Patent Description:
A mammography apparatus is known that captures a radiographic image by emitting radiation from a radiation source toward the breast of a subject and detecting radiation transmitted through the breast using a radiation detector.

As this type of mammography apparatus, there is a mammography apparatus that can perform contrast imaging in which a breast in a state in which a contrast medium using iodine is administered is a subject. In addition, as a mammography apparatus capable of performing contrast imaging, a mammography apparatus is known in which radiation having a first energy is emitted and a first radiographic image is captured by a radiation detector and radiation having a second energy different from the first energy is emitted and a second radiographic image is captured by the radiation detector. In a case where this apparatus is used, a doctor examines a lesion part using a third radiographic image which is generated from the first radiographic image and the second radiographic image and in which a contrast medium is emphasized.

Incidentally, in general, evaluation (so-called quality control: QC) of a mammography apparatus is performed using a radiographic image captured with a phantom for evaluation as a subject. As this type of phantom, a contrast imaging phantom used for evaluating the contrast imaging function of a mammography apparatus is known. For example, <CIT> (<CIT>) discloses a phantom including a contrast medium insert. <CIT> discloses a radiographic image capturing system according to the preamble of claim <NUM>. The mammography apparatus takes an image of a patient breast on which a reference film containing a contrast agent iodine has been disposed to enhance the contrast of the breast image. Both the breast and the reference film are imaged at the same time.

In conventional contrast imaging phantoms, in the case of evaluating a mammography apparatus, users such as technicians may be troublesome to handling, such as preparing a phantom containing a contrast medium in a liquid state. For this reason, improvement of convenience for users has been desired.

The present disclosure has been made in consideration of the above circumstances, and provides a radiographic image capturing system, a phantom, and an evaluation method that can improve the convenience in evaluating the contrast imaging function of a mammography apparatus.

A radiographic image capturing system of a first aspect of the present disclosure comprises: a mammography apparatus that emits radiation having a first energy to a subject and captures a first radiographic image with a radiation detector and emits radiation having a second energy greater than the first energy to the subject and captures a second radiographic image with the radiation detector and that captures the first radiographic image and the second radiographic image with a breast in a state in which a contrast medium using iodine is administered; and a phantom for evaluation of the mammography apparatus that has a solid material containing at least one element, which has a value of a k absorption edge that is equal to or greater than the first energy and equal to or less than the second energy, as an image evaluation pattern simulating the contrast medium.

A radiographic image capturing system of a second aspect of the present disclosure comprises: a mammography apparatus that emits radiation having a first energy to a subject and captures a first radiographic image with a radiation detector and emits radiation having a second energy greater than the first energy to the subject and captures a second radiographic image with the radiation detector and that captures the first radiographic image and the second radiographic image with a breast in a state in which a contrast medium using iodine is administered; and a phantom for evaluation of the mammography apparatus that has a solid material containing at least one element, which has an atomic number of <NUM> to <NUM>, as an image evaluation pattern simulating the contrast medium.

In the radiographic image capturing system of a third aspect of the present disclosure, a thickness of the solid material in an incidence direction of the radiation is a thickness determined according to a concentration of the contrast medium.

In the radiographic image capturing system of a fourth aspect of the present disclosure, the phantom further has another predetermined image evaluation pattern.

In the radiographic image capturing system of a fifth aspect of the present disclosure, the image evaluation pattern includes at least one of an image evaluation pattern for evaluating a contrast to noise ratio or an image evaluation pattern for evaluating low contrast detectability.

In the radiographic image capturing system of a sixth aspect of the present disclosure, the image evaluation pattern includes at least one of an image evaluation pattern simulating a mass, an image evaluation pattern simulating a microcalcification, or an image evaluation pattern simulating a fiber structure.

In the radiographic image capturing system of a seventh aspect of the present disclosure, the first energy is equal to or greater than <NUM> keV and less than a value of a k absorption edge of iodine, and the second energy is greater than the value of the k absorption edge of iodine and equal to or less than <NUM> keV.

In the radiographic image capturing system of an eighth aspect of the present disclosure, the solid material is molded by performing any of vapor deposition, sputtering, fine particle coating, and machining with respect to the element.

The radiographic image capturing system of a ninth aspect of the present disclosure further comprises: a generation unit that generates a third radiographic image in which the contrast medium is emphasized from the first radiographic image and the second radiographic image and that generates the third radiographic image in which the solid material is emphasized instead of the contrast medium in a case where the mammography apparatus captures the first radiographic image and the second radiographic image with the phantom as a subject.

The radiographic image capturing system of a tenth aspect of the present disclosure further comprises: an evaluation unit that evaluates the mammography apparatus based on the third radiographic image generated by the generation unit in a case where the phantom is a subject.

A phantom of an eleventh aspect of the present disclosure is a phantom for evaluation of a mammography apparatus comprising a solid material containing at least one element, which has a value of a k absorption edge that is equal to or greater than <NUM> keV and equal to or less than <NUM> keV, as an image evaluation pattern simulating a contrast medium using iodine.

A phantom of a twelfth aspect of the present disclosure is a phantom for evaluation of a mammography apparatus comprising a solid material containing at least one element, which has an atomic number of <NUM> to <NUM>, as an image evaluation pattern simulating a contrast medium using iodine.

An evaluation method of a thirteenth aspect of the present disclosure is an evaluation method for a mammography apparatus, and comprises: a step in which a phantom for evaluation of the mammography apparatus having a solid material containing at least one element, which has a value of a k absorption edge that is equal to or greater than <NUM> keV and equal to or less than <NUM> keV, as an image evaluation pattern simulating a contrast medium using iodine is irradiated with radiation having a first energy from the mammography apparatus and a first radiographic image is captured by a radiation detector; a step in which the phantom is irradiated with radiation having a second energy greater than the first energy and a second radiographic image is captured by the radiation detector; and a step of generating a third radiographic image in which the solid material is emphasized from the first radiographic image and the second radiographic image.

An evaluation method of a fourteenth aspect of the present disclosure is an evaluation method for a mammography apparatus, and comprises: a step in which a phantom for evaluation of the mammography apparatus having a solid material containing at least one element, which has an atomic number of <NUM> to <NUM>, as an image evaluation pattern simulating a contrast medium using iodine is irradiated with radiation having a first energy from the mammography apparatus and a first radiographic image is captured by a radiation detector; a step in which the phantom is irradiated with radiation having a second energy greater than the first energy and a second radiographic image is captured by the radiation detector; and a step of generating a third radiographic image in which the solid material is emphasized from the first radiographic image and the second radiographic image.

According to the present disclosure, an effect is obtained that the convenience in evaluating the contrast imaging function of the mammography apparatus can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying diagrams. In addition, the present embodiment does not limit the present invention.

First, an example of the overall configuration of a radiographic image capturing system of the present embodiment will be described. In <FIG>, a configuration diagram showing an example of the overall configuration of a radiographic image capturing system <NUM> of the present embodiment is shown.

The radiographic image capturing system <NUM> of the present embodiment has a function of capturing a radiographic image by the operation of a user, such as a doctor or a radiology technician, based on an instruction (imaging order) input from an external system (for example, a radiology information system (RIS)) through the console <NUM>.

As shown in <FIG>, the radiographic image capturing system <NUM> of the present embodiment comprises a console <NUM>, a mammography apparatus <NUM>, and a phantom <NUM>. In <FIG>, a block diagram showing an example of the configuration of the console <NUM> and the mammography apparatus <NUM> of the present embodiment is shown.

The console <NUM> of the present embodiment has a function of controlling the mammography apparatus <NUM> using the imaging order or various kinds of information acquired from an external system or the like through a wireless communication local area network (LAN) or the like.

The console <NUM> of the present embodiment is a server computer as an example. As shown in <FIG>, the console <NUM> comprises a controller <NUM>, a storage unit <NUM>, an interface (I/F) unit <NUM>, a display unit driving unit <NUM>, a display unit <NUM>, an operation input detection unit <NUM>, and an operation unit <NUM>. The controller <NUM>, the storage unit <NUM>, the I/F unit <NUM>, the display unit driving unit <NUM>, and the operation input detection unit <NUM> are connected to each other through a bus <NUM>, such as a system bus or a control bus, so that various kinds of information can be transmitted and received therebetween.

The controller <NUM> of the present embodiment controls the overall operation of the console <NUM>. The controller <NUM> of the present embodiment comprises a central processing unit (CPU) 70A, a read only memory (ROM) 70B, and a random access memory (RAM) 70C. Various programs including an image evaluation processing program to be described later, which are executed by the CPU 70A, are stored in advance in the ROM 70B. The RAM 70C temporarily stores various kinds of data.

Image data of a radiographic image captured by the mammography apparatus <NUM>, other various kinds of information, and the like are stored in the storage unit <NUM>. In addition, the evaluation result of the mammography apparatus <NUM>, which will be described in detail later, is stored in the storage unit <NUM> of the present embodiment. As specific examples of the storage unit <NUM>, a hard disk drive (HDD), a solid state drive (SSD), and the like can be mentioned. The I/F unit <NUM> communicates with an external system, such as the mammography apparatus <NUM> or the RIS, by wireless communication or wired communication to transmit and receive various kinds of information therebetween.

The display unit <NUM> displays various kinds of information. The display unit driving unit <NUM> controls display of various kinds of information on the display unit <NUM>. The operation unit <NUM> is used by the user to input various kinds of information, instructions regarding radiographic image capturing including a radiation R exposure instruction, and the like. The operation unit <NUM> is not particularly limited, and examples thereof include various switches, a touch panel, a touch pen, and a mouse. In addition, the operation unit <NUM> and the display unit <NUM> may be integrated to form a touch panel display. The operation input detection unit <NUM> detects an operation state with respect to the operation unit <NUM>.

On the other hand, the mammography apparatus <NUM> of the present embodiment is an apparatus that captures a radiographic image of a breast as a subject by emitting radiation R (X-rays) to the breast of the subject. In addition, the mammography apparatus <NUM> may be an apparatus that images the breast of the subject not only in a state in which the subject is standing (standing state) but also in a state in which the subject is sitting on a chair (including a wheelchair) or the like (sitting state), and may be any apparatus capable of capturing at least a radiographic image of the breast of the subject.

In addition, the mammography apparatus <NUM> of the present embodiment has a contrast enhanced digital mammography (CEDM) function for performing contrast imaging by energy subtraction imaging as a function of performing imaging in a state in which a contrast medium is administered to the breast of the subject, so-called contrast imaging.

As shown in <FIG>, the mammography apparatus <NUM> of the present embodiment comprises a radiation detector <NUM>, a radiation emission unit <NUM> having a radiation source <NUM>, a controller <NUM>, a storage unit <NUM>, an I/F unit <NUM>, and an operation panel <NUM>. The radiation detector <NUM>, the radiation emission unit <NUM>, the controller <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, so that various kinds of information can be transmitted and received therebetween.

The controller <NUM> of the present embodiment controls the overall operation of the mammography apparatus <NUM>. In addition, the controller <NUM> of the present embodiment controls the radiation detector <NUM> and the radiation emission unit <NUM> in the case of capturing a radiographic image. The controller <NUM> of the present embodiment comprises a CPU 60A, a ROM 60B, and a RAM 60C. Various programs including an imaging processing program to be described later, which are executed by the CPU 60A, are stored in advance in the ROM 60B. The RAM 60C temporarily stores various kinds of data.

Image data of a radiographic image captured by the radiation detector <NUM>, other various kinds of information, and the like are stored in the storage unit <NUM>. As specific examples of the storage unit <NUM>, an HDD, an SSD, and the like can be mentioned. The I/F unit <NUM> communicates with the console <NUM> by wireless communication or wired communication to transmit and receive various kinds of information therebetween. The operation panel <NUM> is provided as a plurality of switches on an imaging table <NUM> of the mammography apparatus <NUM>, for example. In addition, the operation panel <NUM> may be provided as a touch panel.

In <FIG>, a configuration diagram showing an example of the overall configuration of the mammography apparatus <NUM> of the present embodiment is shown. The following description will be given on the assumption that the side closer to the subject (chest wall side) in a case where the subject faces the mammography apparatus <NUM> in radiographic image capturing is the front side of the mammography apparatus <NUM> and the side away from the subject is the rear side of the mammography apparatus <NUM>. In addition, the description will be given on the assumption that the left-right direction of the subject in a case where the subject faces the mammography apparatus <NUM> is the left-right direction of the mammography apparatus <NUM>. In addition, the description will be given on the assumption that the head direction of the subject in a case where the subject faces the mammography apparatus <NUM> is the upper side and the foot direction is the lower side.

As shown in <FIG>, the mammography apparatus <NUM> comprises an imaging unit <NUM>, which has an approximately C shape in a side view and is provided on the front side of the apparatus, and a base unit <NUM> that supports the imaging unit <NUM> from the rear side of the apparatus.

The imaging unit <NUM> comprises the imaging table <NUM> having a planar imaging surface <NUM> in contact with the breast of the subject, a compression plate <NUM> for compressing the breast interposed between the compression plate <NUM> and the imaging surface <NUM> of the imaging table <NUM>, and a holding unit <NUM> that supports the imaging table <NUM> and the compression plate <NUM>. A member that transmits the radiation R is used as the compression plate <NUM>. The imaging unit <NUM> comprises a support unit <NUM> that supports the radiation source <NUM> and the radiation emission unit <NUM>, and the support unit <NUM> is separated from the holding unit <NUM>.

As shown in <FIG>, the radiation source <NUM> comprising a tube (tungsten as an example in the present embodiment) for emitting the radiation R to the breast is provided inside the radiation emission unit <NUM> of the mammography apparatus <NUM> of the present embodiment. In the radiation emission unit <NUM>, a rhodium (Rh) filter <NUM> and a copper (Cu) filter <NUM> are provided between the radiation source <NUM> and the imaging table <NUM>. In <FIG>, the Rh filter <NUM> and the Cu filter <NUM> are shown as being integrated, but the filters are provided as separate filters.

The filters provided in the mammography apparatus <NUM> are not limited to the Rh filter <NUM> and the Cu filter <NUM>. For example, a molybdenum (Mo) filter may be provided instead of the Rh filter <NUM> or in addition to the Rh filter <NUM>. In addition, for example, an aluminum (Al) filter has a lower radiation R attenuation rate than the Rh filter <NUM>. Therefore, the Al filter is suitable for tomosynthesis imaging in which the imaging time (radiation R emission time) at each imaging position in a state in which the radiation source <NUM> is continuously moved is short. For this reason, in a case where the mammography apparatus <NUM> has a function of performing tomosynthesis imaging, an Al filter may be provided and tomosynthesis imaging may be performed using the Al filter.

A moving unit (not shown) is provided inside the radiation emission unit <NUM>. In the case of capturing a radiographic image, the Rh filter <NUM> or the Cu filter <NUM> is moved to a position in the irradiation field according to the energy of the radiation R to be emitted.

On the other hand, a shaft (not shown) is provided in the imaging unit <NUM> of the present embodiment, so that the imaging unit <NUM> can rotate with respect to the base unit <NUM>. The shaft is fixed to the support unit <NUM>, so that the shaft and the support unit <NUM> rotate together. A gear is provided in each of the holding unit <NUM> and the shaft provided in the imaging unit <NUM>. By switching the engagement state and the non-engagement state of the gears, it is possible to perform switching between a state in which the holding unit <NUM> and the shaft are connected to each other to rotate together and a state in which the shaft is separated from the holding unit <NUM> and idles. In addition, switching between transmission and non-transmission of the power of the shaft is not limited to the gear, and various mechanical elements can be used.

The holding unit <NUM> supports the imaging table <NUM> and the radiation source <NUM> by separating the imaging surface <NUM> and the radiation source <NUM> from each other by a predetermined distance. In addition, the holding unit <NUM> also holds the compression plate <NUM> through a support arm <NUM>. The holding unit <NUM> makes the support arm <NUM> slide so that the compression plate <NUM> moves, and accordingly, the distance between the compression plate <NUM> and the imaging surface <NUM> changes.

The imaging surface <NUM> with which the breast of the subject comes into contact is formed of, for example, carbon from the viewpoint of radiolucency or strength. The radiation detector <NUM> that detects the radiation R transmitted through the breast and the imaging surface <NUM> is disposed in the imaging table <NUM>. A radiographic image is generated based on the radiation R detected by the radiation detector <NUM>. The type of the radiation detector <NUM> of the present embodiment is not particularly limited. For example, an indirect conversion type radiation detector that converts the radiation R into light and converts the converted light into electric charge may be used, or a direct conversion type radiation detector that converts the radiation R into electric charge may be used. In the present embodiment, image data indicating a radiographic image output from the radiation detector <NUM> of the mammography apparatus <NUM> is transmitted to the console <NUM>.

As described above, the mammography apparatus <NUM> of the present embodiment has a function of performing contrast imaging. As a contrast medium used for contrast imaging, a contrast medium using iodine having a k absorption edge of <NUM> keV (hereinafter, simply referred to as a "contrast medium") is generally used. The mammography apparatus <NUM> captures a first radiographic image with the radiation detector <NUM> by emitting the radiation R having a first energy lower than the k absorption edge of the contrast medium to the breast as a subject to which the contrast medium has been administered, and captures a second radiographic image with the radiation detector <NUM> by emitting the radiation R having a second energy higher than the k absorption edge of the contrast medium to the breast as a subject to which the contrast medium has been administered.

In the mammography apparatus <NUM> of the present embodiment, emitting the radiation R having the first energy refers to emitting the radiation R from the radiation source <NUM> by applying a tube voltage of the first energy. Similarly, emitting the radiation R having the second energy refers to emitting the radiation R from the radiation source <NUM> by applying a tube voltage of the second energy.

The specific first energy and second energy are determined from the viewpoint of the specifications of the mammography apparatus <NUM>, the desired image quality of the radiographic image, exposure of the subject, and the like in addition to the k absorption edge of the contrast medium. In general, the specific first energy and second energy are preferably <NUM> keV to <NUM> keV. In other words, it is preferable that the first energy is equal to or greater than <NUM> keV and less than the value of the k absorption edge of the contrast medium. In addition, it is preferable that the second energy is greater than the value of the k absorption edge of the contrast medium and equal to or less than <NUM> keV.

In the mammography apparatus <NUM> of the present embodiment, the first energy is the same as the energy of the radiation R used for normal (general) imaging. In the mammography apparatus <NUM>, in the case of performing imaging by emitting the radiation R having the first energy (hereinafter, referred to as "first imaging"), the Rh filter <NUM> is disposed in the irradiation field. Since the k absorption edge of Rh is <NUM> keV, the quality of the radiation R emitted to the subject is a radiation quality in which an energy component of <NUM> keV or more is suppressed.

In the mammography apparatus <NUM> of the present embodiment, the second energy is set in the range of <NUM> keV to <NUM> keV. In the mammography apparatus <NUM>, in the case of performing imaging by emitting the radiation R having the second energy (hereinafter, referred to as "second imaging"), the Cu filter <NUM> is disposed in the irradiation field. The k absorption edge of Cu is as low as <NUM> keV. However, by setting the thickness appropriately, the quality of the radiation R emitted to the subject can be made to be a radiation quality in which the first energy component of the radiation R is suppressed.

The first radiographic image captured by the first imaging and the second radiographic image captured by the second imaging are output to the console <NUM>, and the console <NUM> calculates the concentration distribution of the contrast medium from the difference between the pieces of image data of the first radiographic image and the second radiographic image and images the contrast medium. Specifically, the controller <NUM> of the console <NUM> of the present embodiment generates image data of a difference image, in which the human body structure is suppressed and the administered contrast medium is emphasized, by subtracting image data, which is obtained by multiplying the image data of the first radiographic image by a first coefficient set in advance, from image data, which is obtained by multiplying the image data of the second radiographic image by a second coefficient set in advance. The difference image generation method of the controller <NUM> is not limited thereto, and a known difference image generation method can be used. The difference image generated by the mammography apparatus <NUM> of the present embodiment is an example of a third radiographic image of the present disclosure.

On the other hand, the phantom <NUM> of the present embodiment is used to evaluate the mammography apparatus <NUM> by evaluating the quality of a radiographic image based on desired image quality evaluation items. As an example, the phantom <NUM> of the present embodiment is applied to the method of international electrotechnical commission (IEC) and the method of European reference organization for quality assured breast screening and diagnostic services (EUREF). Specifically, the phantom <NUM> of the present embodiment additionally has a function of evaluating the detectability of a contrast medium image. <FIG> shows a plan view in a case where an example of the phantom <NUM> of the present embodiment is viewed from the radiation source <NUM> side.

As shown in <FIG>, the phantom <NUM> of the present embodiment has an image evaluation pattern <NUM> and an image evaluation pattern <NUM> that are used for the evaluation of the detectability of a contrast medium image (hereinafter, simply referred to as "detectability of a contrast medium"). By including the image evaluation pattern <NUM> and the image evaluation pattern <NUM>, image quality evaluation items of the phantom <NUM> of the present embodiment includes the detectability of the contrast medium.

In addition, although details will be described later, the image evaluation pattern <NUM> is also used for the evaluation of the contrast to noise ratio (CNR), which is one of the image quality evaluation items. In addition, although details will be described later, the image evaluation pattern <NUM> includes a plurality of disks <NUM>, and is also used for the evaluation of the low contrast detectability (LCD), which is one of the image quality evaluation items.

In order to be used for the evaluation of the detectability of the contrast medium, the image evaluation pattern <NUM> and the image evaluation pattern <NUM> are formed as solid materials each having a predetermined size, shape, and density, which simulates a contrast medium, on a substrate formed of plastic (hereinafter referred to as a "plastic substrate"), such as poly ethylene terephthalate (PET) or polycarbonate. In the present embodiment, the "solid material" means that the shape does not change according to the shape of a container in which the solid is housed and the shape does not change with time.

The phantom <NUM> of the present embodiment has, as the image evaluation pattern <NUM> and the image evaluation pattern <NUM> simulating a contrast medium, a solid material containing at least one element having a k absorption edge within the range of the first energy to the second energy of the radiation R emitted from the radiation source <NUM>.

In other words, in the phantom <NUM> of the present embodiment, the image evaluation pattern <NUM> and the image evaluation pattern <NUM> are formed as solid materials simulating a contrast medium by a material containing at least one element having a k absorption edge that is greater than the k absorption edge of the Rh filter <NUM> used in the first imaging, in which the radiation R having the first energy is emitted, and smaller than the peak energy of the radiation R in the second imaging.

Examples of this type of element include elements ranging from Rh having an atomic number of <NUM> and a k absorption edge of <NUM> keV to barium (Ba) having an atomic number of <NUM> and a k absorption edge of <NUM> keV. As for which of these elements is used, it is possible to appropriately use an element by which the image evaluation pattern <NUM> and an image evaluation pattern <NUM> can be easily formed (processed) in desired shapes and the like.

Examples of the solid material using this kind of element include a tin foil formed of Sn having an atomic number of <NUM> and a k absorption edge of <NUM> keV, not forming part of the present invention, and an indium tin oxide (ITO) film formed of Sn and indium (In) having an atomic number of <NUM> and a k absorption edge of <NUM> keV.

In a case where the solid material is a tin foil, the image evaluation pattern <NUM> and the image evaluation pattern <NUM> can be formed on a plastic substrate by machining. For example, the image evaluation pattern <NUM> is formed in a rectangular shape having a thickness of <NUM> and a side of <NUM>. In addition, for example, in the image evaluation pattern <NUM>, the disk <NUM> is formed in a circular shape having a thickness of <NUM> and a diameter of <NUM>.

On the other hand, in a case where the solid material is an ITO film, the image evaluation pattern <NUM> and the image evaluation pattern <NUM> can be formed on a plastic substrate using any method, such as vapor deposition, sputtering, and fine particle coating. For example, the image evaluation pattern <NUM> is formed in a rectangular shape having a thickness of <NUM> and a side of <NUM>. In addition, for example, in the image evaluation pattern <NUM>, the disk <NUM> is formed in a circular shape having a thickness of <NUM> and a diameter of <NUM>. In addition, since the ITO film as the image evaluation pattern <NUM> and the image evaluation pattern <NUM> does not require transparency unlike in the case of being used as a transparent electrode, the film forming conditions are relatively loose and no heat treatment is required. Therefore, it is easy to increase the thickness of the ITO film, and it is possible to easily form a film on a plastic substrate.

The thickness of the image evaluation pattern <NUM> and the image evaluation pattern <NUM>, specifically, the thickness in an incidence direction in which the radiation R is incident is determined according to the concentration of the contrast medium to be simulated, and the thickness in the incidence direction increases as the concentration of the contrast medium increases.

The phantom <NUM> of the present embodiment has image evaluation patterns for evaluating other desired image quality evaluation items. For example, as shown in <FIG>, the phantom <NUM> has an image evaluation pattern <NUM> used for the evaluation of a dynamic range, an image evaluation pattern <NUM> used for the evaluation of linearity, and an image evaluation pattern <NUM> used for the evaluation of spatial resolution (SR).

Although details are omitted, the phantom <NUM> shown in <FIG> can further evaluate, for example, chest wall defect, system sensitivity invariance, geometric distortion, image unevenness (system artifact), and image uniformity as other desired image quality evaluation items, and has respective image evaluation patterns.

Next, an operation for evaluating the mammography apparatus <NUM> (hereinafter, referred to as an "evaluation operation") in the radiographic image capturing system <NUM> of the present embodiment will be described. <FIG> shows a flowchart showing an example of the flow of the entire evaluation operation by the radiographic image capturing system <NUM> of the present embodiment.

First, in step S100, the user places the phantom <NUM> as a subject at a certain position on the imaging surface <NUM> of the imaging table <NUM> of the mammography apparatus <NUM>. Then, in the next step S102, the user places the compression plate <NUM> on the phantom <NUM>.

In the next step S104, the user gives an instruction to start capturing a radiographic image from the operation unit <NUM> of the console <NUM>. The instruction to start imaging (imaging start instruction) is transmitted to the mammography apparatus <NUM> through the I/F unit <NUM>. In the radiographic image capturing system <NUM> of the present embodiment, the imaging order is also transmitted from the console <NUM> to the mammography apparatus <NUM> through the I/F unit <NUM>.

In the next step S106, the mammography apparatus <NUM> performs imaging processing shown as an example in <FIG> to capture a radiographic image of the phantom <NUM>. Thus, in the mammography apparatus <NUM> of the present embodiment, in a case where the imaging order and the instruction to start capturing a radiographic image are received from the console <NUM>, the CPU 60A of the controller <NUM> executes an imaging processing program stored in the ROM 60B, thereby performing the imaging processing shown in <FIG>.

As shown in <FIG>, in step S150, the controller <NUM> of the mammography apparatus <NUM> emits the radiation R having a first energy from the radiation source <NUM>. In the next step S152, the controller <NUM> performs the first imaging by capturing the first radiographic image with the radiation detector <NUM>. In the present embodiment, the Rh filter <NUM> is disposed in the irradiation field in a state in which the imaging processing has started, at least in the case of performing the first imaging.

In steps S150 and S152, the radiation R having the first energy is emitted to the phantom <NUM>, and image data indicating the first radiographic image generated by the radiation detector <NUM> according to the radiation R transmitted through the phantom <NUM> is output from the mammography apparatus <NUM> to the console <NUM>.

In the next step S154, the controller <NUM> moves the Rh filter <NUM> and the Cu filter <NUM> to locate the Cu filter <NUM> in the irradiation field. In addition, the controller <NUM> changes a tube voltage applied to the radiation source <NUM> so as to be increased from the tube voltage in the case of emitting the first energy to the tube voltage in the case of emitting the second energy.

In the next step S156, the controller <NUM> emits the radiation R having a second energy from the radiation source <NUM>. In the next step S158, the controller <NUM> performs the second imaging by capturing the second radiographic image with the radiation detector <NUM>, and ends this imaging processing. In steps S156 and S158, the radiation R having the second energy is emitted to the phantom <NUM>, and image data indicating the second radiographic image generated by the radiation detector <NUM> according to the radiation R transmitted through the phantom <NUM> is output from the mammography apparatus <NUM> to the console <NUM>. Hereinafter, in a case where various radiographic images, such as the first radiographic image and the second radiographic image, are collectively called, these will be referred to as "radiographic images".

In a case where image data indicating a radiographic image captured by imaging processing is input from the mammography apparatus <NUM>, the console <NUM> temporarily stores the input image data indicating the radiographic image in the storage unit <NUM>.

In a case where the imaging processing of the mammography apparatus <NUM> in step S106 is ended as described above, the controller <NUM> of the console <NUM> generates a difference image from the first radiographic image and the second radiographic image and displays the difference image on the display unit <NUM> in the next step S108. Here, the method of generating a difference image is the same as a method of generating a difference image in the case of performing normal contrast imaging in a case where the breast in a state in which a contrast medium is administered is a subject. The controller <NUM> of the present embodiment is an example of a generation unit of the present disclosure.

Specifically, first, the controller <NUM> acquires image data indicating the first radiographic image and image data indicating the second radiographic image from the storage unit <NUM>. Then, the controller <NUM> generates image data of a difference image by subtracting image data, which is obtained by multiplying the image data indicating the first radiographic image by a first coefficient set in advance, from image data, which is obtained by multiplying the image data indicating the second radiographic image by a second coefficient set in advance, for each corresponding pixel. The difference image generation method of the controller <NUM> is not limited thereto, and a known difference image generation method can be used.

In the next step S110, the controller <NUM> evaluates the generated difference image. The difference image evaluation method is not particularly limited, but an evaluation value CNR for evaluating the contrast to noise ratio using the image evaluation pattern <NUM> is obtained by the following Equation (<NUM>). In the following Equation (<NUM>), the average pixel value of the image of the image evaluation pattern <NUM> (100A) is mAL, the standard deviation is σAL, the average pixel value of the image of the image evaluation pattern <NUM> (100B) is mBG, and the standard deviation is σBG. [Equation <NUM>] <MAT>.

In the radiographic image capturing system <NUM> of the present embodiment, the controller <NUM> derives the evaluation value CNR based on the image data of the difference image using the above Equation (<NUM>).

In addition, the LCD score for evaluating the low contrast detectability using the image evaluation pattern <NUM> is derived by a dot pattern (LCD pattern) formed in the difference image by the disk <NUM>. In the difference image of the embodiment, white and black LCD patterns are formed by the disk <NUM> of the image evaluation pattern <NUM>. The controller <NUM> digitizes the LCD score by deriving a function of cross correlation with the LCD pattern of the difference image using an ideal LCD pattern in a case where no noise is generated.

In the present embodiment, the CPU 70A executes an image evaluation processing program stored in the ROM 70B of the controller <NUM>, so that the evaluation value CNR is derived and the LCD score is derived. In addition, the CPU 70A executes the image evaluation processing program, so that the controller <NUM> functions as an example of an evaluation unit of the present disclosure.

In addition, the detectability of the contrast medium by the image evaluation pattern <NUM> and the image evaluation pattern <NUM> in the radiographic image capturing system <NUM> of the present embodiment is evaluated based on the visual recognition result (visibility) of the user who views the difference image. Information indicating the evaluation based on the visual recognition result is input to the console <NUM> of the present embodiment by the user.

In the next step S112, the controller <NUM> displays the evaluation result of the difference image obtained in the above step S110 on the display unit <NUM>. The console <NUM> of the present embodiment stores the evaluation result in the storage unit <NUM>. In the radiographic image capturing system <NUM> of the present embodiment, the evaluation operation ends in a case where step S112 ends.

In the present embodiment, the configuration and the operation are the same except that the phantom <NUM> provided in the radiographic image capturing system <NUM> is different from the phantom <NUM> (refer to <FIG>) of the first embodiment. Accordingly, the phantom <NUM> of the present embodiment will be described with the detailed description being omitted.

As described above, the phantom <NUM> of the first embodiment additionally has a function of evaluating the detectability of the contrast medium image. On the other hand, the phantom <NUM> of the present embodiment additionally has a function of visually evaluating the detectability of the contrast medium image. <FIG> shows a plan view in a case where an example of the phantom <NUM> of the present embodiment is viewed from the radiation source <NUM> side.

As shown in <FIG>, the phantom <NUM> of the present embodiment has an image evaluation pattern <NUM>, an image evaluation pattern <NUM>, and an image evaluation pattern <NUM> that are used for the evaluation of the detectability of the contrast medium. By including the image evaluation pattern <NUM>, the image evaluation pattern <NUM>, and the image evaluation pattern <NUM>, image quality evaluation items of the phantom <NUM> of the present embodiment includes the detectability of the contrast medium.

The image evaluation pattern <NUM> is also used for the evaluation of the detectability of a fiber structure (fiber), which is one of the image quality evaluation items. Therefore, the image evaluation pattern <NUM> includes a plurality of test objects having different sizes simulating a fiber structure. In the present embodiment, in order to be used for the evaluation of the detectability of the contrast medium, as an example, the image evaluation pattern <NUM> is created by molding a resin kneaded with barium sulfate powder as a solid material having a shape simulating a fiber structure with a desired size. The amount of barium sulfate kneaded into the resin (the content of barium sulfate) is determined according to the concentration of the contrast medium to be simulated, and the content of barium sulfate increases as the concentration of the contrast medium increases.

In addition, the image evaluation pattern <NUM> is also used for the evaluation of the detectability of microcalcification (calc), which is one of the image quality evaluation items. Therefore, the image evaluation pattern <NUM> includes a plurality of test objects having different sizes simulating a microcalcification. In the present embodiment, in order to be used for the evaluation of the detectability of the contrast medium, as an example, the image evaluation pattern <NUM> is created by molding a resin kneaded with barium sulfate powder as a solid material having a shape simulating a microcalcification with a desired size.

In addition, the image evaluation pattern <NUM> is also used for the evaluation of the detectability of a mass, which is one of the image quality evaluation items. Therefore, the image evaluation pattern <NUM> includes a plurality of test objects having different sizes simulating a mass. In the present embodiment, in order to be used for the evaluation of the detectability of the contrast medium, as an example, the image evaluation pattern <NUM> is created by molding and sintering barium sulfate powder into a solid material having a shape simulating a mass with a desired size.

The image evaluation pattern <NUM>, the image evaluation pattern <NUM>, and the image evaluation pattern <NUM> are built into a wax simulating the compressed breast.

The flow of the entire evaluation operation of the mammography apparatus <NUM> using the phantom <NUM> of the present embodiment is the same as the flow of the entire evaluation operation (refer to <FIG>) of the first embodiment. Needless to say, in the evaluation of the difference image in step S110 in the flow of the entire evaluation operation, evaluation according to the image evaluation pattern <NUM>, the image evaluation pattern <NUM>, and the image evaluation pattern <NUM> is performed.

Specifically, the detectability of the contrast medium in a case where the phantom <NUM> of the present embodiment is evaluated based on the visual recognition result (visibility) of the user who views the difference image. In addition, the detectability of the fiber structure, the mass, and the microcalcification is also evaluated based on the visual recognition result (visibility) of the user who views the difference image.

In the present embodiment, the form has been described in which each of the image evaluation pattern <NUM>, the image evaluation pattern <NUM>, and the image evaluation pattern <NUM> is used for the evaluation of the detectability of the contrast medium. However, any one or more image evaluation patterns may be used for the evaluation of the detectability of the contrast medium. For example, the image evaluation pattern <NUM> may be used for the evaluation of the detectability of the microcalcification and the detectability of the contrast medium, and the image evaluation pattern <NUM> and the image evaluation pattern <NUM> may be respectively used only for the evaluation of the detectability of the fiber structure and the detectability of the mass.

As described above, the radiographic image capturing system <NUM> of each of the embodiments described above comprises the mammography apparatus <NUM> that emits the radiation R having the first energy to the subject and captures a first radiographic image with the radiation detector <NUM> and emits the radiation R having the second energy greater than the first energy to the subject and captures a second radiographic image with the radiation detector <NUM> and that captures the first radiographic image and the second radiographic image with the breast in a state in which a contrast medium using iodine is administered. In addition, the radiographic image capturing system <NUM> comprises the phantom <NUM> for evaluation of the mammography apparatus <NUM> that has a solid material containing at least one element, which has a value of the k absorption edge that is equal to or greater than the first energy and equal to or less than the second energy, as an image evaluation pattern simulating the contrast medium.

In other words, for the phantom <NUM>, the radiographic image capturing system <NUM> of each of the above embodiments comprises the phantom <NUM> for the evaluation of the mammography apparatus <NUM> having a solid material, which contains at least one element having an atomic number of <NUM> to <NUM>, as an image evaluation pattern simulating a contrast medium.

As described above, the phantom <NUM> of each of the above embodiments has a solid material containing an element based on the k absorption edge of iodine as an image evaluation pattern simulating a contrast medium. For example, in the case of evaluating the contrast imaging function of the mammography apparatus <NUM> using a phantom into which a liquid contrast medium is injected as in the conventional technique, there may be a procedure in which a prepared liquid contrast medium is injected into a desired position in the phantom, a radiographic image is then captured with the phantom as a subject, and then the injected contrast medium is discarded. In this case, the amount of contrast medium into the phantom may vary. In addition, the user may feel bothersome due to a plurality of time-consuming steps.

In contrast, in the phantom <NUM> of the present embodiment, as described above, the image evaluation pattern simulating a contrast medium is a solid material, and can be built into the phantom. Therefore, it is possible to improve the convenience in evaluating the contrast imaging function of the mammography apparatus <NUM>.

In addition, since the phantom <NUM> of the present embodiment can add the evaluation of the contrast imaging function to the image evaluation pattern used for the evaluation of image quality evaluation items different from the evaluation of the contrast imaging function, it is possible to evaluate a larger number of image quality evaluation items with one phantom <NUM>.

It is needless to say that the elements contained in the solid material, which is an image evaluation pattern simulating the contrast medium contained in the phantom <NUM>, and the manufacturing method are not limited to those in the above-described embodiments and can be changed depending on the situation without departing from the gist of the present invention.

For example, as in a phantom <NUM> shown in <FIG>, a sheet <NUM> formed by molding a resin kneaded with barium sulfate powder may be disposed on the phantom <NUM> (on the radiation source <NUM> side). <FIG> shows a side view as seen from a direction crossing the incidence direction of the radiation R. In the phantom <NUM> shown in <FIG>, the thickness of the sheet <NUM> in the incidence direction of the radiation R is set to a plurality of thicknesses (thicknesses L1, L2, and L3) according to the concentration of the contrast medium.

The imaging processing or the image quality evaluation processing executed in a case where the CPU executes software (program) in each of the embodiments described above may be executed by various processors other than the CPU. As processors in this case, a programmable logic device (PLD) whose circuit configuration can be changed after manufacture, such as a field-programmable gate array (FPGA), and a dedicated electric circuit that is a processor having a dedicated circuit configuration for executing specific processing, such as an application specific integrated circuit (ASIC), are exemplified. The imaging processing or the image quality evaluation processing may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same type or different types (for example, a plurality of FPGAs and a combination of a CPU and an FPGA). More specifically, the hardware structure of these various processors is an electric circuit in which circuit elements, such as semiconductor elements, are combined.

Claim 1:
A radiographic image capturing system (<NUM>), comprising:
a mammography apparatus (<NUM>) adapted to emit radiation having a first energy to a subject and to capture a first radiographic image with a radiation detector (<NUM>) and to emit radiation having a second energy greater than the first energy to the subject and to capture a second radiographic image with the radiation detector (<NUM>); wherein the first radiographic image and the second radiographic image are captured with a breast in a state in which a contrast medium using iodine is administered; and
a phantom (<NUM>) for evaluation of the mammography apparatus that has a solid material as an image evaluation pattern (<NUM>, <NUM>, <NUM>, <NUM>) simulating the contrast medium,
characterized in that the solid material is an indium tin oxide (ITO) film formed of Sn and In.