JP2010051337A - Tomographic breast imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of body movement to an X-ray tomographic image without using a tool for fixing breast causing attenuation of X-ray signals or giving uncomfortable feeling to a subject in a mammo CT with little dose to sites other than breast. <P>SOLUTION: A tomographic breast imaging system has a top plate 12 having a hole 14 for passing the breast B, a body movement detecting means 191 for detecting the movement of the mammo, an X-ray generating device 20 for irradiating a corn beam of the X-ray, an X-ray detector 18 for detecting the incident intensity of the X-ray, a base 16 for mounting the X-ray generating device 20 and the X-ray detector 18 and rotating around a rotating axis A, and an image reconstructing means 125 for generating the X-ray tomographic image of the breast from the plurality of X-ray transmitting image data obtained while the base rotates, the X-ray tomographic image of the breast is corrected from the movement of the breast B detected by the body movement detecting means 191. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a breast tomographic imaging apparatus using computer tomography (CT), and more particularly to a breast tomographic imaging apparatus capable of eliminating a false image generated due to movement of a breast.

  Traditionally, breast cancer testing has been performed using palpation and ultrasound. However, these tests can be found only with cancer cells that have grown to some extent. For this reason, mammography using an X-ray transmission image that can relatively easily find calcification occurring in early breast cancer has come to be used in combination. However, mammography requires uniform breast thickness in order to obtain good image quality, so the X-ray transmission image is obtained by flattening the breast with a compression plate, which may cause pain to the subject. There is. In addition, since the obtained image is a simple X-ray transmission image, when the target tumor part or calcification part overlaps with an object that forms an X-ray image such as a mammary gland on the image, the lesion is determined. Hard to break.

  Therefore, a breast tomographic imaging apparatus (mammo CT) using computer tomography (CT) capable of obtaining a 3D image without compressing the breast has been developed. With mammo CT, small calcification can be detected without causing pain to the subject. Moreover, it can be accurately evaluated even when the X-ray opaque parts overlap, and is effective for early detection of breast cancer.

Patent Document 1 discloses an example of mammo CT.
The mammo CT disclosed in Patent Document 1 controls a bed having a hole in the breast position, a gantry that rotates horizontally around the hole, a motor that moves the bed and the gantry, and a switch that operates a measurement device. Device. The measurement apparatus includes an X-ray generation apparatus, an X-ray detection apparatus disposed opposite to the X-ray generation apparatus, and an arithmetic unit that reconstructs a tomographic image from an X-ray transmission image obtained by the X-ray detection apparatus. The X-ray generation device and the X-ray detection device are mounted on a gantry and acquire an X-ray transmission image of the breast from each direction while rotating around the breast together.

  The X-ray generator emits X-rays according to the drive switch. The X-ray becomes a cone-shaped cone beam, passes through the subject, and enters the X-ray detection apparatus. The X-ray detection apparatus is a flat panel detector (FPD) in which X-ray detection elements are arranged in a matrix on a plane. Each X-ray detection element accumulates the X-ray projected from the X-ray generator as a measurement signal corresponding to the remaining X-ray intensity absorbed by the substance in the optical path, and the FPD forms an X-ray transmission image at that time Will do. The X-ray detection apparatus can transmit an X-ray transmission image by scanning the measurement signal of each detection element and sequentially outputting it.

When the subject lies on his / her bed and puts the breast to be measured into the hole, the breast hangs down between the X-ray generator and the X-ray detector. The subject presses the chest against the hole so that the breast is exposed to the measurement area as close to the chest wall.
The cone beam X-ray generator and the FPD operate around the breast as the subject, operate the X-ray generator for each predetermined angle, take an X-ray transmission image with the X-ray detector, and perform a reconstruction calculation device. The image signal is transmitted to. The reconstruction calculation device reconstructs the collected X-ray transmission images of one crew into 3D, and creates an X-ray tomographic image of the breast.

  In the X-ray tomographic image thus obtained, the calcified portion has an image generating power equivalent to that of bone, so that relatively small calcification can be easily visualized and early breast cancer can be found with a high probability. In addition, since the image is a three-dimensional image, it is possible to reliably detect a lesion part on the back side of a tissue such as a mammary gland. Therefore, early diagnosis of breast cancer can be accurately performed by using palpation or ultrasonic examination together with mammo CT.

  However, for example, the mammo CT currently in clinical trials generates X-ray tomographic images using 300 X-ray transmission images acquired over 10 seconds. Therefore, during the acquisition of an X-ray transmission image of one crew, body movement accompanying breathing and pulsation changes the position of the breast, and the coordinates of the X-ray transmission image with respect to the breast are distorted. The X-ray tomographic image includes a false image, making accurate diagnosis difficult. Although breathing can be controlled by the subject, the heartbeat cannot be intentionally stopped, so the occurrence of false images is inevitable.

In Patent Document 2, when both the breast and the heart are imaged using an X-ray CT apparatus, a false image is generated in the reconstructed image due to the influence of the heart beat, whereas the breast is pushed upward and fixed. It is disclosed that the generation of false images is suppressed by using a breast fixing jig that prevents the heart from being included in the scan range. However, when trying to diagnose breast cancer with the disclosed apparatus, there is a problem of X-ray exposure to parts other than the breast, and there is a problem that the X-ray transmission image of the breast is distorted due to X-ray absorption in the breast fixing jig.
US Pat. No. 6,480,565 JP 2005-204859 A

  Accordingly, an object of the present invention is not to use a breast fixing jig that causes attenuation of the X-ray signal or makes the subject feel uncomfortable in a CT apparatus dedicated to a mammon with less X-ray exposure to parts other than the breast. Thus, a breast tomographic imaging apparatus (mammo CT) that reduces the influence of body motion is provided.

  In order to solve the above problems, a tomographic image radiographing apparatus according to the present invention includes a top plate that has a hole through which a breast passes and a subject lies on his / her face down and hangs the breast from the hole, and a body that detects breast movement A two-dimensional detector in which a plurality of X-ray detectors that detect motion detection means, an X-ray generator that emits an X-ray cone beam, and an incident intensity of X-rays emitted from the X-ray generator are arranged on the surface An X-ray detector comprising: an X-ray generator and an X-ray detector mounted at opposing positions, a frame that rotates around a rotation axis that passes through a hole through which the breast passes, and X-ray detection while the frame rotates X-ray tomography of a breast based on the movement of the breast detected by the body motion detector, and a reconstruction calculation device for generating a X-ray tomogram of the breast from a plurality of X-ray transmission image data acquired and output by the instrument It is characterized by correcting an image.

  According to the breast tomography apparatus according to the present invention, the motion of the breast hanging from the hole is detected by the body motion detection means, and the X-ray tomographic image of the breast is corrected based on the detected data. It is possible to obtain an accurate X-ray tomographic image without a false image that can be obtained when the breast moves due to the influence of heartbeat or heartbeat.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a conceptual configuration diagram conceptually showing an image acquisition unit of a breast tomographic imaging apparatus according to an embodiment of the present invention, and FIG. 2 is a system block diagram for explaining the overall configuration of the breast tomographic imaging apparatus. FIG. 3 is a drawing for explaining the arrangement of the body motion detecting means, and FIGS. 4 and 5 are conceptual diagrams of images acquired by the body motion detecting means.

As shown in FIG. 1, the breast tomography apparatus 200 according to the present embodiment includes a hole 14 through which the breast passes, and the subject P can lie down on his / her face and suspend the breast B from the hole 14. And an X-ray generator 20 that emits a radial X-ray cone beam C and a plurality of X-ray detection elements that detect the incident intensity of X-rays emitted from the X-ray generator 20 and transmitted through the object are arranged on the surface. An X-ray detector 18 having a flat panel display (FPD), and a gantry 16 mounted so that the X-ray generator 20 and the X-ray detector 18 face each other across the rotation axis A are provided. The rotation axis A is arranged to pass through the hole 14 through which the breast passes. The gantry 16 rotates around the rotation axis A.
The breast tomography apparatus 200 further includes a control device, an image processing device, and an image display device that control the movement of the top 12 and the gantry 16 and the operation of the X-ray generator 20 and the X-ray detector 18.

Referring to FIG. 2, the breast tomographic imaging apparatus 200 includes an image generation unit 110, an image processing unit 120, an image storage unit 130, an image display unit 140, an imaging unit 160, a top plate unit 170, and body motion detection means 191. Is done.
Specifically, the image generation unit 110 includes an X-ray generation unit 113 corresponding to the X-ray generation apparatus 20 and an X-ray detection unit 115 corresponding to the X-ray detector 18. When the trigger signal is received from the imaging unit 111, The X-ray generation unit 113 emits the cone beam C, and the X-ray detection unit 115 detects the cone beam C transmitted through the subject, generates an image signal, and transmits the image signal to the image processing unit 120.

The image processing unit 120 includes an image processing unit 121, an image correction unit 123, an image reconstruction unit 125, a confirmation image generation unit 127, and an adjustment value calculation unit 129.
The image processing unit 121 generates an image signal of an X-ray transmission image detected by the X-ray detection unit 115 based on the detection signal input from the image generation unit 110. The generated image signal is transmitted to the image correction unit 123 and also transmitted to the image storage unit 130 and the image display unit 140, and can be referred to as acquired image information.

The image correcting unit 123 corrects the obtained image signal of the X-ray transmission image by removing noise and reducing artifacts and transmits the image signal to the image reconstruction unit 125 and the confirmation image generating unit 127.
When the X-ray transmission image signals from each direction acquired for the subject are collected, the image reconstruction unit 125 performs an reconstruction operation to generate an image signal that forms a CT screen of the subject, and the image storage unit 130. And transmitted to the image display unit 140.

  In the present embodiment, body movement detection means 191 is provided. As will be described in detail later, the body motion detecting means 191 detects the movement of the breast B that is suspended from the hole 14 through which the subject lies on the top and passes the breast. The movement of the breast B can be directly measured, or indirectly estimated from the respiratory state and the heartbeat. In the image reconstruction unit 125, for each X-ray transmission image, the image shift in the horizontal and vertical images of the breast B measured by the body motion detection unit 191 is input and reflected in the reconstruction calculation. An X-ray tomographic image replaced with a state in which does not change is generated. It should be noted that the X-ray tomographic image obtained by performing reconstruction operation on the collected X-ray transmission image signal is also corrected by the method of correcting the image based on the movement of the breast, and the position of the image of the X-ray transmission image is corrected. Then, it is possible to obtain an X-ray tomographic image without a false image also by a method of performing reconstruction calculation.

The confirmation image generation unit 127 generates a confirmation image used for adjustment of the apparatus 200 and sends it to the adjustment value calculation unit 129. An image that shows the positional relationship between the screen and the subject is generated and related to the adjustment values of the device, such as whether the alignment is correct, whether it has the correct resolution, and does not include extra noise. Confirm.
The adjustment value calculation unit 129 calculates an adjustment value necessary for eliminating the deviation from the expected value for the position of the screen frame, the signal intensity, and other environmental values, and the photographing unit control unit 161 and the top panel unit control unit. 171.
The adjustment value can also be designated directly by the operator via the adjustment value input means 151. The adjustment value input unit 151 includes a data input device using a keyboard, a touch panel, or a mouse.

The image storage unit 130 is provided with an image storage unit 131 formed by an image memory or the like, and can be easily read out and used when image information is required, such as recalculation or redisplay.
The image display unit 140 is provided with an image display unit 141 and a confirmation image display unit 143. The image display unit 141 displays a cross-sectional image or a stereoscopic image of a breast for confirming whether a tumor, calcification, cancer tissue, or the like is present in the breast as an image used for breast cancer diagnosis. The confirmation image display unit 143 displays an image that can be used to monitor or adjust the abnormality or malfunction of the breast tomography apparatus 200. In particular, when the operator performs the adjustment, the adjustment can be performed while observing the image displayed by the confirmation image display unit 143. Since only the positional relationship needs to be known for adjustment of the apparatus, an X-ray image obtained by using X-rays with weak radiant energy can be used to avoid X-ray exposure.

  The imaging unit 160 includes an imaging unit rotation unit 163 controlled by the imaging unit control unit 161, an imaging unit lifting / lowering unit 165, an X-ray detection unit translation unit 167, and an X-ray generation unit translation unit 169. The imaging unit rotating unit 163 and the imaging unit lifting / lowering unit 165 adjust the rotation and height of the gantry 16 on which the image generation unit 110 composed of the X-ray generation unit 113 and the X-ray detection unit 115 is mounted to the next determined position. When the X-ray transmission image is acquired by driving the image generation unit 110 to a predetermined position, the imaging unit 111 supplies a trigger signal to the imaging unit control unit 161 and drives the imaging unit rotation unit 163 again to move to the next position. Move to. Further, by using the X-ray detection unit translation unit 167 and the X-ray generation unit translation unit 169, the detection sensitivity is adjusted by adjusting the distance from the X-ray detection unit 115 to the X-ray generation unit 113 or the subject B, that is, the rotation axis A. Can also be adjusted.

  The top plate portion 170 includes a top plate translation means 173 and a top plate lift means 175 controlled by the top plate control means 171. The position of the cone beam C irradiating the subject B can be easily adjusted by raising and lowering the gantry 16, but since it is in a relative relationship, the height can be adjusted by raising and lowering the top 12 as well. Is possible. Further, when making a diagnosis by switching the left and right breasts, it is necessary to realign the rotation axis A of the gantry 16 and the position of the breast B. In particular, when the top plate 12 has two holes that are aligned with the left and right breasts, the other hole is translated to the position of the rotation axis A for alignment.

  The body movement detecting means 191 may detect the movement of the breast B using a CCD camera or a video camera as exemplified in FIGS. As shown in FIG. 4, the first CCD camera 35 keeps the breast B in the field of view from the horizontal direction, and in accordance with a command from the imaging means 111, the X-ray transmission image by the X-ray generator 20 and the X-ray detector 18 is displayed. In conjunction with imaging, the vertical movement of the breast B is detected. The amount of displacement δ in the vertical direction can be obtained by converting the deviation from the reference line in the image into the actual distance or the distance on the X-ray transmission image using, for example, the tip of the nipple as a target site. Further, as shown in FIG. 5, the second CCD camera 37 images the breast B from below and measures the horizontal movement from the origin O set for an arbitrary reference point A on the breast B. This can also be obtained by expressing the deviation from the reference coordinate in an orthogonal coordinate system or a spherical coordinate system and converting it to an actual distance or a distance on an X-ray transmission image. These CCD cameras 35 and 37 are provided outside the gantry 16 so as not to obstruct X-ray irradiation or gantry rotation.

This body motion detection method has an advantage that the X-ray transmission signal is not attenuated because the breast B is directly imaged without contact.
The displacement amount information of the breast B obtained in this way is sent to the image processing unit 120 as information attached to the X-ray transmission image captured at the same time. The image reconstruction unit 125 corrects the positional relationship of the breast B in the X-ray transmission image using this displacement amount information, and reconstructs it to generate an X-ray tomographic image that does not generate a false image.

  As a method for reducing the false image of the X-ray tomographic image based on the deformation or movement amount of the breast B detected or estimated by the body motion detection means 191, as described above, the captured X-ray transmission image is used as the movement amount. In addition to a method of reconstructing an X-ray tomographic image by accumulating X-ray transmission images after shifting by a corresponding amount, the movement of the breast B is predicted based on the detected body movement, and the breast B is at the same position. A synchronous imaging method that obtains an X-ray transmission image by operating the X-ray generator 20 for the coming time can also be used.

  In the synchronous imaging method, since it is only necessary to capture when the position of the breast B is almost the same, it is not necessary to accurately measure the amount of movement of the breast B, and the synchronization position is predicted by detecting the phase of movement. do it. For example, in the case of a sinusoidal motion, an X-ray transmission image is acquired in anticipation of a time coming to an area close to zero phase (0 degrees and 180 degrees). Alternatively, the vicinity of the phase 90 degrees or −90 degrees at which the movement of the breast B becomes slow can be used. In the X-ray transmission image obtained in this way, the breast B is always imaged at the same position. Therefore, an X-ray tomographic image with few false images can be obtained by reconstruction. However, since the period suitable for imaging is short and the period only travels periodically, there is an inconvenience that it takes time to capture one crew X-ray transmission image necessary for X-ray tomographic image generation.

  Further, based on the detected or predicted body movement, the imaging system is moved by moving the gantry 16 up and down, or the top 12 is translated or moved up and down so that the imaging system and the breast B always have the same relative positional relationship. It is also possible to reduce false images of X-ray tomographic images by using a method for acquiring an X-ray transmission image in such a manner as to be maintained. The X-ray transmission image obtained by this method does not need to wait for imaging timing, and since the breast B is in the same position at any time, an X-ray tomographic image with few false images can be obtained. However, since the top 12 and the gantry 16 are moved following the heartbeat and respiration, there is a problem that a driving device having a strong and responsive response is required even if the amount of movement is small.

6 to 11 are conceptual diagrams for explaining various modes of the body motion detecting means.
Instead of setting a reference point on the breast, as shown in FIG. 6, a string 39 with a marker M attached to the tip may be hung from the breast B and the movement of the marker M moving with the breast B may be observed. . In this method, since any material can be selected for the marker M, it is possible to easily perform highly sensitive displacement measurement using an appropriate material suitable for a CCD camera or other imaging device. In addition, since the position of the camera is determined by the position of the marker M, the X-ray generator and the X-ray detector are prevented from entering the field of view of the camera, and the camera is not exposed to X-rays to cause problems. can do.
Further, as shown in FIG. 7, some markers M are pasted or applied to the breast B, and the marker M is observed with a video camera, thereby detecting a fine movement on the surface of the breast B as a displacement distribution. There is also a method. The marker M is formed of a material having a low X-ray transmittance.

FIG. 8 is a conceptual diagram showing that the laser distance meter 41 is installed below the suspended breast B, the distance L to the breast B is measured, and the vertical movement of the breast B is detected. In addition to the laser distance meter, a non-contact distance meter such as an ultrasonic distance meter can be used for this application.
FIG. 9 is a conceptual diagram for explaining a body motion detection unit configured by surrounding the breast B with a soft material 43 and providing an ultrasonic probe 45 in the soft material 43. The ultrasonic probe 45 detects the ultrasonic wave reflected at the boundary between the soft material 43 and the breast B, and based on this, the distance to the surface of the breast B is measured, and the vertical movement of the breast B can be detected therefrom. . An example of the soft material 43 is a liquid phase fluid filled in a bag. Further, as shown in the figure, the container 47 is applied to the breast B from below, the container B is filled with a liquid, the breast B is immersed in the liquid, and the contour of the breast B is prepared by the ultrasonic probe 45 charged at the bottom of the container. Even if the method of measuring the distance to is used, the movement of the breast B can be captured.

FIG. 10 is a use state diagram for explaining the case where the movement of the chest is measured from the ventral side with the ultrasonic probe. An ultrasonic probe 49 is incorporated in a portion corresponding to the abdomen of the subject P who has become prone to the top 12, and when the subject P prone on the top 12, the ventral side of the subject P The motion of the chest due to breathing and pulse is detected, and the motion of the breast B is estimated.
FIG. 11 is a use state diagram showing a case where the ultrasound probe 49 is applied to the back of the subject P and the movement of the chest is detected from the back. The ultrasonic probe 49 is pressed against the back of the subject P who is prone by the belt 51 whose end is fixed to the top plate 12.

  Using the measurement result of the motion phase of the breast B, the X-ray transmission image is obtained in the state where the breast should be by automatically adjusting the automatic device by the vertical movement of the top 12, the vertical movement of the imaging system, or X-ray synchronous irradiation. In the case of repairing an X-ray tomographic image by obtaining an image, it is preferable to perform CT imaging while monitoring after detecting and accumulating a period of several breaths in advance. In the case where correction is performed by obtaining an X-ray tomographic image after correcting the position of the captured X-ray transmission image, the prior data accumulation may be omitted.

  The present invention provides a breast tomographic imaging apparatus that compensates for movements of the breast due to breathing and heartbeats and has few false images without exposing the breast to X-ray exposure and without causing pain by compressing or sucking the breast. We were able to.

It is a conceptual block diagram shown about the image acquisition part of the breast tomography apparatus which concerns on one Embodiment of this invention. It is a system block diagram explaining the whole structure of the breast tomography apparatus concerning this embodiment. It is drawing explaining arrangement | positioning of the body movement detection means in this embodiment. It is a conceptual diagram of the image acquired by the 1st body movement detection means of this embodiment. It is a conceptual diagram of the image acquired by the 2nd body movement detection means of this embodiment. It is drawing explaining the aspect of the 2nd body movement detection means in this embodiment. It is drawing explaining the aspect of the 3rd body movement detection means in this embodiment. It is drawing explaining the aspect of the 4th body movement detection means in this embodiment. It is drawing explaining the aspect of the 5th body movement detection means in this embodiment. It is drawing explaining the aspect of the 6th body movement detection means in this embodiment. It is drawing explaining the aspect of the 7th body movement detection means in this embodiment.

Explanation of symbols

12 Top plate 14 Hole through which breast passes 15 Breast container 16 Base 18 X-ray detector 20 X-ray generator 22 Negative pressure controller 35 Breast motion detector (first CCD camera)
37 Breast motion detector (second CCD camera)
39 String 41 Laser distance meter 43 Soft material 45 Ultrasonic probe 47 Container 49 Ultrasonic probe 51 Belt 110 Image generation unit 111 Imaging unit 113 X-ray generation unit 115 X-ray detection unit 120 Image processing unit 121 Image processing unit 123 Image correction unit 123 125 Image reconstruction unit 127 Confirmation image generation unit 129 Adjustment value calculation unit 130 Image storage unit 131 Image storage unit 140 Image display unit 141 Image display unit 143 Confirmation image display unit 151 Adjustment value input unit 160 Imaging unit 161 Imaging unit control unit 163 Imaging unit rotating means 165 Imaging unit lifting / lowering means 167 X-ray detection unit translation unit 169 X-ray generation unit translation unit 170 Top plate unit 171 Top panel control unit 170 Top panel unit 171 Top panel control unit 173 Top panel translation unit 175 Top Plate lifting / lowering means 191 Body motion detecting means 2 0 breast tomographic imaging apparatus

Claims (11)

A top plate with a hole through which the breast passes and the subject prone to hang down from the hole;
Body movement detecting means for detecting movement of the breast;
An X-ray generator that emits an X-ray cone beam;
An X-ray detector comprising a two-dimensional detector in which a plurality of X-ray detection elements for detecting the incident intensity of X-rays emitted from the X-ray generator are arranged on the surface;
A gantry that mounts the X-ray generator and the X-ray detector at opposing positions and rotates around a rotation axis that passes through the hole;
A reconstruction calculation device that generates an X-ray tomographic image of a breast from a plurality of X-ray transmission image data acquired and output by the X-ray detector while the gantry rotates,
A breast tomographic imaging apparatus that corrects an X-ray tomographic image of the breast based on breast movement detected by the body motion detector.   The breast tomography apparatus according to claim 1, wherein the body motion detector detects a movement of a breast hanging from the hole in a non-contact manner.   The breast tomographic imaging apparatus according to claim 2, wherein the body motion detector is one of an imaging apparatus, an ultrasonic distance meter, and a laser distance meter.   The breast tomographic imaging apparatus according to claim 1, wherein the body motion detector detects a movement of a breast drooping from the hole by an ultrasonic probe.   The breast tomography apparatus according to claim 1, wherein the body motion detector detects a motion of the subject due to pulsation or respiration by an ultrasonic probe disposed on the top board.   The correction of the X-ray tomographic image of the breast is to erase a false image of the X-ray tomographic image obtained by the reconstruction calculation device based on a detection output of the body motion detector. The breast tomography apparatus as described in any one of Claims.   The correction of the X-ray tomographic image of the breast is performed by correcting the position of the image of the X-ray transmission image obtained by the X-ray detector based on the detection output of the body motion detector. The breast tomographic imaging apparatus according to any one of claims 1 to 5, which eliminates a false image.   The correction of the X-ray tomographic image of the breast is performed by operating the X-ray generation device and acquiring an X-ray transmission image during a period in which the positional deviation of the breast is small based on the detection output of the body motion detector. The breast tomographic imaging apparatus according to any one of claims 1 to 5, which eliminates a false image of the X-ray tomographic image.   The breast tomography apparatus according to claim 1, wherein the body motion detector detects a phase of movement due to pulsation or respiration of the subject.   The breast tomography apparatus according to claim 9, wherein the body motion detector is an ultrasonic detector built in the top board, and detects movement of the chest against the abdomen of the subject.   The said body motion detector is an ultrasonic detector applied to the back of the subject lying on the top board, and detects movement of the chest by applying to the back of the subject. Breast tomographic imaging device.

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