WO2006121371A1

WO2006121371A1 - Biological tissue stimulation by magneto-acoustical action

Info

Publication number: WO2006121371A1
Application number: PCT/RU2006/000232
Authority: WO
Inventors: Andrei Gervasievich Vasiliev; Vladimir Vasilievich Kopeikin
Original assignee: Schekutiev, Georgy Alexandrovich; Margulis, Milya Arkadievich
Priority date: 2005-05-12
Filing date: 2006-05-05
Publication date: 2006-11-16
Also published as: RU2005114342A; RU2316368C2

Abstract

The invention relates to a method for exposing biological tissue areas (brain and other human being and animal organs) to a stimulating action and to a device for carrying out said method without using implantable electric conductors (electrodes). The inventive method consists in producing a stimulating current directly in a biological tissue by generating an external magnetic field therearound and in locally exciting the mechanical oscillating movement of the tissue segment with the aide of ultrasound waves focused thereon. According to the electromagnetic induction law, a current producing stimulating effect on the selected segment of the biological tissue mechanically oscillating in the magnetic field is generated. The inventive method has the following advantages: non-invasiveness, possibility of focusing the action and forming a physiologically appropriate current density in any required tissue volume at any location, the simplicity of stimulation parameter control and a painless stimulation process.

Description

STIMULATION OF BIOLOGICAL TISSUES USING MAGNETO-ACOUSTIC INFLUENCE

Technical field

The invention relates to a method for magnetoacoustic exposure to areas of biological tissues, for example, structures of the nervous system, or tissues of other organs of animals and humans, as well as a device that implements it, without using implantable electrodes. This allows for non-invasive effects.

BACKGROUND OF THE INVENTION In medicine, a method is known for curative and research effects on certain parts of the nervous system with electrical impulses supplied through electrodes implanted into the body. It is important to note that electrical stimulation is the most adequate, since most brain functions are realized through the generation and distribution of electrical potentials.

The main disadvantage of this method is trauma to the patient’s body. In addition, the neurosurgeon does not always know exactly where this patient needs to implant electrodes and whether to do it at all. It is clear that this is fraught with the inefficiency of the operation, which is complicated by the presence of rather large material costs for treatment, due to the high cost of implantable electrical stimulators and their electrodes.

In the nervous system there are a large number of neurons and their axons, which from the physical point of view are conductors, and which are directed by the influence of electric current during the method of implantable electrodes.

Neurons and axons can be considered as biological conductors in which currents circulate in the form of nerve impulses that determine the nervous activity of the body. In the method of implantable electrodes, an electrical contact of such a biological conductor with an electrode is carried out, when an external voltage is applied to it, a current from an external source begins to flow in the biological conductors. This current has the desired effect of either stimulating or blocking the passage of nerve impulses. The world's leading manufacturer of implantable stimulants is Medtropis (USA) (www.medtropys.com).

The main disadvantages of using the method of implantable stimulants are the following: - the need for surgical intervention, respectively, trauma, and as a consequence the risk of complications;

- the presence of anatomical and functional variability in the structures of the human brain sometimes requires several diagnostic immersions of the electrodes, which increases the invasiveness of the operation; - often there is a need to replace the electrodes due to inflammatory reactions of biological tissue or wrapping the electrodes with connective tissue, which reduces the stimulation effect.

Today, in the absence of the effect of drug therapy, the only surgical method used is the implantation of stimulants and electrodes. The essence of the method described in the following publications. (2, 3)

SUMMARY OF THE INVENTION

The main idea of the proposed method is that instead of connecting a biological conductor to an external current source through an implantable electrode, this current is generated directly in a selected area of the biological conductor (for example, in a neuron or axon).

As you know, based on the law of electromagnetic induction, an electromotive force (EMF) of induction arises in a conductor moving in a magnetic field.

The essence of the proposed method is to place biological tissue (for example, brain tissue) in an external magnetic field and local excitation of the vibrational movement of the sections of the conductors

(neurons, axons) using focused ultrasound waves. In this case, the mechanical vibrations of the bodies of nerve cells (neurons) and their processes - axons

- (or other biological conductors) are caused by ultrasound. The magnetoacoustic effect indirectly leads to the appearance of an electric current in biological conductors, which has a direct effect. Therefore, this method relates to electrical stimulation.

The advantages of this method of electrical stimulation are: non-invasiveness, the ability to focus the electric field and create a physiologically adequate current density in any required tissue volume of any location, ease of adjustment of stimulation parameters, painless stimulation procedure (in contrast to transcranial electrical stimulation, which is also extremely unfocused).

It is also important that magnetoacoustic stimulation can be an effective tool in determining indications and places for implantation of electrodes in each individual case.

The proposed method can also stimulate spinal cord tissue and peripheral nerves. In addition, the method can be applied to solve problems in the field of cardiology, which can also be solved by the proposed electrical stimulation. Brief Description of the Drawings

Fig.l - is a structural diagram of the installation (top view). Figure 2 - is a structural diagram of the installation (side view). DETAILED DESCRIPTION OF THE INVENTION

The invention is described below by the example of remote electrical stimulation of deep brain structures by the proposed method. However, it is obvious that instead of the nervous tissue of the brain, it is also possible to act on other tissues of the human or animal body.

The law of electromagnetic induction is described by the formula:

E = V * B * 1 (1)

Here E is the EMF induced in a conductor of length 1 moving at a speed V in a magnetic field of magnitude B. In this particular case, the conductor is a neuron or axon. Formula (1) can be used to describe the mechanism of the occurrence of electric current in a biological conductor.

In accordance with (1), the induction EMF induced in the conductor depends on the magnitude of the magnetic field and the mechanical speed of the conductor.

If the magnetic field and / or speed of the conductor are variables, then the induced EMF will also be a variable.

To influence acoustic waves on a separate section of a conductor of a certain length, it is necessary to focus these waves on a selected section. Moreover, to ensure the focusing conditions of acoustic waves, a sufficiently high frequency of ultrasound is necessary, since the “spot” of focusing depends on the length of the ultrasonic wave. The magnitude of this spot is approximately equal to several wavelengths. To ensure the locality (point) of the impact, a short wavelength is needed, i.e. high frequency. For example, to provide a focusing spot with a size (diameter) of 1.5 mm, the ultrasound frequency should be of the order of f = 1 MHz.

In a constant magnetic field, the frequency of the induced current will also be equal to 1 MHz. However, a current of this frequency does not have an exciting electric effect on neurons and axons. To create a current of low frequency F, which in a particular case can take a zero value (in this case, the current becomes actually a constant current), the magnetic field must change with a frequency f + F or f - F.

Monochromatic waves and vibrations are described, as is known, by harmonic functions - sine and cosine. If we assume that in the formula (1) V = V ₀ * cos (2πft), B = B ₀ * cos (2πft + 2πFt), then, up to the coefficient K of proportionality of the corresponding dimension, in accordance with (1) and trigonometric identity cos α * cos β = 1/2 * cos (α + β) * cos (α - β) we obtain: E - V * B * 1 =

= K * cos (2πft) cos (2πft + 2πFt) = K * cos (2πFt) + K * cos (4πft + 2πFt) (2)

(2π is the coefficient of proportionality between the cyclic and circular frequencies.)

Thus, a low difference frequency F (the first term on the right-hand side of (2)) appears in the spectrum of the current induced in the biological conductor. Here t is time.

In the above equations, V is the mechanical vibrational velocity biological conductor, which does not move with the ultrasonic wave, but remains in place, performing only oscillations. The changing magnetic field of the indicated frequency also has an oscillatory (quasistatic) character.

The following is taken into account. Acoustic waves at a low frequency cannot be focused on the size of the patient’s head. Therefore, a high frequency f must be present both in the acoustic and in the magnetic field, but one of them must differ from the other by a small difference frequency F in order to obtain a low-frequency spectral component in accordance with formula (2). When focusing the acoustic waves (ultrasonic frequency) on a selected tissue site in this area, a mechanical oscillatory movement is created in response to the aforementioned exposure to acoustic waves, thereby forming a low frequency current in the selected tissue area in accordance with (2). This low-frequency current arising in the tissue site has a stimulating effect on the tissue.

In this case, the oscillations of the acoustic waves are synchronized with the oscillations of the external magnetic field. Description of the installation The block diagram of the installation is illustrated in FIGS. L and 2. The head of patient 1 is partially immersed in a container 5 filled with physiological saline, distilled water or gel, which has acoustic properties close to human tissues. Coordination of the acoustic properties of the solution and human tissues is necessary so that ultrasound from the solution can pass into these tissues without noticeable attenuation. The solution contains a focusing ultrasound source 3 in the form of a concave piezoceramic plate. The concavity of the plate provides focusing. Around the head are turns (one or more) of an electric wire, which is a winding of an electromagnet 4 for

'creating the necessary magnetic field. The operating frequency range of ultrasound is from 0.3 to 5 MHz. In this case, the magnetic field frequency differs only by a low frequency F = 0-1000 Hz. The formation of ultrasonic vibrations is possible in both pulsed and continuous modes.

FIXED SHEET (RULE 91 ISA / RU) Although the proposed embodiment uses a concave piezoceramic plate, in the general case, the ultrasonic wave can be focused in several ways:

1. Reflective mirrors. 2. A radiating plate having a concave geometry, in this case, the momentum can be transmitted to the brain structures through an elastic pad, for example, in the form of a gel-filled pillow, which does not require placing the person’s head in a “container”.

3. A phase grating, the emitters of which can be applied directly to the head, which is most optimal for focusing and research, but requires large expenses for calculations and manufacturing.

The synchronization of acoustic and magnetic waves can be carried out in one of the following ways. For example, at a difference frequency F = O, the piezoelectric emitter of acoustic waves and a coil for generating a magnetic field are fed from a single generator, which automatically ensures synchronization. In the pulsed mode, the initial phases of the ultrasonic and magnetic pulses must coincide, for example, when the unit is switched on from one toggle switch or through a special pulse generator. In continuous operation, when the frequency F is not equal to zero, synchronization is not required. Thus, synchronization is needed only at F = 0 and the pulse mode of the system.

The scheme of the installation

Installation works as follows. Selected area of the brain 2, which should be subjected to electrostimulating effects. The focus of the piezoceramic ultrasound source 3 is aimed at this area by moving the piezoacoustic system 3 inside the vessel 6.

The ultrasonic emitter 3 and the electromagnet 4 synchronized with it in frequency are turned on (synchronization provides the necessary frequency spacing between the acoustic and magnetic fields), which will lead to mechanical vibrations of neurons and their axons at the focal point under the influence of ultrasound and the appearance of electromagnetic induction in them in accordance with formula (1) i.e. stimulating impulse. Formed a stimulating impulse can be used to excite or inhibit (depending on the frequency of the impulses) in the corresponding structures - targets of the nervous system and, thereby, provide a therapeutic effect in a number of diseases. LITERATURE

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Claims

CLAIM

1. A method of stimulating areas of biological tissues of an organism by exposing them to acoustic and magnetic waves, comprising the steps of: - creating around the tissue on the area of which it is necessary to influence, an external magnetic field that changes with a first frequency,

- they act on the selected tissue site with acoustic waves focused on it, changing with a second frequency, while the vibrations of the acoustic waves are synchronized with the vibrations of the external magnetic field.

2. The method according to claim 1, wherein the frequency difference is a low frequency.

3. The method according to claim 1, wherein the focusing of the acoustic waves is performed by reflective mirrors.

4. The method according to claim 1, wherein the focusing of the acoustic waves is performed by a radiating plate having a concave shape.

5. The method according to p. 1, in which in response to the aforementioned impact of acoustic waves on a tissue site creates a mechanical oscillatory movement of this site.

6. A device for stimulating areas of biological tissues of the body by exposing them to acoustic and magnetic waves, containing:

- a source of an external magnetic field, changing with the first frequency, to create an external magnetic field around the tissue on the area of which it is necessary to influence,

- a source of acoustic waves changing with a second frequency, while the vibrations of the acoustic waves are synchronized with the vibrations of the external magnetic field,

- a device for focusing acoustic waves on a selected area of body tissue.

7. The device according to claim 6, in which the said focusing device form a reflective mirror.

8. The device according to claim 6, in which said focusing device is a radiating plate having a concave shape.

9. The device according to claim 6, in which the difference of the first and second frequencies is a low frequency.