Patent Publication Number: US-2015065801-A1

Title: Guidance device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT international application Ser. No. PCT/JP2013/062851 filed on May 7, 2013 which designates the United States, incorporated herein by reference, and which claims the benefit of priority from Japanese Patent Application No. 2012-106330, filed on May 7, 2012, incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to a guidance device for guiding a capsule medical apparatus introduced into a subject. 
     2. Related Art 
     In the field of an endoscope, there has been promoted the development of a capsule endoscope having a size that allows for being introduced into the gastrointestinal tract of a subject such as a patient. The capsule endoscope has an imaging function and a wireless communication function inside a capsule-shaped casing. The capsule endoscope is swallowed through the mouth of a subject, and thereafter travels in the gastrointestinal tract by peristaltic movement or the like. Meanwhile, image data of the inside of the organ of a subject (hereinafter, also referred to as an in-vivo image) is sequentially acquired, and wirelessly transmitted to a receiving device placed outside a subject. The image data received by a receiving device is incorporated in an image display apparatus to be subjected to certain image processing. Accordingly, an in-vivo image is displayed as a still image or a moving image on a display screen. A user such as a medical doctor or a nurse observes the in-vivo image displayed on the image display apparatus in this manner, and diagnoses the condition of the organ of a subject. 
     There is recently proposed a guidance system that guides with a magnetic force (hereinafter, referred to as magnetically guides) a capsule endoscope introduced into a subject (for example, see Japanese Patent Application Laid-open No. 2006-68501 and JP-T-2008-503310). Generally, in such a guidance system, a permanent magnet is disposed inside the capsule endoscope, and a guidance device including a magnetic field generation unit such as an electromagnet is disposed outside a subject. A magnetic field generated by the magnetic field generation unit is applied to the permanent magnet provided inside the capsule endoscope. With a magnetic attracting force caused by the generated magnetic field, the capsule endoscope is magnetically guided to a desired position. 
     Also, there is another guidance device provided with a display unit that receives image data acquired by the capsule endoscope and displays an in-vivo image; an input device that operates the position or posture of the capsule endoscope; and the like. In the case of such a guidance device, a user can operate the magnetic guidance of the capsule endoscope using the input device while referring to the in-vivo image displayed on the display unit. 
     Also, there has been developed a system that applies a magnetic field from the outside of a subject to the capsule endoscope to perform signal control such as on/off of a switch for the capsule endoscope (for example, see WO 2007/083708). 
     SUMMARY 
     A guidance device according to some embodiments is a guidance device for applying a magnetic field to a capsule medical apparatus within which a first permanent magnet is arranged when the capsule medical apparatus is introduced into a subject, to guide the capsule medical apparatus within the subject. The guidance device includes a second permanent magnet that is configured to be disposed outside the subject and has a rectangular parallelepiped shape or a polygonal column shape, the second permanent magnet having a first plane containing a magnetization direction and a first direction orthogonal to the magnetization direction, and being configured to confine the capsule medical apparatus within a region facing the first plane. The second permanent magnet has a length in the first direction longer than a length in the magnetization direction. 
     The above and other features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a capsule medical apparatus guidance system according to a first embodiment of the present invention; 
         FIG. 2  is a partial sectional side view schematically illustrating a configuration example when the guidance device illustrated in  FIG. 1  is in a magnetic field generating state; 
         FIG. 3  is a partial sectional side view schematically illustrating a configuration example when the guidance device illustrated in  FIG. 1  is in a magnetic field shielding state; 
         FIG. 4  is a schematic diagram for explaining an installed state of the extracorporeal permanent magnet illustrated in  FIG. 2 ; 
         FIG. 5  is a cross-sectional schematic diagram illustrating an example of an internal configuration of the capsule endoscope illustrated in  FIG. 1 ; 
         FIG. 6  is a schematic diagram for explaining a relative positional relationship between an imaging element and a permanent magnet inside a capsule endoscope; 
         FIG. 7  is a conceptual diagram for explaining a situation of a capsule endoscope when a liquid is introduced into a subject (a state in which a magnetic field is not allowed to act); 
         FIG. 8  is a conceptual diagram for explaining a situation of a capsule endoscope when a liquid is introduced into a subject (a state in which a magnetic field is allowed to act); 
         FIG. 9  is a diagram illustrating an example of an image displayed on a display screen of the display unit illustrated in  FIG. 1 ; 
         FIGS. 10A and 10B  are schematic diagrams for explaining a position control method in a horizontal direction of a capsule endoscope; 
         FIGS. 11A and 11B  are schematic diagrams for explaining a position control method in a vertical direction of a capsule endoscope; 
         FIGS. 12A and 12B  are diagrams illustrating an example of the operation input unit illustrated in  FIG. 1 ; 
         FIG. 13  is a diagram for explaining magnetic guidance of a capsule endoscope operable by the operation input unit illustrated in  FIG. 1 ; 
         FIG. 14  is a diagram exemplifying a menu screen displayed on a display unit; 
         FIG. 15  is a flow chart illustrating action of the capsule medical apparatus guidance system illustrated in  FIG. 1 ; 
         FIG. 16  is a partial sectional side view schematically illustrating a configuration example when the guidance device illustrated in  FIG. 1  is in a weak magnetic field generating state; 
         FIG. 17  is a schematic diagram for explaining evaluation items in a simulation of calculating the relationship between the shape of an extracorporeal permanent magnet and the generated magnetic field; 
         FIG. 18  is a table illustrating a ratio in length among sides of a permanent magnet used in the simulation; 
         FIG. 19  is a graph illustrating magnetic field strengths of the permanent magnets illustrated in  FIG. 18 ; 
         FIG. 20  is a graph illustrating magnetic field gradients in the z-axis direction generated by the permanent magnets illustrated in  FIG. 18 ; 
         FIG. 21  is a graph illustrating magnetic field gradients in the x-axis direction generated by the permanent magnets illustrated in  FIG. 18 ; 
         FIG. 22  is a graph illustrating magnetic field gradients in the y-axis direction generated by the permanent magnets illustrated in  FIG. 18 ; 
         FIG. 23  is a table illustrating a ratio in length among sides of each permanent magnet used in another simulation; 
         FIG. 24  is a graph illustrating magnetic field strengths of the permanent magnets illustrated in  FIG. 23 ; 
         FIG. 25  is a graph illustrating magnetic field gradients in the z-axis direction generated by the permanent magnets illustrated in  FIG. 23 ; 
         FIG. 26  is a graph illustrating magnetic field gradients in the x-axis direction generated by the permanent magnets illustrated in  FIG. 23 ; 
         FIG. 27  is a graph illustrating magnetic field gradients in the y-axis direction generated by the permanent magnets illustrated in  FIG. 23 ; 
         FIG. 28  is a graph illustrating a relationship between the ratio of a length in the y-axis direction to a length in the z-axis direction, and the ratio of a magnetic field strength of a permanent magnet having each dimensional ratio to a magnetic field strength of a permanent magnet of type y-x-z (33); 
         FIG. 29  is a table illustrating a ratio in length among sides of each permanent magnet used in further simulation; 
         FIG. 30  is a graph illustrating a relationship between a length in the z-axis direction and a magnetic field strength of each permanent magnet illustrated in  FIG. 29 ; 
         FIG. 31  is a graph illustrating a relationship between a length in the z-axis direction and a magnetic field gradient in the z-axis direction of each permanent magnet illustrated in  FIG. 29 ; 
         FIG. 32  is a graph illustrating a relationship between a length in the z-axis direction and a magnetic field gradient in the x-axis direction of each permanent magnet illustrated in  FIG. 29 ; 
         FIG. 33  is a graph illustrating a relationship between a length in the z-axis direction and a magnetic field gradient in the y-axis direction of each permanent magnet illustrated in  FIG. 29 ; 
         FIG. 34  is a table illustrating evaluation of the results indicated in  FIG. 30  to  FIG. 33 ; 
         FIGS. 35A and 35B  are diagrams illustrating an example of the operation input unit according to modified example 1-1; 
         FIG. 36  is a diagram for explaining magnetic guidance of a capsule endoscope operable by the operation input unit illustrated in  FIGS. 35A and 35B ; 
         FIG. 37  is a schematic diagram illustrating a modified example of the magnetic field generating unit illustrated in  FIG. 1 ; 
         FIG. 38  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field generating state) of the capsule medical apparatus guidance system according to a second embodiment of the present invention; 
         FIG. 39  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field shielding state) of the capsule medical apparatus guidance system according to the second embodiment of the present invention; 
         FIG. 40  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field generating state) of the capsule medical apparatus guidance system according to a third embodiment of the present invention; 
         FIG. 41  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field shielding state) of the capsule medical apparatus guidance system according to the third embodiment of the present invention; 
         FIG. 42  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field generating state) of the capsule medical apparatus guidance system according to a fourth embodiment of the present invention; 
         FIG. 43  is a partial sectional side view schematically illustrating a configuration example (in a magnetic field shielding state) of the capsule medical apparatus guidance system according to the fourth embodiment of the present invention; and 
         FIG. 44  is a perspective view schematically illustrating a configuration example of the capsule medical apparatus guidance system according to a fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A guidance device according to some embodiments of the present invention will be described below with reference to the drawings. Although the following description illustrates a guidance system for a capsule endoscope that uses, as a capsule medical apparatus, a capsule endoscope that is orally introduced into a subject and floats in a liquid stored in the stomach of a subject, the embodiment does not limit the present invention. That is, in the present invention, there can be used various capsule medical apparatuses such as a capsule endoscope that moves in the lumen from the esophagus to the anus of a subject, and a capsule endoscope to be inserted together with an isotonic solution from the anus. Also, in the following description, the shape, the size and the positional relationship in each drawing are merely schematically illustrated to a degree that facilitates understanding of a content of the present invention. Therefore, the present invention is not limited only by the shape, the size and the positional relationship illustrated in each drawing. Here, in the description of the drawings, the same signs are assigned to the same parts. 
     First Embodiment 
       FIG. 1  is a schematic diagram illustrating a configuration example of a capsule medical apparatus guidance system according to a first embodiment of the present invention. As illustrated in  FIG. 1 , a capsule medical apparatus guidance system (hereinafter, also merely referred to as a guidance system)  1  according to the first embodiment includes a capsule endoscope  10  and a guidance device  20 . The capsule endoscope  10  is a capsule medical apparatus to be introduced into the body cavity of a subject, and contains a permanent magnet therein. The guidance device  20  generates a three-dimensional magnetic field to magnetically guide the capsule endoscope  10  introduced into the subject. 
       FIG. 2  and  FIG. 3  are each a partial sectional side view schematically illustrating a configuration example of the guidance device  20 .  FIG. 2  illustrates a state in which a magnetic field for guiding the capsule endoscope  10  is not shielded (hereinafter, referred to as a magnetic field generating state). On the other hand,  FIG. 3  illustrates a state in which a magnetic field for guiding the capsule endoscope  10  is shielded (hereinafter, referred to as a magnetic field shielding state). 
     As illustrated in  FIG. 2  and  FIG. 3 , the guidance device  20  includes a bed  20   a  supported by a leg  20   b . The bed  20   a  serves as a placing table on which a subject  101  is placed. Hereinafter, an area to which a magnetic field capable of guiding the capsule endoscope  10  is generated is referred to as an effective magnetic field area  100 . In the first embodiment, the effective magnetic field area  100  is set in a portion of the region above the bed  20   a . Usually, the subject  101  is placed on the bed  20   a  such that an examination (diagnosis) target region is overlapped with the effective magnetic field area  100 . 
     The capsule endoscope  10  is introduced into the inside of the organ of the subject  101  along with a certain liquid through oral intake, then moves through the inside of the gastrointestinal tract, and is finally discharged to the outside of the subject  101 . Meanwhile, the capsule endoscope  10  floats in a liquid introduced into the inside of the organ (for example, the inside of the stomach) of the subject  101 , and sequentially takes an image of the inside of the subject  101  while being magnetically guided by the magnetic field generated by the guidance device  20 . Then, the capsule endoscope  10  sequentially wirelessly transmits image information (image data) corresponding to an in-vivo image acquired by imaging. The detailed configuration of the capsule endoscope  10  will be described later. 
     The guidance device  20  includes: a receiver  21  that performs wireless communication with the capsule endoscope  10  to receive a wireless signal containing image information acquired by the capsule endoscope  10 ; a position detector  22  that detects a position of the capsule endoscope  10  within the subject  101  based on the wireless signal received from the capsule endoscope  10 ; a display unit  23   a  that acquires the image information from the wireless signal received by the receiver  21  and displays on a screen an in-vivo image obtained by performing specified signal processing on the image information as well as various information; a notifying unit  23   b  that performs notification to a user with visual information or auditory information; an operation input unit  24  that receives input of information that instructs various operations in the guidance system  1 , and the like; a magnetic field generating unit  25  that generates a magnetic field for guiding the capsule endoscope  10 ; a shielding unit  26  that shields the magnetic field generated by the magnetic field generating unit  25 ; a shielding state detector  27  that detects a shielding state of a magnetic field by the shielding unit  26 ; a control unit  28  that controls these components; and a storage unit  29  that stores image information taken by the capsule endoscope  10 , and the like. 
     The receiver  21  includes a plurality of antennas  21   a , and sequentially receives a wireless signal from the capsule endoscope  10  through the plurality of antennas  21   a . The receiver  21  selects an antenna having the highest received electric field strength among the plurality of antennas  21   a , and performs, for example, demodulation processing on the wireless signal received from the capsule endoscope  10  through the selected antenna. Thus, the receiver  21  extracts image data on the inside of the subject  101  from this wireless signal. The receiver  21  outputs an image signal containing the extracted image data to the display unit  23   a.    
     The position detector  22  performs calculation to estimate the position of the capsule endoscope  10  within the subject  101 , based on the signal strength of the wireless signal received by the receiver  21 . 
     The display unit  23   a  includes various displays such as a liquid crystal display, and generates an in-vivo image based on the image data input from the receiver  21  and a screen containing other various information, to be displayed on a display. Specifically, the display unit  23   a , for example, sequentially displays on a screen a group of in-vivo images of the subject  101  taken by the capsule endoscope  10  while displaying the information on the position and posture of the capsule endoscope  10  and the information on guidance operation. At this time, the display unit  23   a  may display the position and posture of the capsule endoscope  10  estimated based on the magnetic field generated by the guidance device  20 , or may display on a screen the position within the subject  101  corresponding to the displayed in-vivo image based on the position detection result of the position detector  22 . Also, the display unit  23   a  displays, for example, a reduced image of the in-vivo image selected in accordance with control of the control unit  28 , patient information and examination information of the subject  101 , and the like. Furthermore, the display unit  23   a  displays on a screen a warning to a user and information such as a state of the guidance device  20  (for example, the magnetic field generating state or the magnetic field shielding state) in accordance with control of the control unit  28 . 
     The notifying unit  23   b  includes, for example, an illumination device such as an LED and a voice device such as a buzzer, as well as a drive circuit that operates under control of the control unit  28  for controlling these devices. The notifying unit  23   b  notifies a user of a warning through the flashing of illumination or the sound of a buzzer, or notifies a user of a state of the guidance device  20  (for example, the magnetic field generating state or the magnetic field shielding state) through the lighting of illumination with a specified color. 
     The operation input unit  24  is achieved by an input device such as a joy stick, a console equipped with various buttons and various switches, and a keyboard, and receives input of various types of information such as the guidance instruction information for magnetically guiding the capsule endoscope  10  and the setting information for setting a specified mode to the guidance device  20 . The guidance instruction information is information for controlling the position and posture of the capsule endoscope  10  that is a target of the magnetic guidance operation. In particular, the guidance instruction information includes information on the action of changing the position of the capsule endoscope  10  and the action of changing a tilt angle (an angle with respect to the vertical axis) of the capsule endoscope  10 , and information on the action of changing an azimuth angle (an angle around the vertical axis) of the visual field (imaging units  11 A and  11 B described later) of the capsule endoscope  10 . Hereinafter, the azimuth angle of the visual field is merely referred to as an azimuth angle. The operation input unit  24  inputs the above-described received information to the control unit  28 . 
     The magnetic field generating unit  25  is disposed below the bed  20   a  (inside the leg  20   b ), and generates a magnetic field for changing the position, tilt angle and azimuth angle of the capsule endoscope  10  introduced into the subject  101  relative to the subject  101 , to the effective magnetic field area  100 . Here, in order to inhibit the leakage of the magnetic field generated by the magnetic field generating unit  25  into a space other than the effective magnetic field area  100  (for example, in a side surface direction of the leg  20   b ), the leg  20   b  is preferably made of a ferromagnetic substance such as an iron plate. 
     The magnetic field generating unit  25  has an extracorporeal permanent magnet  25   a  that generates a magnetic field, as well as a plane position changing unit  25   b , a vertical position changing unit  25   c , an elevation angle changing unit  25   d , and a revolution angle changing unit  25   e  as a mechanism of translating and rotating the extracorporeal permanent magnet  25   a.    
       FIG. 4  is a schematic diagram for explaining an installed state of the extracorporeal permanent magnet  25   a . As illustrated in  FIG. 4 , the extracorporeal permanent magnet  25   a  is achieved by, for example, a bar magnet having a rectangular parallelepiped shape. The extracorporeal permanent magnet  25   a  confines the capsule endoscope  10  within a region facing a plane that contains a magnetization direction and a first direction orthogonal to the magnetization direction. Hereinafter, the plane of the extracorporeal permanent magnet  25   a  that faces the capsule endoscope  10  is referred to as a capsule facing plane PL1 (a first plane). 
     The extracorporeal permanent magnet  25   a  is arranged using an optional plane parallel to the first direction (a y-axis direction in  FIG. 4 ) as a reference. In the present first embodiment, the reference plane is set in parallel to a horizontal plane, and in an initial state of the capsule endoscope  10 , the capsule facing plane PL1 is arranged so as to be parallel to the reference plane (a horizontal plane). Hereinafter, the arrangement of the extracorporeal permanent magnet  25   a  when the extracorporeal permanent magnet  25   a  is in an initial state of the capsule endoscope  10  is defined as an initial position. The magnetization direction at this time is defined as an x-axis direction; a direction within the horizontal plane orthogonal to the magnetization direction is defined as a y-axis direction; and a vertical direction is defined as a z-axis direction. 
     In the extracorporeal permanent magnet  25   a , among the lengths of the sides in the three directions of the rectangular parallelepiped shape, the length of the side in the direction orthogonal to the magnetization direction on the capsule facing plane PL1 (the y-axis direction in  FIG. 4 ) is longer than the lengths of the sides in the magnetization direction (the x-axis direction in  FIG. 4 ) and in the direction orthogonal to the capsule facing plane PL1 (the z-axis direction in  FIG. 4 ). Preferably, the extracorporeal permanent magnet  25   a  has a flat plate shape in which, among the lengths of the sides in the three directions of the rectangular parallelepiped shape, the length in the direction orthogonal to the capsule facing plane PL1 is the shortest. The shape of the extracorporeal permanent magnet  25   a  will be described in detail later. 
     The plane position changing unit  25   b  is a translation mechanism that translates the extracorporeal permanent magnet  25   a  on the horizontal plane set as a reference plane. That is, the movement is performed within the horizontal plane while maintaining a state in which the relative position of two magnetic poles magnetized in the extracorporeal permanent magnet  25   a  is ensured. 
     The vertical position changing unit  25   c  is a translation mechanism that translates the extracorporeal permanent magnet  25   a  in the vertical direction orthogonal to the horizontal plane set as a reference plane. 
     The elevation angle changing unit  25   d  is a rotation mechanism that rotates the extracorporeal permanent magnet  25   a  around an axis that is parallel to the capsule facing plane PL1 and orthogonal to the magnetization direction and that extends through the center of the extracorporeal permanent magnet  25   a  (hereinafter, referred to as a rotation axis Y C ), thereby to change the angle of the magnetization direction with respect to the horizontal plane set as a reference plane. Hereinafter, an angle formed between the extracorporeal permanent magnet  25   a  and the horizontal plane is defined as an elevation angle θ. 
     The revolution angle changing unit  25   e  rotates the extracorporeal permanent magnet  25   a  around an axis orthogonal to the reference plane. In the present first embodiment, the axis in the vertical direction extending through the center of the extracorporeal permanent magnet  25   a  is defined as a rotation axis of the extracorporeal permanent magnet  25   a . Hereinafter, the rotation motion around the axis in the vertical direction of the extracorporeal permanent magnet  25   a  is referred to as a revolution motion. Also, the angle at which the extracorporeal permanent magnet  25   a  revolves with respect to the initial position is defined as a revolution angle ψ. 
     The revolution angle changing unit  25   e  revolves the extracorporeal permanent magnet  25   a  at the revolution angle ψ, to change the angle of the rotation axis Y C  with respect to the initial position. In this state, the elevation angle changing unit  25   d  rotates the extracorporeal permanent magnet  25   a  around the rotation axis Y C . This enables the azimuth angle and the tilt angle of the capsule endoscope  10  confined by the magnetic field generated by the extracorporeal permanent magnet  25   a  to be changed. 
     As illustrated in  FIG. 2  and  FIG. 3 , the shielding unit  26  has: a plate-shaped magnetic body member  26   a  disposed on a lower surface of the bed  20   a ; a support  26   b  that slidably supports the magnetic body member  26   a  to a main surface of the bed  20   a  in a lower surface of the bed  20   a ; a drive unit  26   c  that drives the magnetic body member  26   a  along the bed  20   a ; and a fixing unit  26   d.    
     Here, the extracorporeal permanent magnet  25   a , unlike an electromagnet, cannot perform on/off of magnetic field formation, adjustment of magnetic field strength, and the like. That is, a permanent magnet constantly generates a magnetic field having certain strength. Therefore, when guidance operation of the capsule endoscope  10  is not performed, or when the guidance device  20  is not used, the magnetic field needs to be reduced in strength, or preferably shielded, in order to inhibit an unintended movement of the capsule endoscope  10  or an influence on the subject  101 . In this regard, a configuration is conceivable in which when the guidance device  20  is not used, a covering unit made of a ferromagnetic substance covers the extracorporeal permanent magnet  25   a  for shielding. However, in this case, operation of shielding a magnetic field is complicated, and, for example, it is difficult to take a quick action in an emergency. 
     On the contrary, in the present first embodiment, the guidance device  20  is provided with the shielding unit  26 . Thus, there is provided a configuration in which the magnetic field in the effective magnetic field area  100  can be shielded by a simpler operation. 
     The magnetic body member  26   a  is preferably made of a ferromagnetic substance, and is inserted below the bed  20   a  thereby to shield the magnetic field generated by the magnetic field generating unit  25  to the effective magnetic field area  100 . The magnetic body member  26   a  has a material and a size (width×length×thickness) that allow the magnetic field generated by the magnetic field generating unit  25  to be shielded in the effective magnetic field area  100 . As described herein, a width means a dimension in the width direction of the subject  101 , and a length means a dimension in the body length direction of the subject  101 . In the first embodiment, as the magnetic body member  26   a , for example, there is used a member having a size of a width approximately equal to the width of the bed  20   a ×a length approximately half the length of the bed  20   a.    
     A concave  20   c  to which the magnetic body member  26   a  is to be arranged is disposed on the lower surface of the bed  20   a . The concave  20   c  is positioned so as to correspond to from the effective magnetic field area  100  that is a region on which the examination target region (for example, the stomach) of the subject  101  is placed, to a region on which the non-examination target region (for example, the leg) is placed. The magnetic body member  26   a  slides and moves in the concave  20   c  along the length direction of the bed  20   a.    
     The support  26   b  supports the magnetic body member  26   a  arranged in the concave  20   c  upward. Preferably, in order to allow the magnetic body member  26   a  to easily slide, rails and pulleys may be disposed on an upper surface of the support  26   b  (a contact surface with the magnetic body member  26   a ). 
     The drive unit  26   c  drives the magnetic body member  26   a  to move in the concave  20   c  along the length direction of the bed  20   a , thereby to insert and remove the magnetic body member  26   a  into and from between the magnetic field generating unit  25  and the effective magnetic field area  100 . When the magnetic body member  26   a  is inserted between the magnetic field generating unit  25  and the effective magnetic field area  100 , the guidance device  20  becomes in the magnetic field shielding state (see  FIG. 3 ). On the other hand, when the magnetic body member  26   a  is removed from between the magnetic field generating unit  25  and the effective magnetic field area  100 , the guidance device  20  becomes in the magnetic field generating state (see  FIG. 2 ). 
     The fixing unit  26   d  is disposed near the middle of the concave  20   c , and fixes the position of the magnetic body member  26   a  so that an unintended shifting between the magnetic field generating state and the magnetic field shielding state does not occur. Particularly, when the guidance device  20  is in the magnetic field generating state (see  FIG. 2 ), the magnetic field generated by the magnetic field generating unit  25  causes a magnetic attracting force for sliding the magnetic body member  26   a  toward the position in the magnetic field shielding state, to act on the magnetic body member  26   a . For this reason, the fixing unit  26   d  mechanically inhibits the movement of the magnetic body member  26   a . Also, when shifting from the magnetic field generating state to the magnetic field shielding state is performed, a drive unit (not shown) that operates under control of the control unit  28  drives the fixing unit  26   d  to move upward in the drawing. Accordingly, the fixing state of the magnetic body member  26   a  is released (see  FIG. 3 ). In this case, the fixing unit  26   d  can be manually operated to release the fixing state of the magnetic body member  26   a.    
     The shielding state detector  27  is achieved by, for example, a pressure sensor that detects a pressure in the horizontal direction applied to the magnetic body member  26   a . Here, as described above, when the guidance device  20  is in the magnetic field generating state (see  FIG. 2 ), a magnetic attracting force acts between the extracorporeal permanent magnet  25   a  and the magnetic body member  26   a . Therefore, at this time, the magnetic body member  26   a  is applied with a pressure in the left direction of the drawing in the horizontal direction. On the other hand, when the guidance device  20  is in the magnetic field shielding state (see  FIG. 3 ), a magnetic attracting force between the extracorporeal permanent magnet  25   a  and the magnetic body member  26   a  mainly acts in an up-and-down direction. Therefore, the magnetic body member  26   a  is hardly applied with a pressure in the horizontal direction. Thus, a pressure in the horizontal direction applied to the magnetic body member  26   a  is detected by the shielding state detector  27 , thereby to determine a state of the guidance device  20 . That is, when the output value of the shielding state detector  27  is a specified threshold value or more, the guidance device  20  can be determined to be in the magnetic field generating state. Conversely, when the output value is lower than a specified threshold value, the guidance device  20  can be determined to be in the magnetic field shielding state. In this case, this determination is made by the control unit  28  based on the output result of the shielding state detector  27 . 
     Also, as the shielding state detector  27 , other than a pressure sensor, any sensor such as a compression sensor, a distortion sensor and an acceleration sensor (a force sensor) may be used as long as the magnitude of the force in a specified direction applied to the magnetic body member  26   a  can be detected. Alternatively, a force applied to the extracorporeal permanent magnet  25   a , instead of the magnetic body member  26   a , may be detected thereby to determine the state of the guidance device  20 . 
     The control unit  28  controls action of each component of the magnetic field generating unit  25  based on the detection result of the position detector  22  and the guidance instruction information input from the operation input unit  24 , to achieve the position, the tilt angle and the azimuth angle of the capsule endoscope  10  as a user desires. Also, the control unit  28  controls the shielding unit  26  in accordance with an operation signal input from the operation input unit  24 , so that the guidance device  20  is shifted to a state corresponding to the status of a capsule endoscope examination (the magnetic field generating state or the magnetic field shielding state). 
     The storage unit  29  is achieved by using a storage medium that stores information in a rewritable manner, such as a flash memory and a hard disk. The storage unit  29  stores information such as various programs and various parameters used when the control unit  28  controls the components of the guidance device  20  as well as image data of a group of the in-vivo images of the subject  101  taken by the capsule endoscope  10 . 
     Next, the detailed configuration of the capsule endoscope  10  will be described.  FIG. 5  is a cross-sectional schematic diagram illustrating an example of an internal configuration of the capsule endoscope  10 . As illustrated in  FIG. 5 , the capsule endoscope  10  includes a capsule-shaped casing  12  that is a sheath with a size allowing for being easily introduced into the organ of the subject  101 , and imaging units  11 A and  11 B that take images of an imaging subject in different imaging directions from each other to generate image information. The capsule endoscope  10  also includes a wireless communication unit  16  that wirelessly transmits the image information acquired by the imaging units  11 A and  11 B to the outside, a control unit  17  that controls each component of the capsule endoscope  10 , and a power source unit  18  that supplies electric power to each component of the capsule endoscope  10 . The capsule endoscope  10  further includes a permanent magnet  19  for enabling magnetic guidance by the guidance device  20 . 
     The capsule-shaped casing  12  is a sheath case with a size allowing for being introduced into the organ of the subject  101 , and is achieved by closing the opening ends on both sides of a tubular casing  12   a  with dome-shaped casings  12   b  and  12   c . The dome-shaped casings  12   b  and  12   c  are each a dome-shaped optical member that is transparent to light in a specified wavelength range such as visible light. Also, the tubular casing  12   a  is a colored casing that is substantially opaque to visible light. The capsule-shaped casing  12  constituted by the tubular casing  12   a  and the dome-shaped casings  12   b  and  12   c  liquid-tightly contains, as illustrated in  FIG. 5 , the imaging units  11 A and  113 , the wireless communication unit  16 , the control unit  17 , the power source unit  18  and the permanent magnet  19  therein. 
     The imaging unit  11 A has an illumination unit  13 A such as an LED, an optical system  14 A such as a condenser lens, and an imaging element  15 A such as a CMOS image sensor or a CCD. The illumination unit  13 A emits illumination light such as white light to the imaging visual field of the imaging element  15 A, and illuminates an imaging subject within the imaging visual field through the dome-shaped casing  12   b . The optical system  14 A concentrates reflected light from this imaging visual field on the imaging surface of the imaging element  15 A, and forms an imaging subject image in the imaging visual field. The imaging element  15 A receives the light that is reflected from the imaging visual field and concentrated on the imaging surface, and performs photoelectric conversion of the received optical signal, to generate image information indicating a subject image in the imaging visual field, that is an in-vivo image of the subject  101 . 
     The imaging unit  11 B has, similarly to the imaging unit  11 A, an illumination unit  13 B such as an LED, an optical system  14 B such as a condenser lens, and an imaging element  15 B such as a CMOS image sensor or a CCD. 
     As illustrated in  FIG. 5 , when the capsule endoscope  10  is a twin-lens type capsule medical apparatus that takes images of the front and the back in a long axis La direction, the imaging units  11 A and  11 B are arranged so that each optical axis is substantially parallel to or substantially coincide with the long axis La that is the central axis in the longitudinal direction of the capsule-shaped casing  12 , and so that both imaging visual fields are opposed to each other. That is, the imaging units  11 A and  11 B are mounted so that the imaging surfaces of the imaging elements  15 A and  15 B are orthogonal to the long axis La. 
     The wireless communication unit  16  includes an antenna  16   a , and sequentially wirelessly transmits the above-described image information acquired by the imaging units  11 A and  11 B to the outside via the antenna  16   a . Specifically, the wireless communication unit  16  acquires an image signal based on the image information generated by the imaging unit  11 A or the imaging unit  11 B from the control unit  17 , and performs modulation processing on the image signal, to generate a wireless signal obtained by modulating the image signal. The wireless communication unit  16  transmits this wireless signal to the outside receiver  21  through the antenna  16   a.    
     The control unit  17  controls actions of the imaging units  11 A and  11 B and the wireless communication unit  16 , and also controls input and output of signals among these components. Specifically, the control unit  17  allows the imaging element  15 A to take an image of an imaging subject within the imaging visual field illuminated by the illumination unit  13 A, and allows the imaging element  15 B to take an image of an imaging subject within the imaging visual field illuminated by the illumination unit  13 B. Also, the control unit  17  has a signal processing function of generating an image signal. The control unit  17  acquires image information from the imaging elements  15 A and  15 B, and for every acquisition, performs a specified signal processing on this image information, to generate an image signal containing image data. Furthermore, the control unit  17  controls the wireless communication unit  16  to sequentially wirelessly transmit such an image signal to the outside in chronological order. 
     The power source unit  18  is an electric storage unit such as a button-type battery or a capacitor, and has a switch unit such as a magnetic switch and an optical switch. The power source unit  18  switches an on/off state of the power source by the magnetic field applied from the outside. In an on-state, the electric power in the electric storage unit is appropriately supplied to each component of the capsule endoscope  10  (the imaging units  11 A and  11 B, the wireless communication unit  16 , and the control unit  17 ). Also, in an off-state, the power source unit  18  stops the supply of electric power to each component of the capsule endoscope  10 . 
     The permanent magnet  19  is provided for enabling magnetic guidance of the capsule endoscope  10  in the effective magnetic field area  100  with the magnetic field generated by the magnetic field generating unit  25 , and is fixed and arranged to the inside of the capsule-shaped casing  12  so that the magnetization direction is tilted with respect to the long axis La. Specifically, the permanent magnet  19  is arranged so that the magnetization direction is orthogonal to the long axis La. The permanent magnet  19  acts while following the magnetic field applied from the outside. As a result, magnetic guidance of the capsule endoscope  10  by the magnetic field generating unit  25  is achieved. 
     Here, with reference to  FIG. 6 , the relative positional relationship between the imaging elements  15 A and  15 B and the permanent magnet  19  will be described. The permanent magnet  19  is fixed and arranged inside the capsule-shaped casing  12  in a state of being relatively fixed with respect to the above-described imaging units  11 A and  11 B. More particularly, the permanent magnet  19  is arranged so that the magnetization direction thereof is relatively fixed with respect to the up-and-down direction of the imaging surface of each of the imaging elements  15 A and  15 B. Specifically, as illustrated in  FIG. 6 , the permanent magnet  19  is arranged so that a magnetization direction Ym thereof becomes parallel to an up-and-down direction Yu of the imaging surfaces of the imaging elements  15 A and  15 B. 
       FIG. 7  is a conceptual diagram for explaining a situation of the capsule endoscope  10  when a liquid W is introduced into the subject  101 . Here,  FIG. 7  illustrates a state in which the magnetic field for controlling the position, the tilt angle and the azimuth angle of the capsule endoscope  10  does not act on the permanent magnet  19 . 
     The capsule endoscope  10  exemplified in the first embodiment is designed so that the specific gravity to the liquid W becomes nearly 1. Also, a gravity center G of the capsule endoscope  10  is set so as to be positioned off a geometric center C of the capsule endoscope  10  along the long axis La of the capsule endoscope  10  (the central axis in the longitudinal direction of the capsule endoscope  10 : see  FIG. 5 ). Specifically, the gravity center G of the capsule endoscope  10  is set at a position that is on the long axis La and off the geometric center C of the capsule-shaped casing  12  toward the imaging unit  11 B side by adjusting the position of the components such as the power source unit  18  and the permanent magnet  19 . Accordingly, the capsule endoscope  10  floats in the liquid W in a state where the long axis La thereof becomes substantially parallel to the vertical direction (that is, the gravity direction). In other words, the capsule endoscope  10  floats in the liquid W in a state where the line connecting the geometric center C and the gravity center G is upright. In such an upright posture, the capsule endoscope  10  directs the imaging visual field of the imaging unit  11 A vertically upward, while directing the imaging visual field of the imaging unit  11 B vertically downward. Here, the liquid W is a liquid that is harmless to the human body, such as water and a physiological salt solution. 
     Also, as described above, the permanent magnet  19  is arranged such that the magnetization direction Ym thereof (see  FIG. 6 ) is orthogonal to the long axis La. That is, the magnetization direction Ym of the permanent magnet  19  coincides with the radial direction of the capsule endoscope  10 . Therefore, when the magnetic field for controlling the position, the tilt angle and the azimuth angle of the capsule endoscope  10  does not act on the permanent magnet  19 , the capsule endoscope  10  floats in the liquid W in a state where the magnetization direction Ym coincides with the horizontal direction. Also, at this time, the plane which passes the magnetization direction Ym and the line connecting the geometric center C and the gravity center G of the capsule-shaped casing  12  comes to be a vertical plane. 
       FIG. 8  is a conceptual diagram for explaining a situation of the capsule endoscope  10  in a state where the liquid W is introduced into the subject  101 , and illustrates a state in which the magnetic field for controlling the tilt angle and the azimuth angle of the capsule endoscope  10  acts on the permanent magnet  19 . 
     As illustrated in  FIG. 8 , the tilt of the long axis La of the capsule endoscope  10  to a gravity direction Dg can be controlled by permitting the magnetic field to act on the permanent magnet  19  of the capsule endoscope  10  from the outside. For example, by permitting the magnetic field having a magnetic force line direction that has an angle with respect to the horizontal plane to act on the permanent magnet  19 , the capsule endoscope  10  can be tilted with respect to the gravity direction Dg so that the magnetization direction Ym of the permanent magnet  19  is substantially parallel to this magnetic force line. In this case, the tilt angle of the capsule endoscope  10  changes while the magnetization direction Ym maintains the state of being contained in the vertical plane. The magnetic field that performs such control is achieved when the elevation angle changing unit  25   d  of the guidance device  20  rotates the extracorporeal permanent magnet  25   a  (see  FIG. 1  and  FIG. 4 ). 
     Therefore, by applying the magnetic field that revolves around the gravity direction Dg with the capsule endoscope  10  tilted so that the capsule endoscope  10  revolves around the gravity direction Dg as indicated by an arrow, in-vivo images around the capsule endoscope  10  can be easily acquired. The magnetic field that performs such control is achieved when the revolution angle changing unit  25   e  of the guidance device  20  revolves the extracorporeal permanent magnet  25   a  (see  FIG. 1  and  FIG. 4 ). 
     At this time, the display unit  23   a  of the guidance device  20  displays an in-vivo image of the subject  101  by the capsule endoscope  10 , in a display mode in which the up-and-down direction of the imaging subject in the in-vivo image associated with the magnetic guidance of the capsule endoscope  10  is the same as the up-and-down direction of the display screen. As a result, as illustrated in  FIG. 9 , on a display screen M of the display unit  23   a , a liquid surface Ws imaged by an element in an upper region Pu of the imaging element  15 A of the capsule endoscope  10  is displayed in the upper portion of the image corresponding to the imaging unit  11 A. Furthermore, since the magnetization direction Ym of the permanent magnet  19  is parallel to the up-and-down direction Yu of the imaging surfaces of the imaging elements  15 A and  15 B, the direction parallel to the magnetization direction Ym of the permanent magnet  19  coincides with the up-and-down direction of the display screen of the display unit  23   a.    
     As illustrated in  FIGS. 10A and 10B , the translational movement in the horizontal direction of the capsule endoscope  10  can be controlled by permitting a magnetic field having a peak of the magnetic field strength in the direction vertical to the capsule facing plane PL1 (see  FIG. 10A ) to act on the permanent magnet  19  of the capsule endoscope  10  so as to attract the permanent magnet  19  to the peak position of the magnetic field to confine the capsule endoscope  10  (see  FIG. 10B ). Specifically, such a magnetic field is achieved when the plane position changing unit  25   b  of the guidance device  20  moves the extracorporeal permanent magnet  25   a  within the horizontal plane. 
     As illustrated in  FIGS. 11A and 11B , the translational movement in the vertical direction of the capsule endoscope  10  can be controlled by permitting a magnetic field having a distribution of the magnetic field strength that changes in accordance to the distance in the direction orthogonal to the capsule facing plane PL1 to acts on the permanent magnet  19  of the capsule endoscope  10 . Specifically, such a magnetic field is achieved when the vertical position changing unit  25   c  of the guidance device  20  moves the extracorporeal permanent magnet  25   a  in the vertical direction. 
     For example, as illustrated in  FIG. 11A , when the capsule facing plane PL1 is set to be horizontal, a magnetic field having a magnetic strength that becomes weaker as the vertical position is higher acts on the permanent magnet  19 . At this time, as illustrated in  FIG. 11B , when the extracorporeal permanent magnet  25   a  is moved upward to relatively lower the vertical position of the permanent magnet  19 , the magnetic attracting force applied to the permanent magnet  19  becomes stronger so that the capsule endoscope  10  is biased downward. Here, the position in the vertical direction of the capsule endoscope  10  is nearly maintained at a position where the buoyancy of the capsule endoscope  10  to the liquid W, the gravity applied to the capsule endoscope  10 , and the magnetic attracting force applied by the extracorporeal permanent magnet  25   a  are balanced. 
     Next, the specific configuration and action of the operation input unit  24  illustrated in  FIG. 1  will be described.  FIG. 12A  is a front view of the operation input unit  24 , and  FIG. 12B  is a right side view of the operation input unit  24 .  FIG. 13  is a diagram illustrating a motion of the capsule endoscope  10  that is instructed by an operation of each component of the operation input unit  24 . 
     As illustrated in  FIG. 12A , the operation input unit  24  includes two joy sticks  61  and  62  for three-dimensionally operating the magnetic guidance of the capsule endoscope  10  by the magnetic field generating unit  25 . The joy sticks  61  and  62  each can perform a tilting operation in the up-and-down direction and the left-and-right direction. 
     As illustrated in  FIG. 12B , an up button  64 U and a down button  64 B are disposed on the back surface of the joy stick  61 . The up button  64 U is pressed to input guidance instruction information instructing the upward guidance of the capsule endoscope  10  to the control unit  28 , and the down button  64 B is pressed to input guidance instruction information instructing the downward guidance of the capsule endoscope  10  to the control unit  28 . A capture button  65  is disposed on the top of the joy stick  61 . The capture button  65  is pressed to capture an in-vivo image displayed on the display unit  23   a . Also, an approach button  66  is disposed on the top of the joy stick  62 . The approach button  66  is pressed to input guidance instruction information for guiding the capsule endoscope  10  so that the imaging unit  11 A side of the capsule endoscope  10  is closer to the imaging object of the imaging unit  11 A, to the control unit  28 . 
     As illustrated in  FIG. 12A , the tilting direction in the up-and-down direction indicated by an arrow Y11j of the joy stick  61  corresponds to a tilting guidance direction in which the distal end of the capsule endoscope  10  swing so as to pass through a vertical axis Az as indicated by an arrow Y11 of  FIG. 13 . When the guidance instruction information corresponding to the tilting operation of the arrow Y11j of the joy stick  61  is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this guidance instruction information, the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  61 , and calculates a guidance amount in accordance with the tilting operation of the joy stick  61 . Then, the magnetic field generating unit  25 , for example, controls the elevation angle changing unit  25   d  to rotate the extracorporeal permanent magnet  25   a  in the calculated guidance direction in accordance with the calculated guidance amount. 
     As illustrated in  FIG. 12A , the tilting direction in the left-and-right direction indicated by an arrow Y12j of the joy stick  61  corresponds to a rotation guidance direction in which the capsule endoscope  10  rotates around the vertical axis Az as indicated by an arrow Y12 of  FIG. 13 . When the guidance instruction information corresponding to the tilting operation of the arrow Y12j of the joy stick  61  is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this guidance instruction information, the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  61 , and calculates the guidance amount in accordance with the tilting operation of the joy stick  61 . Furthermore, the control unit  28 , for example, controls the revolution angle changing unit  25   e  to revolve the extracorporeal permanent magnet  25   a  in the calculated guidance direction in accordance with the calculated guidance amount. 
     As illustrated in  FIG. 12A , the tilting direction in the up-and-down direction of the joy stick  62  as indicated by an arrow Y13j corresponds to a horizontal backward guidance direction or a horizontal forward guidance direction both proceeding in a direction in which the long axis La of the capsule endoscope  10  is projected on a horizontal plane Hp as indicated by an arrow Y13 of  FIG. 13 . When the guidance instruction information corresponding to the tilting operation of the arrow Y13j of the joy stick  62  is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this guidance instruction information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  62 . Then, the control unit  28  controls the plane position changing unit  25   b  to translate the extracorporeal permanent magnet  25   a  in accordance with the calculated guidance direction and guidance amount. 
     As illustrated in  FIG. 12A , the tilting direction in the left-and-right direction of the joy stick  62  as indicated by an arrow Y14j corresponds to a horizontal right guidance direction or a horizontal left guidance direction in which the capsule endoscope  10  proceeds on the horizontal plane Hp vertically to a direction in which the long axis La is projected on the horizontal plane Hp as indicated by an arrow Y14 of  FIG. 13 . When the guidance instruction information corresponding to the tilting operation of the arrow Y14j of the joy stick  62  is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this guidance instruction information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  62 . Then, the control unit  28  controls the plane position changing unit  25   b  to translate the extracorporeal permanent magnet  25   a  in accordance with the calculated guidance direction and guidance amount. 
     Also, the up button  64 U and the down button  64 B are disposed on the back surface of the joy stick  61 . As indicated by an arrow Y15j of  FIG. 12B , when the up button  64 U is pressed, an up action of proceeding upward as indicated by an arrow Y15 along the vertical axis Az illustrated in  FIG. 13  is instructed. Also, as indicated by an arrow Y16j of  FIG. 12B , when the down button  64 B is pressed, a down action of proceeding downward as indicated by an arrow Y16 along the vertical axis Az illustrated in  FIG. 13  is instructed. When the guidance instruction information corresponding to the pressing operation of the arrow Y15j or Y16j of the up button  64 U or the down button  64 B is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this guidance instruction information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the pressed button. Then, the control unit  28  controls the vertical position changing unit  25   c  to translate the extracorporeal permanent magnet  25   a  in the vertical direction in accordance with the calculated guidance direction and guidance amount. For example, when the up button  64 U is pressed, the vertical position changing unit  25   c  translates the extracorporeal permanent magnet  25   a  toward the lower direction of the vertical axis Az (the direction away from the capsule endoscope  10 ). Accordingly, the capsule endoscope  10  moves upward as indicated by the arrow Y15. On the other hand, when the down button  64 B is pressed, the vertical position changing unit  25   c  translates the extracorporeal permanent magnet  25   a  toward the upper direction of the vertical axis Az (the direction closer to the capsule endoscope  10 ). Accordingly, the capsule endoscope  10  moves downward as indicated by the arrow Y16. 
     Here, the operation input unit  24  may further have an input device including various operation buttons and keyboards as well as the above-described joy sticks  61  and  62 . 
       FIG. 14  is a schematic diagram illustrating a display example of a menu screen S displayed on the display unit  23   a . On this menu screen S, various subject information such as patient name, patient ID, birth date, sex and age of the subject  101  is displayed in a region S1 in the upper left; a living body image Sg1 taken by the imaging unit  11 A is displayed on the left side in a region S2 in the center; a living body image Sg2 taken by the imaging unit  11 B is displayed on the right side; images captured by the pressing operation of the capture button  65  are displayed in a reduced manner along with capture times in a region S3 below the region S2; and a posture diagram Sg3 on the vertical plane and a posture diagram Sg4 on the horizontal plane are displayed as posture diagrams of the capsule endoscope  10  in a region S4 on the left side. The tilt angle and the azimuth angle of the capsule endoscope  10  displayed on the posture diagrams Sg3 and Sg4 indicate the tilt angle and the azimuth angle corresponding to the guidance instruction information of the operation input unit  24 . In the first embodiment, since the input amount from the operation input unit  24  is reflected on a guiding force, the displayed tilt angle and azimuth angle of the capsule endoscope  10  can be considered as being substantially equal to the actual tilt angle and azimuth angle of the capsule endoscope  10 , and the guidance instruction assistance to an operator is also improved. Here, the directions in which the capsule endoscope  10  can be guided are indicated by arrows in these posture diagrams Sg3 and Sg4. When operation of one of the guidance directions is input, the display color of the arrow corresponding to the input direction is changed to assist an operation by an operator. 
     Next, the action of the guidance system  1  illustrated in  FIG. 1  will be described.  FIG. 15  is a flow chart illustrating the action of the guidance system  1 . 
     When the capsule medical apparatus guidance system  1  is started, firstly, in step S 101 , the control unit  28  of the guidance device  20  checks, from the output result of the shielding state detector  27 , that the guidance device  20  is in the magnetic field shielding state (see  FIG. 3 ). 
     In subsequent step S 102 , the control unit  28  checks that the extracorporeal permanent magnet  25   a  is arranged at a position (an initial position) where the magnetic field strength is minimum in the effective magnetic field area  100 . Here, when the extracorporeal permanent magnet  25   a  is not in the initial position, the control unit  28  controls the vertical position changing unit  25   c  to move the extracorporeal permanent magnet  25   a  to the initial position. 
     In step S 103 , when a signal indicating that the subject  101  has been placed on the bed  20   a  is input from the operation input unit  24 , the control unit  28  recognizes that the subject  101  has been placed on the bed  20   a . This signal may be input by a specified user operation (for example, pressing of a bed placement check button). Alternatively, the input may be performed when the bed  20   a  becomes in a specified state (for example, when a pressure sensor disposed on the subject placing surface of the bed  20   a  has an output value of higher than a specified threshold value). 
     In step S 104 , when the power source of the capsule endoscope  10  is turned on, the guidance device  20  receives a wireless signal transmitted from the capsule endoscope  10 , and checks that an image taken by the capsule endoscope  10  can be acquired. Here, turning on the capsule endoscope  10  is achieved by turning on a magnetic switch or an optical switch of the power source unit  18  arranged in the capsule endoscope  10 . That is, the magnetism or the light for activating the magnetic switch or the optical switch is applied from the outside. 
     In step S 105 , when a signal indicating that the capsule endoscope  10  has been swallowed by the subject  101  is input from the operation input unit  24 , the control unit  28  recognizes that the capsule endoscope  10  has been swallowed by the subject  101 . This signal may be input by a specified user operation (for example, pressing of a capsule swallowing check button). Alternatively, the signal may be input when image data transmitted from the capsule endoscope  10  becomes in a specified state (for example, in a specified state indicating that the color characteristic amount of an image is in the body). 
     In step S 106 , when a signal indicating the start of an examination is input from the operation input unit  24 , the control unit  28  controls each component to shift the guidance device  20  to the magnetic field generating state. This signal indicating the start of an examination may be input by, for example, one action such as pressing of a specified button (for example, an examination start button) of the operation input unit  24 , or an operation by the joy sticks  61  and  62 , or the like. 
     Accordingly, the magnetic body member  26   a  arranged between the magnetic field generating unit  25  and the effective magnetic field area  100  is removed, and the guidance device  20  becomes in the magnetic field generating state. At this time, since the magnetic field generating unit  25  is in the initial position (see step S 102 ), the strength of the magnetic field to be generated to the effective magnetic field area  100  comes to be minimum. Accordingly, the magnetic field having a high strength can be inhibited from being rapidly applied to the capsule endoscope  10 . Hereinafter, the magnetic field generating state in which the magnetic field generating unit  25  is in the initial position (see  FIG. 16 ) is referred to as a weak magnetic field generating state. 
     In step S 107 , the control unit  28  receives information (for example, the body position information of the subject  101 , such as decubitus left) input from the operation input unit  24 , and causes the display unit  23   a  to display the received information. At this time, the control unit  28  may acquire a relative coordinate system in the subject  101  based on the received information and the absolute coordinate system (the coordinate system based on the gravity direction) of the capsule endoscope  10 , and perform calculation processing of estimating an observation direction and an observation region within the subject  101  based on the relative coordinate system. 
     In step S 108 , the control unit  28  starts guidance of the capsule endoscope  10 , and controls the position, the elevation angle θ and the revolution angle ψ of the extracorporeal permanent magnet  25   a  in accordance with guidance instruction information input from the operation input unit  24 . Here, at this time, the extracorporeal permanent magnet  25   a  is moved upward higher than the initial position, so that the magnetic field having a higher strength comes to be formed to the effective magnetic field area  100 . Accordingly, the guidance device  20  is shifted from the weak magnetic field generating state to the normal magnetic field generating state. 
     In step S 109 , the control unit  28  sequentially receives a wireless signal transmitted from the capsule endoscope  10 , and controls an image taken by the capsule endoscope  10  to be displayed on the display unit  23   a . A user operates the operation input unit  24  while referring to the image, thereby enabling the capsule endoscope  10  to be guided to a desired position, tilt angle and azimuth angle. 
     Here, a user may change the body position of the subject  101  as necessary. In this case, by performing a specified operation to the operation input unit  24 , such as pressing of the operation button and input of the posture information through a keyboard or the like, a signal indicating that the body position of the subject  101  has been changed can be input into the guidance device  20 . When the signal indicating that the body position of the subject  101  has been changed is input from the operation input unit  24 , the control unit  28  controls the extracorporeal permanent magnet  25   a  to temporarily return to the initial position and become in a weak magnetic field generating state. Accordingly, the magnetic field having a high strength can be inhibited from being rapidly applied to the capsule endoscope  10  after the change of a body position. 
     In step S 110 , the control unit  28  determines whether or not an emergency stop trigger has been turned on. Here, the emergency stop trigger may be, for example, an emergency stop signal that is input from the operation input unit  24  in response to the pressing of a specified button (an emergency stop button), or may be a signal indicating that the placement of the subject  101  temporarily recognized in step S 103  has come not to be recognized (for example, a decrease in the output value of the pressure sensor disposed on the subject placing surface). Besides, the detection of vibration caused by an earthquake or the like, or the rapid voltage drop in the guidance device  20  may be used as the emergency stop trigger. 
     When the emergency stop trigger has been turned on (step S 110 : Yes), the control unit  28  allows the display unit  23   a  and the notifying unit  23   b  to execute notification indicating that an emergency stop trigger has been turned on, and controls the shielding unit  26  so that the guidance device  20  is shifted to the magnetic field shielding state (emergency shielding) (step S 111 ). As a specific notification method, a warning by visual information like “Emergency stop is executed” may be displayed on the display unit  23   a ; the notifying unit  23   b  may execute a warning by another visual information like the flashing of illumination or a warning by auditory information like voice or a warning sound; or both of these may be executed. Thereafter, the action of the guidance system  1  proceeds to step S 116 . On the other hand, when the emergency stop trigger is not turned on (step S 110 : No), the action of the guidance system  1  proceeds to step S 112 . 
     In step S 112 , the control unit  28  determines whether or not a signal indicating that the acquisition of all images has been completed has been input from the operation input unit  24 . This signal may be input by a specified user operation (for example, pressing of an image acquisition completion button or a guidance stop button). Alternatively, the signal may be input when the number of images received from the capsule endoscope  10  has reached a specified amount, or when a specified time has elapsed after the power source of the capsule endoscope  10  was turned on. 
     When the acquisition of all images has been completed (step S 112 : Yes), the control unit  28  allows the action of the magnetic field generating unit  25  to be stopped so as to stop the guidance of the capsule endoscope  10 . At the same time, the extracorporeal permanent magnet  25   a  is returned to the initial position to shift the guidance device  20  to the weak magnetic field generating state (step S 113 ). 
     On the other hand, when all images have not yet acquired (step S 112 : No), the control unit  28  determines whether or not the body position information has been newly input from the operation input unit  24  (step S 114 ). When the body position information has been newly input (step S 114 : Yes), the control unit  28  allows the extracorporeal permanent magnet  25   a  to return to the initial position to shift the guidance device  20  to the weak magnetic field generating state (step S 115 ). Thereafter, the action of the guidance system  1  proceeds to step S 109 . On the other hand, when the body position information is not newly input (step S 114 : No), the action of the guidance system  1  directly proceeds to step S 109 . 
     In step S 116 , the control unit  28  controls the shielding unit  26  so that the guidance device  20  is shifted to the magnetic field shielding state. Accordingly, the action of the guidance system  1  is stopped. Thereafter, a user prompts the subject  101  to leave the bed  20   a.    
     Here, although in the above description, the shifting between the magnetic field generating state and the magnetic field shielding state is performed by the shielding unit  26  under control of the control unit  28 , a user may manually move the magnetic body member  26   a  to perform this shifting. 
     Next, the condition for the shape of the extracorporeal permanent magnet  25   a  will be described. 
     The inventors calculated the relationship between the shape (the ratio among length, width and height) of a permanent magnet and the generated magnetic field by simulation, in order to efficiently generate a magnetic field for guiding the capsule endoscope  10  from the extracorporeal permanent magnet  25   a .  FIG. 17  is a schematic diagram for explaining the evaluation items in this simulation. As illustrated in  FIG. 17 , in the present simulation, a magnetization direction of a permanent magnet was set in an x-axis direction; a direction orthogonal to the magnetization direction on the plane PL2 facing a simulation position was set in a y-axis direction; and a direction orthogonal to the plane PL2 was set in a z-axis direction. Then, the magnetic field strength in the simulation position, and the magnetic field gradients in the z-axis direction, the x-axis direction and the y-axis direction in the simulation position were evaluated. Here, the magnetic strength is involved in the guidance when changing the tilt angle and the azimuth angle of the capsule endoscope  10 . The magnetic field gradient in the z-axis direction is involved in the guidance in the z-axis direction of the capsule endoscope  10 . The magnetic field gradient in the x-axis direction is involved in the guidance in the x-axis direction of the capsule endoscope  10 . The magnetic field gradient in the y-axis direction is involved in the guidance in the y-axis direction of the capsule endoscope  10 . 
     Also, in the present simulation, a permanent magnet having a rectangular parallelepiped shape (including a cube) was used.  FIG. 18  is a table illustrating the ratio in length among sides of a permanent magnet used in the simulation. As illustrated in  FIG. 18 , a “length L x  in the x-axis direction” indicates a length L x  of a side parallel to the x-axis; a “length L y  in the y-axis direction” indicates a length L y  of a side parallel to the y-axis; and a “length L z  in the z-axis direction” indicates a length L z  of a side parallel to the z-axis (see  FIG. 17 ). Also, in the column of “type” in  FIG. 18 , the sides of each permanent magnet are indicated in a descending order of the length from the left. For example, type “x-y-z” indicates a rectangular parallelepiped shape in which a side parallel to the x-axis is the longest, and a side parallel to the z-axis is the shortest (L x &gt;L y &gt;L z ). Here, type “xyz” indicates a cube in which all sides have the same length (L x =L y =L z ). 
       FIG. 19  is a graph illustrating magnetic field strengths of the permanent magnets illustrated in  FIG. 18 .  FIG. 20  is a graph illustrating magnetic field gradients in the z-axis direction generated by the permanent magnets illustrated in  FIG. 18 .  FIG. 21  is a graph illustrating magnetic field gradients in the x-axis direction generated by the permanent magnets illustrated in  FIG. 18 .  FIG. 22  is a graph illustrating magnetic field gradients in the y-axis direction generated by the permanent magnets illustrated in  FIG. 18 . Here, in  FIG. 19 , the values of the magnetic field strengths are normalized. Also, in  FIG. 20  to  FIG. 22 , the values of the magnetic field gradients are normalized. In  FIG. 21  and  FIG. 22 , the horizontal axis indicates the normalized value of the distance from the axis (central axis) in the z-axis direction passing through the center of the permanent magnet. 
     In order to efficiently control the tilt angle and the azimuth angle of the capsule endoscope  10 , the magnetic field strength generated by a permanent magnet is preferably high. In this regard, as illustrated in  FIG. 19 , a magnet with a relatively high magnetic field strength was type y-x-z and type x-y-z. Therefore, it can be seen that the shape suitable for the control of the tilt angle and the azimuth angle of the capsule endoscope  10  is a shape in which the length L z  in the z-axis direction is shorter than the length L y  in the y-axis direction. Furthermore, it can be said that a flat shape is more preferred in which the length L z  in the z-axis direction is shorter than the length L x  in the x-axis direction and the length L y  in the y-axis direction. 
     Also, when changing the tilt angle of the capsule endoscope  10  (that is, when rotating a permanent magnet around the axis parallel to the y-axis), a smaller projected area on the zx plane orthogonal to the y-axis is preferred so that the movement region of the permanent magnet during rotation can be reduced. Therefore, the length of L x  in the x-axis direction is favorably shorter. In this case, since the permanent magnet can be installed further closer to the subject  101 , the magnetic field having a high strength can be efficiency generated within the subject  101 , thereby enabling the magnetic field generating unit  25  to be miniaturized. 
     For performing position control in the vertical direction of the capsule endoscope  10 , the magnetic field gradient in the vertical direction is preferably large. In this regard, as illustrated in  FIG. 20 , a magnet with a relatively high magnetic field gradient in the z-axis direction was type y-x-z and type x-y-z. Therefore, it can be seen that the shape suitable for the position control in the vertical direction of the capsule endoscope  10  is a flat shape having a shorter length L z  in the z-axis direction. 
     For performing position control in the horizontal direction of the capsule endoscope  10 , the magnetic field gradient in the horizontal direction is preferably large. In this regard, as illustrated in  FIG. 21 , a magnet with a relatively high magnetic field gradient in the x-axis direction was type y-x-z and type y-z-x. Here, it was found that in the cases of type x-z-y and type x-y-z, the peak of the magnetic field gradient is formed at a position away from the permanent magnet. Also, as illustrated in  FIG. 22 , a magnet with a relatively high magnetic field gradient in the y-axis direction was type y-x-z and type x-y-z. Thus, it can be seen that the shape suitable for the control in the horizontal direction of the capsule endoscope  10  is a shape in which the length L y  in the y-axis direction is longer compared to the length L x  in the x-axis direction and the length L z  in the z-axis direction. Also, it can be said that the length L x  in the x-axis direction is preferably not much longer compared to the length L y  in the y-axis direction and the length L z  in the z-axis direction. 
     From the results of the above-described simulation, it was found that the shape of the extracorporeal permanent magnet  25   a  suitable for the control of the capsule endoscope  10  is a flat plate shape in which the length in the y-axis direction is the longest while the length in the z-axis direction is the shortest. Then, the present inventors subsequently performed another simulation for calculating a suitable ratio among the lengths of the sides of the extracorporeal permanent magnet  25   a.    
       FIG. 23  is a table illustrating a ratio in length among sides of a permanent magnet used in another simulation. As illustrated in  FIG. 23 , a “length L x  in the x-axis direction” corresponds to a length L x  of a side parallel to the x-axis (a magnetization direction); a “length L y  in the y-axis direction” corresponds to a length L y  of a side parallel to the y-axis; and a “length L z  in the z-axis direction” corresponds to a length L z  of a side parallel to the z-axis (see  FIG. 17 ). Also, in the column of “type” in  FIG. 23 , the sides of each permanent magnet are indicated in a descending order of the length from the left, and the numerical value in a parenthesis indicates the ratio of the length of the z-axis direction to the length of the x-axis direction. As illustrated in  FIG. 23 , in this simulation, all of the permanent magnets have a rectangular parallelepiped shape in which the side parallel to the y-axis direction is the longest while the side parallel to the z-axis direction is the shortest. 
       FIG. 24  is a graph illustrating magnetic field strengths of the permanent magnets illustrated in  FIG. 23 .  FIG. 25  is a graph illustrating magnetic field gradients in the z-axis direction generated by the permanent magnets illustrated in  FIG. 23 .  FIG. 26  is a graph illustrating magnetic field gradients in the x-axis direction generated by the permanent magnets illustrated in  FIG. 23 .  FIG. 27  is a graph illustrating magnetic field gradients in the y-axis direction generated by the permanent magnets illustrated in  FIG. 23 . Here, in  FIG. 24 , the values of the magnetic field strengths are normalized. Also, in  FIG. 25  to  FIG. 27 , the values of the magnetic field gradients are normalized. In  FIG. 26  and  FIG. 27 , the horizontal axis indicates the normalized value of the distance from the axis (central axis) in the z-axis direction passing through the center of the permanent magnet. 
     As illustrated in  FIG. 24  and  FIG. 25 , all of the permanent magnets had a favorable result in terms of the magnetic field strength and the magnetic field gradient in the z-axis direction. This result shows that the effect obtained by changing the ratio of the lengths of the sides of a permanent magnet is small. 
     On the other hand, as illustrated in  FIG. 26 , it can be seen that as the length L y  in the y-axis direction is longer compared to the length L z  in the z-axis direction of the permanent magnet (for example, type y-x-z(33) and type Y-x-z(50)), the magnetic field gradient in the x-axis direction significantly improves. On the other hand, in this case, it can be seen that when this ratio is extreme (for example, type y-x-z(33)), as illustrated in  FIG. 27 , the magnetic field gradient in the y-axis direction deteriorates. However, since the value of the magnetic field gradient in the x-axis direction is smaller compared to that of the magnetic field gradient in the y-axis direction, the ratio between the length L y  in the y-axis direction and the length L z  in the z-axis direction may be determined in consideration of the balance among the magnetic field gradients in the axis directions. 
       FIG. 28  is a graph illustrating the relationship between the ratio L y /L z  of the length L y  in the y-axis direction to the length L z  in the z-axis direction, and the ratio of the magnetic field strength of the permanent magnet having each of the above-described ratios to the magnetic field strength of the permanent magnet of type y-x-z(33). As illustrated in  FIG. 28 , when the length L y  in the y-axis direction to the length L z  in the z-axis direction becomes 1.5 times, the magnetic field strength of approximately 90% of the magnetic field strength generated by the permanent magnet of type y-x-z(33) which is the permanent magnet having a sufficiently long length L y  to the length of L z  can be generated. Furthermore, when the length L y  in the y-axis direction to the length L z  in the z-axis direction becomes 3 times or more, the above-described ratio of the magnetic field strength comes to be 95%. Therefore, a preferred shape of the permanent magnet may be a shape in which the length L y  in the y-axis direction to the length L z  in the z-axis direction is 1.5 times or more, or 3 times or more. 
     Based on the above results of the simulation, the shape of the extracorporeal permanent magnet  25   a  was focused on a shape in which the length L y  in the y-axis direction is the longest (L y &gt;L x  and L y &gt;L z ). Then, further detailed simulation was conducted. 
       FIG. 29  is a table illustrating a ratio in length among the sides of the permanent magnet used in the present simulation. As illustrated in  FIG. 29 , a “length L x  in the x-axis direction” corresponds to a length L x  of a side parallel to the x-axis (the magnetization direction); a “length L y  in the y-axis direction” corresponds to a length L y  of a side parallel to the y-axis; and a “length L z  in the z-axis direction” corresponds to a length L z  of a side parallel to the z-axis (see  FIG. 17 ). Also, as illustrated in  FIG. 29 , types A1 to A3 are indicated as having a length L x  of 100; types B1 to B3 are indicated as having a length L x  of 50; and types C1 to C3 are indicated as having a length L x  of 25. Furthermore, a value K indicated in the bottom line of  FIG. 29  is a value representing the characteristics of the shape of the permanent magnet, and is defined with the lengths L x , L y  and L z  as below: 
     
       
         
           
             K 
             = 
             
               
                 
                   L 
                   y 
                   2 
                 
                 
                   
                     L 
                     x 
                   
                   × 
                   
                     L 
                     z 
                   
                 
               
             
           
         
       
     
       FIG. 30  is a graph illustrating a relationship between the length L z  in the z-axis direction and the magnetic field strength of each of the permanent magnets illustrated in  FIG. 29 .  FIG. 31  is a graph illustrating a relationship between the length L z  of each of the permanent magnets illustrated in  FIG. 29  and the magnetic field gradient in the z-axis direction.  FIG. 32  is a graph illustrating a relationship between the length L z  of each of the permanent magnets illustrated in  FIG. 29  and the magnetic field gradient in the x-axis direction.  FIG. 33  is a graph illustrating a relationship between the length L z  of each of the permanent magnets illustrated in  FIG. 29  and the magnetic field gradient in the y-axis direction. Here, in  FIG. 30 , the values of the magnetic field strengths are normalized. Also, in  FIG. 31  to  FIG. 33 , the values of the magnetic field gradients are normalized. 
       FIG. 34  is a table illustrating the results indicated in  FIG. 30  to  FIG. 33 , and the magnetic field strength or the magnetic field gradients in the x-axis, the y-axis and the z-axis are evaluated and classified into three ranks of large, moderate and small. Here, in  FIG. 34 , for each of the evaluation items, evaluation as large is indicated by a “double circle” symbol; evaluation as moderate is indicated by a “circle” symbol; and evaluation as small is indicated by a “triangle” symbol. 
     From  FIG. 34 , the permanent magnets of types A3, B2 and C1 do not contain “small (triangle)” in the evaluation results of all items, and have a favorable balance among the magnetic field strength and the magnetic field gradients in the x-axis, y-axis and z-axis. Thus, it can be said that a magnetic field is efficiently generated. Conversely, the permanent magnet of type C3 is evaluated as large (double circle) only in the magnetic field gradient of the x-axis direction, and is evaluated as small (triangle) in other items. Thus, it can be said that the generation efficiency of a magnetic field is significantly low. It can be said that the efficiency of the magnetic field caused by the permanent magnet of type (A1, A2, B1, B3 and C2) other than the above is between types A3, B2 and C1, and type C3. 
     From these results, it can be said that the shape of a permanent magnet that can efficiently generate a magnetic field has a K value higher than 1.0 and 22.6 or lower (1&lt;K≦22.6). 
     Also, in comparison among the permanent magnets of types A3, B2 and C1, when the length L x  in the x-axis direction becomes shorter with respect to the length L z  in the z-axis direction, the magnetic field strength, the magnetic field gradient in the z-axis direction, and the magnetic field gradient in the y-axis direction are decreased. Therefore, the length L x  in the x-axis direction is preferably not much shorter compared to the length L z  in the z-axis direction. 
     From the above, the condition for the aspect ratio for efficiently generating a magnetic field for guiding the capsule endoscope  10  from the extracorporeal permanent magnet  25   a  is as below. That is, the range of the K value may be 1&lt;K≦22.6, and preferably, the K value may be around 8. Also, the length L x  in the x-axis direction may be the length L z  in the z-axis direction or longer (L x ≧L z ). 
     As described above, according to the first embodiment, by using the extracorporeal permanent magnet  25   a  having the above-described condition, the guidance device  20  that can generate a magnetic field suitable for guiding the capsule endoscope  10  can be achieved. 
     Also, according to the first embodiment, since the shielding unit  26  that slides the magnetic body member  26   a  is disposed in the guidance device  20 , a user can easily and quickly shift the guidance device  20  between the magnetic field generating state and the magnetic field shielding state by a simple input operation to the operation input unit  24  or manually. 
     Also, according to the first embodiment, since the state of the guidance device  20  is shifted by a simple operation in accordance with the status of the capsule endoscope examination, the examination can be safely performed. For instance, since the guidance device  20  is shifted to the magnetic field generating state after the start of an examination, a risk of unintentionally attracting a metal member to a magnetic field before and after the start of an examination can be inhibited. Also, for example, since the magnetic field strength is in the lowest state immediately after the shifting of the guidance device  20  to the magnetic field generating state, a risk of allowing a magnetic field having a high strength to be suddenly applied to the subject  101  can be prevented. 
     Also, according to the first embodiment, when the body position of the subject  101  is changed at the start of an examination or after the start of an examination, the extracorporeal permanent magnet  25   a  is returned to the initial position to shift the guidance device  20  to the weak magnetic field generating state. Accordingly, a situation can be prevented in which a magnetic field having a high strength is applied to the capsule endoscope  10  resulting in the movement of the capsule endoscope  10  to the position not expected by a user. 
     Also, according to the first embodiment, the capsule endoscope  10  is guided in a state where the capsule endoscope  10  floats in a liquid in which a liquid is introduced into the subject  101 . For this reason, the magnetic field generating unit  25  for guiding the capsule endoscope  10  can be placed under the bed  20   a  on which the subject  101  is placed. Thus, the whole capsule medical apparatus guidance system can be miniaturized. 
     Here, although in the first embodiment described above, a pantoscopic capsule in which the imaging units  11 A and  11 B are disposed on the both sides of the capsule endoscope  10  is used, a monocular capsule in which an imaging unit is disposed on one end of the capsule endoscope may be used. In this case, by positioning the gravity center G of the capsule endoscope closer to the end on a side where the imaging unit is disposed, a capsule endoscope that takes only an image under a water surface (in water) can be achieved. On the other hand, by positioning the gravity center G of the capsule endoscope closer to the end on a side where the imaging unit is not disposed, a capsule endoscope that takes only a space above a water surface can be achieved. 
     Also, although in the first embodiment described above, the permanent magnet  19  is arranged such that the magnetization direction Ym is orthogonal to the long axis La of the capsule endoscope  10  (see  FIG. 6 ), the permanent magnet  19  may be arranged such that the magnetization direction Ym coincides with the direction of the long axis La. At this time, the gravity center G may be positioned off the geometric center C of the capsule endoscope  10  in the radial direction. In this case, the posture of the capsule endoscope  10  can be uniquely controlled in the liquid W. 
     Also, in the first embodiment described above, in a state where a magnetic field is not applied, the gravity center G is positioned on the long axis La so that the capsule endoscope  10  floats with the long axis La directed in the vertical direction (see  FIG. 7 ). However, the gravity center G may be positioned off the long axis La so that the capsule endoscope  10  floats with the long axis La tilted with respect to the vertical direction in a state where a magnetic field is not applied. In this case, the tilt angle and the azimuth angle of the capsule endoscope  10  can be uniquely controlled in the liquid W. 
     Alternatively, the gravity center G of the capsule endoscope  10  may be positioned off the geometric center C toward a direction different from the magnetization direction of the permanent magnet  19 . In this case, the tilt angle and the azimuth angle of the capsule endoscope  10  can also be uniquely controlled in the liquid W. 
     Also, although in the first embodiment described above, a magnetic field for guiding the capsule endoscope  10  introduced into the subject  101  is generated by the magnetic field generating unit  25 , a magnetic field that variously acts on the capsule endoscope  10  other than the above may be generated. For example, the magnetic field generating unit  25  may remotely perform on/off of a magnetic switch incorporated in the capsule endoscope  10 . 
     Although in the first embodiment described above, the extracorporeal permanent magnet  25   a  included in the guidance device  20  has a rectangular parallelepiped shape, a permanent magnet having various shapes other than the rectangular parallelepiped shape, such as a polygonal column shape, a disk (or oval disk) shape, a frustum shape, or a shape similar to these may be employed as long as a permanent magnet whose length in the first direction orthogonal to the magnetization direction is longer than the length of the magnetization direction can be configured to confine the capsule endoscope  10  within a region facing the first plane parallel to the first direction. Preferably, the length in the second direction orthogonal to the magnetization direction of the extracorporeal permanent magnet and the first direction may be shorter than the length in the first direction. Even in a case where the shape of the extracorporeal permanent magnet is other than the rectangular parallelepiped shape, the details of, for example, the condition for the lengths of the magnetization direction as well as the first and second directions are similar to those described in the first embodiment. If a permanent magnet having a disk shape or an oval disk shape is used, the lengths in the magnetization direction as well as the first and second directions may be defined by the diameter, or the length of the major axis or the minor axis. 
     Modified Example 1-1 
     Next, modified example 1-1 of the first embodiment will be described. 
       FIG. 35A  is a front view of the operation input unit  24  according to modified example 1-1;  FIG. 35B  is a right side view of the operation input unit  24 ; and  FIG. 36  is a diagram illustrating another example of the action content of the capsule endoscope  10  to be instructed by operation of each component of the operation input unit  24 . 
     Each operation of the operation input unit  24  and guidance operation of the capsule endoscope  10  may be corresponded to each other so that, as described below, the capsule endoscope  10  can be guided along a plane orthogonal to a long axis La of the capsule endoscope  10 , not along the horizontal plane Hp. Hereinafter, the movement of the capsule endoscope  10  corresponding to the guidance operation when guiding the capsule endoscope  10  along the plane orthogonal to the long axis La of the capsule endoscope  10  will be described. 
     As illustrated in  FIG. 35A , the tilting direction in the up-and-down direction indicated by an arrow Y23j of the joy stick  62  instructs, as illustrated in  FIG. 36 , a down guidance direction or an up guidance direction in which the capsule endoscope  10  proceeds as indicated by an arrow Y23 on a plane orthogonal to the long axis La. When the operation information corresponding to the tilting operation of the arrow Y23j of the joy stick  62  is input from the operation input unit  24  to the control unit  28 , the magnetic field generating unit  25  calculates, based on this operation information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  62 . Then, the magnetic field generating unit  25  controls the plane position changing unit  25   b  and the vertical position changing unit  25   c  to translate the extracorporeal permanent magnet  25   a  in accordance with the calculated guidance direction and guidance amount. 
     As illustrated in  FIG. 35A , the tilting direction in the left-and-right direction indicated by an arrow Y24j of the joy stick  62  instructs, as illustrated in  FIG. 36 , a right guidance direction or a left guidance direction in which the capsule endoscope  10  proceeds as indicated by an arrow Y24 on a plane orthogonal to the long axis La. When the operation information corresponding to the tilting operation of the arrow Y24j of the joy stick  62  is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this operation information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the tilting direction of the joy stick  62 . Then, the control unit  28  controls the plane position changing unit  25   b  to translate the extracorporeal permanent magnet  25   a  in accordance with the calculated guidance direction and guidance amount. 
     As illustrated in  FIG. 35B , the pressing of the up button  64 U or the down button  64 B as indicated by arrows Y25j and Y26j instructs, as illustrated in  FIG. 36 , a forward guidance direction or a backward guidance direction in which the capsule endoscope  10  proceeds forward or backward with respect to the imaging elements  15 A and  15 B as indicated by arrows Y25 and Y26 along the long axis La. When the operation information corresponding to the pressing operation of the arrow Y25j or Y26j of the up button  64 U or the down button  64 B is input from the operation input unit  24  to the control unit  28 , the control unit  28  calculates, based on this operation information, the guidance amount and the guidance direction on the absolute coordinate system for the distal end of the capsule endoscope  10  in accordance with the pressed button. Then, the control unit  28  controls the plane position changing unit  25   b  and the vertical position changing unit  25   c  to translate the extracorporeal permanent magnet  25   a  in accordance with the calculated guidance direction and the calculation amount. 
     Here, as illustrated in  FIG. 35A , the tilting direction in the up-and-down direction indicated by an arrow Y21j of the joy stick  61  corresponds to a tilting guidance direction in which the distal end of the capsule endoscope  10  swings so as to pass through a vertical axis Az as indicated by an arrow Y21 of  FIG. 36 . The tilting direction in the left-and-right direction indicated by an arrow Y22j of the joy stick  61  corresponds to a rotation guidance direction in which the capsule endoscope  10  rotates around the vertical axis Az as indicated by an arrow Y22 of  FIG. 36 . 
     Modified Example 1-2 
     Next, modified example 1-2 of the first embodiment will be described. 
     The position detection of the capsule endoscope  10  within the subject  101  may be performed not only by the method based on the strength of the wireless signal received from the capsule endoscope  10  described in the first embodiment, but also by other various methods. 
     For example, a method may be used in which the position of the capsule endoscope  10  is detected based on acceleration applied to the capsule endoscope  10 . In this case, an acceleration sensor that three-dimensionally detects the acceleration applied to the capsule endoscope  10  is disposed inside the capsule endoscope  10 , and the detection result of the acceleration sensor is superimposed on a wireless signal to be transmitted at any time. The guidance device  20  integrates the accelerations applied to the capsule endoscope  10  based on the detection result of the acceleration sensor superimposed on the received wireless signal to obtain the relative change amount of the position of the capsule endoscope  10 , and calculates the current position of the capsule endoscope  10  from this change amount. 
     Modified Example 1-3 
     Next, modified example 1-3 of the first embodiment will be described. 
     As the position detection method of the capsule endoscope  10  within the subject  101 , a method of detecting an AC magnetic field may be used. In this case, an AC magnetic field generation unit that generates an AC magnetic field is disposed inside the capsule endoscope  10 . On the other hand, a plurality of magnetic field sensors that detect an AC magnetic field is disposed on the guidance device  20  side. 
     The guidance device  20  detects an AC magnetic field generated by the capsule endoscope  10  with the plurality of magnetic field sensors that has been installed at a plurality of locations. Then, at least one of the position, the azimuth angle and the tilt angle of the capsule endoscope  10  is continuously calculated based on these detection results. In this case, the guidance device  20  may control the magnetic field generated by itself based on at least one of the calculated position, azimuth angle and tilt angle of the capsule endoscope  10 . Also, the guidance device  20  may check whether or not the position of the capsule endoscope  10  is located within the measurement region in the subject  101  (within the region of the magnetic field generated by the magnetic field generating unit  25 ), and control the action of the shielding unit  26  based on this checking result. For example, when the capsule endoscope  10  is located within the measurement region in the subject  101 , the control unit  28  controls the shielding unit  26  to remove the magnetic body member  26   a  from below the effective magnetic field area  100  so as to be in the magnetic field generating state. On the other hand, when the capsule endoscope  10  is located outside the measurement region within the subject  101 , the control unit  28  controls the shielding unit  26  to insert the magnetic body member  26   a  below the effective magnetic field area  100  so as to be in the magnetic field shielding state. 
     Modified Example 1-4 
     Next, modified example 1-4 of the first embodiment will be described. 
     As the position detection method of the capsule endoscope  10  within the subject  101 , another method of detecting an AC magnetic field will be described. In this case, an LC circuit that resonates with an AC magnetic field is disposed inside the capsule endoscope  10 , and an AC magnetic field generation device and a plurality of magnetic field sensors that detects an AC magnetic field are disposed on the guidance device  20  side. 
     The guidance device  20  previously detects a first AC magnetic field that is generated by the AC magnetic field generation device, in a state where the capsule endoscope  10  is not located within the measurement region within the subject  101  (within the region of the magnetic field generated by the magnetic field generating unit  25 ). Then, when the capsule endoscope  10  is located within the measurement region within the subject  101 , a second AC magnetic field containing the resonance magnetic field generated by the LC circuit in the capsule endoscope  10  is detected. Thereafter, the resonance magnetic field generated by the LC circuit in the capsule endoscope  10  is calculated from the difference value between the detected value of the first AC magnetic field and the detected value of the second AC magnetic field. The guidance device  20  continuously calculates the position coordinate of the capsule endoscope  10  in a three-dimensional space, based on the resonance magnetic field calculated as described above. 
     Modified Example 1-5 
     Next, modified example 1-5 of the first embodiment will be described. 
       FIG. 37  is a schematic diagram illustrating a modified example of the magnetic field generating unit  25  illustrated in  FIG. 1 . A magnetism generation unit that generates magnetism in the magnetic field generating unit  25  is not limited to a configuration in which only the extracorporeal permanent magnet  25   a  is employed. 
     For example, as illustrated in  FIG. 37 , a magnetism generation unit may be achieved by an electromagnet having an extracorporeal permanent magnet  25   a - 1  and a coil  25   a - 2 . The extracorporeal permanent magnet  25   a - 1  is arranged such that one plane (a capsule facing plane PL3) among four planes parallel to the magnetization direction thereof becomes parallel to the horizontal plane. 
     On the other hand, the coil  25   a - 2  is fixed to the guidance device  20  and arranged so that an orientation Zμ of a magnetic field generated by the coil  25   a - 2  becomes in the vertical direction. The coil  25   a - 2  generates a magnetic field in the vertical direction within the guidance region of the capsule endoscope  10 . The generated magnetic field has uniformity higher than by the extracorporeal permanent magnet  25   a - 1 . Also, the magnetic field strength thereof can be controlled by the control unit  28 . 
     In this case, the tilt angle of the capsule endoscope  10  is controlled by a synthesis magnetic field of the magnetic field in the horizontal direction generated by the extracorporeal permanent magnet  25   a - 1  and the magnetic field in the vertical direction generated by the coil  25   a - 2 . Also, the azimuth angle of the capsule endoscope  10  is controlled by the revolution angle changing action of the extracorporeal permanent magnet  25   a - 1  by the revolution angle changing unit  25   e . Furthermore, the position of the capsule endoscope  10  is controlled by the translating action of the extracorporeal permanent magnet  25   a - 1  by the plane position changing unit  25   b  and the vertical position changing unit  25   c.    
     According to modified example 1-5, since an electromagnet can generate a strong magnetic field having uniformity higher compared to a permanent magnet to the guidance region, the tilt angle and the azimuth angle of the capsule endoscope  10  can be more stably controlled. Also, in this case, since the extracorporeal permanent magnet  25   a - 1  is mainly used only for controlling the position and the azimuth angle of the capsule endoscope  10 , the limitation to the shape of the extracorporeal permanent magnet  25   a - 1  can be alleviated. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. 
       FIG. 38  and  FIG. 39  are partial sectional side views schematically illustrating a configuration example of a capsule medical apparatus guidance system according to a second embodiment. As illustrated in  FIG. 38  and  FIG. 39 , a capsule medical apparatus guidance system (hereinafter, merely referred to as a guidance system)  2  according to the second embodiment includes the capsule endoscope  10  and a guidance device  20 A.  FIG. 38  illustrates a case in which the guidance device  20 A is in the magnetic field generating state, and  FIG. 39  illustrates a case where the guidance device  20 A is in the magnetic field shielding state. 
     The guidance device  20 A has, instead of the drive unit  26   c  illustrated in  FIG. 2 , an elastic member  26   e  that slides the magnetic body member  26   a  with an elastic force. As the elastic member  26   e , there can be used, for example, rubber as well as a spring member such as a wind-up spring, a disk spring and a plate spring. The configuration of each of the other components of the guidance device  20 A is similar to that in the first embodiment. 
     As illustrated in  FIG. 38 , when the guidance device  20 A is in the magnetic field generating state, the elastic member  26   e  shrinks while pressing the magnetic body member  26   a  with the elastic force thereof. At this time, the position of the magnetic body member  26   a  is fixed by the fixing unit  26   d.    
     As illustrated in  FIG. 39 , when the fixing unit  26   d  is moved upward to release the fixing state of the magnetic body member  26   a , the magnetic body member  26   a  slides with an elastic force caused by the elastic member  26   e  and moves to the concave  20   c  below the effective magnetic field area  100  (above the magnetic field generating unit  25 ). Accordingly, the guidance device  20 A is shifted to the magnetic field shielding state. Here, operation of the fixing unit  26   d  for releasing the fixing state of the magnetic body member  26   a  may be performed manually by a user, or the fixing unit  26   d  may be operated by a drive unit that acts under control of the control unit  28 . 
     According to the second embodiment described above, the magnetic body member  26   a  is moved by the elastic force of the elastic member  26   e . Therefore, for example, even when a situation like sudden loss of electric power occurs, the guidance device  20 A can be quickly shifted to the magnetic field shielding state. 
     Here, when shifting the guidance device  20 A from the magnetic field shielding state to the magnetic field generating state, a user may manually move the positions of the magnetic body member  26   a  and the fixing unit  26   d , or the magnetic body member  26   a  may be moved in the horizontal direction (in the right direction of the diagram) by a separately disposed drive unit that acts under control of the control unit  28 . 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described. 
       FIG. 40  and  FIG. 41  are partial sectional side views schematically illustrating a configuration example of a capsule medical apparatus guidance system according to the third embodiment. As illustrated in  FIG. 40  and  FIG. 41 , a capsule medical apparatus guidance system (hereinafter, merely referred to as a guidance system)  3  according to the third embodiment includes the capsule endoscope  10  and a guidance device  30 .  FIG. 40  illustrates a case in which the guidance device  30  is in the magnetic field generating state, and  FIG. 41  illustrates a case where the guidance device  30  is in the magnetic field shielding state. 
     The configuration of the guidance system  3  is generally similar to the guidance system  1  illustrated in  FIG. 1 , and only the configurations of a bed  30   a  and a shielding unit  31  described later are different from the guidance system  1 . 
     The guidance device  30  includes a bed  30   a  as a placing table on which the subject  101  is placed. The bed  30   a  is slidably disposed with respect to a leg  30   b  that supports the bed  30   a . The main surface (the subject placing surface) of the bed  30   a  contains a region R A  on which the examination target region (for example, the stomach) of the subject  101  is placed, and a region R B  on which the non-examination target region (for example, the leg) is placed. The position of this bed  30   a  relative to the leg  30   b  is switched by a drive unit  31   b  described later between the position of a state where the region R A  is inserted between the magnetic field generating unit  25  and the effective magnetic field area  100  (the magnetic field generating state), and the position of a state where the region R A  is removed from between the magnetic field generating unit  25  and the effective magnetic field area  100  (the magnetic field shielding state). 
     The magnetic field generating unit  25  for forming a magnetic field to the effective magnetic field area  100  is housed inside the leg  30   b . Here, in order to inhibit leakage of the magnetic field generated by the magnetic field generating unit  25  into a space other than the effective magnetic field area  100  (for example, in the side surface direction of the leg  30   b ), the leg  30   b  is preferably made of a ferromagnetic substance such as an iron plate. 
     The guidance device  30  includes a shielding unit  31  that shields the magnetic field generated by the magnetic field generating unit  25  to the effective magnetic field area  100 . The shielding unit  31  has a magnetic body member  31   a  and a drive unit  31   b . The magnetic body member  31   a  is attached to the lower surface of the bed  30   a , and the drive unit  31   b  acts under control of the control unit  28  to allow the bed  30   a  to move together with the magnetic body member  31   a.    
     The magnetic body member  31   a  is made of, for example, a ferromagnetic substance such as an iron plate. The material and the size of the magnetic body member  31   a  are similar to the magnetic body member  26   a  described in the first embodiment. Such a magnetic body member  31   a  is fixed in a concave disposed on the lower surface of the bed  30   a  through adhesion, mechanical fastening, and the like. The position of the magnetic body member  31   a  relative to the bed  30   a  is determined so that when shifted to the magnetic field shielding state, the magnetic body member  31   a  covers at least the region above the magnetic field generating unit  25 . In the third embodiment, the magnetic body member  31   a  is arranged in a portion of the region R B . 
     The drive unit  31   b  moves the bed  30   a  attached with the magnetic body member  31   a  one-dimensionally (for example, in the height direction of the subject  101 ) within the horizontal plane, in order to switch the position of the bed  30   a  between the position in the magnetic field generating state and the position in the magnetic field shielding state. 
     The guidance device  30 , as illustrated in  FIG. 40 , moves the bed  30   a  so that the region R A  is located above the magnetic field generating unit  25  during examination. Accordingly, the magnetic body member  31   a  is removed from between the magnetic field generating unit  25  and the effective magnetic field area  100 , and the magnetic field generated in the effective magnetic field area  100  by the magnetic field generating unit  25  leads to a state (a magnetism generating state) that allows the magnetic guidance of the capsule endoscope  10 . On the other hand, the guidance device  30 , as illustrated in  FIG. 41 , moves the bed  30   a  such that the region R A  departs from above the magnetic field generating unit  25  before and after examination or during an emergency stop. This leads to the magnetic field shielding state where the magnetic body member  31   a  is inserted between the magnetic field generating unit  25  and the effective magnetic field area  100 . 
     Thus, in the third embodiment, since the shielding of a magnetic field by the magnetic body member  31   a  and the movement of the bed  30   a  are performed in conjunction with each other, the effect of a magnetic field on the capsule endoscope  10  in the magnetic field shielding state can be further reduced. 
     Here, in the third embodiment, the bed  30   a  may also be moved due to an elastic member such as a spring in a similar manner to the second embodiment, instead of the drive unit  31   b.    
     Fourth Embodiment 
     Next, a fourth embodiment of the present invention will be described. 
       FIG. 42  and  FIG. 43  are partial sectional side views schematically illustrating a configuration example of the capsule medical apparatus guidance system according to the fourth embodiment. As illustrated in  FIG. 42  and  FIG. 43 , a capsule medical apparatus guidance system (hereinafter, merely referred to as a guidance system)  4  according to the fourth embodiment includes the capsule endoscope  10  and a guidance device  40 .  FIG. 42  illustrates a case in which the guidance device  40  is in the magnetic field generating state, and  FIG. 43  illustrates a case where the guidance device  40  is in the magnetic field shielding state. 
     The configuration of the guidance system  4  is generally similar to the guidance system  1  illustrated in  FIG. 1 , and only the configurations of a bed  40   a  and a shielding unit  41  described later are different from the guidance system  1 . 
     The guidance device  40  includes a bed  40   a  as a placing table on which the subject  101  is placed. The bed  40   a  is slidably disposed with respect to a leg  40   b  that supports the bed  40   a . The main surface of the bed  40   a  contains a region R A  on which the examination target region of the subject  101  is placed, and a region R B  on which the non-examination target region is placed. The position of this bed  40   a  relative to the leg  40   b  is switched by a drive unit  41   e  described later between the position of a state where the region R A  is inserted between the magnetic field generating unit  25  and the effective magnetic field area  100  (the magnetic field generating state), and the position of a state where the region R A  is removed from between the magnetic field generating unit  25  and the effective magnetic field area  100  (the magnetic field shielding state). 
     The magnetic field generating unit  25  for forming a magnetic field to the effective magnetic field area  100  is housed inside the leg  40   b . Here, in order to inhibit the leakage of the magnetic field generated by the magnetic field generating unit  25  into a space other than the effective magnetic field area  100  (for example, in the side surface direction of the leg  40   b ), the leg  40   b  may be made of a ferromagnetic substance such as an iron plate. 
     A guidance device  40  includes a shielding unit  41  that shields the magnetic field generated by the magnetic field generating unit  25  to the effective magnetic field area  100 . The shielding unit  41  has a magnetic fluid  41   a , a magnetic fluid housing unit  41   b  disposed inside the bed  40   a , a magnetic fluid storage unit  41   c  disposed below the bed  40   a , a piston  41   d  that moves the magnetic fluid  41   a  into the magnetic fluid housing unit  41   b  through a linking hole  41   f , and a drive unit  41   e  that acts under control of the control unit  28  to move the bed  40   a.    
     The magnetic fluid  41   a  is a fluid having magnetic properties. For example, a dispersion of magnetic body particles such as magnetite in liquid such as water or oil is used. Such a magnetic fluid  41   a  is stored in the magnetic fluid storage unit  41   c  when the guidance device  40  is in the magnetic field generating state, and is housed in the magnetic fluid housing unit  41   b  when the guidance device  40  is in the magnetic field shielding state. 
     The region where the magnetic fluid housing unit  41   b  is disposed is determined so that when shifted to the magnetic field shielding state, the magnetic fluid housing unit  41   b  covers at least the region above the magnetic field generating unit  25 . In the fourth embodiment, the magnetic fluid housing unit  41   b  is disposed in the region R B  and a portion of the region R A . 
     The magnetic fluid storage unit  41   c  has a volume substantially equal to the magnetic fluid housing unit  41   b , and disposed, for example, in the end region of the bed  40   a.    
     The magnetic fluid housing unit  41   b  and the magnetic fluid storage unit  41   c  communicate with each other through the linking hole  41   f.    
     The piston  41   d  is a magnetic fluid moving means that is disposed within the magnetic fluid storage unit  41   c  and that works in conjunction with movement of the bed  40   a . The piston  41   d  is moved in the right direction of the diagram to the magnetic fluid storage unit  41   c , thereby to extrude the magnetic fluid  41   a  in the magnetic fluid storage unit  41   c  into the magnetic fluid housing unit  41   b  through the linking hole  41   f . Also, the piston  41   d  is moved in the left direction of the diagram to the magnetic fluid storage unit  41   c , thereby to suck the magnetic fluid  41   a  in the magnetic fluid housing unit  41   b  into the magnetic fluid storage unit  41   c  through the linking hole  41   f.    
     The drive unit  41   e  moves the bed  40   a  one-dimensionally (for example, in the height direction of the subject  101 ) within the horizontal plane, so that the position of the bed  40   a  is switched between the position in the magnetic field generating state and the position in the magnetic field shielding state. The relative position of the piston  41   d  to the magnetic fluid storage unit  41   c  is changed in conjunction with the shifting of the position of the bed  40   a.    
     The guidance device  40 , as illustrated in  FIG. 42 , moves the bed  40   a  so that the region R A  is located above the magnetic field generating unit  25  during examination. Accordingly, the magnetic fluid  41   a  is sucked into the magnetic fluid storage unit  41   c  so that the magnetic fluid housing unit  41   b  becomes empty, and the magnetic field generated in the effective magnetic field area  100  by the magnetic field generating unit  25  leads to a state (the magnetic field generating state) that allows the magnetic guidance of the capsule endoscope  10 . On the other hand, the guidance device  40 , as illustrated in  FIG. 43 , moves the bed  40   a  so that the region R A  departs from above the magnetic field generating unit  25  before and after examination or during an emergency stop. Accordingly, the magnetic fluid  41   a  in the magnetic fluid storage unit  41   c  is extruded into the magnetic fluid housing unit  41   b , and the magnetic fluid housing unit  41   b  filled with the magnetic fluid  41   a  is inserted between the magnetic field generating unit  25  and the effective magnetic field area  100 . That is, the magnetic field shielding state is led. 
     As described above, in the fourth embodiment, by positioning the examination target region of the subject  101  off the effective magnetic field area  100  while inserting the magnetic fluid  41   a  between the magnetic field generating unit  25  and the effective magnetic field area  100 , the magnetic field shielding state is achieved. Therefore, the effect of a magnetic field on the capsule endoscope  10  in the magnetic field shielding state can be further reduced. 
     In the fourth embodiment, the piston  41   d  moves in conjunction with the movement of the bed  40   a . However, the bed  40   a  may be fixed to the leg  40   b  to allow only the piston  41   d  to be moved, so that the magnetic fluid  41   a  circulates between the magnetic fluid housing unit  41   b  and the magnetic fluid storage unit  41   c . In this case, the magnetic fluid housing unit  41   b  may be disposed in the region of the bed  40   a  between the magnetic field generating unit  25  and the effective magnetic field area  100  (that is, a region containing the region R A ). 
     Fifth Embodiment 
     Next, a fifth embodiment of the present invention will be described. 
       FIG. 44  is a perspective view schematically illustrating a configuration example of a capsule medical apparatus guidance system according to the fifth embodiment. As illustrated in  FIG. 44 , a capsule medical apparatus guidance system (hereinafter, also merely referred to as a guidance system)  5  according to the fifth embodiment includes: the capsule endoscope  10  that contains the permanent magnet  19  therein and that is introduced into the subject  101 ; permanent magnets  51  and  52  that are faced to each other on both sides of the subject  101 ; magnet drive units  53  and  54  that drive the permanent magnets  51  and  52  respectively; shielding plates  55  and  56  disposed in an insertable and removable manner between the permanent magnets  51  and  52  and the subject  101 ; shielding plate drive units  57  and  58  that drive the shielding plates  55  and  56  respectively; and a control unit  59  that controls actions of the magnet drive units  53  and  54  and the shielding plate drive units  57  and  58 . The capsule endoscope  10  is confined by a magnetic field generated within the subject  101  by the permanent magnets  51  and  52 . The position, the tilt angle and the azimuth angle of the capsule endoscope  10  are changed in accordance with the position, elevation angle θ and revolution angle ψ of the permanent magnets  51  and  52  driven by the magnet drive units  53  and  54 . 
     The permanent magnets  51  and  52  are permanent magnets of the same type as and having the same rectangular parallelepiped shape as each other. The permanent magnets  51  and  52  each have a magnetization direction parallel to four planes of the rectangular parallelepiped. One plane (hereinafter, referred to as capsule facing planes PL4 and PL5) among these is directed toward the subject  101 . The magnetization directions of the capsule facing planes PL4 and PL5 are placed in parallel so as to be mirror-symmetrical to each other. Here, the magnetization directions of the permanent magnets  51  and  52  are directed toward the vertical direction (z-axis direction) when the guidance of the capsule endoscope  10  is not performed. Hereinafter, among the directions orthogonal to the vertical direction when the guidance of the capsule endoscope  10  is not performed, the direction orthogonal to the capsule facing planes PL4 and PL5 is defined as an x-axis direction, and the direction parallel to the capsule facing planes PL4 and PL5 is defined as a y-axis direction. 
     Each of the permanent magnets  51  and  52  has a shape in which, among the lengths of the sides in three directions of the rectangular parallelepiped shape, the length of a side in a direction orthogonal to the capsule facing planes PL4 and PL5 (in the x-axis direction in  FIG. 44 ) is shorter than the length of a side in one direction contained in the capsule facing planes PL4 and PL5 (a magnetization direction or a direction orthogonal to the magnetization direction, in the z-axis direction or the y-axis direction in  FIG. 44 ). Preferably, the permanent magnets  51  and  52  each have a flat plate shape in which, among the lengths of the sides in three directions of the rectangular parallelepiped shape, the length in a direction orthogonal to the capsule facing planes PL4 and PL5 is the shortest. 
     The permanent magnets  51  and  52  are configured in such a manner as being capable of translating together in the horizontal direction and the vertical direction. Accordingly, the position of the capsule endoscope  10  within the subject  101  can be controlled. Further, the translation of the permanent magnets  51  and  52  within the vertical plane changes the position of the capsule endoscope  10  within the vertical plane. For example, the translation of the permanent magnets  51  and  52  within the horizontal plane changes the position of the capsule endoscope  10  within the horizontal plane. 
     The permanent magnets  51  and  52  are configured in such a manner as being capable of rotating around an axis R 0  that is orthogonal to the capsule facing planes PL4 and PL5 and extending through respective centers, and around axes R 1  and R 2  that are orthogonal to the magnetization direction within the capsule facing planes PL4 and PL5. Accordingly, the azimuth angle and the tilt angle of the capsule endoscope  10  within the subject  101  can be controlled. For example, the rotation (revolution) of the permanent magnets  51  and  52  around the axis R 0  while maintaining the positional relationship between the permanent magnets  51  and  52  is followed by the capsule endoscope  10  to change the azimuth angle. Also, the tilting of the permanent magnets  51  and  52  relative to the axes R 1  and R 2  while maintaining the positional relationship between the permanent magnets  51  and  52  is followed by the capsule endoscope  10  to be tilted. 
     Furthermore, the permanent magnets  51  and  52  are configured in such a manner as being capable of changing the distance between the permanent magnets  51  and  52 . The change of the distance between the permanent magnets  51  and  52  can cause the magnetic field strength in the effective magnetic field area  100  to be changed. In a guidance system  5 , the position of the permanent magnets  51  and  52  when the distance between the permanent magnets  51  and  52  is the largest within the installable range (that is, when the magnetic field strength in the effective magnetic field area  100  is the lowest) is set as an initial position. 
     The shielding plates  55  and  56  are each a member made of a ferromagnetic substance such as an iron plate. The shielding plates  55  and  56  may have a material and a size (width×length) that allow the magnetic field generated by the permanent magnets  51  and  52  to be shielded in the effective magnetic field area  100 . In the present fifth embodiment, the areas of the main surfaces of the permanent magnets  51  and  52  as well as the shielding plates  55  and  56  are approximately the same. 
     The shielding plate drive units  57  and  58  drive the shielding plates  55  and  56  in the vertical direction, thereby to insert and remove the shielding plates  55  and  56  into and from between the effective magnetic field area  100  and the permanent magnets  51  and  52 . When the shielding plates  55  and  56  are inserted between the effective magnetic field area  100  and the permanent magnets  51  and  52 , the guidance system  5  becomes in the magnetic field shielding state, and when the shielding plates  55  and  56  are removed from between the effective magnetic field area  100  and the permanent magnets  51  and  52 , the guidance system  5  becomes in the magnetic field generating state. 
     According to such a fifth embodiment, the subject  101  can be examined in a standing posture, and furthermore, the magnetic field generating state and the magnetic field shielding state in the guidance system  5  can be switched. 
     Here, like the fifth embodiment, when a permanent magnet is disposed laterally to the subject  101 , a capsule endoscope guidance system that examines a subject in a sitting posture can also be configured. In this case, a permanent magnet and a shielding plate may be disposed on a backrest or an armrest of a chair on which a subject sits and which is provided as a placing table. 
     The embodiments described above are only examples for implementing the present invention, and the present invention is not limited to these. Also, the present invention can generate various inventions by appropriately combining a plurality of components disclosed in the embodiments and modified examples. The present invention can be variously modified depending on specifications and the like. Furthermore, it is obvious from the above description that other various embodiments are possible within the scope of the present invention. 
     (Note 1) 
     A guidance device for applying a magnetic field to a capsule medical apparatus within which a first permanent magnet is arranged when the capsule medical apparatus is introduced into a subject, to guide the capsule medical apparatus within the subject, the guidance device including: 
     a second permanent magnet configured to be disposed outside the subject, the second permanent magnet having a first plane containing a magnetization direction and a first direction orthogonal to the magnetization direction, and being configured to confine the capsule medical apparatus within a region facing the first plane; and 
     a shielding unit configured to shield a magnetic field generated by the second permanent magnet in an effective magnetic field area where the magnetic field capable of guiding the capsule medical apparatus is generated by the second permanent magnet, and configured to switch between a first state in which the magnetic field is not shielded in the effective magnetic field area and a second state in which the magnetic field is shielded in the effective magnetic field area. 
     (Note 2) 
     The guidance device according to Note 1, wherein the shielding unit includes: 
     a magnetic body; and 
     a drive unit configured to insert and remove the magnetic body into and from between the second permanent magnet and the effective magnetic field area. 
     (Note 3) 
     The guidance device according to Note 2, wherein the magnetic body has a plate shape. 
     (Note 4) 
     The guidance device according to Note 2, wherein the drive unit is an elastic member for pressing the magnetic body with an elastic force. 
     (Note 5) 
     The guidance device according to any one of Notes 1 to 4, further including: 
     a detecting unit configured to detect a shielding state of the magnetic field by the shielding unit; and 
     a notifying unit configured to notify a detection result by the detecting unit. 
     (Note 6) 
     The guidance device according to Note 5, wherein the notifying unit is configured to notify the detection result using visual information or auditory information. 
     (Note 7) 
     A capsule medical apparatus guidance system including: 
     the guidance device according to any one of Notes 1 to 6; and 
     the capsule medical apparatus in which the first permanent magnet is arranged. 
     (Note 8) 
     A capsule medical apparatus guidance system including: 
     a guidance device for applying a magnetic field to a capsule medical apparatus within which a first permanent magnet is arranged when the capsule medical apparatus is introduced into a subject, to guide the capsule medical apparatus within the subject; and 
     the capsule medical apparatus in which the first permanent magnet is arranged, 
     wherein the guidance device includes a second permanent magnet configured to be disposed outside the subject, the second permanent magnet having a first plane containing a magnetization direction and a first direction orthogonal to the magnetization direction, and being configured to confine the capsule medical apparatus within a region facing the first plane, 
     wherein the second permanent magnet has a length in the first direction longer than a length in the magnetization direction. 
     (Note 9) 
     The capsule medical apparatus guidance system according to Note 7 or 8, 
     wherein the capsule medical apparatus is guided by the guidance device in a liquid introduced into the subject, and 
     a gravity center of the capsule medical apparatus is arranged away from a geometric center of the capsule medical apparatus in a direction different from a magnetization direction of the first permanent magnet. 
     According to some embodiments, the length the second permanent magnet in the first direction is longer than the length of the second permanent magnet in the magnetization direction. Therefore, the magnetic field suitable for guiding the capsule medical apparatus can be generated by the second permanent magnet. As a result, it is possible to achieve a guidance device that can efficiently guide a capsule medical apparatus. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.