JP4699623B2 - Method and apparatus for measuring physical variables in vivo - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a guide wire assembly for intravascular examination.
[0002]
[Prior art]
It is known to mount a sensor on a guide wire and place the sensor in a blood vessel in the living body via the guide wire to detect a physical parameter such as pressure or temperature. The sensor comprises elements that are directly or indirectly sensitive to the parameters. For example, the temperature can be measured by observing the resistance of a conductor having a temperature sensitive resistance or by observing the length of an element having a known temperature related elongation.
[0003]
In order to monitor the state of the sensor in the body, some kind of communication means is required. In some cases, a means for supplying power to the sensor and / or communication means is also required. Thus, in order to power the sensor and to communicate with the sensor, a plurality of cables transmitting measurement signals are connected to the sensor, the cables being routed from the blood vessel to the external monitoring unit via the connector assembly. Guided along. Further, the guide wire is typically provided with a central metal wire (core wire) that functions as a sensor support and a ground potential conductor.
[0004]
However, when multiple cables are used, the core wire must be at least partially replaced with a tubular section that houses the cable. This section forms a fragile part of the guidewire and presents dangers such as bending or asymmetric movement during manipulation in the blood vessel. Also, the conventional guide wire assembly presents a problem in that it requires a very difficult manual assembly procedure. Extremely small components must be assembled under a microscope, which is tedious, tedious and labor intensive.
[0005]
An improved guidewire that addresses this problem is described in European Patent Application No. 0925803, which forms the basis of the preamble of the independent claims of this application. European Patent Application No. 0925803 describes a guide wire that simplifies the manufacturing process by placing a generally tubular conductor coaxially about a core wire. However, the manufacture of such guidewires is still relatively time consuming and expensive and requires complex connectors. There also remains a need for a guidewire with a sensor that is easy to operate.
[0006]
[Problems to be solved by the invention]
Accordingly, there is a continuing need for a wire communication system that is easy to operate, inexpensive, and easy to use, and there remains a need for a simplified guidewire assembly with physical property sensors.
[0007]
[Means for Solving the Problems]
It is an object of the present invention to provide a system for examining in vivo physiological variables in blood vessels with a guidewire that is easy to manufacture and operate. This object is achieved with the system according to claim 1 and the guidewire according to claim 7.
[0008]
According to the present invention, the number of electrical conductors of a guide wire provided with a sensor for measuring physiological variables in a living body can be reduced, thereby providing a guide wire that is easy to manufacture and use. A physiological variable measurement method using a guidewire and system according to the invention is also provided according to claim 11.
[0009]
Further scope of the applicability of the present invention will become apparent from the detailed description given below. However, the detailed description and specific examples are given for the purpose of illustration only, while illustrating preferred embodiments of the present invention. From this detailed description, various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. The present invention will be more fully understood from the detailed description, including the accompanying drawings, given by way of example only and not limiting the present invention.
[0010]
First, the guide wire according to the present invention will be described. In general, according to the present invention, a sensor that requires electrical energy for operation is connected to the far end of an insulated wire. In addition, the body electrode is directly connected to the sensor or connected to the sensor via an electronic circuit connected to the sensor. The body electrode is arranged in contact with a living tissue such as blood when inserted into the body. That is, the body electrode includes a portion for directly contacting body tissue when inserted into a patient.
[0011]
In use, the sensor is inserted into the living body with the proximal end of the wire connected to the power source, and the sensor and the body electrode are placed at a site in the body where the measurement is performed. Therefore, the body electrode is disposed in contact with a living body, specifically in contact with a body tissue such as blood, and obtains electrical connection with the body tissue. In order to obtain a closed electrical circuit, the second electrode is connected to a power source and carried near the body electrode. The second electrode comprises a portion that is physically and electrically connected to the patient directly or via a conductive enhancement medium, as is well known in the art.
[0012]
In one embodiment of the invention, this is done by placing the electrode on the patient's skin outside the measurement site, similar to the application of ECG electrodes. In this embodiment, the electrical circuit is closed through the patient's internal tissue and skin. In another embodiment of the invention, the electrical circuit is closed by inserting the second electrode so that the distal end of the second electrode is located near the measurement site and contacts the patient's body tissue. It is done. In this embodiment, the electrical circuit is closed internally through the patient's tissue, typically blood.
[0013]
Sensors and electrodes can be inserted into any suitable site in the body via a hollow tube such as a suitable cannula or introducer. In a preferred embodiment, the sensor, additional electronic circuitry, body electrode, electrical wire, and second electrode are mounted on a guidewire structure and are typically inserted through the femoral artery.
[0014]
In the most preferred embodiment, the electrical wire is integrated with the core wire of the guide wire. The advantage of reducing the number of components can be obtained by using the core wire as the electric wire. This is because such a metal core wire that normally extends axially along the guide wire is present in the guide wire in order to give the guide wire adequate rigidity. Thus, although the present specification describes for simplicity the use of a guidewire having a core wire as an electrical wire, the method for communicating with the sensors described herein can run along or guide the guidewire. Obviously, it may be implemented using a separate wire separated from the wire.
[0015]
The power source used in the present invention is an electronic unit installed outside the patient's body. The electrical unit can provide the appropriate current through an electrical circuit that partially includes the patient's body, as described below. Furthermore, as will be described later, the electronic unit is preferably provided with an electronic circuit for interpreting and presenting an output signal from the sensor circuit.
[0016]
Next, one embodiment of the guide wire of the present invention will be described with reference to FIG. FIG. 1 shows a cross-section at the distal end of a guidewire 10 according to the present invention. Typically, a core 11 of superelastic alloy such as stainless steel or Nitinol® extends through the central axis of the guide wire. The core wire 11 is coated with an insulating layer 12 which is a polymer such as Parylene (registered trademark), silicon, Teflon (registered trademark), polyimide, polyurethane, or ceramic coating.
[0017]
Proximal coil section 13A and distal coil section 13B cover the distal end of the core wire. Proximal coil section 13A functions to provide a smooth surface and adequate stiffness at the end of the guidewire and is typically made of stainless steel. The distal coil section 13B is similar to the proximal section except that it also provides x-ray opacity and is typically manufactured from platinum. The coils are combined to serve to provide a uniform outer diameter for the guide and facilitate introduction of the guide wire into the artery. When inserted into the artery, the coil can penetrate the blood surrounding the end of the guidewire. The tip of the guide wire is closed by a soldered arcuate tip 16.
[0018]
The configuration of the coil section is described to show the shape of the distal end of a typical guide wire currently in use. However, the coil section is not necessary per se for the implementation of the present specification, but can be used as part of one embodiment of the present invention, as will be described later.
[0019]
The sensor 14 is attached to the core wire and is electrically connected to the core wire via the connection point 15. The sensor comprises components sensitive to the physical characteristics to be determined, as well as any electronic circuitry necessary to function properly and usefully as a sensor, and circuitry for superimposing the sensor output signal on the carrier voltage signal . Circuits for such superposition are known per se to those skilled in the art and include devices such as voltage / frequency converters, analog / digital converters, pulse width modulators and delta modulators.
[0020]
An example of one embodiment of a sensor having a related circuit is shown in FIG. Here, a rectifier 501, a sensor element 502, and a relaxation oscillator 503 are shown connected in series. The input of the rectifier 501 is connected to the core wire of the guide wire via the connection point 504. The output of relaxation oscillator 503 is connected to the body electrode via connection point 505. The rectifier 501 and the sensor element 502 are connected to the body electrode. Relaxation oscillator 503 generates a square wave as opposed to a sine wave oscillator. That is, the output signal shifts from the minimum level (digital “zero”) to the maximum level (digital “1”). The oscillation period or pulse width of such an oscillator, also known as “astable multivibrator” in the literature, is usually due to one or several characteristic time constants RC, where R is the resistance value and C is the capacitance value. It can be controlled with a characterized resistance-capacitance circuit. Therefore, the period or pulse width of the oscillator can be controlled using a resistance sensor or a capacitance sensor.
[0021]
Referring to FIG. 1 again, the output signal from the sensor 14 is transmitted to the surrounding blood via the signal output electrode 17. The signal output electrode 17 is not at least partially insulated, and is connected to the sensor 14 at one end to transmit the output from the sensor circuit, and the other end is the periphery between one of the coil sections 13A, 13B. Extends into the blood. Since the core wire is insulated, the electrode 17 does not receive interference due to the potential of the core wire.
[0022]
FIG. 2 shows an alternative embodiment 117 of the signal output electrode, in which components different from those in FIG. 1 are provided with reference numerals. According to FIG. 2, the signal output electrode 117 is connected to or forms part of one coil section 113B. During the period in which one of the coil sections is useful, at least a portion of the selected section should not be insulated so that contact with surrounding body fluid is possible. With this alternative embodiment, a simple design is obtained that ensures proper contact with the surrounding body part.
[0023]
The use of a guidewire 10 according to the present invention, such as the guidewire shown in FIG. 1, is schematically illustrated in FIG. The guide wire 10 is inserted into the femoral artery of the patient 25. The positions of the guide wire 10, the sensor 14, and the signal output electrode 17 in the body are indicated by dotted lines.
[0024]
An external electrode 21 similar to the ECG electrode is attached to the skin of the patient 25 near the position of the sensor circuit 14. The external electrode 21 is connected to the electronic unit 22 via the electric wire 24. The guide wire 10, more specifically its core wire 11, is a cable 26 connected to the core wire using any suitable connector means (not shown), such as an alligator type connector or any other known connector. To the electronic unit 22.
[0025]
The electronic unit 22 provides voltage to a circuit that includes a wire 26, a core wire 11 of the guidewire 10, a sensor circuit 14, a signal output electrode 17, a patient's blood or other tissue 23, an electrode 21 and a cable 24.
[0026]
In use, the sensor 14 is inserted into the patient, for example, as described above with reference to FIG. 3, and the electrode 21 is provided approximately above the signal output electrode 17, for example, through the patient's skin, as described above. Methods of introducing a guide wire, as well as the methods necessary to attach the electrodes provided on the patient's skin for proper conduction, are well known to those skilled in the art. The core wire 11 and the electrode 21 are connected to the electronic unit 22.
[0027]
The current generated through the patient's tissue by applying the voltage needs to be low enough to be safely transmitted through the human body. It is preferable to select an acceptable value in accordance with International Standard IEC 601-1 (1998), Chapter 19. An alternating voltage with a frequency higher than 1 kHz that allows a weak DC voltage to be used, but to allow useful high currents through the body, for example up to 10 mA without jeopardizing patient health. In order to obtain AC, it is preferable to use an AC voltage.
[0028]
In a very simple embodiment, corresponding to the above description and schematically shown in FIG. 4, when measuring the temperature in the body, the sensor is at a temperature having a known relationship between temperature and resistance. The sensitive resistor 214 has one end connected to the core wire 211 (corresponding to the connection point 15 in FIG. 1) and the other end connected to the signal output electrode 217. The sensor is inserted into the body, fairly schematically as indicated by dotted line 223. The electronic unit 232 outside the body provides a voltage to the sensor 217 via the cable 26, the core wire 211, the signal output electrode 217, the body tissue 233, and the electrode 221 disposed on the skin of the body 233.
[0029]
The voltage provided by the electronic unit 232 may be an AC voltage or a DC voltage. The electronic unit 232 also comprises means for recording the overall resistance of the circuit through the body. Such means are well known and will not be described herein. By measuring the total resistance and knowing the temperature-resistance relationship of the sensor, the temperature at the sensor can be easily calculated.
[0030]
The main advantage of this embodiment is simplicity. However, it has the disadvantage of low accuracy and reliability. These disadvantages are the result of effects from other resistances in the monitoring circuit, such as the coupling impedance of the skin electrode 221. In general, when applying an AC voltage, the sensor is typically connected to a circuit that includes a rectifier that converts the AC voltage to a DC voltage to drive a sensor selected as sensitive to the physical parameter being examined. An example used in such applications and useful for measuring cardiovascular pressure is Transducers '87 (The 4th international conference on solid state sensors and actuators), p. 344 by H. Chau and KD Wise, An ultraminiature solid-state pressure sensor for a cardiovascular catherter.
[0031]
As described above, the sensor output signal is processed by circuitry connected to the sensor such that information representing the level of the monitored physical parameter is superimposed on the signal provided by the electronic unit. The electronic unit includes a circuit that calculates the value of the inspected parameter based on the superimposed signal. One embodiment of such an electronic unit 332 is shown in FIG. 5, in which the guidewire assembly provides a core wire 321, sensor unit for providing electrical signals through the patient's tissue 326. 303 and body electrode 317 are schematically represented. The guide wire assembly is introduced into the patient (indicated by dotted line 325). The electronic unit 332 is connected to the core wire 321 via the cable 26 and to the outside of the body via the tissue and the second cable 24.
[0032]
The electronic unit 332 includes a drive oscillator 310 that provides an AC voltage in the range of 2 to 10 V, typically at a frequency in the range of 100 kHz to 1 MHz. The drive oscillator 310 is connected to a drive amplifier 301 that drives a first transformer 302, which is connected to the circuit non-dc through the body to provide a supply voltage. The second transformer 304 connected to the circuit through the body in a non-DC manner is used for detection of the superimposed signal. The signal is amplified by an amplifier 305, and low-frequency and high-frequency interference is removed using a narrow band filter 306. The bandpass filter 306 can be, for example, a so-called phase sensitive amplifier or a synchronous amplifier.
[0033]
A Schmitt trigger (or comparator) 307 is connected to the output of the bandpass filter 306 and triggers (transmits a digital “1”) at a selected voltage threshold level. The digital microprocessor 308 correlates the trigger pulse with the clock pulse generator 309 and counts the number of clock pulses between successive trigger pulses.
[0034]
6A to 6E are interconnected with respect to the time axis and illustrate the decoding operation of the measurement signal provided by the sensor unit 303 in the setup according to FIG. The sensor unit 303 is a unit including an oscillator and corresponds to the sensor circuit described above with reference to FIG.
[0035]
FIG. 6A shows the oscillator output signal from the sensor unit 303. The measurement conditions, i.e. the measured variables, determine the pulse widths T1, T2.
FIG. 6B shows the power consumption of the sensor unit 303. The power consumption is essentially constant, with a peak superimposed in time that coincides with the transition of the sensor oscillator from “0” to “1” or vice versa.
[0036]
FIG. 6C shows an output signal from the Schmitt trigger 307. The trigger threshold is shown as a horizontal dotted line in FIG. 6B.
FIG. 6D shows the clock pulses from the clock pulse generator 309 calculated by the microprocessor 308 to determine the time interval T1.
[0037]
FIG. 6E shows the clock pulses from the clock pulse generator 309 calculated by the microprocessor 308 to determine the time interval T2.
Thus, by determining the time intervals encoded by the sensors and corresponding circuitry, information about the measured physiological variable can be obtained via electrical signals passing through body tissue.
[0038]
FIG. 9 shows one embodiment of the present invention comprising an acoustic sensor. As shown with the previous embodiment, the guide wire 410 is provided with the core wire 401 covered with the insulating layer 402. The distal end of the guide wire is provided with a rounded tip 404 and a coil 403 acting as a signal output electrode according to the present invention, as described above. A piezoelectric ceramic plate 407 such as a PZT (zirconate titanate) plate is connected to the core wire and to the signal output electrode 403. The micromechanical acoustic resonator 406 is attached to the piezoelectric ceramic plate 407. The resonator should be chosen such that the resonant frequency depends on the physiological change being measured. An example of a useful micromechanical acoustic resonator is disclosed in US Pat. No. 5,096,096 entitled "Polysilicon resonating beam transducers and methods of producing the same" to H. Guckel et al. No. 5,188,983.
[0039]
As described above, the piezoelectric ceramic plate 407 responds with mechanical vibrations transferred to the resonator 406 when energized by an alternating voltage provided through body tissue. As shown in FIG. 10, at the resonance frequency f1 or f2 (corresponding to series resonance or parallel resonance), the peak point and the valley bottom point respectively appear in the electrical impedance. The electrical impedance is detected by an external electronic unit corresponding to the unit described above with reference to FIG. 5, and as a result, the physiological variable being sought can be calculated.
[0040]
Thus, in the guide wire assembly and communication system according to the present invention for determining physical parameters in a patient's body, a single wire provided on the guide wire is used to detect by a sensor in the body. Can transfer information about the physiological variables. This is obtained according to the present invention by using patient tissues such as blood and skin which function as a conductor in cooperation with the guidewire according to the present invention.
[0041]
The guide wire assembly according to the present invention is very simply manufactured with a small number of components. The sensor circuit is easily connected to the exposed section of the core wire at the distal end of the guide wire using any suitable conventional method, such as soldering, along with associated body electrodes. Any appropriate connector means can be used to connect the core wire to the electronic unit without the need for additional cables. Furthermore, as shown in the above embodiment, the present invention has no flexibility other than the core wire, so that the guide wire is placed in the blood vessel for a period of time during which the guide wire is placed in a suitable flexibility and symmetry. Allows sensor guidewire designs that are provided with flexibility.
[0042]
Another embodiment of the present invention, referred to as a double wire embodiment, is shown in the schematic diagram of FIG. According to FIG. 7, the guide wire 210 is similar to the guide wire 10 of FIG. 1 in that it includes, for example, an insulated core wire 11, but additionally includes an insulated second conductor 31. . In the distal portion, the insulating property is removed from the second conducting wire 31 near the far end of the guide wire, and the electrode 32 is formed by exposing the conductor.
[0043]
As shown in FIG. 8, when inserted into the patient's body 25, the core wire 11 of the guide wire 210 is connected to an electronic unit 222 similar to the electronic unit 22 of the first embodiment. The second conducting wire 31 is also connected to the electronic unit 222. At the same time, the insulated second lead electrode 32 is inserted into the body along with the guide wire and contacts the patient's bodily fluid. In use, the electrical circuit including the core 11, the sensor (and any additional electronic circuitry) 14, the signal output electrode 17, the lead 31, the electrode 32, the connecting leads 24, 26 and the electronic unit 222 is the body tissue 23 or patient. Closed through the blood.
[0044]
For this reason, the electrical circuit includes the patient's body tissue, as described in the previous embodiments. However, in the double wire embodiment, no electricity is transmitted through the patient's skin and no electrode is provided on the patient's skin. Instead, the electric signal output from the signal output electrode 17 propagates to the second electric wire 31 through the surrounding blood.
[0045]
Thus, when using the double wire embodiment, there is no need to provide electrodes on the patient's skin. This comes at the cost of manipulating the guidewire more complicated and difficult.
[0046]
According to the second embodiment, it is necessary to connect the guide wire by using two connectors, both of which are any suitable connectors such as a simple and low-cost alligator type connector. It is possible.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a distal end of a guide wire according to the present invention.
FIG. 2 is a cross-sectional view of the distal end of a guidewire according to another embodiment of the present invention.
FIG. 3 is a schematic diagram showing a system according to the present invention being used for a patient.
FIG. 4 is a schematic diagram of a simple embodiment of the present invention.
FIG. 5 is a block diagram of one embodiment of an electronic unit used in conjunction with the present invention.
6A-6E are interconnected time charts illustrating the decoding operation of a measurement signal provided by a sensor unit configured in accordance with the present invention.
FIG. 7 is a diagram of an embodiment of a double line of the present invention.
FIG. 8 is a schematic diagram showing the embodiment of FIG. 7 being used for a patient.
FIG. 9 shows one embodiment of the present invention with an acoustic sensor.
FIG. 10 is a chart of impedance versus frequency for one embodiment with an acoustic sensor.
FIG. 11 is a block diagram illustrating one embodiment of a sensor and associated circuitry.

Claims (10)

A power supply electronic unit (22, 222, 332), an electric wire (11) having a far end for insertion into a living body and a near end for electrical connection to the electronic unit (22, 222, 332); 11) a sensor (14, 502, 406) connected to the proximal end of 11) for measuring physiological variables in vivo in blood vessels,
A body electrode (17; 117, 113B; 317; 405) connected to the sensor (14, 502, 406) for physical and electrical contact with body tissue when placed at the measurement site An internal electrode having a portion of
A second electrode (21, 24; 221; 32) for electrical connection to the electronic unit (22, 222, 332) for electrically contacting the second part of the living body A second electrode having
And transmitting an electrical signal from the electric wire to the second electrode through the sensor, the body electrode, and the body tissue .   The system according to claim 1, wherein the intrabody insertion wire (11) is a core wire extending through a guide wire.   The system of claim 1 or 2, wherein the electrical unit (22, 222, 332) includes AC power for powering the sensor (14) with an AC voltage through the body tissue.   The system of claim 3, wherein the AC voltage is in the range of 2-10 V and the frequency is in the range of 100 kHz to 1 MHz.   The system according to claim 1 or 2, wherein the electronic unit (22, 222, 332) comprises a DC power source.   The system according to any one of claims 1 to 5, wherein the second electrode is a second electric wire (31) having an electrode portion (32) at the distal end for insertion into the body. An electric wire (11) extending along the guide wire (210) and any one of the pressure sensor and the temperature sensor (14, 14) connected to the electric wire (11) at the far end of the guide wire (210). 214, 502, 406) a guide wire (210) for measuring physiological variables in vivo in blood vessels,
When a body electrode (17; 117, 113B; 317; 405) is connected to the sensor (14, 502, 406) and the body electrode (17; 117, 113B; 317; 405) is placed at the measurement site. A guide wire having a portion for physical and electrical contact with body tissue.   The guide wire according to claim 7, wherein the electric wire (11) is a core wire extending through the guide wire (210).   The guide wire according to claim 7 or 8, wherein a coil (113B) disposed around a distal end of the guide wire (210) is connected to the sensor and functions as the body electrode.   A second electric wire (31) extending along the guide wire (210) is attached, and the second electric wire (31) is physically and electrically connected to a body tissue near the distal end of the guide wire (31). 10. A guide wire according to claim 7 or 9, characterized in that it has an electrode part (32) for contact with the body.

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