CN101391131B - Nervous system magnetic induction electrical stimulation device - Google Patents

Abstract

Disclosed is a nervous system magnetic induction electro-stimulation device, which comprises a stimulator (1), an exciting coil (2), an induction coil (3) and a stimulating electrode (4). The induction coil (3) is positioned in subcutaneous tissues of a patient, and is parallel to the plane of the back of the patient. The stimulating electrode (4) is fixed on the backbone of the patient (5), one end of the stimulating electrode (4) is connected with the induction coil (3), and the other end thereof is in contact with nerves. The exciting coil (2) is positioned outside the patient, and is coaxial with the induction coil (3). The stimulator (1) is placed near the patient for providing the pulse current to the exciting coil (2). The distance between the exciting coil (2) and the induction coil (3) is between 10 and 30mm. when in stimulation, the exciting coil (2) generates a pulse magnetic field under the action of the pulse current provided by the stimulator (1), the magnetic line of force penetrating through the induction coil (3) alters with time, and the induction coil (3) will generate the induction electromotive force and form an electric field on nerves between two electrodes, thereby exciting the nerves.

Description

A kind of nervous system magnetic induction electrical stimulation device

Technical field

The present invention relates to a kind of nervous system magnetic induction electrical stimulation device.

Background technology

Spinal cord injury (Spinal Cord Injury, SCI) reconstruction after is one of difficult point of Neuroscience Research, along with microelectric technique, the development of microprocessing and neuroscience, rehabilitation engineering worker's successful application functional electric stimulation (Functional Electrical Stimulation, FES) system makes the Patients of Spinal enough handss of energy and lower limb complete partial function, and acquisition control is to a certain degree urinated and the function of relieving constipation.In order to reach the purpose of life-time service, the FES system need to implant, but power volume is huge and the problem that needs to change is restricting the development of FES always.Just have the scholar to propose to utilize a pair of emission-receiving coil to realize the transmission of electric energy as far back as the seventies in last century, receiving coil receives the radiofrequency signal from transmitting coil, and to be translated into dc signal be the stimulator power supply that implants.At present a lot of implantation type electric stimulation devices adopt this power transfer mode, and frequency is generally the hundreds of megahertz, as United States Patent (USP) 5741316,6804561,7177698,7209792,7392091.Although this power transfer mode makes the size of implant devices get reducing to a certain extent, the implant devices volume is still larger, has affected patient's activity.Also do not have at present patent to adopt pulse electromagnetic field to carry out energy delivery.

Utilize in addition oscillating electric field to stimulate to promote axon regeneration after SCI, make patient's recovered part function.Patent about oscillating electric field stimulating instrument and Therapeutic Method has four at present, is United States Patent (USP) (patent No. 4774967,4919140,6975907 and 7199110), and device adopts battery powered, and therapeutic modality is for implanting or semi-implantation type.But existing research finds that using the effective time of oscillating electric field stimulation therapy is 6-12 month, existing battery is difficult to satisfy the requirement (otherwise volume can be very large) that works long hours, therefore existing patented technology is difficult to accomplish long-time implantation, and the device of semi-implantation type (1 year) problem such as be difficult to avoid infection that works long hours.

With respect to the FES system that needs implant devices, noninvasive magnetic stimulating method is more easily accepted by the patient.It is according to Faraday law of electromagnetic induction that magnetic stimulates, and the time-varying magnetic field that utilizes the changing currents with time in coil to produce forms induction field, thereby makes neural excitation on nerve.Say in a sense, magnetic stimulates and the principle of electricity irritation is identical, and when the induction field value surpassed threshold value, nerve will be excited, reaches the effect identical with electricity irritation.At present in the patent that magnetic stimulates, all that the more shallow nerve in position is stimulated, Chinese patent 200510015749.4 has designed multilead magnetic stimulator for brain, fix 128 coils in the head-shield inboard, corresponding to 128 circuit controll blocks, the all coils shape is identical, and field stimulation can reach any range of human brain.Chinese patent 200510077042.6 uses a pair of coaxial coil to carry out stimulated in vitro to nerve, and two coils all need power drives.Chinese patent 94102890.9 stimulates magnetic and with ultrasonic combining, subcutaneous nerve is stimulated.Although above-mentioned patent has realized stimulating for the external noinvasive of nerve, but with decaying apart from rapid, magnetic stimulates also can't act on the nerve of putting than deep-seated in body due to magnetic field, and because the focusing of magnetic stimulation is poor, can cause non-target tissue excited during stimulation, cause side effect.

Summary of the invention

The objective of the invention is to overcome existing implanted electric stimulator and contain built-in power and bulky, and directly magnetic stimulates depth as shallow, the poor shortcoming of focusing, by being embedded in vivo induction coil and stimulating electrode, then the method that carrying out magnetic stimulates improves supraneural electric field intensity, and can be applied to the human body deep nerve stimulates.

The present invention is comprised of device two parts in external device and body.External device comprises stimulator and excitation coil, is used to provide pulsewidth less than the pulsed magnetic field of 0.5 millisecond, but not radio frequency electromagnetic field; Body comprised induction coil and stimulating electrode in inner minute, be used for producing induction electromotive force and complete electricity irritation, and in body, part itself does not contain built-in power.

Part is very little induction coil to be imbedded subcutaneous in body of the present invention, and described coil two ends connect and neural contacted stimulating electrode by wire, at excitation coil coaxial with induction coil of external placement.During stimulation, excitation coil produces pulsed magnetic field under the effect of the pulse current that is provided by stimulator, makes produce induction electromotive force in induction coil and form electric field on the nerve between two electrodes, thereby makes neural excitation.

Stimulator of the present invention utilizes the electric capacity of store electrical energy that excitation coil is discharged, and produces pulse current.By the adjustment to the stimulator parameter, realize the external control to the magnetic induction electrical stimulation effect.

Excitation coil of the present invention is formed by copper wire winding, and outer surface cover has insulation crust.Excitation coil under the effect of pulse current in its vicinity the space produce pulsed magnetic field.The inductive impact of excitation coil amplitude and the pulsewidth of pulsed magnetic field, and its size and shape has affected the distribution of magnetic field and induction field.

Induction coil of the present invention is made by the high conductivity material, and there is biocompatible materials (as silicones, Teflon, polyimides) parcel the outside, and its size is less, and diameter 10～30mm is simple in structure, has reduced the implantation risk, is easily accepted by the patient.Induction coil is used for receiving the external energy that is delivered in body, under the effect of pulsed magnetic field, the magnetic line of force that passes induction coil changes in time, according to Faraday law of electromagnetic induction, can produce induction electromotive force in induction coil, this induction electromotive force can be used as the stimulus of nerve stimulation, and need not built-in power.In addition, fixedly the time, induction electromotive force E is determined by the distance between two coils, rather than the distance between nerve and excitation coil when two coil shapes, the distance that this just is equivalent to further between nerve and excitation coil has solved the problem that direct magnetic stimulates depth as shallow; Induction electromotive force is the loop integral of induction field on induction coil in addition, and its effect is that the energy that magnetic stimulate to disperse is focused on stimulating electrode two ends, has improved the focusing that direct magnetic stimulates.

Stimulating electrode one end of the present invention is connected with induction coil, and the other end contacts with nerve, when producing induction electromotive force in induction coil, can produce electric field on the nerve between two electrodes.When this electric field is enough large, just can make neural excitation.

Description of drawings

Fig. 1 is the schematic diagram of magnetic induction electrical stimulation, in figure: 1 stimulator, 2 excitation coils, 3 induction coils, 4 stimulating electrodes, 5 spinal columns, the wire between 6 stimulators and excitation coil;

Fig. 2 is the work process block diagram of magnetic induction electrical stimulation device.

The specific embodiment

Further illustrate the present invention below in conjunction with the drawings and specific embodiments.

Explanation the specific embodiment of the present invention, as shown in Figure 1, the present invention includes stimulator 1, excitation coil 2, induction coil 3, stimulating electrode 4 as an example of the magnetic induction electrical stimulation of spinal cord example.Induction coil 3 diameter 10～30mm, be positioned at patient body, be connected with stimulating electrode 4, stimulating electrode 4 is fixed on spinal column 5, can make intravertebral spinal cord excited during stimulation, excitation coil 2 is positioned at outside patient body, and is coaxial with induction coil 3, and the distance between excitation coil 2 and induction coil 3 is between 10～30mm.Stimulator 1 is placed near the patient, for excitation coil 2 provides pulse current, connects stimulator and excitation coil by wire 6.

The circuit model of stimulator 1 is the RLC charging and discharging circuit, and high-voltage DC power supply charges to initial voltage V0 to capacitor C; After charging was completed, L discharged to coil.Make α=R/2L, wherein R is coil resistance, (α in the underdamping situation ²-1/LC＜0), the electric current in coil is:

$I\left(t\right)=\frac{V_0}{\mathrm{\ωL}}{e}^{-\mathrm{\αt}}\sin \left(\mathrm{\ωt}\right)---\left(1\right)$

ω wherein ²=1/ (LC)-α ², during practical application, only having kept first posivtive spike of current waveform, its pulsewidth is T _p=π/ω, it is worth below 0.5ms.

Excitation coil 2 is the circular planar disk-like coil, after the design pulsewidth of stimulator parameter and pulse current is determined, can calculate the inductance of excitation coil:

$L=\frac{T_p^2}{C{\mathrm{\π}}^2}---\left(2\right)$

The inductance of excitation coil is determined by its shape, can be expressed as:

$L=\frac{{\mathrm{\&mu;}}_0}{8\mathrm{\&pi;}}{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="H2008102241717E00011.png"\; state="\{\{state\}\}">N</figure-callout>}}^2\mathrm{d\&psi;}---\left(3\right)$

N, d are respectively the number of turn and the average diameter of coil, and ψ is the parameter relevant with coil shape, can table look-up to obtain in relevant reckoner.Convolution (2) and formula (3) are optimized the shape of coil.Excitation coil is in the arbitrfary point, space

The vector magnetic potential that produces is:

Wherein:

$k_i=\sqrt{\frac{4a_i\mathrm{\&rho;}}{{(a_i+\mathrm{\&rho;})}^2+z^2}}---\left(5\right)$

K (k) and E (k) are respectively the first kind and complete elliptic integral of the second kind, a _iBe the radius of i circle coil, N is coil turn,

For

Unit vector on direction.

Induction coil 3 is made by the high conductivity material, and skin has the biocompatible materials parcel, with the coaxial placement of excitation coil.Under the effect of pulsed magnetic field, the magnetic line of force that passes induction coil changes in time, according to Faraday law of electromagnetic induction, can produce induction electromotive force in induction coil, and its value is the integration along induction coil direction inductor electric field E.Ignore the impact of surperficial stored charge, radius is that the induction electromotive force in the induction coil of b is:

$E={\&Integral;}_{\mathrm{coil}}E\&CenterDot;\mathrm{dI}=2\mathrm{\&pi;b}\frac{\&PartialD;A}{\&PartialD;t}---\left(6\right)$

By formula (4)-(6) as seen, when two coil shapes fixedly the time, induction electromotive force E determines by the distance between two coils, the distance between enclosing before this just be equivalent to further neural and excitation; Induction electromotive force is the loop integral of induction field on induction coil in addition, and its result is equivalent to concentrating in together with the induction field on Radius, thereby stimulates the energy that disperses will focus on stimulating electrode two ends magnetic.

Stimulating electrode 4 one ends are connected with induction coil, and the other end contacts with nerve, when producing induction electromotive force E in induction coil, can produce electric field on the nerve between two electrodes.If E is enough large, just can make neural excitation.

Work process of the present invention is as follows:

The explanation work process of the present invention as an example of the magnetic induction electrical stimulation of spinal cord example, as shown in Figure 2, at first by Operation induction coil and stimulating electrode, stimulating electrode is fixed on spinal cord, the induction coil that is connected with electrode is fixed on subcutaneous, induction coil and back plane parallel.During stimulation, according to the electrophysiological characteristics of spinal cord, select the excitation coil of suitable inductance and be connected on stimulator.Excitation coil is attached to patient body-surface, with the coaxial placement of induction coil, and the distance 10～30mm between two coils.The charging voltage that electric capacity in stimulator is set is a smaller value, begins to stimulate and observe effect of stimulation.Strengthen gradually afterwards stimulus intensity, until the patient produces muscle contraction, reach effect of stimulation.

Claims (1)

1. a nervous system magnetic induction electrical stimulation device, is characterized in that comprising stimulator (1), excitation coil (2), induction coil (3), stimulating electrode (4); It is subcutaneous that induction coil (3) is positioned at the patient, with patient back plane parallel; Stimulating electrode (4) is fixed on patient's spinal column (5), and stimulating electrode (4) one ends are connected with induction coil (3), and the other end contacts with nerve; Excitation coil (2) is positioned at outside patient body, and is coaxial with induction coil (3); Stimulator (1) is placed near the patient, and for excitation coil (2) provides pulse current, wire (6) connects stimulator (1) and excitation coil (2); The circuit model of stimulator (1) is the RLC charging and discharging circuit, and high-voltage DC power supply charges to initial voltage V0 to capacitor (C), after charging is completed, excitation coil (2) is discharged; Pulse current waveform in excitation coil (2) is unidirectional pulse, and described pulse current pulsewidth is less than 0.5ms; According to the electrophysiological characteristics of spinal cord, select the excitation coil of suitable inductance and be connected on stimulator;

Described excitation coil (2) is coaxial with induction coil (3), and the distance between two coils is between 10 ~ 30mm.

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