Rib-penetrating focusing sound field construction method for arrhythmia treatment

Abstract

The invention provides a construction method of a rib-penetrating focusing sound field for arrhythmia treatment, and the method comprises the steps: designing a radial phase modulation disc, guiding sound waves emitted by a plane piston transducer to be transmitted along a preset bent concave track, and enabling the sound waves to penetrate through rib gaps to form focusing at a cardiac sinus node, the arrhythmia can be treated by utilizing the mechanical effect to stimulate the sinus node. Based on the size of the human body heart sinus node, the distance between the human body heart sinus node and ribs and the distance between the edges of the ribs, the upper end point height of a track and the actual sound field focal length are obtained through diffraction limit analysis, the curved sound field track is optimized through interpolation, a radial phase function is designed through a caustics method, and a phase modulation disc is manufactured. Concave track bending modulation of sound waves output by the plane piston transducer is achieved, and safe and effective ultrasonic stimulation is provided for arrhythmia treatment. A complex phase control system is not needed, the constructed sound field is not hindered by ribs, and the method has the advantages of being high in energy utilization rate, accurate in focus positioning and accurate and controllable in focus sound pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of medical ultrasound and arrhythmia treatment, and in particular to a method for constructing a trans-rib focused sound field that can be used for arrhythmia treatment, belonging to the field of medical ultrasound treatment. Technical Background

[0002] The increasing incidence of arrhythmias has attracted widespread attention. Currently, the main treatments for arrhythmias include drug therapy, implantable cardioverter devices, catheter ablation, and surgical treatment. These treatments are highly invasive or have unstable therapeutic effects. Ultrasound is non-invasive and can be generated from outside the body, propagating through human tissue to the target area. It stimulates biological tissues through the mechanical effects of ultrasound and has the advantages of being radiation-free and easy to operate. The miniaturization of ultrasound instruments can be designed into portable or wearable devices, which have broad application prospects. Studies have shown that the mechanical effects of ultrasound propagating in tissues exert acoustic radiation forces on tissues, which can activate mechanically sensitive ion channels on cell membranes, change the cell's potential, and regulate electrophysiological activities, providing feasibility for non-invasive treatment of arrhythmias.

[0003] The focused acoustic field has the advantages of concentrated energy, precise positioning, and significant mechanical effects. Short-term irradiation can achieve effective and precise cardiac stimulation without damaging surrounding tissues, and can be used for in vitro ultrasound treatment of arrhythmias. However, the ribs in front of the heart will block and scatter the incident sound beam, reducing the accuracy and energy of the sound field focusing. At the same time, the thermal effect of the sound waves scattered by the ribs may also cause thermal damage. So far, there have been no studies or reports on the use of transducers to emit sound waves from outside the body to directly stimulate the human heart. Therefore, how to modulate the output sound waves of the transducer to construct a concave trajectory curved sound field, and accurately focus it at a specified position in the heart after passing through the rib gap, is the key to the non-invasive treatment of arrhythmias with focused ultrasound. Summary of the Invention

[0004] In order to solve the problem of ribs blocking and scattering sound waves when the current sound field is focused on the cardiac sinoatrial node area, the present invention proposes a method for constructing a trans-rib focused sound field that can be used for arrhythmia treatment. First, the propagation characteristics of two axially symmetrically distributed concave improved curved sound beams when focused are studied. The diffraction limit of the sound field is calculated based on the upper endpoint of the trajectory and the rib edge, the actual focal length of the sound field is obtained, and the height of the upper endpoint of the sound field design is determined. Then, based on the set upper endpoint of the trajectory and the midline of the rib edge, a variable interpolation point is set with an offset to the sound axis. A concave trajectory function is constructed using a quadratic polynomial. A one-dimensional phase modulation structure is designed using the caustic method. The concave trajectory curved sound beam is constructed by phase modulation of the line sound source. Furthermore, a phase modulation disk is designed and manufactured by rotating the one-dimensional phase modulation structure around the axis. The sound waves output by the planar piston transducer are radially bent and modulated to construct a trans-rib focused sound field. The influence of the sound beam trajectory on the focal range of the sound field is analyzed. Results show that the focal length, axial length, and radius of the acoustic field decrease with increasing transducer radius, but an excessively large radius increases the axial sidelobe peak. For a transducer with a fixed radius, increasing the interpolation point offset decreases the axial length of the focal field and increases the peak sound pressure gain, while the focal length initially increases and then decreases. Therefore, the interpolation point position is adjusted so that the acoustic beam emitted from the transducer edge and the concave trajectory curved beam intersect at the rib edge, forming a focal field that completely covers the sinoatrial node region, with the smallest size and the highest gain, ensuring the safety and effectiveness of focused ultrasound therapy for arrhythmias. Finally, the interpolation point is optimized based on the location and size of the sinoatrial node region to achieve focal location, and the excitation sound pressure is adjusted based on the peak sound pressure gain to obtain the acoustic field parameters that meet the requirements for arrhythmia treatment.

[0005] This invention uses a phase modulation disk to phase-modulate the sound waves output by a planar transducer. This guides the sound waves emitted by a radial sound source along a pre-set concave trajectory, forming a conical sound field that passes through the intercostal space and focuses on the heart's sinoatrial node. This mechanical effect precisely stimulates the heart, restoring normal heart rhythm and achieving arrhythmia treatment. This system has a simple structure, is easily controlled, and does not require surgical implantation. It also avoids the influence of ribs on sound propagation and focusing, providing a practical technology for treating arrhythmias.

[0006] A method for constructing a trans-rib focused acoustic field that can be used for arrhythmia treatment includes the following specific steps:

[0007] S1. Based on the size of the human heart's sinoatrial node and its distance from the ribs, as well as the spacing between the rib edges, calculate the diffraction-limited point of the focused sound field and the distance from the upper endpoint of the trajectory to the ribs. Based on the inclination angle between the upper endpoint of the trajectory and the rib edge, obtain the height of the upper endpoint of the trajectory when the maximum diffraction-limited distance is formed.

[0008] S2. A trajectory offset is introduced to the acoustic axis at the midpoint of the line connecting the upper endpoint of the set trajectory and the rib edge point. The function expression of the concave trajectory curved sound beam is constructed using the interpolation method. The one-dimensional phase modulation function is designed through the caustic method, and the corresponding phase modulation structure is prepared to realize phase modulation of the line sound source, thereby constructing a shape-controllable concave trajectory curved sound beam.

[0009] S3. By rotating a one-dimensional phase modulation structure and manufacturing a phase modulation disk, the sound waves emitted by the circular planar piston transducer at different azimuth angles are radially phase modulated. The concave trajectory sound beam distributed in a ring around the acoustic axis forms a conical sound field, passes through the intercostal space and converges toward the acoustic axis, forming a focus in the sinoatrial node area of the heart behind the ribs.

[0010] S4. To ensure the safety and effectiveness of ultrasound in arrhythmia treatment, the trajectory of the sound beam is optimized by adjusting the trajectory offset based on the upper endpoint of the trajectory, the intercostal space, and the distance between the transducer and the ribs, so as to construct a focused sound field with a focal area covering the sinoatrial node, the shortest axial length, and the highest peak sound pressure gain.

[0011] S5. Establish a trans-rib focused sound field construction and measurement system that can be used for arrhythmia treatment, conduct three-dimensional scanning measurement of the sound field, and reconstruct the sound pressure distribution of the sound field; further verify and carry out potential signal simulation using the cardiac potential change model to prove the feasibility of using the trans-rib focused sound field for arrhythmia treatment.

[0012] Specifically, first, in step S1, a human heart model is established, and based on the diffraction limit theory, the height of the upper endpoint of the trajectory corresponding to the maximum diffraction limit height (focal length) is calculated, as follows:

[0013] According to the physiological structure of the human body, the heart's sinoatrial node is the pacemaker of the automatic rhythm, responsible for controlling the rhythmic contraction of the heart. It is located between the second and third ribs, is about 2 cm long, and the distance between the lower end and the rib surface is about 2 cm. In the trans-rib focused sound field design of the present invention, the inter-rib gap 2d1 is 1-2 cm, with an average of 1.5 cm. The sound field focus is located in the sinoatrial node area, and its depth z below the rib is 1.5 cm. d The range is 1-3cm, with an average of 2cm.

[0014] The -3dB beamwidth of the concave trajectory curved sound beam formed by phase modulation is w. The two curved sound beams are symmetrically distributed about the acoustic axis and incident obliquely from the edge of the rib. The height from the upper end point P of the trajectory to the edge of the rib is h, and the incident angle of the sound beam at the edge of the rib is angle α. The actual focused sound field will form a diffraction-limited focal spot at F below P, which is the actual focal range of the sound field z. d , its horizontal width is w / (2cosα), the height of the end point P on the trajectory is h=d1tanα, and the distance between P and F is h1=w·sinα / (4·cos 2α), the focal length relative to the rib is z d =h-h1, which is determined by the width of the sound beam and the tilt characteristics of the curved trajectory. When two sound beams with a width of w are focused, the actual focal length z of the sound field is d As α increases, it first increases and then decreases, and the maximum focal length z is obtained. dmax The height h of the endpoint P on the trajectory d , and use this to design a concave trajectory curved sound beam.

[0015] Then, in step S2, quadratic polynomial interpolation is introduced to establish a concave trajectory function, and a one-dimensional phase modulation structure is designed by using the caustics method to modulate the one-dimensional line sound source to construct a shape-controllable concave trajectory curved sound beam, as follows:

[0016] Considering the difference in thickness of muscle tissue, skin and subcutaneous fat, a propagation matching layer with a distance d is designed between the transducer and the ribs. The actual trajectory upper endpoint height and focal length relative to the transducer surface are h+d and z respectively. d +d. Introduce the trajectory offset ε, add an interpolation point (d1 / 2-ε / 2,h / 2+d-ε / 2) between the trajectory endpoint P and the rib edge point, and obtain the curve equation z=ax through quadratic polynomial interpolation. 2 -bx+c, where a>0, b>0, and c>0, a and b are related to ε, and c=h+d. Results show that z decreases monotonically with increasing x, and its slope distribution ensures the uniqueness and feasibility of line source modulation. The design requires ε>0 and -b / 2a>d1. Under fixed d, d1, and h conditions, adjusting ε can change the shape of the concave trajectory beam. As ε increases, the trajectory becomes more curved, and the closer the curved beam is to the z-axis, the smaller the focal length of the actual sound field.

[0017] The caustic method is used to phase modulate the line sound source located on the +x axis, so that the sound waves emitted from each point on the sound source propagate along the tangent direction of the designed concave trajectory curve. The envelope trajectory formed by a series of rays emitted from each point of the one-dimensional line sound source satisfies z=ax 2 -bx+c, the phase distribution function φ(x) of the line sound source satisfies:

[0018]

[0019] Where k0 is the wave number of the sound wave, θ is the angle between the tangent and +x. In order to ensure the modulatability and uniqueness of the one-dimensional sound source phase φ(x), the concave trajectory curve z=ax 2 In -bx+c, z decreases monotonically as x increases, and the extreme range of θ increases from 90° to 180°, and the corresponding slope increases from -∞ to 0.

[0020] Integrate the above formula to construct z=ax 2The phase distribution function φ(x) required by the one-dimensional line sound source at -bx+c is converted into a one-dimensional phase modulation structure realized by material height. The structural height at x is:

[0021]

[0022] where c0 and c s are the sound speeds of the surrounding medium and the material used to make the phase modulation structure, respectively, and f is the frequency of the sound wave.

[0023] Furthermore, in step S3, a phase modulation disk is designed and manufactured by rotating a one-dimensional phase modulation structure to perform radial phase modulation on the sound waves output by the circular transducer. The sound beam is curved with a concave trajectory that converges toward the acoustic axis and forms a conical sound field. The sound beam passes through the intercostal space and is focused on the sinoatrial node region of the heart. Specifically,

[0024] The above-mentioned one-dimensional phase modulation structure is rotated along the acoustic axis, and a phase modulation disk is designed and manufactured. It is then coaxially mounted on a circular planar piston transducer. The radial line sound source at different azimuth angles of the transducer is phase modulated. The concave trajectory distributed annularly around the acoustic axis bends the sound beam to form a conical sound field, which passes through the intercostal space and converges toward the acoustic axis, and is focused in the cardiac sinoatrial node area behind the ribs.

[0025] Finally, based on the trajectory endpoint height h, the rib gap d1, and the distance d between the transducer and the ribs, the trajectory offset ε is adjusted to optimize the sound field trajectory, constructing a focused sound field with a focal area covering the sinoatrial node, an axial length as short as possible, and a peak sound pressure gain as high as possible, as follows:

[0026] When h, d, d1, and ε are fixed, as the transducer radius R increases, the axial and radial dimensions of the focal zone decrease, and the peak sound pressure gain increases, but the focus moves closer to the ribs and produces significant side lobes. This design requires R < 60 mm.

[0027] By adjusting the concave trajectory shape by keeping R, h, d, and d1 fixed and varying ε, the results show that as ε increases, the focal peak sound pressure gain increases monotonically, the focal axial length decreases monotonically, and the focal length of the sound field first increases and then decreases. Therefore, to construct a trans-rib focused sound field with the highest focal peak sound pressure gain and the smallest focal axial length, ε is determined by the human body structure and transducer position parameters h, d, and d1 in the system. It is generally selected between 0 and 2.6 mm to optimize the focused sound field.

[0028] Under the conditions of fixed R, h and d1, adjust ε and d to optimize the design, and the relevant parameters of the curve meet d=(2d1 2 -2d1R)a+(d1-R)b, a=2ε(d1+h) / [d1·(d1 2 -ε 2 )] and b=-(2d12 ε+hd1 2 +2hd1ε-hε 2 ) / [d1·(d1 2 -ε 2 )], the slope of the concavely curved beam at the rib edge is the same as the slope of the line connecting the transducer edge and the rib edge. Therefore, adjusting ε makes the designed concavely curved beam tangent to the line connecting the transducer edge and the rib edge at the rib edge. At this point, the sound waves emitted by the transducer, after phase modulation, can fully pass through the intercostal space. The constructed sound field focal zone can cover the sinus node area, forming a trans-rib focused sound field with the smallest size and the highest sound pressure gain.

[0029] Finally, step S5 establishes a trans-rib focused acoustic field construction and measurement system for arrhythmia treatment and therapeutic efficacy simulation based on a cardiac potential variation model. The system includes a computer A, a function signal generator B, a power amplifier C, a hydrophone, a preamplifier D, a filter E, an oscilloscope F, a three-dimensional translation stage G, a planar piston transducer, a phase modulation disk structure, and a water tank. The planar piston transducer is sequentially connected to the power amplifier and the function signal generator. The function signal generator outputs a single-frequency sinusoidal signal, which is amplified by the power amplifier and drives the planar piston transducer to emit sound waves. The phase modulation disk structure is coaxially and tightly mounted on the surface of the planar piston transducer, and the output sound waves are subjected to concave trajectory phase modulation to construct a trans-rib focused acoustic field. The hydrophone is mounted on a three-dimensional translation stage and sequentially connected to the preamplifier, filter, oscilloscope, and computer to perform three-dimensional scanning measurement of the sound field, signal acquisition, and sound field reconstruction. Furthermore, the cardiac potential variation model is used to verify the potential signal simulation, demonstrating the feasibility of trans-rib focused ultrasound for arrhythmia treatment.

[0030] The present invention adopts the above technical solution, and the rib-penetrating focused sound field constructed has the following advantages:

[0031] The present invention uses a phase modulation disk to phase-modulate the sound waves output by a planar piston transducer. This guides the sound waves emitted by a radial sound source along a pre-set concave curved trajectory, passing through the intercostal spaces and focusing them in the heart's sinoatrial node region. This mechanical effect precisely stimulates the heart, restoring normal cardiac rhythm and achieving arrhythmia treatment. This invention eliminates the need for a complex phase-controlled system, offering advantages such as a simple structure and easy control. It also eliminates the need for surgical implantation and avoids the effects of ribs on sound propagation and focusing, providing a practical technology for treating arrhythmias. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 .Using phase modulation of circular planar piston transducer to construct transcostal focusing for arrhythmia treatment

[0033] Sound field diagram.

[0034] Figure 2 . Schematic diagram of the construction of a concave trajectory through-rib focused sound field based on phase modulation of symmetrically distributed line sound sources.

[0035] Figure 3 .Simulation results of the through-rib focused acoustic field based on radial phase modulation of the phase modulation disk.

[0036] Figure 4 The beam width w is equal to the diffraction-limited height (focal length) z at wavelength λ. d The relationship with the angle α. Figure 5 (a) The upper and lower endpoints of the focal area and the depth of the focus into the ribs, and (b) the local

[0037] Amplified results, (c) focal zone axial length and (d) peak sound pressure gain curves varying with ε.

[0038] Figure 6 .(a) Sound pressure diagram of the axial section and (b) normalized axial sound pressure distribution of the through-rib focused sound field when ε=2.41 mm.

[0039] Figure 7 Diagram and photo of the sound field construction and measurement system, where A: computer, B: signal source, C: power amplifier

[0040] D: preamplifier, E: filter, F: oscilloscope, G: three-dimensional moving stage.

[0041] Figure 8 Axial cross-sectional sound pressure diagram of the focused sound field through the ribs under (a) free field and (b) rib obstacle conditions, (c) no ribs

[0042] Simulation and experimental results of the normalized axial sound pressure distribution under bone conditions, (d) axial normalized sound pressure distribution before and after rib placement.

[0043] Figure 9 .Potential distribution of the cross section of the sinoatrial node region during heartbeat, (a) Potential distribution in the resting state, myocardium

[0044] The cells are in diastole. (b)-(d) The sinoatrial node sends electrical impulses to the outer cells, causing myocardial contraction. (e) Abnormal depolarization of cells in some regions, resulting in erroneous cell potential distribution. (f) Asymmetric propagation of action potentials in regions in the refractory period. (g) Formation of the spiral wave nucleus. (h) Formation of the spiral wave. Starting at 1000 ms, a transcostal focused acoustic field is applied to the sinoatrial node region at a repetition rate of 10 Hz and a duration of 0.5 ms. (i)-(k) The process of expelling the spiral wave. (l) After the tenth stimulation, the spiral wave is expelled from the tissue boundary, and normal heartbeat is restored. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0046] Example: Figure 1 As shown, the focused transducer used in this example has a radius of R = 50 mm, a center frequency of f = 1 MHz, and the filling medium around the transducer is water, whose sound velocity is c0 = 1500 m / s and density is ρ0 = 1000 kg / m 3 The speed of sound and density of human soft tissue are similar to those of water. The phase modulation disk is made of white resin material 3D printing, and its speed of sound is c s =2313.6m / s, density is ρ s =1050kg / m 3 . Establish as Figure 2 The relative position model of the heart, ribs and symmetrically distributed linear array transducers shown in the figure assumes that the intercostal gap below the heart is 2d1 = 1.5 cm, d1 is the half-width of the gap between the two ribs, the lower end point of the sinoatrial node area is located 2 cm above the outer surface of the ribs, and the length of the sinoatrial node area is 2 cm.

[0047] Based on the above transducer parameters and related positions, calculate the diffraction limit point (actual focus) z d The relationship between the endpoint height h on the trajectory and the incident tilt angle α of the rib edge is used to obtain the endpoint height h on the trajectory when the diffraction limit height is maximum. d The offset ε was adjusted so that the sound line emitted from the edge of the transducer and the designed concave trajectory were tangent to the edge point of the rib. A concave trajectory bending beam function was established, and a phase modulation disk was designed to phase modulate the sound waves emitted by the planar piston transducer. A trans-rib focused sound field was constructed, and the position and size of the focal area of the sound field as well as the peak sound pressure gain were measured. Finally, a cardiac potential change model was used to simulate the potential signal, demonstrating the feasibility of the designed trans-rib focused ultrasound for arrhythmia treatment.

[0048] The specific implementation steps are as follows:

[0049] (1) Figure 2 As shown, the height z of the diffraction-limited point F relative to the rib is set d =h-h1, the height of the end point P on the trajectory is h=d1tanα, and the distance between P and F is h1=w·sinα / (4·cos 2 α). For an actual curved acoustic beam, its beam width w is generally greater than the wavelength λ. Under the condition of a fixed α, when w = λ, z is obtained. d Maximum value. Further, set w = λ and calculate z d The corresponding α at the maximum and its corresponding height z dmaxUnder the conditions of f = 1MHz and λ = 1.5mm, we get Figure 4 Shown d The relationship curve between z and α shows d As α increases, it first increases and then decreases. When α = 1.47 rad, the diffraction limit height reaches its maximum value z dmax =37.3mm, the height of point P is h d =d1 tanα=74.8mm; When α increases further, due to the corresponding increase of w / (2cosα), z d Therefore, in subsequent designs, h was fixed at 74.8 mm.

[0050] (2) Figure 2 As shown, the center offset ε is set under the condition of h = 74.8 mm, and the curve equation of the concave trajectory z = ax is constructed by quadratic polynomial interpolation based on the rib and line sound source positions. 2 -bx+c, where a>0, b>0, c>0, x<0, a and b are related to ε, and c=h+d. A one-dimensional phase modulation structure is designed by the caustic method, and a phase modulation disk is designed and manufactured by rotation. It is coaxially mounted on a circular planar piston transducer. The radial line sound source at different azimuth angles of the circular planar piston transducer is subjected to concave trajectory bending phase modulation to form a conical sound field, which is focused behind the ribs. The results are shown in the figure. Figure 3 shown.

[0051] (3) Trajectory curve z = ax 2 In -bx+c, the parameters a, b, c, and d are all functions of ε, where a = 2ε(d1+h) / (d1·(d1 2 -ε 2 )), b=-(2d1 2 ε+hd1 2 +2hd1ε-hε 2 ) / (d1·(d1 2 -ε 2 )), c=h+d, d=(2d1 2 -2d1R)a+(d1-R)b, adjust ε to simulate the sound field to obtain the sound pressure distribution of the rib-penetrating focused sound field, and obtain the following Figure 5The upper and lower endpoints of the focal zone's axial half-height width, as well as the depth of the focal point into the ribs, the focal zone's axial length, and the peak sound pressure gain are shown as a function of ε. The results show that when ε ≥ 2.6 mm, the axial sidelobe peak exceeds half the mainlobe peak, and part of its width must be included in the focal zone's axial length. Therefore, the focal zone's axial length no longer decreases, and the peak sound pressure gain actually decreases. Therefore, ε should be appropriately set within the range of 0-2.6 mm. Based on the cardiac sinoatrial node region, the relative position of the transducer and the ribs, the minimum and maximum depths of the sinoatrial node behind the ribs are 20 and 40 mm, respectively. Therefore, the depth of the lower endpoint of the focused sound field into the ribs is less than 20 mm. When ε is less than 2.41 mm, the upper endpoint distance of the focal zone is greater than 40 mm, and the focal zone covers the sinoatrial node region, meeting the sound field design requirements. Further increasing ε slightly reduces the sound field size and slightly increases the peak sound pressure, but the upper endpoint distance is less than 40 mm, and the focal zone's range of influence deviates from the sinoatrial node region. Therefore, ε=2.41 mm is selected. At this time, the distance between the upper end points of the focal area is equal to 40 mm, the axial length of the focal area is minimized, and the peak sound pressure gain is maximized, thus obtaining an optimized design solution.

[0052] Under the above conditions, the function expression of the concave trajectory sound beam is z = 1048.6x 2 -17.8x+0.1644, when the sound pressure on the transducer surface is 45kPa, the simulation results are as follows Figure 6 The trans-rib focused sound field is shown. At this time, ε = 2.41 mm, d = 89.64 mm, and the depth of the focus into the rib is z d =27.36mm, the axial length of the focal area is 25.4mm, and the peak sound pressure gain is 22.35. The position of the focal area of the sound field and the peak sound pressure fully meet the needs of arrhythmia treatment.

[0053] (4) The caustic method is used to calculate the phase of the concave trajectory curved sound beam designed under the condition of ε = 2.41 mm, and a phase modulation disk is designed and manufactured by 3D printing. Figure 7The system shown here can be used to construct and measure a transrib focused acoustic field for arrhythmia treatment. The system includes a computer A, a function signal generator B, a power amplifier C, a hydrophone, a preamplifier D, a filter E, an oscilloscope F, a three-dimensional translation stage G, a planar piston transducer, a phase-modulation disk structure, and a water tank. The planar piston transducer is sequentially connected to the power amplifier and the function signal generator. The function signal generator outputs a single-frequency sinusoidal signal, which, after amplification by the power amplifier, drives the planar piston transducer to emit sound waves. The phase-modulation disk structure is coaxially and tightly mounted on the surface of the planar piston transducer, applying concave phase modulation to the output sound waves to construct a transrib focused acoustic field. The hydrophone is mounted on a three-dimensional translation stage and sequentially connected to the preamplifier, filter, oscilloscope, and computer to perform three-dimensional scanning measurement of the sound field, signal acquisition, and sound field reconstruction. Under the condition of no ribs, the free sound field was scanned and measured in the range of 44<z<144mm in the axial direction and -20≤x≤20mm in the radial direction with a step of 0.5mm. Further, with ribs as obstacles, the sound field was scanned and measured in the range of 104<z<144mm in the axial direction and -20≤x≤20mm in the radial direction. The results are as follows: Figure 8 (a) and 8(b), the normalized axial sound pressure distributions of the simulated and experimental measurements under experimental conditions are shown in Figure 8 As shown in (c), the normalized sound pressure distribution before and after the ribs are set is as follows: Figure 8 (d) The experimental results show that the ribs have almost no effect on the designed concave track focused sound field, and the focal position, focal area size, and peak sound pressure remain almost unchanged. This proves that the designed concave track focused sound field has good rib penetration characteristics and can ensure good focus in the sinus node area.

[0054] (5) Based on the cardiac potential change model, potential signal simulation was carried out to prove the feasibility of arrhythmia treatment. The myocardial cell was idealized as a cylinder with a bottom radius of 7.5 μm and a height of 80 μm. The Piezo1 channel on the myocardial cell membrane is an ion channel that opens when stimulated by mechanical force. It can convert mechanical stimulation into physiological electrical signals and thus affect cell activity. The peak sound pressure at the focus of the focused sound field was controlled to be 1.23 MPa, and the sodium ion (Na + ), potassium ion (K + ) and calcium ions (Ca 2+ The cardiac potential change model of the influence of ) channels and Piezo1 channels on cell potential simulates the process of focusing sound field to treat arrhythmia. The results are as follows Figure 9As shown in the figure, initially, cells are at a resting potential (diastolic), and the sinoatrial node normally emits electrical impulses. However, when myocardial tissue is partially damaged or fibrotic, the electrophysiological properties of the myocardial cells in the abnormal area change, leading to abnormal depolarization and erroneous cell potentials. This in turn causes irregular propagation of the electrical signal wavefront, ultimately leading to the generation of spiral waves. Once spiral waves appear in the myocardial tissue, they quickly replace the electrical impulses emitted by the sinoatrial node, causing rapid contraction and relaxation of myocardial cells, a significant increase in heart rate to approximately 400 bpm, and the onset of arrhythmia. Starting at 1000 ms, a focused acoustic field delivers 0.5 ms ultrasonic pulses at a 10 Hz repetition rate to the sinoatrial node region, aiming to drive the spiral waves beyond the boundaries of the cardiac tissue. After the tenth stimulation, the generated action potential permeates the entire myocardial tissue. At this point, cessation of the focused acoustic field stimulation allows the electrical impulses emitted by the sinoatrial node to resume control of the heartbeat, eliminating the arrhythmia.

[0055] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0056] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for constructing a trans-rib focused acoustic field for arrhythmia treatment, characterized in that: The following steps are involved: S1. Based on the size of the human heart's sinoatrial node and its distance from the ribs, as well as the spacing between the rib edges, calculate the height of the diffraction-limited point of the focused sound field and the distance between the upper endpoint of the trajectory and the ribs. Based on the inclination angle between the upper endpoint of the trajectory and the rib edge, calculate the height of the upper endpoint of the trajectory when the maximum diffraction-limited distance is achieved. S2. A trajectory offset is introduced to the acoustic axis at the midpoint of the line connecting the upper endpoint of the set trajectory and the rib edge point. A concave trajectory bending function is constructed using the interpolation method. A one-dimensional phase modulation function is designed using the caustics method. Phase modulation of the line sound source is achieved through the corresponding phase modulation structure, thus constructing a shape-controllable concave trajectory bending beam. S3. A phase modulation disk is designed by rotating a one-dimensional phase modulation structure to radially phase modulate the sound waves emitted at different azimuth angles by the circular planar piston transducer. The concave trajectory sound beam distributed annularly around the acoustic axis passes through the intercostal space and converges toward the acoustic axis, forming a focus in the sinoatrial node area behind the ribs. S4. Based on the upper endpoint of the trajectory, the intercostal space, and the distance between the transducer and the ribs, the trajectory offset is adjusted to optimize the sound field trajectory, constructing a focused sound field with a focal area covering the sinoatrial node, the shortest axial length, and the highest peak sound pressure gain; S5. Establish a trans-rib focused sound field construction and measurement system that can be used for arrhythmia treatment, conduct three-dimensional scanning measurement of the sound field, and reconstruct the sound pressure distribution of the sound field; further verify and carry out potential signal simulation using the cardiac potential change model to prove the feasibility of using the trans-rib focused sound field for auxiliary treatment of arrhythmias.

2. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S1, the heart's sinoatrial node is the pacemaker of the automatic rhythm, responsible for controlling the rhythmic contraction of the heart. It is located between the second and third ribs. In the trans-rib focused sound field design, the rib gap 2d1 is 1-2 cm, with an average of 1.5 cm. d1 is the half-width of the gap between the two ribs. The sound field focus is located in the sinoatrial node area, and its depth z below the ribs is 1.5 cm. d The range is 1-3cm, with an average of 2cm.

3. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S1, the -3dB beam width of the curved sound beam formed by phase modulation is set to w, and the two curved sound beams symmetrically distributed about the acoustic axis are incident obliquely from the edge of the rib. The height from the endpoint P on the trajectory to the edge of the rib is h, and the incident angle of the sound beam on the edge of the rib is the angle α. The actual focused sound field will form a diffraction-limited focal spot at F below P, which is the actual focus. Its lateral width is w / (2cosα). The height of the endpoint P on the trajectory at this time is h=d1 tanα, and the distance between P and F is h1=w·sinα / (4·cos 2 α), the actual focal length relative to the rib is z d =h-h1.

4. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S1, for a fixed sound beam w, the actual focal length z of the sound field d As α increases, it first increases and then decreases, and the maximum focal length z is obtained. dmax The height h of the endpoint P on the trajectory d , and use this to design the concave trajectory curved sound field.

5. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S2, a propagation matching layer with a distance d is designed between the transducer and the rib, and the actual trajectory end point height and focal length relative to the transducer surface are obtained as h+d and z respectively. d +d.

6. The method for constructing a trans-rib focused acoustic field for treating arrhythmia according to claim 1, characterized in that: In step S2, the trajectory offset ε is introduced, and an interpolation point (d1 / 2-ε / 2, h / 2+d-ε / 2) is added between the trajectory endpoint P and the rib edge point. The concave trajectory curve equation z=ax is obtained by quadratic polynomial interpolation. 2 -bx+c, where a>0, b>0, c>0, a and b are related to ε, and c=h+d, z decreases monotonically with increasing x. Its slope distribution ensures the uniqueness and feasibility of line source modulation, requiring ε>0 and -b / 2a>d1; The caustic method is used to phase modulate the line sound source located on the +x axis, so that the sound waves emitted from each point on the sound source propagate along the tangent direction of the designed concave trajectory curve. The envelope trajectory formed by a series of rays emitted from each point of the sound source satisfies z=ax 2 -bx+c, we get the phase distribution function φ(x) of the line sound source, which satisfies: Where k0 is the wave number of the sound wave, θ is the angle between the tangent and +x, and in order to ensure the modulatability and uniqueness of the one-dimensional line sound source phase φ(x), the concave trajectory curve z decreases monotonically with the increase of x, and the extreme range of θ increases from 90° to 180°, and its corresponding slope increases from -∞ to 0; By integrating the above formula, we can construct the curve z=ax 2 The phase distribution function φ(x) required by the sound source at -bx+c is converted into a one-dimensional phase modulation structure realized by the material height. The structural height at x is: where c0 and c s are the sound speeds of the surrounding medium and the material used to make the phase modulation structure, respectively, and f is the frequency of the sound wave.

7. The method for constructing a trans-rib focused acoustic field for treating arrhythmia according to claim 1, characterized in that: In step S3, a one-dimensional phase modulation structure is designed based on the constructed concave trajectory curve equation by using the caustics method to achieve phase modulation of the line sound source and construct a shape-controllable concave trajectory curved sound beam close to the acoustic axis; In step S3, the one-dimensional phase modulation structure is rotated along the acoustic axis, and a phase modulation disk is designed to perform phase modulation on the radial line sound source at different azimuth angles of the circular planar piston transducer. The concave trajectory distributed in a ring around the acoustic axis bends the sound beam to form a conical sound field, which passes through the intercostal space and converges toward the acoustic axis and focuses in the sinoatrial node area of the heart behind the ribs.

8. The method for constructing a trans-rib focused acoustic field for treating arrhythmia according to claim 1, characterized in that: In step S4, when h, d, d1 and ε are fixed, as the transducer radius R increases, the axial and radial dimensions of the focal area decrease, and the sound pressure gain increases. When R is less than 60 mm, a sound field that meets the requirements can be generated. In step S4, R, h, d and d1 are fixed, and ε is changed to adjust the shape of the curved trajectory. It is found that as ε increases, the focal peak sound pressure gain increases monotonically, the focal axial length decreases monotonically, and the sound field focal length first increases and then decreases, requiring 0<ε<2.6mm.

9. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S4, R, h and d1 are fixed, and the relationship between ε and d is adjusted to satisfy d = (2d1 2 - 2d1R)a+(d1 - R)b, a = 2ε(d1 + h) / [d1·(d1 2 - ε 2 )] and b=-(2d1 2 ε+hd1 2 +2hd1ε-hε 2 ) / [d1·(d1 2 -ε 2 )], the slope of the designed concave trajectory curved sound beam at the rib edge point is the same as the slope of the line connecting the transducer edge and the rib edge point; In step S4, corresponding to the fixed R, h and d1, ε should be adjusted so that the designed concave trajectory curved sound beam is tangent to the line connecting the transducer edge point and the rib edge point at the rib edge point. At this time, the constructed sound field focal area completely covers the sinoatrial node area, and can ensure that the sound waves emitted by the transducer can completely pass through the rib gap after phase modulation, forming a focused sound field with the smallest size and the highest sound pressure gain, and realizing ultrasonic treatment of arrhythmia through precise and efficient mechanical stimulation of the sinoatrial node.

10. The method for constructing a trans-rib focused acoustic field for arrhythmia treatment according to claim 1, characterized in that: In step S5, a trans-rib focused sound field construction and measurement system that can be used for arrhythmia treatment is established, three-dimensional scanning measurement of the sound field is performed, and the sound pressure distribution of the sound field is reconstructed; further, a cardiac potential change model is used to verify the potential signal simulation and prove the feasibility of the trans-rib focused sound field for auxiliary arrhythmia treatment. The method also includes the following steps: The system includes a computer, a function signal generator, a power amplifier, a hydrophone, a preamplifier, a filter, an oscilloscope, a three-dimensional moving stage, a planar piston transducer, a phase modulation disk structure and a water tank. The planar piston transducer is connected to the power amplifier and the function signal generator in sequence. The function signal generator outputs a single-frequency sinusoidal signal, which is amplified by the power amplifier and drives the planar piston transducer to emit sound waves. The phase modulation disk structure is coaxially and tightly mounted on the surface of the planar piston transducer, and the output sound wave is subjected to concave trajectory phase modulation to construct a rib-penetrating focused sound field. The hydrophone is mounted on the three-dimensional translation stage and connected to the preamplifier, filter, oscilloscope and computer in sequence to carry out three-dimensional scanning measurement of the sound field, signal acquisition and sound field reconstruction.

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