JP5174080B2 - Breast imaging device - Google Patents

Description

  The present invention relates to a breast image photographing apparatus for photographing a breast image.

  Breast cancer screening has traditionally increased the detection rate of early cancer by combining mammography taken with a dedicated X-ray machine (hereinafter referred to as “breast imaging device”), rather than screening only by visual inspection. Medical examination using the device is performed.

  In general breast cancer screening, there are one-way imaging (two imaging) and two-direction imaging (four imaging), but in one-way imaging, only MLO imaging (inside / outside oblique direction imaging) is performed. In MLO imaging, as shown in FIG. 14 (a), imaging is performed with the breast sandwiched obliquely from the side so that the pectoralis major muscle is reflected. The mammography apparatus is provided on the arm so that the radiation irradiation unit and the imaging table face each other so that imaging can be performed from such a direction, and the imaging table can be tilted by rotating the arm. It is configured. In two-way shooting, MLO shooting and CC shooting (head-to-tail shooting) are performed. In CC imaging, imaging is performed with the breast sandwiched from above as shown in FIG. The MLO imaging method is the imaging method that can make the whole breast image the widest, but the CC imaging method is performed to complement the MLO imaging, and the MLO imaging makes the inside of the breast difficult to image in the image Can do. Normally, one-way imaging and two-way imaging are performed for the left and right breasts, respectively, so that two-time imaging is performed in one-way imaging and four-time imaging is performed in two-way imaging.

  The breast is made of mammary tissue, adipose tissue, and skin, but in order to take a mammogram necessary for correct diagnosis, it is necessary to press the breast to the same thickness as much as possible and copy the fine mammary gland and adipose tissue onto a film. For this reason, in the breast image photographing apparatus, the breast is photographed between the photographing table and the compression plate. However, if the compression pressure is too low, the breasts, fats, blood vessels, etc. may overlap, and even if there is a tumor, the image may not be displayed. The compression pressure must be adjusted so that the thickness is suitable for imaging according to each breast.

  Furthermore, AEC (Automatic Exposure Control) for measuring the dose of radiation that has passed through the breast is indispensable for obtaining a stable and appropriate film density in a mammography apparatus. AEC is a sensor installed in the lower part of the cassette. Generally, a semiconductor detector is arranged as a sensor, so that the operator can measure the radiation dose irradiated to the center of the breast at the time of imaging. The photo is taken by adjusting the breast position of the person.

  Therefore, when performing bi-directional imaging of the left and right breasts, it is necessary to perform these adjustments four times, which places a considerable burden on the subject.

  Therefore, for mammography examination in which repeated imaging is performed, values such as compression pressure adjusted for each subject for the first time are stored, and from the next time, breast imaging is performed using the stored values. It has been proposed (Patent Document 1).

  In addition, in order to obtain an image with the optimum density, it is necessary to take an image with the center of the breast placed on the center of the imaging table with the AEC so that the amount of X-ray transmission at the center of the breast can be detected. Since there is a large individual difference in the size of the breast, so that the breast can be photographed with the breast placed on the center of the imaging table, a large size imaging table is used and a small breast is imaged. A small-sized photographic stand is used.

Special table 2003-520115 gazette

  However, even if the pressure on the subject can be reduced by storing compression pressure or the like in advance as in Patent Document 1, it is difficult to always keep the breast at the center of the imaging table. The concentration may not be appropriate.

  In addition, there is a large individual difference in the size of the breast, and if a small breast is photographed on a large photographing stand, the position of the breast is shifted from the center, so it is possible to prepare a photographing stand of a different size depending on the size of the breast. Although it is desirable, since a photographing stand incorporating a flat panel detector is expensive, it is difficult to always prepare a large photographing stand and a small photographing stand.

  For this reason, when a small breast is imaged on a large imaging stand, the dose detected by the AEC sensor is not necessarily the dose that transmitted radiation through the vicinity of the center of the breast, and an image cannot be captured at an optimum density.

  In addition, with a large-sized compression plate, there is a problem that it is difficult for the operator to remove the hand after positioning in the case of a small breast.

  Therefore, an object of the present invention is to provide a mammography apparatus that can automatically acquire a breast image with an optimal density while reducing the burden on the subject.

A first breast imaging apparatus of the present invention includes a radiation irradiation unit that irradiates a subject's breast with radiation,
An image recording medium that records image information corresponding to a dose that has been irradiated with the radiation and transmitted through the breast, and a dose detector that detects a dose at which the radiation irradiated by the radiation irradiation unit has transmitted through the breast A shooting stand,
An arm that connects the radiation irradiation unit and the imaging table to face each other;
A compression plate that compresses the breast on the imaging table provided between the radiation irradiation unit and the imaging table;
In a breast imaging apparatus comprising arm rotating means for rotating the arm according to a direction in which the breast is imaged,
Breast size detection means for detecting the breast size of the subject;
Depending on the size of the detected breast and the direction in which the arm moving means rotates the arm, the dose detection position by the dose detector is the side of the imaging table that faces the chest wall of the subject. And a dose detection position changing means for changing along the line.

  The “image recording medium” refers to a medium that records an image of a subject through which radiation has passed, and specifically includes a flat panel detector, an imaging plate, and an X-ray film. Flat panel detectors include solid state detectors and TFTs (thin film transistors).

  The “side facing the chest wall” means the side of the imaging table that faces the chest wall when taking a breast image, and the “change the position along the side facing the chest wall” is parallel to that side. This includes not only changing the position but also changing the position so as to include a component parallel to the side.

  Further, the compression position of the compression plate is set on the side of the imaging table that faces the chest wall of the subject according to the size of the detected breast and the rotation direction in which the arm moving means rotates the arm. It may be provided with a compression plate compression position moving means that moves along.

Further, when the first breast image capturing apparatus is provided with a compression plate size detection means for detecting the size of the compression plate,
The breast size detecting means may detect a breast size corresponding to the detected size of the compression plate as the breast size of the subject.

  The dose detection position changing means may include first switching means for switching whether or not to change the dose detection position by the dose detector according to the detected size of the compression plate. .

A second breast imaging apparatus of the present invention includes a radiation irradiation unit that irradiates a subject's breast with radiation,
A recording medium holding unit that holds an image recording medium that records image information corresponding to a dose that has been irradiated by the radiation and transmitted through the breast, and a dose that the radiation irradiated by the radiation irradiation unit has transmitted through the breast An imaging table having a dose detector to perform,
An arm that connects the radiation irradiation unit and the imaging table to face each other;
A compression plate that compresses the breast on the imaging table provided between the radiation irradiation unit and the imaging table;
In a breast imaging apparatus comprising arm rotating means for rotating the arm according to a direction in which the breast is imaged,
Breast size detection means for detecting the size of the breast on the imaging table;
According to the detected breast size and the rotation angle by which the arm moving means rotates the arm, the compression position of the compression plate is along the side of the imaging table that faces the chest wall of the subject. And a pressing plate pressing position moving means for moving the pressing plate.

In addition, the second breast imaging apparatus includes a compression plate size detection means for detecting the size of the compression plate,
The breast size detecting means may detect a breast size corresponding to the detected size of the compression plate as the breast size of the subject.

  The compression plate compression position moving means may include second switching means for switching whether to move the compression position of the compression plate according to the detected compression plate size.

  The breast size detecting means may detect the breast size of the subject from image information recorded on the image recording medium.

A third mammography apparatus of the present invention includes a radiation irradiation unit that irradiates a subject's breast with radiation,
An imaging table on which the breast is placed;
Breast position detection means for detecting the position of the breast on the imaging table along the side of the imaging table that faces the chest wall of the subject;
Based on the position of the breast detected by the breast position detecting means, the dose at which the radiation irradiated by the radiation irradiation unit reaches the imaging table on the line connecting the radiation irradiation unit and the region of interest of the breast is measured. And a radiation dose measuring means.

  The “region of interest” refers to a central region (part) to which radiation is applied when a breast image is taken. When imaging a breast, it is desirable to irradiate radiation around a thick part of the breast. For example, the central part of the breast is a region of interest (region of interest).

The radiation dose measuring means
A plurality of dose detectors provided along a side of the imaging table facing the chest wall;
Of the plurality of dose detectors, a dose detection position selection unit that selects a dose detector on a straight line connecting the radiation irradiation unit and the region of interest of the breast may be used.

The radiation dose measuring means
A dose detector movably provided along a side of the imaging table facing the chest wall;
It may comprise a dose detection position changing means for changing the dose detection position by moving the dose detector on a straight line connecting the radiation irradiation unit and the region of interest of the breast.

The third breast image capturing device includes an arm that connects the radiation irradiation unit and the imaging table so as to face each other, an arm rotating unit that rotates the arm according to a direction in which the breast is imaged, and the imaging If it further comprises breast size detection means for detecting the size of the breast on the table,
The breast position detecting means is
The position of the breast on the imaging table may be detected from the rotation angle obtained by rotating the arm by the arm rotating means and the size of the breast.

The third breast image photographing device further includes photographing table height adjusting means for adjusting the height of the photographing table,
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the height adjusted by the imaging table height adjusting means.

The third breast imaging apparatus is a compression plate that compresses the breast on the imaging table provided between the radiation irradiation unit and the imaging table;
A compression plate inclination detecting means for detecting an angle at which the compression plate is inclined with respect to the imaging table when the breast is sandwiched between the compression plate and the imaging table is further provided. If
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the angle at which the compression plate is inclined.

If the third breast imaging apparatus is provided with an irradiation field stop detection means for detecting a position where an irradiation field stop is attached to the radiation irradiation unit,
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the position of the irradiation field stop.

A fourth mammography apparatus of the present invention includes a radiation irradiation unit that irradiates a subject's breast with radiation,
An imaging table on which the breast is placed;
An arm that connects the radiation irradiation unit and the imaging table to face each other;
A compression plate that compresses the breast on the imaging table provided between the radiation irradiation unit and the imaging table;
Breast position detection means for detecting the position of the breast on the imaging table along the side of the imaging table that faces the chest wall of the subject;
Compression plate compression position moving means for moving the position where the compression plate compresses the breast along the side facing the chest wall of the subject based on the breast position detected by the breast position detection means. It is characterized by that.

The fourth breast image capturing apparatus further includes arm rotating means for rotating the arm according to the direction in which the breast is imaged, and breast size detecting means for detecting the size of the breast on the imaging table. If,
The breast position detecting means is
The position of the breast on the imaging table may be detected from the rotation angle obtained by rotating the arm by the arm rotating means and the size of the breast.

If the fourth breast image photographing device further includes photographing table height adjusting means for adjusting the height of the photographing table,
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the height adjusted by the imaging table height adjusting means.

When the fourth breast image capturing apparatus compresses the breast between the compression plate and the imaging table, the compression plate detects an angle at which the compression plate is inclined with respect to the imaging table. If it further comprises an inclination detection means,
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the angle at which the compression plate is inclined.

If the fourth breast imaging apparatus includes an irradiation field stop detection unit that detects a position where an irradiation field stop is attached to the radiation irradiation unit,
The breast position detecting means is
The position of the breast on the imaging table may be estimated according to the position of the irradiation field stop.

  According to the present invention, by moving the detection position of the dose detector so as to come to the center of the breast according to the size of the breast, a breast image is captured at an appropriate density and the subject is irradiated. It is possible to reduce the radiation dose.

  Also, by detecting the size of the compression plate, it becomes possible to easily detect the size of the breast.

  Further, by detecting the breast size from the image information, the center of the breast can be detected accurately, and the dose can be detected at a more appropriate position.

  Furthermore, by moving the position of the compression plate according to the size of the breast and compressing the breast at an appropriate position, it is possible to compress the breast uniformly and to take a breast image suitable for diagnosis. Become.

  Further, by estimating the position of the breast on the imaging table from the height of the imaging table, the position of the breast can be estimated without changing the configuration of the mammography apparatus.

  Moreover, the position of the breast in the compressed state can be estimated by estimating the position of the breast on the imaging table from the angle at which the compression plate is inclined.

  Furthermore, by estimating the position of the breast on the imaging table in accordance with the irradiation field stop mounting position, the position of the breast can be easily estimated with the imaging center as the center of the breast.

Schematic diagram of a first embodiment of a breast imaging device Front view of arm part of breast imaging device Diagram showing the relationship between the compression plate, the solid state detector in the imaging table, and the dose detector (Part 1) Schematic view of the inside of the imaging table of the breast imaging system Schematic diagram of solid state detector The figure which showed the connection aspect of a solid state detector and an electric current detection means Block diagram showing details of current detection means and high voltage power supply unit and connection mode between them and solid state detector A diagram showing the state of the dose detector moved to the center of the breast Schematic of imaging stand with multiple dose detectors Diagram showing the relationship between the compression plate, the solid state detector in the imaging table, and the dose detector (Part 2) Schematic diagram of a second embodiment of a breast imaging apparatus The figure showing the appearance of moving the position of the compression plate and dose detector to the center of the breast A diagram showing how the compression plate and the dose detector are moved with different amounts of movement Illustration for explaining MLO shooting and CC shooting A CCD camera installed near the radiation irradiation unit Figure with a strain gauge on the photographic stand Diagram showing the relationship between the height of the imaging platform and the position of the breast A diagram showing the relationship between the inclination of the compression plate and the position of the breast Diagram showing the relationship between the irradiation field stop and breast position Picture of an imaging stand with multiple dose detectors in the direction away from the chest wall Diagram showing the area for detecting the dose of flat panel detectors

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of a breast imaging apparatus according to the present invention, and FIG. 2 is a front view of an arm portion of the breast imaging apparatus according to the present invention.

  In this breast imaging apparatus 1, a radiation irradiation unit 3 that houses a radiation source 2 is opposed to an imaging table 4 that houses an image recording medium such as a flat panel detector 10 in a recording medium holding unit such as a cassette. The arm 5 is connected to the base 6 with an axis C so as to be connected.

  The base 6 further includes an operation unit 8 for an operator to adjust the height of the photographing table 4 (that is, the height of the arm 5) and the inclination of the photographing table 4 (that is, the inclination of the arm 5), and an operation. Arm moving means 9 for moving the arm 5 up and down and rotating in accordance with an input from the unit 8 is provided.

  The operation unit 8 is an operation panel, a foot pedal, or the like attached to the base 6, and the height of the arm 5 is adjusted to a position suitable for imaging by the operator according to the physique of the subject and the size / position of the breast. This is for inputting instructions for changing the direction and instructions for breast compression. For example, when the operator presses a button on the operation panel once, the amount of vertical movement or rotation by one operation is sent to the arm moving means 9.

  The arm moving means 9 includes an arm rotating means 91 for rotating the arm 5 and an arm height adjusting means (photographing table height adjusting means) 92 for adjusting the height of the photographing table 4 by moving the arm in the vertical direction. Prepare.

  The arm rotation means 91 rotates the axis C attached to the base 6 according to the inclination of the arm input from the operation unit 8.

  The imaging table height adjusting unit 92 moves the arm up and down according to the height of the imaging table 4 input from the operation unit 8.

  Further, the arm moving means 9 is provided with a movement amount storage unit (not shown) for storing the amount of movement of the arm 5 by the operation of the operator, and the vertical movement amount and rotation angle from the origin position of the arm 5 are determined. Remember.

  The arm 5 is provided with an attachment portion 51 for attaching a compression plate 7 that presses the breast M against the imaging table 4 between the radiation irradiation unit 3 and the imaging table 4. A compression plate moving means 52 that moves up and down in the vertical direction and a compression plate size detection means 53 that detects the size of the attached compression plate 7 are provided. On the other hand, the compression plate 7 is provided with an insertion portion 54 for insertion into the attachment portion 51 of the arm 5.

  The compression plate 7 is prepared in different sizes depending on the size of the breast, the size for the large breast is about 30 cm × 24 cm, and the size for the small size is about 24 cm × 18 cm. Further, the length of the insertion portion 54 of the compression plate 7 varies depending on the size of the compression plate 7.

  The compression plate size detection means 53 is provided in the attachment portion 51 of the arm 5 and detects the size of the compression plate 7 by detecting the length of the insertion portion 54 inserted using a dip switch or a photo sensor. Alternatively, even if the barcode reader includes a barcode including size and model number information attached to the side surface of the compression plate 7 and is installed so that the compression plate 7 can be inserted into the mounting portion 51 and read the barcode simultaneously. Good.

  As shown in FIG. 3, a flat panel detector 10 for recording image information corresponding to the dose that has been irradiated with radiation and transmitted through the breast, and outputting image data representing the recorded image information, is provided inside the imaging table 4. And a radiation dose measuring means for measuring the dose of radiation that has passed through the breast and reached the imaging table 4 under the flat panel detector 10 is disposed.

  The radiation dose measuring means is provided under the flat panel detector 10 and detects the dose of the radiation irradiated by the radiation irradiating unit 3 that has passed through the breast, and the position of the dose detector 20 is changed to the center of the breast. And a dose detection position changing means 21 for performing the above.

  Further, the axis C serving as the center of rotation is attached to the center position of the flat panel detector 10 so that the center of rotation of the arm 5 is the center of the flat panel detector 10, and the arm 5 is attached to the base 6 (see FIG. 2). .

  Hereinafter, the structure of the imaging stand 4 when the flat panel detector 10 is a solid state detector will be described with reference to FIGS. 4 to 7.

  As shown in FIG. 4, a reading exposure light source unit 73 and a reading exposure light source unit 73 that are used when reading image information recorded on the solid state detector 10 are arranged in the sub-scanning direction. A reading exposure light source unit moving means 75 to be moved; a current detection unit 72 for obtaining an image signal by detecting a current flowing out from the solid detector 10 at the time of scanning exposure to the solid detector 10 by the reading exposure light source unit 73; A high-voltage power supply unit 71 that applies a predetermined voltage to the detector 10, a pre-exposure light source unit 60 that irradiates the solid-state detector 10 with pre-exposure light before imaging starts, and the solid-state detector 10 within the imaging table 4. A solid detector moving means 70 for moving in a direction to approach the examiner's chest wall H and a direction away from the chest wall H (the above-described sub-scanning direction), a reading exposure light source unit 73, a current detection unit 72, and a high voltage power supply unit. 71, Pre-exposure light source 60, a control unit 80 for controlling the moving means 70 and 75 are arranged.

  The solid state detector 10 is a direct conversion type and optical readout type radiation solid state detector, which records the image information as an electrostatic latent image by irradiating the recording light carrying the image information. By scanning, a current corresponding to the electrostatic latent image is generated. Specifically, as shown in FIG. 5, radiation formed on the glass substrate 16 and transmitted through the breast M (hereinafter, recorded) A first conductive layer 11 that is transparent to light), a recording photoconductive layer 12 that exhibits electrical conductivity when irradiated with recording light, and a latent charge charged to the first conductive layer 11. The charge transport layer 13 that acts as an insulator for the image polarity charge and acts as a conductor for the transport polarity charge opposite to the latent image polarity charge is irradiated with the reading light. Reading that generates electric charge and exhibits conductivity The photoconductive layer 14, in which the second conductive layer 15 permeable to the reading light are laminated in this order. A power storage unit 17 is formed at the interface between the recording photoconductive layer 12 and the charge transport layer 13.

  Each of the first conductive layer 11 and the second conductive layer 15 forms an electrode. The electrode of the first conductive layer 11 is a two-dimensional flat plate electrode, and the electrode of the second conductive layer 15 is hatched in the figure. As shown in FIG. 4, a large number of elements (linear electrodes) 15a for detecting recorded image information as image signals are formed as stripe electrodes arranged in a stripe shape at a pixel pitch (for example, JP-A-2000-2000). No. 105297). The arrangement direction of the elements 15a corresponds to the main scanning direction, and the longitudinal direction of the elements 15a corresponds to the sub scanning direction.

  The solid-state detector 10 has a long side of 30 cm × a short side of 24 cm so as to be compatible with a large breast, and has an imaging table so that the long side direction is the main scanning direction and the short side direction is the sub-scanning direction. 4 is accommodated.

  The reading exposure light source unit 73 includes a line light source configured by arranging a plurality of LED chips in a line and an optical system that linearly irradiates light output from the light source on the solid state detector 10. Is used. The light source unit 73 is scanned in the longitudinal direction of the stripe electrode 15a of the solid state detector 10, that is, in the sub-scanning direction by the moving means 75 made of a linear motor while maintaining a necessary distance from the solid state detector 10. 10 exposures are performed on the entire surface. The reading exposure light source unit 73 and the moving unit 75 constitute a reading light scanning unit.

  FIG. 6 is a diagram showing details of the connection mode of the solid state detector 10 and the current detection means 72. As shown in the drawing, each of the elements 15a of the solid state detector 10 is formed on a TAB (Tape Automated Bonding) film 32 on a side in contact with the chest wall H of the subject via a print pattern (not shown). Further, the charge amplifier IC 33 is connected to the printed circuit board 31 via a print pattern (not shown) formed on the TAB film 32. In the present embodiment, not all the elements 15a are connected to one charge amplifier IC33, but a few to several tens of charge amplifier ICs 33 are provided as a whole, and several to about a hundred adjacent elements are sequentially provided. Each 15a is connected to each charge amplifier IC33.

  The current detection means 72 is not limited to the above-described embodiment, and is called so-called COG (Chip On Glass) in which the charge amplifier IC 33 is formed on the glass substrate 16 without being formed on the TAB film 32. It is good also as an aspect.

  FIG. 7 is a block diagram showing the details of the current detection means 72 and the high voltage power supply unit 71 provided in the imaging table 4 and the connection mode between them and the solid state detector 10.

  The high voltage power supply unit 71 is a circuit in which a high voltage power supply 711 and a bias switching unit 712 are integrated, and the high voltage power supply 711 is once biased for switching a bias application / short circuit to the electrostatic recording unit 10. It is connected to the electrostatic recording unit 10 via a switching unit 712. This circuit is designed to prevent an excessive charge / discharge current in order to limit the peak value of the current flowing at the time of switching and to prevent the destruction of the location where the current of the device is concentrated.

  The charge amplifier IC 33 provided on the TAB film 32 multiplies signals from a large number of charge amplifiers 33a and sample hold (S / H) 33b connected to each element 15a of the solid state detector 10 and each sample hold 33b. A multiplexer 33c for multiplexing is provided. The current flowing out from the solid state detector 10 is converted into a voltage by each charge amplifier 33a, the voltage is sampled and held at a predetermined timing by the sample hold 33b, and the voltage corresponding to each element 15a sampled and held is in the order of arrangement of the elements 15a. The signals are sequentially output from the multiplexer 33c so as to be switched (corresponding to a part of main scanning). The signal sequentially output from the multiplexer 33c is input to the multiplexer 31c provided on the printed circuit board 31, and further, the voltage corresponding to each element 15a is sequentially output from the multiplexer 31c so as to be switched in the arrangement order of the elements 15a, thereby completing the main scanning. To do. The signals sequentially output from the multiplexer 31c are converted into digital signals by the A / D converter 31a, and the digital signals are stored in the memory 31b.

  As the pre-exposure light source unit 60, a light source that emits and extinguishes light in a short time and has a very small afterglow is required. Therefore, an external electrode type rare gas fluorescent lamp is used in the present embodiment. Specifically, as shown in FIG. 4, the pre-exposure light source unit 60 is inserted between a plurality of external electrode type rare gas fluorescent lamps 61 extending in the depth direction of the drawing sheet and between the fluorescent lamps 61 and the solid state detector 10. The wavelength selection filter 62 and a reflector 63 disposed behind the fluorescent lamp 61 for efficiently reflecting the light output from the fluorescent lamp 61 toward the solid state detector 10 are provided. The pre-exposure light only needs to be applied to the entire second electrode layer 15 of the solid state detector 10, and no condensing means is required. However, the illuminance distribution is preferably small. As the light source, for example, an LED chip arranged in a plane can be used instead of the fluorescent lamp.

  The moving means 70 is constituted by a linear motor or the like (not shown), and reciprocates the solid detector 10 between the imaging position and the reading position.

  In addition to the solid state detector described above, the flat panel detector has a TFT readout system that reads out the signal charge accumulated in the power storage unit of the solid state detection element by scanning the TFT connected to the power storage unit. It can be used (for example, see JP 2004-80749 A, JP 2004-73256 A, etc.).

  The dose detector 20 is installed in the lower part of the solid state detector 10, and as the dose detector 20, for example, an AEC sensor in which semiconductor detectors are arranged as a sensor for measuring a radiation dose is used. Or you may make it detect from the dose of the radiation irradiated to the solid state detector 10 (or a TFT type flat panel detector may be sufficient). Hereinafter, in the present embodiment, the dose detector 20 will be described as an AEC sensor.

  The dose detection position changing means 21 uses a pulse motor or the like to move the dose detector 20 in parallel with the solid state detector 10 along the side facing the chest wall H of the imaging table 4 to change the radiation dose detection position. To do.

  Next, the operation of the breast image capturing apparatus 1 configured as described above will be described in the case where the subject's breast is subjected to MLO imaging.

  Since the breast is three-dimensional and thick, if you take a picture as it is, the mammary gland, fat, blood vessels, etc. may be damaged and the tumor may not be copied. Stretch thin and evenly with a small amount of radiation so that even a small lump shadow is clearly projected. Further, in order to apply pressure evenly, it is necessary to apply uniform pressure. However, when a large compression plate 7 is used when the subject's breast is small, there is a gap around the breast. Since the compression plate 7 is inclined and the breast cannot be pressed uniformly, the compression plate 7 having a size suitable for the size of the breast must be attached to the breast imaging apparatus 1.

  In addition, in the case of a small breast, a large-sized compression plate is difficult to remove the hand because the back of the operator's hand is pressed over a large area after positioning.

  Therefore, the operator performs imaging by attaching the compression plate 7 corresponding to the size of the breast of the subject to the attachment portion 51 of the arm 5. When attached to the attachment portion 51 of the breast image pickup apparatus 1, the size of the compression plate 7 attached by the compression plate size detection means 53 is detected.

  Next, in order to perform MLO imaging, when the subject stands beside the breast image capturing apparatus 1, the operator selects the height of the imaging table 4 from the operation unit 8 such as an operation panel according to the height of the subject. And the arm is adjusted by the imaging table height adjusting unit 92 of the arm moving unit 9 until the imaging table 4 reaches the input height. Further, the rotation angle of the arm is input from the operation unit 8 according to the size and shape of the breast of the subject, and the arm 5 is rotated by the arm rotation means 91 so as to be the input rotation angle. At this time, the imaging table 4 is tilted within a range of 45 ° to 80 ° from the horizontal direction so that the imaging table 4 is parallel to the pectoral muscle of the subject. Usually, the photographing table 4 is photographed with an inclination of about 60 °. Further, depending on whether the right or left breast is to be photographed, the tilting direction may be as shown in FIGS. 8A and 8B (FIG. 8A is the right breast and FIG. 8B is the left breast). It will be the opposite.

  Further, since the upper part of the tilted imaging table 4 is applied to the pectoral muscle, imaging is performed when a small breast is imaged on the imaging table 4 for the large breast, as shown in FIG. The picture is taken in a state where it is not in the center of 4 but is shifted to either one. In order to reduce the exposure dose while taking an image of the breast at an appropriate density, it is necessary to detect the radiation dose transmitted through the center of the breast by the AEC sensor 20, but in the case of photographing a small breast It cannot be detected accurately because it is in a shifted position.

  Therefore, the radiation dose measuring means moves the AEC sensor 20 that measures the dose of the radiation irradiated by the radiation irradiation unit 3 to the imaging table 4 on the extended line connecting the radiation irradiation unit 3 and the center of the breast M. Let

  First, the breast size detection means estimates the breast size from the size of the compression plate 7 detected by the compression plate size detection means 53. If the compression plate 7 is small, the size of the breast M of the subject is small. If the compression plate 7 has a large size, it is detected that the size of the breast M of the subject is large.

  In addition, when a small breast is imaged, it is imaged in a state of being biased to either side (see FIG. 8), but the rotation direction of the arm differs depending on which of the left and right breasts M is to be imaged. The direction deviated from the center of the imaging table 4 can be seen. Therefore, the breast position detecting means determines the position of the breast M of the subject placed on the imaging table 4 from the breast size detected by the breast size detecting means and the rotation direction of the arm rotated by the arm rotating means 91. To detect. When the size of the breast M is large, it is assumed that it exists in the vicinity of the center of the imaging table 4, and when the size of the breast M is small, it is assumed that the breast is uniformly displaced from the center by the distance d.

  Therefore, the radiation dose measuring means moves the AEC sensor 20 by the dose detection position changing means 21 according to the position of the breast M detected by the breast position detecting means, and the radiation passes through the center of the breast and the radiation enters the imaging table 4. Measure the dose reached. When the size of the compression plate 7 detected by the compression plate size detection unit 53 is small, the breast size detection unit determines that the breast size of the subject is small, and the AEC sensor 20 determines the center of the breast. The position of the AEC sensor 20 is moved by a predetermined distance d along the side (long side direction) facing the chest wall H of the imaging table 4 by the dose detection position changing means 21. For example, d is about 3 cm, which is half of the difference in length in the long side direction between the large size compression plate and the small size compression plate. Also, since the direction of the arm rotation angle θ differs depending on which of the left and right breasts is imaged, the direction in which the AEC sensor 20 is moved is reversed according to the rotation direction (or rotation angle θ).

  Further, when the photographing table 4 is tilted and the upper part of the photographing table 4 is applied to the pectoral muscle H, the photographing position becomes higher as the photographing table 4 is tilted as shown in FIG. Therefore, by lowering the arm 5 by h by the arm moving means 9 according to the inclination of the imaging table 4, it is possible to reduce the trouble of the operator and the burden on the subject.

h is obtained by the following equation, where d is the amount of movement of the AEC sensor and θ is the inclination of the arm 5.
h = d × cos θ
When the photographing table 4 has an optimum inclination for photographing, the breast is compressed with the compression plate 7.

  When the operator inputs an instruction to gradually pressurize the breast using the operation unit 8 such as an operation panel or a foot switch while confirming the compressed state of the breast, the compression plate moving means 52 performs the longitudinal direction of the arm 5 according to the input. The pressure plate 7 is gradually pushed down. For example, the pressing force is applied in units of 1 kg each time the foot switch is pressed, and the foot switch is pressed so that the breast has a thickness suitable for imaging. Or you may make it pressurize gradually, when a compression board falls and touches a breast.

  When the compression is completed, the breast is imaged by irradiating radiation from the radiation source 2 of the radiation irradiating unit 3.

  In the above description, the case where the size of the breast is determined from the size of the compression plate has been described. However, the breast size detection unit performs pre-exposure with a small amount of dose before performing the main imaging so that the size of the breast is determined. You may make it detect. Specifically, for example, since an image obtained by the solid detector 10 by pre-exposure has different pixel values in the breast region and the region directly irradiated with radiation, binarization processing is performed with a predetermined threshold value. The breast region is extracted, and the size of the breast is determined from the number of pixels of the extracted breast region and the length of the image edge on the chest wall H side.

  Alternatively, the size may be detected using a past inspection image or an image taken immediately before.

  The movement amount of the AEC sensor 20 is divided into several stages according to the size of the detected breast when detecting the size of the breast from an image obtained by pre-exposure. A plurality of movement amounts according to the stage may be prepared.

  Alternatively, as shown in FIG. 15, a CCD camera 25 is installed near the radiation source 2 as a breast size detection unit, a compressed breast is photographed, and the size of the breast region is larger than the image obtained by the CCD camera 25. You may make it detect. Alternatively, the size of the breast region may be detected by irradiating ultrasonic waves and using the reflected waves. If these methods are used, the breast size can be detected without exposing the subject. In addition, a delicate movement of the compression plate can be realized so that the compression plate and the center of the breast are aligned. Furthermore, even if the operator accidentally wears a large compression plate, the operator is warned to move the compression plate so that the compression plate and the center of the breast are aligned, or to change the compression plate. Also good.

  Alternatively, a strain gauge may be provided on the imaging stand 4 and the breast weight may be calculated from the strain gauge value to detect the size of the breast. Alternatively, the size of the breast can be detected from an image inspected immediately before mammography imaging using ultrasound.

In the above description, the case where the breast position detecting unit detects the position of the breast M according to the size of the breast detected by the breast size detecting unit and the rotation direction in which the arm moving unit rotates the arm has been described. As shown in FIG. 16, strain gauges 41 may be provided at both ends of the imaging table 4 and the position may be estimated by looking at the balance of both outputs. When pressure is applied to the imaging table 4, distortion occurs, and the resistance value of the strain gauge 41 changes according to the distortion. Therefore, the resistance value is detected and the position of the breast placed on the imaging table 4 is determined at both ends. The position of the breast can be estimated from the difference in output output from the strain gauge 41. For example, the position of the breast is expressed by the following equation using the difference between the outputs of the two strain cages 41 and the compression pressure applied to the compression plate.
Breast position = fx (compression pressure, difference between the outputs of the two strain cages)
Further, a temperature sensor may be provided on the side of the imaging table 4 facing the chest wall H, and the position of the breast may be detected from the position where the subject is in contact with the imaging table 4.

  When performing MLO imaging, the position where the breast M is placed on the imaging table 4 may be estimated according to the height adjusted by the imaging table height adjusting unit 92. When performing MLO imaging, the arm is rotated by the arm rotating means 91 and the imaging platform is tilted to perform imaging. Further, when the height is high in accordance with the height of the subject, the breast M is at a high position, and thus the imaging table 4 is raised, and if the height is high, the distance from the armpit to the center of the breast is also increased. Since it is large, the breast M is placed near the center of the imaging table 4 tilted obliquely. However, when the height is low, the breast M is placed not in the vicinity of the center of the photographing table 4 but in a position slightly shifted upward. Therefore, a table as shown in FIG. 17 is prepared based on the result of measuring the correspondence between the height of the imaging table 4 and the position of the breast M of the subject in the case of MLO imaging, and the imaging table 4 is based on the table. And the approximate position where the breast M deviates from the center of the imaging table 4 can be estimated. The radiation source 2 or the imaging table 4 is moved based on the values in this table.

  Further, when the breast M is large, the photographing table 4 is photographed without being largely inclined, but when the breast M is small, photographing is performed by tilting the photographing table 4 so as to be close to the vertical direction. The position of the breast may be estimated according to the inclination of the imaging table 4.

  In addition, when the breast M placed on the imaging table 4 is pressurized with the compression plate 7, the small breast is offset to one of the imaging tables 4, so that the pressurized compression plate 7 and the imaging table 4 are parallel to each other. First, as shown in FIG. 18, the compression plate 7 is slightly inclined with respect to the imaging table 4. By detecting this inclination, the approximate position of the breast M on the imaging table 4 can be estimated. Therefore, a compression plate inclination detecting means 55 for detecting an angle δ at which the compression plate 7 is inclined with respect to the imaging table 4 is provided in the insertion portion 54 of the compression plate 7. The position of the breast M on the imaging table 4 may be estimated according to the tilted angle. Specifically, the deviation can be detected from the stress of the two insertion portions 54 that support the compression plate 7.

  Further, when the compression plate 7 is provided so as not to be inclined with respect to the imaging table 4, the position of the breast M may be estimated from only the stress distribution applied to the compression plate 7 or the imaging table 4.

  Alternatively, as shown in FIG. 19, when imaging is performed with the irradiation field stop 18 attached to the radiation storage unit (radiation irradiation unit) 3 that stores the radiation source 2, the breast M is mounted so as to be the center of the image. Therefore, the position where the irradiation field stop 18 is attached can be detected by using a dial or the like for adjusting the irradiation field size of the side facing the chest wall H or the side perpendicular to the side of the irradiation field stop attached to the radiation storage unit 3. Such an irradiation field stop detection means 26 may be provided, and the position of the breast M on the imaging table 4 may be estimated according to the position of the irradiation field stop 18 attached to the radiation storage unit 3.

  In the above description, the case where the AEC sensor is moved so as to detect the dose of radiation irradiated from the radiation irradiating unit through the center of the breast and reaching the imaging table has been described. However, the captured image is optimized. What is necessary is just to move an AEC sensor so that the dose which permeate | transmitted the site | part (region of interest) which irradiates radiation, and arrived at the imaging | photography stand may be detected.

  Further, as shown in FIG. 10, the first switching means for switching whether or not to move the position of the dose detector to the dose detection position changing means 21 in accordance with the size detected by the compression plate size detecting means 53. 22, when the size of the compression plate 7 detected by the compression plate size detection means 53 is large, the moving function of the AEC sensor 20 is turned off and the size of the compression plate 7 detected by the compression plate size detection means 53 is small. Only at times may the movement function of the AEC sensor 20 be turned on.

  In the above description, the case where there is one AEC sensor has been described. However, when a plurality of AEC sensors are arranged along the side facing the chest wall of the imaging table 4 as shown in FIG. 21 may be a dose detection position selection means for selecting any of the dose detectors of the plurality of AEC sensors 20 arranged side by side.

  Furthermore, as shown in FIG. 20 (the figure when the imaging table 4 is viewed from the surface on which the breast M is placed), the dose detection position changing means 21 moves the AEC sensor 20 away from the side facing the chest wall H of the imaging table 4. Some of the AEC sensors 20 are selected according to the position of the breast M, and further, the position of the selected AEC sensor 20 is moved along the side facing the chest wall H (arrow in FIG. 20). You may make it make it.

  As described above in detail, by moving the AEC sensor and detecting the radiation dose at the center position of the breast, an image with the optimum density can be taken, and the exposure dose of the subject can be reduced. can do.

  Further, the dose is detected by using the flat panel detector 10 instead of the AEC sensor, and the dose detection position selection means divides the flat panel detector 10 into several regions (shaded portions) as shown in FIG. It may be configured to function as a dose detector and detect a dose by selecting one of the divided areas.

  Next, a second embodiment will be described. In the present embodiment, the same components as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 11 is a schematic view showing a second embodiment of a breast image pickup apparatus according to the present invention. An image capturing apparatus for breast 1a according to the present invention includes the image capturing apparatus for breast 1 according to the first embodiment and further includes a compression plate pressing position moving unit 56.

  In order to apply pressure evenly to the breast, it is necessary to apply uniform pressure. When the subject's breast is small, a small compression plate 7 is used. In order to compress the breast evenly, it is desirable to compress the vicinity of the center of the breast.

  Therefore, as shown in FIG. 12, when the size of the compression plate 7 detected by the compression plate size detection unit 53 is small, the compression plate compression position moving unit 56 places the AEC sensor 20 at the center of the breast. The position of the compression plate 7 is moved in the direction along the side facing the chest wall H of the imaging table 4 by the compression plate compression position moving means 56 so that the compression plate 7 comes to the center of the breast. The arm 5 is moved in the direction crossing the arm 5 by substantially the same movement amount d as the AEC sensor 20.

  Further, the compression plate compression position moving means 56 is provided with second switching means 57 for switching whether or not to move the position of the dose detector according to the size detected by the compression plate size detection means 53. When the size of the compression plate 7 detected by the size detection means 53 is large, the moving function of the compression plate 7 is turned off, and only when the size of the compression plate 7 detected by the compression plate size detection means 53 is small. You may do it.

  Further, when the size of the breast is small, as shown in FIG. 13, the radiation that passes through the breast from the radiation source 2 proceeds in the direction of the diagonal line, so that the dose transmitted through the center position of the breast is accurately detected. Therefore, the movement amount d2 of the AEC sensor 20 may be larger than the movement amount d1 of the compression plate 7.

  Although the case where both the AEC sensor and the compression plate are moved has been described above, only the compression plate may be moved.

  As described above in detail, it is possible to uniformly compress the breast by moving the compression plate so as to come to the center of the breast.

  Further, in each of the above-described embodiments, the mode in which the axis C serving as the center of rotation is attached to the center position of the flat panel detector has been described. However, in consideration of the thickness of the breast, both center positions are shifted. The amount of vertical movement of the arm may be adjusted by adding this amount of deviation.

  Further, although the AEC sensor is used as the dose detector, a flat panel detector may be used, and the target X-ray intensity can be obtained by using pre-exposure. In this case, the area used as the AEC sensor may be switched or the position of the mammary gland may be detected by image recognition or the like, and the weight of the image area may be changed when obtaining the X-ray intensity.

DESCRIPTION OF SYMBOLS 1,1a Breast imaging device 2 Radiation source 3 Radiation irradiation part 4 Imaging stand 5 Arm 6 Base 7 Compression plate 8 Operation part 9 Arm moving means 10 Flat panel detector 18 Irradiation field stop 20 Dose detector 21 Dose detection position change Means 22 First switching means 24 Scatter removal grid 25 CCD camera 26 Irradiation field stop detection means 41 Strain gauge 51 Attaching portion 52 Compression plate moving means 53 Compression plate size detection means 54 Insertion portion 55 Compression plate inclination detection means 56 Compression plate Compression position moving means 57 Second switching means 86 Radiation irradiation part moving means
88 Shooting table moving means 91 Arm rotating means 92 Arm height adjusting means C axis

Claims (4)

A radiation irradiation unit for irradiating the breast of the subject;
An imaging table on which the breast is placed;
An arm that connects the radiation irradiation unit and the imaging table to face each other;
A compression plate that compresses the breast on the imaging table provided between the radiation irradiation unit and the imaging table;
Breast position detection means for detecting the position of the breast on the imaging table along the side of the imaging table that faces the chest wall of the subject;
A compression for detecting an angle at which the compression plate is inclined with respect to a side of the imaging table facing the chest wall of the imaging table when the breast is sandwiched between the compression plate and the imaging table. Plate inclination detection means,
The breast position detecting means is
A breast image photographing apparatus, wherein the position of the breast on the photographing table is estimated according to an angle at which the compression plate is inclined with respect to the photographing table. 2. The breast image photographing apparatus according to claim 1, further comprising an image recording medium for recording image information corresponding to a dose that has been irradiated with the radiation and transmitted through the breast inside the photographing stand. Based on the position of the breast detected by the breast position detecting means, the dose at which the radiation irradiated by the radiation irradiation unit reaches the imaging table on the line connecting the radiation irradiation unit and the region of interest of the breast is measured. mammography apparatus according to claim 1, wherein further comprising a radiation dose measuring means for. Based on the position of the breast detected by the breast position detecting means, further provided is a compression plate compression position moving means for moving the position where the compression plate compresses the breast along the side facing the chest wall of the subject. The mammography apparatus according to any one of claims 1 to 3 , wherein the mammography apparatus is provided.

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