal mammary gland structure outside the region of interest is not reflected. In the example shown in <FIG>, a pixel value of the normal region <NUM><NUM> of the first difference image <NUM><NUM> is set to "<NUM>", a pixel value of the region of interest <NUM><NUM> is set to "<NUM>", a pixel value of the normal region <NUM><NUM> of the first difference image <NUM><NUM> is set to "<NUM>", and a pixel value of the region of interest <NUM><NUM> is set to "<NUM>". In this case, in the second difference image <NUM> generated by subtracting the image data obtained by multiplying the first difference image <NUM><NUM> by "<NUM>" as a predetermined removal coefficient from the image data of the first difference image <NUM><NUM> for each corresponding pixel, a pixel value of a normal region <NUM><NUM> is set to "<NUM>", and a pixel value of a region of interest <NUM><NUM> is set to "<NUM>". As described above, in the example shown in <FIG>, the second difference image <NUM> can be made to be an image in which the contrast amount is not reflected in the normal region <NUM><NUM>.

As described above, in the present embodiment, the second generation unit <NUM> generates the second difference image <NUM> showing the difference between the first difference image <NUM><NUM> and the first difference image <NUM><NUM>, so that the second difference image <NUM> can be made to be an image in which the pixel value corresponding to the contrast medium that has permeated outside the region of interest is removed. It should be noted that the removal of the pixel value corresponding to the contrast medium is not limited to a case of complete removal, and includes, for example, a case of a slight amount of residual.

The display control unit <NUM> has a function of displaying, on the display unit <NUM>, the second difference image generated by the generation unit <NUM>.

Next, an action of the console <NUM> in the contrast imaging by the radiography system <NUM> according to the present embodiment will be described with reference to the drawings.

<FIG> shows a flowchart showing an example of a flow of the contrast imaging by the radiography system <NUM> according to the present embodiment. In a case in which the contrast imaging is performed, first, the user injects the contrast medium into the breast, which is the subject, as shown in step S10 of <FIG>. Next, as shown in step S12, the user positions the breast of the examinee on the imaging table <NUM> of the mammography apparatus <NUM> and compresses the breast with the compression plate <NUM>.

Next, in step S14, the mammography apparatus <NUM> captures the radiation image, specifically, the low-energy image and the high-energy image. In the present embodiment, as described above, the control unit <NUM> of the console <NUM> performs control related to the irradiation with the radiation R in the mammography apparatus <NUM>. As an example, in the console <NUM> according to the present embodiment, the CPU 50A of the control unit <NUM> executes the irradiation control processing program 51A stored in the ROM 50B to execute irradiation control processing shown in <FIG> as an example. <FIG> shows a flowchart showing an example of a flow of the irradiation control processing executed in the console <NUM> according to the present embodiment.

In step S100 of <FIG>, the control unit <NUM> determines whether or not the irradiation instruction of the radiation R is received. A negative determination is made in the determination in step S100 until the irradiation instruction is received. On the other hand, in a case in which the irradiation instruction is received, a positive determination is made in the determination in step S100, and the processing proceeds to step S102.

In step S102, the control unit <NUM> outputs the instruction to perform the irradiation with the radiation R having the first energy to the mammography apparatus <NUM>. In the mammography apparatus <NUM>, the control unit <NUM> emits the radiation R having the first energy from the radiation source 37R toward the breast based on the instruction input from the console <NUM>, and the low-energy image is captured by the radiation detector <NUM>. In the example shown in <FIG>, the low-energy image <NUM><NUM> is captured.

In next step S104, the control unit <NUM> outputs the instruction to perform the irradiation with the radiation R having the second energy to the mammography apparatus <NUM>. In the mammography apparatus <NUM>, the control unit <NUM> emits the radiation R having the second energy from the radiation source 37R toward the breast based on the instruction input from the console <NUM>, and the high-energy image is captured by the radiation detector <NUM>. In the example shown in <FIG>, the high-energy image <NUM><NUM> is captured.

In next step S106, the control unit <NUM> determines whether or not the second imaging timing is reached. A negative determination is made in the determination in step S106 until the second imaging timing is reached. On the other hand, in a case in which the second imaging timing is reached, a positive determination is made in the determination in step S106, and the processing proceeds to step S108.

In step S108, the control unit <NUM> outputs the instruction to perform the irradiation with the radiation R having the first energy to the mammography apparatus <NUM>, as in step S102. The mammography apparatus <NUM> captures the low-energy image according to the instruction input from the console <NUM>. In the example shown in <FIG>, the low-energy image <NUM><NUM> is captured.

In next step S110, the control unit <NUM> outputs the instruction to perform the irradiation with the radiation R having the second energy to the mammography apparatus <NUM>, as in step S104. The mammography apparatus <NUM> captures the high-energy image according to the instruction input from the console <NUM>. In the example shown in <FIG>, the high-energy image <NUM><NUM> is captured. In a case in which the processing of step S110 ends, the irradiation control processing shown in <FIG> ends.

In this way, in a case in which the irradiation control processing shown in <FIG> ends, the contrast imaging ends, and the processing of step S14 shown in <FIG> ends. It should be noted that the control unit <NUM> may notify the user that the contrast imaging ends.

Therefore, in next step S <NUM>, the compression of the breast is released. Specifically, the control unit <NUM> outputs an instruction to the mammography apparatus <NUM> to move the compression plate <NUM> in a direction away from the imaging table <NUM>. In the mammography apparatus <NUM>, the control unit <NUM> moves the compression plate <NUM> in the direction away from the imaging table <NUM> based on the input instruction. As a result, the compression of the breast is released. It should be noted that the release of the breast compression may be performed according to the instruction of the user, or may be performed automatically according to the end of the contrast imaging.

In next step S18, the console <NUM> performs difference image generation display processing shown in <FIG>. In the console <NUM> according to the present embodiment, as an example, the CPU 50A of the control unit <NUM> executes the image processing program 51B stored in the ROM 50B, thereby executing the difference image generation display processing shown in <FIG> as an example. <FIG> shows a flowchart showing an example of a flow of the difference image generation display processing executed in the console <NUM> according to the present embodiment.

In step S200, as described above, the acquisition unit <NUM> acquires the low-energy image and the high-energy image captured by the contrast imaging from the mammography apparatus <NUM>. It should be noted that a timing at which the acquisition unit <NUM> acquires the low-energy image and the high-energy image is not limited. For example, the low-energy image and the high-energy image may be acquired from the mammography apparatus <NUM> each time each of the low-energy image and the high-energy image is captured. In addition, for example, the low-energy image and the high-energy image stored in the storage unit <NUM> of the mammography apparatus <NUM> may be acquired after capturing all the low-energy images and the high-energy images ends. In addition, an order of acquiring the low-energy image and the high-energy image is not limited. In the example shown in <FIG>, the acquisition unit <NUM> acquires the low-energy images <NUM><NUM> and <NUM><NUM> and the high-energy images <NUM><NUM> and <NUM><NUM>.

In next step S202, the first generation unit <NUM> of the generation unit <NUM> generates the first difference image for each imaging timing from the low-energy image and the high-energy image acquired in step S200, as described above. In the example shown in <FIG>, the first generation unit <NUM> generates the first difference image <NUM><NUM> showing the difference between the high-energy image <NUM><NUM> and the low-energy image <NUM><NUM>. In addition, the first generation unit <NUM> generates the first difference image <NUM><NUM> showing the difference between the high-energy image <NUM><NUM> and the low-energy image <NUM><NUM>.

In next step S204, the second generation unit <NUM> of the generation unit <NUM> specifies the region of interest from the first difference image generated in step S202. In the example shown in <FIG>, the second generation unit <NUM> specifies the region of interest from each of the first difference image <NUM><NUM> and the first difference image <NUM><NUM>. It should be noted that a method by which the second generation unit <NUM> specifies the region of interest from the first difference image is not particularly limited. For example, the region of interest may be specified from the first difference image by receiving information about the region of interest input by the user. Specifically, at least one image of the first difference image, the low-energy image, or the high-energy image may be displayed on the display unit <NUM>, and a region designated by the user operating the operation unit <NUM> on the display image may be received as the information about the region of interest. In addition, for example, the second generation unit <NUM> may specify the region of interest by applying computer aided diagnosis (CAD) to the first difference image.

In next step S206, the second generation unit <NUM> specifies the removal coefficient described above. As described above, the second generation unit <NUM> generates the second difference image by subtracting the image data obtained by multiplying the first difference image obtained at the second imaging timing by the predetermined removal coefficient from the image data of the first difference image obtained at the first imaging timing for each corresponding pixel.

The second generation unit <NUM> according to the present embodiment specifies the removal coefficient based on the first difference image generated in step S202. A method by which the second generation unit <NUM> specifies the removal coefficient is not limited, but it is preferable to specify the removal coefficient at which the contrast medium that has permeated the mammary gland structure or the normal region can be more removed. In the example shown in <FIG>, the second generation unit <NUM> specifies "<NUM>" as the removal coefficient, as described above.

As the method of specifying the removal coefficient, for example, in a case in which the removal coefficient is determined in advance according to the type of the region of interest, the mammary gland mass of the breast, or the like, the second generation unit <NUM> need only specify the removal coefficient that is determined in advance according to the type of the region of interest, the mammary gland mass of the breast, or the like.

In addition, for example, the second generation unit <NUM> may specify the removal coefficient at which the sum of the pixel values of the generated second difference images is the smallest. In addition, for example, the second generation unit <NUM> may specify the removal coefficient at which the sum of the pixel values outside the region of interest in the generated second difference image is the smallest.

In next step S208, as described above, the second generation unit <NUM> generates the second difference image showing the difference between the first difference images generated in step S202 by using the removal coefficient specified in step <NUM>. In the example shown in <FIG>, the second generation unit <NUM> generates the second difference image <NUM> showing the difference between the first difference image <NUM><NUM> and the first difference image <NUM><NUM>.

It should be noted that, unlike the present embodiment, instead of the specification of the removal coefficient as described above, a form may be adopted in which the second generation unit <NUM> generates the second difference image after matching the contrasts of the first difference images, particularly, the contrasts of at least one of the mammary gland structure or the region other than the region of interest in the first difference image.

In addition, since noise tends to appear in the image as a high-frequency component, the second generation unit <NUM> may remove the high-frequency component by applying the low-pass filter to the first difference image, and then generate the second difference image from the first difference image having the low-frequency component.

In addition, in a case in which an interval between the first imaging timing and the second imaging timing is widened, the difference between the first difference images is large. Therefore, in order to remove the influence of the interval between the first imaging timing and the second imaging timing, the second generation unit <NUM> may normalize the second difference image with an interval between the first imaging timing and the second imaging timing.

In next step S210, the second generation unit <NUM> performs enhancement processing of enhancing the region of interest in the second difference image generated in step S208. As described above with reference to <FIG>, in the second difference image between the first difference images, the contrast amount (pixel value) of the region of interest is smaller than that in the first difference image obtained at the second imaging timing. In the example shown in <FIG>, the pixel value of the region of interest <NUM><NUM> in the first difference image <NUM><NUM> obtained at the second imaging timing is "<NUM>", whereas the pixel value of the region of interest <NUM><NUM> in the second difference image <NUM> is "<NUM>". Since the pixel value of the region of interest is reduced in this way, the second generation unit <NUM> performs the enhancement processing of enhancing the region of interest in order to make the region of interest easy to see. As an example, the second generation unit <NUM> according to the present embodiment performs gradation enhancement processing and frequency enhancement processing on the generated second difference image.

In next step S212, the display control unit <NUM> performs control of displaying, on the display unit <NUM>, the second difference image. <FIG> shows an example of a state in which the second difference image <NUM> after the enhancement processing is displayed on the display unit <NUM>. The example shown in <FIG> shows a form in which the first difference image <NUM><NUM> obtained at the first imaging timing and the first difference image <NUM><NUM> obtained at the second imaging timing are displayed side by side in the second difference image <NUM> after the enhancement processing on the display unit <NUM>. It should be noted that, in a case in which a plurality of radiation images including the second difference image <NUM> are displayed on the display unit <NUM> in this way, the display form is not limited to the form in which the plurality of radiation images including the second difference image <NUM> are displayed side by side as shown in <FIG>. For example, a display form may be adopted in which the plurality of radiation images are displayed according to the instruction of the user or automatically switched, or a display form may be adopted in which the plurality of radiation images are superimposed and displayed. In addition, the low-energy image, the high-energy image, or the like may also be displayed.

In addition, the example shown in <FIG> shows a form in which imaging timing information <NUM> indicating the imaging timing corresponding to each of the first difference image <NUM><NUM> and the first difference image <NUM><NUM> is further displayed. As described above, the display control unit <NUM> need only display at least the second difference image that has been subjected to the enhancement processing in step S210, and may further display at least one of other radiation images, the information about the contrast imaging, such as the imaging timing, or the information about the contrast amount.

In this way, in a case in which the processing of step S212 ends, the difference image generation display processing shown in <FIG> ends, and the difference image generation display processing of step S18 shown in <FIG> ends. As a result, the series of processing related to the contrast imaging in the radiography system <NUM> according to the present embodiment ends. It should be noted that a form may be adopted in which the low-energy image and the plurality of high-energy images, which are captured by the mammography apparatus <NUM> according to the present embodiment, the plurality of first difference images and the second difference image, which are generated by the console <NUM>, and the like are stored in the storage unit <NUM> of the console <NUM>, picture archiving and communication systems (PACS), or the like.

In addition, in each form described above, the form has been described in which the difference image generation display processing is performed as the series of processing after the contrast imaging which is the processing of S <NUM> in <FIG> ends, but the timing for performing the difference image generation display processing, that is, the timing for generating the first difference image and the second difference image or displaying the second difference image is not limited to the present form. For example, a form may be adopted in which the timing of each of the generation of the first difference image and the second difference image, and the display of the second difference image is a timing according to the user's desire after the contrast imaging.

As described above, the console <NUM> of each form described above comprises the CPU 50A as at least one processor. The CPU 50A acquires the low-energy image captured by the mammography apparatus <NUM> by emitting the radiation R having the first energy to the breast into which the contrast medium has been injected, and the plurality of high-energy images captured by the mammography apparatus <NUM> by emitting the radiation R having the second energy higher than the first energy, at a plurality of different imaging timings after the injection of the contrast medium. In addition, the CPU 50A generates the second difference image showing the difference between the plurality of first difference images showing the difference of the low-energy image and each of the plurality of high-energy images to remove the pixel value corresponding to the contrast medium that has permeated outside the region of interest.

As described above, the console <NUM> according to the present embodiment generates the second difference image showing the difference between the first difference images showing the difference between the high-energy image and the low-energy image. Therefore, the console <NUM> can make the second difference image to be the image in which the pixel value corresponding to the contrast medium that has permeated the mammary gland structure other than the object of interest is not included or the like, or the image in which the contrast amount is reduced even in a case in which the pixel value corresponding to the contrast medium that has permeated outside the object of interest is included. Therefore, with the console <NUM> according to the present embodiment, it is possible to obtain the radiation image (second difference image) in which the region of interest in which the contrast medium has permeated is more easily seen.

It should be noted that a method by which the generation unit <NUM> generates the first difference image and the second difference image is not limited to the form described above. For example, the difference image showing the difference between the low-energy images at each imaging timing may be generated, the difference image showing the difference between the high-energy images may be generated, and then the difference image showing the difference between the two difference images may be generated. In this case as well, the finally generated difference image corresponds to the second difference image. In the example shown in <FIG>, the generation unit <NUM> generates a third difference image <NUM> showing the difference between the high-energy image <NUM><NUM> and the high-energy image <NUM><NUM>. In addition, the generation unit <NUM> generates a fourth difference image <NUM> showing the difference between the low-energy image <NUM><NUM> and the low-energy image <NUM><NUM>. Further, the generation unit <NUM> generates the second difference image <NUM> showing the difference between the fourth difference image <NUM> and the third difference image <NUM>. It should be noted that the third difference image <NUM> according to the present form is an example of a third difference image according to the present disclosure, and the fourth difference image <NUM> is an example of a fourth difference image according to the present disclosure.

In addition, in the form described above, the form has been described in which both the low-energy image and the high-energy image are captured at each imaging timing, but the imaging timing of the low-energy image is not limited to the present form. As described above, the low-energy image is the image in which almost no contrast medium is reflected, and the body tissue, such as the mammary gland, is clearly reflected. Therefore, in a case in which the body movement is not taken into consideration, the low-energy image is the same image regardless of the imaging timing. Therefore, the imaging timing of the low-energy image is not limited. In addition, the number of times of capturing of the low-energy image may not be the same as the number of times of capturing of the high-energy image. As an example, <FIG> shows a form in which the low-energy image is captured only at the first imaging timing out of the first imaging timing and the second imaging timing. In this case, the generation unit <NUM> generates the first difference image <NUM><NUM> showing the difference between the high-energy image <NUM><NUM> and the low-energy image <NUM><NUM>. In addition, the generation unit <NUM> generates the first difference image <NUM><NUM> showing the difference between the high-energy image <NUM><NUM> and the low-energy image <NUM><NUM>. Further, the generation unit <NUM> generates the second difference image <NUM> showing the difference between the first difference image <NUM><NUM> and the first difference image <NUM><NUM>.

In addition, in the form described above, the form has been described in which the imaging timing is two times, but the imaging timing may be two or more times. In a case in which the imaging timing is set to <NUM> or more times, for example, a plurality of second difference images <NUM> can be generated.

In addition, in the form described above, the form has been described in which the low-energy image is first captured in the contrast imaging, but the present disclosure is not limited to the present form, and a form may be adopted in which the high-energy image is captured first.

In addition, in the form described above, the form has been described in which the breast is applied as an example of the subject according to the present disclosure, and the mammography apparatus <NUM> is applied as an example of the radiography apparatus according to the present disclosure, but the subject is not limited to the breast, and the radiography apparatus is not limited to the mammography apparatus. For example, the subject may be a chest, an abdomen, or the like, and a form may be adopted in which a radiography apparatus other than the mammography apparatus is applied as the radiography apparatus.

In addition, in the form described above, the form has been described in which the console <NUM> is an example of the image processing apparatus according to the present disclosure, but an apparatus other than the console <NUM> may have the function of the image processing apparatus according to the present disclosure. In other words, some or all of the functions of the control unit <NUM>, the acquisition unit <NUM>, the generation unit <NUM>, and the display control unit <NUM> may be provided in an apparatus other than the console <NUM>, for example, the mammography apparatus <NUM> or an external apparatus.

In addition, in the form described above, various processors shown below can be used as the hardware structure of processing units that execute various pieces of processing, such as the control unit <NUM>, the acquisition unit <NUM>, the generation unit <NUM>, and the display control unit <NUM>. As described above, the various processors include, in addition to the CPU which is a general-purpose processor which executes software (program) and functions as various processing units, a programmable logic device (PLD) which is a processor of which a circuit configuration can be changed after manufacture, such as a field programmable gate array (FPGA), and a dedicated electric circuit which is a processor having a circuit configuration which is designed for exclusive use in order to execute specific processing, such as an application specific integrated circuit (ASIC).

One processing unit may be composed of one of the various processors or may be composed of a combination of two or more processors of the same type or different types (for example, a combination of a plurality of FPGAs or a combination of a CPU and an FPGA). In addition, a plurality of processing units may be composed of one processor.

A first example of the configuration in which the plurality of processing units are composed of one processor is a form in which one processor is composed of a combination of one or more CPUs and software and the processor functions as the plurality of processing units, as represented by the computer, such as a client and a server. Second, as represented by a system on chip (SoC) or the like, there is a form of using a processor that realizes the function of the entire system including the plurality of processing units by one integrated circuit (IC) chip. As described above, various processing units are composed of one or more of the various processors as the hardware structure.

Further, more specifically, an electric circuit (circuitry) obtained by combining circuit elements, such as semiconductor elements, can be used as the hardware structure of the various processors.

Claim 1:
An image processing apparatus comprising:
at least one processor (50A) that is configured to:
acquire a low-energy image captured by a radiography apparatus by emitting radiation having first energy to a subject into which a contrast medium has been injected, and a plurality of high-energy images captured by the radiography apparatus by emitting radiation having second energy higher than the first energy at a plurality of different imaging timings after the injection of the contrast medium, and
characterized by generating a second difference image showing a difference between a plurality of first difference images showing a difference of the low-energy image and each of the plurality of high-energy images to remove a pixel value corresponding to the contrast medium that has permeated outside a region of interest.