JP2021176413A - Position detector for capsule endoscope - Google Patents

Abstract

To detect a position of a capsule endoscope with accuracy.SOLUTION: A position detector 1 for a capsule endoscope includes an antenna 2 which receives electromagnetic waves transmitted by a capsule endoscope and a signal detecting part 3 which supports the antenna and includes a signal processing circuit for detecting the intensity of an output signal of the antenna. An opening shield 4 which covers the entire antenna, has a non-conductive window in the vicinity of the maximum point of the directivity of the antenna, and is made of a conductive member is provided. The window is circular or polygonal, and a diameter of the circle and a length of a diagonal line may be 0.01-0.04 times the wavelength of the electromagnetic wave.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a capsule endoscopy position detecting device that accurately detects the position of a capsule endoscope introduced into a subject's digestive organs by oral administration.

Gastrointestinal endoscopy is widely used for diagnosis of the gastrointestinal tract in the medical field. Examples thereof include oral endoscopes and nasal endoscopes. For example, oral and transnasal upper gastrointestinal endoscopy and colonoscopy enable detailed observation of the mucosal surface of the upper gastrointestinal tract and the large intestine, and endoscopic treatment of early cancer is also possible.

However, since these endoscopes are tube-shaped, they often cause pain and discomfort to the patient. In addition, since the small intestine is far from the mouth and anus and detours in a complicated manner, it is difficult to examine it using a normal upper gastrointestinal tract / colonoscope. Therefore, in recent years, a so-called capsule endoscope having a swallowable size has attracted attention (Non-Patent Document 1). Capsule endoscopy has the advantage that the gastrointestinal tract can be examined by a camera mounted inside, just by swallowing. Moreover, since it is a minimally invasive medical device and does not have the concept of effective length, it has the advantage of being able to examine the small intestine.

On the other hand, in capsule endoscopy, movement in the body depends on the internal peristaltic movement, and there is a concern that retention in the digestive tract and passage of lesions may occur. However, if the image captured by the capsule endoscope is always associated with the exact position of the capsule endoscope, the doctor can observe the passed lesion in real time by mapping processing or the like. You can check.

As a device for detecting the position of the capsule endoscope, for example, a device in which a plurality of sensors are attached to the body of the subject and the position of the capsule endoscope is specified based on the output of each sensor (Patent Document 1). A handy device (Patent Document 2 and Non-Patent Document 2) in which an operator such as a doctor or a medical engineer scans the abdomen of the subject with a sensor and estimates the point where the sensor strength is maximum as the position of the capsule endoscope (Patent Document 2 and Non-Patent Document 2). ). In each case, an electromagnetic wave carrying image data transmitted from a capsule endoscope is received by a loop antenna and its intensity is measured.

Japanese Unexamined Patent Publication No. 2005-052252 Japanese Unexamined Patent Publication No. 2007-325866

IKEDA Keiichi, SWAIN C.I. Paul, TAJIRI Hisao, "The Cut-ting Edge of Capsule Endoscopy Endoscopy and Innova-tions-Past, Present, and Future", Capsule Endoscope. 17, pp. 481-491,2005 Ryome Yuzawa, Yoshitake Masuda, Mitsuhide Sato, Tsutomu Mizuno, Shinhisa Tashiro, Naoki Omiya, "Examination of Real-Time Position Detector for Capsule Endoscopy", Institute of Electrical Engineers of Japan Materials, OQD-19-036, pp. 1-6, 2019

However, the electromagnetic wave transmitted from the capsule endoscope originally has directivity, and the directivity of the sensor (loop antenna) that receives it is not completely subject to rotation, so the reception strength of the loop antenna is maximum. There was a problem that the position of the capsule endoscope was deviated from the actual position of the capsule endoscope. In particular, in the case of a handy type device (Patent Document 2 and Non-Patent Document 2), the operator must always search for the point where the sensor strength is maximum, and the maximum detection strength due to the rotation of the capsule endoscope in the body or the like must be searched. Misalignment was an obstacle to accurate exploration.

The capsule endoscopy position detecting device according to one aspect of the present disclosure includes an antenna that receives an electromagnetic wave transmitted by the capsule endoscope, and a signal processing circuit that supports the antenna and detects the strength of the output signal of the antenna. A capsule endoscopy position detection device having a signal detection unit including It is a provided device.

The shape of the window is a circle or a polygon, and the diameter of the circle and the length of the diagonal line may be 0.01 to 0.04 times the wavelength of the electromagnetic wave.

The distance between the antenna and the window may be 0.04 to 0.08 times the wavelength of the electromagnetic wave.

The frequency of the electromagnetic wave may be 300 MHz to 600 MHz.

The antenna is a loop antenna having an outer diameter of 30 mm to 60 mm, the diameter or diagonal length of the window may be 10 mm to 20 mm, and the distance between the antenna and the window may be 30 mm to 60 mm.

According to one aspect of the present disclosure, a sharp directivity can be obtained in the near-field region of the electromagnetic wave radiated from the capsule endoscope, and as a result, a capsule endoscope position detection device having high position detection accuracy is realized. can.

It is a conceptual diagram which shows the basic structure and usage form of a capsule endoscope position detection device. It is a block diagram of the capsule endoscope of one Embodiment of this disclosure. It is a conceptual diagram which shows the operation of one Embodiment of this disclosure. It is a shape diagram and a peripheral circuit diagram of the antenna of one Example (Example 1) of this disclosure. It is a frequency characteristic diagram of the antenna of Example 1 of this disclosure. It is a block block diagram of the signal detection part of Example 1 of this disclosure. It is an external photograph of the prototype of Example 1 of this disclosure. It is an external photograph of the prototype of the comparative example. It is explanatory drawing of the evaluation experiment in Example 1 of this disclosure. It is explanatory drawing of the evaluation experiment in the comparative example. It is a reception intensity distribution map in a comparative example. It is a reception intensity distribution map in Example 1 of this disclosure. It is a perspective view of another Example (Example 2) of this disclosure. It is a perspective view of another Example (Example 3) of this disclosure. It is a front view of another Example (Example 4) of this disclosure.

Hereinafter, an embodiment according to one aspect of the present disclosure (hereinafter, the present embodiment) will be described in detail with reference to the drawings.

First, FIG. 1 shows a basic configuration and a usage pattern of a general (for example, Non-Patent Document 2) handy type capsule endoscope position detection device. The orally administered capsule endoscope (Capsule endoscopy) transmits electromagnetic waves to transmit the image captured in the digestive organs to the outside. For the frequency of electromagnetic waves, the UHF band is often used in consideration of the size of the antenna built in the capsule endoscope and absorption in the body. The position detector has a loop-shaped antenna (Antenna) and receives electromagnetic waves from the capsule endoscope. This electromagnetic wave is also used to detect the position of the capsule endoscope. For example, by changing the height of the speaker sound (Sound) according to the intensity of the received electromagnetic wave, the operator (doctor or the like) can determine the position of the capsule endoscope in real time.

FIG. 2 shows a configuration diagram of the capsule endoscope (1) of the present embodiment. In FIG. 2, reference numeral 2 denotes a loop-shaped antenna, which has a function of receiving electromagnetic waves of a capsule endoscope (not shown). The frequency of the electromagnetic wave is preferably 400 MHz to 600 MHz, which is a relatively low frequency region of the UHF band in consideration of the influence on the human body. The reception sensitivity of the antenna 2 is higher when the antenna 2 is as large as the wavelength, but considering that the antenna 2 is a handy type, the diameter is preferably 30 mm to 50 mm.

Reference numeral 3 denotes a signal detection unit, which includes a signal processing circuit that extracts a signal component from the electromagnetic wave received by the antenna 2 and detects the amplitude intensity thereof. Details of the signal processing circuit will be shown in Examples described later. In the present embodiment, the detected signal strength is converted into the pitch of the sound emitted by the speaker 32. Further, it may be converted into the emission intensity or wavelength of the LED 31.

Reference numeral 4 denotes an opening shield, which is provided so as to cover the antenna 2. The opening shield 4 is made of a conductive member. This conductive member may be made of a metal such as aluminum or copper. Further, it may be a conductive resin. Further, the resin surface may be plated with metal. The opening shield 4 is provided with a window 40. The position of the window is preferably near the maximum point of directivity of the antenna 2. In the case of a loop antenna, it is preferably located on its central axis.

The window 40 may be a simple opening (air) as long as it is non-conductive, or may be formed of a non-conductive resin. The shape may be circular or polygonal. Further, as shown in Example 4 described later, it may have a squeezing structure. At the time of position detection, the size of the window may be 0.01 to 0.04 times the wavelength of the electromagnetic wave in terms of diameter or diagonal dimension. Further, when the diameter of the loop antenna is 40 mm, the diameter is preferably 1 to 2 cm.

The shape of the opening shield may be a box shape, but may be a columnar shape or a truncated cone shape as shown in Examples 2 and 3 described later. However, the distance between the antenna 2 and the window 40 is preferably 0.04 to 0.08 times the wavelength of the electromagnetic wave. Higher directivity can be obtained at a distance, but on the other hand, the detection sensitivity decreases. It is preferable that the size of the antenna 2 is substantially the same. In the case of a loop antenna, when the diameter is 40 mm, the distance from the window 40 is preferably 30 mm to 60 mm, more preferably 40 mm to 50 mm.

FIG. 3 shows a conceptual diagram of the operation of receiving electromagnetic waves from the capsule endoscope. The capsule endoscope is assumed to be Medtronic's PillCam COLON2. The product has dimensions of φ11.6 mm x 31.5 mm and is equipped with LEDs for lighting and cameras for imaging at both ends. A one-turn loop antenna (Loop antenna) is mounted inside, and emits an electromagnetic wave consisting of an electric field and a magnetic field.

The capsule endoscope position detector in the present embodiment is located in the near-field region of this radiation source. The voltage v is generated when the antenna 2 receives the magnetic field of the electromagnetic waves that has passed through the window 40. Almost all electromagnetic waves emitted to other than the window 40 of the opening shield 4 are shielded. In other words, only electromagnetic waves "visible" from the antenna 2 through the window 40 reach the antenna 2. As a result, the capsule endoscope position detecting device provided with the aperture shield 4 has sharp directivity in the near-field region.

Hereinafter, examples of the present disclosure will be described. FIG. 4 shows a shape diagram (Fig. (A)) and a circuit diagram (Fig. (B)) of the antenna according to an embodiment (Example 1) of the present disclosure. In this embodiment, the antenna 2 is a single loop antenna having an outer diameter of 40.0 mm and an inner diameter of 36.0 mm. The line width is 2.0 mm and the thickness is 0.105 mm. A gap of 2.0 mm is provided at the output end.

In this embodiment, the frequency of the electromagnetic wave is 434.1 MHz. Its wavelength is 691 mm, and when trying to create an all-wavelength antenna, the element length becomes 691 mm. Since it is too large for an operator (doctor, etc.) to hold it in his hand to detect the position, a micro loop antenna as shown in FIG. 4 was adopted. However, since the small loop antenna has an impedance of an inductive reactance component, a resonance capacitor (Resonance capacitor) is inserted (Fig. (B)) so that the reactance component becomes zero at 434.1 MHz. A 0.42 pF ceramic capacitor was used as the resonance capacitor.

In addition, a matching circuit composed of LC is provided so that the received power can be transmitted to the subsequent circuit with maximum efficiency. The circuit constants (57 nH, 9.6 pF) were determined using a Smith chart so that the output impedance of the antenna 2 was 50 Ω. FIG. 5 shows a frequency characteristic diagram of the antenna 2 of this embodiment. A network analyzer (Agilent Technologies, E5061B) was used for the measurement. The output part of the matching circuit of FIG. 4 was connected to the test fixture, and the S parameter and impedance were measured using the reflection method. As shown in the figure, the impedance Z at 434.1 MHz was 50.7 Ω, and it was confirmed that it was approximately 50 Ω.

FIG. 6 shows a block configuration diagram of the signal detection unit 3 of this embodiment. The signal detection unit 3 has a signal processing circuit composed of the above-mentioned matching circuit (Matching circuit), ATA8204 (receiver IC), and the like, and a speaker 32 in the housing. In this embodiment, the received signal is first frequency-converted from f _{RF = 434.1 MHz to f IF = 1 MHz by the mixer inside the ATA8204.} The local oscillation frequency 433.1 MHz is obtained by multiplying the 13.534375 MHz crystal oscillation frequency by the PLL. Frequency reception signal to transform RSSI pin (Received Signal Strength Indication, received signal strength) of the IC are output from the _(V R), the voltage frequency conversion by VF converter after amplification offset removed by the differential amplifier circuit Is performed, and finally the pitch of the sound is converted by the speaker 32.

FIG. 7 shows a photograph of the appearance of the prototype capsule endoscope position detection device. The figure (a) shows the upper surface (operator side), and the figure (b) shows the lower surface (target person side). The actual dimensions are 196 mm in length, 60 mm in width, and 37 mm in height (not shown). The lower surface of the opening shield 4 has a square shape of 55 mm × 55 mm, and the diameter of the window 40 near the center is 16 mm. The material of the conductive member of the opening shield 4 is aluminum, and the window 40 is simply an opening (air). The antenna 2 is a loop antenna shown in FIG. 4A and has an outer diameter of 40 mm. The distance between the center of the loop antenna and the window 40 is 45 mm. The total mass of the capsule endoscope position detection device is 146 g, which a doctor can hold with one hand during medical treatment.

FIG. 8 is a photograph of the appearance and the inside of the capsule endoscope position detecting device of FIG. 7 excluding the opening shield 4. In this embodiment, the capsule endoscope position detecting device will be treated as a comparative example hereafter. Although the antenna is covered with a transparent bag in FIG. 8, it does not affect the characteristics described below.

FIG. 9 shows an explanatory diagram of the evaluation experiment of this example. In this embodiment, assuming that the capsule endoscope is inside the body, the characteristics of the position detector are evaluated by an experiment using a substance simulating human tissue, that is, a phantom. In this example, by dissolving sodium chloride and sugar in water according to the mass ratio shown in Table 1, a muscle tissue simulated substance having a dielectric constant and conductivity equivalent to that of muscle tissue was produced.

By placing the capsule endoscope in the manufactured phantom, the electromagnetic waves emitted by the capsule are attenuated in the same way as when the capsule is actually inside the body. Therefore, by evaluating the position detection accuracy in the situation where the electromagnetic wave is attenuated, it is possible to evaluate the characteristics assuming that the capsule endoscope is inside the body.

Here, the coordinates are set with the position of the capsule endoscope (Capsule endoscopy) fixed in the phantom as the origin (0,0). The direction of the capsule endoscope is assumed to be the case where the axial direction of the capsule is the y-axis (FIG. 9 (a)) and the case where the z-axis (FIG. 9 (b)). The case where the axial direction of the capsule is the x-axis direction is omitted because it is the same as the case of the y-axis direction in consideration of the symmetry of the antenna 2. The distance between the capsule endoscope and the capsule endoscope position detection device (lower surface of the opening shield 4) is 10 cm, which is the average abdominal radius of an adult, and the space is filled with a phantom.

The capsule endoscope position detection device (antenna 2, opening the shield 4) was measured using a the RSSI output voltage when the moving in the x and y directions _{V R} (see FIG. 6) Oscilloscope (Keysight, DSOS054A), The position detection accuracy was evaluated.

A similar evaluation experiment was performed for the comparative example (FIGS. 10 (a) and 10 (b)). However, since there is no opening shield 4, the antenna 2 is in direct contact with the phantom.

11 (a) and 11 (b) show RSSI output voltage distribution diagrams in the comparative example. Since the capsule position is the origin, if the output voltage is high only at the origin (0,0), highly accurate position detection is possible. However, no clear voltage difference can be seen from both figures. Further, since the voltage rises even in a region several tens of centimeters away from the origin, there is a possibility that a false capsule position may be determined. Further, when comparing FIGS. 11 (a) and 11 (b), no clear tendency is shown even if the direction of the capsule is changed. Therefore, the direction of the capsule cannot be determined either.

12 (a) and 12 (b) show RSSI output voltage distribution diagrams of the capsule endoscope position detection device of this embodiment. Similar to FIG. 11, the coordinates were set with the position of the capsule endoscope fixed in the phantom as the origin (0,0). The RSSI output voltage in this example was reduced as a whole as compared with the comparative example. This is because the amount of electromagnetic waves that can be received is limited by the attachment of the aperture shield 4, and the intensity of the received electromagnetic waves is reduced.

However, the directivity is improved, and from the figure (a), when the axial direction of the capsule is the y-axis direction, focusing on the voltage distribution near the origin (enlarged view on the right), the output voltage at the origin and (x, There is a clear voltage difference between the output voltages at y) = (0,5), (5,0), and (5,5). Further, from Table 2, the output voltage at the origin is a value four times or more the output voltage at (x, y) = (0,5), (5,0), (5,5). That is, since only the voltage at the origin, which is the capsule position, rises four times or more from the surroundings, even if it is estimated badly, the position detection with a misalignment error of 5 cm or less is possible by the signal processing circuit in the subsequent stage.

On the other hand, from FIG. 12B, when the axial direction of the capsule is the z-axis direction, the voltage is low in a wide range regardless of the position of the capsule endoscope position detecting device. This is because the loop antenna for electromagnetic wave transmission inside the capsule endoscope also has directivity, and it is difficult for electromagnetic waves to propagate in the axial direction of the capsule. However, if you wait for a while, the capsule endoscope will rotate inside the body, and the strength near the origin (0,0) will be restored. In other words, when the capsule endoscope rotates in the body, the point of maximum intensity (false position) does not move, but in this embodiment, the strength near the origin (0,0) only changes. Further, in such a case, the position on the side surface can be specified by rotating the capsule endoscope position detection device along the body and wrapping around from the front side to the side surface.

(Example 2)
Hereinafter, other examples of the present disclosure will be described. FIG. 13 is a perspective view of another embodiment (Example 2) of the present disclosure. The figure shows only the opening shield 4 and the window 40, which are the characteristic parts of this embodiment. As shown in the figure, the opening shield 4 has a cylindrical shape, and a window 40 is provided near the center of the lower surface (target side) of the opening shield 4.

(Example 3)
FIG. 14 is a perspective view of another embodiment (Example 3) of the present disclosure. The figure shows only the opening shield 4 and the window 40, which are the characteristic parts of this embodiment. As shown in the figure, the opening shield 4 has a truncated cone shape, and a window 40 is provided near the center of the lower surface (target side) thereof.

(Example 4)
FIG. 15 is a perspective view of another embodiment (Example 4) of the present disclosure. The figure shows only the opening shield 4 and the window 40, which are the characteristic parts of this embodiment. As shown in the figure, the window 40 is realized by a conductive throttle provided on the opening shield 4. The electromagnetic waves radiated from the endoscope capsule include image information taken by the camera, and the received SNR deteriorates if the opening shield 4 is provided as described above. Therefore, the aperture may be narrowed when the position is detected, and the aperture may be opened when the image information is received.

1 Capsule endoscopy position detector 2 Antenna 3 Signal detector 4 Aperture shield 40 Window

Claims (5)

It is a capsule endoscopy position detection device having an antenna for receiving electromagnetic waves transmitted by the capsule endoscope and a signal detection unit that supports the antenna and includes a signal processing circuit for detecting the strength of the output signal of the antenna. hand,
A capsule endoscope position detection device that covers the entire antenna and is provided with an opening shield made of a conductive member having a non-conductive window near the maximum point of directivity of the antenna. The first aspect of claim 1, wherein the shape of the window is a circle or a polygon, and the diameter of the circle and the length of the diagonal line are 0.01 to 0.04 times the wavelength of the electromagnetic wave. Capsule endoscopy position detector. The capsule endoscope position detecting apparatus according to any one of claims 1 or 2, wherein the distance between the antenna and the window is 0.04 to 0.08 times the wavelength of the electromagnetic wave. .. The capsule endoscope position detecting device according to any one of claims 1 to 3, wherein the frequency of the electromagnetic wave is 300 MHz to 600 MHz. The antenna is a loop antenna having an outer diameter of 30 mm to 60 mm, the diameter or diagonal length of the window is 10 mm to 20 mm, and the distance between the antenna and the window is 30 mm to 60 mm. Item 4. The capsule endoscopy position detecting device according to Item 4.

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