JP2015097692A - Mammographic tomography apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mammographic tomography apparatus capable of radiography up to a base part of a breast by making a detection area of a radiation detector closer to a subject side.SOLUTION: In a mammographic tomography apparatus comprising: a gantry 2 having a front plate 7 on which a breast inlet/outlet 17 for putting a breast 15 into/out from a breast storage part 3 is opened; a radiation generation tube 8 and a radiation detector 11 which are oppositely provided with the breast storage part 3 held therebetween in the gantry 2; and a rotation drive part which rotates the radiation generation tube 8 and the radiation detector 11 at the same angular velocity around a rotation shaft D passing inside the breast storage part 3, an annular gap 14c corresponding to a rotational transfer path of the radiation detector 11 is opened on the inner surface of the front plate 7 between the inner peripheral edge and the outer peripheral edge of the front plate 7, surrounding the periphery of the breast inlet/outlet 17, to provide a radiation shielding body 14 and an end of the radiation detector 11 on a side facing the front plate 7 is made to get into the inner side of the gap 14c.

Description

  The present invention relates to a tomography apparatus that performs computed tomography (CT imaging), and more particularly to a mammography tomography apparatus (mammo CT apparatus) used for imaging a breast.

  Conventionally, breast cancer examinations have been performed using palpation and ultrasonic diagnosis, but mammo CT apparatuses capable of performing mammography using three-dimensional (3D) images using CT imaging have been developed.

  Patent Document 1 discloses an example of a mammo CT apparatus. The mammo CT apparatus disclosed in Patent Document 1 includes a top plate with an open / closed breast entrance, a measurement device that rotates horizontally around the breast entrance / exit, an X-ray generator, and an X-ray detector. It is configured. At the time of CT imaging, the subject lies down on the top and shoots while the breast is inserted into the breast storage part from the breast entrance / exit. The X-ray generator and X-ray detector with a built-in collimator that defines the X-ray irradiation area are rotated at a predetermined angular position while rotating around the rotation axis passing through the breast housing, and viewed from each direction. An X-ray transmission image of the subject is acquired. In addition, an X-ray shield for blocking leakage of X-rays to the human body is attached to the lower surface of the top plate.

US Pat. No. 6,987,831

  In a mammo CT apparatus such as that disclosed in Patent Document 1, a breast is inserted into a breast storage unit from a breast entrance / exit while applying the subject's sternum to the upper surface of the top plate. As a result, the breast overlaps within the X-ray irradiation area irradiated to the breast storage section, so that an X-ray transmission image can be projected and photographed on the X-ray detector. In the mammo CT apparatus, it is preferable to place the X-ray detector as close to the top plate as possible so that the breast (root) on the sternum side can be imaged as much as possible.

  By the way, the X-ray detector has a detection area in the center where X-ray detection is performed by the X-ray detection element, and a non-detection area in the peripheral area where a wiring circuit and the like are laid out and an X-ray cannot be detected. In order to be able to image the base of the breast, it is necessary to bring the detection area close to the top plate, but there is a problem that it is difficult to bring the detection area and the top plate close due to the presence of the non-detection area at the peripheral edge. In order to prevent X-ray leakage to the subject side, an X-ray shield is provided inside the top plate. When the X-ray detector is brought close to the top plate, it interferes with this, so the X-ray detector cannot be brought closer than a certain level.

  Accordingly, an object of the present invention is to enable radiography of the breast root by bringing the detection area of the radiation detector closer to the subject in a mammo CT apparatus using radiation typified by X-rays. is there.

For the above-mentioned purpose, the present invention provides a gantry having a front plate having an opened breast entrance for entering and exiting a breast into a breast storage section,
A radiation generating tube provided inside the gantry and having a radiation emitting portion;
A radiation detector provided on the inner side of the gantry so as to face the radiation emitting portion with the breast accommodating portion interposed therebetween,
A rotation drive unit that rotates the radiation generating tube and the radiation detector in the same direction at the same angular velocity around a rotation axis extending in the breast entrance / exit direction through the inside of the breast housing unit; Have
A mammography apparatus that irradiates radiation from the radiation emitting unit toward the radiation detector through the breast storage unit,
Surrounding the breast entrance / exit, an annular gap corresponding to the rotational movement path of the radiation detector is opened on the inner surface of the front plate between the inner and outer peripheral edges of the front plate. The present invention provides a mammography apparatus, wherein a radiation shield is provided, and an end of the radiation detector facing the front plate enters the inside of the gap.

  In the present invention, the radiation shield is provided with an annular gap corresponding to the rotational movement path of the radiation detector, and the end on the side facing the front plate of the radiation detector is located inside the gap. I'm stuck in. In other words, since the end of the radiation detector facing the front plate enters the front plate side from the surface of the radiation shield, compared with the case where the radiation detector is provided in contact with the radiation shield. However, the radiation detector can be brought closer to the front plate by the thickness of the radiation shield at the maximum. Thereby, the detection area of the radiation detector can be brought close to the subject, and radiation imaging up to the breast root can be performed. Moreover, leakage of excess radiation to the subject can be prevented by the radiation shield.

It is a whole perspective view of a mammography apparatus (mammo CT apparatus). It is sectional drawing of the mammo CT apparatus of the 1st example of this invention, (a) is sectional drawing seen from the X direction in FIG. 1, (b) is sectional drawing seen from the Y direction in FIG. FIG. 3 is an enlarged view around the collimator from the radiation generating tube in FIG. It is a block diagram of the imaging | photography system of the mammo CT apparatus of this invention. It is sectional drawing of the mammo CT apparatus of the 2nd example of this invention, (a) is sectional drawing seen from the X direction in FIG. 1, (b) is sectional drawing seen from the Y direction in FIG. It is sectional drawing of the mammo CT apparatus of the 3rd example of this invention, (a) is sectional drawing seen from the X direction in FIG. 1, (b) is sectional drawing seen from the Y direction in FIG. It is sectional drawing of the mammo CT apparatus of the 4th example of this invention, (a) is sectional drawing seen from the X direction in FIG. 1, (b) It is sectional drawing seen from the Y direction. FIG. 6 is a cross-sectional view of a mammo CT apparatus according to a fifth example of the present invention, where (a) is a cross-sectional view seen from the X direction in FIG. 1, and (b) is a cross-sectional view seen from the Y direction in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings referred to below, the same reference numerals indicate the same components.

[First example]
<Outline of mammo CT system>
As shown in FIGS. 1 to 3, a mammographic tomography apparatus (mammo CT apparatus) 1 has a gantry 2 constituting a room in which a radiation source, a radiation detector 11 and the like are housed. In addition, the gantry 2 includes a breast housing part 3 for the subject P to insert the breast 15 at the center thereof. In addition, 4 is a support part.

  The gantry 2 includes an inner peripheral plate 5 that surrounds the breast storage unit 3, an outer peripheral plate 6 that surrounds the outer periphery, a front plate 7 that connects the inner peripheral plate 5 and the outer peripheral plate 6 on the front side, and a back side that is not shown. It is a hollow disk-shaped member which has a back plate. The front plate 7 has an annular shape in which a breast entrance / exit 17 for entering / exiting the breast 15 into / from the breast accommodating part 3 is opened at the center. Inside the gantry 2, a radiation generating tube 8 and a radiation detector 11 are supported by a rotating plate (not shown), and are rotated together by a rotation drive unit 101 (see FIG. 4) during CT imaging. It is the composition which becomes. This rotation is performed around a rotation axis D that passes through the inside of the breast storage unit 3 and extends in the direction in which the breast 15 enters and exits the breast storage unit 3 (Z direction). The radiation generating tube 8 and the radiation detector 11 are rotated in the same direction at the same angular velocity. At the time of radiography with the mammo CT apparatus 1, the subject P inserts the breast 15 from the front side 7 of the front plate 7 of the gantry 2 through the breast entrance / exit 17 into the breast housing 3 and performs CT radiography while maintaining this posture. Do. The mammo CT apparatus 1 of this example is of a type in which the front plate 7 is installed vertically and the subject P stands in front of the front plate 7 for examination. However, the mammo CT apparatus 1 according to the present invention is a type in which the front plate 7 is placed sideways and the front plate 7 is a top plate described in the background art, and the subject lies on the front plate 7 and is inspected. It can also be. In this case, the inner peripheral plate 5 can be omitted.

<Radiation tube>
As shown in FIGS. 2 and 3, the radiation generating tube 8 is a transmissive radiation generating tube, and includes an electron gun 9 that generates an electron beam and a radiation emitting unit 10. As the electron gun 9, for example, a hot filament type electron generation source can be used. The radiation emitting unit 10 includes a transmission type target in which a target layer that generates radiation by irradiating an electron beam from an electron gun 9 is laminated on a radiation transmissive support substrate. The material constituting the support substrate is preferably a material having a strength capable of supporting the target layer, a low absorption of radiation generated in the target layer, and a high thermal conductivity so that heat generated in the target layer can be quickly dissipated. For example, diamond, silicon carbide, aluminum nitride, or the like can be used. The material constituting the target layer is preferably a material having a high melting point and high radiation generation efficiency. For example, tungsten, tantalum, molybdenum and alloys thereof can be used.

  The radiation emitting unit 10 has a collimating function for defining a radiation emission region generated by the electron beam irradiation to the target as a predetermined radiation irradiation region 13. The emitted radiation is irradiated to the radiation detector 11 while being defined in a predetermined radiation irradiation region 13 by this collimating function. At this time, when the breast 15 of the subject P enters the radiation irradiation region 13, the radiation transmission image of the breast 15 reaches the radiation detector 11, and transmission images of the mammary gland and fat contained in the breast 15 are obtained. can get.

  The radiation generating tube 8 is supported by a rotating plate (not shown) that is rotated by a rotation driving unit 101 (see FIG. 4), and a rotating shaft that extends in the direction in which the breast 15 enters and exits the breast storage unit 3 by the rotation of the rotating plate. It rotates around D.

<Radiation detector>
The radiation detector 11 has a central detection area 11a where radiation can be detected and a peripheral non-detection area 11b where radiation cannot be detected. The radiation detection 11 of this example has a configuration in which a plurality of radiation detection elements are arranged in the detection area 11a, and signal wirings connected to the plurality of radiation detection elements are arranged in the non-detection area 11b. Yes. The detection area 11a in this example has a size that matches the radiation irradiation region 13 defined by the collimating function of the radiation emitting unit 10, and the planar shape of the detection area 11a in this example is a quadrangle. The radiation detection element is not particularly limited as long as it is an element that converts the intensity of incident radiation to an electric signal, but is configured by a photoelectric conversion element such as a CMOS and a phosphor. Further, the radiation detector 11 may be a digital sensor type radiation detector provided with an AD converter from the viewpoint of compatibility with the imaging system.

  The radiation detector 11 is provided at a position facing the radiation emitting portion 10 of the radiation generating tube 8 with the breast accommodating portion 3 interposed therebetween. The radiation detector 11 is supported by a rotating plate (not shown) that is rotated together with the radiation generating tube 8 by a rotation driving unit 101 (see FIG. 4). The radiation detector 11 rotates in the same direction at the same angular velocity as that of the radiation generating tube 8 around the rotation axis D extending in the direction in which the breast 15 enters and exits the breast housing 3 by the rotation of the rotating plate. .

<Radiation shield>
As shown in FIGS. 2 and 3, a double annular radiation shield 14 is provided inside the front plate 7 of the gantry 2 so as to surround the breast entrance / exit 17. The radiation shield 14 is divided into an inner peripheral radiation shield 14b on the inner peripheral side (a peripheral edge on the breast entrance / exit 17 side) and an outer peripheral radiation shield 14a on the outer peripheral side (the peripheral edge on the outer peripheral plate 6 side). It is provided with an annular gap 14c between them. The gap 14c is formed corresponding to the rotational movement path of the radiation detector 11, and the radiation detector 11 is provided at a position corresponding to the interval 14c and faces the front plate 7 of the radiation detector 11. The end on the side to be inserted enters the inside of the gap 14c. In other words, the end of the radiation detector 11 on the side facing the front plate 7 enters the front plate 7 side from the surfaces of the inner radiation shield 14b and the outer radiation shield 14a. The radiation detector 11 rotates around the rotation axis D in a state where the end on the side facing the front plate 7 enters the gap 14c.

  The radiation shield 14 constituted by the outer peripheral radiation shield 14a and the inner peripheral radiation shield 14b is generated when the radiation emission unit 10 directly irradiates the subject P with radiation or when the radiation detector 11 is irradiated with radiation. This is to prevent leakage of scattered radiation to the subject P. As the material of the radiation shield 14, heavy metals such as lead, tungsten, tantalum, and rhenium having high radiation shielding ability are suitable. The radiation shield 14 (outer peripheral radiation shield 14a and inner peripheral radiation shield 14b) is generally annular, but may be elliptical, rectangular, or the like.

  With the arrangement as in this example, when viewed from the Z direction, the end of the radiation detector 11 on the side facing the front plate 7 enters the thickness of the radiation shield 14. For this reason, the radiation detector 11 can be brought close to the front plate 7 of the gantry 2 without being obstructed by the radiation shield 14, and the detection area 11 a can be brought close to the front plate 7 to widen the root of the breast 15. CT imaging of a range becomes possible. In addition, as described above, since the end of the radiation detector 11 facing the front plate 7 overlaps with the thickness of the radiation shield 14 when viewed from the Z direction, the radiation detector 11 and the radiation shield are overlapped. Leakage of radiation from between the body 14 can also be suppressed.

<Mammo CT system imaging system>
FIG. 4 is a configuration diagram of an imaging system of the mammo CT apparatus of the present invention.

  The system control apparatus 100 controls the radiation generating apparatus 103 including the radiation generating tube 8 and its driving circuit 102, the radiation detector 11, and the rotation driving unit 101 in cooperation with each other. The drive circuit 102 outputs various control signals to the radiation generation tube 8 under the control of the radiation tube control unit 108 of the system control apparatus 100. The rotation drive control unit 107 of the system control apparatus 100 sends a drive control signal to the rotation drive unit 101 based on position information from the position detection sensor 104 for detecting the rotation position of the rotary plate that supports the radiation generating tube 8 and the like. Output. The emission state of radiation emitted from the radiation generator 103 is controlled while rotating the rotation drive unit 101 by a predetermined amount by this drive control signal. The radiation emitted from the radiation generator 103 is partially shielded by a collimator or the like, passes through the breast 15 and is detected by the radiation detector 11. The radiation detector 11 converts the detected radiation into an image signal and outputs it to the signal processing unit 105. The signal processing unit 105 performs predetermined signal processing on the image signal and sends the image signal to the image processing unit 106 under the control of the system control apparatus 100. The image processing unit 106 in the system control device 100 forms a CT image from image information captured at each rotational position, and stores this in the image storage unit 109. The display unit 111 generates a stereoscopic image by synthesizing a CT image obtained by capturing a plurality of images of the radiation generating tube 8 and the radiation detector 11 while rotating around the breast 15 by the image synthesis unit 110. An image can be displayed.

[Second example]
FIG. 5 shows a mammo CT apparatus according to the second example. In the present example, one annular radiation shield 14 is provided on the inner surface of the front plate 7 with a gap 14 c between the outer peripheral edge of the front plate 7. The radiation detector 11 is provided at a position corresponding to the gap 14c, and the end on the side facing the front plate 7 enters the inside of the gap 14c. That is, the end of the radiation detector 11 on the side facing the front plate 7 enters the front plate 7 side from the surface of the radiation shield 14. Except for these points, the second example is the same as the first example.

  With the above configuration, the radiation irradiation region 13 can be configured not to substantially cross the gap 14c, so that the radiation P can be surely leaked to the subject P more than the first example described above. Prevention can be performed.

[Third example]
As shown in FIG. 6, the radiation detector 11 of this example has a three-dimensionally curved shape. Specifically, it is convexly curved toward the rotation outer periphery side in the rotation direction around the rotation axis D shown in FIG. The rest is the same as the first example described above.

  By doing in this way, the width | variety of the clearance gap 14c opened between the outer periphery radiation shield 14a and the inner periphery radiation shield 14b can be made small, and the leakage of the radiation from this area | region can be suppressed. Since the width of the gap 14c can be minimized, it is most preferable that the center of curvature of the radiation detector 11 coincides with the rotation axis D.

[Fourth example]
As shown in FIG. 7, in this example, the radiation detector 11 in the second example described above is curved convexly toward the outer periphery of the rotation in the rotation direction around the rotation axis D. The rest is the same as the second example described above.

  In this example, the width of the gap 14c opened between the outer peripheral edge of the front plate 7 can be reduced, and radiation leakage from this region can be suppressed. Since the width of the gap 14c can be made the smallest, it is most preferable that the center of curvature of the radiation detector 11 coincides with the rotation axis D, as in the third example.

[Fifth example]
As shown in FIG. 8, the region of the gap 14c overlapping the radiation irradiation region 13 from the radiation emitting unit 10 to the breast storage unit 3 is filled, and the periphery of the rotation axis D is synchronized with the radiation detector 11 in the same direction. A rotating radiation sub-shield 16 is provided. Except this point, the second embodiment is the same as the first example.

  By doing in this way, the leakage of the radiation from especially the clearance gap 14c located between the radiation emission part 10 and the breast accommodating part 3 can be suppressed. It is effective to provide the radiation sub-shield 16 at least in the region of the gap 14c that overlaps the radiation irradiation region 13 from the radiation emitting unit 10 to the breast storage unit 3, and by providing it in a wider region, the effect of preventing radiation leakage is provided. It can also be improved.

  1: mammography apparatus (mammography CT apparatus), 2: gantry, 3: breast housing part, 4: support part, 5: inner peripheral plate, 6: outer peripheral plate, 7: front plate, 8: radiation generating tube, 9 : Electron gun, 10: radiation emitting part, 11: radiation detector, 11a: detection area, 11b: detected area, 12: collimator, 13: radiation irradiation region, 14: radiation shield, 14a: outer peripheral radiation shield, 14b: inner peripheral radiation shield, 14c: gap, 15: breast, 16: radiation auxiliary shield, 100: system controller, 101: rotation drive unit, 102: drive circuit, 103: radiation generator, 104: position detection Sensor: 105: Signal processing unit 106: Image processing unit 107: Rotation drive control unit 108: Radiation generation tube control unit 109: Image storage unit 110: Image composition unit 111: Display unit P: Test Who : Axis of rotation

Claims (7)

A gantry having a front plate with an open / closed breast entrance for entering and exiting the breast; and
A radiation generating tube provided inside the gantry and having a radiation emitting portion;
A radiation detector provided on the inner side of the gantry so as to face the radiation emitting portion with the breast accommodating portion interposed therebetween,
A rotation drive unit that rotates the radiation generating tube and the radiation detector in the same direction at the same angular velocity around a rotation axis extending in the breast entrance / exit direction through the inside of the breast housing unit; Have
A mammography apparatus that irradiates radiation from the radiation emitting unit toward the radiation detector through the breast storage unit,
Surrounding the breast entrance / exit, an annular gap corresponding to the rotational movement path of the radiation detector is opened on the inner surface of the front plate between the inner and outer peripheral edges of the front plate. A mammography apparatus, wherein a radiation shield is provided, and an end of the radiation detector on the side facing the front plate enters the inside of the gap.   The radiation detector has a central detection area where radiation can be detected and a non-detection area at a peripheral edge where radiation cannot be detected, and an end of the radiation detector which enters the inside of the gap The non-detection area is a mammography apparatus according to claim 1.   The radiation shield is divided into an inner peripheral radiation shield on the inner peripheral side of the front plate and an outer peripheral radiation shield on the outer peripheral side of the front plate, and the gap is formed between them. The mammographic tomography apparatus according to claim 1 or 2, characterized in that   Provided is a radiation sub-shield that fills at least the gap area overlapping the radiation irradiation area from the radiation emitting section to the breast housing section and rotates in the same direction around the rotation axis in synchronization with the radiation detector. The mammographic tomography apparatus according to claim 3, wherein the tomography apparatus is provided.   The mammography apparatus according to claim 1 or 2, wherein the gap is formed between an outer peripheral edge of the radiation shield and an outer peripheral edge of the front plate.   The mammography apparatus according to any one of claims 1 to 5, wherein the radiation detector is curved convexly toward the outer periphery of the rotation in a rotation direction around the rotation axis.   The mammography apparatus according to claim 6, wherein a center of curvature of the radiation detector coincides with the rotation axis.

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