RU2472545C1 - Method for non-invasive destruction of biological tissues lying behind thoracic bones - Google Patents

Method for non-invasive destruction of biological tissues lying behind thoracic bones Download PDF

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RU2472545C1
RU2472545C1 RU2011131719/14A RU2011131719A RU2472545C1 RU 2472545 C1 RU2472545 C1 RU 2472545C1 RU 2011131719/14 A RU2011131719/14 A RU 2011131719/14A RU 2011131719 A RU2011131719 A RU 2011131719A RU 2472545 C1 RU2472545 C1 RU 2472545C1
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Вера Александровна Хохлова
Олег Анатольевич Сапожников
Леонид Рафаилович Гаврилов
Светлана Михайловна Шмелёва
Петр Викторович Юлдашев
Сергей Андреевич Ильин
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Вера Александровна Хохлова
Олег Анатольевич Сапожников
Леонид Рафаилович Гаврилов
Светлана Михайловна Шмелёва
Петр Викторович Юлдашев
Сергей Андреевич Ильин
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FIELD: medicine.
SUBSTANCE: invention refers to medicine, namely the use of ultrasound for local thermal and mechanical effect on biological tissue in ultrasound surgery. Biological tissue is exposed to focused ultrasonic bunch of high intensity within the frequency range of 0.8-2 MHz. The ultrasonic bunch is created in the form to provide minimal ultrasound ingress into thoracic bones on the bases of pre-determination of bone coordinates. What is also used is visualisation in generation of tissue boiling in an exposure centre. The exposure is conducted at ultrasonic bunch power to provide formation of short fronts in the primary focus with peak positive pressure 30-80 MPa. Local destruction is created within the arrangement of the primary focus without involving the side foci.
EFFECT: method enables reducing an focus splitting effect onto the primary and side foci after the focused ultrasound passes through a periodical rib structure.
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Description

The invention relates to the field of medicine and medical equipment, in particular to the field of application of ultrasound for local thermal and mechanical effects on biological tissues, and is intended for use in ultrasound surgery.

Powerful focused ultrasound (the common HIFU acronym for High Intensity Focused Ultrasound) is used in medicine to locally destroy deeply located tissues of the body, in particular tumors of the liver, breast, bones, kidneys, pancreas and uterus. When irradiating tissues shielded by the chest, such as the liver or heart, there are problems associated with focusing ultrasound through the bones of the chest.

The strong absorption and reflection of ultrasound on the ribs reduces the intensity of the acoustic field that has reached the focus, and therefore it may be insufficient for tissue destruction. Diffraction of the beam on the periodic structure of the edges leads to a splitting of the initial focus into the main focus and several secondary ones, which leads to an additional decrease in the intensity in the main focus, as well as to a deterioration in the locality of the effect. Overheating of bones and skin burns are one of the main side effects of radiation. The above problems limit the use of the HIFU method in medical practice.

Known methods for non-invasive destruction of biological tissues located behind the bones of the chest, including the use of focused ultrasound of high intensity and the formation of an acoustic field that minimizes the penetration of ultrasound on the bones. There is a method in which elements in a virtual lattice are turned off for which vectors normal to the surface of the element intersect an edge [Liu H-Li, Chang H, Chen W-S, Shih T-C, Hsiao J-K, Lin W-L. Feasibility of transrib focused ultrasound thermal ablation for liver tumors using a spherically curved 2D array: A numerical study. Med Phys 2007; 34 (9): 3436-3448].

Also known is a time reversal method for pulsed signals that overcomes the distortions introduced by the bones of the chest located on the propagation path of focused ultrasound [Aubry JF, Pernot M, Marquet F, Tanter M, Fink M. Transcostal high-intensity-focused ultrasound: ex vivo adaptive focusing feasibility study. Physics in Medicine and Biology, 2008; 53: 2937-2951].

There are also known methods of radiation and diffraction description of the propagation of ultrasound from focus to the therapeutic grating through the ribs, followed by phase reversal on the grating elements and reradiation of the harmonic HIFU signal, which can reduce the thermal effect on the ribs [Bobkova S., Gavrilov L., Khokhlova V., Shaw A ., Hand J. Focusing of high intensity ultrasound through the rib cage using therapeutic random phased array. Ultrasound in Medicine &Biology; 2010, 36 (6): 888-906].

The disadvantages of these methods is the presence of the effect of splitting the focus after the passage of focused ultrasound through the bones of the chest. In this case, the absorption of energy of the ultrasonic beam during the passage of the chest is significant and can lead to their overheating. In addition, when the focus is split due to the redistribution of the energy of the ultrasound beam to the lateral maxima, an additional decrease in the intensity in the main focus occurs by about a factor of two, which may become insufficient for thermal destruction of the tissue.

Known methods of using waves with shock fronts that are formed in the focus region due to the effects of nonlinear propagation of ultrasound in the tissue to increase the efficiency of heating the tissue tenfold compared with the case of irradiation with a harmonic wave of the same intensity [M. Canney, V. Khokhlova, O. Bessonova, M. Bailey, L. Crum. Shock-induced heating and millisecond boiling in gels and tissue due to high intensity focused ultrasound. Ultrasound in Medicine &Biology; 2010, 36 (2): 250-267; Yuldashev P.V., Khokhlova V.A. Simulation of three-dimensional nonlinear fields of ultrasound therapeutic arrays. Acoust Phys .; 2011, 57 (3): 334-343]. The result is achieved due to the fact that the absorption of energy of the ultrasonic wave at shock fronts is proportional to the third degree of the amplitude of the gap, in contrast to the quadratic dependence of pressure on the amplitude for a harmonic wave.

The disadvantages of these methods is that they are aimed only at enhancing the thermal effect in the main focus and do not solve the problem of minimizing the impact on the ribs and the effects of side maxima in the focus area.

A known method, including the creation of special distributions of the ultrasonic field on the elements of two-dimensional therapeutic gratings to increase the intensity in focus and locality of exposure after passing through inhomogeneities of soft tissues [US Patent No. US005590657A, publication date 01/07/1997]. The disadvantage of this method is that it does not provide for exposure to tissues located behind strongly absorbing ultrasound bones of the chest.

There is also known a method in which, in order to enhance the thermal effect of ultrasound in the focus area, a special agent is used, which is administered intravenously before the use of HIFU therapy [RF Patent No. 2363494, publication date 08/10/2009]. The agent is a biocompatible solution containing microbubbles or microparticles. The presence of the agent leads to increased absorption of ultrasound in the affected area and allows you to reduce the amount of acoustic energy required to damage the target tissue during irradiation, as well as to reduce the effect on the ribs during liver irradiation.

This method has disadvantages, since it leads to an increase in the absorption of energy of ultrasound not only mainly but also in secondary foci, therefore, it does not allow minimizing the effect of secondary intensity maxima.

Also known is a method of pulsed cavitation ultrasonic destruction of tissues, including the use of ultrasonic waves with shock fronts [US Patent No. US 20100069797 (A1), publication date 03/18/2010]. In its technical essence, this is a method of non-invasive mechanical destruction of biological tissues, including exposure by focused ultrasound to a given area of tissue with the formation of a cloud of cavitation bubbles in the focal region and visualization of the impact area. Irradiation is performed with short (several microseconds) pulses with shock fronts; the peak negative pressure required to create a cavitation cloud is about 20 MPa, and the pulse duty ratio is about 1%.

The method is based on the mechanical destruction of tissue and does not provide for thermal effects on the tissues, and also does not imply effects on the tissues located behind the bones of the chest. The effectiveness of the impact is determined by the large peak negative pressure, which is difficult to achieve.

The closest analogue (prototype) of the invention is a method of exposure to tissues using an ultrasonic phased array [US Patent No. US 2008200806 (A1), publication date 08/21/2008]. In its technical essence, it is a method of non-invasive destruction of biological tissues located behind the bones of the chest, including the use of focused ultrasound of high intensity, determining the coordinates of the bones that are in the path of the ultrasound beam, the formation of an acoustic field that minimizes the penetration of ultrasound on the bones, and exposure to focused ultrasound to a given section of fabric. The disadvantages of the prototype are the lack of locality of exposure and the presence in the created ultrasonic field of side intensity maxima, which reduces the safety and effectiveness of the impact.

The technical result of the present invention is to increase the locality of exposure by focused ultrasound, minimize the effect of side intensity maxima in the created ultrasonic field and further reduce the thermal effect on the ribs and surrounding tissues.

The technical result is achieved due to the fact that in the proposed method, the effect is carried out by focused ultrasound with an intensity in focus above the threshold of the nonlinear exposure mode with the formation of shock fronts in the acoustic wave and create local destruction only at the location of the main focus. A nonlinear exposure regime with the formation of shock fronts is realized upon exposure to tissues with a frequency of 0.8–2 MHz at a peak positive ultrasound pressure at a focus of 30–80 MPa and a duration of a single pulsed exposure T within 2–100 ms.

In this case, exposure can be carried out with visualization of the focus of exposure by increasing the duration of the pulses until boiling occurs in the focus area, which can be detected by the visualizer.

In addition, the effect can be carried out using repetitive pulses, the duration T of each of which and the pulse repetition rate of 1 / T rep are insufficient for boiling in the main focus. In this case, the radiated energy of the pulse coincides with either less than the energy radiated continuously during one period of T rep at a lower, for example, 10-20 times, peak intensity at the emitter, i.e. in linear irradiation mode.

The impact can also be carried out in the mode of repetitive pulses, with a duration T of each of which and / or a pulse repetition rate of 1 / T rep , at which boiling occurs in the main focus. In this case, the time-average intensity in the pulsed mode coincides or is less than the intensity emitted in the continuous mode at a lower, for example, 10-20 times, peak intensity at the emitter, i.e. in linear irradiation mode. The possibility of decreasing the time-average intensity during a pulse-periodic high-amplitude action with the formation of shock fronts in focus compared to irradiation with a low-amplitude harmonic wave is achieved due to more efficient absorption of ultrasound at the shock fronts. In addition, the interaction of ultrasound with vapor bubbles formed upon the action of pulses with shock fronts leads to an increase in the size of thermal destruction in the region of the main focus, as well as to additional mechanical destruction of the tissue.

The impact can be carried out both when boiling is achieved, and without, when scanning focus along a given path in a discrete or continuous manner, in a pulsed or continuous mode of irradiation, when choosing a scanning speed in the range of 2-8 mm / s, to achieve tissue destruction along the scanning path .

Thus, the invention allows to increase the locality of exposure by focused ultrasound, minimize the influence of side intensity maxima in the created ultrasonic field and further reduce the thermal effect on the ribs and surrounding tissues.

The proposed method is illustrated by drawings.

Figure 1. The focusing scheme of the ultrasonic beam using a phased antenna array through the ribs in the tissue layer. 1 - lattice, 2 - ribs, 3 - fabric layer.

Figure 2. The wave profiles in the tissue, calculated in the main focus (a) and secondary (b) foci at different levels of emitter intensity: I 0 = 2.5 W / cm 2 (1), 20 W / cm 2 (2), 40 W / cm 2 (3). Profile (1 ') was obtained without taking into account nonlinear effects and corresponds to linear focusing at the initial intensity I 0 = 2.5 W / cm 2 .

Figure 3. The power distribution of heat sources along the z axis of the emitter (a) and in the focal plane (b) along the y axis (x = 0) at various intensities on the emitter: I 0 = 2.5 W / cm 2 (1), 20 W / cm 2 (2), 30 W / cm 2 (3), 40 W / cm 2 (4). The curves are normalized to the maximum values of the power of heat sources calculated at given intensities without taking into account nonlinear effects. Curve 1 'corresponds to linear focusing at the initial intensity I 0 = 2.5 W / cm 2 .

Figure 4. Two-dimensional power distribution of heat sources Q / Q max , normalized to the maximum value in the corresponding distribution (upper row), temperature T ° C (middle row) and tissue destruction contours (lower row) in the plane of the axis of the emitter at the moment of reaching 100 ° C in the center main focus during continuous irradiation and various intensity levels on the emitter: I 0 = 2.5 W / cm 2 (1), 5 W / cm 2 (2), 20 W / cm 2 (3), 30 W / cm 2 (4 ), 40 W / cm 2 (5).

Figure 5. The dependence of temperature on time in the main (a) and lateral (b) foci for the same average time intensity of the emitter, but different peak intensities in the continuous mode at I 0 = 2.5 W / cm 2 (1) and in pulse-periodic modes at I 0 = 10 W / cm 2 (2), 20 W / cm 2 (3), 30 W / cm 2 (4), 40 W / cm 2 (5). Curves 1-5 were obtained during modeling taking into account nonlinear effects, curve 1 'was obtained without taking into account nonlinear effects and corresponds to the continuous mode at an intensity of I 0 = 2.5 W / cm 2 .

The results of numerical simulations show that for focused ultrasound, for example, with a frequency of 1 MHz, when shock fronts are formed in the focus with the amplitude of the pressure jump at the front, for example, 30-80 MPa, the heat release power in tissue increases, respectively, by 10-60 times compared with the case of irradiation with a harmonic wave of the same frequency and initial intensity. Nonlinear effects are amplitude-dependent; therefore, they are more pronounced in the main focus, compared with the side ones, where the amplitude is smaller. This allows one to choose the irradiation regimes when the shock front is formed in the main focus, but is not formed in the lateral foci. Such modes allow, respectively, a 10–30-fold decrease in the relative heat release level in the lateral foci, as well as a decrease in the total radiation energy to achieve thermal destruction in the main focus. The irradiation frequency in the range of 0.8–2 MHz is selected from the condition that the maximum absorption of ultrasound energy in tissue is reached at a depth of the exposure area. The invention is implemented, for example, as follows.

Example 1. Irradiation of tissue is carried out by single pulses until a temperature of 100 ° C is reached in the main focus with increasing intensity at the emitter. The results of numerical simulation of tissue irradiation with focused ultrasound, for example, with a frequency of 1 MHz through the ribs, show that when the intensity at the emitter increases, for example, by 16 times (from 2.5 W / cm 2 to 40 W / cm 2 ), shock fronts form in the focus . At the same time, during which the tissue is heated in focus to a temperature of 100 ° C, decreases by more than 7500 times (from 19 s to 0.0025 s). In the discontinuous mode, the thermal destruction of the tissue is small and localized only in the region of the main focus, while in the low-amplitude mode, thermal destruction occurs in the lateral foci and is larger.

The geometry of the simulation is shown in figure 1. Irradiation occurs in water using a phased antenna array consisting of 254 elements in the form of disks with a diameter of 7 mm, located in a quasi-random order on a spherical surface with a diameter of 170 mm and a focal distance of 130 mm. The z axis is directed along the axis of the acoustic beam. After passing the ribs, the acoustic field is focused into a layer of fabric 2 cm thick.

The calculation of the acoustic field in water and tissue is based on the Westervelt equation:

Figure 00000001

Here (acoustic pressure, L t is the operator describing the absorption of ultrasound in the tissue, t is time, Δρ = ∂ 2 p / ∂z 2 + ∂ 2 p / ∂y 2 + ∂ 2 p / ∂x 2 ; ρ 0 and s 0 is the density and speed of sound in the medium, α w is the absorption coefficient in water, ε is the nonlinearity coefficient in water or in tissue. The specific values of the parameters are: ρ 0 = 1000 kg · m -3 , s 0 = 1500 m · s - 1 , in water ε = 3.5, in tissue ε = 4.7, the absorption coefficient in water α w = 4.33 · 10 -6 m 2 / s. The absorption coefficient in the tissue linearly depends on the frequency and is α = 0.42 dB · cm -1 per frequency f = 1 MHz. Calculations are made taking into account the presence of ribs. I, that strips imitating ribs completely absorb ultrasound.

The choice of the irradiation frequency is determined based on the maximum energy absorption of the ultrasonic beam W when focusing to a depth l in the tissue: dW / dz = 2α (f) · W · exp (- 2α (f) l). Taking into account the linear dependence of absorption in tissue on frequency, we obtain f = 1 / 2lα. With a focusing depth of 5-12 cm, f = 2-0.9 MHz. We consider f = 1 MHz as an example.

The intensity distribution in the focal region is calculated in the approximation of a quasi-plane wave:

Figure 00000002

where | p n | - the amplitude of the nth harmonic of acoustic pressure. The initial intensity on the lattice elements is set equal to I 0 = 2.5, 10, 20, 30 and 40 W / cm 2 . Some lattice elements located in the geometric shadow of the ribs are turned off.

The spatial distribution of the power of heat sources Q is calculated according to the results of the acoustic model:

Figure 00000003

Modeling the evolution of the temperature distribution in the tissue is carried out using the heat equation, which is solved numerically by the finite difference method:

Figure 00000004

Here T ° С is the difference between the current and initial temperature as a function of coordinates and time. The initial temperature T 0 = 35 ° C, the heat capacity at a constant volume c v = 3.06 · 10 6 J · m -3 C -1 and the thermal diffusivity χ = 1.93 · 10 -7 m 2 s -1 . Based on the data on the evolution of temperature at each point in space, in accordance with the formula below, the thermal dose t 56.0 is calculated:

Figure 00000005

Here R 0 - 0.5, t 56.0 is the time equivalent of the heat dose, expressed in seconds. Exceeding a thermal dose of a threshold value of t 56.0 ≥1 s means tissue destruction.

When irradiated with harmonic waves in the absence of nonlinear effects, the power of the heat sources in focus is proportional to the square of the pressure amplitude of the fundamental frequency and is equal to:

Figure 00000006

When shock fronts are formed in focus, the absorption is proportional to the cube of the pressure jump at the front, significantly exceeds the absorption at the fundamental frequency of the wave and does not depend on the absorption coefficient in the tissue:

Figure 00000007

Figure 2 shows the dimensionless wave profiles in the main focus and in the lateral foci with increasing intensity values on the emitter I 0 : 2.5 W cm -2 (1), 20 W cm -2 (2) and 40 W cm -2 (3). Profile 1 corresponds to the linear focusing of the wave. At I 0 = 2.5 W cm −2, nonlinear effects are almost imperceptible and the wave profile at the focus is close to harmonic, strong nonlinear effects in the main maximum begin to appear with I 0 = 20 W / cm 2 , at an intensity I 0 = 40 W / cm 2 , a shock front is formed in focus. In this case, the wave profile in the lateral focus is practically not distorted and remains close to harmonic.

Using the formula for absorption on the shock front, one can obtain an estimate for increasing the efficiency of heat release in the tissue and the time of increasing the temperature to 100 ° C in the mode of action in the mode of shock waves compared with the action of a harmonic wave at the same intensity on the elements of the lattice. So, at the initial intensity I 0 = 40 W / cm 2 , which corresponds to the initial pressure ρ 0 = 1.1 MPa, the amplitude of the shock front at the focus is 82 MPa, the heat generation due to absorption at the front is Q shock = 85 kW cm -3 that is 60 times higher than the heat release power Q lin = 1.4 kW · cm -3 with linear focusing of the wave with the same initial intensity. The time estimate for increasing the temperature of the tissue in focus to 100 ° C in the mode of exposure in the mode of blast waves is only 2.7 ms.

Figure 3 shows the power distribution of heat sources along the beam axis z (a) and in the focal plane (b) along the y axis (x = 0) at various levels of intensity on the emitter: I 0 = 2.5 W / cm 2 (1), 20 W / cm 2 (2), 30 W / cm 2 (3), 40 W / cm 2 (4). The curves are normalized to the maximum heat release at the corresponding intensity, calculated without taking into account nonlinear effects. Curve 1 ′ corresponds to linear focusing at the initial intensity I 0 = 2.5 W / cm 2 . It is seen that when a gap is formed at the focus (I 0 = 30 and 40 W / cm 2 ), the heat release efficiency sharply increases compared to the linear case of harmonic wave absorption, 66 times at I 0 = 40 W / cm 2 , and the side maxima are practically imperceptible.

Two-dimensional distribution of the power of heat sources in the plane of the beam axis (upper row), as well as temperature (middle row) and the region of thermal destruction of tissue (lower row) at the time of reaching 100 ° C in the main focus are shown in Fig.4. As can be seen, with an increase in the initial intensity, the sizes of the main focus area and the relative level and size of the lateral distribution maxima decrease. At an intensity of I 0 ≥30 W cm – 2 , when shock fronts are formed in the focus, the impact region becomes very localized, and the side maxima disappear, since their level becomes negligible compared to the main maximum.

The temperature of 100 ° C in the main focus is reached in t = 19 seconds at an initial intensity of 2.5 W / cm 2 , in 0.2 s at I 0 = 20 W / cm 2 , and in 0.0025 s at I 0 = 40 W / cm 2 . A 16-fold increase in the initial intensity of the emitter leads to a decrease in the heating time in the main focus to 100 ° C by more than 8000 times. The splitting of the focus is observed at I 0 ≤20 W · cm -2 . For low intensities and continuous heating (I 0 = 2.5 W cm – 2 , t = 19 s), three maxima merge into one large region (Fig. 4a). For high intensities (I 0 = 20, 30, 40 W · cm -2 ), the fracture region is significantly localized, while the temperature in the lateral foci is insufficient for the onset of thermal necrosis (Fig. 4 c-d).

Thus, irradiation with a single high-amplitude pulse makes it possible to reach boiling points in milliseconds only in the main focus, to create local destruction of small sizes and to visualize the irradiation region by scattering from boiling bubbles.

Example 2. Irradiation of tissue is analogous to example 1, except that the impact on the tissue is carried out by repeating pulses, with different peak intensities in the pulse, the duration of each of the pulses is insufficient for boiling in the main focus and the duty cycle in the range 0.05-1, such that the total emitted ultrasonic energy during the pulse repetition period with a high-amplitude (nonlinear) exposure is the same or less than with a continuous low-amplitude (linear) exposure.

Under such irradiation, the thermal processes calculated in the heat equation do not include boiling, and the heat release power during pulse absorption can be averaged within the pulse repetition period. In the absence of nonlinear effects and the same time-average radiation intensity within the repetition period, the temperature increase will be the same when the peak intensity in the pulse changes. With the manifestation of nonlinear effects and the formation of shock fronts, absorption increases and the temperature rises more rapidly.

The temperature increase in the main focus and in one of the lateral foci during periodic repetitive irradiation and various values of intensity I 0 in a pulse is shown in FIG. 5. With increasing intensity in the pulse, the duty cycle of the pulses changes so that the total irradiation time and the total radiated power are the same for all cases. The total radiated energy during the pulse repetition period corresponds to the energy of continuous irradiation with an initial intensity of I 0 = 2.5 W cm -2 . Density at an intensity of 20 W cm -2 is 0.125, and at 40 W cm -2 it is 0.0625. At an intensity of I 0 = 30 and 40 W cm -2 , when a shock front forms in the main focus (Fig. 2), the rate of temperature increase at the main maximum increases significantly. At a side maximum, changes in the rate of temperature increase are insignificant.

The indicated method of using pulse-periodic exposure with high intensities in the pulse and the presence of shock fronts in focus allows one to obtain thermal damage in the main focus region in less time compared to continuous irradiation of lower intensity and the same radiated energy during the pulse repetition period. Since irradiation occurs in less time, the total absorbed energy in the lateral foci and on the edges decreases.

Similarly, it is possible to reduce the thermal effect on the ribs and in the lateral foci as compared to the continuous low-amplitude effect, choosing a high duty cycle of the high-amplitude pulses, so that thermal necrosis occurs in the main focus in the same time as with a continuous low-amplitude effect. In this case, the exposure time remains the same, but the average time intensity in the lateral foci and on the edges decreases.

Example 3. Irradiation of tissue is similar to example 2, except that the duration of each of the pulses when irradiated with high peak intensity on the elements of the lattice, for example 30 and 40 W / cm 2 and the formation of shock fronts in focus (figure 2), is selected sufficient for boiling in the main focus, but insufficient to achieve thermal necrosis at lateral maxima. When boiling occurs in the main focus, the thermal and mechanical effect of ultrasound on the tissue is enhanced by the reflection of ultrasound from vapor bubbles. In this case, the effect in the lateral foci and on the ribs does not change.

Example 4. Tissue irradiation is similar to examples 2 and 3, except that the focus area is scanned along a predetermined path at a speed of 2-8 mm / s and a larger fracture is created compared to the focal region of the beam. The scanning speed is determined from the condition that the transverse size of the fracture under the conditions of manifestation of nonlinear effects, for example, at I 0 = 20 W cm -2 , is 1 mm and is achieved in 0.2 seconds (Fig. 4). Then, when scanning at a speed of 5 mm / s, a continuous area of damage will be obtained.

Claims (6)

1. The method of non-invasive destruction of the biological tissues located behind the bones of the chest, which consists in exposing the biological tissue to a focused ultrasound beam of high intensity in the frequency range of 0.8-2 MHz, the ultrasound beam being created in a form that minimizes the penetration of ultrasound onto the bones chest based on preliminary determination of the coordinates of the bones and use visualization when boiling tissue in the focus of exposure, characterized in that the impact of exist at the power of the ultrasonic beam, providing the formation of shock fronts in the main focus with a peak positive pressure of 30-80 MPa, and create local destruction at the location of the main focus without damage in the side foci.
2. The method according to claim 1, characterized in that the effect on the tissue is carried out by single pulses with a gradually increasing duration in the range of 2 - 100 ms until the boiling of the tissue in the main focus, which is recorded using ultrasound imaging.
3. The method according to claim 1, characterized in that the effect on the tissue is carried out by repeating pulses, the duration of each of which is insufficient for boiling in the main focus and the duty cycle in the range of 0.005-0.03.
4. The method according to claim 1, characterized in that the effect on the tissue is carried out in a pulsed mode, while the duration of each of the pulses exceeds the time to reach the boiling point in the main focus.
5. The method according to claim 1, characterized in that the effect on the tissue is carried out continuously, while the duration of the continuous exposure exceeds the time to reach the boiling point in the main focus.
6. The method according to any one of claims 1 to 5, characterized in that the effect on the tissue is carried out with discrete or continuous movement of the focus inside the tissue along a predetermined path with a speed of 2-8 mm / s.
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RU2589649C1 (en) * 2015-03-19 2016-07-10 Федеральное государственное бюджетное образовательное учреждение высшего образования "Московский государственный университет имени М.В. Ломоносова" (МГУ) Method and device for non-invasive local destruction of biological tissue
RU2617374C1 (en) * 2016-04-28 2017-04-24 Федеральное государственное бюджетное образовательное учреждение высшего образования "Московская государственная академия ветеринарной медицины и биотехнологии - МВА имени К.И. Скрябина" (ФГБОУ ВО МГАВМиБ - МВА имени К.И. Скрябина) Method of directed acoustic impact on the functional state of cells-targets material of representatives of cat families
RU2639805C2 (en) * 2016-04-04 2017-12-22 Федеральное государственное бюджетное образовательное учреждение высшего образования "Московская государственная академия ветеринарной медицины и биотехнологии - МВА имени К.И. Скрябина" (ФГБОУ ВО МГАВМиБ - МВА имени К.И. Скрябина) Method of directed non-invasive impact on morphological state of tissue cells-targets of representatives of cat family
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