Patent Description:
Tomosynthesis imaging has been known which irradiates an object with radiation at a plurality of different irradiation angles in order to generate a tomographic image in any tomographic plane of the object. <CIT> discloses a tomosynthesis imaging apparatus that performs tomosynthesis imaging using a radiation source in which a plurality of focuses where radiation is emitted are arranged. The tomosynthesis imaging apparatus disclosed in <CIT> has an irradiation field limiter in which irradiation openings for radiation which define the irradiation field of radiation are formed so as to correspond to each of a plurality of focuses. <CIT> is concerned with radiographic imaging and discloses a collimator having a number of apertures movable to either a first or second position in a path of a radiation source array. <CIT> is concerned with directed x-ray fields for tomosynthesis.

The inventors have studied a technique in which three or more radiation tubes, each of which has one or more focuses, are used and adjacent radiation tubes are brought close to each other to improve the signal-noise (SN) ratio of a tomographic image. In this configuration, in a case in which an irradiation field limiter having irradiation openings formed so as to correspond to each of a plurality of radiation tubes is applied and radiation is emitted from a certain radiation tube, the radiation leaks from the irradiation openings corresponding to adjacent radiation tubes, which may cause unnecessary exposure.

An object of the technology of the present disclosure is to provide a tomosynthesis imaging apparatus that can prevent unnecessary exposure.

In order to achieve the above object, according to an aspect, there is provided a tomosynthesis imaging apparatus according to claim <NUM>.

Preferably, the plate-like member is moved in a direction in which an interval between the radiation tube and the through hole changes.

Preferably, the irradiation field limiter has a configuration in which plate-like members, in which a through hole at least one side of which functions as an opening edge of the irradiation opening is formed, are stacked in a direction normal to an imaging surface of a radiation detector that detects the radiation and outputs a radiographic image, and each of a plurality of the plate-like members is moved along the arrangement direction of the radiation tubes to move the position of the irradiation openings to the at least two set positions.

Preferably, the irradiation field limiter has one actuator that moves two of the plate-like members, which are adjacent to each other in a stacking direction, along the arrangement direction of the radiation tubes at the same time.

Preferably, the irradiation field limiter includes a sheet-like member in which a through hole functioning as the irradiation opening is formed and the sheet-like member is sent along the arrangement direction of the radiation tubes and is rolled to move the irradiation opening.

Preferably, a plurality of types of the through holes having different sizes are formed in the sheet-like member.

Preferably, the irradiation field limiter includes a plate-like member in which a through hole functioning as the irradiation opening is formed and the plate-like member is rotated about a rotating shaft which is provided between the radiation tube and an imaging surface of a radiation detector that detects the radiation and outputs a radiographic image to move the irradiation opening to the at least two set positions.

Preferably, the irradiation field limiter has an adjustment member that adjusts a width of the plurality of irradiation openings and the adjustment member is moved in a direction intersecting the arrangement direction of the radiation tubes to adjust the width of the plurality of irradiation openings at once.

Preferably, a plurality of the radiation tubes are arranged at equal intervals in a linear shape or an arc shape.

According to the technique of the present disclosure, it is possible to provide a tomosynthesis imaging apparatus that can prevent unnecessary exposure.

In <FIG> and <FIG>, a mammography apparatus <NUM> is an example of a "tomosynthesis imaging apparatus" according to the technique of the present disclosure and a breast M of a subject H is an object. The mammography apparatus <NUM> irradiates the breast M with radiation <NUM> (see, for example, <FIG>), such as X-rays or γ-rays, to capture a radiographic image of the breast M.

The mammography apparatus <NUM> includes an apparatus main body <NUM> and a control device <NUM>. The apparatus main body <NUM> is installed, for example, in a radiography room of a medical facility. The control device <NUM> is installed, for example, in a control room next to the radiography room. The control device <NUM> is, for example, a desktop personal computer. The control device <NUM> is connected to an image database (hereinafter, referred to as a DB) server <NUM> through a network <NUM>, such as a local area network (LAN), such that it can communicate with the image DB server <NUM>. The image DB server <NUM> is, for example, a picture archiving and communication system (PACS) server, receives a radiographic image from the mammography apparatus <NUM>, stores the radiographic image, and manages the radiographic image.

A terminal apparatus <NUM> is also connected to the network <NUM>. The terminal apparatus <NUM> is, for example, a personal computer that is used by a doctor to make a diagnosis based on the radiographic image. The terminal apparatus <NUM> receives the radiographic image from the image DB server <NUM> and displays the radiographic image on a display.

The apparatus main body <NUM> includes a stand <NUM> and an arm <NUM>. The stand <NUM> includes a pedestal 20A that is provided on the floor of the radiography room and a support 20B that extends from the pedestal 20A in a height direction. The arm <NUM> has a substantially C-shape in a side view and is connected to the support 20B through a connection portion 21A. The arm <NUM> can be moved with respect to the support 20B in the height direction by the connection portion 21A and the height of the arm <NUM> can be adjusted according to the height of the subject H by the connection portion 21A. In addition, the arm <NUM> is rotatable on a rotating shaft perpendicular to the support 20B through the connection portion 21A.

The arm <NUM> includes a radiation source accommodation portion <NUM>, a detector accommodation portion <NUM>, and a main body portion <NUM>. The radiation source accommodation portion <NUM> accommodates a radiation source <NUM>. The detector accommodation portion <NUM> accommodates a radiation detector <NUM>. In addition, the detector accommodation portion <NUM> functions as an imaging table on which the breast M is placed. The main body portion <NUM> integrally connects the radiation source accommodation portion <NUM> and the detector accommodation portion <NUM>. The radiation source accommodation portion <NUM> is provided on the upper side in the height direction and the detector accommodation portion <NUM> is provided on the lower side in the height direction at a posture where the detector accommodation portion <NUM> faces the radiation source accommodation portion <NUM>.

The radiation source <NUM> includes a plurality of radiation tubes <NUM>, for example, <NUM> radiation tubes <NUM> and a housing <NUM> that accommodates the radiation tubes <NUM>. The housing <NUM> is filled with insulating oil. The radiation tubes <NUM> are used for tomosynthesis imaging which captures a plurality of projection images P (see <FIG>) of the breast M at different irradiation angles as radiographic images. The radiation detector <NUM> detects the radiation <NUM> transmitted through the breast M and outputs a radiographic image. In addition, the number of radiation tubes <NUM> is not limited to <NUM> in the above example. The number of radiation tubes <NUM> may be three or more.

The radiation source accommodation portion <NUM> accommodates an irradiation field limiter <NUM> in addition to the radiation source <NUM>. The irradiation field limiter <NUM> is attached to a lower part of the radiation source <NUM>. The irradiation field limiter <NUM> is also called a collimator and defines the irradiation field of the radiation <NUM> in an imaging surface <NUM> (see <FIG>) of the radiation detector <NUM>.

A compression plate <NUM> is attached between the radiation source accommodation portion <NUM> and the detector accommodation portion <NUM> in the main body portion <NUM>. The compression plate <NUM> is made of a material that transmits the radiation <NUM>. The compression plate <NUM> is disposed so as to face the detector accommodation portion <NUM>. The compression plate <NUM> can be moved in a direction toward the detector accommodation portion <NUM> and a direction away from the detector accommodation portion <NUM>. The compression plate <NUM> is moved toward the detector accommodation portion <NUM> and compresses the breast M interposed between the detector accommodation portion <NUM> and the compression plate <NUM>. There are a plurality of types of compression plates <NUM> which are interchanged according to, for example, the size of the breast M.

A face guard <NUM> is attached to a lower part of the front surface of the radiation source accommodation portion <NUM>. The face guard <NUM> protects the face of the subject H from the radiation <NUM>.

A tube voltage generator (not illustrated) that generates a tube voltage applied to the radiation tubes <NUM> is provided in the support 20B. In addition, a voltage cable (not illustrated) extending from the tube voltage generator is provided in the support 20B. The voltage cable further extends from the connection portion 21A into the radiation source accommodation portion <NUM> through the arm <NUM> and is connected to the radiation source <NUM>.

In <FIG>, the radiation tube <NUM> includes a cathode <NUM> and an anode <NUM>. The cathode <NUM> emits electrons. The electrons collide with the anode <NUM> and the anode <NUM> emits the radiation <NUM>. The cathode <NUM> and the anode <NUM> are accommodated in a vacuum glass tube <NUM> with a substantially cylindrical shape. The cathode <NUM> is a cold cathode. Specifically, the cathode <NUM> is an electron emission type including an electron emission source that emits an electron beam EB to the anode <NUM>, using a field emission phenomenon. The anode <NUM> is a fixed anode which is not rotated and whose position is fixed, unlike a rotating anode that is rotated by a rotation mechanism.

The tube voltage generator applies a tube voltage between the cathode <NUM> and the anode <NUM>. The electron beam EB is emitted from the cathode <NUM> to the anode <NUM> by the application of the tube voltage. Then, the radiation <NUM> is emitted from a point (hereinafter, referred to as a focus) F of the anode <NUM> where the electron beam EB collides.

In <FIG> illustrating the detector accommodation portion <NUM>, the radiation detector <NUM> has the imaging surface <NUM>. The imaging surface <NUM> detects the radiation <NUM> transmitted through the breast M to capture the projection image P of the breast M. Specifically, the imaging surface <NUM> is a two-dimensional plane in which pixels converting the radiation <NUM> into an electric signal are two-dimensionally arranged. The radiation detector <NUM> is called a flat panel detector (FPD). The radiation detector <NUM> may be an indirect conversion type that includes, for example, a scintillator converting the radiation <NUM> into visible light and converts visible light emitted from the scintillator into an electric signal or a direct conversion type that directly converts the radiation <NUM> into an electric signal.

<FIG> and <FIG> illustrate a method for capturing an image of the breast M in the mammography apparatus <NUM>. <FIG> illustrates craniocaudal view (CC) imaging and <FIG> illustrates mediolateral oblique view (MLO) imaging. The CC imaging is an imaging method which captures an image while compressing the breast M interposed between the detector accommodation portion <NUM> and the compression plate <NUM> in the vertical direction. In this case, the radiation detector <NUM> outputs a CC image as the projection image P. In contrast, the MLO imaging is an imaging method which captures an image while compressing the breast M interposed between the detector accommodation portion <NUM> and the compression plate <NUM> at an inclination angle of about <NUM>°. In this case, the radiation detector <NUM> outputs an MLO image as the projection image P. In addition, <FIG> and <FIG> illustrate only one radiation tube <NUM> for simplicity of illustration. Further, <FIG> and <FIG> illustrate the right breast M. However, an image of the left breast M may be captured.

In <FIG> which is a plan view illustrating the radiation source <NUM> and the radiation detector <NUM> as viewed from the support 20B, it is assumed that a direction normal to the imaging surface <NUM> is the Z direction, a direction along a side of the imaging surface <NUM> is the X direction, and a depth direction of the imaging surface <NUM> which is orthogonal to the Z direction and the X direction is the Y direction. The radiation tubes <NUM> are provided at a total of <NUM> positions SP1, SP2, ··· , SP14, and SP15 where the radiation <NUM> is emitted to the imaging surface <NUM> at different irradiation angles. The focuses F1 to F15 of the radiation <NUM> in the radiation tubes <NUM> at the positions SP1 to SP15 are arranged in a linear shape at equal intervals D_F.

Further, the position SP8 is disposed on a normal line NR to the imaging surface <NUM> which extends from a center point CP of the side of the imaging surface <NUM> in the X direction. Positions other than the position SP8 are set so as to be bilaterally symmetric with respect to the normal line NR such that the positions SP1 to SP7 are disposed on the left side of the normal line NR and the positions SP9 to SP15 are disposed on the right side of the normal line NR. That is, the radiation tubes <NUM> at the positions SP1 to SP7 and the radiation tubes <NUM> at the positions SP9 to SP15 are disposed at positions that are symmetric with respect to a line.

Here, a straight line GL on which the positions SP1 to SP15 are set is parallel to the side of the imaging surface <NUM> in the X direction in a plan view of the radiation source <NUM> and the radiation detector <NUM> from the Z direction. That is, the X direction is an example of an "arrangement direction of radiation tubes" according to the technique of the present disclosure. The straight line GL is offset to the front side (a side opposite to the support 20B) in the Y direction. The present disclosure is not limited to a case in which the intervals D_F between the focuses F1 to F15 are exactly equal to each other. For example, an error of ±<NUM>% is allowed in the interval D_F.

The irradiation angle of the radiation <NUM> is an angle formed between the normal line NR and a line connecting the center point CP and each of the focuses F1 to F15 of the radiation <NUM> in the radiation tubes <NUM> at the positions SP1 to SP15. Therefore, the irradiation angle at the position SP8 aligned with the normal line NR is <NUM>°. <FIG> illustrates a line L1 connecting the focus F1 at the position SP1 and the center point CP and an irradiation angle θ(<NUM>) formed between the normal line NR and the line L1 as an example.

An angle represented by a symbol Ψ is the maximum scanning angle of tomosynthesis imaging. The maximum scanning angle Ψ is defined by the positions SP1 and SP15 at both ends among the positions SP1 to SP15. Specifically, the maximum scanning angle Ψ is an angle formed between the line L1 connecting the focus F1 at the position SP1 and the center point CP and a line L15 connecting the focus F15 at the position SP15 and the center point CP.

In one normal tomosynthesis imaging operation, each of the radiation tubes <NUM> at the positions SP1 to SP15 is operated to emit the radiation <NUM> to the breast M at each of the positions SP1 to SP15. The radiation detector <NUM> detects the radiation <NUM> emitted at each of the positions SP1 to SP15 whenever the radiation <NUM> is emitted and outputs the projection images P at the positions SP1 to SP15. The tomosynthesis imaging can be performed by both the CC imaging method illustrated in <FIG> and the MLO imaging method illustrated in <FIG>. In the case of simple imaging in which the CC imaging illustrated in <FIG> and the MLO imaging illustrated in <FIG> are independently performed, only the radiation tube <NUM> disposed at the position SP8 where the irradiation angle is <NUM>° is operated.

As illustrated in <FIG>, in general, the mammography apparatus <NUM> generates tomographic images T1 to TN corresponding to any tomographic planes TF1 to TFN of the breast M from the plurality of projection images P at the plurality of positions SP1 to SP15 obtained by the tomosynthesis imaging illustrated in <FIG>. The mammography apparatus <NUM> generates the tomographic images T1 to TN using a known method such as a filtered back projection method. The tomographic images T1 to TN are images in which structures in the tomographic planes TF1 to TFN have been highlighted. Adjacent radiation tubes <NUM> are disposed close to each other at a distance of, for example, several centimeters to several tens of centimeters in order to improve the SN ratio of the tomographic image T.

As illustrated in <FIG>, radiation transmission windows <NUM> that transmit the radiation <NUM> are provided in the lower surface of the housing <NUM> at corresponding positions immediately below each radiation tube <NUM>. The radiation <NUM> emitted from each radiation tube <NUM> is emitted to the outside of the housing <NUM> through the radiation transmission windows <NUM>.

The irradiation field limiter <NUM> includes a housing <NUM> and one plate-like member <NUM>. Small openings <NUM> are provided in the upper surface of the housing <NUM> at positions corresponding to the radiation transmission windows <NUM> of the housing <NUM>. A large opening <NUM> is provided in the lower surface of the housing <NUM>. The lower surface of the housing <NUM> and the upper surface of the housing <NUM> are connected such that the radiation transmission windows <NUM> and the small openings <NUM> are aligned with each other. The radiation <NUM> emitted from the radiation transmission windows <NUM> is incident into the housing <NUM> through the small openings <NUM>.

The plate-like member <NUM> is accommodated in the housing <NUM>. The plate-like member <NUM> is made of a material shielding the radiation <NUM> such as lead. A total of eight through holes <NUM> are formed in the plate-like member <NUM> along the X direction. Adjacent through holes <NUM> are separated by an interval D_OP. The interval D_OP is nearly equal to an interval of one radiation tube <NUM>. The through hole <NUM> functions as an irradiation opening for defining the irradiation field, which will be described below. The irradiation opening is defined by the through hole <NUM> of the plate-like member <NUM> and the radiation <NUM> that has been incident into the housing <NUM> through the small opening <NUM> exits to the imaging surface <NUM> of the radiation detector <NUM> through the large opening <NUM>.

As illustrated in <FIG>, the plate-like member <NUM> is held in the housing <NUM> so as to be movable in the X direction by a pair of rails <NUM>. Both ends of the plate-like member <NUM> in the Y direction are fitted to the rails <NUM>. For example, bearings for facilitating the movement of the plate-like member <NUM> in the X direction are provided in the rails <NUM>, which is not illustrated.

As illustrated in <FIG>, a rack gear <NUM> is formed at a position that does not interfere with the rails <NUM> on the lower surface of one end of the plate-like member <NUM> in the X direction. The rack gear <NUM> is engaged with a pinion gear <NUM>. The pinion gear <NUM> is rotated clockwise and counterclockwise by a motor <NUM>. That is, the plate-like member <NUM> is reciprocated in the X direction by the rack and pinion. (A) of <FIG> illustrates a case in which the pinion gear <NUM> is rotated counterclockwise by the motor <NUM> and (B) of <FIG> illustrates a case in which the pinion gear <NUM> is rotated clockwise by the motor <NUM>. The rails <NUM> illustrated in <FIG> and the rack gear <NUM>, the pinion gear <NUM>, and the motor <NUM> illustrated in <FIG> form a displacement mechanism <NUM> (see <FIG>) that displaces the plate-like member <NUM> to move the through hole <NUM> functioning as the irradiation opening.

The displacement mechanism <NUM> moves the plate-like member <NUM> to a first set position illustrated in <FIG> and a second set position illustrated in <FIG>. As illustrated in <FIG>, at the first set position, each through hole <NUM> of the plate-like member <NUM> functions as an irradiation opening for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. That is, the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15 are an example of "first radiation tubes" according to the technique of the present disclosure.

In contrast, as illustrated in <FIG>, at the second set position, each through hole <NUM> of the plate-like member <NUM> functions as an irradiation opening for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. However, the through hole <NUM> corresponding to the radiation tube <NUM> at the position SP15 at the first set position is excluded. That is, the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14 is an example of "second radiation tubes" according to the technique of the present disclosure.

<FIG> illustrates a summary of the content illustrated in <FIG> and <FIG>. <FIG> of <FIG> illustrates a main portion in the case of the first set position illustrated in <FIG>. In contrast, (B) of <FIG> illustrates a main portion in the case of the second set position illustrated in <FIG>.

As illustrated in <FIG>, adjacent through holes <NUM> are separated from each other by the interval D_OP that is nearly equal to an interval of one radiation tube <NUM>. Therefore, at the first set position illustrated in <FIG> and <FIG> of <FIG>, the through holes <NUM> do not face the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. In contrast, at the second set position illustrated in <FIG> and <FIG> of <FIG>, the through holes <NUM> do not face the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15.

In <FIG>, the computer forming the control device <NUM> comprises, for example, a storage device <NUM>, a memory <NUM>, a central processing unit (CPU) <NUM>, a display <NUM>, and an input device <NUM>.

The storage device <NUM> is a hard disk drive that is provided in the computer forming the control device <NUM> or is connected to the computer through a cable or a network. Alternatively, the storage device <NUM> is a disk array in which a plurality of hard disk drives are connected. The storage device <NUM> stores a control program, such as an operating system, various application programs, and various kinds of data associated with these programs. In addition, a solid state drive may be used instead of the hard disk drive.

The memory <NUM> is a work memory used by the CPU <NUM> to perform processes. The CPU <NUM> loads the program stored in the storage device <NUM> to the memory <NUM> and performs a process corresponding to the program to control the overall operation of each unit of the computer.

The display <NUM> displays various screens. The various screens have operation functions by a graphical user interface (GUI). The computer forming the control device <NUM> receives operation commands input from the input device <NUM> through various screens. The input device <NUM> is, for example, a keyboard, a mouse, or a touch panel.

An operation program <NUM> is stored in the storage device <NUM>. The operation program <NUM> is an application program for causing the computer to function as the control device <NUM>. The storage device <NUM> stores a setting table <NUM> in addition to the operation program <NUM>.

In a case in which the operation program <NUM> is started, the CPU <NUM> of the control device <NUM> functions as a receiving unit <NUM>, a setting unit <NUM>, a control unit <NUM>, a generation unit <NUM>, and a display control unit <NUM> in cooperation with, for example, the memory <NUM>.

The receiving unit <NUM> receives imaging conditions <NUM> input by the operator through the input device <NUM>. The receiving unit <NUM> outputs the imaging conditions <NUM> to the setting unit <NUM>.

The setting unit <NUM> receives the imaging conditions <NUM> from the receiving unit <NUM>. In addition, the setting unit <NUM> reads out the setting table <NUM> from the storage device <NUM>. The setting unit <NUM> sets the operating conditions <NUM> of the radiation tubes <NUM> and the displacement mechanism <NUM> on the basis of the imaging conditions <NUM> and the setting table <NUM>. The setting unit <NUM> outputs the operating conditions <NUM> to the control unit <NUM>.

The control unit <NUM> controls the operation of the radiation source <NUM>, the radiation detector <NUM>, and the irradiation field limiter <NUM>. The control unit <NUM> receives the operating conditions <NUM> from the setting unit <NUM>. The control unit <NUM> operates the radiation tubes <NUM> and the displacement mechanism <NUM> on the basis of the operating conditions <NUM> such that the radiation tubes <NUM> emit the radiation <NUM>. The control unit <NUM> outputs the projection image P detected by the radiation detector <NUM> by the emission of the radiation <NUM> from the radiation detector <NUM> to the generation unit <NUM>.

The generation unit <NUM> receives the plurality of projection images P from the radiation detector <NUM>. The generation unit <NUM> generates tomographic images T on the basis of the plurality of projection images P. The generation unit <NUM> outputs the tomographic images T to the display control unit <NUM>.

The display control unit <NUM> receives the tomographic images T from the generation unit <NUM>. The display control unit <NUM> performs control to display the received tomographic images T on the display <NUM>.

As illustrated in <FIG>, the imaging conditions <NUM> include the compression plate <NUM> used (described as a compression plate used in <FIG>) and an imaging mode. As described above, the compression plate <NUM> is interchanged according to, for example, the size of the breast M. In the tomosynthesis imaging, the radiation tube <NUM> that emits the radiation <NUM> varies depending on the compression plate <NUM> used (see <FIG>). Therefore, the compression plate <NUM> used is included in the imaging conditions <NUM>.

The imaging mode includes an image quality priority mode and an exposure reduction mode (see <FIG>). The image quality priority mode is a mode in which the radiation <NUM> is emitted from as many radiation tubes <NUM> as possible to increase the SN ratio of the tomographic image. In contrast, the exposure reduction mode is a mode in which the minimum amount of radiation <NUM> is emitted to reduce the exposure of the subject H as much as possible. Since the radiation tube <NUM> that emits the radiation <NUM> varies depending on each of the imaging modes (see <FIG>), the imaging mode is included in the imaging conditions <NUM>.

<FIG> illustrates imaging conditions <NUM> in which a compression plate B is registered as the compression plate <NUM> used and the image quality priority mode is registered as the imaging mode. In addition to the compression plate <NUM> used and the imaging mode, information for changing the radiation tube <NUM> that emits the radiation <NUM> may be added to the imaging conditions <NUM>.

As illustrated in <FIG>, in the setting table <NUM>, the radiation tube identification data (ID) of the radiation tubes <NUM> (described as the radiation tubes used in <FIG>) that emit the radiation <NUM> is registered for each combination of the compression plate <NUM> used and the imaging mode. For the radiation tube ID, numbers are linked to each of the positions SP1 to SP15. For example, the radiation tube <NUM> disposed at the position SP1 is represented by RT01, the radiation tube <NUM> disposed at the position SP2 is represented by RT02, ··· , the radiation tube <NUM> disposed at the position SP14 is represented by RT14, and the radiation tube <NUM> disposed at the position SP15 is represented by RT15.

In the exposure reduction mode, the number of radiation tubes <NUM> that emit the radiation <NUM> is smaller than that in the image quality priority mode. For example, in a case in which the compression plate <NUM> used is the compression plate B, a total of <NUM> radiation tubes <NUM> having the radiation tube IDs RT02 to RT14 are registered in the image quality priority mode. In contrast, in the exposure reduction mode, a total of seven radiation tubes <NUM> having the radiation tube IDs RT02, RT04, RT06, RT08, RT10, RT12, and RT14 are registered.

In <FIG>, in the operating conditions <NUM>, the radiation tube ID of the radiation tube <NUM> and the set position of the plate-like member <NUM> are registered for each irradiation number of the radiation <NUM>. <FIG> illustrates the operating conditions <NUM> in a case in which the content of the imaging conditions <NUM> is as illustrated in <FIG>, that is, is that the compression plate <NUM> used is the compression plate B and the imaging mode is the image quality priority mode. In a case in which the content of the imaging conditions <NUM> is as illustrated in <FIG>, the setting table <NUM> illustrated in <FIG> shows that the radiation tubes <NUM> with the radiation tube IDs RT02 to RT14 emit the radiation <NUM>. Therefore, in the operating conditions <NUM>, first, for irradiation numbers <NUM> to <NUM>, RT03, RT05, RT07, RT09, RT11, and RT13 are registered as the radiation tube IDs and the first set position is registered as the set position of the plate-like member <NUM>. Then, for irradiation numbers <NUM> to <NUM>, RT02, RT04, RT06, RT08, RT10, RT12, and RT14 are registered as the radiation tube IDs and the second set position is registered as the set position of the plate-like member <NUM>.

In the case of the operating conditions <NUM> illustrated in <FIG>, the control unit <NUM> performs control such that the radiation tubes <NUM> with the radiation tube IDs RT03, RT05, RT07, RT09, RT11, RT13, RT02, RT04, RT06, RT08, RT10, RT12, and RT14 emit the radiation <NUM> in this order. Further, the control unit <NUM> operates the displacement mechanism <NUM> between irradiation number <NUM> and irradiation number <NUM> to move the set position of the plate-like member <NUM> from the first set position to the second set position.

As another example, a case is considered in which the content of the imaging conditions <NUM> is that the compression plate <NUM> used is the compression plate B and the imaging mode is the exposure reduction mode. In this case, according to the setting table <NUM>, the radiation tubes <NUM> with the radiation tube IDs RT02, RT04, RT06, RT08, RT10, RT12, and RT14 emit the radiation <NUM>. Therefore, in this case, the plate-like member <NUM> is maintained at the second set position from beginning to end.

The control unit <NUM> recognizes whether the plate-like member <NUM> is at the first set position or the second set position on the basis of, for example, a detection signal of a linear encoder.

Next, the operation of the above-mentioned configuration will be described with reference to a flowchart illustrated in <FIG>. In a case in which the operation program <NUM> is started, the CPU <NUM> of the control device <NUM> functions as the receiving unit <NUM>, the setting unit <NUM>, the control unit <NUM>, the generation unit <NUM>, and the display control unit <NUM> as illustrated in <FIG>.

First, the receiving unit <NUM> receives the imaging conditions <NUM> (Step ST100). The imaging conditions <NUM> are output from the receiving unit <NUM> to the setting unit <NUM>. Then, the setting unit <NUM> sets the operating conditions <NUM> on the basis of the imaging conditions <NUM> and the setting table <NUM> (Step ST110). The operating conditions <NUM> are output from the setting unit <NUM> to the control unit <NUM>.

In Step ST120, the control unit <NUM> operates the radiation tubes <NUM> according to the operating conditions <NUM>. The radiation <NUM> emitted from the radiation tubes <NUM> is incident into the irradiation field limiter <NUM> through the radiation transmission windows <NUM> and the small openings <NUM>. The radiation <NUM> incident on the irradiation field limiter <NUM> passes through the through holes <NUM> of the plate-like member <NUM> which function as the irradiation openings. The irradiation field of the radiation <NUM> is defined in this way. As illustrated in <FIG>, the through holes <NUM> are arranged at the interval D_OP that is nearly equal to an interval of one radiation tube <NUM>. Therefore, in a case in which the radiation <NUM> is emitted from a certain radiation tube <NUM>, the leakage of the radiation <NUM> from the adjacent through hole <NUM> is suppressed.

In Step ST120, the control unit <NUM> operates the displacement mechanism <NUM> on the basis of the operating conditions <NUM> to move the plate-like member <NUM> in the X direction, if necessary. As a result, the through hole <NUM> that functions as the irradiation opening is shared by two radiation tubes <NUM>.

The irradiation field is defined by the through hole <NUM> and the radiation <NUM> emitted to the breast M is detected by the radiation detector <NUM>. Then, the projection images P are output from the radiation detector <NUM> to the generation unit <NUM>. Step ST120 is repeatedly performed in a case in which the emission of the radiation <NUM> by all of the radiation tubes <NUM> registered in the operating conditions <NUM> does not end (NO in Step ST130).

In a case in which the emission of the radiation <NUM> by all of the radiation tubes <NUM> registered in the operating conditions <NUM> ends (YES in Step ST130), the generation unit <NUM> generates the tomographic images T on the basis of the projection images P from the radiation detector <NUM> (Step ST140). The tomographic images T are output from the generation unit <NUM> to the display control unit <NUM>. The tomographic images T are displayed on the display <NUM> by the display control unit <NUM> and are provided for the operator to browse (Step ST150).

As described above, the mammography apparatus <NUM> uses the irradiation field limiter <NUM> which has a plurality of through holes <NUM> that are irradiation openings for the radiation <NUM> and are arranged at an interval D_OP of at least one radiation tube <NUM> and in which the position of the irradiation openings is moved to the first set position in a case in which the radiation <NUM> is emitted from first radiation tubes which are some of three or more radiation tubes <NUM> and the second set position in a case in which the radiation <NUM> is emitted from second radiation tubes different from the first radiation tubes among the three or more radiation tubes <NUM> with respect to the radiation source <NUM> having the three or more radiation tubes <NUM>. Therefore, it is possible to prevent unnecessary exposure.

In this embodiment, the irradiation field limiter <NUM> includes the plate-like member <NUM> in which the through holes <NUM> functioning as the irradiation openings are formed. Then, the displacement mechanism <NUM> moves the plate-like member <NUM> along the X direction which is the arrangement direction of the radiation tubes <NUM> to move the through holes <NUM>. Therefore, it is possible to define the irradiation field of the radiation <NUM> with a very simple configuration.

As illustrated in <FIG>, the plate-like member <NUM> may be divided into a first plate-like member 52A and a second plate-like member 52B. The first plate-like member 52A defines irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1 to SP8. Further, the second plate-like member 52B defines irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP9 to SP15.

Specifically, the through holes <NUM> of the first plate-like member 52A function as the irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, and SP7 at the first set position. In contrast, the through holes <NUM> of the first plate-like member 52A function as the irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, and SP8 at the second set position. Further, the through holes <NUM> of the second plate-like member 52B function as the irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP9, SP11, SP13, and SP15 at the first set position. In contrast, the through holes <NUM> of the second plate-like member 52B function as the irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP10, SP12, and SP14 at the second set position. The first plate-like member 52A and the second plate-like member 52B are moved to the first set position and the second set position at the same timing.

<FIG> illustrates an example in which the first plate-like member 52A and the second plate-like member 52B deviate in the Z direction so as not to interfere with each other in the X direction. In this case, as illustrated in a table <NUM> of <FIG>, while the radiation <NUM> is emitted in a state in which the second plate-like member 52B is at the first set position, the first plate-like member 52A can be moved to the second set position. Further, while the radiation <NUM> is emitted in a state in which the first plate-like member 52A is at the second set position, the second plate-like member 52B can be moved to the second set position. In the first embodiment and <FIG>, the emission of the radiation <NUM> and the movement of the plate-like member <NUM> need to be performed separately. However, according to the example illustrated in <FIG>, the emission of the radiation <NUM> and the movement of the plate-like member <NUM> can be performed together. Therefore, it is possible to reduce the imaging time.

In the following embodiments, the description will be made on the premise that <NUM> radiation tubes <NUM> are disposed at the positions SP1 to SP15 as in the first embodiment.

In a second embodiment illustrated in <FIG>, the plate-like member <NUM> is moved in a direction in which the interval between the radiation tube <NUM> and the through hole <NUM> changes.

As illustrated in <FIG>, in the second embodiment, the plate-like member <NUM> is moved not only in the X direction but also in the Z direction. Therefore, the interval between the radiation tube <NUM> and the through hole <NUM> changes. That is, the Z direction is an example of a "direction in which the interval between the radiation tube and the through hole changes" according to the technique of the present disclosure. As a method for moving the plate-like member <NUM> in the Z direction, a method can be adopted in which the rack and pinion illustrated in <FIG> is also provided for the Z direction. Alternatively, the plate-like member <NUM> may be moved up and down in the Z direction by wires and pulleys. The displacement mechanism <NUM> also includes a mechanism that moves the plate-like member <NUM> in the Z direction.

(A) of <FIG> illustrates a case in which the plate-like member <NUM> is moved to the radiation tube <NUM> and the interval between the radiation tube <NUM> and the through hole <NUM> decreases. In contrast, (B) of <FIG> illustrates a case in which the plate-like member <NUM> is moved to the radiation detector <NUM> and the interval between the radiation tube <NUM> and the through hole <NUM> increases. In (A) of <FIG>, the irradiation field defined by the through hole <NUM> has substantially the same size as the imaging surface <NUM> of the radiation detector <NUM>, as represented by a one-dot chain line and reference numeral 100A. In contrast, in (B) of <FIG>, the size of the irradiation field defined by the through hole <NUM> is slightly smaller than the size of the imaging surface <NUM>, as represented by a one-dot chain line and reference numeral 100B. That is, in a case in which the plate-like member <NUM> is moved to the radiation detector <NUM> and the interval between the radiation tube <NUM> and the through hole <NUM> increases, the size of the irradiation field decreases.

As such, in the second embodiment, since the plate-like member <NUM> is moved in the direction in which the interval between the radiation tube <NUM> and the through hole <NUM> changes, it is possible to change the size of the irradiation field.

In a third embodiment illustrated in <FIG>, a convex portion that protrudes toward the radiation tube <NUM> is provided between adjacent through holes of a plate-like member.

As illustrated in <FIG>, in a plate-like member <NUM> according to the third embodiment, a convex portion <NUM> that protrudes toward the radiation tube <NUM> is provided between adjacent through holes <NUM>. Since the convex portion <NUM> is provided, the radiation <NUM> deviating from the through hole <NUM> is effectively shielded as represented by a cross mark in <FIG>. Therefore, it is possible to more reliably prevent the radiation <NUM> from leaking from the adjacent through holes <NUM>. Further, it is possible to further reduce the interval D_OP between the adjacent through holes <NUM>. As a result, it is possible to make the adjacent radiation tubes <NUM> closer to each other and to further improve the SN ratio of the tomographic image T.

A rising surface of the convex portion <NUM> toward the radiation tube <NUM> may be inclined as illustrated in <FIG> or may be vertical.

In a fourth embodiment illustrated in <FIG>, an irradiation field limiter having a configuration in which plate-like members are stacked is used.

The irradiation field limiter illustrated in <FIG> has a configuration in which two plate-like members 110A and 110B are stacked in the Z direction which is a direction normal to the imaging surface <NUM> of the radiation detector <NUM>. Through holes 111A are formed in the plate-like member 110A and through holes 111B are formed in the plate-like member 110B. The plate-like members 110A and 110B are held by rails (not illustrated) so as to be movable in the X direction, similarly to the plate-like member <NUM> according to the first embodiment.

As illustrated in (A) of <FIG>, at the first set position, the through holes 111A and 111B of the plate-like members 110A and 110B function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in (B) of <FIG>, at the second set position, the through holes 111A and 111B of the plate-like members 110A and 110B function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14.

As illustrated in <FIG>, a rack gear 115Ais formed on the lower surface of one end of the plate-like member 110A in the X direction. Similarly, a rack gear 115B is formed on the upper surface of one end of the plate-like member 110B in the X direction. The rack gears 115A and 115B are engaged with a pinion gear <NUM>. The pinion gear <NUM> is rotated clockwise and counterclockwise by a motor <NUM>. That is, the plate-like members 110A and 110B are reciprocated in opposite directions in the X direction by the rack and pinion. As described above, the two plate-like members 110A and 110B that are adjacent to each other in the stacking direction are moved at the same time in the X direction by one motor <NUM>. The motor <NUM> is an example of an "actuator" according to the technique of the present disclosure. (A) of <FIG> illustrates a case in which the pinion gear <NUM> is rotated counterclockwise by the motor <NUM> and (B) of <FIG> illustrates a case in which the pinion gear <NUM> is rotated clockwise by the motor <NUM>. The rails (not illustrated) and the rack gears 115A and 115B, the pinion gear <NUM>, and the motor <NUM> illustrated in <FIG> form a displacement mechanism.

<FIG> is a diagram illustrating the plate-like members 110A and 110B as viewed from the radiation tube <NUM>. Since the plate-like member 110B is located closer to the radiation detector <NUM> than the plate-like member 110A, the size of the through hole 111B of the plate-like member 110B is slightly larger than the size of the through hole 111A of the plate-like member 110A as illustrated in <FIG>. An irradiation opening that is hatched and is denoted by reference numeral <NUM> is defined by three sides of the through hole 111A and one side of the through hole 111B. That is, at least one side of each of the through holes 111A and 111B functions as an opening edge of the irradiation opening <NUM>. Therefore, the interval D_OP between the irradiation openings <NUM> defined by the through holes 111A and 111B is an interval of at least one radiation tube <NUM>, as in the first embodiment (see <FIG>).

As illustrated in <FIG>, in the irradiation field limiter according to this embodiment, the amount of movement of the plate-like members 110A and 110B in the X direction is finely adjusted to adjust the width W_OPX of the irradiation opening <NUM> in the X direction. <FIG> illustrates a case in which the width W_OPX of the irradiation opening <NUM> in the X direction is slightly increased from the state illustrated in <FIG> and <FIG> illustrates a case in which the width W_OPX of the irradiation opening <NUM> in the X direction is slightly decreased from the state illustrated in <FIG>.

As such, in the fourth embodiment, the irradiation field limiter is used in which the plate-like members 110A and 110B having the through holes 111A and 111B, at least one side of which functions as the opening edge of the irradiation opening <NUM>, are stacked in the Z direction that is a direction normal to the imaging surface <NUM> of the radiation detector <NUM>. The displacement mechanism moves each of the plate-like members 110A and 110B in the X direction which is the arrangement direction of the radiation tubes <NUM> to move the irradiation openings <NUM>. Therefore, as illustrated in <FIG>, it is possible to adjust the width W_OPX of the irradiation opening <NUM> in the X direction.

Further, as illustrated in <FIG>, the two plate-like members 110A and 110B which are adjacent to each other in the stacking direction are moved at the same time by the motor <NUM> in the X direction which is the arrangement direction of the radiation tubes <NUM>. Therefore, it is possible to contribute to reducing a component cost and reducing the size of the apparatus, as compared to a case in which the plate-like members 110A and 110B are moved by two motors.

The number of plate-like members stacked is not limited to two. For example, as illustrated in <FIG>, an irradiation field limiter having a configuration in which four plate-like members 120A, 120B, 120C, and 120D are stacked in the Z direction may be used.

In <FIG>, through holes 121A, 121B, 121C, and 121D are formed in the plate-like members 120A to 120D along the X direction, respectively. As illustrated in (A) of <FIG>, at the first set position, the through holes 121A to 121D of the plate-like members 120A to 120D function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in (B) of <FIG>, at the second set position, the through holes 121A to 121D of the plate-like members 120A to 120D function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. In this case, the interval D_OP between the irradiation openings <NUM> defined by the through holes 121Ato 121D is an interval of at least one radiation tube <NUM>.

Further, two plate-like members 120A and 120B that are adjacent to each other in the stacking direction are reciprocated in opposite directions in the X direction by one actuator, as in the irradiation field limiter illustrated in <FIG>. Similarly, two plate-like members 120C and 120D that are adjacent to each other in the stacking direction are reciprocated in opposite directions in the X direction by one actuator. Further, as in the irradiation field limiter illustrated in <FIG>, at least one side of each of the through holes 121A to 121D functions as an opening edge of the irradiation opening <NUM>.

As such, in a case in which the four plate-like members 120A to 120D are used, the width W_OPX of the irradiation opening <NUM> in the X direction can be adjusted more finely than that in a case in which two plate-like members 110A and 110B are used.

The third embodiment may be applied such that a convex portion protruding toward the radiation tube <NUM> is provided between adjacent through holes of a plate-like member closest to the radiation tube <NUM> among a plurality of plate-like members.

In a fifth embodiment illustrated in <FIG> and <FIG>, an irradiation field limiter including a sheet-like member is used.

In <FIG>, through holes <NUM> that function as irradiation openings are formed in a sheet-like member <NUM>. Adjacent through holes <NUM> are arranged at an interval D_OP corresponding to at least one radiation tube <NUM>, similarly to the through holes <NUM> of the plate-like member <NUM> according to the first embodiment. That is, it can be said that the sheet-like member <NUM> replaces the plate-like member <NUM> according to the first embodiment. The sheet-like member <NUM> is held by a pair of rails <NUM> so as to be movable in the X direction. For example, the sheet-like member <NUM> is formed by applying a material for shielding the radiation <NUM> onto a surface of a flexible plastic film.

One end of the sheet-like member <NUM> in the X direction is attached to a core <NUM>. The core <NUM> is rotated clockwise and counterclockwise by a motor <NUM>. The sheet-like member <NUM> is sent along the X direction and is rolled by the rotation of the core <NUM> by the motor <NUM>. Therefore, as represented by a dashed line, the through holes <NUM> that function as the irradiation openings are moved. That is, the rails <NUM>, the core <NUM>, and the motor <NUM> form a displacement mechanism <NUM>. A space for accommodating the sent sheet-like member <NUM> is ensured at the other end of the sheet-like member <NUM> in the X direction, which is not illustrated.

As illustrated in <FIG>, there are three types of through holes <NUM>, that is, a through hole 126A with a relatively large size, a through hole 126B with a medium size, and a through hole 126C with a relatively small size. A control unit according to the fifth embodiment changes the amount of sending of the sheet-like member <NUM> such that any one of the through holes 126A to 126C faces each radiation tube <NUM>.

As such, in the fifth embodiment, the irradiation field limiter including the sheet-like member <NUM> in which the through holes <NUM> functioning as the irradiation openings are formed is used. Then, the displacement mechanism <NUM> sends the sheet-like member <NUM> in the X direction which is the arrangement direction of the radiation tubes <NUM> and rolls the sheet-like member <NUM> to move the irradiation openings. Therefore, the weight of the irradiation field limiter can be less than the weight of the irradiation field limiter including the plate-like member.

Further, a plurality of types of through holes 126A to 126C having different sizes are formed in the sheet-like member <NUM>. Therefore, it is possible to change the size of the irradiation field. It is possible to significantly reduce the number of components as compared to a case in which a plurality of plate-like members having a plurality of types of through holes with different sizes are prepared and are selectively used. In addition, it is possible to contribute to reducing the size of the apparatus.

The number of types of the through holes <NUM> may be two or four or more. Further, a core may be attached to the other end of the sheet-like member <NUM> in the X direction and may be rotated by a motor.

The number of types of the through holes <NUM> may be one. In this case, the second embodiment may be applied to move the sheet-like member <NUM> in the direction in which the interval between the radiation tube <NUM> and the through hole <NUM> changes. Alternatively, the fourth embodiment may be applied to stack a plurality of sheet-like members <NUM> in the Z direction.

In a sixth embodiment illustrated in <FIG>, a plate-like member is rotated to move irradiation openings.

An irradiation field limiter illustrated in <FIG> includes eight plate-like members <NUM> that are arranged in the X direction (only five plate-like members <NUM> are illustrated in <FIG>). Each of the plate-like members <NUM> has one through hole <NUM> that functions as the irradiation opening. A rotating shaft <NUM> is attached to each plate-like member <NUM>. The rotating shaft <NUM> is disposed between the radiation tube <NUM> and the imaging surface <NUM>. Specifically, the rotating shaft <NUM> is a shaft extending in a direction that is orthogonal to the X direction which is the arrangement direction of the radiation tubes <NUM> and is parallel to the imaging surface <NUM> of the radiation detector <NUM>. That is, the rotating shaft <NUM> is parallel to the Y direction.

A motor <NUM> is connected to the rotating shafts <NUM>. The rotating shafts <NUM> are rotated clockwise and counterclockwise by the motor <NUM>. Each plate-like member <NUM> is rotated clockwise and counterclockwise about the rotating shaft <NUM>. The rotating shafts <NUM> and the motor <NUM> form a displacement mechanism <NUM>.

As illustrated in (A) of <FIG>, at the first set position, the through holes <NUM> of the plate-like member <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in (B) of <FIG>, at the second set position, the through holes <NUM> of the plate-like member <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. However, the through hole <NUM> corresponding to the radiation tube <NUM> at the position SP1 at the first set position is excluded. In this case, the interval D_OP between the irradiation openings defined by the through holes <NUM> is an interval of at least one radiation tube <NUM>.

As such, in the sixth embodiment, the irradiation field limiter including the plate-like members <NUM> in which the through hole <NUM> functioning as the irradiation opening is formed is used. Then, the plate-like member <NUM> is rotated about the rotating shaft <NUM> extending in a direction that is orthogonal to the X direction which is the arrangement direction of the radiation tubes <NUM> and is parallel to the imaging surface <NUM> of the radiation detector <NUM> to move the irradiation opening. Therefore, it is possible to respond to a case in which it is difficult to adopt each of the above-described embodiments in which the plate-like member or the sheet-like member is moved in the X direction for some reason.

The number of through holes formed in the plate-like member is not limited to one. For example, two through holes <NUM> may be formed, as in a plate-like member <NUM> illustrated in <FIG> and <FIG>.

In <FIG> and <FIG>, the plate-like member <NUM> includes one first plate-like member 145A that is disposed close to the position SP1 and four second plate-like members 145B. One through hole <NUM> that functions as the irradiation opening is formed in the first plate-like member 145A. In contrast, two through holes <NUM> that function as the irradiation openings are formed in the second plate-like member 145B. Rotating shafts <NUM> are attached to the first plate-like member 145A and the second plate-like members 145B. Similarly to the rotating shaft <NUM>, the rotating shaft <NUM> is a shaft extending in a direction that is orthogonal to the X direction which is the arrangement direction of the radiation tubes <NUM> and is parallel to the imaging surface <NUM> of the radiation detector <NUM>.

A motor <NUM> is connected to the rotating shafts <NUM>. The rotating shafts <NUM> are rotated clockwise and counterclockwise by the motor <NUM>. The first plate-like member 145A and the second plate-like members 145B are rotated clockwise and counterclockwise about the rotating shafts <NUM>. The rotating shafts <NUM> and the motor <NUM> form a displacement mechanism <NUM>.

As illustrated in <FIG>, at the first set position, the through holes <NUM> of the second plate-like member 145B function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in <FIG>, at the second set position, the through holes <NUM> of the first plate-like member 145A and the second plate-like member 145B function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. However, the through holes <NUM> of the second plate-like member 145B corresponding to the radiation tubes <NUM> at the position SP13 and SP15 at the first set position are excluded. In this case, the interval D_OP between the irradiation openings defined by the through holes <NUM> is an interval of at least one radiation tube <NUM>.

In a seventh embodiment illustrated in <FIG> and <FIG>, adjustment members <NUM> adjust the widths of a plurality of irradiation openings <NUM> at once.

<FIG> and <FIG> illustrate a case in which the plate-like member <NUM> according to the first embodiment is used. In <FIG> and <FIG>, a pair of adjustment members <NUM> are disposed above the plate-like member <NUM> so as to cover the plate-like member <NUM>. The adjustment member <NUM> is a rectangular plate that is long in the X direction and has long sides arranged along the X direction. The adjustment members <NUM> can be reciprocated in the Y direction by a movement mechanism (not illustrated). The Y direction is an example of "a direction intersecting the arrangement direction of the radiation tubes" according to the technique of the present disclosure. As illustrated in <FIG>, the adjustment members <NUM> are moved in the Y direction to adjust the widths W_OPY of the plurality of irradiation openings <NUM> in the Y direction at once.

As such, in the seventh embodiment, the adjustment members <NUM> for adjusting the widths W_OPY of the plurality of irradiation openings <NUM> are provided. The adjustment members <NUM> are moved in the direction intersecting the arrangement direction of the radiation tubes <NUM> to adjust the widths W_OPY of the plurality of irradiation openings <NUM> at once. Therefore, it is possible to easily adjust the widths W_OPY of the irradiation openings <NUM> in the Y direction.

The application of the seventh embodiment is not limited to the irradiation field limiter <NUM> including the plate-like member <NUM> according to the first embodiment, but the seventh embodiment may be applied to the irradiation field limiters according to other embodiments to adjust the widths W_OPY of the irradiation openings <NUM> in the Y direction.

A pair of plate-like members <NUM> and <NUM> illustrated in <FIG> may be used.

In <FIG>, the pair of plate-like members <NUM> and <NUM> are line-symmetric with respect to the X direction. The plate-like members <NUM> and <NUM> have a shape obtained by cutting the plate-like member <NUM> of the first embodiment in zigzag. Specifically, the plate-like members <NUM> and <NUM> have a comb shape in which a plurality of rectangular plate-like protruding portions <NUM> and <NUM> protrude from long portions <NUM> and <NUM> that are long in the X direction in the Y direction at intervals, respectively. The plate-like members <NUM> and <NUM> are disposed so as to deviate from each other in the Z direction (see also <FIG> and <FIG>). The plate-like members <NUM> and <NUM> are moved obliquely upward or downward (see <FIG> and <FIG>).

In this case, as illustrated in <FIG>, the irradiation opening <NUM> is defined by a space surrounded by the long portion <NUM> and the protruding portion <NUM> of the plate-like member <NUM> and the long portion <NUM> and the protruding portion <NUM> of the plate-like member <NUM>.

As illustrated in <FIG>, at the first set position, the long portions <NUM> and <NUM> and the protruding portions <NUM> and <NUM> of the plate-like members <NUM> and <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in <FIG>, at the second set position, the long portions <NUM> and <NUM> and the protruding portions <NUM> and <NUM> of the plate-like members <NUM> and <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. In this case, the interval D_OP between the irradiation openings <NUM> is an interval of at least one radiation tube <NUM>.

At the first set position, the plate-like member <NUM> is disposed on the side of the radiation tubes <NUM> and the plate-like member <NUM> is disposed on the side of the radiation detector <NUM>. At the second set position, the plate-like member <NUM> is moved obliquely downward from the first set position and the plate-like member <NUM> is moved obliquely upward from the first set position. Then, contrary to the first set position, the plate-like member <NUM> is disposed on the side of the radiation tubes <NUM> and the plate-like member <NUM> is disposed on the side of the radiation detector <NUM>. In <FIG> and <FIG>, the protruding portions <NUM> and <NUM> are represented by solid lines and the long portions <NUM> and <NUM> are represented by two-dot chain lines for ease of understanding.

As such, the plate-like members <NUM> and <NUM> without having through holes are used and the irradiation openings <NUM> can be defined by moving the plate-like members <NUM> and <NUM> in an oblique direction. Two plate-like members <NUM> and <NUM> are illustrated in <FIG>. However, the number of plate-like members may be three or more.

As illustrated in <FIG> and <FIG>, the radiation tubes <NUM> may be divided into a first group of the radiation tubes <NUM> disposed at the positions SP1 to SP5, a second group of the radiation tubes <NUM> disposed at the positions SP6 to SP10, and a third group of the radiation tubes <NUM> disposed at the positions SP11 to SP15. The radiation tubes <NUM> in the first group and the third group may be arranged so as to be inclined at a predetermined angle with respect to the imaging surface <NUM>.

In this case, it is preferable to prepare plate-like members <NUM> for each group. That is, a plate-like member 180A is prepared for the first group, a plate-like member 180B is prepared for the second group, and a plate-like member 180C is prepared for the third group. A through hole 181A is formed in the plate-like member 180A, a through hole 181B is formed in the plate-like member 180B, and a through hole 181C is formed in the plate-like member 180C.

The plate-like members 180A to 180C are moved to a first set position illustrated in <FIG> and a second set position illustrated in <FIG>. As illustrated in <FIG>, at the first set position, the through holes 181A to 181C of the plate-like members 180A to 180C function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in <FIG>, at the second set position, the through holes 181A to 181C of the plate-like members 180A to 180C function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. In this case, the interval D_OP between the irradiation openings defined by the through holes 181Ato 181C is an interval of at least one radiation tube <NUM>.

As illustrated in <FIG>, in the second group, a ratio SD1/SD2 of a distance SD1 between the radiation tube <NUM> and the plate-like member 180B to a distance SD2 between the plate-like member 180B and the imaging surface <NUM> is the same for all of the radiation tubes <NUM> forming the group. Further, the arrangement direction of the radiation tubes <NUM> is parallel to the direction of the long side of the plate-like member 180B. Furthermore, the side of the imaging surface <NUM> in the X direction is parallel to the direction of the long side of the plate-like member 180B. Therefore, the through holes 181B of the plate-like member 180B have the same size and have a rectangular shape. The distance SD1 is the length of a line connecting the focus F of the radiation tube <NUM> and the center of the through hole 181B facing the radiation tube <NUM>. The distance SD2 is the length of a line connecting the center of the through hole 181B and the center of the imaging surface <NUM>.

In contrast, as illustrated in <FIG>, the first group is the same as the second group in that the arrangement direction of the radiation tubes <NUM> is parallel to the direction of the long side of the plate-like member 180A. However, in the first group, the ratio SD1/SD2 varies depending on the radiation tubes <NUM> forming the group. Further, as described above, since the radiation tubes <NUM> are arranged so as to be inclined at a predetermined angle with respect to the imaging surface <NUM>, the side of the imaging surface <NUM> in the X direction is not parallel to the direction of the long side of the plate-like member 180A. Therefore, the through holes 181A of the plate-like member 180A have different sizes. Specifically, the size of the through hole 181A increases toward the end. Further, the through hole 181A has a trapezoidal shape in which the base is widened toward the end. In addition, since the plate-like member 180C is mirror-symmetric to the plate-like member 180A, it is not illustrated.

As illustrated in <FIG>, in the first group, the radiation tubes <NUM> may be disposed so as to become further away from the plate-like member 180A as becoming closer to the center such that the ratio SD1/SD2 is the same for all of the radiation tubes <NUM> forming the group. In this case, the through holes 181A have the same trapezoidal shape as those in the case illustrated in <FIG> and have the same size. In this case, in the third group, similarly, the radiation tubes <NUM> are disposed so as to become further away from the plate-like member 180C as becoming closer to the center such that the ratio SD1/SD2 is the same for all of the radiation tubes <NUM> forming the group, which is not illustrated.

As such, a plurality of radiation tubes <NUM> may be divided into a plurality of groups, each group may be regarded as one radiation source, and the plate-like members 180A to 180C may be arranged in each group.

In each of the above-described embodiments, the positions where the focuses F are disposed are arranged in a straight line. However, the invention is not limited thereto. As illustrated in <FIG>, the plurality of positions SP1 to SP15 where the focuses F1 to F15 are disposed may be arranged in an arc shape at equal intervals D_F. In this case, for example, one plate-like member <NUM> illustrated in <FIG> and <FIG> is used. The plate-like member <NUM> has an arc shape following the positions SP1 to SP15. Through holes <NUM> that function as irradiation openings are formed in the plate-like member <NUM>. The plate-like member <NUM> is moved in the arrangement direction of the radiation tubes <NUM>.

As illustrated in <FIG>, at the first set position, the through holes <NUM> of the plate-like member <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP1, SP3, SP5, SP7, SP9, SP11, SP13, and SP15. In contrast, as illustrated in <FIG>, at the second set position, the through holes <NUM> of the plate-like member <NUM> function as irradiation openings for the radiation <NUM> emitted from the radiation tubes <NUM> disposed at the positions SP2, SP4, SP6, SP8, SP10, SP12, and SP14. However, the through hole <NUM> corresponding to the radiation tube <NUM> at the position SP15 at the first set position is excluded. In this case, the interval D_OP between the irradiation openings defined by the through holes <NUM> is an interval of at least one radiation tube <NUM>.

In this case, as illustrated in <FIG>, the ratio SD1/SD2 varies depending on the radiation tube <NUM>. Further, as described above, since the radiation tubes <NUM> are arranged in an arc shape, the side of the imaging surface <NUM> in the X direction is not parallel to the direction of the long side of the plate-like member <NUM>. Therefore, the size of the through hole <NUM> increases toward the end. Further, the through hole <NUM> has a trapezoidal shape in which the base is widened toward the end.

As illustrated in <FIG>, a plate-like member <NUM> with a linear shape may be used instead of the plate-like member <NUM> with an arc shape. In this case, the ratio SD1/SD2 varies depending on the radiation tube <NUM>. However, the side of the imaging surface <NUM> in the X-direction is parallel to the direction of the long side of the plate-like member <NUM>. Therefore, the size of the through hole <NUM> of the plate-like member <NUM> decreases toward the end. The shape of the through hole <NUM> is the same as a rectangular shape.

<FIG> is a table <NUM> summarizing the sizes and shapes of the through holes in the aspects illustrated in <FIG>. Patterns <NUM> to <NUM> indicate cases in which the radiation tubes <NUM> are arranged in a linear shape and patterns <NUM> and <NUM> indicate cases in which the radiation tubes <NUM> are arranged in an arc shape. Pattern <NUM> indicates an aspect of the plate-like member 180B illustrated in <FIG>. In this case, the through holes 181B have the same size and have the same rectangular shape. Pattern <NUM> indicates an aspect of the plate-like member 180A illustrated in <FIG>. In this case, the through holes 181A have different sizes and have the same trapezoidal shape. Pattern <NUM> indicates an aspect of the plate-like member 180A illustrated in <FIG>. In this case, the through holes 181A have the same size and have the same trapezoidal shape.

Pattern <NUM> indicates an aspect of the plate-like member <NUM> illustrated in <FIG>. In this case, the through holes <NUM> have different sizes and have the same trapezoidal shape. Pattern <NUM> indicates an aspect of the plate-like member <NUM> illustrated in <FIG>. In this case, the through holes <NUM> have different sizes and have the same rectangular shape.

The irradiation openings may be arranged at an interval of two or more radiation tubes <NUM>. However, in this case, since one irradiation opening is shared by two or more radiation tubes <NUM>, the number of times that, for example, the plate-like member is moved is two or more.

For example, in the first embodiment, the rack and pinion is described as an example of the displacement mechanism. However, the displacement mechanism is not limited thereto. Other known displacement mechanisms may be used.

Instead of the simple imaging in which the CC imaging illustrated in <FIG> and the MLO imaging illustrated in <FIG> are independently performed, a composite radiographic image equivalent to the radiographic image obtained by the simple imaging may be generated. The composite radiographic image is generated by performing a known composite image generation process, such as a minimum intensity projection method, for at least one of a plurality of projection images P obtained by the tomosynthesis imaging or a plurality of tomographic images T generated by the generation unit <NUM>.

In each of the above-described embodiments, the mammography apparatus <NUM> has been exemplified. In the related art, performing tomosynthesis imaging in the mammography apparatus <NUM> has been found to be useful as a method for easily finding lesions such as microcalcifications of the breast M. Therefore, it is preferable to apply the technique of the present disclosure to the mammography apparatus <NUM>.

Of course, the technology of the present disclosure is not limited to the mammography apparatus <NUM> and may be applied to other imaging apparatuses. For example, the technology of the present disclosure may be applied to an imaging apparatus <NUM> illustrated in <FIG> which captures the image of the subject H during surgery.

The imaging apparatus <NUM> comprises an apparatus main body <NUM> having a control device <NUM> provided therein and an arm <NUM> having a substantially C-shape in a side view. A carriage <NUM> is attached to the apparatus main body <NUM> such that the apparatus main body <NUM> can be moved. The arm <NUM> includes a radiation source accommodation portion <NUM>, a detector accommodation portion <NUM>, and a main body portion <NUM>. As in the mammography apparatus <NUM> illustrated in <FIG>, the radiation source accommodation portion <NUM> accommodates a radiation source <NUM> and an irradiation field limiter <NUM>. In addition, the detector accommodation portion <NUM> accommodates a radiation detector <NUM>. The radiation source accommodation portion <NUM> and the detector accommodation portion <NUM> are held by the main body portion <NUM> at a posture where they face each other.

The radiation source <NUM> and the radiation detector <NUM> have the same basic configurations as the radiation source <NUM> and the radiation detector <NUM> illustrated in <FIG>, respectively. However, the imaging apparatus <NUM> captures an image of an object, such as the entire chest of the subject H, which is larger than the breast M. Therefore, a radiation tube <NUM> forming the radiation source <NUM> has a larger diameter than each radiation tube <NUM> of the mammography apparatus <NUM>. In addition, the radiation detector <NUM> has an imaging surface <NUM> whose area is larger than that of the imaging surface <NUM> of the radiation detector <NUM>. The number of radiation tubes <NUM> arranged may increase in order to respond to the capture of the image of a large object.

The detector accommodation portion <NUM> is inserted below a bed <NUM> on which the subject H lies supine. The bed <NUM> is made of a material that transmits the radiation <NUM>. The radiation source accommodation portion <NUM> is disposed above the subject H at a position that faces the detector accommodation portion <NUM> with the subject H interposed therebetween.

The irradiation field limiter <NUM> of the imaging apparatus <NUM> has a plurality of irradiation openings for the radiation <NUM> which are arranged at an interval of at least one radiation tube <NUM>, similarly to the irradiation field limiter <NUM> of the mammography apparatus <NUM>. The position of the irradiation openings is moved to at least two set positions including a first set position in a case in which the radiation <NUM> is emitted from first radiation tubes which are some of three or more radiation tubes <NUM> and a second set position in a case in which the radiation <NUM> is emitted from second radiation tubes different from the first radiation tubes among the three or more radiation tubes <NUM>. The imaging apparatus <NUM> can also perform simple imaging using one radiation tube <NUM>, in addition to the tomosynthesis imaging. In addition, instead of the simple imaging, the imaging apparatus may generate a composite radiographic image. Further, the imaging apparatus <NUM> may capture both still radiographic images and moving radiographic images. Furthermore, reference numeral <NUM> indicates a housing for the radiation source <NUM>.

The technology of the present disclosure may be applied to a general radiography apparatus configured by combining a ceiling-suspended radiation source and an upright imaging table or a decubitus imaging table in which a radiation detector is set, in addition to the imaging apparatus <NUM> for surgery. Further, the technology of the present disclosure may be applied to, for example, a cart-type mobile radiography apparatus which is moved to each hospital room and is used to capture the image of the subject H.

In each of the above-described embodiments, the radiation tube <NUM> having one focus F is given as an example. However, the technology of the present disclosure is not limited thereto. A radiation tube having a plurality of focuses F may be used.

In the technology of the present disclosure, the above-described various embodiments and/or various modification examples may be combined with each other. In addition, the present disclosure is not limited to the above-described embodiments and various configurations can be used without departing from the scope of the claims.

The above descriptions and illustrations are detailed descriptions of portions related to the technology of the present disclosure and are merely examples of the technology of the present disclosure. For example, the above description of the configurations, functions, operations, and effects is the description of examples of the configurations, functions, operations, and effects of portions according to the technology of the present disclosure. Therefore, unnecessary portions may be deleted or new elements may be added or replaced in the above descriptions and illustrations without departing from the scope of the claims. In addition, in the above-described content and the above-illustrated content, the description of, for example, common technical knowledge that does not need to be particularly described to enable the implementation of the technology of the present disclosure are omitted in order to avoid confusion and facilitate the understanding of portions related to the technology of the present disclosure.

Claim 1:
A tomosynthesis imaging apparatus comprising:
a radiation source (<NUM>, <NUM>) in which three or more radiation tubes (<NUM>, <NUM>) emitting radiation are arranged to perform tomosynthesis imaging which irradiates an object with the radiation at a plurality of different irradiation angles; and
an irradiation field limiter (<NUM>, <NUM>) in which a plurality of irradiation openings (<NUM>) for the radiation that define an irradiation field of the radiation are arranged along an arrangement direction of the radiation tubes (<NUM>, <NUM>) at an interval of at least one radiation tube and a position of the irradiation openings (<NUM>) is moved to at least two set positions including a first set position in a case in which the radiation is emitted from first radiation tubes which are some of the three or more radiation tubes (<NUM>, <NUM>) and a second set position in a case in which the radiation is emitted from second radiation tubes different from the first radiation tubes among the three or more radiation tubes (<NUM>, <NUM>),
wherein
the irradiation field limiter (<NUM>, <NUM>) comprises a plate-like member (<NUM>) in which a through hole (<NUM>) functioning as the irradiation opening (<NUM>) is formed,
the plate-like member (<NUM>) is moved along the arrangement direction of the radiation tubes (<NUM>, <NUM>) to move the position of the irradiation openings (<NUM>) to the at least two set positions, and characterised in that
the plate-like member (<NUM>) has a convex portion (<NUM>) that protrudes toward the radiation tube (<NUM>, <NUM>) between the through holes (<NUM>) adjacent to each other.