Abstract:
A bed-type compression mechanism of related art is still desired to be improved to reduce a burden on a subject and to increase operability of an operator. 
     An apparatus includes a bed configured to support a subject and having an insertion hole through which a subject portion that is part of the subject is inserted; a pair of compression plates configured to hold and compress the subject portion when the subject portion is inserted through the insertion hole; a camera configured to capture an image of the subject portion; and an illumination device configured to irradiate the subject portion inserted through the insertion hole with light from a side opposite to the insertion hole when the image of the subject portion is captured.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an apparatus. 
       BACKGROUND ART 
       [0002]    An X-ray diagnostic apparatus or an acoustic-wave acquiring apparatus has been known as an example of a measurement apparatus that acquires biological information. An acoustic-wave acquiring apparatus may be, for example, an apparatus using an ultrasonic echo or an apparatus using a photoacoustic effect. To obtain a good measurement result by such a measurement apparatus, a subject portion has to be non-movably held. If the subject portion is a part of diagnostic interest of a living body, such as a breast, a burden on the subject portion during measurement is desired to be reduced as much as possible to prevent a subject from feeling discomfort. 
         [0003]    The photoacoustic effect represents a phenomenon in which when a subject portion is irradiated with pulsed light from a light source such as a laser, the subject portion absorbs optical energy, is expanded and contracted, and generates an acoustic wave (photoacoustic wave). By detecting the photoacoustic wave with use of a probe and performing signal processing and image reconstruction, an optical-property-value distribution in the subject portion is acquired and visualized. 
         [0004]    A configuration including a bed that reduces a burden on a subject and a compression unit configured to provide a projected cross-sectional area of a breast sufficient for image-capturing is disclosed in PTL 1 as an example of the X-ray diagnostic apparatus. 
         [0005]      FIG. 32  is a schematic illustration showing an X-ray mammography apparatus disclosed in PTL 1. This apparatus includes a bed  113  having a breast insertion hole, a compression plate  102  that compresses a breast  112 , and an X-ray film table  101 . The X-ray film table  101  is arranged such that the X-ray film table  101  and the compression plate  102  compress the breast  112 . The X-ray film table  101  includes therein an X-ray film  105 . A subject lies on the bed with her face down during image-capturing and inserts the breast  112  into the breast insertion hole. The inserted breast  112  is inserted to an area between the compression plate  102  and the X-ray film table  101 . In this state, the compression plate  102  is moved to compress the breast  112 . Then, an X-ray source  117  irradiates the breast  112  with an X-ray beam and an image of the breast  112  is captured. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: Japanese Patent Laid-Open No. 7-303633 
       
     
       SUMMARY OF INVENTION 
       [0007]    With the configuration of PTL 1, since the subject lies on the bed with her face down, the breast sags vertically downward. Hence, the projected cross-sectional area becomes large by the sagging amount. However, the bed-type compression mechanism of related art is still desired to be improved to reduce a burden on a subject and to increase operability of an operator. 
         [0008]    The present invention reduces a burden on a subject and increases operability of an operator. 
         [0009]    According to an aspect of the present invention, an apparatus includes a bed configured to support a subject and having an insertion hole through which a subject portion that is part of the subject is inserted; a pair of compression plates configured to hold and compress the subject portion when the subject portion is inserted through the insertion hole; a camera configured to capture an image of the subject portion; and an illumination device configured to irradiate the subject portion inserted from the insertion hole with light through a side opposite to the insertion hole when the image of the subject portion is captured. 
         [0010]    With the aspect of the present invention, since the illumination device that irradiates the subject portion from the lower side is provided, the subject portion can be properly compressed and compression does not have to be retried again. Accordingly, a burden on the subject can be reduced. Also, operability of the operator can be increased. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is an external perspective view showing an acoustic-wave acquiring apparatus to which the present invention can be applied. 
           [0012]      FIG. 2  is a partial perspective view showing the acoustic-wave acquiring apparatus to which the present invention can be applied. 
           [0013]      FIG. 3  is an illustration explaining a measurement method. 
           [0014]      FIG. 4  is an illustration explaining a state during measurement. 
           [0015]      FIG. 5  is an illustration explaining a state during measurement. 
           [0016]      FIG. 6  is an illustration explaining a state during measurement. 
           [0017]      FIG. 7  is a partial perspective view showing the acoustic-wave acquiring apparatus to which the present invention can be applied. 
           [0018]      FIG. 8  is a partial perspective view showing the acoustic-wave acquiring apparatus to which the present invention can be applied. 
           [0019]      FIG. 9  is a perspective view of a compression mechanism. 
           [0020]      FIG. 10  is a perspective view of a scanning system. 
           [0021]      FIG. 11  is a perspective view of the scanning system. 
           [0022]      FIG. 12  is a perspective view of the compression mechanism. 
           [0023]      FIG. 13  is a perspective view of the compression mechanism. 
           [0024]      FIG. 14  is a perspective view of the compression mechanism. 
           [0025]      FIG. 15  is a partial perspective view of the compression mechanism. 
           [0026]      FIG. 16  is a perspective view of the compression mechanism. 
           [0027]      FIG. 17  is a partial perspective view of the compression mechanism. 
           [0028]      FIG. 18  is a perspective view of an electric compression mechanism. 
           [0029]      FIG. 19  is a partial perspective view of the electric compression mechanism. 
           [0030]      FIG. 20  is a partial perspective view of the electric compression mechanism. 
           [0031]      FIG. 21  is a partial perspective view of the electric compression mechanism. 
           [0032]      FIG. 22A  illustrates part of a flowchart showing a compression sequence according to an embodiment of the present invention. 
           [0033]      FIG. 22B  illustrates part of the flowchart showing the compression sequence according to the embodiment of the present invention. 
           [0034]      FIG. 23A  illustrates part of a flowchart showing a compression sequence according to the embodiment of the present invention. 
           [0035]      FIG. 23B  illustrates part of the flowchart showing the compression sequence according to the embodiment of the present invention. 
           [0036]      FIG. 24  is an illustration explaining an operation of a compression release mechanism. 
           [0037]      FIG. 25  is an illustration explaining an operation of the compression release mechanism. 
           [0038]      FIG. 26  is an illustration explaining an operation of the compression release mechanism. 
           [0039]      FIG. 27  is an illustration explaining an operation of the compression release mechanism. 
           [0040]      FIG. 28  is an illustration explaining an operation of the compression release mechanism. 
           [0041]      FIG. 29  is an illustration explaining an operation of the compression release mechanism. 
           [0042]      FIG. 30  is an illustration explaining an operation of the compression release mechanism. 
           [0043]      FIG. 31  is an arrangement diagram of a monitor camera and an illumination device. 
           [0044]      FIG. 32  is a schematic illustration of an X-ray mammography apparatus of related art. 
           [0045]      FIG. 33A  is a schematic illustration when a subject portion is compressed. 
           [0046]      FIG. 33B  is a schematic illustration when the subject portion is compressed. 
           [0047]      FIG. 34  is a perspective view of a compression mechanism. 
           [0048]      FIG. 35  is a cross-sectional view of the compression mechanism. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0049]    According to an embodiment of the present invention, a measurement apparatus includes an apparatus using an ultrasonic echo technique that transmits an ultrasonic wave to a subject portion and receives a reflected wave (reflected ultrasonic wave) reflected in the subject portion; and an apparatus using a photoacoustic effect that irradiates a subject portion with light (electromagnetic wave) and receives an acoustic wave (typically, ultrasonic wave) generated in the subject portion. The present invention can be also applied to an X-ray diagnostic apparatus like the apparatus described in PTL 1. According to the embodiment of the present invention, an acoustic wave is typically an ultrasonic wave, and includes elastic waves called a sonic wave, an acoustic wave, a photoacoustic wave, and a photoultrasonic wave. A probe receives an elastic wave that is generated or reflected in a subject portion. 
       Basic Configuration 
       [0050]      FIGS. 1 and 2  are illustrations showing appearance of an acoustic-wave acquiring apparatus according to an embodiment of the present invention. In the embodiment described here, a breast is measured as a subject portion that is part of the body of a subject. Reference sign  1  denotes a bed that allows a subject to take a prone position (face-down position). Reference sign  2  denotes a compression measurement unit that is hung below a breast insertion hole  1   a  of the bed  1  in a slidable manner. The compression measurement unit  2  has a manipulation opening  2   a  for a manipulation when a breast is held and compressed. 
         [0051]    By rotating a slide handle  3 , the compression measurement unit  2  can slide relative to the bed  1  in a left-right direction. Reference sign  4  denotes a manual compression handle. By rotating the manual compression handle  4 , a movable compression plate  12  is advanced toward and retracted from a fixed compression plate  10 . The fixed compression plate  10  and the movable compression plate  12  function as a pair of compression plates configured to compress a breast from both sides. Reference sign  5  denotes a state change switch that changes rotation of the manual compression handle  4  between a one-way latch state and a constantly direct-coupled state. The one-way latch state is a state in which the manual compression handle  4  is rotatable when the manual compression handle  4  is rotated in a direction in which the movable compression plate  12  compresses a subject portion (hereinafter, occasionally referred to as compression direction), and the manual compression handle  4  is locked and non-rotatable when the manual compression handle  4  is rotated in a direction in which the movable compression plate  12  releases a subject portion (hereinafter, occasionally referred to as release direction). As described above, since the rotation of the manual compression handle  4  is locked when the manual compression handle  4  is rotated in the release direction of the movable compression plate  12 , a reactive force when the movable compression plate  12  compresses a breast is not generated on the manual compression handle  4 . An operator does not have to always grip the manual compression handle  4  during compression, and an operation becomes easy. 
         [0052]    The constantly direct-coupled state can be set by releasing a one-way mechanism of the one-way latch. The constantly direct-coupled state is a state in which the manual compression handle  4  can be rotated in both the compression direction and the release direction of the movable compression plate  12 . This state is used when compression of a subject in a compressed state is released. Reference sign  6  denotes a foot pedal. The foot pedal  6  is a switch that electrically drives the movable compression plate  12  in the compression direction or the release direction, similarly to the operation of the manual compression handle  4 . 
         [0053]    The foot pedal  6  includes a pedal  6   a  for driving in the release direction and a pedal  6   b  for driving in the compression direction. The foot pedal  6  assists the operation of the manual compression handle  4 . Reference sign  10  denotes the above-mentioned fixed compression plate that is fixed to the compression measurement unit  2 . The fixed compression plate  10  together with the compression measurement unit  2  slides relative to the bed  1  by an operation of the slide handle  3 . Accordingly, one-side compression is performed on a breast inserted through the breast insertion hole  1   a  and an inserted state of the breast can be adjusted by a manipulation. 
         [0054]    Reference sign  11  denotes an under tray that is made of a transparent material according to the embodiment of the present invention. A monitor camera (described later) that allows a compression angle of a breast to be checked, and an LED illumination device (described later) that provides optimal illumination to allow the operator to check a compressed state of the breast are installed below the under tray  11 . 
         [0055]    Reference sign  12  denotes the movable compression plate that is supported by a linear guide (described later), moves in parallel to the fixed compression plate  10 , and hence performs compression and release. Reference sign  13  denotes a base plate of the compression measurement unit  2 . The base plate  13  slides relative to the bed  1  in a direction perpendicular to a surface of the fixed compression plate  10 , which will be described later. Thus, the fixed compression plate  10  can move relative to the bed  1 . By bringing a bottom portion (breast portion at the foot side) of the breast into contact with the fixed compression plate  10  and then moving the movable compression plate relative to the fixed compression plate, the inserted state of the breast can be adjusted, and the compressed state of the breast can become proper. Also, the size of the apparatus can be reduced, and the design of the apparatus can attain energy-saving. Further, the compressed state of the breast can be adjusted in the process of manipulation. Hence, the subject does not have to insert the breast again due to an insufficient compressed state. 
       Measurement Method 
       [0056]      FIGS. 3 to 8  are explanatory illustrations of a measurement method for a subject of the apparatus according to the embodiment of the present invention. 
         [0057]      FIG. 3  is a schematic illustration of a human body. Reference sign A denotes compression in a right medio-lateral oblique (MLO) direction. Reference sign B denotes compression in a left MLO direction. In the embodiment of the present invention, the MLO direction indicates a medio-lateral oblique direction in which a breast is obliquely compressed. Reference sign C denotes a CC direction in which a breast is compressed from a head side to a foot side. In the embodiment of the present invention, the CC direction indicates a cranio-caudal direction. Normally during the compression in the CC direction of reference sign C, a left breast and a right breast are measured individually. 
         [0058]    In an X-ray mammography, setting positions of the fixed compression plate  10  and the movable compression plate  12  are determined in the respective compression directions in  FIG. 3 . A fixed-compression-plate side of each of the A and B positions in the MLO directions in  FIG. 3  is an armpit side. In particular, the fixed-compression-plate side of the A position is determined as Aa, and the fixed-compression-plate side of the B position is determined as Bb. 
         [0059]    In the embodiment of the present invention, the fixed compression plate  10  is located constantly at the right side of the operator with respect to the manipulation opening  2   a . Hence, at the B position in the MLO direction in  FIG. 3 , the fixed compression plate  10  is located at the same position as the fixed-compression-plate position in an X-ray mammograph. In contrast, during compression at the A position in the MLO direction, as shown in  FIG. 4 , the fixed compression plate  10  at the A position is located at Ab. 
         [0060]    When compression is performed similarly to the X-ray mammography, during compression at the A position in the MLO direction, the fixed compression plate  10  is set at Aa. However, in the case of the bed-type MLO measurement apparatus according to the embodiment of the present invention, a subject may overly on the operator, and hence measurement cannot be carried out. Owing to this, in the embodiment of the present invention, a MLO receiving plate  7  is provided as shown in  FIG. 8  so that the fixed compression plate  10  at the A position is located at Ab and the measurement can be carried out in the state shown in  FIG. 4 . 
         [0061]      FIG. 7  illustrates a state in which the MLO receiving plate  7  is not provided. When the subject takes the prone position in this state for right MLO measurement in  FIG. 4 , a large gap is present between the fixed compression plate  10  and the movable compression plate  12 . Hence, the abdominal portion or the costal portion of the subject cannot be received by the bed and may protrude to the gap between the compression plates. When the movable compression plate  12  moves toward the fixed compression plate  10  for compression of the breast, the protruding abdominal portion or costal portion may be compressed before the breast is compressed, and the breast, which is a target of compression, may not be compressed. 
         [0062]    Alternatively, the MLO receiving plate  7  may be integrally formed with the base plate  13 , so that the abdominal portion or the costal portion of the subject is received by the integrated configuration and the abdominal portion of the subject can be prevented from protruding to the gap between the compression plates  10  and  12 . Still alternatively, the MLO receiving plate  7  may be formed of a flexible material. When the movable compression plate  12  compresses the breast of the subject, although the abdominal portion of the subject slightly protrudes into the gap between the compression plates  10  and  12 , the abdominal portion of the subject can slide on an upper surface of the movable compression plate  12 . 
         [0063]    As described above, by providing the MLO receiving plate  7  extending in the direction perpendicular to the fixed compression plate  10 , compression in the CC direction and compression in the MLO direction can be carried out. Thus, a measurement range can be markedly expanded. Also, different configurations do not have to be provided for CC and MLO. The space and energy of the apparatus can be saved. 
         [0064]      FIGS. 4 to 6  are illustrations showing positions of a subject during inspections on the acoustic-wave acquiring apparatus according to the embodiment of the present invention.  FIG. 4  illustrates an inspection of a right breast at the A position in  FIG. 3  through compression in the MLO direction.  FIG. 5  illustrates an inspection of a left breast at the B position in  FIG. 3  through compression in the MLO direction.  FIG. 6  illustrates an inspection of a right breast at the C position in  FIG. 3  through compression in the CC direction. 
       Operation of Acoustic-Wave Acquiring Apparatus 
       [0065]      FIGS. 9 to 11  are explanatory perspective views in a state in which the bed  1 , the base plate  13 , etc., are omitted so that compression and a scanning mechanism are exposed.  FIG. 9  is a perspective view showing the entire compression measurement unit  2 . An operation of the acoustic-wave acquiring apparatus is described with reference to  FIG. 9 . 
         [0066]    A laser illumination optical system  20  expands and diffuses a pulsed laser beam that is transmitted from a pulsed laser device (not shown) through a fiber cable  21  into a desired size, and illuminates a breast of a subject compressed by the movable compression plate  12  with the pulsed laser beam through the movable compression plate  12 . 
         [0067]    If a cancer is generated in the breast of the subject, many newborn blood vessels are formed in the cancer, and the amount of blood to the cancer is increased. Blood containing hemoglobin constantly flows in the blood vessels. Hence, if the laser illumination optical system  20  illuminates the breast with the pulsed laser beam (in particular, a near-infrared pulsed laser beam with a wavelength in a range from about 750 to about 1064 nm), the laser beam enters an internal tissue from the surface of the breast while the laser beam is diffused, and the laser beam is absorbed by specific hemoglobin in the blood. The hemoglobin is instantly expanded and contracted. It is known that the instant expansion and contraction of the hemoglobin generates an ultrasonic wave. 
         [0068]    The ultrasonic wave propagates to the fixed compression plate  10  through the tissue of the breast, and is received by an ultrasonic probe  15  arranged on a side of the fixed compression plate  10  opposite to the breast. An ultrasonic-wave generation source is re-constructed by processing a signal received by the ultrasonic probe  15  through arithmetic processing similar to that of a typical ultrasonic diagnostic apparatus. Then, the position of a cluster of the specific hemoglobin in the breast of the subject can be determined. 
         [0069]    Being able to make a diagnosis on a high probability that a cancer is generated in the cluster portion of the specific hemoglobin is the operating principle of the acoustic-wave acquiring apparatus. If the desired pulsed laser beam illuminates the breast of the subject, the ultrasonic wave is generated from the specific hemoglobin. Hence, a strong ultrasonic wave is generated from a portion where hemoglobin is gathered like a cancer. By specifying the location of generation of the strong ultrasonic wave, the presence of a cancer in the breast and the size of the cancer are determined. 
         [0070]    Regarding the operating principle of the acoustic-wave acquiring apparatus, since the pulsed laser beam is diffused in a human body when the pulsed laser beam illuminates the breast, the thickness of the breast has to be reduced as much as possible. Owing to this, the breast is compressed. Also, since the breast is compressed by the movable compression plate  12  and then is illuminated by the laser illumination optical system  20 , the material of the movable compression plate  12  has to have a high transmittance for near-infrared radiation. For example, the material may be acrylic resin. Further, the fixed compression plate  10  has to cause the ultrasonic wave generated from the hemoglobin to propagate to the ultrasonic probe  15  through the tissue in the breast. 
         [0071]    First, to improve acoustic matching between the breast and the fixed compression plate  10 , for example, gel or a urethane gel sheet that is used for ultrasonic diagnosis has to be interposed between the breast and the fixed compression plate  10 . 
         [0072]    Further, a countermeasure for matching acoustic impedances to improve propagation of the ultrasonic wave has to be provided in the fixed compression plate  10  and in a space from the surface of the fixed compression plate  10  to the ultrasonic probe  15 . In the embodiment of the present invention, polymethyl pentene or the like is selected as a material of a countermeasure for a loss of propagation of the ultrasonic wave in the fixed compression plate  10 . Also, the space from the surface of the fixed compression plate  10  to the ultrasonic probe  15  is filled with diisodecyl sebacate or called DIDS (coaster oil), PEG (polyethylene glycol), or the like. 
         [0073]      FIG. 10  illustrates a filling unit configured to fill the space with DIDS (coaster oil), PEG (polyethylene glycol), or the like. The ultrasonic probe  15  is set such that liquid does not leak to a carriage  17 . A packing  17   a  is mounted on the carriage  17 . The packing  17   a  is pressed to the fixed compression plate  10 , and hence a U-shaped space is formed. DIDS (coaster oil), PEG (polyethylene glycol), or the like, is supplied from a supply port  17   b  by an oil pump (not shown), and discharged from a discharge port  17   c.    
         [0074]    If the number of ultrasonic sensors in the ultrasonic probe  15  is increased, the ultrasonic probe  15  becomes very expensive. As the result, the area of the ultrasonic probe  15  may become small with respect to the compressed breast. Owing to this, X-Y drive mechanisms as shown in  FIGS. 10 and 11  support the ultrasonic probe  15  and the laser illumination optical system  20  for scanning along a plane parallel to the compression plates and acquiring an ultrasonic wave. If the ultrasonic probe  15  and the laser illumination optical system  20  constantly face each other during scanning, the ultrasonic wave can be most efficiently acquired. Owing to this, a probe Y-axis drive guide  18 , a probe X-axis drive guide  19 , a phototransmitter Y-axis drive guide  23 , and a phototransmitter X-axis drive guide  24  are used. 
       Scanning System 
       [0075]      FIGS. 10 and 11  are perspective views showing scanning systems according to the embodiment of the present invention.  FIG. 10  shows a scanning system of the ultrasonic probe  15  according to the embodiment of the present invention. The probe Y-axis drive guide  18  includes a drive motor  18   a  that serves as a power source. The drive motor  18   a  transmits rotation to a lead screw  18   c  through a joint  18   b  and hence drives a linear guide  18   d  vertically along the Y-axis. The carriage  17  is fixed to the linear guide  18   d . When the ultrasonic probe  15  vertically moves along the linear guide  18   d , a linear sensor  18   e  provided on a side surface of the linear guide  18   d  reads a position at a linear scale  18   f  and detects a correct scanning position. 
         [0076]    The probe X-axis drive guide  19  has a configuration substantially similar to the probe Y-axis drive guide  18 . A drive motor  19   a  is coupled with a lead screw  19   c  through a joint  19   b . The lead screw  19   c  is rotated and hence a linear guide  19   d  scans horizontally. The probe Y-axis drive guide  18  is directly mounted on the linear guide  19   d , so that the drive mechanism of the probe Y-axis drive guide  18  and the ultrasonic probe  15  scan in the X-axis direction. 
         [0077]      FIG. 11  is a perspective view showing the details of the phototransmitter Y-axis drive guide  23  and the phototransmitter X-axis drive guide  24 . To perform a facing operation precisely with the probe portion, the phototransmitter portion has a configuration similar to the probe portion. The phototransmitter Y-axis drive guide  23  includes a drive motor  23   a  that serves as a power source. The drive motor  23   a  transmits rotation to a lead screw  23   c  through a joint  23   b  and hence drives a linear guide  23   d  vertically along the Y-axis. A phototransmitter carriage  22  is fixed to the linear guide  23   d . When the phototransmitter carriage  22  vertically moves along the linear guide  23   d , a linear sensor  23   e  provided on a side surface of the linear guide  23   d  reads a position at a linear scale  23   f  and detects a correct scanning position. 
         [0078]    The phototransmitter X-axis drive guide  24  has a configuration substantially similar to the phototransmitter Y-axis drive guide  23 . A drive motor  24   a  is coupled with a lead screw  24   c  through a joint  24   b . The lead screw  24   c  is rotated and hence a linear guide  24   d  scans horizontally. The phototransmitter Y-axis drive guide  23  is directly mounted on the linear guide  24   d , so that the drive mechanism of the phototransmitter Y-axis drive guide  23  and the laser illumination optical system  20  scan in the X-axis direction. 
       Compression Mechanism 
       [0079]    Next, a compression mechanism is described.  FIGS. 9 and 12  to  15  are illustrations showing a compression mechanism according to the embodiment of the present invention.  FIG. 9  illustrates arrangement of both compression mechanism and scanning mechanism.  FIGS. 12 and 13  are perspective views extracting only parts relating to compression according to the embodiment of the present invention.  FIGS. 12 and 13  omit illustration of the under tray  11 , so that a monitor camera  58  and a LED illumination device  59  provided below the under tray  11  can be observed.  FIG. 14  is a cross-sectional perspective view showing a mechanism that causes the compression measurement unit  2  to slide relative to the bed  1  through rotation of the slide handle  3 , and a coupling mechanism of the manual compression handle.  FIG. 15  is an enlarged view showing the detail of a phase adjustment plate. 
         [0080]    In  FIG. 9 , the fixed compression plate  10  is fixed to the base plate  13  by a compression-plate guide  14 . The under tray  11  is also mounted at the compression-plate guide  14 . The under tray  11  is used during a manipulation when the breast of the subject is inserted from the bed  1  such that the breast is arranged along the fixed compression plate  10  with ultrasonic gel or water applied to the breast. That is, the under tray  11  is a tray that prevents the ultrasonic gel or water from being dropped on the monitor camera  58  and the LED illumination device  59 . 
         [0081]    In  FIG. 12 , reference sign  25  denotes a compression-plate holder that supports the movable compression plate  12  by screwing. The compression-plate holder  25  is fixed to a linear guide  26  of a linear guide body  29  and slides along the linear guide body  29 . The linear guide body  29  allows a linear guide  28  to slide when a lead screw shaft  41  rotates. The linear guide  28  is fitted on the lead screw shaft  41  by a screw. In contrast, the linear guide  26  does not have inside thereof a fitting structure by a screw for the lead screw shaft  41 . The linear guide  28  is coupled with the linear guide  26  through a pressure sensor  27 . Accordingly, when the lead screw shaft  41  rotates, the linear guide  28  slides along the lead, and the linear guide  26  and the movable compression plate  12  also slide in the same direction. When the movable compression plate  12  slides to compress a breast or a breast phantom, a reactive force of the compression is generated at the movable compression plate  12 , and the pressure sensor  27  can measure the compression force. 
         [0082]    Reference sign  30  denotes a compression-plate one-side pressing lever that is fixed to a linear guide  32  and can slide on a linear guide body  35 . A compression-plate one-side pressing knob  31  is set for the movable compression plate  12 . The linear guide  32  does not have inside thereof a fitting structure by a screw for a lead screw shaft  36 . The linear guide  32  is coupled with a linear guide  34  through a pressure sensor  33 . When the lead screw shaft  36  rotates and the linear guide  34  slides relative to the linear guide body  35 , the linear guide  32 , the compression-plate one-side pressing lever  30 , the compression-plate one-side pressing knob  31 , and the movable compression plate  12  are pressed in a pressing direction through the pressure sensor  33 . 
         [0083]    The movable compression plate  12  is driven to slide by the linear guide bodies  29  and  35 . However, due to parallelism between the linear guide bodies  29  and  35  and eccentricities of the linear guide bodies  29  and  35 , if the movable compression plate  12  is fixed by the linear guide  26  and then is fixed by the linear guide  32 , the movable compression plate  12  may be excessively restrained, and sliding may become difficult. Owing to this, the compression-plate one-side pressing knob  31  only contacts the movable compression plate  12  in the compression direction and is not fixed to the movable compression plate  12 . 
         [0084]    Reference sign  37  denotes a phase adjustment plate. As shown in  FIG. 15 , the phase adjustment plate  37  includes a driving plate  37   a  and a driven plate  37   b . The driving plate  37   a  is integrally formed with a bevel gear  38  and is rotatably fitted on the lead screw shaft  36 . The driving plate  37   a  is coupled with the driven plate  37   b  by screws  37   g  and  37   f . Also, an eccentricity adjustment shaft  37   d  is rotatably coupled with the driving plate  37   a . An eccentric portion of the eccentricity adjustment shaft  37   d  is fitted to a long hole  37   e  of the driven plate  37   b . The driven plate  37   b  is fitted on the lead screw shaft  36  by a keyway. Since the driven plate  37   b  is coupled with the driving plate  37   a  by the screws  37   g  and  37   f , a driving force of the bevel gear  38  is transmitted to the lead screw shaft  36 . 
         [0085]    Bevel gears  39  and  43  are fitted on a rotation shaft  40  through keys. When a bevel gear  44  is driven to rotate, the bevel gears  39  and  43  rotate together with the rotation shaft  40 . 
         [0086]    Bevel gears  45  and  47  are fitted on a rotation shaft  46  through keys, and rotate together with the rotation shaft  46 . Bevel gears  48  and  50  are fitted on a rotation shaft  49  through keys, and rotate together with the rotation shaft  49 . 
         [0087]    Reference sign  51  denotes a bevel gear that is integrated with a rotation shaft  52  by a key. Reference sign  53  denotes a torque limiter. Reference sign  54  denotes a torque limiter with a coupling gear. These torque limiters slip with the same torque. This configuration is provided for safety in case of a breakdown during compression of a breast. Even if one of the torque limiters is broken and no longer slips, the other torque limiter can prevent excessive compression. The torque limiter  53  includes a friction spring between a rotor portion  53   b  into which the rotation shaft  52  is press-fitted and an outer portion  53   a  with which a rotation shaft  54   c  is coupled. If a rotating torque of the rotation shaft  54   c  exceeds a predetermined rotating torque, rotation is not transmitted from the outer portion  53   a  to the rotor portion  53   b . Hence, a torque exceeding the predetermined torque is not generated on the rotation shaft  52 . 
         [0088]    The torque limiter  54  with the coupling gear has the same structure as the torque limiter  53 . The torque limiter  54  includes a friction spring between a rotor portion  54   b  into which the rotation shaft  54   c  that is an output shaft is press-fitted and an outer portion  54   e  with which a rotation shaft  54   d  is coupled. If a rotating torque of the rotation shaft  54   d  exceeds a predetermined rotating torque, rotation is not transmitted from the outer portion  54   e  to the rotor portion  54   b . Hence, a torque exceeding the pre-determined torque is not generated on the rotation shaft  54   c.    
         [0089]    Also, a coupling gear portion  54   a  for transmission of electric driving is fixed to the rotation shaft  54   d  by press-fitting, and rotates together with the rotation shaft  54   d . During electric driving, since power is transmitted through the portion with the double torque limiters when the breast is compressed, even if an electric drive mechanism is broken and provides driving with a torque equal to or higher than a pre-determined torque, only compression by a predetermined degree or smaller can be provided. 
         [0090]    Reference sign  55  denotes a brake with a one-way mechanism, the brake including a bearing  55   d  fixed to the compression measurement unit  2 , and a stator  55   a  fixed to the bearing  55   d  by a screw or the like. An electromagnetic coil is provided in the stator  55   a . The electromagnetic coil is magnetized when the electromagnetic coil is energized. The electromagnetic coil attracts a brake rotor  55   b  and unitizes the brake rotor  55   b  with the stator  55   a . Accordingly, the brake works. The brake rotor  55   b  includes a one-way mechanism  55   c  and is coupled with a rotation shaft  55   e  through the one-way mechanism  55   c . When the brake rotor  55   b  is unitized with the stator  55   a  by the magnetization of the stator  55   a  and hence the brake works, the rotation shaft  55   e  is allowed to rotate in a release direction of the one-way mechanism  55   c  but is inhibited from rotating in a lock direction of the one-way mechanism  55   c . This explanation is for an operation when the state change switch  5  changes the state of rotation of the manual compression handle  4  to the one-way latch state. 
         [0091]    In particular, the manual compression handle  4  is rotatable when the manual compression handle  4  is rotated in the compression direction of the movable compression plate  12 , and the manual compression handle  4  is locked and non-rotatable when the manual compression handle  4  is rotated in the release direction of the movable compression plate  12 . 
         [0092]    As described above, since the rotation of the manual compression handle  4  is locked when the manual compression handle  4  is rotated in the release direction of the movable compression plate  12 , a reactive force when the movable compression plate  12  compresses a breast is not generated on the manual compression handle  4 . The operator does not have to always grip the manual compression handle  4  during compression, and the operation becomes easy. Also, when the state change switch  5  changes the state to the constantly direct-coupled state, the electromagnetic coil in the stator  55   a  is no longer energized, and magnetization is no longer provided. The brake rotor  55   b  is separated from the stator  55   a , and the one-way mechanism  55   c  no longer works. Accordingly, the manual compression handle  4  becomes freely rotatable in the compression direction and the release direction. 
         [0093]    Reference sign  56  denotes a universal joint that couples the rotation shaft  55   e  with a rotation shaft  57  of the manual compression handle  4  at an angle of about 30 degrees. The rotation shafts  52 ,  54   c ,  54   d , and  55   e  for compression and release are substantially linearly arranged from the far side toward the near side. By mounting the manual compression handle  4  with the inclination by the angle of about 30 degrees with respect to the manipulation opening  2   a  for a manipulation, the handle can be most easily operated for compression or release at that position during a manipulation. 
         [0094]    Phase adjustment is setting such that the movable compression plate  12  fixed to and supported by the linear guide  26  at a position determined by the lead screw shaft  41  of the linear guide body  29  contacts the compression-plate one-side pressing knob  31  at a position at which the movable compression plate  12  is located at a plane parallel to the fixed compression plate  10 . To set the compression-plate one-side pressing knob  31  at the contact position with respect to the movable compression plate  12 , the eccentricity adjustment shaft  37   d  is rotated while the screw  37   g  of the phase adjustment plate  37  is loosened, and simultaneously, a rotation phase of the lead screw shaft  36  is changed with respect to a phase of the bevel gear  38  determined by the bevel gears  39  and  43 . Hence, the linear guide  34  is finely adjusted by sliding with respect to the linear guide body  29  by a value of lead/rotation angle of the lead screw shaft  36 . Thus, the contact position of the compression-plate one-side pressing knob  31  with respect to the movable compression plate  12  is adjusted. 
         [0095]    In the acoustic-wave acquiring apparatus according to the embodiment of the present invention, the compression plate is supported by the two shafts, and such a fine adjustment mechanism is installed in view of the parallelism between the fixed compression plate  10  and the movable compression plate  12 . In X-ray mammography, a compression plate performs compression while being supported typically by a single member. The X-ray mammography provides a projection image obtained by measuring transmission of X-rays from the upper side of a compressed breast. The projection image is an image in a flat plane. Compression is performed to increase the transmittance for X-rays and minimize the amount of X-rays, thereby preventing the subject from being excessively exposed to X-rays. Also, compression is performed to expand the breast as possible and reduce an overlap in the projection image. As the result, the parallelism between the compression plates is not a serious matter, and hence the compression plates are frequently supported by the single shaft. 
         [0096]    In contrast, in the acoustic-wave acquiring apparatus according to the embodiment of the present invention, illumination is provided with laser light, an ultrasonic wave of hemoglobin in blood is measured, and a location of the hemoglobin is reconstructed by calculation, to determine the location of the ultrasonic wave in the three-dimensional space of the breast. In this case, if an acoustic-wave property of the ultrasonic wave of the breast is obtained, the calculation can be performed. However, an acoustic property of an ultrasonic wave of a human body varies in a complicated manner. It is difficult to measure the acoustic-wave property. In this situation, if the parallelism between the compression plates is very accurately set, the position of the ultrasonic wave generated from the hemoglobin can be figured out with reference to the compression plates. Even though the acoustic-wave property of the ultrasonic wave of the human body is uncertain, the level of cluster in blood, such as a cancer, can be calculated. Accordingly, in the acoustic-wave acquiring apparatus according to the embodiment of the present invention, the movable compression plate  12  is supported by the two shafts, and a countermeasure that adjusts the parallelism between the movable compression plate  12  and the fixed compression plate  10  is required. 
         [0097]      FIGS. 16 and 17  are illustrations showing the detail of the compression mechanism according to the embodiment of the present invention. In  FIG. 16 , reference sign  61  denotes a potentiometer. A hook portion  61   c  of the potentiometer  61  is fixed to the movable compression plate  12 , and the potentiometer  61  is coupled with the hook portion  61   c  by a wire  61   b  pulled from a body  61   a  of the potentiometer  61 . Accordingly, a compression moving distance of the movable compression plate  12  is calculated by using a length of the wire  61   b  pulled from the body  61   a .  FIG. 17  is a perspective view showing the detail of the one-side pressing portion of the movable compression plate  12 . The phase adjustment of the pressing portion of the movable compression plate  12  can be performed by the fine adjustment by the phase adjustment plate  37  as described above. Described below is an embodiment, in which an adjustment amount that cannot be provided by the fine adjustment is required. 
         [0098]    First, the pressing portion of the movable compression plate  12  slides by a lead fitting portion of a lead piece portion  34   b  of the linear guide  34  by rotating the lead screw shaft  36 . The pressing portion of the movable compression plate  12  is fixed to a mount  34   a  of the linear guide  34  by a mount portion  33   b  of the pressure sensor  33 . A mounting bolt  33   a  is mounted at the other end of the pressure sensor  33 . If a mount  32   a  fixed to a linear guide  32   b  that is not fitted on the lead screw shaft  36  through a lead is coupled with the other end of the mounting bolt  33   a  by a nut or the like, a slide driving force can be transmitted therebetween. Further, the compression-plate one-side pressing lever  30  is fixed to the lead piece portion  34   b  of the linear guide  34 . The compression-plate one-side pressing knob  31  is located at the other end of the compression-plate one-side pressing lever  30  and screwed into a screw tap portion  30   a.    
         [0099]    The compression-plate one-side pressing knob  31  presses the movable compression plate  12  in this state. Hence, by changing the screwing amount of the compression-plate one-side pressing knob  31  with respect to the compression-plate one-side pressing lever  30 , parallel pressing adjustment of the movable compression plate  12  can be performed similarly to when the driving phase of the lead screw shaft is changed. 
         [0100]    Also, the parallel pressing adjustment of the movable compression plate  12  can be performed similarly to when the driving phase of the lead screw shaft is changed, even if the position of the nut that mounts the mounting bolt  33   a  of the pressure sensor  33  onto the mount  32   a  is changed. However, since the target to be adjusted is a normal bolt or a normal screw portion, the parallel pressing adjustment of the movable compression plate  12  is adjustment by a large distance, but is not fine adjustment. Hence, a fine adjustment mechanism by the phase adjustment plate  37  is required. 
       Electric Drive Mechanism 
       [0101]    Next, an electric drive mechanism for compression is described.  FIGS. 18 to 21  are operation explanatory views of an electric compression mechanism according to the embodiment of the present invention. In  FIG. 18 , reference sign  70  denotes an electric drive motor that supplies power when the foot pedal  6  in  FIG. 1  is depressed and turned ON. When the pedal  6   b  is depressed and turned ON, a motor output shaft  71  rotates counterclockwise to provide driving in the compression direction. When the pedal  6   a  is depressed and turned ON, the motor output shaft  71  rotates clockwise to provide driving in the release direction. Reference sign  72  denotes a planetary-gear-change sun gear that is fitted on the motor output shaft  71  by a key and rotates together with the motor output shaft. 
         [0102]    Reference sign  73  denotes a planetary-gear change lever that is rotatably fitted on the motor output shaft  71 . A friction spring is provided between the planetary-gear change lever  73  and the sun gear  72 , and an urging force acts therebetween. Hence, the planetary-gear change lever  73  rotates in the same direction as that of the motor output shaft  71 . Reference sign  74  denotes a planetary gear rotatably fitted on a planetary gear shaft  75  that is fixed to the planetary-gear change lever  73  by press-fitting. The planetary gear shaft  75  fixed to the planetary-gear change lever  73  by press-fitting has a stopper pin  75   a  that protrudes further from the planetary-gear change lever  73  as shown in  FIG. 19 . The stopper pin  75   a  contacts a compression-driving planetary-gear stopper surface  76   a  and a release-driving planetary-gear stopper surface  76   b  of a planetary-gear change plate  76 , for positioning the planetary gear  74 . 
         [0103]    In  FIG. 19 , when the motor output shaft  71  rotates clockwise, the sun gear  72  rotates clockwise, and the planetary-gear change lever  73  also rotates clockwise. Then, the stopper pin  75   a  of the planetary gear shaft  75  contacts the compression-driving planetary-gear stopper surface  76   a  of the planetary-gear change plate  76  and the clockwise rotation of the planetary-gear change lever  73  is stopped. The position at which the clockwise rotation of the planetary-gear change lever  73  is stopped is a position at which the planetary gear  74  meshes with a gear  77 . Even when the stopper pin  75   a  contacts the compression-driving planetary-gear stopper surface  76   a  of the planetary-gear change plate  76  and the clockwise rotation of the planetary-gear change lever  73  is stopped, since the sun gear  72  slips by the friction spring (not shown), the sun gear  72  can transmit power that is reduced by a slipping torque of the friction spring. Thus, the rotation of the sun gear  72  is transmitted from the planetary gear  74  to the gear  77 , and a rotation shaft  78  that is fitted to the gear  77  by a key and rotated together with the gear  77  rotates clockwise. 
         [0104]    Reference sign  80  denotes a torque limiter that transmits the rotating torque of the rotation shaft  78  to a rotation shaft  81 . If the rotating torque of the rotation shaft  78  becomes a predetermined level or higher, the rotation shaft  78  rotates at idle. The torque limiter  80  limits an upper limit value of the rotating torque of the rotation shaft  81 . A gear  82  is fitted on the rotation shaft  81  by a key and rotates together with the rotation shaft  81 . The gear  82  constantly meshes with a gear  83 . The gear  83  is fitted on a rotation shaft  84  by a key and rotates together with the rotation shaft  84 . The rotation shaft  84  also rotates together with a clutch plate (not shown) provided in a clutch  85 . The clutch plate is electromagnetically attracted to an armature portion  86   a  of a clutch rotor  86  when the clutch  85  is energized, and the clutch plate becomes rotatable together with the armature portion  86   a . The clutch plate can transmit the rotating torque of the rotation shaft  84  to a sleeve gear  86   b  of the clutch rotor  86 . 
         [0105]    When application of electricity to the clutch rotor  86  is stopped, the electromagnetic attraction between the clutch plate coupled to the rotation shaft  84  and the armature portion  86   a  of the clutch rotor  86  is eliminated, and the rotating torque of the rotation shaft  84  is not transmitted to the clutch rotor  86 . The sleeve gear  86   b  of the clutch rotor  86  constantly meshes with the coupling gear portion  54   a  of the torque limiter  54  with the coupling gear. Hence, when the rotating torque of the electric drive motor  70  is transmitted to the clutch rotor  86 , the coupling gear portion  54   a  rotates, and electric compression driving is started. 
         [0106]    In  FIG. 20 , when the pedal  6   a  in  FIG. 1  is depressed and turned ON, the motor output shaft  71  of the electric drive motor  70  rotates clockwise for driving in the release direction. Then, the sun gear  72  rotates clockwise, and hence the planetary-gear change lever  73  rotates clockwise by the friction spring of the sun gear  72 . The stopper pin  75   a  of the planetary gear shaft  75  contacts the release-driving planetary-gear stopper surface  76   b  of the planetary-gear change plate  76 . This state is shown in  FIGS. 20 and 21 . 
         [0107]    When the stopper pin  75   a  contacts the release-driving planetary-gear stopper surface  76   b , the rotation of the sun gear  72  is transmitted to the planetary gear  74 , and the planetary gear  74  meshes with a gear  88 . When the stopper pin  75   a  contacts, the rotation of the planetary-gear change lever  73  stops such that the contact state of the stopper pin  75   a  is maintained while a clockwise rotating force from the friction spring of the sun gear  72  slips. The gear  88  is fitted on a rotation shaft  89  by a key and rotates together with the rotation shaft  89 . The rotation shaft  89  is also fitted to a gear  90  by a key. Hence, the rotating torque of the gear  88  is directly transmitted to the gear  90 . The gear  90  meshes with the gear  83  and the rotating torque of the gear  90  is transmitted to the clutch  85 . Transmission of the rotating torque to the clutch  85  and downstream portions is similar to transmission for the above-described compression driving. 
       Slide Mechanism 
       [0108]    Next, sliding is described. In  FIG. 14 , slide-rail receiving plates  63  are fastened to a frame  1   b  of the bed  1  by screws or the like. Slide rails  62  and  64  are mounted on the slide-rail receiving plates  63 . The base plate  13  is arranged on pieces  62   a ,  62   b , and  62   c  sliding on the slide rail  62  and pieces sliding on the slide rail  64 , and the base plate  13  is fastened to the pieces of the slide rails  62  and  64  by screws or the like. With this configuration, the base plate  13  can slide relative to the bed  1  along the slide rails  62  and  64 . Slide driving is made when the slide handle  3  is rotated. 
         [0109]    In  FIG. 14 , the slide handle  3  is directly coupled with a handle gear  67  through a rotation shaft included in a handle holder  66  and rotates together with the handle gear  67 . The handle gear  67  meshes with a reduction gear  68 . The reduction gear  68  meshes with a slide drive gear  69 . The reduction gear  68  and the slide drive gear  69  are rotatably supported on shafts fixed to the handle holder  66 . 
         [0110]    Further, the slide drive gear  69  meshes with a slide rack gear  65  fixed to the base plate  13 . Hence, in  FIG. 14 , when the slide handle  3  is rotated clockwise, the handle gear  67  also rotates clockwise, and the reduction gear  68  rotates counterclockwise. Since the slide drive gear  69  rotates clockwise, the slide drive gear  69  drives the slide rack gear  65  to slide rightward, and the base plate  13  also slides rightward. At least the fixed compression plate  10  is hung from the base plate  13 . Hence, this sliding direction corresponds to an under-breast pre-compression operation of an inserted breast (described later). 
         [0111]    Also, when the slide handle  3  is rotated counterclockwise, the base plate  13  slides leftward in a reverse direction, so that the under-breast pre-compression of the breast can be released. 
       Operation of Manual Mechanism 
       [0112]    Next, an operation of a manual mechanism is described. In  FIG. 12 , when the manual compression handle  4  is rotated counterclockwise, the movable compression plate  12  approaches the fixed compression plate  10 , thereby providing a compression operation. To be more specific, when the manual compression handle  4  is rotated counterclockwise, the rotation is transmitted to the rotation shaft  57  and reaches the brake  55  with the one-way mechanism through the universal joint  56 . The brake  55  with the one-way mechanism acts when the state change switch  5  in  FIG. 1  selects the one-way latch state. In contrast, when the manual compression handle  4  is rotated counterclockwise in the compression direction, since the rotation is in a free-rotation direction of the one-way mechanism, a rotation load is not generated, and the rotation is transmitted to the downstream torque limiter  54  with the coupling gear. 
         [0113]    The coupling gear portion  54   a  of the torque limiter  54  with the coupling gear constantly meshes with the sleeve gear  86   b  of the clutch  85 . However, when the foot pedal  6  in  FIG. 1  is not depressed, the clutch  85  in  FIG. 18  is not coupled with the coupling gear portion  54   a  or the electric drive motor  70 . Accordingly, a rotation load is not generated. If the rotating torque from the manual compression handle  4  at the input side exceeds 300 N when the rotating torque is converted into a pressing force for pressing the movable compression plate  12 , the torque limiter portion of the torque limiter  54  with the coupling gear controls the force generated at an input shaft of the torque limiter  53  at the output side so as not to exceed 300 N. 
         [0114]    Also, the torque limiter  53  serves as the same torque limiter as the torque limiter  54  with the coupling gear, and controls the output rotating torque with respect to the input rotating torque so as not to exceed 300 N when the rotating torque is converted into the pressing force for pressing the movable compression plate  12 . The double torque limiters are provided for a certification in case of a failure of a single torque limiter. Even if one of the torque limiters is broken, it can be certified that the rotating torque does not exceed 300 N when the rotating torque is converted into a pressing force for the movable compression plate  12 . Since the electric driving torque is transmitted from the coupling gear portion  54   a  during electric compression with the electric drive motor  70 , this safety mechanism also certifies a system such that the rotating torque does not exceed 300 N. 
         [0115]    The manual compression force transmitted to the rotation shaft  52  that is the output shaft of the torque limiter  53  is transmitted to the bevel gears  51  and  50  to change the direction. Then, the direction of the force is changed at the bevel gears  48  and  47  shown in  FIG. 13  in association with the rotation shaft  49  and is transmitted to the rotation shaft  46 . Then, the force is transmitted to the rotation shaft  40  from the bevel gears  45  and  44 . The two bevel gears  43  and  39  are fitted on the rotation shaft  40  by keys and rotate together with the rotation shaft  40 . Accordingly, the left and right linear guide bodies  29  and  35  of the movable compression plate  12  can be simultaneously driven. Also, when the movable compression plate  12  provides compression, the movable compression plate  12  can be constantly parallel to the fixed compression plate  10  regardless of the position of the breast. 
         [0116]    The rotating torque transmitted to a bevel gear  42  that meshes with the bevel gear  43  is transmitted to the lead screw shaft  41  that is fitted to the bevel gear  42  by a key and rotates together with the bevel gear  42 . The rotating torque generates a rightward moving force at the linear guide  28  that is fitted on the lead screw shaft  41  by a screw. Thus, a force for pressing rightward the linear guide  26  that is not fitted on the lead screw shaft  41  by a screw is generated through the pressure sensor  27  that measures the compression reactive force of the movable compression plate  12 . 
         [0117]    The compression-plate holder  25  of the movable compression plate  12  is rigidly directly mounted at the linear guide  26 . The parallelism between the movable compression plate  12  and the fixed compression plate  10  can be sufficiently satisfied even with only the support by the linear guide  26 . Owing to this, the rail portion of the linear guide body  29  also extends toward the fixed compression plate  10 . 
         [0118]    Meanwhile, the bevel gear  39  meshes with the bevel gear  38 , and is driven simultaneously with the bevel gear  42 , so that the movable compression plate  12  is pressed from the left and right sides. In this situation, it is very difficult to eliminate a gear phase shift between the bevel gears and to eliminate a phase difference between the lead screw shafts  41  and  36 . Thus, according to the embodiment of the present invention, the phase adjustment plate  37  is provided. The phase adjustment plate  37  adjusts the phases such that the phase of the lead screw shaft  41  is fixed as a certified value because the fixed portion of the compression plate at the left side is provided and the phase of the lead screw shaft  36  is variable. That is, the phase adjustment plate  37  is provided on the shaft of the bevel gear  38  that meshes with the bevel gear  39 . The position after the phase adjustment is transmitted to the lead screw shaft  36 , so that the linear guide  34  that is fitted on the lead screw shaft  36  by a screw is driven in the compression direction. 
         [0119]    The pressure sensor  33  is mounted on the linear guide  34 . The linear guide  32  that is not fitted on the lead screw shaft  36  by a screw is pressed in the compression direction through the pressure sensor  33 . When a breast is compressed, the breast has to be supported by a manipulation at a position of the linear guide body  35  near the compression plate. If the linear guide body  35  extends to the position of the fixed compression plate  10  like the left linear guide body  29 , the linear guide body  35  may disturb the manipulation. It has been found through an experiment that the linear guide body  35  does not disturb the manipulation as long as the linear guide body  35  extends by a length to the same plane as a plane containing a maximum opening position of the movable compression plate  12  shown in  FIG. 12 . 
         [0120]    Hence, if the linear guide body  35  extends to the maximum opening position of the movable compression plate  12 , in order to press the movable compression plate  12  to a position near the fixed compression plate  10  at the position of the linear guide  34  or  32 , the compression-plate one-side pressing lever  30  with an overhang shape is required. Also, when the movable compression plate  12  moves substantially in parallel to the fixed compression plate  10  for compression, the linear guide bodies  29  and  35  guide the movable compression plate  12 . However, if the movable compression plate  12  is rigidly supported by the linear guide bodies  29  and  35 , the movable compression plate  12  may be excessively restrained. That is, a load on the linear guides  26  and  28  or a load on the linear guides  32  and  34  may become very large. Hence, the support at the linear guide body  35  by supporting with the overhang shape only receives the compression reactive force that is generated when the movable compression plate  12  compresses the breast. 
         [0121]    Accordingly, the linear guide body  35  of the movable compression plate  12  extends to the opening for the manipulation so as not to disturb the manipulation. Since the compression-plate one-side pressing lever  30  has an overhang shape, the compression plate can be driven along the two shafts. The parallelism with respect to the fixed compression plate  10  can be precisely maintained. 
       Operation of Electric Mechanism 
       [0122]    Next, an operation of an electric mechanism is described. The electric compression mechanism is activated only when the foot pedal  6  in  FIG. 1  is depressed. When the pedal  6   b  for driving in the compression direction of the foot pedal  6  in  FIG. 1  is depressed, the electric drive motor  70  in  FIG. 18  is energized to rotate counterclockwise, and the clutch  85  is also energized. Accordingly, the torque of the electric drive motor can be transmitted to the torque limiter  54  with the coupling gear. The electric torque is transmitted from the sun gear  72  to the gear  77  through the planetary gear  74 , and is input from the planetary gear shaft  75  to the torque limiter  80 . 
         [0123]    The torque limiter  80  performs torque limitation in a manner different from those of the double torque limiters  54  and  53  provided in the manual compression mechanism. The electric compression and the manual compression are provided in X-ray mammography. A compression force of the electric compression is relatively small. Japan Industrial Standard (JIS) defines that the electric compression is used in an auxiliary manner. Owing to this, similarly in the mechanism according to the embodiment of the present invention, the compression force of the electric compression is relatively smaller than that of the manual compression. The electric compression force at the torque limiter  80  is set as about 70 N. Even if the electric drive motor is broken, a force with 70 N or larger slips and is not transmitted to the movable compression plate  12 . 
         [0124]    Regarding a certification for the electric compression mechanism in case of a failure of a single torque limiter, if the torque limiter  80  is broken, is directly coupled, and no longer provides the torque limitation, the torque is transmitted from the gear  82 , the gear  83 , the clutch  85 , the sleeve gear  86   b , and then to the coupling gear portion  54   a , and is limited by the manual torque limiter with the limitation of 300 N. Thus, safety is certified. 
         [0125]    If a compression force with 70 N or larger is generated during electric driving, an emergency stop button (not shown) is pressed, so that application of electricity to the electric drive motor is stopped. Also, application of electricity to the clutch  85  is stopped, so that the torque of the electric drive motor  70  is no longer transmitted to the sleeve gear  86   b . Safety can be sufficiently assured. 
         [0126]    Also, when the pedal  6   b  is depressed and the manual compression is further performed during the compression in the electric compression mode, if the coupling gear portion  54   a  is manually rotated counterclockwise in the gear coupling state shown in  FIG. 18  faster than the electric compression, the sleeve gear  86   b  and the gear  83  rotate clockwise, and the coupled gear  82  rotates counterclockwise. Then, the torque limiter  80  and the gear  77  also rotate counterclockwise. When the gear  77  rotates counterclockwise, the planetary gear  74  repels the rotation, and a load on the manual compression handle  4  is not increased. In addition to driving in the electric compression direction, even if the pedal  6   a  for driving in the release direction of the foot pedal  6  is depressed and the movable compression plate  12  is electrically driven in the release direction, additional release driving can be provided by the manual compression handle. This configuration is described with reference to  FIG. 20 . 
         [0127]      FIG. 20  illustrates a state in which the pedal  6   a  for driving in the release direction is depressed and hence electric release driving is provided. In this driving state, in order to move the manual compression handle  4  in the release direction of the movable compression plate  12 , the manual compression handle  4  is rotated clockwise. Accordingly, the coupling gear portion  54   a  rotates clockwise, and the sleeve gear  86   b  and the gear  83  rotate counterclockwise. Further, the gear  90  and the gear  88  rotate clockwise. When the gear  88  rotates clockwise, similarly to the situation in which the additional manual rotation is made during compression, the planetary gear  74  repels the rotation, and the clockwise additional rotation of the gear  88  does not affect the electric drive motor  70 . 
         [0128]    Hence, even when the pedal  6   a  for driving in the release direction is depressed and the electric release operation is carried out, the additional release driving by the manual compression handle  4  does not receive a load. If the subject feels discomfort or an abnormal situation occurs during measurement by the acoustic-wave acquiring apparatus, the release operation may be late only by electric release driving. Therefore, the option of additional manual release to increase the speed of the release operation during the electric release is required in view of safety. 
       Emergency Compression Release Mechanism 
       [0129]    Next, an emergency release mechanism for compression is described.  FIG. 24  is a perspective view showing an emergency release mechanism according to the embodiment of the present invention.  FIGS. 25 to 30  are operation diagrams explaining operations of the emergency release mechanism for compression according to the embodiment of the present invention. 
         [0130]    In  FIG. 24 , reference sign  91  denotes a compression-plate stopper mounted on the compression-plate holder  25 . When the movable compression plate  12  is manually or electrically moved in the compression direction, if a breast or a breast phantom  9  is not set, the movable compression plate  12  may contact the compression-plate guide  14  of the fixed compression plate  10 . Hence, a rubber stopper may be provided to prevent a finger or the like from being pinched and injured or the compression plate from being damaged. 
         [0131]    Reference sign  92  denotes an emergency release lever that forcedly retracts the movable compression plate  12  in the release direction. A fitting portion  92   c  is slidably fitted to a fitting hole  14   a  provided in the compression plate guide  14 , and a tension spring  93  is hooked at a spring hook portion  92   a . The tension spring  93  is stretched between the hole  14   a  of the compression-plate guide  14  and a spring hook portion  93   b . Hence, the emergency release lever  92  is constantly urged in a direction in which the compression-plate holder  25  is released. Also, a stopper portion  92   b  is provided. When a restraint lever  95  at a cut portion  92   e  slides and restraint is released, the stopper portion  92   b  is stopped at a flat portion  95   f  of the restraint lever  95  or an area around the fitting hole  14   a  of the compression-plate guide  14 . 
         [0132]    Reference sign  94  denotes an electromagnetic attraction magnet that is an electromagnet that can attract an attraction surface  95   a  of the restraint lever  95  against a spring force of a tension spring  96 . The electromagnetic attraction magnet  94  is constantly energized when the apparatus is in operation, and continuously attracts the restraint lever  95 . If the emergency stop button (not shown) is pressed or an abnormal situation such as a power failure or other error occurs, application of electricity is stopped, so that the restraint lever  95  is released. 
         [0133]    Reference sign  95  denotes the restraint lever. The restraint lever  95  is mounted such that positioning pins  14   c  and  14   d  provided at the compression-plate guide  14  can vertically slide relative to long holes  95   c  and  95   d . A hook portion  96   a  of the tension spring  96  is hooked at a spring hook portion  95   b . The tension spring  96  is urged between the spring hook portion  95   b  and a spring hook pin portion  14   f  of the compression-plate guide  14 . When the attraction of the electromagnetic attraction magnet  94  is released, the spring hook portion  95   b  slides downward by an urging force of the tension spring  96 , and stops when contacting a stopper pin  14   e.    
         [0134]    An operation of the emergency release mechanism for compression with the above-described configuration is described.  FIG. 25  is an illustration of a standby state like  FIG. 24 . In  FIG. 25 , a distal end portion  95   e  of the restraint lever  95  enters the cut portion  92   e  of the emergency release lever  92  urged rightward by the tension spring  93 . Hence, this state is a preparation completed state for emergency release. An attraction portion  94   a  of the electromagnetic attraction magnet  94  attracts the attraction surface  95   a  of the restraint lever  95 . 
         [0135]      FIG. 26  is an illustration showing a state in which the breast phantom  9  is compressed. The emergency release mechanism holds the preparation completed state.  FIG. 27  illustrates a state immediately after the emergency release mechanism starts an operation because the emergency stop button (not shown) is depressed or an abnormal situation such as a power failure or other error occurs when the breast or the breast phantom is compressed. First, application of electricity to the electromagnetic attraction magnet  94  is stopped. The restraint lever  95  moves downward by the tension spring  96 . Then, the spring hook portion  95   b  contacts the stopper pin  14   e  and is stopped. In this state, since the emergency release lever  92  is not moved yet, emergency release for compression is not executed. 
         [0136]      FIG. 28  is an illustration showing a state next to the state in  FIG. 27 . First, the emergency release lever  92  moves rightward along the fitting hole  14   a  by the tension spring  93 . Then, a distal end portion  92   d  of the emergency release lever  92  presses the compression-plate holder  25 , and hence a large gap is made between the breast phantom and the movable compression plate  12 . The retraction amount of the movable compression plate  12  is determined such that the stopper portion  92   b  of the emergency release lever  92  is stopped at the flat portion  95   f  of the restraint lever  95  or the area around the fitting hole  14   a  of the compression-plate guide  14 . In  FIG. 28 , the stopper portion  92   b  is stopped at the flat portion  95   f  of the restraint lever  95 . 
         [0137]    In  FIG. 28 , the gap is widened by the emergency release lever  92  by a width sufficient for removing the breast phantom  9 . However, the configuration is not limited to the embodiment. When the emergency release lever  92  performs the release, as shown in  FIG. 25 , the movable compression plate  12  may be released to a full-open state that is an initial position of the movable compression plate  12 . Also, since the strong tension spring  93  causes the emergency release lever  92  to rapidly contact the compression-plate holder  25  for the emergency release, a large sound may be generated. Hence, a sound absorber like a rubber sheet may be provided at the distal end portion  92   d  of the emergency release lever  92 . Alternatively, a rubber sheet may be bonded to a surface of the compression-plate holder that contacts the emergency release lever  92 . Accordingly, anxiety of the subject can be eliminated. 
         [0138]    If the movable compression plate  12  is driven by the electric drive motor  70  or is manually driven by the manual compression handle  4  in the one-way latch state while the brake  55  with the one-way mechanism is activated, even though the emergency release lever  92  rapidly contacts the compression-plate holder  25  by the strong tension spring  93 , the emergency release cannot be carried out. If the emergency stop button (not shown) is pressed or an abnormal situation such as a power failure or other error occurs, application of electricity to the brake  55  with the one-way mechanism is stopped, and application of electricity to the clutch  85  is also stopped. Accordingly, the movable compression plate  12  or the compression-plate holder can be retracted by a small force. 
         [0139]    As shown in  FIG. 28 , if the emergency release mechanism is used once, in a case in which a similar situation occurs, the emergency release mechanism may no longer work in the state shown in  FIG. 28 . Hence, a reset operation of the emergency release mechanism is illustrated in  FIG. 29 . In  FIG. 29 , the operation starts from a state in which the breast, the breast phantom, or the like, is removed by the compression release operation after the emergency stop. 
         [0140]    In  FIG. 29 , the operation starts from a state in which a trouble of the apparatus is eliminated, power is supplied again, and the apparatus is in a normal state. First, through system check of the apparatus, it is found that the compression-plate holder is forcedly retracted by the emergency release. Hence, the reset operation is started. First, the clutch is energized so that the electric drive motor  70  is activated and the movable compression plate  12  is driven in the compression direction. Since the potentiometer  61  is provided at the movable compression plate  12 , the position of the movable compression plate  12  is immediately determined Electric driving is started from that position, and electric compression is performed without stopping until a distal end portion  91   a  of the compression-plate stopper  91  in  FIG. 29  contacts the compression-plate guide. 
         [0141]    An electric compression driving force at this time is provided up to a compression force of about 70 N under the control of the torque limiter  80 . In contrast, the emergency release operation can be performed by about 50 N because an urging force is eliminated. The tension spring  93  can be properly electrically driven although the torque limiter  80  is provided.  FIG. 29  is a state in which the reset operation is completed by the electric compression driving. The compression by electric driving is stopped when the compression-plate holder  25  presses the distal end portion  92   d  of the emergency release lever  92  leftward and the compression-plate stopper  91  contacts the compression-plate guide  14 . 
         [0142]    In the state in  FIG. 29 , when the electromagnetic attraction magnet  94  is energized and the restraint lever  95  is attracted, the distal end portion  95   e  of the restraint lever  95  enters the cut portion  92   e  of the emergency release lever  92 . Hence, the emergency release lever  92  can be brought into the preparation completed state.  FIG. 30  illustrates a state in which the electromagnetic attraction magnet  94  is energized and the restraint lever  95  is continuously attracted.  FIG. 30  illustrates a state in which reverse driving of the electric drive motor  70  is performed, the compression-plate holder  25  is slightly moved toward the release position, and the emergency release lever  92  is brought into the preparation completed state by the restraint lever  95 . From the state in  FIG. 30 , the electric drive motor  70  is driven in the release direction. Application of electricity is stopped when the movable compression plate  12  becomes full open, and the reset operation of the emergency release mechanism is completed. 
       Monitor Camera and Illumination Device 
       [0143]    Next, a monitor camera and an illumination device that assist compression according to the embodiment of the present invention are described.  FIGS. 12 and 31  are illustrations showing features of the monitor cameras  58  and  60 , and the LED illumination device  59 . In  FIGS. 12 and 31 , reference sign  58  denotes the monitor camera for observation from directly below the breast during compression. The monitor camera  58  is arranged at a position near the fixed compression plate  10 . As shown in  FIG. 31 , the position of the monitor camera  58  is substantially at the center of the fixed compression plate. 
         [0144]    The monitor camera  58  is a camera for mainly viewing an angle between the subject and the compression plate during MLO measurement. The inventor of the present invention found that there is an inclination angle of the subject with respect to the compression plate at which it is difficult to perform compression in the MLO direction, in a plane parallel to the surface of the bed, through an experiment. Then, the inventor ensured that the compression can be properly performed by aligning the breast with an angle defined by a line formed of a connection position of the breast with a breast muscle at the shoulder side and a line formed of a connection position of the breast with an abdominal muscle at the abdominal portion side. However, the angle (the angle defined by the line formed of the connection position of the breast with the breast muscle at the shoulder side and the line formed of the connection position of the breast with the abdominal muscle at the abdominal portion side) varies among individuals. The angle cannot be determined in an erect position. Thus, according to the embodiment of the present invention, the monitor camera  58  that captures an image of a breast is provided at a position that is below the compression plates and is opposite to the breast insertion hole. 
         [0145]    With the monitor camera  58 , a state of a shape of the breast can be observed from the lower side (side opposite to the breast insertion hole) while the base plate  13  slides. In the state in which the fixed compression plate contacts the breast, as shown in a right section of  FIG. 33A , if the shape of a distal end portion of the breast (crescentic shape in  FIGS. 33A and 33B ) viewed from the lower side is substantially parallel to the movable compression plate, it is determined that compression can be properly performed, and hence the movable compression plate is moved. In the state in which the fixed compression plate contacts the breast, as shown in a left section of  FIG. 33A , if the shape of the distal end portion of the breast viewed from the lower side is inclined with respect to the movable compression plate, it is determined that compression cannot be properly performed. In this case, a relative angle between the subject and the compression plate can be changed.  FIG. 33B  is a schematic illustration showing the angle defined by the subject and the compression plate in the state of  FIG. 33A . By observing the state of the breast shape of the subject from the lower side during measurement in the MLO direction, the number of times that compression is retried is reduced and pain of the subject during compression is reduced. 
         [0146]    Also, in a case of an apparatus that a manipulation is performed from a lateral side of the subject portion like the acoustic-wave acquiring apparatus according to the embodiment of the present invention, the monitor camera  60  for observation through the compression plate can be provided. Since the monitor camera  60  observes the breast, the monitor camera  60  assists the manipulation when the compressed state of the breast cannot be sufficiently determined from the manipulation side. Accordingly, the number of failures of compression is markedly reduced. The monitor camera  60  may be provided at either one or both of the movable compression plate and the fixed compression plate. If the monitor camera  60  is provided at the fixed compression plate, the positional relationship between the camera and the compression plate can be constantly fixed. If the positional relationship between the camera and the compression plate is fixed, the relationship between an actual size of the breast and an apparent size of the breast displayed on a monitor (display device) is constantly fixed. In contrast, if the camera is provided at the movable compression plate, the positional relationship between the camera and the compression plate has to be calculated and a scale of an image displayed on the monitor has to be changed. However, since the probe etc. is not arranged at the movable compression plate, the apparatus structure can be simple. 
         [0147]    Also, according to the embodiment of the present invention, the LED illumination device  59  that irradiates the subject portion from a lower side opposite to the breast insertion hole with light is provided. The LED illumination device  59  provides illumination that allows the monitor cameras  58  and  60  to easily perform image-capturing, and the illumination is not obstructed by a hand during a manipulation. Hence, the captured image of the breast can be easily viewed on the monitor. Also, the illumination position of the LED illumination device  59  is not located at the center of the fixed compression plate  10  unlike the monitor camera  58 , but is shifted to the left side with respect to the center (a side opposite to the manipulation opening). As shown in  FIGS. 4 and 5 , the side opposite to the manipulation opening is the foot side of the subject. That is, in  FIG. 31 , the left side of any of the left and right breasts is located at the foot side during compression in the MLO direction. This is because, during compression of the breast in the MLO direction, the nipple of the breast is not arranged at the center unlike the position during compression in the CC direction, but is shifted to the foot side. 
         [0148]    Hence, with regard to the monitor camera  58 , a center axis  59   a  of the LED illumination device  59  is shifted to the left side (the side opposite to the manipulation opening) with respect to a center axis  58   a  of the monitor camera  58 , so that a shade hardly appears in the illumination. In any embodiment of the present invention, the illumination device does not have to be a LED, and may be an incandescent lamp, a fluorescent lamp, or the like. 
         [0149]    Second monitor cameras and second illumination devices according to an embodiment of the present invention are described with reference to  FIGS. 34 and 35 . 
         [0150]    LED illumination devices  59  emit illumination light from positions below the fixed compression plate  10  and the movable compression plate  12  to obliquely upper sides. With this illumination, a shade hardly appears near the breast. If monitor cameras  60  are arranged with the fixed compression plate  10  and the movable compression plate  12  interposed between the monitor cameras  60 , image-capturing can be performed without the illumination light serving as backlight. 
         [0151]    A tray  14  includes a bottom surface, a side surface arranged below the fixed compression plate  10  (a side surface extending from a position of the fixed compression plate opposite to the breast insertion hole), and a side surface arranged below the movable compression plate  12  (a side surface extending from a position of the movable compression plate opposite to the breast insertion hole). That is, the bottom surface of the tray  14  connects the side surfaces with each other. Further, the tray  14  may include a side surface at a position opposite to the manipulation opening. With this configuration, water, ultrasonic gel, or the like, used during a manipulation is prevented from being scattered into the apparatus. The tray  14  is formed of a transparent or semitransparent member that can transmit the illumination light so that irradiation with the light can be provided from the illumination devices  59  through the side surfaces (surfaces A and B) of the tray  14 . With this configuration, it can be determined whether the breast is properly held or not during the manipulation. A proper image can be acquired. 
         [0152]    Also, in order to correctly determine whether the breast is properly held or not, the breast can be irradiated with the illumination light uniformly without the light quantity of illumination light unevenly distributed. If surfaces A, B, and C of the tray  14  are formed of diffusion surfaces, unevenness of the light quantity distribution is reduced, and correct determination can be made. 
       Flowcharts Showing Measurement Sequences of Acoustic-Wave Acquiring Apparatus 
       [0153]    Next, an operation of the acoustic-wave acquiring apparatus is described as an example of a measurement apparatus according to the embodiment of the present invention.  FIGS. 22A ,  22 B,  23 A, and  23 B are flowcharts showing measurement sequences of the acoustic-wave acquiring apparatus.  FIGS. 22A and 22B  illustrate measurement during compression in the CC direction. 
         [0154]    First, the sequence starts from step S 101 . In step S 102 , the subject takes the prone position on the bed, and inserts a breast to be measured into the hole  1   a  of the bed  1 . In step S 103 , the state change switch  5  changes the state of the compression mechanism to the one-way latch state. 
         [0155]    In step S 104 , when the breast of the subject is sufficiently pulled toward the compression measurement unit  2  by a manipulation, the breast is arranged to sufficiently extend along the fixed compression plate  10  through the manipulation, and the sequence goes to step S 105 . In step S 105 , the slide handle  3  is rotated, so that the compression measurement unit  2  slides relative to the bed  1 . This sliding provides pre-compression on the breast of the subject from a Cb direction when the breast is at the C position in  FIG. 3 . That is, when the subject takes the position as shown in  FIG. 6 , the fixed compression plate  10  is pressed to the breast from the foot side. Accordingly, the under-breast of the breast is fixed, and pre-compression corresponding to one-third to half of full compression is completed. 
         [0156]    When the slide handle  3  is rotated counterclockwise in  FIG. 14 , since the gear  67  is fixed to the shaft of the slide handle  3 , the gear  67  rotates counterclockwise similarly, and the rotation is transmitted from the reduction gear  68  to the gear  69 . Since the slide rack gear  65  fixed to the base plate  13  meshes with the gear  69 , the counterclockwise rotation of the gear  69  causes the slide rack gear  65  to move from the foot side to the head side together with the base plate  13  (step S 106 ). When the pre-compression is completed, the sequence goes to step S 107 , in which the pedal  6   b  is depressed to start electric compression. Then, the movable compression plate  12  gradually moves in the compression direction. In step S 108 , the compressed state of the breast is adjusted by a manipulation. 
         [0157]    In step S 109 , the pedal  6   b  is released to end the electric compression while the hand for the manipulation is removed from the breast. In step S 110 , the manual compression handle  4  is rotated counterclockwise for manual compression. This manual compression handle  4  is carefully operated while the operator asks the subject whether the subject feels pain or not in step S 111 . If the subject feels pain, the sequence goes to step S 119 , in which the manual compression handle  4  is operated clockwise in the release direction of compression, and removes the pain. Then, the sequence goes back to step S 110  in which compression is continued from the state without pain. 
         [0158]    If an abnormal situation occurs in step S 112 , the sequence immediately goes to step S 120 , in which the emergency stop switch (not shown) is turned ON. Then, the system recognizes the abnormal situation, automatically performs steps S 121  to S 123 , that is, the system releases the one-way break at step S 121  and activates a forced release of the compression at step S 122 , so that the compression is automatically released in step S 123  by performing electric release driving. Thus, the measurement is stopped. If the abnormal situation does not occur in step S 112 , an image of the monitor camera  60  that captures the image of the breast from the head side of the movable compression plate  12  is observed through a monitor (not shown) and the compressed state of the breast is checked in step S 113 . When the monitor camera  60  captures the image of the breast from the head side of the movable compression plate  12 , since the LED illumination device  59  provided directly below the fixed compression plate  10  illuminates the breast, the breast can be entirely illuminated. 
         [0159]    In step S 114 , it is judged whether the compression position is OK (proper) or NG (not proper), and if OK, the sequence goes to step S 115 , in which a photoultrasonic wave is measured by a predetermined procedure. When the measurement of the photoacoustic wave is ended, to release the breast, the state change switch  5  changes the state to the constantly direct-coupled state in step S 116 . Then, the brake  55  with the one-way mechanism is no longer energized, and release restriction of the movable compression plate  12  is released (release compression). Accordingly, the movable compression plate  12  is slightly retracted by an elastic force of the breast, and the pain of the breast of the subject is reduced. In step S 117 , the manual compression handle  4  can be rotated clockwise to retract the movable compression plate  12 . 
         [0160]    Also, the system can recognize that the state change switch  5  changes the state to the constantly direct-coupled state in step S 116 . When the measurement is ended, the electric drive motor can be rotated clockwise in step S 117 , and the compression of the movable compression plate  12  can be forcedly released. 
         [0161]    In contrast, if the compression position of the breast is NG (not good) in step S 114 , for example, if the breast is not sufficiently pulled, the measurement cannot be performed. Hence, the sequence goes to step S 124 , in which the state change switch  5  changes the state to the constantly direct-coupled state, the manual compression handle  4  is rotated clockwise to release the compression in step S 125 , the breast of the subject is removed once in step S 126 , and the sequence is performed again from step S 102 . 
         [0162]      FIGS. 23A and 23B  illustrate measurement during compression in the MLO direction. First, the sequence starts from step S 201 . In step S 202 , the subject takes the prone position on the bed, and inserts a breast to be measured into the hole  1   a  of the bed  1 . When the subject takes the prone position, the angle in the MLO direction has to be instructed unlike the measurement in the CC direction. In step S 203 , the state change switch  5  changes the state of the compression mechanism to the one-way latch state. 
         [0163]    In step S 204 , when the breast of the subject is sufficiently pulled toward the compression measurement unit  2  by a manipulation, the breast is arranged to sufficiently extend along the fixed compression plate  10  through the manipulation, and the sequence goes to step S 205 . In step S 205 , the slide handle  3  is rotated, so that the compression measurement unit  2  slides relative to the bed  1 . In case of the right breast, the subject takes the position in  FIG. 4 , and this sliding provides pre-compression on the breast from the Ab direction at the A position in  FIG. 3 . In case of the left breast, the subject takes the position in  FIG. 5 , and this sliding provides pre-compression on the breast from the Bb direction at the B position in  FIG. 3 . 
         [0164]    The pre-compression is similar to that in the CC direction. When the slide handle  3  is rotated counterclockwise in  FIG. 14 , since the gear  67  is fixed to the shaft of the slide handle  3 , the gear  67  rotates counterclockwise similarly, and the rotation is transmitted from the reduction gear  68  to the gear  69 . Since the slide rack gear  65  fixed to the base plate  13  meshes with the gear  69 , the counterclockwise rotation of the gear  69  causes the slide rack gear  65  to move from the foot side to the head side together with the base plate  13  (step S 206 ). When the pre-compression is completed, the sequence goes to step S 207 , in which the pedal  6   b  is depressed to start electric compression. Then, the movable compression plate  12  gradually moves in the compression direction. The compressed state of the breast is adjusted by a manipulation in step S 208 . 
         [0165]    In step S 209 , by using the monitor cameras  58  and  60  provided directly below the compression mechanism and by providing illumination with the LED illumination device  59 , the compressed state of the breast is viewed through the monitor (not shown). In step S 210 , in particular, the monitor camera  58  directly below the compression plate checks whether the angles Ab and Bb in the MLO direction of the breast of the subject in  FIG. 3  are OK (proper) or NG (not proper). If the angle is NG, the compressed state is insufficient. 
         [0166]    In step S 210 , if the angle in the MLO direction is OK, the sequence goes to step S 211 , in which the pedal  6   b  is released to end the electric compression. In step S 212 , the manual compression handle  4  is rotated counterclockwise for manual compression. This manual compression handle  4  is carefully operated while the operator asks the subject whether the subject feels pain or not in step S 213 . If the subject feels pain, the sequence goes to step S 221 , in which the manual compression handle  4  is operated clockwise in the release direction of compression, and removes the pain. Then, the sequence goes back to step S 212  in which compression is continued from the state without pain. If an abnormal situation occurs in step S 214 , the sequence immediately goes to step S 222 , in which the emergency stop switch (not shown) is turned ON. Then, the system recognizes the abnormal situation, automatically performs steps S 223  to S 225 , that is, the system releases the one-way break at step S 223  and activates a forced release of the compression at step S 224 , so that the compression is automatically released in step S 225  by performing electric release driving. Thus, the measurement is stopped. 
         [0167]    If an abnormal situation does not occur in step S 214 , measurement is continued, and an image of the monitor camera  60  that captures the image of the breast from the head side with respect to the movable compression plate  12  is observed through the monitor (not shown) and the compressed state of the breast is checked in step S 215 . When the monitor camera  60  captures the image of the breast from the head side of the movable compression plate  12 , since the LED illumination device  59  provided directly below the fixed compression plate  10  illuminates the breast, the breast can be entirely illuminated. If the compression position is OK in step S 216 , the sequence goes to step S 217 , in which a photoultrasonic wave is measured by a predetermined procedure. 
         [0168]    When the measurement of the photoacoustic wave is ended, to release the breast, the state change switch  5  changes the state to the constantly direct-coupled state in step S 218 . Then, the brake  55  with the one-way mechanism is no longer energized, and release restriction of the movable compression plate  12  is released. Accordingly, the movable compression plate  12  is slightly retracted by an elastic force of the breast, and the pain of the breast of the subject is reduced. In step S 219 , the manual compression handle  4  can be easily rotated clockwise to retract the movable compression plate  12 . 
         [0169]    Also, the system can recognize that the state change switch  5  changes the state to the constantly direct-coupled state in step S 218 . When the measurement is ended, the electric drive motor can be rotated clockwise in step S 219 , and the compression of the movable compression plate  12  can be forcedly released. 
         [0170]    In contrast, if the compression position of the breast is NG in step S 216 , for example, if the breast is not sufficiently pulled, the measurement cannot be performed. Hence, the sequence goes to step S 227 , in which the state change switch  5  changes the state to the constantly direct-coupled state, the manual compression handle  4  is rotated clockwise to release the compression in step S 228 , the breast of the subject is removed once in step S 229 , and the sequence is performed again from step S 202 . 
         [0171]    If the angle in the MLO direction is NG in step S 210 , the compression may not be sufficient. The angle in which the breast is inserted is changed by rotation around the hole  1   a  of the bed when the subject takes the prone position, and the compression is performed again. The sequence goes to step S 226 , in which the pedal  6   b  is released to stop the electric compression. Next, the sequence goes to step S 227 , in which the state change switch  5  changes the state to the constantly direct-coupled state. Then, in step S 228 , the manual compression handle  4  is rotated clockwise and the compression is released. In step S 229 , the breast of the subject is removed once, and in step S 202 , the sequence is performed again from the beginning. 
         [0172]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
         [0173]    This application claims the benefit of Japanese Patent Application No. 2010-265750, filed Nov. 29, 2010 and No. 2011-231006 filed Oct. 20, 2011, which are hereby incorporated by reference herein in their entirety. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               1  Bed 
               2  Compression measurement unit 
               3  Slide handle 
               4  Manual compression handle 
               5  State change switch 
               6  Foot pedal 
               7  MLO receiving plate 
               8  CC receiving plate 
               9  Breast phantom 
               10  Fixed compression plate 
               11  Under tray 
               12  Movable compression plate 
               13  Base plate 
               14  Compression-plate guide 
               15  Ultrasonic probe 
               16  Probe cable 
               17  Carriage 
               18  Probe Y-axis drive guide 
               19  Probe X-axis drive guide 
               20  Laser illumination optical system 
               21  Fiber cable 
               22  Phototransmitter carriage 
               23  Phototransmitter Y-axis drive guide 
               24  Phototransmitter X-axis drive guide 
               25  Compression-plate holder 
               26 ,  28 ,  32 ,  34  Linear guide 
               27 ,  33  Pressure sensor 
               29 ,  35  Linear guide body 
               30  Compression-plate one-side pressing lever 
               31  Compression-plate one-side pressing knob 
               36 ,  41  Lead screw shaft 
               37  Phase adjustment plate 
               38 ,  39 ,  42 ,  43 ,  44 ,  45 ,  47 ,  48 ,  50 ,  51  Bevel gear 
               40 ,  46 ,  49 ,  52 ,  57  Rotation shaft 
               53  Torque limiter 
               54  Torque limiter with coupling gear 
               55  Brake with one-way mechanism 
               56  Universal joint 
               58 ,  60  Monitor camera 
               59  LED illumination device 
               61  Potentiometer 
               62 ,  64  Slide rail 
               63  Slide-rail receiving plate 
               65  Slide rack gear 
               66  Handle holder 
               67  Handle gear 
               68  Reduction gear 
               69  Slide drive gear 
               70  Electric drive motor 
               71  Motor output shaft 
               72  Sun gear 
               73  Planetary-gear change lever 
               74  Planetary gear 
               75  Planetary gear shaft 
               76  Planetary-gear change plate 
               77 ,  79 ,  82 ,  83 ,  88 ,  90  Gear 
               78 ,  84 ,  87 ,  89  Rotation shaft 
               80  Torque limiter 
               81  Rotation shaft 
               85  Clutch 
               86  Clutch rotor 
               86   b  Sleeve gear 
               91  Compression-plate stopper 
               92  Emergency release lever 
               93 ,  96  Tension spring 
               94  Electromagnetic attraction magnet 
               95  Restraint lever