A COMSOL-based dynamic simulation method and system for a three-dimensional temperature field of microwave lipolysis

Abstract

This invention discloses a COMSOL-based method and system for dynamic simulation of the three-dimensional temperature field in microwave liposuction. The method comprises: Step 1, constructing a three-dimensional geometric model of the skin tissue-microwave liposuction antenna coupling system; Step 2, establishing a multi-physics coupling model, including bidirectional coupling of the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field; Step 3, setting dynamic coupling boundary conditions, calculating and updating the blood perfusion rate in real time based on the current tissue temperature, and feeding it back to the heat transfer calculation in the next time step, thereby realizing the dynamic feedback coupling of electromagnetic heat generation and the temperature field; Step 4, using a transient fully coupled solver to jointly solve the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field to obtain the spatiotemporal distribution data of the three-dimensional temperature field of the skin tissue during microwave liposuction. This invention achieves accurate simulation of the microwave liposuction process by introducing dynamic physiological parameters and bidirectional multi-physics coupling.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic simulation, and specifically relates to a method and system for dynamic simulation of three-dimensional temperature field of microwave lipolysis based on COMSOL. Background Technology

[0002] With the increasing prevalence of obesity, the demand for non-invasive or minimally invasive liposuction techniques is growing. Traditional liposuction methods (such as invasive liposuction) have problems such as large trauma, slow recovery, and common complications. Microwave liposuction, as an emerging technology, has the potential to act locally and with less trauma. However, current temperature field simulation and control technologies are not yet perfect and cannot meet the needs of precise liposuction and preoperative assessment.

[0003] The specific treatment principle of microwave liposuction is as follows: Microwave liposuction antennas act on skin tissue, increasing the temperature and damaging the fat tissue. When the heat energy is focused on the fat tissue, it can induce apoptosis and metabolism in fat cells. When the heat energy raises the temperature of the dermis to 42-65℃, collagen fibers contract and denature, inducing a wound healing response in the dermis, stimulating continuous collagen regeneration and remodeling, thereby achieving the effect of skin tightening and wrinkle removal.

[0004] Studies have shown that under the influence of high-frequency alternating electromagnetic fields, water molecules, due to their own polarity, will rapidly deflect and rotate with the direction of the electric field, causing violent collisions and friction with surrounding water molecules, converting electromagnetic energy into heat energy. When the local temperature rises to 42°C or above the apoptosis threshold temperature of adipocytes, tissue proteins denature, ultimately achieving fat ablation and promoting collagen regeneration.

[0005] Temperature field distribution is one of the important indicators for evaluating the effects of microwave liposuction beauty devices on the skin. Currently, there is almost no research on temperature field simulation technology for microwave liposuction, and existing simulation studies are not comprehensive enough, failing to use dynamic parameters to accurately reflect the actual conditions of in vivo tissues, resulting in relatively simplistic skin models. Furthermore, the quality of domestic microwave beauty devices varies greatly, and there is a lack of clear simulation standards and parameters to constrain both safety and efficacy.

[0006] This study focuses on the application of multi-electrode microwaves to skin tissue. A complex skin tissue model is constructed, and dynamic parameters are input to make it more realistic. Under various parameter conditions, the influence of each parameter condition on the skin temperature distribution is explored to fill the gap in related microwave lipolysis simulation research. Summary of the Invention

[0007] The purpose of this invention is to provide a three-dimensional temperature field dynamic simulation method and system for microwave liposuction based on COMSOL. By using a real dynamic parameter model of in vivo skin tissue, the thickness of the epidermis, dermis, fat layer and muscle layer of a real individual is measured to establish a three-dimensional finite element simulation model, calculate the thermal field of skin tissue liposuction, calculate the equivalent cumulative thermal effect, guide the determination of microwave liposuction scheme, and realize the quantification of temperature measurement and over-limit protection.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A dynamic simulation method for three-dimensional temperature field of microwave lipolysis based on COMSOL includes the following steps:

[0010] Step 1: Construct a three-dimensional geometric model of the skin tissue-microwave lipolysis antenna coupling system. The skin tissue is arranged in sequence along the depth direction as epidermis, dermis, fat layer and muscle layer. The microwave lipolysis antenna is set on the surface of the skin tissue.

[0011] Step 2: Establish a multi-physics coupling model, including the bidirectional coupling of electromagnetic wave-frequency domain physical field and biological heat transfer physical field. The biological heat transfer physical field adopts the Pennes biological heat transfer equation that considers the temperature dependence of blood perfusion rate.

[0012] Step 3: Set dynamic coupling boundary conditions, calculate and update blood perfusion rate in real time based on the current tissue temperature, and feed it back to the heat transfer calculation in the next time step to realize dynamic feedback coupling between electromagnetic heat generation and temperature field.

[0013] Step 4: Use a transient fully coupled solver to jointly solve the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field to obtain the spatiotemporal distribution data of the three-dimensional temperature field of skin tissue during microwave lipolysis.

[0014] Furthermore, in step 1, the constructed three-dimensional geometric model also includes an air domain, which covers the microwave liposuction antenna and the skin tissue to provide propagation space for electromagnetic waves.

[0015] Furthermore, in step 1, the thickness of each layer of skin tissue is set as a global parameter according to the fat-dissolving area. The global parameter includes the thickness of the epidermis, dermis, fat layer and muscle layer in at least one of the following areas: face, upper arm, abdomen or buttocks.

[0016] Furthermore, in step 2, the Pennes biological heat transfer equation is:

[0017]

[0018] Where ρ is the density of each tissue, ρ b C is blood density, C is the specific heat capacity of various tissues, Cb This refers to the heat capacity of blood, where T is tissue temperature, t is time, and k is the thermal conductivity. It is a temperature-dependent blood perfusion rate, T b Q is the arterial blood temperature, and Q is the power density generated by the external heat source. met It is the heat generated by the metabolism of various tissues.

[0019] Furthermore, in step 2, the bidirectional coupling between the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field is achieved through the multiphysics coupling interface built into COMSOL, using electromagnetic loss as a heat source. It is incorporated into the biological heat transfer equation.

[0020] Furthermore, in step 3, the temperature dependence of blood perfusion rate is achieved through a real-time feedback mechanism, specifically: based on the tissue temperature at the current time step, through... Coefficient formula for updating blood perfusion rate And use it for the biological heat transfer calculation in the next time step, the The coefficient formula is:

[0021]

[0022] in, This refers to the baseline blood perfusion rate at 37°C. This is a variation factor, with a value ranging from 2.0 to 3.0. The temperature is 37℃.

[0023] Furthermore, in step 4, the transient fully coupled solver uses a direct linear solver to process the coupled equations formed by the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field, the time stepping uses adaptive step size control, and the nonlinear solver uses the free height nonlinear Newton method.

[0024] Furthermore, it also includes step 5: visualizing the spatiotemporal distribution data obtained in step 4 to obtain temperature field distribution views under different times and different parameter conditions; the parameters include at least one of microwave output power, output frequency, ablation time, antenna electrode height, antenna electrode diameter or antenna electrode spacing.

[0025] This invention also provides a COMSOL-based three-dimensional temperature field dynamic simulation system for microwave lipolysis, used to implement the method, including:

[0026] The skin tissue layered geometry module includes the epidermis, dermis, fat layer, muscle layer arranged sequentially along the depth direction, and a microwave lipolysis antenna disposed on the surface of the skin tissue.

[0027] The electromagnetic-thermal multiphysics coupling module includes bidirectional data exchange between an electromagnetic wave-frequency domain interface and a biological heat transfer interface. The biological heat transfer interface incorporates the Pennes equation, which considers the temperature dependence of blood perfusion rate.

[0028] The dynamic parameter update module is used to perform real-time updates and feedback calculations of blood perfusion rate based on tissue temperature;

[0029] The transient solution module is configured as a fully coupled solver, used to jointly solve the electromagnetic-thermal coupled equations and output the three-dimensional dynamic temperature field distribution.

[0030] Furthermore, the microwave fat-dissolving antenna has a coaxial structure with a waveguide port at its feed boundary, activated by the wave excitation on the side close to the skin, and an ideal electrical conductor boundary condition is set between the central conductor and the shielding layer to form a slit structure.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0032] 1. By introducing real physiological dynamic parameters and blood perfusion effects, the bioequivalence of the simulation model is improved by more than 20%, providing a theoretical basis and technical support for personalized liposuction.

[0033] 2. By setting global parameters, the electrode diameter, electrode spacing, electrode spatial distribution, electrode height, thickness of each skin tissue layer, output frequency, output power, ablation time, etc. can be adjusted to achieve temperature field simulation of multiple parts, multiple frequencies, multiple powers, and multiple time domains under the same model.

[0034] 3. The microwave liposuction antenna is designed with a circular port and a circular port reference axis is set. The end close to the skin tissue outputs wave excitation to realize the concentrated output of microwave energy and realize the efficient conversion of electromagnetic energy into heat energy.

[0035] 4. By setting different solution steps and their respective optimal solver configurations, the system can quickly solve complex models with high degrees of freedom that are difficult to solve, and present accurate temperature simulation results while taking into account both computational accuracy and computational speed.

[0036] 5. The simulation under the dynamic parameter model realizes that the energy is concentrated in the fat layer, and the energy is not concentrated in the epidermis and dermis, so as not to cause burns to the skin tissue. It achieves a high concentration of energy in the fat layer, that is, precise energy delivery.

[0037] 6. Effectively avoids the "heat sink effect" and does not cause heat damage to the muscle layer. The temperature rise of the epidermis is ≤42℃ and the temperature rise of the muscle layer is ≤45℃, effectively achieving 20% ​​energy absorption by the epidermis / dermis and 80% absorption by the fat layer. Attached Figure Description

[0038] Figure 1 : Flowchart of the method of the present invention;

[0039] Figure 2 (a) is a structural diagram of the microwave lipolysis antenna constructed in this invention, (b) is a geometric model diagram constructed in this invention, (c) is a finite element model of this invention, and (d) is the simulation result of this invention, showing the three-dimensional simulation multi-section result at an ablation dose of 2.45 GHz, 13.5 W, and 600 s (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0040] Figure 3 (a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0041] Figure 4 (a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 120 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 120 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0042] Figure 5 (a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 15 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 15 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0043] Figure 6(a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 0.915 GHz, 13.5 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 0.915 GHz, 13.5 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0044] Figure 7 (a) shows the simulation results of this invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 10 mm, electrode diameter 20 mm, electrode spacing 30 mm); (b) shows the simulation results of this invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 10 mm, electrode diameter 20 mm, electrode spacing 30 mm).

[0045] Figure 8 (a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 15 mm, electrode spacing 30 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 15 mm, electrode spacing 30 mm).

[0046] Figure 9 (a) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field distribution map of the skin tissue section (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 40 mm); (b) shows the simulation results of the present invention, displaying the three-dimensional simulation results at an ablation dose of 2.45 GHz, 13.5 W, and 600 s, and the temperature field of the skin tissue section and its 42°C isotherm range map (electrode height 5 mm, electrode diameter 20 mm, electrode spacing 40 mm). Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1: Dynamic Simulation Method of Three-Dimensional Temperature Field for Microwave Lipolysis Based on COMSOL

[0049] like Figure 1 As shown, the present invention provides a three-dimensional temperature field dynamic simulation method for microwave lipolysis based on COMSOL, comprising the following steps:

[0050] Step 1, Global Parameter Settings:

[0051] As shown in Table 1, the thicknesses of the epidermis, dermis, fat layer, and muscle layer in the area requiring fat reduction were measured, and the fat reduction time, electrode diameter, electrode spacing, electrode height, and number of electrodes for the microwave fat reduction antenna were determined. The measured parameters were then used for global parameter settings.

[0052] Table 1. In vivo skin tissue thickness

[0053]

[0054] Step 2, construct the 3D geometric model:

[0055] A layered 3D model of skin tissue was built using COMSOL. A microwave liposuction antenna model was then established above the working plane of the epidermis. The constructed geometric model is as follows: Figure 2 As shown in (b), the specific components of this simulation model are as follows:

[0056] Muscle layer 1, fat layer 2, dermis layer 3, epidermis layer 4, microwave fat-dissolving antennas 5, 6, 7, and 8, and an air domain positioned above 1 to 8.

[0057] Step 3, setting material parameters:

[0058] Different materials and parameters are set for the computational domain in the model. The specific material types are: copper antenna, air, epidermis / dermis / fat / muscle layer; the specific parameters of each material are set according to Table 2.

[0059] Table 2 Parameters of Simulation Materials

[0060] Step 4, construct a multiphysics coupling model:

[0061] An electromagnetic wave-frequency domain (EMW) and biological heat transfer (HT) model was constructed. The transfer of microwave heat within biological tissues follows the Penns biological heat transfer (HT) model:

[0062]

[0063] Thermal damage to biological tissues follows the Arrhenius equation and the thermal damage equation:

[0064]

[0065]

[0066]

[0067] Q 10 The formula for the temperature coefficient is:

[0068]

[0069]

[0070] Where ρ is the density of each tissue (kg / m³) 3 ), ρ b Blood density (kg / m³) 3 C is the specific heat capacity of each tissue (J / kg·K). b Here, T is the blood heat capacity (J / kg·K), k is the tissue temperature (K), k is the thermal conductivity (W / m·K), and w is the blood perfusion rate (1 / s). b Q is the arterial blood temperature (K), and Q is the power density generated by the external heat source (W / m²). 3 ), Q met The metabolic heat production of various tissues (W / m 3 ); Q met The metabolic heat production of various tissues (W / m 3 ), Q 10 Let Q be a variation factor (2.0~3.0). 10 =2.5, T0=37℃.

[0071] In COMSOL, the constructed geometric model contains multiple domains, such as Figure 2 As shown in (b), the layers are numbered as follows: muscle layer 1, fat layer 2, dermis layer 3, epidermis layer 4, microwave lipolysis antennas 5, 6, 7, 8 (the specific numbering depends on the modeling order), and the air domain is located above 1 to 8. The bio-heat transfer domain is selected as the skin tissue region, i.e., domains 1 to 4; the electromagnetic wave-frequency domain is selected as the entire model region, i.e., domains 1 to 8. The multiphysics coupling interface electromagnetic setting is: electromagnetic wave-frequency domain, and the heat transfer setting is: bio-heat transfer.

[0072] Step 5, set dynamic parameters:

[0073] The initial temperature of the skin tissue and the microwave liposuction antenna was defined as 37°C, and the reference pressure was 1 atm, to simulate the microwave liposuction surgical environment.

[0074] Dynamic parameters were set according to Tables 3 and 4 to simulate the actual blood perfusion rate and metabolic heat production in the human body.

[0075] Table 3 Thermal properties of tissue

[0076] organize <![CDATA[C p / (J / kg·K)]]> <![CDATA[ρ / (kg / m 3 )]]> k / (W / m·k) Epidermis / Dermis <![CDATA[3240+0.49T+2.12×10 -3 T 2 ]]> <![CDATA[1070-0.2T-2.17×10 -3 T 2 ]]> <![CDATA[0.40+9.51×10 -4 T-4.64×10 -6 T 2 ]]> fat layer <![CDATA[2210+1.31T-3.66×10 -3 T 2 ]]> <![CDATA[946-0.38T-3.87×10 -4 T 2 ]]> <![CDATA[0.22-2.19×10 -3 T-9.19×10 -7 T 2 ]]> muscle layer <![CDATA[3499-0.3T+3.23×10 -3 T 2 ]]> <![CDATA[1051.79-0.14T-2.64×10 -2 T 2 ]]> <![CDATA[0.45+1.31×10 -3 T-5.41×10 -6 T 2 ]]>

[0077] Table 4. Tissue blood perfusion rate and metabolic heat

[0078] organize <![CDATA[w b,0 / S -1 ]]> <![CDATA[q met,0 / W·m -3 ]]> Epidermis / Dermis <![CDATA[1.44×10 -3 ]]> 368 fat layer <![CDATA[3.60×10 -6 ]]> 58 muscle layer <![CDATA[3.60×10 -6 ]]> 684

[0079] Step 6, Mesh Generation:

[0080] To meet the requirements of computational accuracy and solution speed, mesh-based solutions can be implemented, and all solutions can be set to free tetrahedral meshes.

[0081] Step 7, Solver Configuration:

[0082] Update the solver configuration for efficient solving. Configure the solver as a fully coupled solver under the transient solver; set the linear solver of the fully coupled solver to direct, and the nonlinear method to automatic highly nonlinear (Newton); adjust the threshold values ​​of each coefficient according to the hardware configuration and computational accuracy.

[0083] Step 8, Research Setup:

[0084] Select frequency domain-transient / frequency domain-steady-state analysis. Output frequency is 2.45GHz or 0.915GHz, output time step is range(0,1,10), total ablation time is 10 minutes, and a simulation result is output every minute, enabling plotting temperature field distribution results at different times under the same model. Simultaneously, it can achieve arbitrary output power conversion, arbitrary ablation duration, and output simulation results according to arbitrary time steps.

[0085] Step 9, visualize the results:

[0086] By plotting temperature field distribution images and visualizing the simulation data, the distribution law of the temperature field can be obtained.

[0087] Simulation results are as follows Figure 3-6 The values ​​were displayed as: 2.45GHz, 13.5W, 600s; 2.45GHz, 13.5W, 120s; 2.45GHz, 15W, 600s; and 0.915GHz, 13.5W, 600s, respectively, indicating that the energy and temperature fields were mainly concentrated in the fat layer region.

[0088] like Figure 7-9 The conclusions are as follows: (1) Electrode height has almost no effect on the temperature of the fat-dissolving center region; (2) The larger the electrode diameter, the higher the temperature of the center region; (3) The closer the electrode spacing, the higher the temperature of the center region; (4) 2.45 GHz is more likely to form a concentrated fat layer energy than 915 MHz.

[0089] Step 10, output simulation results:

[0090] Output the simulation results and optimize the microwave liposuction antenna design based on the simulation results.

[0091] Step 11, Model Iteration:

[0092] The global parameters are updated according to the actual simulation requirements to achieve iterative updates of the simulation model.

[0093] Example 2: Simulation of different parts

[0094] This embodiment is basically the same as Embodiment 1, except that the skin tissue thickness parameters set according to Table 1 in step 1 are different. By modifying the global parameters, model conversion for different parts can be quickly achieved, and the temperature field distribution of the corresponding parts can be obtained.

[0095] Example 3: Simulation of Different Antenna Structures

[0096] This embodiment is basically the same as Embodiment 1, except that the antenna structure parameters are different. By adjusting parameters such as the number of electrodes, electrode diameter, electrode spacing, electrode spatial distribution, and electrode height, the influence of these parameters on the temperature field distribution is studied to guide the design of the optimal ablation size parameters for the multi-antenna microwave lipolysis device.

[0097] Example 3: Three-dimensional temperature field dynamic simulation system for microwave liposuction based on COMSOL

[0098] This embodiment provides a COMSOL-based three-dimensional temperature field dynamic simulation system for microwave lipolysis, used to implement the above method, including:

[0099] The skin tissue layered geometry module includes the epidermis, dermis, fat layer, muscle layer arranged sequentially along the depth direction, and a microwave lipolysis antenna disposed on the surface of the skin tissue.

[0100] The electromagnetic-thermal multiphysics coupling module includes bidirectional data exchange between an electromagnetic wave-frequency domain interface and a biological heat transfer interface. The biological heat transfer interface incorporates the Pennes equation, which considers the temperature dependence of blood perfusion rate.

[0101] The dynamic parameter update module is used to perform real-time updates and feedback calculations of blood perfusion rate based on tissue temperature;

[0102] The transient solution module is configured as a fully coupled solver, used to jointly solve the electromagnetic-thermal coupled equations and output the three-dimensional dynamic temperature field distribution.

[0103] The microwave fat-dissolving antenna has a coaxial structure with a waveguide port at its feed boundary. The side close to the skin is activated by wave excitation, and an ideal electrical conductor boundary condition is set between the center conductor and the shielding layer to form a slit structure.

[0104] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A three-dimensional temperature field dynamic simulation method for microwave liposuction based on COMSOL, characterized in that: Includes the following steps: Step 1: Construct a three-dimensional geometric model of the skin tissue-microwave lipolysis antenna coupling system. The skin tissue is arranged in sequence along the depth direction as epidermis, dermis, fat layer and muscle layer. The microwave lipolysis antenna is set on the surface of the skin tissue. Step 2: Establish a multi-physics coupling model, including the bidirectional coupling of electromagnetic wave-frequency domain physical field and biological heat transfer physical field. The biological heat transfer physical field adopts the Pennes biological heat transfer equation that considers the temperature dependence of blood perfusion rate. Step 3: Set dynamic coupling boundary conditions, calculate and update blood perfusion rate in real time based on the current tissue temperature, and feed it back to the heat transfer calculation in the next time step to realize dynamic feedback coupling between electromagnetic heat generation and temperature field. Step 4: Use a transient fully coupled solver to jointly solve the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field to obtain the spatiotemporal distribution data of the three-dimensional temperature field of skin tissue during microwave lipolysis.

2. The method according to claim 1, characterized in that: In step 1, the constructed three-dimensional geometric model also includes an air domain, which covers the microwave liposuction antenna and the skin tissue to provide propagation space for electromagnetic waves.

3. The method according to claim 1, characterized in that: In step 1, the thickness of each layer of skin tissue is set as a global parameter according to the fat-dissolving area. The global parameter includes the thickness of the epidermis, dermis, fat layer and muscle layer in at least one of the following areas: face, upper arm, abdomen or buttocks.

4. The method according to claim 1, characterized in that: In step 2, the Pennes biological heat transfer equation is: Where ρ is the density of each tissue, ρ b C is blood density, C is the specific heat capacity of various tissues, C b This refers to the heat capacity of blood, where T is tissue temperature, t is time, and k is the thermal conductivity. It is a temperature-dependent blood perfusion rate, T b Q is the arterial blood temperature, and Q is the power density generated by the external heat source. met It is the heat generated by the metabolism of various tissues.

5. The method according to claim 1, characterized in that: In step 2, the bidirectional coupling between the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field is achieved through the multiphysics coupling interface built into COMSOL, using electromagnetic loss as a heat source. It is incorporated into the biological heat transfer equation.

6. The method according to claim 1, characterized in that: In step 3, the temperature dependence of blood perfusion rate is achieved through a real-time feedback mechanism, specifically: based on the tissue temperature at the current time step, through... Coefficient formula for updating blood perfusion rate And use it for the biological heat transfer calculation in the next time step, the The coefficient formula is: in, This refers to the baseline blood perfusion rate at 37°C. This is a variation factor, with a value ranging from 2.0 to 3.

0. The temperature is 37℃.

7. The method according to claim 1, characterized in that: In step 4, the transient fully coupled solver uses a direct linear solver to process the coupled equations formed by the electromagnetic wave-frequency domain physical field and the biological heat transfer physical field. The time stepping uses adaptive step size control, and the nonlinear solver uses the free height nonlinear Newton method.

8. The method according to claim 1, characterized in that: The method also includes step 5: visualizing the spatiotemporal distribution data obtained in step 4 to obtain temperature field distribution views under different time and parameter conditions; the parameters include at least one of microwave output power, output frequency, ablation time, antenna electrode height, antenna electrode diameter or antenna electrode spacing.

9. A COMSOL-based microwave liposuction three-dimensional temperature field dynamic simulation system, used to implement the method described in any one of claims 1 to 8, characterized in that: include: The skin tissue layered geometry module includes the epidermis, dermis, fat layer, muscle layer arranged sequentially along the depth direction, and a microwave lipolysis antenna disposed on the surface of the skin tissue. The electromagnetic-thermal multiphysics coupling module includes bidirectional data exchange between an electromagnetic wave-frequency domain interface and a biological heat transfer interface. The biological heat transfer interface incorporates the Pennes equation, which considers the temperature dependence of blood perfusion rate. The dynamic parameter update module is used to perform real-time updates and feedback calculations of blood perfusion rate based on tissue temperature; The transient solution module is configured as a fully coupled solver, used to jointly solve the electromagnetic-thermal coupled equations and output the three-dimensional dynamic temperature field distribution.

10. The system according to claim 9, characterized in that: The microwave fat-dissolving antenna has a coaxial structure with a waveguide port at its feed boundary. The side close to the skin is activated by wave excitation, and an ideal electrical conductor boundary condition is set between the center conductor and the shielding layer to form a slit structure.

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