JP2006075534A - Position detection apparatus and intra-patient introduction system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect noise magnetic field accurately and to suppress a deterioration in accuracy of position detection in a position detection apparatus that detects the position of a detection object using position detection magnetic field having position dependency. <P>SOLUTION: A processing device 12, which is a constituent of the position detection apparatus, has a judgment section 50 and an alarm display section 51. Magnetic field strength detected by a noise magnetic field sensor 13 arranged on the outer surface of a subject is entered into the judgment section, and magnetic field strength detected by a capsule endoscope, which is the detection object, is also entered into the judgment section via a signal processing section 39 or the like. The alarm display section displays a predetermined alarm according to a judgment result of the judgment section 50. The judgment section 50 determines whether a difference value between the magnetic field detected by the noise magnetic field sensor 13 arranged on the outer surface of the subject and the magnetic field detected by the capsule endoscope located within the subject exceeds a predetermined threshold or not, and judges whether a noise magnetic field is generated or not on the basis of the result. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for detecting a positional relationship between a target coordinate axis fixed with respect to a detection target and a reference coordinate axis set regardless of the motion of the detection target using a predetermined magnetic field. .

  In recent years, in the field of endoscopes, swallowable capsule endoscopes have been proposed. This capsule endoscope is provided with an imaging function and a wireless communication function. The capsule endoscope is swallowed from the mouth of the subject for observation (examination) until it is spontaneously discharged until it is spontaneously discharged. It has the function of moving and capturing images sequentially.

  While moving inside the body cavity, image data captured inside the body by the capsule endoscope is sequentially transmitted to the outside by wireless communication and stored in a memory provided outside. By carrying a receiver having a wireless communication function and a memory function, the subject can freely act after swallowing the capsule endoscope and before being discharged. After the capsule endoscope is ejected, a doctor or a nurse can make a diagnosis by displaying an image of an organ on a display based on image data stored in a memory (see, for example, Patent Document 1). .)

  Further, a conventional capsule endoscope system has been proposed that includes a mechanism for detecting the position of the capsule endoscope in the body cavity. For example, a magnetic field having a position dependency with respect to strength is formed inside a subject to which a capsule endoscope is introduced, and the inside of the subject is determined based on the strength of the magnetic field detected by a magnetic field sensor built in the capsule endoscope. It is possible to detect the position of the capsule endoscope. In such a capsule endoscope system, in order to form a magnetic field, a configuration in which a predetermined coil is arranged outside the subject is adopted, and a magnetic field is generated inside the subject by flowing a predetermined current through the coil. Trying to form. Here, since it is difficult to detect the position of the capsule endoscope in advance, the magnetic field to be formed is the capsule endoscope in all regions where the capsule endoscope can exist in the subject. Must be formed to have a detectable intensity. Specifically, in a conventional capsule endoscope system, a magnetic field that can be detected by the capsule endoscope is formed in all digestive organs from the oral cavity to the anus.

Japanese Patent Laid-Open No. 2003-19111

  However, the conventional capsule endoscope system provided with the position detection mechanism has a problem that the detection accuracy decreases due to the presence of the external noise magnetic field. That is, as a mechanism for detecting the position of the capsule endoscope, the capsule endoscope has a mechanism for detecting a magnetic field. In addition to a position detection magnetic field formed for position detection, an external electronic device A noise magnetic field caused by the above will be detected. Depending on the magnetic field sensor provided in the capsule endoscope, it is difficult to determine whether the detected magnetic field is a position detection magnetic field or a noise magnetic field, and noise is detected in the region where the capsule endoscope is located. When a magnetic field is formed, the strength and / or direction of the detected magnetic field is affected, so that the position detection accuracy is lowered.

  The present invention has been made in view of the above, and includes a position detection device that performs position detection of an in-subject introduction device such as a capsule endoscope using a position detection magnetic field having position dependency. An object of the present invention is to realize a position detection apparatus and an in-subject introduction system that detect a noise magnetic field with high accuracy and suppress a decrease in position detection accuracy in the in-subject introduction system.

  In order to solve the above-described problems and achieve the object, a position detection apparatus according to claim 1 is a position detection apparatus that detects a position of a detection target using a predetermined position detection magnetic field, and the position detection apparatus includes: Magnetic field forming means for forming a magnetic field for use, position derivation means for deriving the position of the detection target based on the strength of the magnetic field for position detection detected at a position where the detection target exists, and magnetic field strength for detecting the magnetic field strength It is characterized by comprising detection means and determination means for determining whether or not a noise magnetic field is formed in a region where the detection target is located based on the strength of the magnetic field detected by the magnetic field strength detection means. .

  According to the first aspect of the present invention, since the determination means for determining whether or not the noise magnetic field is formed at the position where the detection target exists, the noise magnetic field is mixed in addition to the position detection magnetic field. It is possible to detect that a noise magnetic field is formed.

  According to a second aspect of the present invention, in the above invention, the determination unit includes: a magnetic field intensity detected by the magnetic field intensity detection unit; and a magnetic field intensity detected in a region where the detection target is located. It is determined that a noise magnetic field is formed when the difference value between the two values exceeds a predetermined threshold value.

  According to a third aspect of the present invention, in the above position detection apparatus, the determination unit may form a noise magnetic field when the strength of the magnetic field detected by the magnetic field strength detection unit exceeds a predetermined threshold. It is characterized by determining that it is.

  According to a fourth aspect of the present invention, in the above invention, the threshold is larger than the strength of geomagnetism.

  According to a fifth aspect of the present invention, in the above invention, the position detection device further includes a warning unit that performs a predetermined warning when the determination unit determines that a noise magnetic field is formed. To do.

  In the position detection device according to a sixth aspect of the present invention, in the above invention, the position detection magnetic field includes a first linear magnetic field having a predetermined traveling direction and a second linear magnetic field having a traveling direction different from the first linear magnetic field. And a correspondence relationship between the traveling directions of the first linear magnetic field on a target coordinate axis fixed to the detection target and on a reference coordinate axis that is different from the target coordinate axis, and the second linear magnetic field The apparatus further comprises azimuth deriving means for deriving an azimuth formed by the target coordinate axis with respect to the reference coordinate axis based on a correspondence relationship between the traveling direction on the target coordinate axis and the traveling direction on the reference coordinate axis.

  According to a seventh aspect of the present invention, in the above-described invention, the first linear magnetic field is formed by terrestrial magnetism, arranged at a predetermined position on the reference coordinate axis, and forms the second linear magnetic field. A magnetic field forming unit; and a magnetic field sensor unit that detects a traveling direction of the geomagnetism in the reference coordinate axis, and the azimuth deriving unit includes a traveling direction of the geomagnetism in the reference coordinate axis detected by the magnetic field sensor unit. The azimuth is derived based on a traveling direction of the second linear magnetic field on the predetermined reference coordinate axis and a traveling direction of the geomagnetism on the target coordinate axis detected by the detection target.

  An in-subject introduction system according to an eighth aspect of the present invention includes an intra-subject introduction apparatus that is introduced into a subject and moves inside the subject, and a predetermined position detection magnetic field inside the subject. An intra-subject introduction system comprising a position detection device for detecting a position of the intra-subject introduction device, wherein the intra-subject introduction device is used for position detection in a region where the intra-subject introduction device is located. A magnetic field sensor that detects a magnetic field; and a wireless transmission unit that transmits a wireless signal including a detection result of the magnetic field sensor, wherein the position detection device includes a magnetic field forming unit that forms the magnetic field for position detection, and the magnetic field sensor. Position deriving means for deriving the position of the in-subject introduction device based on the intensity of the position detecting magnetic field detected by the magnetic field intensity detecting means; Based on the intensity of the detected magnetic field by, wherein the detection target and a determining means for determining whether the noise magnetic field in a region located is formed.

  Since the position detection apparatus and the in-subject introduction system according to the present invention include determination means for determining whether or not the noise magnetic field is formed at the position where the detection target exists, the noise magnetic field in addition to the position detection magnetic field is provided. This produces an effect that it is possible to detect that a noise magnetic field is formed in the case where the noise is mixed.

  Hereinafter, a position detection apparatus and an in-subject introduction system, which are the best modes for carrying out the present invention (hereinafter simply referred to as “embodiments”), will be described. Note that the drawings are schematic, and it should be noted that the relationship between the thickness and width of each part, the ratio of the thickness of each part, and the like are different from the actual ones. Of course, the part from which the relationship and ratio of a mutual dimension differ is contained. In the following description, a technique using geomagnetism, a linear magnetic field, and a diffusion magnetic field will be described as an example of the position detection mechanism. However, it should be understood that the present invention should not be limited to such a configuration and is position dependent. The present invention can be applied as long as the position of the detection target is detected over a plurality of times using a position detection magnetic field having the property.

(Embodiment 1)
First, the in-subject introduction system according to the first embodiment will be described. In the first embodiment, the overall configuration and each component of the in-subject introduction system will be described, the position detection mechanism will be described, and then the control mechanism related to the strength of the position detection magnetic field used for position detection will be described. I will do it.

  FIG. 1 is a schematic diagram illustrating the overall configuration of the intra-subject introduction system according to the first embodiment. As shown in FIG. 1, the in-subject introduction system according to the first embodiment includes a capsule endoscope 2 that is introduced into the subject 1 and moves along a passage route, and a capsule endoscope. A position detection device 3 that performs wireless communication with the camera 2 and detects a positional relationship between a target coordinate axis fixed to the capsule endoscope 2 and a reference coordinate axis fixed to the subject 1; In order to exchange information between the display device 4 that displays the contents of the radio signal transmitted from the capsule endoscope 2 and received by the position detection device 3, and between the position detection device 3 and the display device 4. The portable recording medium 5 is provided. As shown in FIG. 1, in the first embodiment, an object coordinate axis that is a coordinate axis that is formed by the X axis, the Y axis, and the Z axis and is fixed to the capsule endoscope 2, and the x axis, It is formed by the y-axis and the z-axis, is determined regardless of the movement of the capsule endoscope 2, and specifically sets a reference coordinate axis that is a coordinate axis fixed with respect to the subject 1, The positional relationship of the target coordinate axis with respect to the reference coordinate axis is detected using the mechanism described in (1).

  The display device 4 is for displaying an in-vivo image captured by the capsule endoscope 2 received by the position detection device 3 and is based on data obtained by the portable recording medium 5. It has a configuration such as a workstation that performs image display. Specifically, the display device 4 may be configured to directly display an image or the like by a CRT display, a liquid crystal display, or the like, or may be configured to output an image or the like to another medium such as a printer.

  The portable recording medium 5 can be attached to and detached from the processing device 12 and the display device 4 described later, and has a structure capable of outputting and recording information when attached to both. Specifically, the portable recording medium 5 is attached to the processing device 12 while the capsule endoscope 2 is moving in the body cavity of the subject 1, and the target coordinate axis with respect to the in-subject image and the reference coordinate axis. The positional relationship is stored. Then, after the capsule endoscope 2 is discharged from the subject 1, the capsule endoscope 2 is taken out from the processing device 12 and mounted on the display device 4, and the recorded data is read out by the display device 4. When data is transferred between the processing device 12 and the display device 4 using a portable recording medium 5 such as a compact flash (registered trademark) memory, the processing device 12 and the display device 4 are connected by wire. Unlike the capsule endoscope 2, the subject 1 can freely move even when the capsule endoscope 2 is moving inside the subject 1.

  Next, the capsule endoscope 2 will be described. The capsule endoscope 2 functions as an example of a detection target in the claims. Specifically, the capsule endoscope 2 is introduced into the subject 1, acquires in-subject information while moving in the subject 1, and transmits a radio signal including the acquired in-subject information to the outside It has the function to transmit to. In addition, the capsule endoscope 2 has a magnetic field detection function for detecting a positional relationship, which will be described later, and has a configuration in which driving power is supplied from the outside. Specifically, a radio signal transmitted from the outside is received. It has a function of receiving and reproducing the received radio signal as drive power.

  FIG. 2 is a block diagram showing a configuration of the capsule endoscope 2. As shown in FIG. 2, the capsule endoscope 2 functions as a mechanism for acquiring in-subject information. In-subject information acquisition unit 14 for acquiring in-subject information and the acquired in-subject information And a signal processing unit 15 for performing predetermined processing. The capsule endoscope 2 detects a magnetic field as a magnetic field detection mechanism, outputs a magnetic signal corresponding to the detected magnetic field, an amplifying unit 17 for amplifying the output electric signal, and an amplification And an A / D converter 18 that converts the electrical signal output from the unit 17 into a digital signal.

  The in-subject information acquisition unit 14 is for acquiring in-subject information, that is, an in-subject image as image data in the subject in the first embodiment. Specifically, the in-subject information acquisition unit 14 is an LED 22 that functions as an illumination unit, an LED drive circuit 23 that controls driving of the LED 22, and an imaging unit that captures at least a part of a region illuminated by the LED 22. A functioning CCD 24 and a CCD driving circuit 25 for controlling the driving state of the CCD 24 are provided. In addition, as a specific structure of an illumination part and an imaging part, it is not essential to use LED and CCD, For example, it is good also as using CMOS etc. as an imaging part.

  The magnetic field sensor 16 is for detecting the direction and intensity of the magnetic field formed in the region where the capsule endoscope 2 is present. Specifically, the magnetic field sensor 16 is formed using, for example, an MI (Magneto Impedance) sensor. The MI sensor has a configuration in which, for example, an FeCoSiB amorphous wire is used as a magnetosensitive medium. When a high frequency current is applied to the magnetosensitive medium, the MI impedance of the magnetosensitive medium greatly changes due to an external magnetic field. The magnetic field strength is detected using the effect. In addition to the MI sensor, the magnetic field sensor 16 may be configured using, for example, an MRE (magnetoresistive effect) element, a GMR (giant magnetoresistive effect) magnetic sensor, or the like.

  As shown in FIG. 1, in the first embodiment, a target coordinate axis defined by the X axis, the Y axis, and the Z axis is assumed as the coordinate axis of the capsule endoscope 2 to be detected. Corresponding to the target coordinate axis, the magnetic field sensor 16 detects the magnetic field strengths of the X direction component, the Y direction component, and the Z direction component for the magnetic field formed in the region where the capsule endoscope 2 is located, It has a function of outputting an electrical signal corresponding to the magnetic field strength in the direction. The magnetic field strength component on the target coordinate axis detected by the magnetic field sensor 16 is transmitted to the position detection device 3 via the wireless transmission unit 19 described later, and the position detection device 3 detects the value of the magnetic field component detected by the magnetic field sensor 16. Based on this, the positional relationship between the target coordinate axis and the reference coordinate axis is derived.

  Further, the capsule endoscope 2 includes a transmission circuit 26 and a transmission antenna 27, and performs signal processing on a wireless transmission unit 19 for performing wireless transmission to the outside and a signal output to the wireless transmission unit 19. And a switching unit 20 that appropriately switches between the output from the unit 15 and the output from the A / D conversion unit 18. Further, the capsule endoscope 2 includes a timing generation unit 21 for synchronizing the drive timings of the in-subject information acquisition unit 14, the signal processing unit 15, and the switching unit 20.

  The capsule endoscope 2 has a receiving antenna 28 and a power regeneration circuit that regenerates power from the radio signal received via the receiving antenna 28 as a mechanism for receiving a wireless signal for power feeding from the outside. 29, a booster circuit 30 that boosts the voltage of the power signal output from the power regeneration circuit 29, and a power signal that has been changed to a predetermined voltage by the booster circuit 30 is stored and supplied as drive power for the other components described above. The storage battery 31 is provided.

  The reception antenna 28 is formed using, for example, a loop antenna. Such a loop antenna is fixed at a predetermined position in the capsule endoscope 2, and is specifically arranged to have a predetermined position and a directing direction on a target coordinate axis fixed to the capsule endoscope 2. ing.

  Next, the position detection device 3 will be described. As shown in FIG. 1, the position detection device 3 includes receiving antennas 7 a to 7 d for receiving a radio signal transmitted from the capsule endoscope 2, and a radio for supplying power to the capsule endoscope 2. Transmitting antennas 8a to 8d for transmitting signals, a geomagnetic sensor 9 for detecting the traveling direction of geomagnetism, a linear magnetic field forming unit 10 for forming a linear magnetic field, a diffusion magnetic field forming unit 11 for forming a diffusion magnetic field, and reception The processing apparatus 12 which performs a predetermined | prescribed process with respect to the radio signal etc. which were received via antenna 7a-7d, and the noise magnetic field sensor 13 used in the case of a noise magnetic field detection are provided. Note that FIG. 1 is a schematic diagram only, and the receiving antennas 7a to 7d and the like are schematically shown with respect to the configuration and are merely examples of the positions where they are arranged. That is, it should be noted that the positional relationship between the components shown in FIG. 1, particularly the positional relationship on the subject 1, is not limited to the example shown in FIG.

  The receiving antennas 7a to 7d are for receiving radio signals transmitted from the radio transmitting unit 19 provided in the capsule endoscope 2. Specifically, the receiving antennas 7a to 7d are formed by a loop antenna or the like, and have a function of transmitting a received radio signal to the processing device 12.

  The transmission antennas 8 a to 8 d are for transmitting the radio signal generated by the processing device 12 to the capsule endoscope 2. Specifically, the transmission antennas 8 a to 8 d are formed by a loop antenna or the like that is electrically connected to the processing device 12.

  The geomagnetic sensor 9 is for detecting the direction of travel of geomagnetism. In the in-subject introduction system according to the first embodiment, as will be described in detail later, since the geomagnetism is also used as a position detection magnetic field, the subject 1 (more precisely, the subject 1 is not affected). It becomes necessary to detect the traveling direction of geomagnetism with respect to a fixed reference coordinate axis), and the geomagnetic sensor 9 has a function of detecting the traveling direction. In addition, from the viewpoint of realizing such a function, it is sufficient that the geomagnetic sensor 9 has a function of detecting only the magnetic field direction at the arranged position. The same configuration as that of the magnetic field sensor 16 provided is used. In the first embodiment, the geomagnetism functions as an example of the position detection magnetic field and the first linear magnetic field in the claims.

  Next, the linear magnetic field forming unit 10 and the diffusion magnetic field forming unit 11 will be described. Each of the linear magnetic field forming unit 10 and the diffusion magnetic field forming unit 11 functions as an example of a magnetic field forming unit in the claims, and the formed linear magnetic field and the diffusion magnetic field are the position detection magnetic fields in the claims. It functions as an example.

  The linear magnetic field forming unit 10 is for forming a linear magnetic field (corresponding to the second linear magnetic field in the claims) that is a linear magnetic field that travels in a direction different from the geomagnetism. Here, the “linear magnetic field” refers to a magnetic field component substantially only in one direction in at least a predetermined spatial region, in this first embodiment, in a spatial region where the capsule endoscope 2 inside the subject 1 can be located. The magnetic field. Unlike the linear magnetic field forming unit 10, the diffusion magnetic field forming unit 11 forms a diffusion magnetic field in which the magnetic field direction is position-dependent, that is, a magnetic field that diffuses as the distance from the diffusion magnetic field forming unit 11 increases in the first embodiment. Is for.

  FIG. 3 is a schematic diagram showing the configuration of the linear magnetic field forming unit 10 and the diffusion magnetic field forming unit 11 and the mode of the linear magnetic field formed by the linear magnetic field forming unit 10. As shown in FIG. 3, the linear magnetic field forming unit 10 extends in the y-axis direction on the reference coordinate axis, and supplies a current to the coil 32 that is formed so that the coil cross section is parallel to the xz plane. Current source 33. For this reason, as shown in FIG. 3, the linear magnetic field formed by the coil 32 is a linear magnetic field at least inside the subject 1, and the intensity gradually decreases as the distance from the coil 32 increases. It will have dependency.

  The diffusion magnetic field forming unit 11 includes a coil 34 and a current source 35 for supplying current to the coil 34. Here, the coil 32 is arranged to form a magnetic field having a traveling direction in a predetermined direction. In the case of the first embodiment, the traveling direction of the linear magnetic field formed by the coil 32 is the reference coordinate axis. In the y-axis direction. Further, the coil 34 is fixed at a position where a diffusion magnetic field that is the same as the magnetic field direction stored in the magnetic force line direction database 42 described later is formed.

  FIG. 4 is a schematic diagram showing an aspect of the diffusion magnetic field formed by the diffusion magnetic field forming unit 11. As shown in FIG. 4, the coil 34 provided in the diffusion magnetic field forming unit 11 is formed in a spiral shape on the surface of the subject 1, and the diffusion magnetic field formed by the diffusion magnetic field forming unit 11 is shown in FIG. Thus, in the magnetic field formed by the coil 34 (not shown in FIG. 4), the magnetic lines of force are once diffused radially and are incident on the coil 34 again.

  In the first embodiment, the linear magnetic field forming unit 10 and the diffusion magnetic field forming unit 11 form magnetic fields at different times. That is, in the first embodiment, the linear magnetic field forming unit 10 or the like does not form a magnetic field at the same time but forms a magnetic field according to a predetermined order, and the magnetic field sensor 16 provided in the capsule endoscope 2 includes The geomagnetism, linear magnetic field, and diffusion magnetic field are detected separately.

  Next, the noise magnetic field sensor 13 will be described. The noise magnetic field sensor 13 functions as an example of the magnetic field strength detection means in the claims. Specifically, the noise magnetic field sensor 13 is disposed at a predetermined position on the outer surface of the subject 1 and has a function of detecting at least the magnetic field strength with respect to the magnetic field at the disposed position. Although referred to as a “noise magnetic field sensor”, it is not necessary to adopt a configuration that detects only the noise magnetic field by filtering the geomagnetism, linear magnetic field, etc., and as will be apparent from the following description, a specific structure The same configuration as the magnetic field sensor 16 and the geomagnetic sensor 9 provided in the capsule endoscope 2 may be employed.

  Next, the configuration of the processing device 12 will be described. FIG. 5 is a block diagram schematically showing a specific configuration of the processing device 12. First, the processing device 12 has a function of performing reception processing of a radio signal transmitted by the capsule endoscope 2, and a reception antenna selection that selects any one of the reception antennas 7a to 7d corresponding to the function. Unit 37, a receiving circuit 38 for extracting the original signal included in the radio signal by performing demodulation processing or the like on the radio signal received via the selected receiving antenna, and processing the extracted original signal And a signal processing unit 39 for reconstructing an image signal and the like.

Specifically, the signal processing unit 39 has a function of reconstructing the magnetic field signals S _{1 to} S ₃ and the image signal S ₄ based on the extracted original signal and outputting them to appropriate components. Here, the magnetic field signals S _{1 to} S ₃ are magnetic field signals corresponding to the geomagnetism, the linear magnetic field, and the diffusion magnetic field detected by the magnetic field sensor 16, respectively. The image signal S ₄ corresponds to the in-subject image acquired by the in-subject information acquisition unit 14. The specific form of the magnetic field signals S _{1 to} S ₃ is expressed by a direction vector corresponding to the detected magnetic field intensity on the target coordinate axis fixed with respect to the capsule endoscope 2, and the magnetic field traveling direction on the target coordinate axis. And information on magnetic field strength. The image signal S ₄ is output to the recording unit 43. The recording unit 43 is for outputting input data to the portable recording medium 5, and records not only the image signal S ₄ but also the result of position detection, which will be described later, on the portable recording medium 5. Has the function of

The processing device 12 is fixed to the subject 1 and the function of detecting the position of the capsule endoscope 2 in the subject 1 based on the magnetic field intensity detected by the capsule endoscope 2. A function of detecting an orientation formed by the target coordinate axis fixed with respect to the capsule endoscope 2 with respect to the reference coordinate axis. Specifically, among the signals transmitted by the capsule endoscope 2 and output by the signal processing unit 39, the object for the reference coordinate axis based on the magnetic field signals S ₁ and S ₂ corresponding to the detected intensities of the geomagnetism and the linear magnetic field. Using the azimuth deriving unit 40 for deriving the azimuth formed by the coordinate axes, the magnetic field signal S ₃ and the magnetic field signal S ₂ corresponding to the detection intensity of the diffusion magnetic field, and the derivation result of the azimuth deriving unit 40, A position deriving unit 41 for deriving a position, and a magnetic force line azimuth database 42 that records a correspondence relationship between a traveling direction and a position of magnetic force lines constituting a diffusion magnetic field when the position deriving unit 41 derives a position. The azimuth derivation and position derivation by these components will be described in detail later.

  Further, the processing device 12 has a function of wirelessly transmitting drive power to the capsule endoscope 2, and includes an oscillator 44 that defines a frequency of a wireless signal to be transmitted, and an intensity of the wireless signal output from the oscillator 44. And a transmission antenna selection unit 47 that selects a transmission antenna to be used for transmitting a radio signal. Such a radio signal is received by the receiving antenna 28 provided in the capsule endoscope 2 and functions as driving power for the capsule endoscope 2.

  Further, the processing device 12 includes a selection control unit 48 that controls an antenna selection mode by the reception antenna selection unit 37 and the transmission antenna selection unit 47. The selection control unit 48 is based on the azimuth and position of the capsule endoscope 2 derived by the azimuth deriving unit 40 and the position deriving unit 41, respectively, and the transmission antenna 8 and reception most suitable for transmission / reception with respect to the capsule endoscope 2 A function of selecting the antenna 7 is provided. Further, the processing device 12 includes a power supply unit 51 having a function of supplying driving power to each component.

  In addition, the processing device 12 includes a geomagnetic azimuth deriving unit 49 that derives the traveling direction of geomagnetism. The geomagnetic azimuth deriving unit 49 has a function of deriving the advancing direction of geomagnetism on the reference coordinate axis based on the detection result of the geomagnetic sensor 9. The advancing direction of the geomagnetism derived by the geomagnetic azimuth deriving unit 49 is output to the azimuth deriving unit 40 and used in the azimuth deriving process described later.

  Furthermore, the processing device 12 has a function of detecting the presence or absence of a noise magnetic field. In order to realize such a function, the processing device 12 affects the accuracy of position detection in the region where the subject 1 is located, more precisely in the region where the capsule endoscope 2 is located inside the subject. The determination part 50 which determines whether the noise magnetic field is formed, and the warning display part 51 which displays a predetermined warning according to the determination result by the determination part 50 are provided.

  The determination part 50 is for determining the presence or absence of a noise magnetic field. Specifically, the determination unit 50 includes the magnetic field strength detected by the noise magnetic field sensor 13 and the magnetic field strength detected by the magnetic field sensor 16 included in the capsule endoscope 2 reconfigured by the signal processing unit 39. And a function of determining the presence or absence of a noise magnetic field using these magnetic field strengths. The determination process related to the noise magnetic field performed by the determination unit 50 will be described in detail later.

  The warning display unit 51 is for notifying the user of the presence of the noise magnetic field by displaying a predetermined warning when the presence of the noise magnetic field is clarified by the determination by the determination unit 50. The specific configuration may be any as long as it fulfills the above functions, for example, a configuration including a light emitting element such as an LED that emits light when a noise magnetic field is present, or a configuration that emits a warning sound. May be adopted.

  Next, the operation of the intra-subject introduction system according to the first embodiment will be described. Hereinafter, after describing the position detection mechanism of the capsule endoscope 2 to be detected, the detection mechanism of the noise magnetic field will be described.

  First, the position detection mechanism of the capsule endoscope 2 will be described. In the intra-subject introduction system according to the first embodiment, a positional relationship is derived between a reference coordinate axis fixed with respect to the subject 1 and a target coordinate axis fixed with respect to the capsule endoscope 2. Specifically, after deriving the azimuth of the target coordinate axis with respect to the reference coordinate axis, using the derived azimuth, the position of the origin of the target coordinate axis on the reference coordinate axis, that is, within the capsule type inside the subject 1 The position of the endoscope 2 is derived. Therefore, in the following description, after describing the azimuth derivation mechanism, the position derivation mechanism using the derived azimuth will be described. is there.

  The direction deriving mechanism performed by the direction deriving unit 40 will be described. FIG. 6 is a schematic diagram showing the relationship between the reference coordinate axis and the target coordinate axis when the capsule endoscope 2 is moving in the subject 1. As already described, the capsule endoscope 2 travels along the passage path inside the subject 1 and rotates by a predetermined angle with the traveling direction as an axis. Accordingly, the target coordinate axis fixed with respect to the capsule endoscope 2 causes a azimuth shift as shown in FIG. 6 with respect to the reference coordinate axis fixed with respect to the subject 1.

  On the other hand, the linear magnetic field forming unit 10 is fixed to the subject 1. Accordingly, the linear magnetic field formed by the linear magnetic field forming unit 10 proceeds in a certain direction with respect to the reference coordinate axis, specifically, in the y-axis direction.

  The azimuth | direction derivation in this Embodiment 1 is performed using this geomagnetism and a linear magnetic field. Specifically, first, the magnetic field sensor 16 provided in the capsule endoscope 2 detects the traveling direction of the geomagnetism and the linear magnetic field on the target coordinate axis. The magnetic field sensor 16 is configured to detect magnetic field components in the X-axis direction, the Y-axis direction, and the Z-axis direction in the target coordinate axis, and information regarding the detected traveling direction of the geomagnetic and linear magnetic fields in the target coordinate axis is wirelessly transmitted. It is transmitted to the position detection device 3 via the unit 19.

The radio signal transmitted by the capsule endoscope 2 is processed as the magnetic field signals S ₁ and S ₂ through processing by the signal processing unit 39 and the like. For example, in the example of FIG. 6, the magnetic field signal S ₁ includes information on coordinates (X ₁ , Y ₁ , Z ₁ ) as the geomagnetic progression direction, and the magnetic field signal S ₂ includes the linear magnetic field progression direction. Includes information on coordinates (X ₂ , Y ₂ , Z ₂ ). On the other hand, the orientation deriving unit 40 receives the magnetic field signals S ₁ and S ₂ and derives the orientation of the target coordinate axis with respect to the reference coordinate axis. Specific processing is as follows.

  First, the direction deriving unit 40 grasps the traveling direction of the linear magnetic field and the geomagnetism on the reference coordinate axis fixed with respect to the subject 1. Specifically, as described above, the linear magnetic field forming unit 10 is fixed to the subject 1, and the traveling direction of the formed linear magnetic field is a known direction (in the first embodiment, as described above, y Therefore, the direction deriving unit 40 grasps in advance the traveling direction of the linear magnetic field on the reference coordinate axis. Further, the traveling direction of geomagnetism is grasped by the action of the geomagnetic sensor 9 and the geomagnetic direction deriving unit 49. That is, the geomagnetic sensor 9 has a function of detecting each component on the reference coordinate axis with respect to the geomagnetism, and the azimuth deriving unit 40 operates on the reference coordinate axis by the detection result of the geomagnetic sensor 9 and the processing of the geomagnetic azimuth deriving unit 49 for the detection result. Know the direction of geomagnetism.

  As a result, regarding the linear magnetic field and the geomagnetism, the azimuth deriving unit 40 grasps the traveling directions of the target coordinate axis and the reference coordinate axis, and the correspondence between the target coordinate axis and the reference coordinate axis becomes clear. Thereafter, by performing a predetermined coordinate conversion process, the coordinates in the reference coordinate axis are derived with respect to the X axis, the Y axis, and the Z axis in the target coordinate axis, and the coordinates are output as azimuth information. The above is the direction deriving mechanism by the direction deriving unit 40.

Next, the position deriving mechanism of the capsule endoscope 2 by the position deriving unit 41 will be described. The position deriving unit 41 has a configuration in which magnetic field signals S ₂ and S ₃ are input from the signal processing unit 39, azimuth information is input from the azimuth deriving unit 40, and information stored in the magnetic force line azimuth database 42 is input. . The position deriving unit 41 derives the position of the capsule endoscope 2 as follows based on the input information.

First, the position deriving unit 41 uses the magnetic field signal S _2, performs the derivation of the distance between the linear magnetic field generator 10 and the capsule endoscope 2. The magnetic field signal S ₂ corresponds to the detection result of the linear magnetic field in the region where the capsule endoscope 2 exists, and the linear magnetic field corresponds to the linear magnetic field forming unit 10 being arranged outside the subject 1. Thus, it has a characteristic that its strength attenuates as the distance from the linear magnetic field forming unit 10 increases. By utilizing such properties, the position deriving unit 41 (determined from the current value to be supplied to the linear magnetic field generator 10) the intensity of the linear magnetic field in the linear magnetic field generator 10 near the capsule endoscope which is obtained from the magnetic field signal S ₂ 2 is compared with the intensity of the linear magnetic field in the existence region 2 to derive the distance r between the linear magnetic field forming unit 10 and the capsule endoscope 2. As a result of deriving the distance r, as shown in FIG. 7, it is clear that the capsule endoscope 2 is located on the curved surface 52 that is a set of points separated from the linear magnetic field forming unit 10 by the distance r. .

Then, the position deriving unit 41 derives the position on the curved surface 52 of the capsule endoscope 2 based on the magnetic field signal S ₃ , the direction information derived by the direction deriving unit 40 and the information stored in the magnetic force direction database 42. . Specifically, based on the magnetic field signal S ₃ and orientation information, to derive the traveling direction of the diffusion field at the location of the capsule endoscope 2. Since the magnetic field signal S ₃ is a signal corresponding to the result of detecting the diffusion magnetic field based on the target coordinate axis, the direction of the diffusion magnetic field based on the magnetic field signal S ₃ is coordinated from the target coordinate axis to the reference coordinate axis using the azimuth information. By performing the conversion process, the traveling direction of the diffusion magnetic field on the reference coordinate axis at the position where the capsule endoscope 2 exists is derived. Since the magnetic field direction database 42 records the correspondence between the traveling direction and position of the diffusion magnetic field on the reference coordinate axis, the position deriving unit 41 is stored in the magnetic field direction database 42 as shown in FIG. The position corresponding to the traveling direction of the diffusion magnetic field derived by referring to the information is derived, and the derived position is specified as the position of the capsule endoscope 2. The position derivation mechanism by the position derivation unit 41 has been described above.

  Next, a determination mechanism for the presence / absence of a noise magnetic field performed by the determination unit 50 will be described. FIG. 9 is a flowchart for explaining the determination process performed by the determination unit 50. Hereinafter, the determination mechanism will be described with reference to FIG.

First, the determination unit 50 acquires the intensity P _{1 of} the magnetic field detected by the magnetic field sensor 16 included in the capsule endoscope 2 at a predetermined time via the signal processing unit 39 (step S101). Then, the determination unit 50 acquires the strength P _{2 of} the magnetic field detected by the noise magnetic field sensor 13 at the same time as the predetermined time (step S102), and the difference value between the magnetic field strength P ₁ and the magnetic field strength P ₂ is predetermined. It is determined whether or not the threshold value ΔP ₀ is greater than (step S103). When the difference value is larger than the threshold value ΔP ₀ (step S103, Yes), the process proceeds to step S105. On the other hand, when the difference value is a value equal to or smaller than the threshold value ΔP ₀ (No in step S103), the determination unit 50 further determines whether or not the magnetic field strength P ₂ becomes a value larger than the predetermined threshold value P ₀ . A determination is made (step S104). When the magnetic field strength P ₂ is larger than the threshold value P ₀ (step S104, Yes), control is performed to display a predetermined warning on the warning display unit 51 (step S105). On the other hand, if the magnetic field strength P ₂ is the threshold value P ₀ the following values (step S104, No), it ends.

  The determination process in step S103 will be described. In the first embodiment, a noise magnetic field having position dependency is detected by the process in step S103. A general noise magnetic field is caused by, for example, a coil or the like provided in an electronic device or the like located outside the subject 1, and is usually in the same manner as the diffusion magnetic field described above. Unlike geomagnetism, etc., it is usually position dependent with respect to strength. Since the capsule endoscope 2 is located inside the subject 1 and the noise magnetic field sensor 13 is disposed on the outer surface of the subject 1, a predetermined distance is provided between the magnetic field sensor 16 and the noise magnetic field sensor 13. In the case of a noise magnetic field having position dependency, the value of the magnetic field strength detected in each is different.

Based on the above principle, in step S103, a difference value between the magnetic field intensity P ₂ detected by the noise magnetic field sensor 13 and the magnetic field intensity P ₁ detected by the magnetic field sensor 16 is derived, and the derived difference value and the threshold value ΔP _0. And to compare. By adopting such a configuration, unlike the geomagnetism, it is possible to accurately determine the presence or absence of a noise magnetic field having position dependency with respect to strength.

Next, the determination process in step S104 will be described. The purpose of step S104 is to detect a noise magnetic field that has no position dependency or poor position dependency. For example, when an electronic device or the like as a noise magnetic field forming source is located far from the subject 1, the magnetic field sensor is compared with the distance between the electronic device or the like and the magnetic field sensor 16 and the noise magnetic field sensor 13. The distance between 16 and the noise magnetic field sensor 13 is a negligible value. Therefore, even in the case where the noise magnetic field has position dependency, in such a case, the intensity of the magnetic field detected by the magnetic field sensor 16 and the intensity of the magnetic field detected by the noise magnetic field sensor 13 are almost the same value. . However, even such a noise magnetic field hinders accurate position detection, so it is desirable to detect it reliably. Therefore, in the first embodiment, in addition to the process of step S103, it is set to be performed: determining S104 whether the noise magnetic field on the basis of the absolute value of the magnetic field strength P ₂ in the noise magnetic field sensor 13.

  Next, advantages of the in-subject introduction system according to the first embodiment will be described. In the intra-subject introduction system according to the first embodiment, since the position detection device 3 includes the noise magnetic field sensor 13 and the determination unit 50, the presence or absence of the noise magnetic field can be determined based on the above-described mechanism. Is possible. Therefore, the in-subject introduction system according to the first embodiment has an advantage that it is possible to suppress a decrease in accuracy of position detection of the capsule endoscope 2 as a detection target.

Further, as described above, since the configuration using the geomagnetism as one of the position detection magnetic fields is employed in the first embodiment, it is necessary to avoid erroneous detection of the geomagnetism as a noise magnetic field. On the other hand, in the intra-subject introduction system according to the first embodiment, the presence / absence of a noise magnetic field is determined based on the difference value between the magnetic field intensity P ₂ and the magnetic field intensity P ₁ as shown in step S103 of FIG. By adopting such a configuration, there is an advantage that it is possible to prevent erroneous detection of geomagnetism as a noise magnetic field.

Specifically, geomagnetism has almost no position dependency with respect to strength, and has the property that the strength of geomagnetism becomes a substantially constant value at any position. Therefore, in step S103, it is possible to avoid detecting the geomagnetism as a noise magnetic field by setting the predetermined threshold ΔP ₀ to a predetermined value larger than 0.

From the viewpoint of avoiding erroneous detection of geomagnetism as a noise magnetic field, the threshold value P ₀ in step S104 is preferably set to a value higher than the intensity of geomagnetism. By adopting such a configuration, the in-subject introduction system according to the first embodiment can reliably detect a noise magnetic field that is poor in position dependency of magnetic field strength or does not have position dependency. At the same time, it is possible to avoid erroneously detecting the geomagnetism as a noise magnetic field.

  Furthermore, the intra-subject introduction system according to the first embodiment has a configuration including a warning display unit 51 that displays a predetermined warning according to the determination result of the determination unit 50. By providing the warning display unit 51, a user of the in-subject introduction system (that is, the subject 1) can recognize that the noise magnetic field is formed by the displayed warning, and the noise magnetic field It is possible to take measures such as moving to a place that can be ignored.

(Embodiment 2)
Next, the in-subject introduction system according to the second embodiment will be described. The in-subject introduction system according to the second embodiment uses a predetermined linear magnetic field as an alternative magnetic field for geomagnetism.

  FIG. 10 is a schematic diagram illustrating an overall configuration of the in-subject introduction system according to the second embodiment. As shown in FIG. 10, the in-subject introduction system according to the second embodiment has a capsule endoscope 2, a display device 4, and a portable recording medium 5 as in the first embodiment. The detection device 53 has a configuration different from that of the position detection device 3 in the first embodiment. Specifically, the position detecting device 53 has a configuration in which the geomagnetic sensor 9 is omitted and a first linear magnetic field forming unit 54, a second linear magnetic field forming unit 55, and a processing device 56 are provided. In the second embodiment, components having the same names and reference numerals as those in the first embodiment have the same structure and function as those in the first embodiment unless otherwise specified.

  The first linear magnetic field forming unit 54 is for forming a first linear magnetic field that is an alternative magnetic field of the geomagnetism in the first embodiment. Specifically, the first linear magnetic field forming unit 54 has a configuration including a coil formed so as to cover the body of the subject 1 as shown in FIG. 10, and a function of forming a magnetic field by the coil. Have Such a coil is arranged in a fixed state with respect to the subject 1, and more specifically, is arranged in a fixed state with respect to a reference coordinate axis.

  FIG. 11 is a schematic diagram showing an aspect of the first linear magnetic field formed by the first linear magnetic field forming unit 54. As shown in FIG. 11, the first linear magnetic field is configured to travel in the z-axis direction of the reference coordinate axis, and the first linear magnetic field functions as a position detection magnetic field instead of the geomagnetism.

  The second linear magnetic field forming unit 55 corresponds to the linear magnetic field forming unit 10 in the first embodiment. In the second embodiment, since the first linear magnetic field instead of the geomagnetism is formed as described above, the linear magnetic field in the first embodiment is used for the purpose of clarifying the distinction from the first linear magnetic field. This is referred to as a “second linear magnetic field”, and a configuration that forms the second linear magnetic field is referred to as a “second linear magnetic field forming unit 55”. Therefore, the second linear magnetic field forming unit 55 has substantially the same configuration and function as the linear magnetic field forming unit 10 in the first embodiment.

  Next, the processing device 56 will be described. FIG. 12 is a schematic block diagram illustrating the configuration of the processing device 56. As shown in FIG. 12, the processing device 56 omits the geomagnetic azimuth deriving unit 49 provided in the processing device 12 in the first embodiment in response to the fact that the geomagnetism is not used as the position detection magnetic field in the second embodiment. To do. In addition, the processing device 56 has a configuration that newly includes an orientation deriving unit 57 that derives an orientation in a manner different from the orientation deriving unit 40 in the first embodiment.

  In the second embodiment, the first linear magnetic field that functions as an alternative magnetic field for the geomagnetism is formed by the first linear magnetic field forming unit 54 as described above. Here, since the first linear magnetic field forming unit 54 is arranged in a fixed state with respect to the reference coordinate axis, the traveling direction of the first linear magnetic field is also fixed with respect to the reference coordinate axis. Using such characteristics, the azimuth deriving unit 57 grasps in advance the traveling direction of the first linear magnetic field (in the example of FIG. 11, the z-axis direction), and then first the target coordinate axis detected by the magnetic field sensor 16. The direction is derived based on the correspondence with the traveling direction of the linear magnetic field.

  It is important to determine the presence or absence of a noise magnetic field even in an in-subject introduction system having a configuration that does not use geomagnetism as a position detection magnetic field as in the second embodiment. The formation of the noise magnetic field makes it difficult to accurately detect the traveling directions of the first linear magnetic field and the second linear magnetic field when deriving the direction, and makes it difficult to accurately detect the magnetic field strength when deriving the position. As a result, the accuracy of azimuth derivation and position derivation decreases. Therefore, the intra-subject introduction system according to the second embodiment also has an advantage that accurate position detection can be performed by including the noise magnetic field sensor 13, the determination unit 50, and the like.

Also in the second embodiment, the threshold value P ₀ in step S104 shown in FIG. 9 is preferably a magnetic field strength higher than the magnetic field strength of geomagnetism. Although the geomagnetism is not used as the position detection magnetic field in the second embodiment, it is unavoidable that the geomagnetism exists in a normal environment. This is because the display can be avoided.

  Although the present invention has been described above in connection with the first and second embodiments, the present invention should not be construed as being limited to the first and second embodiments described above. It is possible to come up with examples. For example, in the first embodiment, the position detection device 3 has a configuration including the geomagnetic sensor 9 for the purpose of deriving the geomagnetic traveling direction separately from the noise magnetic field sensor 13. However, the reason why both are made independent components is from the viewpoint of facilitating understanding of the invention, and they may be configured integrally. For example, by adopting the same configuration as the magnetic field sensor 16 described above, it is possible to detect the magnetic field direction and the magnetic field strength, and therefore the position detection device 3 includes a single magnetic field sensor having such a configuration. It is also possible to enjoy the advantages of the present invention.

  Further, regarding the determination processing performed by the determination unit 50, it is possible to perform only one of the steps shown in FIG. 9 instead of necessarily performing both steps S103 and S104. That is, the processes in steps S103 and S104 are not effective only when performed as a series of processes, but each has the property of exhibiting the effect of detecting a noise magnetic field with a predetermined accuracy. .

1 is a schematic diagram illustrating an overall configuration of an in-subject introduction system according to a first embodiment. It is a typical block diagram which shows the structure of the capsule endoscope with which an in-subject introduction system is equipped. It is a schematic diagram which shows the aspect of the 2nd linear magnetic field formed by the 2nd linear magnetic field formation part while showing the structure of the 2nd linear magnetic field formation part with which a position detection apparatus is equipped, and a diffusion magnetic field formation part. It is a schematic diagram which shows the aspect of the diffusion magnetic field formed by the diffusion magnetic field formation part. It is a typical block diagram which shows the structure of the processing apparatus with which a position detection apparatus is equipped. It is a schematic diagram which shows the relationship between a reference | standard coordinate axis and an object coordinate axis. It is a schematic diagram which shows the utilization aspect of a 2nd linear magnetic field in the case of position derivation. It is a schematic diagram which shows the utilization aspect of the diffusion magnetic field in the case of position derivation. It is a flowchart for demonstrating the process of the determination part with which a processing apparatus is equipped. FIG. 3 is a schematic diagram illustrating an overall configuration of an in-subject introduction system according to a second embodiment. It is a schematic diagram which shows the aspect of the 1st linear magnetic field formed by the 1st linear magnetic field formation part with which the in-subject introduction system is equipped. It is a typical block diagram which shows the structure of the processing apparatus with which the in-subject introduction system is equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Capsule-type endoscope 3 Position detection apparatus 4 Display apparatus 5 Portable recording medium 7a-7d Reception antenna 8a-8d Transmission antenna 9 Geomagnetic sensor 10 Linear magnetic field formation part 11 Diffusion magnetic field formation part 12 Processing apparatus 13 Noise magnetic field Sensor 14 In-subject information acquisition unit 15 Signal processing unit 16 Magnetic field sensor 17 Amplification unit 18 A / D conversion unit 19 Wireless transmission unit 20 Switching unit 21 Timing generation unit 22 LED
23 LED drive circuit 24 CCD
Reference Signs List 25 CCD drive circuit 26 transmitting circuit 27 transmitting antenna 28 receiving antenna 29 power regeneration circuit 30 booster circuit 31 capacitor 32 coil 33 current source 34 coil 35 current source 37 receiving antenna selection unit 38 receiving circuit 39 signal processing unit 40 direction deriving unit 41 position Deriving unit 42 Magnetic field direction database 43 Recording unit 44 Oscillator 46 Amplifying circuit 47 Transmitting antenna selection unit 48 Selection control unit 49 Geomagnetic direction deriving unit 50 Judgment unit 51 Warning display unit 52 Curved surface 53 Position detection device 54 First linear magnetic field forming unit 55 Two linear magnetic field forming units 56 Processing device 57 Direction deriving unit

Claims (8)

A position detection device that detects a position of a detection target using a predetermined position detection magnetic field,
Magnetic field forming means for forming the position detecting magnetic field;
Position deriving means for deriving the position of the detection target based on the intensity of the magnetic field for position detection detected at the position where the detection target exists;
Magnetic field strength detecting means for detecting the magnetic field strength;
Determination means for determining whether a noise magnetic field is formed in a region where the detection target is located based on the intensity of the magnetic field detected by the magnetic field intensity detection means;
A position detection device comprising:   The determination unit is configured to detect noise when a difference value between a magnetic field strength detected by the magnetic field strength detection unit and a magnetic field strength detected in a region where the detection target is located exceeds a predetermined threshold. The position detection device according to claim 1, wherein it is determined that a magnetic field is formed.   The said determination means determines that the noise magnetic field is formed when the intensity | strength of the magnetic field detected by the said magnetic field strength detection means exceeds the predetermined threshold value. Position detector.   The position detection apparatus according to claim 3, wherein the threshold value is greater than the intensity of geomagnetism.   5. The position detection device according to claim 1, further comprising a warning unit configured to perform a predetermined warning when the determination unit determines that a noise magnetic field is formed. . The position detection magnetic field is formed by a first linear magnetic field having a predetermined traveling direction and a second linear magnetic field having a traveling direction different from the first linear magnetic field,
Correspondence relationship of the traveling direction of the first linear magnetic field on the target coordinate axis fixed with respect to the detection target and the reference coordinate axis which is different from the target coordinate axis, and the progress of the second linear magnetic field on the target coordinate axis 6. An azimuth deriving unit for deriving an azimuth formed by the target coordinate axis with respect to the reference coordinate axis based on a correspondence relationship between a direction and a traveling direction on the reference coordinate axis. The position detection device according to any one of the above. The first linear magnetic field is formed by geomagnetism,
A linear magnetic field forming means arranged at a predetermined position on the reference coordinate axis to form the second linear magnetic field;
Magnetic field sensor means for detecting a traveling direction of the geomagnetism in the reference coordinate axis;
Further comprising
The azimuth deriving means is detected by the detection target and the traveling direction of the geomagnetism on the reference coordinate axis, the traveling direction of the second linear magnetic field on the predetermined reference coordinate axis, detected by the magnetic field sensor means. The position detection apparatus according to claim 6, wherein the direction is derived based on a traveling direction of the geomagnetism on the target coordinate axis. An in-subject introduction device that is introduced into the subject and moves within the subject, and a position detection device that detects the position of the in-subject introduction device within the subject using a predetermined magnetic field for position detection An in-subject introduction system comprising:
The in-subject introduction device comprises:
A magnetic field sensor for detecting the position detection magnetic field in a region where the intra-subject introduction apparatus is located;
Wireless transmission means for transmitting a wireless signal including a detection result by the magnetic field sensor;
With
The position detection device includes:
Magnetic field forming means for forming the position detecting magnetic field;
Position deriving means for deriving the position of the in-subject introduction device based on the strength of the position detection magnetic field detected by the magnetic field sensor;
Magnetic field strength detecting means for detecting the magnetic field strength;
Determination means for determining whether a noise magnetic field is formed in a region where the detection target is located based on the intensity of the magnetic field detected by the magnetic field intensity detection means;
An in-subject introduction system characterized by comprising:

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