US20080262303A1 - System for detecting position of capsule endoscope in subject - Google Patents

Abstract

A system is for detecting a position of a device. The device is swallowed, passes through a subject, and includes a magnetic field generator generating a constant magnetic field. The system also includes a position transducer. The position transducer includes a magnetic detector detecting an intensity of a magnetic field component parallel to a constant magnetic field output from the magnetic field generator, and a position processor calculating a position of the device in the subject based on the intensity detected by the magnetic detector.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of priority of Japanese Patent Application No. 2003-430-405 filed on Dec. 25, 2003, and the disclosure of which is incorporated herein by its entirely.
BACKGROUND OF THE INVENTION
• 1) Field of the Invention
• The present invention relates to a system for detecting a position of a device such as a capsule endoscope, which is swallowed and passes naturally through digestive tract of the subject, by a position transducer that is disposed on the outside of the subject and obtains information of the position of the device in the subject.
• 2) Description of the Related Art
• In recent years, in the field of endoscopes, a swallowable capsule endoscope has been proposed. The capsule endoscope has an image capturing function and a radio communication function. The capsule endoscope has the function of traveling in the body cavity, for example, in the organs such as the stomach and the small intestine with peristalsis of the organs and sequentially capturing images for a period of time since the capsule endoscope is swallowed from the mouth of a subject for inspection (examination) until it is naturally excreted.
• Image data captured in the body by the capsule endoscope as the capsule endoscope travels in the body cavity is sequentially transmitted by radio communication to the outside and stored into a memory provided on the outside. The subject can freely move throughout the period after he/she swallows the capsule endoscope until it is excreted by carrying a receiver having a radio communication function and a storing function. After the capsule endoscope is excreted, a doctor or nurse can display the images of the organs on a display based on the image data stored in the memory and make a check.
• A capsule endoscope has been proposed in which the receiver has the function of detecting the position of the capsule endoscope in the subject to capture, for example, an endoscope image of a specific organ in the subject. As an example of a capsule endoscope system having the position detecting function, a capsule endoscope system using the radio communication function provided in the capsule endoscope is known. Specifically, the system has a configuration that a receiver provided on the outside of a subject has a plurality of antenna elements, and has the function of receiving a radio signal transmitted from the capsule endoscope by the plurality of antenna elements and, based on intensities received by the antenna elements, detecting the position of the capsule endoscope in the subject (see Japanese Patent Application Laid-open No. 2003-19111, for example).
SUMMARY OF THE INVENTION
• It is an object of the present invention to at least solve the problems in the conventional technology.
• A system according to one aspect of the present invention includes a device that is swallowed, passes through a subject, and includes a magnetic field generator generating a constant magnetic field; and a position transducer that includes a magnetic detector detecting an intensity of a magnetic field component parallel to a constant magnetic field output from the magnetic field generator, and a position processor calculating a position of the device in the subject based on the intensity detected by the magnetic detector.
• The other objects, features, and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic view of a system for detecting a position of a capsule endoscope in a subject according to a first embodiment;
• FIG. 2 is a schematic view of a test capsule as a component of the system according to the first embodiment;
• FIG. 3 is a schematic view of a magnetic detector as a component of the system according to the first embodiment;
• FIG. 4 is a schematic view of a position processor as a component of the system according to the first embodiment;
• FIG. 5 is a flowchart of operations of the position processor;
• FIG. 6 is a schematic view of calculating the position of a test capsule by the position processor;
• FIG. 7 is a schematic view of a system for detecting a position of a capsule endoscope in a subject according to a second embodiment;
• FIG. 8 is a schematic view of the capsule endoscope as a component of the system according to the second embodiment; and
• FIG. 9 is a schematic view of a position processor as a component of the system for detecting a position in a subject according to the second embodiment.
DETAILED DESCRIPTION
• Exemplary embodiments of a system for detecting a position of a capsule endoscope in a subject relating to the present invention will be explained in detail below with reference to the accompanying drawings. It should be noted that the drawings are schematic ones and the relation between thickness and width of each part, the thickness ratio of the parts, and the like are different from real ones. Obviously, the drawings include parts having different relations of dimensions and ratios.
• A system for detecting a position of a capsule endoscope in a subject according to a first embodiment will now be explained. As shown inFIG. 1, the system for detecting a position of a capsule endoscope includes atest capsule2 that is swallowed and passes though asubject1 and functions as an example of a device to be traveled in a subject; aposition transducer3 that detects the position in thesubject1 of thetest capsule2; adisplay4 displaying position information of thetest capsule2 detected by theposition transducer3; and aportable recording medium5 for transmitting/receiving information between theposition transducer3 and thedisplay4.
• Thedisplay4 is used for displaying position information of thetest capsule2 obtained by theposition transducer3 and has a configuration like a workstation or the like that displays an image based on data obtained from theportable recording medium5. Concretely, thedisplay4 may be constructed to directly display an image by a cathode-ray tube (CRT) display, a liquid crystal display, or the like or to output an image to another medium like a printer or the like.
• Theportable recording medium5 can be inserted/removed to/from aposition processor8 that is explained later and thedisplay4, and has a structure capable of outputting and recording information when inserted to theposition processor8 and thedisplay4. Concretely, theportable recording medium5 is inserted in theposition processor8 to record information on the position of thetest capsule2 while thetest capsule2 travels in the body cavity of thesubject1. After thetest capsule2 is excreted from thesubject1, theportable recording medium5 is removed from theposition processor8 and inserted into thedisplay4, and the recorded data is read by thedisplay4. By transmitting data between theposition processor8 and thedisplay4 by theportable recording medium5 such as a compact flash (trademark) memory, different from the case where theposition processor8 and thedisplay4 are connected to each other by wire, even when thetest capsule2 is traveling in thesubject11 thesubject1 can move freely.
• Thetest capsule2 is used at the time of conducting a preliminary inspection to check whether or not a narrow part in which passage of a capsule endoscope is difficult exists in thesubject1 before introduction of the capsule endoscope or the like into thesubject1. The system according to the first embodiment is used to check how thetest capsule2 travels in thesubject1. To achieve the purpose, a high-precision position detecting mechanism is provided.
• FIG. 2 is a schematic diagram of thetest capsule2. As shown inFIG. 2, thetest capsule2 includes acasing10 having a capsule shape that is similar to that of a casing of a capsule endoscope; acase member12 held in thecasing10 and having a spherical shell shape; and aspherical body15 disposed in a state where it floats in theliquid14 held in thecase member12. The clearance between the inner surface of thecasing10 and the outer surface of thecase member12 is filled with afilling member11.
• Thecasing10 is made of, for example, a bio-compatible material and has a characteristic such that when thecasing10 remains in thesubject1 for a few days, the material dissolves. By forming thecasing10 of a bio-compatible material, there is an advantage such that even if thetest capsule2 introduced in thesubject1 is not excreted to the outside of thesubject1, it is unnecessary to perform an abdominal operation or the like on thesubject1.
• The fillingmember11 is provided to fill the clearance between the inner face of thecasing10 and apermanent magnet13 to fix the position of thepermanent magnet13. The material of the fillingmember11 does not exert an adverse influence on thesubject1. For example, the fillingmember11 is made of barium sulfate. Since barium sulfate can be used as a contrast medium in an X-ray inspection, position detection by an X-ray inspection can be performed in addition to the position detection of the first embodiment. By comparing the results of both of the inspections, more accurate position detection can be performed. Obviously, it is not essential to use barium sulfate as the fillingmember11 in the first embodiment and an arbitrary material can be used as long as the material functions as the filling member.
• Thespherical body15 has therein thepermanent magnet13 and aweighting member16. Theweighting member16 is a member that is heavier than the other elements constructing thespherical body15, and thespherical body15 floats in theliquid14 in a state where theweighting member16 is positioned at the bottom in the vertical direction. As shown inFIG. 2, theweighting member16 is disposed so as to position on extension line in the direction of an output magnetic field from thepermanent magnet13.
• Thepermanent magnet13 functions as a magnetic field generator in the claims, has a size that can be housed in thecasing10, and is to output a constant magnetic field whose intensity fluctuation with time is ignorable. As described above, theweighting member16 is disposed on extension of the magnetic field output direction of thepermanent magnet13, so that thepermanent magnet13 maintains a state where the output magnetic field direction is parallel to the vertical direction irrespective of fluctuations in the orientation of thetest capsule2 by the action of theweighting member16.
• In place of thepermanent magnet13, for example, a coil that receives constant current and generates a constant magnetic field may be used as the magnetic field generator. In the case of using thepermanent magnet13, there is an advantage such that drive power is unnecessary. Thus, it is preferable to construct the magnetic field generator by using thepermanent magnet13.
• The constant magnetic field generated from thepermanent magnet13 is expressed by a line of magnetic force of a closed curve that is output from the N pole side, travels on the outside of thepermanent magnet13, and enters again on the S pole side. As shown inFIG. 2, the travel direction of the line of magnetic force has location dependency but it can be regarded that the intensity of the constant magnetic field expressed by the line of magnetic force is determined only in accordance with the distance from thetest capsule2. Specifically, the size of thepermanent magnet13 provided in thetest capsule2 is small enough to be ignored as compared with the distance between thetest capsule2 andmagnetic detectors6ato6h. Consequently, magnetic field intensity P at a point apart from thetest capsule2 only by distance “r” is expressed as follows by using a proportional factor α.
• 
  P=α/r³  (1)
• The system according to the first embodiment detects the position of thetest capsule2 based on the relation shown in Equation (1) as is explained later.
• Theposition transducer3 is explained. Theposition transducer3 detects the position of thetest capsule2 in the subject1 based on the constant magnetic field output from thetest capsule2. Concretely, theposition transducer3 has, as shown inFIG. 1, themagnetic detectors6ato6hfor detecting the intensity of the constant magnetic field output from thetest capsule2, a fixingmember7afor fixing themagnetic detectors6ato6dto thesubject1, a fixingmember7bfor fixing themagnetic detectors6eto6hto thesubject1, and theposition processor8 for calculating the position of thetest capsule2 based on the magnetic field intensities detected by themagnetic detectors6ato6h.
• Each of themagnetic detectors6ato6his to detect the magnetic field intensity in the position where it is disposed.FIG. 3 is a schematic diagram of each of themagnetic detectors6ato6h. As shown inFIG. 3, each of themagnetic detectors6ato6his constructed by aspherical body19 having amagnetic sensor21, a liquid20 disposed so as to cover the outer surface of thespherical body19 for holding thespherical body19 in a floating state, acase member18 for holding the liquid20, and elements provided on the outside of thecase member18.
• Thespherical body19 has amagnetic sensor21, amagnetic measurement controller22 that controls the driving state or the like of themagnetic sensor21, a transmitting/receivingunit25 that modulates/demodulates a signal as necessary at the time of performing radio communications with the outside of thespherical body19, and a transmitting/receivingantenna26 for performing radio communications with the outside. Thespherical body19 has acapacitor23 that holds power to drive themagnetic sensor21 and the like, a power receiving unit24 that converts a power supply signal transmitted from the outside to power, and apower receiving antenna27 for receiving the power supply signal transmitted from the outside and supplying it to the power receiving unit.
• Thespherical body19 also has aweighting member28 that is disposed on extension in the magnetic field detecting direction (that is explained later) of themagnetic sensor21 and is made of a member heavier than the other elements. Since thespherical body19 is held in a state where thespherical body19 floats in the liquid20, by the action of theweighting member28, thespherical body19 always maintains the state where theweighting member28 is positioned at the bottom in the vertical direction irrespective of fluctuations in the state of themagnetic detector6.
• Themagnetic sensor21 takes the form of a magnetic field intensity sensor such as a magneto-impedance (MI) sensor having the function of detecting the magnetic field that travels in a predetermined direction (hereinbelow, the magnetic field direction will be called a “magnetic field detecting direction”). The MI sensor has a configuration using, for example, an FeCoSiB amorphous wire as a magneto-sensitive medium and senses the magnetic field intensity by using an MI effect that the magnetic impedance of the magneto-sensitive medium largely changes according to an external magnetic field when high-frequency current is passed to the magneto-sensitive medium. Themagnetic sensor21 has a magnetic field detecting direction shown by the arrow inFIG. 3 and has a configuration that theweighting member28 is disposed on extension of the magnetic field detecting direction. Consequently, themagnetic sensor21 is held in a state where the magnetic field detecting direction always coincides with the vertical direction, and senses the intensity of a magnetic field component traveling in the vertical direction among magnetic fields existing in the region where themagnetic detector6 is disposed.
• Themagnetic detector6 has, around thecase member18, apower supplying antenna29 that transmits a power supply signal, a transmitting/receivingantenna30 performing reception or the like of the magnetic field intensity detected by themagnetic sensor21, apower supply unit31 electrically connected to thepower supplying antenna29, and a transmitting/receivingunit32 electrically connected to the transmitting/receivingantenna30. Thepower supply unit31 and the transmitting/receivingunit32 are electrically connected to amain controller33 and operate under control of themain controller33. Themain controller33 is electrically connected to theposition processor8, operates under control of theposition processor8, and has the function of outputting the magnetic field sensed by themagnetic sensor21 to theposition processor8.
• The fixingmembers7aand7bfix themagnetic detectors6ato6hto thesubject1. Concretely, each of the fixingmembers7aand7bis formed, for example, of an elastic member in an annular shape and is fixed in a state where it is closely attached to the trunk of thesubject1. Themagnetic detectors6ato6dand themagnetic detectors6eto6hare fixed to predetermined positions in the subject1 by the fixingmembers7aand7b, respectively. By closely attaching the fixingmembers7aand7bto the trunk of the subject1, themagnetic detectors6ato6hare disposed in a state where their relative positions to the subject1 are fixed.
• Theposition processor8 calculates the position of thetest capsule2 based on the magnetic field intensities sensed by themagnetic detectors6ato6h. A concrete configuration of theposition processor8 is as shown in the block diagram ofFIG. 4. As shown inFIG. 4, theposition processor8 includes areference device selector35 that selects a reference magnetic detector (hereinbelow, called “reference device”) from themagnetic detectors6ato6h, and amagnetic selector36 that outputs the magnetic field intensity obtained by the predetermined number of magnetic detectors based on the result of selection by thereference device selector35. Theposition processor8 includes adistance calculator37 for calculating distance between thetest capsule2 and the reference device or the like based on the magnetic field intensity output from themagnetic selector36; aposition calculator38 for calculating the position of thetest capsule2 by performing a computing process using the calculated distance and position coordinates of the reference device or the like used for calculating the distance; and astorage unit39 for storing information of the position of thetest capsule2 obtained by theposition calculator38 into theportable recording medium5.
• Thereference device selector35 has the function of selecting the largest value of the detected magnetic field intensity from themagnetic detectors6ato6h. Concretely, thereference device selector35 compares the magnetic field intensity values output from themagnetic detectors6ato6hwith each other, selects the magnetic detector (reference device) that has output the largest magnetic field intensity value, and outputs information specifying the reference device (for example, information indicating the reference device among themagnetic detectors6ato6h) to themagnetic selector36.
• Themagnetic selector36 selects a plurality of magnetic detectors based on the result of selection of thereference device selector35 and outputs the magnetic field intensities obtained by the selected magnetic detectors (selected devices) to thedistance calculator37. Concretely, themagnetic selector36 has the function of selecting three magnetic detectors disposed in directions orthogonal to each other with respect to the reference device. Specifically, in the system according to the first embodiment, as also shown inFIG. 1, themagnetic detectors6ato6hare disposed so as to form vertexes of a cube, so that three magnetic detectors positioned in direction orthogonal to each other always exist for an arbitrary magnetic detector, and themagnetic selector36 has the function of selecting the three magnetic detectors as selected devices.
• Thedistance calculator37 calculates the distances among the reference device, the selected devices, and thetest capsule2 based on the magnetic field intensities received via themagnetic selector36. Concretely, thedistance calculator37 has the function of calculating the distance between the magnetic detector that has detected the magnetic field intensity and thetest capsule2 by performing the computing process shown by Equation (1) with respect to the input magnetic field intensity.
• Theposition calculator38 calculates the position of thetest capsule2 by performing a predetermined computing process based on the distance between the magnetic field intensity detecting device selected as a reference device or the like and thetest capsule2. Theposition calculator38 also has the function of calculating the position of thetest capsule2 and, after that, outputting the result of calculation to thestorage unit39.
• The operation of theposition processor8 in the first embodiment is explained.FIG. 5 is a flowchart that depicts the operation of theposition processor8, andFIG. 6 is a schematic diagram for explaining the algorithm of the position calculation. InFIG. 6, the length of one side of a cube constructed by themagnetic detectors6ato6his set as “a”. As is explained later, the position of themagnetic detector6eselected as a reference device is set as the origin, the direction from themagnetic detector6etoward themagnetic detector6fis set as an x direction, the direction from themagnetic detector6etoward themagnetic detector6his set as a y direction, and the direction from themagnetic detector6etoward themagnetic detector6ais set as a z direction. The positions of themagnetic detectors6ato6hare determined based on the xyz coordinate system, and the position of thetest capsule2 in the xyz coordinate system is expressed as (x,y,z). The operation of theposition processor8 is explained hereinbelow by properly referring toFIGS. 5 and 6.
• First, theposition processor8 selects the magnetic detector having the magnetic field intensity that is the highest among the magnetic field intensities received by themagnetic detectors6ato6h(step S101). The example ofFIG. 6 is a case where themagnetic detector6eis selected as the magnetic detector sensing the highest magnetic field intensity. In the following description, it is also assumed that themagnetic detector6eis the reference voltage.
• Theposition processor8 selects three devices by themagnetic selector36 based on the reference device selected in step S101 (step S102), and outputs the magnetic field intensities obtained by the reference device and the selected devices to the distance calculator37 (step S103). In the example ofFIG. 6, themagnetic detectors6f,6h, and6aare disposed in the directions orthogonal to each other with respect to themagnetic detector6eas a reference device, so that themagnetic selector36 selects themagnetic detectors6f,6h, and6aas selected devices.
• After that, theposition processor8 calculates the distance from thetest capsule2 based on the magnetic field intensity obtained by the reference device selected in step S101 and the magnetic field intensities obtained by the devices selected in step S102 by the distance calculator37 (step S104). Concretely, thedistance calculator37 calculates the distance by performing computation of Equation (1) using the magnetic field intensity input via themagnetic selector36. In the example ofFIG. 6, thedistance calculator37 calculates distances r₁, r₂, r₃, and r₄between thetest capsule2 and themagnetic detectors6e,6f,6h, and6a, respectively, based on the magnetic field intensities detected by the reference device and the selected devices.
• Theposition processor8 calculates the position of thetest capsule2 by the computing process in the position calculator38 (step S105). Concretely, the position of thetest capsule2 is calculated by deriving the x coordinate, y coordinate, and z coordinate of thetest capsule2, so that the coordinates of thetest capsule2 are derived by using the coordinates of themagnetic detectors6e,6f,6h, and6aand the values of distances derived in step S104.
• For example, the position coordinates (x,y,z) of thetest capsule2 can be geometrically derived from the positional relations shown inFIG. 6 and, concretely, can be calculated by solving the following equations.
• 
  (x−0)²+(y−0)²+(z−0)²=r₁²  (2)
• 
  (x−a)²+(y−0)²+(z−0)²=r₂²  (3)
• 
  (x−0)²+(y−a)²+(z−0)²=r₃²  (4)
• 
  (x−0)²+(y−0)²+(z−a)²=r₄²  (5)
• In Equations (2) to (5), the number of unknown letters is three so that three equations are theoretically sufficient. At the time of actual position detection, however, to suppress deterioration in precision of the position detection of thetest capsule2 due to positional deviations of themagnetic detectors6ato6h, a distance derivation error, and the like, after solving Equations (2) to (5), the coordinates of the magnetic detector, and the like are corrected so that the values x, y, and z are unconditionally determined.
• Finally, theposition processor8 stores the position of thetest capsule2 calculated in step S105 by the storage unit39 (step S106). Concretely, while thetest capsule2 is swallowed in thesubject1, theportable recording medium5 is inserted in thestorage unit39, so that thestorage unit39 records the position information obtained in step S105 into theportable recording medium5.
• The processes in steps S101 to S106 are repeatedly performed at predetermined time intervals. As a result, theportable recording medium5 records information of travel in thesubject1 of thetest capsule2. After thetest capsule2 is excreted to the outside of the subject1, theportable recording medium5 is inserted to thedisplay4. The user grasps how thetest capsule2 travels in the subject1 based on the result of recording displayed on thedisplay4 and determines the location of a narrow region existing in the subject1 or the like from the grasped result.
• The advantages of the system according to the first embodiment is explained. First, the system according to the first embodiment calculates the position of thetest capsule2 based on the constant magnetic field output from thepermanent magnet13 in thetest capsule2. Different from electromagnetic waves and the like, the constant magnetic field has a characteristic that its intensity attenuates almost unconditionally irrespective of physical parameters such as dielectric constant, magnetic permeability, and the like in a propagation region, so that the relation of Equation (1) is excellently satisfied. Therefore, the system has an advantage such that position detection can be performed with higher precision even in a space like the inside of a human body where organs and the like whose physical parameters are different from each other exist as compared with position detection using electromagnetic waves or the like.
• Another advantage of using the constant magnetic field is that burden on the subject when thetest capsule2 is introduced into thesubject1 is lessened. For the above reasons, the system according to the first embodiment has an advantage such that deterioration in precision of the position detection due to variations of environments around thetest capsule2 is suppressed. Consequently, for example, at the time of introducing thetest capsule2 into thesubject1, it is unnecessary to impose limitations such as restriction on eating and drinking like in other inspecting methods. Therefore, the subject1 can live normal life also at the time of an inspection using thetest capsule2 and the burden on the subject1 in the inspection can be lessened.
• In the system for detecting a position in a subject according to the first embodiment, thepermanent magnet13 held in thetest capsule2 maintains a state where the output magnetic field direction is parallel to the vertical direction irrespective of fluctuations in the orientation of thetest capsule2. Themagnetic sensor21 held in each of themagnetic detectors6ato6hmaintains the state where the magnetic field detecting direction is parallel to the vertical direction irrespective of a change in the posture or the like of thesubject1. Thus, in the system for detecting a position in a subject according to the first embodiment, the state where the magnetic field output direction by thepermanent magnet13 and the magnetic field detecting direction of themagnetic sensor21 are always parallel with each other is maintained.
• By employing such a configuration, the system for detecting a position in a subject according to the first embodiment has an advantage such that the magnetic field intensity can be detected with high sensitivity. Specifically, most of the constant magnetic fields output from thepermanent magnet13 travel in the direction parallel to the magnetic field output direction also on the outside of the subject1, and the magnetic field detecting direction of themagnetic sensor21 becomes parallel to the magnetic field direction by thepermanent magnet13. Consequently, the constant magnetic field output from thepermanent magnet13 can be efficiently detected and high-sensitivity detection of the magnetic field intensity can be realized. To enjoy the advantage, it is sufficient that the magnetic field detecting direction of themagnetic sensor21 and the magnetic field output direction by thepermanent magnet13 are parallel to each other. The directions do not always have to be parallel to the vertical direction.
• Further, in the system for detecting a position in a subject according to the first embodiment, particularly, the configuration of the magnetic sensor with respect to themagnetic detectors6ato6hcan be simplified. Specifically, when the magnetic field output direction from thepermanent magnet13 and the magnetic field detecting direction of the magnetic sensor do not have a correlation, the magnetic detector has to have magnetic field intensity detecting mechanisms in three axes directions. In such a case, generally, magnetic sensors having magnetic field detecting directions with respect to the x, y, and z directions have to be provided. In contrast, the system according to the first embodiment is disposed in a state where the magnetic field detecting direction of themagnetic sensor21 coincides with the magnetic field output direction of thepermanent magnet13. Consequently, a magnetic field detecting mechanism having the function of detecting a magnetic field only in one direction can be employed and the configuration of the magnetic field detecting mechanism can be simplified.
• The system according to the first embodiment has an advantage such that the influence of earth magnetic components can be eliminated. To be specific, the magnetic field output direction from thepermanent magnet13 is the vertical direction, and themagnetic detectors6ato6hhave the function of detecting the intensity of magnetic field components in the vertical direction. On the other hand, the earth magnetic component travels in the direction almost perpendicular to the vertical direction, that is, almost in the horizontal direction. Consequently, themagnetic detectors6ato6hdo not inherently detect the intensity of the earth magnetic component. Without providing a special filtering mechanism, the influence of the earth magnetic component can be eliminated.
• A system for detecting a position of a capsule endoscope in a subject according to a second embodiment will now be explained. The system according to the second embodiment includes a capsule endoscope, as a device swallowed and passing through a subject, including not only the constant magnetic field generator but also a predetermined function executing unit and a radio unit; and a position processor for switching a plurality of antennas for receiving radio signals transmitted from the capsule endoscope based on the constant magnetic field generated by constant magnetic field generator and the result of detection of the position of the capsule endoscope in the subject.
• FIG. 7 is a schematic diagram of the system according to the second embodiment. As shown inFIG. 7, the system according to the second embodiment includes acapsule endoscope40 as an example of the device to be swallowed and passes through a subject, and aposition transducer41. Although elements corresponding to thedisplay4 and theportable recording medium5 in the first embodiment are not shown inFIG. 7, it does not mean that those elements are excluded in the second embodiment. In the system according to the second embodiment, elements having the same reference numerals and names as those of the first embodiment have the same configurations and actions as those of the first embodiment unless otherwise specified in the following.
• Theposition transducer41 includes, as shown inFIG. 7, themagnetic detectors6ato6h, fixingmembers7aand7bfor fixing themagnetic detectors6ato6hto thesubject1, receiving antennas A₁to A_nfor receiving radio signals transmitted from thecapsule endoscope40, and aposition processor42 for processing the information obtained by themagnetic detectors6ato6hand the receiving antennas A₁to A_nand deriving information of the position in thesubject1, of thecapsule endoscope40. Although not shown inFIG. 7, theposition transducer41 has the function of supplying a power supply signal or the like to thecapsule endoscope40 as is explained later and has power supply antennas B₁to B_mfor realizing the function.
• The receiving antennas A₁to A_nare to receive radio signals transmitted from thecapsule endoscope40. As is explained later, thecapsule endoscope40 in the second embodiment has the function of capturing an image of the inside of the subject1 and transmitting the image to the outside by radio. The receiving antennas A₁to A_nhave the configuration of receiving a radio signal transmitted from thecapsule endoscope40 and outputting it to theposition processor42. The receiving antennas A1 to An are constructed by, concretely, for example, a loop antenna and a fixing unit that fixes the loop antenna to thesubject1. When radio signals are transmitted from thecapsule endoscope40, the radio signals may be received by all of the receiving antennas A₁to A_n. However, in the second embodiment, the radio signal is received by using a receiving antenna that is determined to be most adapted to reception by anantenna selector57 that is explained later among the plurality of receiving antennas A₁to A_n.
• FIG. 8 is a block diagram of thecapsule endoscope40. Thecapsule endoscope40 has, like thetest capsule2 in the first embodiment, thepermanent magnet13 as the magnetic field generator. Further, thecapsule endoscope40 includes a light emitting diode (LED)43 functioning as a illuminating unit that illuminates an image capturing region at the time of capturing an image of the inside of the subject1; anLED driving circuit44 that controls a driving state of theLED43; a charge-coupled device (CCD)45 functioning as an image capturing unit for capturing a reflection light image from the region illuminated by theLED43; and aCCD driving circuit46 that controls a driving state of theCCD45. TheLED43,LED driving circuit44,CCD45, andCCD driving circuit46 are defined as afunction executing unit47 having a predetermined function as a whole.
• Thecapsule endoscope40 includes anRF transmitting unit48 that modulates image data captured by theCCD45, thereby generating an RF signal; a transmittingantenna unit49 as a radio unit for transmitting the RF signal output from theRF transmitting unit48 by radio; and asystem control circuit50 for controlling the operation of theLED driving circuit44,CCD driving circuit46, andRF transmitting unit48.
• By having the mechanisms, thecapsule endoscope40 obtains image data of a region to be tested that is illuminated by theLED43 by theCCD45 while thecapsule endoscope40 is introduced in thesubject1. The captured image data is converted to an RF signal by theRF transmitting unit48 and, after that, the RF signal is transmitted to the outside via the transmittingantenna unit49.
• Thecapsule endoscope40 also includes a receivingantenna unit51 for receiving a radio signal sent from theposition transducer41 side; and a separatingcircuit52 for separating the power supply signal from the signal received by the receivingantenna unit51. Thecapsule endoscope40 also includes apower reproducing circuit53 for reproducing power from the separated power supply signal; abooster circuit54 for boosting the reproduced power; and acapacitor55 for storing the boosted power. Thecapsule endoscope40 also includes a controlinformation detecting circuit56 for detecting a control information signal from the components separated from the power supply signal by the separatingcircuit52 and outputting the detected control information signal to thesystem control circuit50. Thesystem control circuit50 also includes the function of distributing drive power supplied from thecapacitor55 to the other elements.
• By having the mechanisms, first, thecapsule endoscope40 receives the radio signal sent from theposition transducer41 side by the receivingantenna unit51 and separates the power supply signal and the control information signal from the received radio signal by the separatingcircuit52. The control information signal separated by the separatingcircuit52 is output to thesystem control circuit50 via the controlinformation detecting circuit56 and used for driving and controlling theLED43,CCD45, andRF transmitting unit48. On the other hand, the power supply signal is reproduced as power by thepower reproducing circuit53. The potential of the reproduced power is boosted to potential adapted to thecapacitor55 by thebooster circuit54, and the boosted potential is stored in thecapacitor55.
• The configuration of theposition processor42 is explained.FIG. 9 is a block diagram of the positioninformation driving apparatus42. Theposition processor42 in the second embodiment has, as elements for detecting the position in thesubject1 of thecapsule endoscope40, thereference device selector35,magnetic selector36,distance calculator37, andposition calculator38. In the second embodiment, themagnetic detectors6ato6houtput not only the magnetic field intensity but also the magnetic field direction to theposition processor42, so that the second embodiment is different from the first embodiment with respect to the following points. Thereference device selector35 extracts the magnetic field intensity from the information output from themagnetic detectors6ato6hto select a reference device, and thedistance calculator37 has the function of deriving distance by extracting the magnetic field intensities received by the reference device and the selected devices from the information input from themagnetic selector36. The operation of detecting the position of thecapsule endoscope40 in the second embodiment is almost the same as that in the first embodiment and its detailed description will not be repeated.
• Theposition processor42 also includes the function of a receiving apparatus for receiving image data of the inside of the subject1, which is sent from thecapsule endoscope40 by radio. Concretely, theposition processor42 has: theantenna selector57 for selecting an antenna used for data reception from the receiving antennas A₁to A_n; anRF receiving unit58 that performs a predetermined process such as demodulation on a radio signal received by the selected receiving antenna, extracts image data captured by thecapsule endoscope40 from the radio signal, and outputs the extracted image data; animage processing unit59 for performing a necessary process on the output image data; and astorage unit60 for storing the processed image data.
• Theantenna selector57 selects the receiving antenna that is most adapted to receive the radio signal transmitted from thecapsule endoscope40. Concretely, theantenna selector57 grasps the positions of the receiving antennas A₁to A_nin advance and receives information of the position of thecapsule endoscope40 derived by theposition calculator38. Theantenna selector57 has the function of selecting a receiving antenna that is estimated to have the most excellent reception sensitivity based on the position of thecapsule endoscope40 and outputting a radio signal received by the selected receiving antenna to theRF receiving unit58.
• Thestorage unit60 has the function of storing image data output from theimage processing unit59 and the position of thecapsule endoscope40 at the time point the output image data is captured in a state where the image data and the position of thecapsule endoscope40 are associated with each other. Theposition processor42 has the configuration of outputting the information obtained by theposition calculator38 and theimage processing unit59 to thestorage unit60 as also shown inFIG. 9, and thestorage unit60 has the function of storing the information in the associated state. As a result, in thestorage unit60, the image data of a predetermined region in thesubject1 and the position of thecapsule endoscope40 at the time point the image data is captured is stored in a state where the image data and the position of thecapsule endoscope40 are associated with each other.
• Theposition processor42 also has the function of generating a power supply signal and the like transmitted to thecapsule endoscope40 and outputting the power supply signal to the power supply antennas B₁to B_m. Concretely, theposition processor42 includes anoscillator61 having the function of generating a power supply signal and the function of specifying an oscillation frequency; a controlinformation input unit62 that generates a control information signal for controlling the drive state of thecapsule endoscope40, amultiplexing circuit63 for combining the power supply signal and the control information signal; and anamplifier circuit64 for amplifying the intensity of the combined signal. The signal amplified by theamplifier circuit64 is sent to the power supply antennas B₁to B_mand transmitted to thecapsule endoscope40. Theposition processor42 includes apower supply unit65 having a predetermined storage, an AC power adapter, or the like, and the elements of theposition processor42 uses the power supplied from thepower supply unit65 as driving energy.
• The advantages of the system according to the second embodiment is explained. First, in the system according to the second embodiment, in a manner similar to the first embodiment, thecapsule endoscope40 includes therein thepermanent magnet13 and the position of thecapsule endoscope40 is detected based on the constant magnetic field output from thepermanent magnet13. As already mentioned above, the constant magnetic field has a characteristic that it attenuates almost unconditionally irrespective of the values such as dielectric constant, magnetic permeability, and the like in organs and the like in thesubject1. Consequently, there is an advantage such that the position of thecapsule endoscope40 can be accurately detected more than the case of performing position detection by using a radio signal.
• The system for detecting a position in a subject according to the second embodiment has a configuration that theantenna selector57 selects the receiving antenna based on the position of the derivedcapsule endoscope40. The reception sensitivity of the radio signal in the receiving antenna depends on the distance from thecapsule endoscope40 and the orientation of the transmittingantenna unit49 in thecapsule endoscope40. Therefore, a receiving antenna to be used can be accurately selected based on thecapsule endoscope40, and a position information detecting system capable of receiving a radio signal transmitted from thecapsule endoscope40 always at high sensitivity can be realized.
• Further, the system according to the second embodiment has a configuration of outputting image data of the inside of the subject1 captured and the derived position of thecapsule endoscope40 to thestorage unit60. Therefore, image data obtained by thecapsule endoscope40 and the derived position at the time of image capture of thecapsule endoscope40 can be stored so as to be associated with each other. At the time of displaying image data on thedisplay4, only the image data positioned in a predetermined range can be designated to be displayed. In other words, every image data is not displayed on thedisplay4 but image data of a region of interest of the user, for example, image data of only the small intestine can be displayed on thedisplay4. Thus, the position information detecting system that is convenient to doctors and the like can be realized.
• Although the invention has been described above by the first and second embodiments, the invention is not limited to the foregoing embodiments and various embodiments, modifications, and application examples can be made by those skilled in the art. For example, in the first and second embodiments, the plurality ofmagnetic detectors6 and themagnetic detector6 are disposed on the outer surface of the subject1 so as to detect the vertexes of a cube. However, the invention is not limited to the layout.
• With respect to themagnetic detectors6 and the like, it is sufficient to grasp relative positions to the subject1 in advance. By using the relative positions, position detection is possible without disposing themagnetic detectors6 in a cube shape. The number of themagnetic detectors6 and the like is not limited to eight. As the simplest configuration, a system using a singlemagnetic detector6 or the like can be constructed. Specifically, thetest capsule2 or thecapsule endoscope40 as the device to be introduced in the subject does not travel arbitrarily in the subject1 but travels along a path that is determined to a certain degree of predetermined organs such as esophagus, stomach, small intestine, large intestine, and the like. Therefore, it is possible to preliminarily grasp a travel path of the device to be introduced in a subject to a certain degree. The position of the device to be introduced in a subject can be detected by using the path information grasped in advance and the intensity of the constant magnetic field received by the single magnetic detector.
• Further, in the first and second embodiments, the reference device and the selected devices are selected by using thereference device selector35 and themagnetic selector36, and position detection is made based on the magnetic field intensities detected by the reference device and the selected devices. The configuration, however, is not essential to the invention. For example, it is also possible to derive the distance from thetest capsule2 orcapsule endoscope40 based on detected intensities with respect to all of themagnetic detectors6ato6hand generate eight ways of equations similar to Equations (2) to (5) to derive the position of thetest capsule2 or the like. In the case of the configuration, computation using, for example, the least square method is possible. Thus, there is an advantage such that an error of derivation of the position of thetest capsule2 or the like can be further reduced.
• Although thefunction executing unit47 having theCCD45 and the like as an image capturing unit and theLED43 and the like as an illuminating unit has been described in the second embodiment, thefunction executing unit47 may obtain, in addition to the above, information of pH and the temperature in thesubject1. A configuration that the device to be introduced in a subject has an oscillator to capture an ultrasonic image of the inside of the subject1 may be also employed. Further, a plurality of pieces of information may be obtained from the information of the inside of the subject.
• The radio signal output from the power supply antennas B₁to B_mis not always limited to a signal obtained by multiplexing the control information signal and the power supply signal. Further, radio transmission from the position transducer to the capsule endoscope may not be performed. The power supply signal and a signal other than the control information signal may be multiplexed and the resultant signal may be transmitted. Theposition transducer41 may receive only the radio signal output from the capsule endoscope. It is also possible to provide a storage unit in the capsule endoscope and, after the capsule endoscope is excreted to the outside of the subject, read information from the storage unit.
• Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.

Claims (6)

1-9. (canceled)

10. A system comprising:

a swallowable device that is swallowed and passes through a subject, the swallowable device includes;

a casing,

a first case member that is held in the casing,

a first spherical body that is disposed in the first case member,

a first liquid that fills a clearance between an inner surface of the first case member and an outer surface of the first spherical body,

a magnetic field generator that is disposed in the first spherical body and generates a constant magnetic field, an orientation of the magnetic field generator being irrespective of fluctuation in an orientation of the swallowable device, and

a first weighting member that is disposed in the first spherical body; and

a magnetic detector that includes

a second case member,

a second spherical body that is disposed in the second case member,

a second liquid that fills a clearance between an inner surface of the second case member and an outer surface of the second spherical body,

a magnetic sensor that is disposed in the second spherical body and detects an intensity of the constant magnetic field, an orientation of the magnetic sensor being irrespective of fluctuation in an orientation of the second case member,

a second weighting member that is disposed in the second spherical body,

a magnetic measurement controller that is disposed in the second spherical body and controls the magnetic sensor,

a first transmitting/receiving unit that is disposed in the second spherical body, connected to the magnetic measurement controller, and modulates/demodulates a signal at the time of performing radio communications with outside of the second spherical body, and

a second transmitting/receiving unit that is disposed outside of the second spherical body and modulates/demodulates a signal at the time of performing radio communications with the inside of the second spherical body.

11. The system according toclaim 10, wherein:

the first weighting member is arranged on a line extended from the magnetic field generator, the line being in a direction of the constant magnetic field in the magnetic field generator, and

the second weighting member is arranged on a line extended from the magnetic sensor, the line being in a direction of the magnetic field detection.

12. The system according toclaim 10, wherein a direction of the constant magnetic field in the magnetic field generator is parallel to a direction of the magnetic field detection.

13. The system according toclaim 10, further comprising a position processor that is disposed outside of the second spherical body and calculates a position of the swallowable device in the subject based on the intensity of the magnetic field detected by the magnetic detector.

14. The system according toclaim 10, further comprising:

the magnetic detector that further includes;

a power supplying antenna that is disposed outside of the second spherical body and transmits a power supply signal to inside of the second spherical body,

a power supply unit that is disposed outside of the second spherical body and electrically connected to the power supplying antenna,

a controller that is disposed outside of the second spherical body and electrically connected to the power supply unit and the second transmitting/receiving unit,

a power receiving antenna that is disposed in the second spherical body and receives the power supply signal transmitted from outside of the second spherical body,

a power receiving unit that is disposed in the second spherical body and converts the power supply signal transmitted from the outside to power, and

a capacitor that is disposed in the second spherical body and holds the power converted at the power receiving unit.

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