Patent Publication Number: US-2009220055-A1

Title: Radiation image information capturing apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a radiation image information capturing apparatus equipped with a radiation source housing unit for housing a radiation source that irradiates an examinee with radiation, a radiographic image capturing base that detects radiation having passed through the examinee to acquire radiation image information, and a compression plate, which compresses and retains a region to be imaged of the examinee with respect to the image capturing base. 
     2. Description of the Related Art 
     In a radiation image information capturing apparatus, for example, in an X-ray mammography apparatus (hereinafter referred to simply as mammography apparatus), a radiation image of an object (breast of the examinee) is recorded in a radiation image recording unit (solid-state radiation detector) by irradiating the object with radiation, whereby reading of the radiation image information is performed. 
     As the aforementioned radiation image recording unit, normally, a solid-state radiation detection device of a light readout type, or of a type in which a plurality of photoelectric conversion elements and thin-film transistors (TFTs) are arranged, is used. In particular, recently, from an X-ray radiographic device utilizing an IP (imaging plate) cassette, in which a stimulable phosphor panel (IP) is accommodated, a cassetteless type of X-ray radiographic device has been developed, in which a digital image is acquired directly using a radiation conversion panel (flat panel detector, FPD). 
     However, in a mammography apparatus, in order to facilitate close contact of the examinee&#39;s breast against an image capturing base, the breast is compressed on the image capturing base using a compression plate. For this reason, there is a concern that the examinee may experience an unpleasant sensation of pressure accompanying positioning of the affected area to be imaged. 
     Consequently, for example, according to the specification of U.S. Pat. No. 5,541,972, a padding device is disposed on a front surface and side surfaces of a plate portion of an X-ray plate (image capturing base), which comes into contact with the examinee&#39;s body. Further, according to the specifications of U.S. Pat. No. 6,968,033 and U.S. Pat. No. 6,765,984, a cushion is provided, which extends from a front surface across a pressing surface of the compression plate. 
     Furthermore, according to the specification of U.S. Pat. No. 6,577,702, cushions are provided on surfaces of an image capturing base and a compression plate that come into contact with the examinee&#39;s body, whereas, according to the specification of U.S. Pat. No. 6,850,590, buffering members are disposed on various surfaces including an image capturing surface of the image capturing base, which come into contact with the examinee&#39;s body. 
     However, according to the specification of U.S. Pat. No. 5,541,972, in spite of reducing discomfort to the examinee when the examinee contacts a chest wall contacting portion of the image capturing base, there is still a concern that the examinee will be exposed to diffused X-rays, which pass from the image capturing base through the chest wall contacting portion. 
     Further, according to the specifications of U.S. Pat. No. 6,968,033, U.S. Pat. No. 6,765,984, U.S. Pat. No. 6,577,702 and U.S. Pat. No. 6,850,590, cushions (buffering members) are provided, which cover the X-ray irradiating region of the compression plate and the image capturing base. Consequently, for the cushions and the buffering members, materials that are highly permeable to X-rays must be used, and therefore it is easy for the examinee to be exposed to diffused X-rays. 
     SUMMARY OF THE INVENTION 
     The present invention has the object of overcoming the problems mentioned above, by providing a radiation image information capturing apparatus, in which excessive pressure and discomfort to an examinee are suitably avoided, and wherein unnecessary exposure to diffused radiation with respect to the examinee can be suppressed. 
     The present invention relates to a radiation image information capturing apparatus, equipped with a radiation source housing unit for housing a radiation source, which irradiates an examinee with radiation, a radiographic image capturing base that detects radiation having passed through the examinee to acquire radiation image information, and a compression plate, which compresses and retains a region of the examinee to be imaged with respect to the image capturing base. 
     The radiation image information capturing apparatus further comprises a pad member positioned outside of an irradiation region extending from the radiation source to the image capturing base, and which is detachably disposed at least on a site having a possibility of coming into contact with the examinee. The pad member has a buffering property for absorbing shocks to the examinee, and a radiation shielding property for suppressing irradiation of radiation with respect to the examinee. 
     According to the present invention, the examinee does not come into contact directly with the outer walls of the radiation image information capturing apparatus, and due to the buffering effect of the pad members, shocks to the examinee can be absorbed and buffered. Owing thereto, the examinee does not experience a sensation of excessive pressure or discomfort, and pain caused by contact with the apparatus can suitably be avoided. In addition, the pad members have a radiation shielding property, so that unnecessary exposure of the examinee to diffused radiation can suitably be suppressed. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a perspective view of a mammography apparatus making up the radiation image information capturing apparatus according to a first embodiment of the present invention; 
         FIG. 2  is an explanatory drawing showing a portion of an image capturing base in the mammography apparatus; 
         FIG. 3  is a cross-sectional explanatory view of a pad member; 
         FIG. 4  is an explanatory drawing illustrating a cranio-caudal (CC) image capturing technique performed on an examinee; 
         FIG. 5  is an explanatory drawing showing positions on which pad members are adhered; 
         FIG. 6  is a perspective view of essential parts of a mammography apparatus according to a second embodiment of the present invention; 
         FIG. 7  is an explanatory drawing illustrating a medio-lateral oblique (MLO) image capturing technique performed on an examinee; 
         FIG. 8  is a perspective view of essential parts of a mammography apparatus according to a third embodiment of the present invention; and 
         FIG. 9  is a cross-sectional explanatory view of another pad member. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , a mammography apparatus  10  forming a radiation image information capturing apparatus according to a first embodiment of the present invention comprises a base  16  positioned in an upstanding manner, an arm member  20  fixed to a swing shaft  18  disposed substantially centrally on the base  16 , a radiation source housing unit  24  fixed to an end of the arm member  20  and which accommodates therein an X-ray source (radiation source)  23  made up of a molybdenum tube, a tungsten tube, or a rhodium tube or the like, which irradiates X-rays (radiation) with respect to an examinee  22 , an image capturing base  26  affixed to another end of the arm member  20  and housing therein a solid-state detector (not shown) for detecting radiation that has passed through the examinee  22 , to thereby acquire radiation image information, and a compression plate  28  for compressing and holding a region to be imaged of the examinee  22  against the image capturing base  26 . 
     The solid-state detector comprises a direct-conversion, light readout type radiation solid-state detector. The solid-state detector stores radiation image information represented by X-ray radiation that has passed through a breast  34  (see  FIG. 2 ) as an electrostatic latent image, and generates a current that depends on the electrostatic latent image when the solid-state detector is scanned by reading light. 
     The arm member  20 , to which the radiation source housing unit  24  and the image capturing base  26  are secured, is constructed such that, by angularly moving the arm member  20  about a swing shaft  18  in the direction indicated by the arrow A, an image capturing direction with respect to the region to be imaged of the examinee  22  can be adjusted. The compression plate  28  is arranged between the radiation source housing unit  24  and the image capturing base  26 , while being connected to the arm member  20 . The compression plate  28  is configured for displacement in the direction of the arrow B. 
     A display control unit  30  is disposed on the base  16  for displaying image capturing information, including an image capturing region, an image capturing direction, and ID information of the examinee  22 , etc., which have been detected by the mammography apparatus  10 . The display control unit  30  also enables setting of such items of information as necessary. 
       FIG. 2  is an explanatory drawing showing a portion of the image capturing base  26  in the mammography apparatus  10 , showing a condition in which a breast  34  as a region to be image of the examinee  22  is set between the image capturing base  26  and the compression plate  28 . 
     As shown in  FIGS. 1 and 2 , the image capturing base  26  includes a front surface portion (chest wall portion)  36   a  facing toward the examinee  22 , side surface portions (side wall portions)  36   b,  an image capturing surface  36   c  having an image capturing area  38 , and a back surface portion  36   d  on an opposite side from the image capturing surface  36   c.  The compression plate  28  includes a front surface portion (chest wall portion)  40   a  facing toward the examinee  22 , side surface portions (side wall portions)  40   b  on both sides thereof, and a pressing surface  40   c  confronting the image capturing surface  36   c.  The radiation source housing unit  24  has a face guard surface  42  that contacts the face of the examinee  22 , and further comprises a casing (housing portion) outer surface  44  accommodating an X-ray source  23  therein. 
     In the first embodiment, pad members  46  are disposed detachably on a front surface portion  36   a  of the image capturing base  26 , on a front surface portion  40   a  of the compression plate  28 , and on a face guard surface  42  of the radiation source housing unit  24 . 
     The pad members  46  have a buffering property for absorbing shocks to the examinee  22 , as well as a radiation shielding property for suppressing radiation from being irradiated toward the examinee  22 . More specifically, by forming the pad members  46  from a polymer material, for example, urethane foam, the pad members  46  function as a soft and flexible material having a buffering property, while functioning dually as a radiation shielding material with a low permeability to X-rays. Preferably, surfaces of the pad members  46  are such that skin oils (sebaceous matter) adhere only slightly thereto and do not lead significantly to any sensation of pulling on the skin, while also having an antibacterial property. 
     With respect to the X-rays irradiated from a molybdenum, tungsten, or rhodium target through a molybdenum, tungsten, rhodium or silver filter, the pad members  46  have such X-ray permeability that after having passed through the human body (examinee  22 ) and/or a member of the apparatus, the X rays are further attenuated to 50% or less. Therefore, the amount of diffused X-rays, which is irradiated onto the examinee  22 , is suitably and significantly reduced. 
     As shown in  FIG. 3 , the pad member  46  has an outer surface of a radius of curvature R of 1 mm or greater and a thickness t of 5 mm or less. Such a pad member  46  is attached (adhered) in a detachable manner, via a double-sided tape  48 , with respect to the front surface portions  36   a,    40   a  and the face guard surface  42 . 
     Operations of the mammography apparatus shall now be explained. 
     First, using a console (not shown) and/or an ID card, etc., the operator sets ID information of the examinee  22 , and image capturing information, such as various image capturing process details, etc. In this case, the ID information represents the name, age, sex, etc., of the examinee  22 . Further, the image capturing process details include information such as an image capturing region, an image capturing direction, etc., which are specified by the doctor and may be entered by a technician from the console. The entered items of information can be displayed for confirmation on the display control unit  30  of the mammography apparatus  10 . 
     Then, the technician places the mammography apparatus  10  in a certain state in accordance with the specified image capturing method. For example, the breast  34  may be imaged as a cranio-caudal view (CC) in which an image is captured while X-rays are irradiated from above (see  FIGS. 2 and 4 ), a medio-lateral view (ML) in which an image is captured while X-rays are irradiated from side surfaces outwardly from the center of the chest, or a medio-lateral oblique view (MLO) in which an image is captured while X-rays are irradiated from an oblique direction (to be described later). Depending on the selected image capturing method, the technician turns the arm member  20  about the swing shaft  18 . 
     Next, the examinee  22  is placed in a specified image capturing condition with respect to the mammography apparatus  10 . For example, if the left breast  34  of the examinee  22  is to be imaged as a cranio-caudal view (CC), as shown in  FIGS. 2 and 4 , the left breast  34  is positioned on the image capturing base  26 , and thereafter, the compression plate  28  is lowered to hold the breast  34  between the image capturing base  26  and the compression plate  28 . 
     Then, the X-ray source  23  accommodated in the radiation source housing unit  24  is energized in order to carry out capturing of the radiation image information. X-rays emitted from the radiation source, which have passed through the breast  34  held between the compression plate  28  and the image capturing base  26 , are irradiated onto the solid-state detector (not shown) housed within the image capturing base  26 , whereupon radiation image information of the breast  34  is acquired. 
     At this time, as shown in  FIG. 4 , because cranial-caudal (CC) imaging is performed with respect to the breast  34  of the examinee  22 , the front surface portion  36   a  of the image capturing base  26  and the front surface portion  40   a  of the compression plate  28  are pressed against the examinee  22 . In addition, the head of the examinee  22  presses against the face guard surface  42 . 
     In this case, according to the first embodiment, as discussed above, when cranial-caudal (CC) imaging is performed with respect to the breast  34  of the examinee  22 , pad members  46  are attached to the front surface portion  36   a  of the image capturing base  26 , the front surface portion  40   a  of the compression plate  28 , and the face guard surface  42 , which come into direct contact with the examinee  22 . 
     As a result, the front surface portions  36   a,    40   a  and the face guard surface  42 , which are constituted by a rigid carbon covering, do not directly contact the examinee  22 , but rather, through the cushioning function of the pad members  46 , any sensation of pressure experienced by the examinee  22  can suitably be alleviated. Owing thereto, the examinee does not experience a sensation of excessive pressure or discomfort when image capturing is performed, and pain caused by contact with the apparatus can suitably be avoided. 
     In addition, the pad members  46  are constructed from a polymer material such as urethane foam, which has an X-ray shielding property. As a result thereof, X-rays that are irradiated from the X-ray source  23  become diffused, for example, inside the image capturing base  26 , and irradiation of such diffused X-rays toward the side of the examinee  22  from the front surface portion  36   a  can effectively be prevented by means of the pad member  46 . Accordingly, unnecessary exposure to diffused X-ray radiation with respect to the examinee  22  can effectively be suppressed. 
     Similarly, due to the pad member  46  disposed on the front surface portion  40   a  of the compression plate  28 , unnecessary exposure to diffused X-ray radiation with respect to the examinee  22  can be prevented. Also, due to the pad member  46  disposed on the face guard surface  42 , unnecessary exposure to diffused X-ray radiation, directed from the face guard surface  42  toward the examinee  22 , can suitably be suppressed. 
     Further, as shown in  FIG. 5 , according to the first embodiment, the pad member  46  can be disposed on all or part of at least the front surface portion  36   a  of the image capturing base  26 . Furthermore, on the image capturing base  26 , apart from the front surface portion  36   a,  pad members can be disposed on at least any of all or part of each of the side surface portions  36   b,  on a region outside of the image capturing area (radiation irradiating area)  38  of the image capturing surface  36   c,  and on a back surface portion  36   d  of the image capturing base  26 . 
     The pad members  46  are disposed on all or part of at least the front surface portion  40   a  of the compression plate  28 . Pad members  46  can also be disposed on all or part of each of the side surface portions  40   b  of the compression plate  28 . 
     On the other hand, on the radiation source housing unit  24 , although the pad member  46  is disposed only on the face guard surface  42  thereof, if desired, pad members  46  may also be disposed from the front surface and over the side surfaces of the casing outer surface  44 , which accommodate the X-ray source  23  therein. Owing thereto, when the arm member  20  is pivoted, a favorable condition results in that the casing outer surface  44  does not directly contact the examinee  22 . 
       FIG. 6  is a perspective view of essential parts of a mammography apparatus  60  according to a second embodiment of the present invention. Structural elements thereof, which are the same as those of the mammography apparatus  10  according to the first embodiment, are designated with the same reference characters, and detailed explanations of such features are omitted. Further, similarly, in the third embodiment described below, detailed explanations of such features are omitted as well. 
     In the mammography apparatus  60 , pad members  62  are adhered to the image capturing base  26 , so as to cover the corners formed by the front surface portion  36   a  and both side surface portions  36   b  of the image capturing base  26 . A single pad member  62  may be constructed as a unitary body. Alternatively, as shown in  FIG. 6 , the pad member  62  may be divided into two sections. The pad members  62  are constructed in the same manner as the above-mentioned pad member  46 , having a desired buffering property for absorbing shocks and a desired X-ray radiation shielding property. 
     The mammography apparatus  60  is particularly suitable when capturing a medio-lateral oblique (MLO) image of the breast  34 . More specifically, as shown in  FIG. 7 , when a medio-lateral oblique (MLO) image of the breast  34  of an examinee  22  is captured, the front surface portion  36   a  of the image capturing base  26 , as well as both side surface portions  36   b  of the image capturing base  26  and the front surface portion  40   a  of the compression plate  28 , come into contact with the examinee  22 . Owing thereto, in particular, due to both front corner portions of the image capturing base  26 , it is easy for a sense of pressure and discomfort to be imparted to the examinee  22 . 
     Accordingly, by disposing the pad members  62  corresponding to the front corner portions of the image capturing base  26 , any sensation of pressure or unpleasantness caused by the corners of the image capturing base  26  can suitably be suppressed. 
       FIG. 8  is a perspective view of essential parts of a mammography apparatus  70  according to a third embodiment of the present invention. 
     A pad member  72  is attached to the image capturing base  26  that makes up the mammography apparatus  70 , at a position corresponding to a corner area between the front surface portion  36   a  and the back surface portion  36   d  thereof. The pad member  72  produces the same effects as the aforementioned pad member  46 . 
     As a result, according to the third embodiment, the corner area between the front surface portion  36   a  and the back surface portion  36   d  of the image capturing base  26  does not come into direct contact with the examinee  22 . Owing thereto, any sensation of pressure or unpleasantness imposed on the examinee  22  can effectively be suppressed. 
     Moreover, in the first through third embodiments, pad members  46 ,  62  and  72  are used, which are constructed respectively in the same manner. However, in place of such a configuration, pad members  80  as shown in  FIG. 9  may also be used. 
     The pad member  80 , for example, includes a sheet member  82  with low radiation permeability, and a foam-containing soft flexible member  84 , which are attached via a double-sided tape  48  to the front surface portion  36   a . Specifically, the sheet member  82  may be formed by a lead sheet, a flame-retardant resin sheet, or the like, whereas the soft flexible member  84  is formed by a material having a desirable cushioning property. The pad member  80  configured in this manner produces the same effects as the aforementioned pad members  46 ,  62  and  72 . 
     Although certain preferred embodiments of the present invention have been shown and described in detail, the invention is not limited by the aforementioned embodiments. It should be understood that various changes and modifications may be made to the embodiments without departing from the scope of the invention as set forth in the appended claims.