JP2012034890A - System for detecting lc resonance magnetic marker fixed to annular hollow body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for detecting an LC resonance magnetic marker fixed to an annular hollow body.SOLUTION: The system includes: an exciting coil 1; a plurality of detecting coils 2 facing the exciting coil; the LC resonance magnetic marker 6 disposed between the exciting coil and the detection coils; and the annular hollow body 16 to which the LC resonance magnetic marker is fixed, the exciting coil generating an alternating magnetic field synchronized with the resonance frequency of the LC resonance magnetic marker. The system further includes a measuring means which measures the induction magnetic field from the LC resonance magnetic marker by each detection coil of the plurality of detection coils; and a means which determines a contribution voltage of the LC resonance magnetic marker.

Description

  The present invention relates to a position detection system for an LC resonance type magnetic marker fixed inside an annular hollow body such as an in-vivo insertion tube, and to a position detection system for an LC resonance type magnetic marker and a tube to which the marker is fixed. is there.

  In the case where the position of a part inside the living body or the surface of the living body is accurately measured by a magnetic method, it is desirable that the marker attached to the measurement part does not have an electrical lead wire or a battery. So far, as a method suitable for detecting the position of an optically shielded space, a method for detecting the position of a permanent magnet or a magnetized magnetic material has been developed (the following Non-Patent Documents 1-5). However, since these measure a DC magnetic field, they are susceptible to the effects of geomagnetism and low-frequency noise.

On the other hand, Massachusetts Institute of Technology reports a marker position detection system using an LC resonance circuit (Non-Patent Document 6 below). However, this is to roughly measure the position of the magnetic marker using one coil, and the position accuracy has not been discussed, and it is not a precise position detection system on the order of mm. Moreover, it is difficult to measure the five degrees of freedom of the marker position and direction. Also, a position detection method using an active IC tag with a built-in battery has been proposed (Non-Patent Document 7 below), but there are problems such as restrictions on dimensions and operating time and time stability of measurement due to the built-in battery. is there.

  The inventors of the present application aimed to achieve both the necessity of an electrical lead wire to the magnetic marker and the difficulty of being affected by external noise, and a position detection system using a marker by an LC resonance circuit. Proposed. By measuring the amplitude of the induced voltage of the marker, it was shown that the position of the marker can be detected with a positional accuracy of about 2 mm using a magnetic marker having a diameter of 5 mm and a length of 10 mm (Non-patent Document 8 below). .

On the other hand, in the medical field, insertion of a tube into a living body is routinely performed in various hospitals, and prevention of the erroneous insertion is extremely important for safety measures, but the position of the tube at the time of insertion is simply and accurately. Means to grasp are not well established. In particular, with the increase in elderly hospitalized patients in recent years, the risk of medical accidents due to misinsertion into the respiratory tract, such as nasal tube feeding tubes, is said to increase, and the erroneous insertion rate of tube feeding tubes is about 2%. There is also a report (the following nonpatent literature 9). In addition, according to a report from the Japan Medical Function Evaluation Organization, about 30,000 cases (about 15% of all cases) were reported as “near and hat cases” when handling tubes in Japan in 2007. It can be inferred that the number of medical accidents such as in the past and the number of cases in the previous stage are enormous. However, in the clinical field, the sound of bubbles due to air injection is still confirmed with a stethoscope, the insertion of the tube is confirmed by pre-modern methods such as collecting gastric juice, and the tube position is confirmed while receiving radiation exposure by X-rays. . These current conditions are insufficient and dangerous from the viewpoint of preventing medical accidents in elderly hospitalized patients, and accurate and simple confirmation at the time of tube insertion is an urgent issue to ensure patient safety. .

There has been a reported method for detecting the position of an in-vivo insert by measuring a DC magnetic field generated from a permanent magnet and determining the position of the permanent magnet (Patent Document 2). However, since this method uses a DC magnetic field as a measurement medium, there is a problem in hospitals and the like that position accuracy deteriorates due to elevators, door opening / closing, bed movement, low-frequency magnetic noise, and the like. In addition, a method has been reported in which a magnetic field sensor is inserted into the tube, an alternating magnetic field is generated from a coil placed outside the body, and the sensor position is roughly detected (Non-Patent Document 10). However, since this method passes thin wires through the inside of the tube, the problem is that the tube operation is hindered and the accuracy deteriorates due to the application of radioactive noise to the thin wires.

JP 2005-121573 A Special Table 2002-529133

F. Grant, G.G. West, Interpretation Theory in Applied Geophysics. New York: McGraw-Hill, 1965, pp. 306-381. S. V. Marshall, Vehicle Detection Using a Magnetic Field Sensor, IEEE Trans. Vehicular Technology, vol. VT-27, pp. 65-68, (1978). W. M.M. Wynu, C.I. P. Frahm, P.A. J. et al. Carroll, R.A. H. Clark, J. et al. Wellhoner, M .; J. et al. Wynn, Advanced Supercomputing Gradiometer / Magnetometer Arrays and A Novel Signal Processing Technique, IEEE Trans. Magn. vol. MAG-11, pp. 701-707, (1974). J. et al. E. McFee, Y.M. Das, Determination of the Parameters of a Dipole by Measurement of it's Magnetic Field, IEEE Trans. Antennas and Propagation, vol. AP-29, pp. 282-287, (1981). S. Yabukami, K .; Arai, H .; Kanetaka, S .; Tsuji, and K.K. I. Arai, Journal of the Magnetics Society of Japan, vol. 28, pp. 711-717, (2004). J. et al. A. Paradiso, K .; Hsiao, J. et al. Stricken, J .; Lifton, A.M. Adler, IBM Systems Journal, vol. 39, no. 3 & 4, pp. 892-914, (2000). S. Watanabe, S.M. Nishiyama, N .; Koshizuka, and K.K. Sakamura, MWE 2003 Microwave Workshop, pp. 245-250, (2003). S. Yabukami, S .; Hashi, Y .; Tokunaga, T .; Kohno, K .; I. Arai, and Y.A. Okazaki, Journal of the Magnetics Society of Japan, vol. 28, pp. 877-885, (2004). (A.J.Rassias et al, Critical Care vol. 2 (1), pp. 25-28 (1998).) http://www.viasyshealthcare.com/default.aspx

The purpose of this patent is to easily detect erroneous insertion detection of a living body insertion tube which is highly urgent for safety measures. A system that can measure the position and direction of the magnetic marker attached to the tube tip in real time will be developed so that erroneous insertion of the tube tip can be detected inside the living body. By using the proposed system, we show that there is no radiation exposure without hindering the insertion of the tube, and it is possible to grasp the erroneous insertion of the tube easily and accurately.

In order to achieve the above object, the present invention provides
(1) An excitation coil, a plurality of detection coils opposed to the excitation coil, an LC resonance type magnetic marker disposed between the excitation coil and the detection coil, and an annular shape in which the LC resonance type magnetic marker is fixed The hollow body and the excitation coil generate an alternating magnetic field tuned to the resonance frequency of the LC resonance type magnetic marker, and the induction magnetic field from the LC resonance type magnetic marker is measured by each detection coil of the plurality of detection coils. The detection system of the LC resonance type magnetic marker fixed to the annular hollow body is characterized by comprising measurement means and means for obtaining the contribution voltage of the LC resonance type magnetic marker.

(2) The LC resonance type magnetic marker is detected using the LC resonance type magnetic marker detection system in which the position or posture angle of the LC resonance type magnetic marker or both the position and posture angle are detected. Of course, when the position and posture angle of the LC resonance type magnetic marker are detected, the position and posture angle of an annular hollow body such as a tube which is fixed to the LC resonance type magnetic marker can be detected. Moreover, since the positional relationship between the tip of the annular hollow body and the fixed LC resonance type magnetic marker can be fixed, the position of the tip of the annular hollow body can also be measured.

(3) The LC resonance type magnetic marker is an LC resonance type magnetic marker detection system comprising a magnetic material, a marker coil wound around the magnetic material, and a capacitor.

(4) The marker coil detects an LC resonance type magnetic marker in which the angle formed by the rotation axis direction of the marker coil, the rotation axis direction of the excitation coil, and the rotation axis direction of the detection coil is any angle between 0 degrees and 60 degrees. The system.

(5) The annular hollow body was used as a detection system for an LC resonance type magnetic marker which is a medical tube for living body insertion.

(6) The annular hollow body is an LC resonant magnetic marker detection system that fixes the LC resonant magnetic marker inside the annular hollow body.

According to the present invention, the following effects can be achieved.
Since the marker is wireless and battery-free, the insertion of the tube is not hindered, and since an AC magnetic field is used, it is not easily affected by low-frequency magnetic noise. Magnetic noise such as opening / closing of doors, elevators, movement of metal objects, etc. Even in many hospitals, erroneous tube insertion can be prevented easily and reliably. Multiple markers are also easy. In addition, there is no radiation exposure, and there is little burden on patients and safety is high.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Hereinafter, embodiments of the present invention will be described in detail.
In this system, an alternating magnetic field having a resonance frequency of the LC resonance type magnetic marker 6 is excited by the excitation coil 1, and thereby the value of the induced magnetic field 5 generated from the LC resonance type magnetic marker 6 is measured using the detection coil 2. The position and direction of the LC resonance type magnetic marker 6 are optimized from the change of the magnetic field depending on the presence or absence of the LC resonance type magnetic marker 6. FIG. 1 shows the configuration of the position detection system. Measurement system is excitation coil 1 and detection coil 2
(40 channels), LC resonance type magnetic marker 6, AD and DA converter (NI PXI-6251: 1 unit), DA converter (NI PXI-6250: 9 units), control unit
(NI PXI-8187) and amplifier 7 (SR560). The control program was created using Lab VIEW ver.7.1, and the optimization program was created using Visual C ++. The AD converter 9 PXI-6251 and PXI-6250 are used in a mode that measures 4 channels of 16-bit signals per unit at a sampling rate of 250 ksample / sec, and acquires the induced voltage of the 40-channel detection coil 2 in parallel. I was able to do it. As for the voltage to the exciting coil 1, the output signal from the PXI-6251 was connected to the exciting coil 1 via the amplifier 7. The optimization process of the position and direction of the LC resonance type magnetic marker 6 is performed by another personal computer 8 connected to Ethernet (registered trademark).
Calculation was performed with (Pentuim (R) D, 3.20 GHz), and the position of the LC resonance type magnetic marker 6 was displayed on the screen.

FIG. 2 shows an assumed arrangement of the excitation coil 1, the detection coil 2, and the LC resonance type magnetic marker 6. As shown in FIG. It is assumed that the position of the tip of the tube 10 is detected by inserting the annular hollow body 16 or the tube 10 attached with the LC resonance type magnetic marker 6 with a person lying between the coils. FIG. 3 shows a drawing of the produced LC resonance type magnetic marker 6. The LC resonance type magnetic marker 6 was formed into an elongated type by winding a copper wire in the longitudinal direction of a rectangular ferrite, assuming the above-described restrictions on the arrangement of the system for increasing the signal strength and insertion at the tip of the tube 10. The LC resonance type magnetic marker 6 is a 4700 pF chip capacitor 13 (C Series made by TDK Corporation) on a coil made by winding 150 mm of 0.1 mm diameter copper wire around MnZn ferrite 12 (PC40 made by TDK Corporation) of 2 mm x 2 mm x 30 mm. ) Are connected in series with solder to form an LC resonance type magnetic marker 6 and the resonance frequency is designed to be 82.5 kHz. The outer diameter was 3mm x 4mm x 33mm, the inductance was 0.748mH, and the figure of merit was about 9.0. The exciting coil 1 is a rectangle of 140 mm × 200 mm, and a copper wire having a diameter of 1.0 mm is subjected to 23 turns. The detection coil 2 was made of a 0.2 mm diameter copper wire with a diameter of 23 mm and 125 turns, and 40 pieces were arranged on the same plane at 30 mm intervals. The surfaces of the excitation coil 1 and the detection coil 2 were opposed to each other at a distance of about 300 mm. Since this system performs measurement in one axis, the magnetic flux penetrating the coil is increased and the signal strength is increased by making the perpendicular direction of the excitation coil 1 and the detection coil 2 and the magnetic field generation direction of the LC resonance type magnetic marker 6 substantially in a straight line. . On the other hand, in this case, there is a concern that the induced magnetic field 5 from the LC resonance type magnetic marker 6 increases in error with respect to the dipole magnetic field, but the positions of the esophagus 14 and the trachea 15 are roughly determined by simple measurement of only one axis component. Adopted from the viewpoint of distinguishing. A human body model (3430 Scientific W43020) is placed between the excitation coil 1 and the detection coil 2, and an alternating magnetic field tuned to the resonance frequency of the LC resonance type magnetic marker 6 is generated. As shown in FIG. An annular hollow body 16 or tube 10 (Fuji Systems' Margensonde S, E-10, outer diameter 6 mm, inner diameter 4 mm) with a resonance type magnetic marker 6 attached to the tip is inserted into the human body model as shown in FIG. The position of the tip of the annular hollow body 16 or the tube 10 was optimized.

FIG. 6 shows a flowchart for obtaining the position and direction of the LC resonance type magnetic marker 6. First, in the state where the LC resonance type magnetic marker 6 is removed, the induced voltage of the arranged detection coil 2 is measured and set as the background voltage. Next, the tube 10 with the LC resonance type magnetic marker 6 attached to the tip is placed inside the human body model, and the induced voltage of the detection coil 2 is measured. A vector-like difference is obtained from the amplitude and phase difference of these voltages, and this is used as the contribution voltage of the LC resonance type magnetic marker 6. The position and direction of the LC resonance type magnetic marker 6 are optimized by the Gauss-Newton method according to the following three equations, assuming that the induced magnetic field 5 generated from the LC resonance type magnetic marker 6 can be approximated to a dipole magnetic field.

However, S is an evaluation value and p is a parameter vector. i is the number of the detection coil 2 (1 to 40)
, B ⁽ⁱ⁾ _c (p) is a theoretical value of magnetic flux density in consideration of the dipole magnetic field, r is a position vector from the LC resonance type magnetic marker 6 to the detection coil 2i, and M is a magnetic moment of the LC resonance type magnetic marker 6. , (X, y, z) are the coordinates of the LC resonant magnetic marker 6i, θ is the angle formed by the moment direction vector projected on the xy plane and the x axis, and φ is the angle formed by the moment direction vector and the z axis. . The initial value of the Gauss-Newton method is the convergence value from the previous step. The reduction factor α in the Gauss-Newton method was about 0.01.

FIG. 7 is a drawing of the excitation coil 1, the detection coil 2, and the LC resonance type magnetic marker 6. The tip of the tube 10 to which the LC resonance type magnetic marker 6 is attached is a micrometer.
It is fixed on the acrylic stick attached to (LIG-16100 made by SIGMA KOKI), and the initial value with the center of the detection coil 2 as the origin
Moved + 100mm in the x direction from (-50,1,150).

FIG. 8 shows the position detection result of the locus of the LC resonance type magnetic marker 6 at the time of parallel movement. FIG.
Shows the projection onto the XZ plane, and FIG. 9 shows the projection onto the XZ plane. The detected trajectory substantially follows the actual moving distance and trajectory. The relative position accuracy was about 7.1 mm at the center position of the exciting coil 1 and the detecting coil 2 considered to have the strictest detection conditions.

FIG. 10 shows the center position of the LC resonance type magnetic marker 6 when the tip of the tube 10 attached with the LC resonance type magnetic marker 6 is inserted into the trachea 15 and the esophagus 14 from the vicinity of the pharynx of the human body model and moved about 100 mm. Are compared with the human body model esophagus 14 and trachea 15. The initial placement of the stroke in the trachea 15 is (-95,1,85), the final placement is (25,1,110), and the initial placement of the stroke in the esophagus 14 is
(-90,1,90) and final placement is (15,1,120). Both the esophagus 14 and the trachea 15 have obtained a result of following the actual trajectory of the curve, and position accuracy is obtained that can determine whether the distal end position of the tube 10 is in the trachea 15 or the esophagus 14. Conceivable. As a result, the tube 10 inserted into the stomach is expected to be prevented from being accidentally inserted into the trachea 15.

In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

The position and direction detection system of the high-accuracy LC resonant magnetic marker 6 of the present invention can be used as a position detection system based on real-time operation using phase information.

3 is a connection diagram of a position detection system using an LC resonance type magnetic marker 6. FIG. Example 1 2 is a configuration diagram of a detection system for an LC resonance type magnetic marker 6 fixed in a tube 10. FIG. Example 1 This is an LC resonance type magnetic marker 6 composed of MnZn ferrite 12, a coil, and a chip capacitor 13. Example 1 This is an LC magnetic type magnetic marker 6 fixed to a commercially available tube 10. Example 1 It is a mode that the tube 10 to which the LC resonance type magnetic marker 6 is fixed is inserted into the human body model. Example 1 It is a flowchart which measures the position and direction of the front-end | tip of a tube 10, and a magnetic marker. Example 1 It is a state that the tube 10 is precisely moved by a micrometer. Example 1 It is a locus in the XZ plane when the LC resonance type magnetic marker 6 is moved 100 mm. Example 1 It is a locus in the XY plane when the LC resonance type magnetic marker 6 is moved 100 mm. Example 1 It is the locus | trajectory of the front-end | tip position of the tube 10 inside a human body model. Example 1

DESCRIPTION OF SYMBOLS 1 Excitation coil 2 Detection coil 3 Controller 4 Applied magnetic field 5 Inductive magnetic field 6 LC resonance type magnetic marker 7 Amplifier 8 Personal computer 9 AD converter 10 Tube 11 Marker coil 12 MnZn ferrite 13 Chip capacitor 14 Esophagus 15 Trachea 16 Annular hollow body 17 In the esophagus Trace of LC resonant magnetic marker 18 Trace of LC resonant magnetic marker in trachea

Claims (6)

An exciting coil;
A plurality of detection coils opposed to the excitation coil;
An LC resonance type magnetic marker disposed between the excitation coil and the detection coil;
An annular hollow body to which the LC resonance type magnetic marker is fixed,
The excitation coil generates an alternating magnetic field tuned to the resonance frequency of the LC resonance type magnetic marker, and measures an induction magnetic field from the LC resonance type magnetic marker with each detection coil of the plurality of detection coils. Means,
A detection system for the LC resonance type magnetic marker fixed to an annular hollow body, comprising means for obtaining a contribution voltage of the LC resonance type magnetic marker. The LC resonance type magnetic marker detection system according to claim 1, wherein the detection of the LC resonance type magnetic marker is performed by using the position or posture angle of the LC resonance type magnetic marker or both the position and the posture angle. 3. The LC resonance type magnetic marker detection system according to claim 1, wherein the LC resonance type magnetic marker includes a magnetic material, a marker coil wound around the magnetic material, and a capacitor.   4. The LC resonance type magnetic according to claim 3, wherein the marker coil has an angle between 0 ° to 60 ° formed by the rotation axis direction of the marker coil, the rotation axis direction of the excitation coil, and the rotation axis direction of the detection coil. Marker detection system.   The detection system for an LC resonance type magnetic marker according to any one of claims 1 to 4, wherein the annular hollow body is a medical tube for insertion into a living body. The detection system for an LC resonance type magnetic marker according to any one of claims 1 to 5, wherein the annular hollow body fixes an LC resonance type magnetic marker inside the annular hollow body.