Laser-induced acoustic pressure wave closed-loop precision control method and system for intravascular complex lesions

Abstract

This invention discloses a closed-loop precise control method and system for laser-induced acoustic pressure wave (APW) in complex intravascular lesions. This method belongs to the field of laser medical technology. This application employs a physical model for APW generation coupled with a laser-plasma-liquid medium, and designs an APW simulation calculation and tunable laser control system based on this model. By adjusting parameters such as the wavelength, pulse width, and peak power density of the tunable laser, precise forward control of the generated APW intensity is achieved. Simultaneously, based on the target APW intensity required clinically, the optimal laser parameter combination can be iteratively calculated in reverse, forming a closed-loop design from "treatment target" to "laser parameters." This invention combines a laser physical model with clinical needs, realizing the quantification, predictability, and controllability of APW intensity, providing a precise and intelligent technical solution for the treatment of intravascular calcification. It can significantly simplify physician operations and improve the safety and effectiveness of treatment.

Description

Technical Field

[0001] This invention relates to the field of laser medical technology, and in particular to a laser-induced acoustic pressure wave closed-loop precise control method and system for complex intravascular lesions. Background Technology

[0002] In interventional treatment of severe calcified lesions of the coronary or peripheral arteries, especially when dealing with complex morphologies such as annular calcification, eccentric calcification, or deep calcification, there is an urgent clinical need for a minimally invasive treatment method that can effectively fragment calcified tissue. Acoustic pressure wave (APW) technology offers an innovative solution to this challenge due to its unique mechanical effect. This technology instantaneously generates high-pressure sound waves in the intravascular fluid medium. Utilizing the reflection and transmission of these sound waves at the interface between the calcified tissue and the vessel wall, shear stress is generated, achieving selective fragmentation of the calcified layer while minimizing damage to the more elastic normal vessel wall. This physical characteristic of "selective fragmentation" gives it an irreplaceable advantage in treating complex calcified lesions.

[0003] Currently, the main methods for generating intravascular acoustic pressure waves are arc discharge and laser-induced methods. Arc discharge relies on a microelectrode structure placed within a balloon to generate a shock wave through high-voltage instantaneous discharge in a liquid medium. However, this method is limited by the physical size and integrated structure of the electrode itself—to achieve controllable discharge, the electrode and its encapsulation components must occupy a certain radial and axial space within the balloon, and the discharge gap must be precisely maintained within millimeters. This makes it difficult to further compress the cross-sectional size of the entire transmitting device, hindering its passage through peripheral vessels or distal coronary branches. Furthermore, this method faces challenges in practical applications, including the cumulative electrode wear with each discharge, potential interference with electrophysiological signals affecting intraoperative monitoring, and challenges to the consistency and predictability of acoustic pressure waves due to repetitive fluctuations in energy output. These factors collectively limit its clinical applicability in refined, highly stable vascular interventional scenarios.

[0004] In contrast, laser-induced propagation utilizes pulsed laser light transmitted to the target point via flexible optical fiber. The laser directly penetrates the liquid medium at the fiber's end to generate plasma and produce acoustic pressure waves. Optical fiber itself possesses excellent flexibility, a very small diameter, and good biocompatibility, eliminating the need for existing minimally invasive interventional catheter systems to reach distal, small blood vessels, fundamentally avoiding the rigid constraints of electrode structures on device size. Simultaneously, the wavelength, pulse width, and energy of the laser source can be independently and flexibly controlled. Combined with the efficient transmission characteristics of optical fiber, this results in greater controllability and repeatability of the acoustic pressure wave intensity and spatial distribution. Therefore, laser-induced propagation exhibits significant advantages in terms of adaptability to minimally invasive interventions, flexibility in parameter control, and long-term system stability, making it a more promising technological direction.

[0005] However, existing laser-induced acoustic pressure wave technology still has key shortcomings, which prevent it from fully realizing its potential in practical applications. Specifically: The "uncontrollability" of sound pressure wave intensity and its effect: Current technologies mostly use solid-state lasers with fixed wavelengths, which have limited adjustable parameters. However, the absorption coefficient and penetration depth of the laser in media such as blood or contrast agents directly affect the excitation efficiency of the plasma and the conversion efficiency of the sound pressure wave. Faced with the wide variety of blood vessel diameters (such as coronary arteries and peripheral arteries) and calcified plaques of varying hardness and thickness in clinical practice, laser systems with limited parameters cannot achieve sufficient energy deposition, resulting in insufficient energy for treating some lesions and potentially causing excessive damage to others. This fundamentally limits the universality and safety of its treatment.

[0006] The "imperfections" of the physical process: Current laser parameter settings largely rely on limited experiments, lacking precise physical model guidance. Existing theoretical models (such as the Fabbro model) oversimplify the description of laser energy deposition into plasma, failing to characterize the dynamic evolution of key state parameters such as plasma absorption coefficient, electron density, and energy density. This makes it impossible to establish a precise physical mapping relationship from input laser parameters (such as wavelength, pulse width, and energy) to the output acoustic pressure wave intensity and spatial distribution, rendering the acoustic pressure wave generation process like a "black box," hindering forward prediction and backward design based on physical principles.

[0007] Lack of precision treatment capabilities: Existing technologies are unable to accurately customize and optimize parameters for specific clinical scenarios (such as high-density annular coronary calcification or eccentric peripheral artery calcification), and lack the ability to design intelligent parameters that can respond to different patients and different lesion characteristics, thus failing to achieve truly personalized precision treatment.

[0008] In conclusion, although laser-induced acoustic pressure wave technology has the physical form of minimally invasive intervention, its clinical efficacy has not been fully explored due to the lack of precise control and prediction capabilities over the core physical processes. Summary of the Invention

[0009] Therefore, the purpose of this invention is to provide a laser-induced acoustic pressure wave closed-loop precise control method and system for complex intravascular lesions, aiming to solve the core problem of the inability to precisely control the acoustic pressure wave generation process in the prior art. By establishing a parameterized physical model that couples laser parameters, medium absorption characteristics and plasma dynamics, it achieves for the first time the forward precise control and reverse parameter design of acoustic pressure wave intensity, providing a predictable, controllable and intelligent technical solution for the treatment of intravascular calcification.

[0010] Therefore, the present invention provides a laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions, comprising the following steps: S1. Establish a physical model for the generation of acoustic pressure waves coupled by laser-plasma-liquid media; S2. Obtain the type of complex lesion in the blood vessel and the target acoustic pressure wave intensity; design the reverse acoustic pressure wave parameters of the acoustic pressure wave generation physical model based on the target acoustic pressure wave intensity to obtain the optimal combination of laser parameters; S3. Based on the obtained optimal combination of laser parameters, control the tunable laser to emit laser pulses; S4. Simulate the acoustic pressure wave generation process of laser pulse irradiation into blood vessels and predict the acoustic pressure wave intensity. S5. Obtain the measured sound pressure wave signal and compare the measured sound pressure wave signal with the predicted sound pressure wave intensity in real time. S6. If the difference between the measured sound pressure wave signal and the predicted sound pressure wave intensity exceeds the preset threshold, control the tunable laser to adjust the output laser pulse parameters.

[0011] More preferably, in S1, the process of establishing the physical model for generating acoustic pressure waves via laser-plasma-liquid medium coupling includes: An integral model of plasma energy density was established to simulate the process of laser breaking down a liquid medium to generate plasma and form bubbles. A sub-model of ionization dynamic evolution based on the free electron density rate equation is established, and the free electron density is solved. A time-varying rate equation to characterize the plasma formation process; A sub-model of bubble expansion dynamics based on the Kirkwood-Bethe approximation was established; the energy conversion and pressure transmission process of acoustic pressure waves were simulated. A sub-model for the propagation and attenuation of acoustic pressure waves based on the Tait equation of state was established; the long-distance transmission and attenuation process of acoustic pressure waves in liquid media was simulated.

[0012] More preferably, the plasma energy density integral model includes: Calculate the effective initial energy of the driving sound pressure wave ; When it is a short pulse ; When it is a long pulse ; Where E' is the plasma energy density, Laser waist radius Free electron density as a function of time : Free electron density, ΔE: Ionization energy, M: Mass of medium molecules or atoms, m: Electron mass; Avalanche ionization coefficient; Laser pulse width; : Laser angular frequency.

[0013] More preferably, the ionization dynamic evolution sub-model based on the free electron density rate equation includes: Bubble radius estimation equation ; Equation for bubble pressure and expansion rate: ; Equation of pressure inside the bubble and deposition energy ; ; Where E is the effective initial energy driving the sound pressure wave, and γ is the adiabatic index of the gas or plasma inside the bubble. Laser pulse width; R0: initial radius of the bubble; W mpi For multiphoton ionization rate, g is the avalanche ionization coefficient; g′ is the diffusion loss coefficient; is the composite coefficient.

[0014] More preferably, the expression for the multiphoton ionization rate is: in, Dawson's probability integral: , Laser angular frequency, unit: rad / s; m′: effective electron mass, unit: kg; Reduced Planck constant, 1.0546 × 10⁻⁶ -34 J*s; e: elementary charge; I: laser intensity, unit: W / m 2 ΔE: Ionization energy of the medium; c: Speed ​​of light; : Absorption cross section of the medium molecules for laser light; n: Refractive index of the medium; k: Number of photons required for multiphoton ionization.

[0015] A further preferred embodiment of the Kirkwood-Bethe approximation of bubble expansion dynamics includes: ; Where H: enthalpy, unit: J / kg; t: time, unit: s; c: liquid sound speed, unit: m / s; u=dR / dt: bubble expansion velocity, unit: m / s; R: instantaneous radius of bubble, unit: m.

[0016] More preferably, the acoustic pressure wave propagation and attenuation sub-model based on the Tait state equation includes: Calculate the attenuation relationship of peak pressure p(r,t) as a function of distance r and time t when a sound pressure wave propagates in a liquid: Wherein, the pressure correction factor θ and the nonlinear attenuation factor g are defined as follows: ; in: : Pressure correction factor, c: Liquid sound velocity; R0: Initial radius of bubble; r: Propagation distance; p1: Internal pressure of bubble; t: Time.

[0017] Furthermore, the mapping relationships of the sub-models in the physical model for generating acoustic pressure waves by coupling laser-plasma-liquid media together constitute a complete forward computational chain: for a given laser parameter The acoustic pressure wave intensity p is obtained by calculating the forward calculation link (τ, I).

[0018] More preferably, in S2, the sound pressure wave generation physical model is designed with inverse sound pressure wave parameters based on the target sound pressure wave intensity; this includes solving the constraint optimization equations shown in the following formula in reverse, using a particle swarm optimization algorithm based on the mapping relationship of each sub-model: Optimization equation: The constraints are: Where, p target To achieve the target sound pressure wave intensity required for clinical use, (λ) min , λ max ), , I max These represent the adjustable ranges of wavelength, pulse width, and peak power density of the tunable laser, respectively.

[0019] This application also provides a laser-induced acoustic pressure wave closed-loop precision control system for complex intravascular lesions, which includes the following steps for implementing the above-mentioned acoustic pressure wave closed-loop precision control method: a computer, a tunable light source, and a pulse width adjustment module, a homogenization coupling device, an optical fiber, and an acoustic wave detector arranged sequentially after the tunable light source. The computer is equipped with a multi-physics coupling modeling module, a forward laser parameter control module, a reverse acoustic pressure wave parameter design module, a full-chain acoustic pressure wave generation simulation module, and a closed-loop feedback adaptive therapy module. The multiphysics coupling modeling module is used to establish a physical model for the generation of acoustic pressure waves coupled with laser-plasma-liquid medium. It dynamically describes the ionization, avalanche, diffusion and recombination processes by solving the free electron density rate equation, and accurately calculates the effective energy deposition using the plasma energy density integral method. Combined with the bubble expansion dynamics and acoustic pressure wave propagation model, it realizes the simulation of the entire process from laser incident to acoustic pressure wave output. The forward laser parameter control module is used to predict the intensity, spatial distribution and range of sound pressure waves under different parameter combinations by adjusting one or more parameters of the wavelength, pulse width or peak power density of the tunable laser source based on the multiphysics model, thereby achieving active, repeatable and precise control of the sound pressure wave output. The reverse acoustic pressure wave parameter design module is used to solve the optimal combination of laser wavelength, pulse width and energy using a numerical optimization algorithm based on the target acoustic pressure wave intensity required in clinical practice. This establishes a calculable mapping relationship from the treatment target to the laser parameters, enabling the automated generation of laser parameters for personalized treatment. The full-chain acoustic pressure wave generation simulation module is used to solve the sub-models in the acoustic pressure wave generation physical model simultaneously, providing a systematic acoustic pressure wave generation simulation capability for coupled laser plasma liquid media. The closed-loop feedback adaptive treatment module is used to integrate a sound wave detector into the treatment system to collect sound pressure wave signals in real time, run a real-time control algorithm to compare the measured values ​​with the model prediction values, and dynamically adjust the wavelength, pulse width or energy parameters of the laser according to the deviation, so as to realize online monitoring, feedback and adaptive adjustment, thereby improving the safety and effectiveness of treatment of complex intravascular lesions.

[0020] The laser-induced acoustic pressure wave closed-loop precise control method and system for complex intravascular lesions disclosed in this application have at least the following advantages compared to the prior art: The coupled laser-plasma-liquid medium coupling acoustic pressure wave generation physical model provided in this application improves the accurate calculation method of plasma absorption energy based on traditional energy distribution methods. By introducing key modules such as plasma energy density integral, free electron density evolution rate equation, and multiphoton ionization rate, it achieves accurate simulation of the entire process from laser energy input to shock wave pressure field distribution. As the core functional module of the system, this model is integrated into the front-end computer control system. It can predict the acoustic pressure wave intensity and attenuation characteristics under different plaque lesion types based on the input tunable light source parameters, pulse width adjustment, homogenization coupling conditions, and liquid medium properties, thereby quantitatively evaluating the system output indicators.

[0021] This application achieves precise forward control of the generated sound pressure wave intensity by adjusting parameters such as the wavelength, pulse width, and peak power density of the tunable laser. Simultaneously, it can iteratively calculate the optimal laser parameter combination based on the target sound pressure wave intensity required clinically, forming a closed-loop design from "treatment target" to "laser parameters." This invention combines a laser physics model with clinical needs, realizing the quantification, predictability, and controllability of sound pressure wave intensity. It provides a precise and intelligent technical solution for the treatment of intravascular calcification, significantly simplifying physician operations and improving the safety and effectiveness of treatment. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions provided by the present invention.

[0023] Figure 2 This is a structural diagram of the laser-induced acoustic pressure wave closed-loop precision control system for complex intravascular lesions provided by the present invention.

[0024] Figure 3 This is a flowchart for calculating plasma absorbed energy according to the present invention.

[0025] Figure 4 This is a graph showing the change of sound pressure wave over time in different bands with a fixed peak power density of 1*1018W / m3 and a pulse width of 10ns in this application.

[0026] Figure 5 This is a graph showing the change of sound pressure wave with different pulse widths over time, where the peak power density is 1*10¹⁸ W / m³ and the wavelength is 355 nm.

[0027] Figure 6 This is a graph showing the change of sound pressure wave with different power densities over time when the pulse width is fixed at 10 ns and the wavelength is 355 nm in this application. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, one embodiment of the present invention provides a method for precise closed-loop control of laser-induced acoustic pressure waves for complex intravascular lesions, comprising the following steps: S1. Establish a physical model for the generation of acoustic pressure waves coupled by laser-plasma-liquid media; The process of establishing the physical model for generating acoustic pressure waves via laser-plasma-liquid medium coupling includes: A plasma energy density integral model is established to simulate the process of laser-induced plasma bubble formation by breaking down a liquid medium. Traditional models employ a static energy distribution method based on geometric proportions; this invention innovatively proposes a precise calculation method based on energy density integration. The effective initial energy E driving the acoustic pressure wave is: (Formula 1) Where E' is the plasma energy density. For short pulses (pulse width) (less than the electron-ion energy relaxation time), which can be approximated as For longer pulses, collision losses and recombination losses must be taken into account: (Formula 2) Where E' is the plasma energy density, Laser waist radius Free electron density as a function of time : Free electron density, ΔE: Ionization energy, M: Mass of medium molecules or atoms, m: Electron mass; Avalanche ionization coefficient; Laser pulse width; : Laser angular frequency.

[0030] like Figure 3 A sub-model of ionization dynamic evolution based on the free electron density rate equation was established, and the free electron density was solved. A time-varying rate equation to characterize the plasma formation process; When a liquid medium (such as water) is subjected to a strong laser, initial free electrons are generated through multiphoton ionization and avalanche ionization. Free electron density. The evolution is described by the following rate equation: (Formula 3) in: The multiphoton ionization rate is given by the expression for multiphoton ionization, which is dominant for ultraviolet lasers (such as water, which has strong absorption at 308 nm and 355 nm). (Formula 4) in, Dawson's probability integral: The avalanche ionization coefficient depends on the laser intensity I and the angular frequency. : (Formula 5) g' is the diffusion loss coefficient: (Formula 6) The electron-ion recombination coefficient (usually taken as 2 × 10⁻⁶) -9 cm 3 / s).

[0031] Where E is the effective initial energy driving the sound pressure wave, and γ is the adiabatic index of the gas or plasma inside the bubble. Laser pulse width; R0: initial radius of the bubble; W mpi For multiphoton ionization rate, g is the avalanche ionization coefficient; g′ is the diffusion loss coefficient; is the composite coefficient.

[0032] A sub-model of bubble expansion dynamics based on the Kirkwood-Bethe approximation was established; the energy conversion and pressure transmission process of acoustic pressure waves were simulated. After plasma is formed, high-temperature, high-pressure bubbles expand in the liquid. The internal pressure p1 of the bubble and the bubble expansion velocity u satisfy the following condition: Based on the energy balance equation, the bubble radius estimation formula is as follows: (Formula 7) The relationship between the pressure inside the bubble and the deposition energy E is as follows: (Formula 8) The relationship between enthalpy H, radius R, and expansion velocity u = dR / dt during bubble expansion is described by the Kirkwood-Bethe approximate kinetic equation: (Formula 9) Where H: enthalpy, unit: J / kg; t: time, unit: s; c: speed of sound in liquid, unit: m / s; u=dR / dt: bubble expansion velocity, unit: m / s; R: instantaneous radius of bubble, unit: m A sub-model for the propagation and attenuation of sound pressure waves based on the Tait equation of state was established; the long-distance propagation and attenuation process of sound pressure waves in liquid media was simulated. Specifically, this includes: Figure 3 Finally, as the sound pressure wave propagates in the liquid, the attenuation law of the peak pressure p(r,t) with respect to distance r and time t is as follows: (Formula 10) The pressure correction factor θ and the nonlinear attenuation factor g are defined as follows: (Formula 11) (Formula 12) The above models together constitute a complete forward computation chain: given laser parameters The sound pressure wave intensity p can be calculated using the above set of equations (τ, I).

[0033] S2. Obtain the type of complex lesion in the blood vessel and the target acoustic pressure wave intensity; design the reverse acoustic pressure wave parameters of the acoustic pressure wave generation physical model based on the target acoustic pressure wave intensity to obtain the optimal combination of laser parameters; Based on the above positive mapping The reverse design problem is transformed into solving the following constrained optimization problem: (τ, I) The constraints are: Where p target To achieve the target sound pressure wave intensity required for clinical use, (λ) min , λ max ), , I max These represent the adjustable ranges of wavelength, pulse width, and peak power density of the tunable laser, respectively.

[0034] In designing the parameters of the reverse acoustic pressure wave, this invention employs the Particle Swarm Optimization (PSO) algorithm to solve the aforementioned optimization problem due to its excellent global convergence in multidimensional nonlinear optimization. The solution steps are as follows: Step 1: Initialize the particle swarm. Set the population size N, and randomly initialize N sets of laser parameters (λ). i , τ i I i ), and initialize the velocity of each particle.

[0035] Step 2: Fitness Assessment. For each set of parameters, the forward model f is used to calculate the corresponding sound pressure wave intensity p. calc And calculate the fitness value.

[0036] Step 3: Update the individual optimal and global optimal. For each particle, if the current fitness is better than its historical optimal p... best，i Then update p best，i If the current fitness is better than the global optimum g best Then update g best .

[0037] Step 4: Update particle velocity and position. Iterate according to the PSO velocity-position update formula: Where w is the inertia weight, c1 and c2 are learning factors, and r1 and r2 are random numbers in [0,1].

[0038] Step 5: Convergence check. When the number of iterations reaches the maximum number of iterations K... max Or the global optimal fitness is below a threshold Stop iterating when the time comes.

[0039] After iterative convergence, the output is the laser parameter combination (λ) that minimizes the fitness. opt , τ opt I opt This combination satisfies the target sound pressure wave intensity p. target The optimal laser parameters are used to drive a tunable laser for personalized treatment.

[0040] S3. Based on the obtained optimal combination of laser parameters, control the tunable laser to emit laser pulses; S4. Simulate the acoustic pressure wave generation process of laser pulse irradiation into blood vessels and predict the acoustic pressure wave intensity. S5. Obtain the measured sound pressure wave signal and compare the measured sound pressure wave signal with the predicted sound pressure wave intensity in real time. S6. If the difference between the measured sound pressure wave signal and the predicted sound pressure wave intensity exceeds the preset threshold, control the tunable laser to adjust the output laser pulse parameters.

[0041] like Figure 2 This application also provides a laser-induced acoustic pressure wave closed-loop precision control system for complex intravascular lesions, which includes the following steps for implementing the above-mentioned laser-induced acoustic pressure wave closed-loop precision control method: a computer 1, a tunable light source 2, and a pulse width adjustment 3, a homogenization coupling 4, an optical fiber and a liquid medium 5, and an acoustic wave detector 6, which are sequentially provided after the tunable light source 2. The computer is equipped with a multi-physics coupling modeling module, a forward laser parameter control module, a reverse acoustic pressure wave parameter design module, a full-chain acoustic pressure wave generation simulation module, and a closed-loop feedback adaptive therapy module. The multiphysics coupling modeling module is used to establish a physical model for the generation of acoustic pressure waves coupled with laser-plasma-liquid medium. It dynamically describes the ionization, avalanche, diffusion and recombination processes by solving the free electron density rate equation, and accurately calculates the effective energy deposition using the plasma energy density integral method. Combined with the bubble expansion dynamics and acoustic pressure wave propagation model, it realizes the simulation of the entire process from laser incident to acoustic pressure wave output. The forward laser parameter control module is used to predict the intensity, spatial distribution and range of sound pressure waves under different parameter combinations by adjusting one or more parameters of the wavelength, pulse width or peak power density of the tunable laser source based on the multiphysics model, thereby achieving active, repeatable and precise control of the sound pressure wave output. The reverse acoustic pressure wave parameter design module is used to solve the optimal combination of laser wavelength, pulse width and energy using a numerical optimization algorithm based on the target acoustic pressure wave intensity required in clinical practice. This establishes a calculable mapping relationship from the treatment target to the laser parameters, enabling the automated generation of laser parameters for personalized treatment. The full-chain acoustic pressure wave generation simulation module is used to solve the sub-models in the acoustic pressure wave generation physical model simultaneously, providing a systematic acoustic pressure wave generation simulation capability for coupled laser plasma liquid media. The closed-loop feedback adaptive treatment module is used to integrate a sound wave detector into the treatment system to collect sound pressure wave signals in real time, run a real-time control algorithm to compare the measured values ​​with the model prediction values, and dynamically adjust the wavelength, pulse width or energy parameters of the laser according to the deviation, so as to realize online monitoring, feedback and adaptive adjustment, thereby improving the safety and effectiveness of treatment of complex intravascular lesions.

[0042] like Figure 4-6 The diagram shows different combinations that can be achieved during the debugging process of this application, for example: Figure 4 This is a graph showing the change in sound pressure levels over time for different frequency bands with a fixed peak power density of 1*10¹⁸ W / m³ and a pulse width of 10 ns, as described in this application. Figure 4 (a) has a wavelength of 308 nm. Figure 4 (b) is 355nm. Figure 4 (c) is 532nm. Figure 4 (d) is 1064nm. Figure 5 This is a graph showing the change in sound pressure level over time for a fixed peak power density of 1*10¹⁸ W / m³ and a wavelength of 355 nm with different pulse widths, as described in this application. Figure 5 (a) has a pulse width of 35 fs. Figure 5 (b) has a pulse width of 16 ps. Figure 5 (c) has a pulse width of 1 ns. Figure 5 (d) has a pulse width of 10 ns; Figure 6 This is a graph showing the change of sound pressure wave with different power densities over time when the pulse width is fixed at 10ns and the wavelength is 355nm in this application. Figure 6 (a) has a power density of 1*10 15 W / m 3 , Figure 6 (b) has a power density of 1*10 16 W / m 3 , Figure 6 (c) has a power density of 1*10 17 W / m 3 , Figure 6 (d) has a power density of 1*10 18 W / m 3 .

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for precise closed-loop control of laser-induced acoustic pressure waves for complex intravascular lesions, characterized in that: Includes the following steps: S1. Establish a physical model for the generation of acoustic pressure waves coupled by laser-plasma-liquid media; S2. Obtain the type of complex lesion in the blood vessel and the target acoustic pressure wave intensity; design the reverse acoustic pressure wave parameters of the acoustic pressure wave generation physical model based on the target acoustic pressure wave intensity to obtain the optimal combination of laser parameters; S3. Based on the obtained optimal combination of laser parameters, control the tunable laser to emit laser pulses; S4. Simulate the acoustic pressure wave generation process of laser pulse irradiation into blood vessels and predict the acoustic pressure wave intensity. S5. Obtain the measured sound pressure wave signal and compare the measured sound pressure wave signal with the predicted sound pressure wave intensity in real time. S6. If the difference between the measured sound pressure wave signal and the predicted sound pressure wave intensity exceeds the preset threshold, control the tunable laser to adjust the output laser pulse parameters.

2. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 1, characterized in that, In S1, the process of establishing the physical model for the generation of acoustic pressure waves coupled with laser-plasma-liquid media includes: An integral model of plasma energy density was established to simulate the process of laser breaking down a liquid medium to generate plasma and form bubbles. A sub-model of ionization dynamic evolution based on the free electron density rate equation is established, and the free electron density is solved. A time-varying rate equation to characterize the plasma formation process; A sub-model of bubble expansion dynamics based on the Kirkwood-Bethe approximation was established; the energy conversion and pressure transmission process of acoustic pressure waves were simulated. A sub-model for the propagation and attenuation of acoustic pressure waves based on the Tait equation of state was established; the long-distance transmission and attenuation process of acoustic pressure waves in liquid media was simulated.

3. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 2, characterized in that, The plasma energy density integral model includes: Calculate the effective initial energy of the driving sound pressure wave ; When it is a short pulse ; When it is a long pulse ; Where E' is the plasma energy density, Laser waist radius Free electron density as a function of time : Free electron density, ΔE: Ionization energy, M: Mass of medium molecules or atoms, m: Electron mass; Avalanche ionization coefficient; Laser pulse width; : Laser angular frequency.

4. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 2, characterized in that, The ionization dynamic evolution sub-model based on the free electron density rate equation includes: Bubble radius estimation equation ; Equation for bubble pressure and expansion rate: ; Equation of pressure inside the bubble and deposition energy ; ； Where E is the effective initial energy driving the sound pressure wave, and γ is the adiabatic index of the gas or plasma inside the bubble. Laser pulse width; R0: initial radius of the bubble; W mpi For multiphoton ionization rate, g is the avalanche ionization coefficient; g′ is the diffusion loss coefficient; is the composite coefficient.

5. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 4, characterized in that, The expression for the multiphoton ionization rate is: in, Dawson's probability integral: , Laser angular frequency, unit: rad / s; m′: effective electron mass, unit: kg; Reduced Planck constant, 1.0546 × 10⁻⁶ -34 J*s; e: elementary charge; I: laser intensity, unit: W / m 2 ΔE: Ionization energy of the medium; c: Speed ​​of light; : Absorption cross section of the medium molecules for laser light; n: Refractive index of the medium; k: Number of photons required for multiphoton ionization.

6. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 2, characterized in that, The Kirkwood-Bethe approximation of the bubble expansion dynamics sub-model includes: ; Where H: enthalpy, unit: J / kg; t: time, unit: s; c: liquid sound speed, unit: m / s; u=dR / dt: bubble expansion velocity, unit: m / s; R: instantaneous radius of bubble, unit: m.

7. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 2, characterized in that, The sound pressure wave propagation and attenuation sub-model based on the Tait equation of state includes: calculating the attenuation relationship of the peak pressure p(r,t) with distance r and time t when the sound pressure wave propagates in the liquid. Wherein, the pressure correction factor θ and the nonlinear attenuation factor g are defined as follows: ； ； in: : Pressure correction factor, c: Liquid sound velocity; R0: Initial radius of bubble; r: Propagation distance; p1: Internal pressure of bubble; t: Time.

8. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to any one of claims 1-7, characterized in that, The mapping relationships between the sub-models in the physical model of acoustic pressure wave generation coupled with laser-plasma-liquid media together constitute a complete forward computational chain: for a given laser parameter The acoustic pressure wave intensity p is obtained by calculating the forward calculation link (τ, I).

9. The laser-induced acoustic pressure wave closed-loop precise control method for complex intravascular lesions according to claim 8, characterized in that, In S2, the physical model for generating sound pressure waves is designed in reverse based on the target sound pressure wave intensity; this includes solving the constraint optimization equations shown in the following formula in reverse, using a particle swarm optimization algorithm based on the mapping relationship between each sub-model: Optimization equation: The constraints are: Where, p target To achieve the target sound pressure wave intensity required for clinical use, (λ) min , λ max ), , I max These represent the adjustable ranges of wavelength, pulse width, and peak power density of the tunable laser, respectively.

10. A laser-induced acoustic pressure wave closed-loop precision control system for complex intravascular lesions, comprising the steps of implementing the laser-induced acoustic pressure wave closed-loop precision control method for complex intravascular lesions as described in any one of claims 1-9, including: The computer includes a tunable light source, and a pulse width adjustment module, a homogenization coupling device, an optical fiber and an acoustic wave detector are sequentially arranged after the tunable light source. The computer is equipped with a multi-physics coupling modeling module, a forward laser parameter control module, a reverse acoustic pressure wave parameter design module, a full-chain acoustic pressure wave generation simulation module, and a closed-loop feedback adaptive therapy module. The multiphysics coupling modeling module is used to establish a physical model for the generation of acoustic pressure waves coupled with laser-plasma-liquid medium. It dynamically describes the ionization, avalanche, diffusion and recombination processes by solving the free electron density rate equation, and accurately calculates the effective energy deposition using the plasma energy density integral method. Combined with the bubble expansion dynamics and acoustic pressure wave propagation model, it realizes the simulation of the entire process from laser incident to acoustic pressure wave output. The forward laser parameter control module is used to predict the intensity, spatial distribution and range of sound pressure waves under different parameter combinations by adjusting one or more parameters of the wavelength, pulse width or peak power density of the tunable laser source based on the multiphysics model, thereby achieving active, repeatable and precise control of the sound pressure wave output. The reverse acoustic pressure wave parameter design module is used to solve the optimal combination of laser wavelength, pulse width and energy using a numerical optimization algorithm based on the target acoustic pressure wave intensity required in clinical practice. This establishes a calculable mapping relationship from the treatment target to the laser parameters, enabling the automated generation of laser parameters for personalized treatment. The full-chain acoustic pressure wave generation simulation module is used to solve the sub-models in the acoustic pressure wave generation physical model simultaneously, providing a systematic acoustic pressure wave generation simulation capability for coupled laser plasma liquid media. The closed-loop feedback adaptive treatment module is used to integrate a sound wave detector into the treatment system to collect sound pressure wave signals in real time, run a real-time control algorithm to compare the measured values ​​with the model prediction values, and dynamically adjust the wavelength, pulse width or energy parameters of the laser according to the deviation, so as to realize online monitoring, feedback and adaptive adjustment, thereby improving the safety and effectiveness of treatment of complex intravascular lesions.

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