WO2018168623A1

WO2018168623A1 - Radiation imaging apparatus

Info

Publication number: WO2018168623A1
Application number: PCT/JP2018/008911
Authority: WO
Inventors: Takaaki Gonda; Satoru Omura; Osamu Tsujii; Tetsuo Shimada; Shouichi Ibaraki; Akira Fujimoto
Original assignee: Canon Kabushiki Kaisha
Priority date: 2017-03-14
Filing date: 2018-03-08
Publication date: 2018-09-20
Also published as: JP2018149201A

Abstract

A breast radiation imaging apparatus includes a radiation generator that generates radiation, a radiation detector that detects radiation, a rotation frame that holds the radiation generator and the radiation detector, and a front cover arranged between an object and the rotation frame. The radiation imaging apparatus includes a slide member provided with a slide receiving surface that reduces frictional force of contact surfaces, between the front cover and any of the radiation generator, the radiation detector, and the rotation frame.

Description

RADIATION IMAGING APPARATUS

The present invention relates to a breast radiation imaging apparatus that performs breast CT imaging.

Generally, mammography apparatuses are used as radiographic examination apparatuses for breast cancer examination. However, it is known that the sensitivity and specificity of mammography decreases in the case of a dense breast (breast with many mammary glands) due to the overlapping of an affected area and mammary structures. Moreover, in order to reduce radiation exposure and obtain good images, breast images are captured with the breast being held and pressed between pressing panels, which may lead to a heavy burden on the object. As a technology for addressing these problems in mammography, tomosynthesis and breast CT (computer tomography) have been attracting attention. A feature of these two apparatuses is that they provide 3D images (tomographic images) of a breast without pressing the breast, thereby making it possible to observe the affected area and mammary structures separately.

[PTL 1] U.S. Patent No. 6480565
[PTL 2] Japanese Patent Laid-Open No. 2010-69241
In U.S. Patent No. 6480565 and Japanese Patent Laid-Open No. 2010-69241, breast radiation imaging apparatuses that perform breast CT imaging are disclosed.

A breast radiation imaging apparatus disclosed in U.S. Patent No. 6480565 includes a bed for image capturing provided with an opening at a position corresponding to breast, a frame that rotates in the periphery of the opening, and a radiation generator and a radiation detector that are mounted on the frame, and obtains a radiation image at each predetermined angle while rotating in the periphery of the opening. Then 3D images are created by performing reconstruction calculation on the obtained images. When the object presses her chest against the opening, pulls the breast from the chest wall, and arranges the breast in a breast housing unit, the entire breast can be set inside the capture range.

In Japanese Patent Laid-Open No. 2010-69241, a configuration is disclosed in which a pad that presses the back of the object is provided in the structure disclosed in U.S. Patent No. 6480565, in order to make a blind area in the vicinity of the breast base (chest wall) as small as possible and reduce blurring caused by body motion.

In order to reduce the size of the blind area in the vicinity of the breast base (chest wall) of the object, U.S. Patent No. 6480565 discloses a configuration in which the breast is pressed against the opening of the bed for image capturing to house the breast in the breast housing unit, and Japanese Patent Laid-Open No. 2010-69241 discloses a configuration in which the breast is pressed against a top plate by a pad that presses the object's back. The drawings in U.S. Patent No. 6480565 and Japanese Patent Laid-Open No. 2010-69241 show that a space exists between the top plate and the radiation generator, the radiation detector, or the frame, which rotate inside.

In the structures in U.S. Patent No. 6480565 and Japanese Patent Laid-Open No. 2010-69241, when the breast is pressed against the top plate, the top plate deflects inward of the imaging apparatus, and thus there is a possibility that the top plate will collide with an inner structure such as the radiation generator, radiation detector, or the frame that rotate. Also, if the thickness of the top plate is increased to enhance the rigidity so as not to collide with the inside structures, the blind area becomes larger by the amount of increase in the thickness of the plate.

The present invention has been made in view of the above-described problems, and provides a breast radiation imaging apparatus that can reduce the size of the blind area in the vicinity of the breast base and prevent a collision of the top plate with an inner structure even when breast CT imaging is performed by pressing the object's chest against the opening.

According to one aspect of the present invention, there is provided a breast radiation imaging apparatus, including a radiation generator that generates radiation, a radiation detector that detects the radiation, a rotation frame that holds the radiation generator and the radiation detector, and a front cover arranged between an object and the rotation frame, the breast radiation imaging apparatus comprising: a slide member provided with a slide receiving surface that reduces frictional force of a contact surface, between the front cover and any of the radiation generator, the radiation detector, and the rotation frame.

According to the present invention, it is possible to provide a breast radiation imaging apparatus that can reduce the blind area in the vicinity of the breast base and prevent a collision of the top plate with the inner structure even when breast CT imaging is performed by pressing the object's chest against the opening.

According to this radiation imaging apparatus, even when breast CT imaging is performed by strongly pressing the object's chest against the opening of the front cover, the front cover does not collide with an inner structure, and the size of the blind area in the vicinity of the breast base can be reduced. Moreover, since it is possible to perform radiation imaging in a larger range, it becomes possible to perform an examination in which oversight in the areas in the vicinity of the breast base, rib bones, and sides is reduced.

Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

FIG. 1 is a diagram schematically showing a radiation imaging apparatus according to a first embodiment.

FIG. 2 is a diagram schematically showing imaging by the radiation imaging apparatus according to the first embodiment.

FIG. 3 is a diagram showing a state in which a front cover has been removed from the radiation imaging apparatus according to the first embodiment.

FIG. 4 is a cross-sectional view of the vicinity of a rotation frame of the radiation imaging apparatus according to the first embodiment, and is an example of a cross-sectional view along a line I-I in FIG. 2.

FIG. 5 is a diagram illustrating the rotation frame in a plan view from the front cover side of the radiation imaging apparatus according to the first embodiment.

FIG. 6 is a diagram illustrating the vicinity of the rotation frame and an object position in a plan view from the front cover side of the radiation imaging apparatus according to the first embodiment.

FIG.7 is a cross-sectional view of the vicinity of the rotation frame of the radiation imaging apparatus according to the first embodiment, and is a cross-sectional view along a line I-I in FIG. 2.

FIG.8 is a cross-sectional view of the vicinity of the rotation frame of the radiation imaging apparatus according to the first embodiment, and a diagram showing an example of a cross-sectional view along a line I-I in FIG. 2.

FIG.9 is a cross-sectional view of the vicinity of the rotation frame of the breast radiation imaging apparatus according to the first embodiment, and is a cross-sectional view along a line I-I in FIG. 2.

FIG. 10 is a cross-sectional view of the vicinity of the rotation frame of the radiation imaging apparatus according to the first embodiment, and is a cross-sectional view along a line I-I in FIG. 2.

FIG. 11 is a diagram showing an example of the vicinity of the rotation frame in a plan view from the front cover side of the radiation imaging apparatus according to the first embodiment.

FIG. 12 is a cross-sectional view of the vicinity of the rotation frame of the radiation imaging apparatus according to the first embodiment, and is for schematically showing the configuration.

FIG. 13 is a flowchart showing the content of processing using rotation angle measurement of the radiation imaging apparatus according to the first embodiment.

FIG. 14 is a flowchart showing the content of processing using rotation speed measurement of the radiation imaging apparatus according to the first embodiment.

FIG. 15 is a flowchart showing the content of processing using rotation resistance measurement of the radiation imaging apparatus according to the first embodiment.

FIG. 16A is a flowchart showing the content of processing using pressing force measurement of the radiation imaging apparatus according to the first embodiment.

FIG. 16B is a flowchart showing the content of processing using pressing force measurement of the radiation imaging apparatus according to the first embodiment.

FIG. 17 is a cross-sectional view of the vicinity of the rotation frame of the radiation imaging apparatus according to the first embodiment, and is for schematically showing the configuration.

FIG. 18 is a cross-sectional view of the vicinity of a rotation frame of a radiation imaging apparatus according to a second embodiment, and is for schematically showing the configuration.

FIG. 19A is a flowchart showing the content of processing using mutual measurement of the radiation imaging apparatus according to the second embodiment.

FIG. 19B is a flowchart showing the content of processing using mutual measurement of the radiation imaging apparatus according to the second embodiment.

In the following, embodiments of the present invention will be described in detail with reference to the drawings. Note that the constituent elements described in these embodiments are merely exemplifications, and the technical scope of the present invention is defined by the claims and not limited by the individual embodiments in the following. Note that the drawings show a breast radiation imaging apparatus 1 to be used in a standing position in which imaging is performed while an object 100 is standing, but a similar configuration can be applied to a breast radiation imaging apparatus to be used in a lying position in which imaging is performed while the object 100 is lying. Also, FIGS. 5, 6, and 11 show the inner structure of the radiation imaging apparatus 1 with the front cover 2 omitted.

First embodiment
FIG. 1 is a diagram schematically showing a breast radiation imaging apparatus 1 that can perform breast CT imaging according to a first embodiment. FIG. 2 is a diagram schematically showing breast CT imaging of an object 100 using the breast radiation imaging apparatus that is capable of breast CT imaging according to the first embodiment. FIG. 3 is a diagram showing the state where a front cover 2 has been removed from the radiation imaging apparatus 1 shown in FIG. 1. Also, FIG. 4 is a cross-sectional view along the line I-I in FIG. 2, and schematically shows the vicinity of a rotation frame 4. The structure that is not related to the present invention is not shown.

Breast CT imaging is performed by the object 100 pressing a breast against an opening 3 provided in a front cover 2 of the radiation imaging apparatus 1. Inside the radiation imaging apparatus 1, radiation images are captured at a predetermined angle, while a rotation frame 4, and a radiation generator 5 and a radiation detector 6 that detects radiation that passed through the breast, which are mounted at opposing positions on the rotation frame 4, are rotating around the opening 3 due to a rotation frame drive mechanism 10. The radiation generator 5 and the radiation detector 6 are arranged on the front cover 2 side relative to the rotation frame 4. The rotation frame drive mechanism 10 includes a drive source such as a motor, and a power transmission unit such as a belt, a gear, a shaft, and a bearing, which are not shown in detail. The rotation frame drive mechanism 10 and the rotation frame 4 are held in the radiation imaging apparatus 1 in a rotatable state by a fixing unit 8. The radiation imaging apparatus 1 creates a breast CT image (tomographic image) by performing reconstruction calculation on a plurality of captured radiation images.

As described above, since the plurality of radiation images are reconstructed, if the object 100 moves during the imaging, a blurring caused by the body motion will appear. Therefore, it is preferable that the rotation speed of the radiation generator 5 and the radiation detector 6 is fast such that a predetermined number of images can be captured in as short time as possible. Also, in order to reduce the size of the blind area (missing image portion) in the vicinity of the breast base (chest wall) and the like of the object 100, it is preferable to arrange the radiation generator 5 and the radiation detector 6 as close to the object 100 as possible. In this way, in order to protect the object 100 from the rotation frame 4 rotating near the object 100, it is necessary to provide the front cover 2. The front cover 2 needs material rigidity in view of the protection of the object and the blind area, and therefore the front cover 2 is composed of a metal material such as stainless steel, iron, or an aluminum alloy, or a reinforced resin material such as CRPR or GFRP are used. Also, since the radiation generator 5 is close to the object 100, in view of radiation protection, a material with relatively low radiation transmittance such as lead, copper, tungsten, or molybdenum is arranged in portions in some cases.

The radiation imaging apparatus according to the present embodiment includes a slide member 7 which is provided with a slide receiving surface 71 that reduces frictional force of the contacting surface between the front cover 2 and the radiation generator 5, radiation detector 6, and rotation frame 4, which form a rotating structure. Although a material with high rigidity is used for the front cover 2, deflection may be caused by pressing by the object 100 because of the thinness and large size of the cover. Due to the slide receiving surface 71 provided between the front cover 2 and the slide member 7, it is possible to realize the radiation imaging apparatus 1 according to which the blind area in the vicinity of the breast base is small and the front cover 2 and the rotating structure do not collide with each other at the time of pressing by the object 100.

It is possible to use a washer, a sheet member, a plate member, or the like as the slide member 7. It is possible to use a material such as a resin material that is excellent in wear characteristics and slide characteristics such as fluorine resin or high-molecular weight polyethylene resin, a high-hard ceramic which is excellent in wear characteristics, or a laminate material using the above-described resin or ceramics and a metal, or the like, as the slide member 7. It is also possible to use a metal thrust bearing as the slide member 7. Due to the above-described slide member 7, even if the front cover 2 is pressed against the radiation generator 5, the radiation detector 6, or the rotation frame 4, which form a rotating structure, the frictional force (rotation resistance) of the slide receiving surface 71 is small and the rotating structure can be rotated smoothly.

FIGS. 5 and 6 are diagrams illustrating the vicinity of the rotation frame 4 in a plan view from the front cover 2 side of the radiation imaging apparatus 1 according to the first embodiment, and shows an example of arrangement of the slide member 7. Also, FIG. 7 is a cross-sectional view of the vicinity of the rotation frame 4 of the radiation imaging apparatus 1 when the arrangement of the slide member 7 shown in FIG. 6 is implemented, and is a cross-sectional view taken along the line I-I in FIG. 2.

In the configuration example of the radiation imaging apparatus 1 shown in FIG. 5, the slide members 7 are arranged closer to the opening 3 than in the configuration example in FIG. 3. Although peripheral portion of the front cover 2 is fixed to the exterior structure of the radiation imaging apparatus 1, the vicinity of the opening 3 in the center of front cover 2 is not fixed by the structure, and therefore deflection increases structurally. By arranging the slide members 7 near the opening 3, it is possible to provide the slide receiving surface 71 that is effective to support the front cover 2 and suppress deflection.

FIG. 6 illustratively shows the positional relation between the position of the object 101 at the time of breast CT imaging and the arrangement of the slide members 7. The deflection of the front cover 2 becomes large especially at the pressing portions of the object 100 (head, body, four limbs, and the like of the object 100) at the time of imaging. By arranging the slide members 7 near the above-described pressing parts, it is possible to provide the effective slide receiving surfaces 71. Also, by fixing the slide members 7 to the front cover 2 and providing the slide receiving surfaces 71 between the slide members 7 and the rotation frame 4 as shown in FIG. 7, it is possible to stabilize the position of the slide receiving surfaces 71 relative to the object 101 at the time of imaging.

FIGS. 8, 9, and 10 illustratively show cross-sectional views along the line I-I in FIG. 2 at the time of implementing the arrangement of the slide members 7, and show examples of fixing of the slide members 7 and arrangement positions of the slide receiving surfaces 71 are respectively shown. Also, FIG. 11 is a diagram showing the vicinity of the rotation frame 4 in a plan view from the front cover 2 side of the radiation imaging apparatus 1 when the slide members 7 shown in FIG. 10 are arranged.

In the configuration example of the radiation imaging apparatus 1 shown in FIG. 8, the slide members 7 are fixed to both the front cover 2 side and the rotation frame 4 side respectively, and the slide receiving surfaces 71 are provided between the slide members 7. Due to the slide receiving surfaces 71 that can reduce the frictional force (rotation resistance) of contact surfaces, the frictional coefficients of both the two contact surfaces are small and excellent in frictional characteristics and slide characteristics, and thus maximum effect can be obtained.

However, if the slide members 7 are fixed to only either the front cover 2 side or the rotation frame 4, it is necessary to cut and polish, or plate a large surface so as to reduce the frictional coefficient of the surface on the structure side without the slide member 7 which comes into contact with the slide receiving surfaces 71, and thus the processing cost may increase. By providing the slide receiving surfaces 71 between the slide members 7 as shown FIG. 8, it is possible to provide the slide receiving surfaces 71 according to which the processing cost is suppressed and both contacting surfaces are small in frictional coefficient and excellent in wear characteristics and slide characteristics, and thus it is possible to rotate the rotation frame 4 smoothly.

In the configuration example of the radiation imaging apparatus 1 shown in FIG. 9, the peripheral portion of the opening 3 of the front cover 2 is extended to the rotation frame 4 along the rotation axis direction, and the slide members 7 are arranged between the front cover 2 and the rotation frame 4. As described with reference to FIG. 5, the vicinity of the opening 3 in the center of the front cover 2 has a large deflection because of the structure. Also, if the slide receiving surfaces 71 are provided near the object 100, vibration, frictional noise and frictional heat and the like caused by rotation of the rotation frame 4 may give the object 100 a feeling of discomfort. By arranging the slide members 7 near the opening 3 as shown in FIG. 9 so as to separate the object 100 from the slide receiving surface 71, it is possible to support the deflection of the front cover 2 effectively, and thus reduce the feeling of discomfort given to the object 100. Also, if the front cover 2 is extended to the rotation frame 4 as shown in FIG. 9, a part comes within the radiation emission area 9. Therefore, the part of the front cover 2 that comes within in the radiation emission area 9 is designed such that an opening is provided, or the material is changed to a resin with high radiation transmittance or the like.

In the configuration examples of the radiation imaging apparatus 1 shown in FIGS. 10 and 11, the radiation generator 5 and the radiation detector 6 are mounted on the front cover 2 side relative to the rotation frame 4, and the slide members 7 are arranged between the front cover 2 and the radiation generator 5 and radiation detector 6. Even in the case where the slide receiving surfaces 71 are provided according to the arrangement of the slide members 7 that are excellent in wear characteristics and slide characteristics, the frictional force (rotation resistance) is generated more or less. Also, in order to reduce the size of the blind area in the vicinity of the breast base of the object 100, the radiation generator 5 and the imaging area of the radiation detector 6 should be close to the object 100.

Therefore, by arranging the slide members 7 only on the front cover 2, and the radiation generator 5 and radiation detector 6, it is possible to reduce the size of area of the slide receiving surfaces 71, and moreover, reduce the rotation resistance. At this time, by keeping the rotation frame sufficiently separated from the front cover 2, it is possible to prevent the rotation frame 4 from colliding with the front cover 2 at the time of pressing by the object 100.

FIG. 12 is a cross-sectional view of the vicinity of the rotation frame 4 of the radiation imaging apparatus 1, and schematically shows the configuration. The arrows in the figure show information transmission between the components. The radiation imaging apparatus 1 includes a radiation controller 11 that controls the emission of radiation from the radiation generator 5, and a detector controller 12 that controls radiation image capture by controlling the driving of image capture by the radiation detector 6.

Also, the rotation frame drive mechanism 10 includes a rotation angle measurement unit 13 that measures the rotation angle of the rotation frame 4, a rotation speed measurement unit 14 that measures the rotation speed, a rotation resistance measurement unit 15 that measures rotation resistance (rotation torque), and a rotation drive controller 16 that controls the rotation frame drive mechanism 10.

The rotation angle measurement unit 13 and the rotation speed measurement unit 14 perform measurement using a rotary encoder, a gyrosensor, or the like. In the rotation resistance measurement unit 15, the magnitude of the rotation resistance applied to the rotation frame drive mechanism 10 can be measured by providing a rotation torque measurement device in the power transmission path of the rotation frame drive mechanism 10. Moreover, a pressing force measurement unit 17 that measures the force by which the front cover 2 presses the rotation frame 4 is provided in the rotation frame drive mechanism 10. The pressing force measurement unit 17 measures a load applied in the thrust direction (axis direction) on the slide receiving surface 71 and the rotation frame drive mechanism 10. The measurement results from the rotation angle measurement unit 13, the rotation speed measurement unit 14, the rotation resistance measurement unit 15, and the pressing force measurement unit 17 are input to the rotation drive controller 16.

In addition, the radiation imaging apparatus 1 is provided with a imaging controller 18 that controls and coordinates the radiation controller 11, a detector controller 12, and a rotation drive controller 16, and a notification unit 19 that notifies an operator of the state of the imaging apparatus (power on/off, sleep state, imaging preparation completion, radiation information, radiation emission state, image obtaining, image transfer, image reconstruction calculation, warning, and the like) by light, sound, or the like.

In breast CT imaging, the radiation generator 5 and the radiation detector 6 rotate around the opening 3 and obtain radiation images at each predetermined angle, perform reconstruction calculation on the obtained images, and generate 3D images (tomographic images).

During radiation image obtaining, due to changes in the amount of deflection of the front cover 2 and the frictional force of the slide receiving surface 71 depending on the pressing state of the object 100, there is possibility that the rotation speed of the rotation frame 4 will not be constant. At this time, due to the angle information from the rotation angle measurement unit 13 and the detector controller 12, the radiation generator 5 and the radiation detector 6 mounted on the rotation frame 4 can obtain radiation images at the timing at which a predetermined angle is reached. FIG. 13 shows a flowchart of control using the rotation angle measurement.

In step S101, when a CT imaging start instruction is input, then in step S102, rotation angle measurement is started by the rotation angle measurement unit 13. At this time, it is confirmed that the rotation frame 4 is at the predetermined initial position, and the rotation angle is set as the initial value.

Next, in step S103, rotation of the rotation frame 4 is started. In step S104, the imaging controller 18 determines whether or not the rotation angle of the rotation frame 4 is at the predetermined angle at which a radiation image is to be obtained. If the rotation angle is not the predetermined angle (S104-No), the processing advances to step S110 and the imaging controller 18 perform control such that the rotation drive of the rotation frame 4 is continued.

Then, the processing advances to step S104 and similar processing is repeated. If the rotation angle is the predetermined angle (S104-Yes) in the determination in step S104, the processing advances to step S105. The detector controller 12 can control the radiation image capture timing of the radiation detector 6 according to the rotation angle of the rotation frame 4. In step S105, radiation emission by the radiation generator 5 and the radiation controller 11, and radiation image obtaining by the radiation detector 6 and the detector controller 12, are performed at the same time based on the control by the imaging controller 18.

Next, in step S106, the imaging controller 18 determines whether or not the rotation angle of the rotation frame 4 is the initial value that was set in step S102. If the rotation angle is not the initial value (S106-No), the processing advances to step S110, and similar processing is repeated. On the other hand, if the rotation angle of the rotation frame 4 is the initial value that was set in step S102 (S106-Yes) in the determination in step S106, the processing advances to step S107.

In step S107, the imaging controller 18 causes rotation of the rotation frame 4 to be stopped, in step S108, the measurement of the rotation angle using the rotation angle measurement unit 13 is ended, and in step S109, CT imaging is ended.

Due to the above-described control according to the rotation angle of the rotation frame 4, radiation image obtaining can be performed by pulse emission instead of continuous emission of radiation, and thus the radiation exposure level of the object 100 can be reduced.

Furthermore, it is also possible to perform feedback control to stabilize the rotation speed of the rotation frame 4 due to the rotation speed information from the rotation speed measurement unit 14 and the rotation drive controller 16. FIG. 14 shows a flowchart of control using the rotation speed measurement.

In step S201, when a CT imaging start instruction is input, then in step S202, the rotation angle measurement unit 13 performs rotation angle measurement, the imaging controller 18 confirms that the rotation frame 4 is at the predetermined initial position based on the measurement result from the rotation angle measurement unit 13, and in step S203, rotation speed measurement is started by rotation speed measurement unit 14. In step S204, rotation of the rotation frame 4 and radiation image obtaining performed by the radiation detector 6 are started at the same time.

In step S205, the imaging controller 18 compares a rotation speed v of the rotation frame with a predetermined speed V0 (reference speed) that has been set in advance. When v＜V0, the processing advances to step S206, and the imaging controller 18 increases the motor output of the rotation frame drive mechanism 10. When v=V0, the processing advances to step S207, and the imaging controller 18 maintains the motor output of the rotation frame drive mechanism 10. When v＞V0, the processing advances to step S208, and the imaging controller 18 decreases the output of the motor of the rotation frame drive mechanism 10.

The processing advances from any of steps S206 to S208 to step S209, and the imaging controller 18 determines whether or not the position of the rotation frame 4 is the initial position. If the position is not the initial position (S209-No), the processing advances to step S205, and similar processing is repeated. On the other hand, if the position of the rotation frame 4 is the initial position (S209-Yes) in the determination in step S209, the processing advances to step S210.

In step S210, the imaging controller 18 performs control such that rotation of the rotation frame 4 and radiation image obtaining performed by the radiation detector 6 are stopped, in step S211, rotation speed measurement by the rotation speed measurement unit 14 is ended, and in step S212, CT imaging is ended.

By controlling the rotation speed of the rotation frame 4, it is possible to match the timing at which the radiation generator 5 and the radiation detector 6 reach a predetermined angle and the radiation image obtaining at a constant frame rate based on the imaging start time.

As described above, the frictional force of the slide receiving surface 71 changes depending on the pressing state of the object 100, and therefore excessive rotation resistance may be generated in the slide member 7 and the rotation frame drive mechanism 10. Therefore, the rotation resistance value is measured by the rotation resistance measurement unit 15, and the drive of the rotation frame 4 is controlled. FIG. 15 shows a flowchart of control using the rotation resistance measurement.

In step S301, when CT imaging start instruction is input, in step S302, the rotation angle measurement unit 13 performs the rotation angle measurement, and the imaging controller 18 confirms that the rotation frame 4 is at the predetermined initial position based on the measurement result from the rotation angle measurement unit 13, and in step S303, the rotation resistance measurement is started by the rotation resistance measurement unit 15. In step S304, rotation of the rotation frame 4 is started.

In step S305, the imaging controller 18 determines whether or not the rotation resistance value is greater than or equal to a threshold. Regarding the threshold, a rotation resistance value is set in advance considering the wear characteristics of the slide member 7 and the drive performance of the rotation frame drive mechanism 10, for example. If the rotation resistance value is less than the threshold (S305-No), the processing advances to step S306, and the imaging controller 18 determines whether or not the position of the rotation frame 4 is the initial position. If the position of the rotation frame 4 is not the initial value (S306-No), in step S310, the imaging controller 18 performs control so as to maintain the rotation drive of the rotation frame 4. Then, the processing advances to step S305 and similar processing is repeated.

On the other hand, if the position of the rotation frame 4 is the initial value (S306-Yes) in the determination in step S306, in step S307, the imaging controller 18 performs control so as to stop rotation of the rotation frame 4, and in step S308, ends the rotation resistance measurement by the rotation resistance measurement unit 15, and in step S309, ends CT imaging.

If the rotation resistance value is greater than or equal to the threshold (S305-Yes) in the determination in step S305, the processing advances to step S311, and the notification unit 19 notifies (warns) the operator that the rotation resistance value is greater than or equal to the threshold. Thereafter, in step S312, when the rotation resistance becomes greater than or equal to the threshold during radiation image capture, rotation of the rotation frame 4 and radiation emission are stopped. The radiation controller 11 causes the radiation generator 5 to stop the radiation emission, and the rotation drive controller 16 controls the rotation frame drive mechanism 10 such that rotation of the rotation frame 4 is stopped. In step S313, the rotation resistance measurement by the rotation resistance measurement unit 15 is stopped, and in step S314, the CT imaging is stopped.

Due to the above-described control by the rotation resistance measurement performed on the rotation frame drive mechanism 10, it is possible to maintain the imaging apparatus and prevent unnecessary radiation exposure on the object 100.

In addition, the pressing force of the object 100 changes during radiation image obtaining, and there is a possibility excessive load will be generated on the slide member 7 and the rotation frame drive mechanism 10. In view of this, the pressing force of the front cover 2 on the rotation frame 4 is measured by the pressing force measurement unit 17, and the drive of the rotation frame 4 is controlled. FIGS. 16A and 16B show flowcharts of control using the pressing force measurement.

In step S401, when a CT imaging setting instruction is input, then in step S402, pressing force measurement by the pressing force measurement unit 17 is started. In step S403, the imaging controller 18 determines whether or not the pressing force is greater than or equal to a threshold based on the measurement result from the pressing force measurement unit 17. Regarding the threshold, for example, a pressing force is set in advance considering the load resistant performance of the slide member 7 and the structure of the rotation frame drive mechanism 10. If the pressing force is greater than or equal to the threshold (S403-Yes), the processing advances to step S404, and the notification unit 19 notifies (warns) the operator that the pressing force is greater than or equal to the threshold. Thereafter, in step S405, the imaging controller 18 performs control such that rotation of the rotation frame 4 is prohibited, and the processing advances to step S403. In the determination in step S403, if the pressing force is less than the threshold (S403-No), the processing advances to step S406, and the imaging controller 18 determines whether or not the CT imaging start instruction has been input. If the instruction has not been input (S406-No), the processing advances to step S403, and similar processing is repeated.

In the determination in step S406, if the instruction is input (S406-Yes), the processing advances to step S407, the rotation angle measurement unit 13 performs the rotation angle measurement, and the imaging controller 18 confirms that the rotation frame 4 is at the predetermined initial position based on the measurement result from the rotation angle measurement unit 13. In step S408, under the control of the imaging controller 18, rotation of the rotation frame 4 and the drive of the radiation detector 6 are started, and CT imaging is started.

In step S409 the imaging controller 18 determines whether or not the pressing force is greater than or equal to the threshold based on the measurement result from the pressing force measurement unit 17. If the pressing power is less than the threshold (S409-No), the processing advances to step S410, the rotation angle measurement unit 13 performs the rotation angle measurement, and the imaging controller 18 determines whether or not the position of the rotation frame 4 is the initial position based on the measurement result from the rotation angle measurement unit 13. If the position of the rotation frame 4 is not the initial position (S410-No), in step S414, the imaging controller 18 performs controls so as to continue the rotation drive of the rotation frame 4. Then, the processing advances to step S409, and similar processing is repeated.

On the other hand, if the position of the rotation frame 4 is the initial position (S410-Yes) in the determination in step S410, then in step S411, under the control of the imaging controller 18, rotation of the rotation frame 4 and the radiation emission are stopped, and in step S412, pressing force measurement performed by the pressing force measurement unit 17 is ended, and in step S413, CT imaging is ended.

If the pressing force is greater than or equal to the threshold in step S409, (S409-Yes), the processing advances to step S415, and the notification unit 19 notifies (warns) the operator that the pressing force is greater than or equal to the threshold. Thereafter, in step S416, under the control of the imaging controller 18, rotation of the rotation frame 4 and radiation emission are stopped, and in step S417, pressing force measurement performed by the pressing force measurement unit 17 is stopped, and in step S418, CT imaging is stopped.

Unlike the rotation resistance, the pressing force can be measured during the setting for imaging, and therefore the setting work for imaging can be performed efficiently. Also, due to the above-described control using the pressing force measurement performed on the rotation frame drive mechanism 10, it is possible to maintain the integrity of the imaging apparatus and prevent unnecessary radiation exposure of the object 100.

In the radiation imaging apparatus 1 according to the present embodiment, it is possible to use the rotation frame drive mechanism 10 that controls the rotation angle and the rotation speed with high accuracy and that can output high torque in response to rotation resistance generated due to having the slide member 7. It is possible to use a stepping motor or a servo motor that can realize high control performance and high torque as the motive power source of the rotation frame drive mechanism 10, and to perform drive control by a mechanism such as a motor controller and driver, or a PLC (programmable logic controller).

Second embodiment
Next, the configuration of a radiation imaging apparatus according to a second embodiment of the present invention will be described. FIGS. 17 and 18 are cross-sectional views of the vicinity of the rotation frame 4 of the radiation imaging apparatus 1, and schematically show the configuration of the second embodiment. Distance sensors (distance measurement units) for measuring the relative positions of (relative distance between) the rotation frame 4 and the fixing unit 8 that holds the rotation frame 4 are provided on the fixing unit 8. For example, an infrared sensor, an ultrasonic sensor, or the like can be used as the distance sensors. Distance sensors (radial direction) 20 (distance measurement units in a radial direction) that measure the distance in a direction that is perpendicular to and intersects a design rotation axis A-A of the rotation frame 4 and is orthogonal to a center point of the opening 3, and distance sensors (thrust direction) 21 (distance measurement units in a thrust direction) that measure the distance in a thrust direction along the design rotation axis A-A are arranged. The distance sensors 20 (radial distance measurement units) measure the relative distance between the rotation frame 4 and the fixing unit 8 in the radial direction that intersects the rotation axis (design rotation axis A-A) of the rotation frame in the state where an external load is not applied to the rotation frame 4. Also, the distance sensors 21 (thrust distance measurement units) measure the relative distance between the rotation frame 4 and the fixing unit 8 in the thrust direction along the rotation axis (design rotation axis A-A) of the rotation frame. Here, the design rotation axis A-A of the rotation frame 4 indicates the ideal rotation axis which was defined when the rotation frame 4 of the radiation imaging apparatus 1 was designed, and the rotation axis of the rotation frame 4 in the state where an external load is not added to the rotation frame 4.

The rotation frame drive mechanism 10 has some leeway (allowance) to allow the rotation frame 4 to rotate smoothly. Therefore, as shown in FIG. 18, a rotation axis B-B of the rotation frame 4 may change depending on the pressing state of the object 100.

In view of this, when obtaining the radiation images, by measuring the distances in the above-described radial and thrust directions, information about the relative positions of the rotation frame 4 (radiation generator 5, radiation detector 6) and the fixing unit 8 is stored. When performing reconstruction calculation on the captured radiation images to generate 3D images (tomographic images), The imaging controller 18, performs image correction (tilt correction, position correction, distortion correction, and the like) on the image obtained along the rotation axis B-B of the rotation frame 4 to obtain an image in the state where the image is captured along the design rotation axis A-A, using the relative positions. That is, the imaging controller 18 functions as an image processing unit, and when performing reconstruction calculation on the radiation images to generate 3D images (tomographic images), based on the measurement result of the relative positions of (relative distance between) the rotation frame 4 and fixing unit 8, performs image correction on the images obtained by the rotation about the rotation axis (rotation about the rotation axis B-B) in the state where the external load acts on the rotation frame 4 to obtain images obtained by rotation about the rotation axis in the state where the external load does not act on the rotation frame 4(rotation about the rotation axis A-A).

A memory unit 22 (storage unit) stores a distance table in which the relationship between the relative positions indicating the relative distance between the rotation frame 4 and the fixing unit 8, which is obtained from the distance sensors (distance measurement units), and conditions of image correction is set in advance. The imaging controller 18 that functions as an image processing unit references the distance table in the memory unit 22 (storage unit), obtains a condition of image correction corresponding to the relative positions measured by the distance sensors (radial distance measurement units and thrust distance measurement units), and executes image correction.

In addition, depending on the relative positions of the rotation frame 4 and the fixing unit 8, there is a possibility that a deflection from the design rotation axis A-A is large, and thus appropriate 3D images cannot be created even if the obtained images are corrected. In view of this, the relative positions of the rotation frame 4 and the fixing unit 8 are measured, and CT imaging drive is controlled. FIGS. 19A and 19B show flowcharts of control using the relative position measurement.

In step S501, when a CT imaging setting instruction is input, then in step S502, measurement of the relative positions of the rotation frame 4 and the fixing unit 8 using the distance sensors (distance measurement units) is started. In step S503, the imaging controller 18 reads the data in the distance table stored in the memory unit 22. In step S504, the imaging controller 18 determines whether or not appropriate 3D images (tomographic images) can be created at the relative positions measured by the distance sensors, according to the distance table. For example, if the relative positions measured by the distance sensors exceed the relative positions stored in the distance table, that is, if data corresponding to the relative positions of the measurement result is not stored in the distance table, the imaging controller 18 determines that appropriate 3D images (tomographic images) cannot be generated. If data corresponding to the relative positions of the measurement result is stored in the distance table, the imaging controller 18 determines that appropriate 3D images (tomographic images) can be created.

If appropriate 3D images cannot be created (S504-No), the processing advances to step S505, and the notification unit 19 notifies (warns) the operator that the measured relative positions are out of the image correction range. That is, the notification unit 19 notifies that the relative positions measured by the distance sensors (radial distance measurement units and thrust distance measurement units) exceed the relative positions stored in the distance table. Thereafter, in step S506, radiation emission is prohibited, and the processing advances to step S504.

If the appropriate 3D images can be created according to the determination in step S504 (S504-Yes), the processing advances to step S507, and the imaging controller 18 determines whether or not the CT imaging start instruction has been input. If the instruction has not been input (S507-No), the processing advances to step S504, and similar processing is repeated. If the instruction has been input (S507-Yes), the processing advances to step S508, the rotation angle measurement unit 13 performs rotation angle measurement, and the imaging controller 18 confirms that the rotation frame 4 is at the predetermined initial position based on the measurement result from the rotation angle measurement unit 13. In step S509, rotation of the rotation frame 4 and drive of the radiation detector 6 are started, and thus CT imaging is started.

In step S510, the imaging controller 18 determines whether or not appropriate 3D images (tomographic images) can be generated through the image correction at the relative positions measured by the distance sensors, according to the distance table. If appropriate 3D images can be created (S510-yes), processing advances to step S511, the rotation angle measurement unit 13 performs the rotation angle measurement, and the imaging controller 18 determines whether or not the position of the rotation frame 4 is the initial position based on the measurement result from the rotation angle measurement unit 13. If the position of the rotation frame 4 is not the initial position (S511-No), in step S515, the imaging controller 18 performs control to maintain CT imaging, the processing advances to step S510, and similar processing is repeated. On the other hand, if the position is the initial position (S511-Yes) in the determination in step S511, in step S512, under the control of the imaging controller 18, rotation of the rotation frame 4 and radiation emission are stopped, and in step S513, the relative position measurement performed by the distance sensors (distance measurement units) is ended, and in step S514, CT imaging is ended.

If appropriate 3D images cannot be created in S510 (S510-No), the processing advances to step S516, and the notification unit 19 notifies (warns) the operator that the relative positions are out of the image correction range. Thereafter, in step S517, under the control of the imaging controller 18, rotation of the rotation frame 4 and radiation emission are stopped, in step S518, the relative position measurement performed by the distance sensors (distance measurement units) is stopped, and in step S519, CT imaging is stopped.

Since the relative position can be measured during the setting for imaging, the setting work for imaging can be performed efficiently. Also, unnecessary radiation exposure of the object 100 can be prevented.

The embodiments of the present invention have been described in detail above, but the technical scope of this invention is not limited to the embodiments. In the present invention, various changes are possible without departing from the spirit of the invention, and such modifications are also encompassed in the technical scope of this invention.

According to the embodiments of the present invention, it is possible to provide a breast radiation imaging apparatus that can reduce the size of the blind area in the vicinity of the breast base and prevent a collision of the top plate with an inner structure even when breast CT imaging is performed by pressing the object's chest against the opening.

Other Embodiments
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a 'non-transitory computer-readable storage medium') to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)^TM), a flash memory device, a memory card, and the like.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2017-049058, filed March 14, 2017, which is hereby incorporated by reference herein in its entirety.

Claims

A breast radiation imaging apparatus, including a radiation generator that generates radiation, a radiation detector that detects the radiation, a rotation frame that holds the radiation generator and the radiation detector, and a front cover arranged between an object and the rotation frame, the breast radiation imaging apparatus comprising:
a slide member provided with a slide receiving surface that reduces frictional force of a contact surface, between the front cover and any of the radiation generator, the radiation detector, and the rotation frame.
The radiation imaging apparatus according to claim 1, wherein the radiation generator and the radiation detector are arranged on a front cover side relative to the rotation frame, and the slide member is arranged between the front cover and any of the radiation generator and the radiation detector.
The radiation imaging apparatus according to claim 1,
wherein the slide member is fixed to any of the radiation generator, the radiation detector, and the rotation frame, and
the slide receiving surface is provided between the slide member and the front cover.
The radiation imaging apparatus according to claim 1,
wherein the slide member is fixed to the front cover, and
the slide receiving surface is provided between the slide member and any of the radiation generator, the radiation detector, and the rotation frame.
The radiation imaging apparatus according to claim 1,
wherein the slide member is fixed to the front cover and any of the radiation generator, the radiation detector, and the rotation frame, and
the slide receiving surface is provided between the slide member fixed to the front cover and the slide member fixed to any of the radiation generator, the radiation detector, and the rotation frame.
The radiation imaging apparatus according to claim 1, further comprising:
a rotation angle measurement unit that measures a rotation angle of the rotation frame; and
a detector controller that controls radiation image capture performed by the radiation detector,
wherein the detector controller controls a timing of radiation image capture of the radiation detector according to the rotation angle.
The radiation imaging apparatus according to claim 6, further comprising:
a radiation controller that controls radiation emission performed by the radiation generator,
wherein if the rotation angle is an angle at which a radiation image is to be obtained, the radiation controller controls radiation emission performed by the radiation generator, and
the detector controller controls the radiation detector to obtain a radiation image.
The radiation imaging apparatus according to claim 7, further comprising:
a rotation speed measurement unit that measures a rotation speed of the rotation frame;
a rotation frame drive mechanism that rotates the rotation frame; and
a rotation drive controller that controls the rotation frame drive mechanism,
wherein the rotation drive controller controls the rotation speed of the rotation frame so as to be constant based on a measurement result from the rotation speed measurement unit.
The radiation imaging apparatus according to claim 8, further comprising a rotation resistance measurement unit that measures a rotation resistance of the rotation frame drive mechanism.
The radiation imaging apparatus according to claim 9, further comprising a notification unit that notifies that the rotation resistance is greater than or equal to a threshold based on a measurement result from the rotation resistance measurement unit.
The radiation imaging apparatus according to claim 10, wherein if the rotation resistance is greater than or equal to the threshold during radiation image capturing, the radiation controller causes the radiation generator to stop the radiation emission, and the rotation drive controller controls the rotation frame drive mechanism such that rotation of the rotation frame is stopped.
The radiation imaging apparatus according to claim 10, further comprising a pressing force measurement unit that measures a pressing force of the front cover on the rotation frame.
The radiation imaging apparatus according to claim 12, wherein the notification unit notifies that the pressing power is greater than or equal to a threshold.
The radiation imaging apparatus according to claim 12, wherein if the pressing force is greater than or equal to a threshold, the radiation controller causes the radiation generator to stop radiation emission, and the rotation drive controller controls the rotation frame drive mechanism such that rotation of the rotation frame is prohibited or stopped.
The radiation imaging apparatus according to claim 10, further comprising:
a fixing unit that holds the rotation frame in a rotatable state;
a radial distance measurement unit that measures a relative distance between the rotation frame and the fixing unit in a direction that intersects a rotation axis of the rotation frame in a state where an external load does not act on the rotation frame; and
a thrust distance measurement unit that measures a relative distance between the rotation frame and the fixing unit in a direction along the rotation axis.
The radiation imaging apparatus according to claim 15, further comprising:
an image processing unit that generates a tomographic image by performing reconstruction calculation on radiation images,
wherein the image processing unit, in generating the tomographic image, performs image correction on images obtained by rotation around a rotation axis in a state where an external load acts on the rotation frame, to obtain images obtained by rotation around a rotation axis in a state where an external load does not act on the rotation frame.
The radiation imaging apparatus according to claim 16, further comprising:
a storage unit that stores a distance table in which a relationship between relative positions indicating a relative distance between the rotation frame and the fixing unit and a condition of the image correction is set in advance,
wherein the image processing unit references the distance table in the storing unit, obtains a condition of an image correction that corresponds to relative positions measured by the radial distance measurement unit and the thrust distance measurement unit, and executes the image correction.
The radiation imaging apparatus according to claim 17, wherein the notification unit notifies that the relative positions measured by the radial distance measurement unit and the thrust distance measurement unit exceed the relative positions stored in the distance table.
The radiation imaging apparatus according to claim 18, wherein if the measured relative positions exceed the relative positions stored in the distance table, the radiation controller prohibits or stops radiation emission performed by the radiation generator, and the rotation drive controller controls the rotation frame drive mechanism such that rotation of the rotation frame is stopped.