Numerical simulation method for large tumor treatment of single-needle multi-point microwave ablation

Abstract

The invention provides a numerical simulation method for large tumor treatment of single-needle multi-point microwave ablation, and belongs to the technical field of large liver tumor data simulation. The method comprises the following steps: establishing a finite element simulation model, and solving the finite element simulation model according to the interaction among an electromagnetic field, heat conduction and biological tissues to obtain a simulation result; constructing a single-needle multi-point microwave ablation numerical model; carrying out ablation simulation by utilizing the single-needle multi-point microwave ablation numerical model, outputting multi-point ablation result data, quantifying the size and form of a solidification area, and carrying out space overlapping analysis on a contour surface to obtain the characteristics of the solidification area; ablation simulation is carried out by setting parameter combinations of pull-back distances and ablation time of a plurality of antennas, and an optimal parameter combination is obtained by combining feature analysis of a solidification area, so that numerical simulation of large tumor treatment is completed; according to the invention, the problems of low ablation temperature, long simulation time and difficulty in accurate positioning of the antenna in the existing single-needle multi-point microwave ablation simulation method are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of large liver tumor data simulation, and in particular relates to a numerical simulation method for large tumor treatment using single-needle multi-point microwave ablation. Background Art

[0002] In the field of microwave ablation simulation, multi-physics modeling of heat conduction, electromagnetic wave propagation, and tissue parameter changes in tumor tissue has become a key research area in thermal ablation technology. Existing studies have primarily used finite element methods to numerically simulate the temperature field distribution after microwave antenna ablation, establishing electromagnetic-thermal coupling models to predict the shape and distribution of the ablation zone. This type of simulation allows for systematic analysis of different antenna parameters, tissue properties, and operational strategies without relying on animal experiments or clinical procedures, thereby assisting in the development of treatment strategies.

[0003] Although single-needle multi-point microwave ablation technology has certain advantages in cost control and operational flexibility, its corresponding numerical simulation method is still immature and still has limitations such as low ablation temperature, long simulation time, and difficulty in accurate antenna positioning. Therefore, how to achieve accurate numerical simulation research on microwave ablation of large tumors based on single-needle multi-point technology is still one of the technical difficulties that need to be solved urgently. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a numerical simulation method for large tumor treatment using single-needle multi-point microwave ablation, which solves the problems of low ablation temperature, long simulation time, and difficulty in precise antenna positioning in the existing single-needle multi-point microwave ablation simulation method.

[0005] To achieve the above objectives, the present invention adopts a technical solution: a numerical simulation method for treating large tumors with single-needle multi-point microwave ablation, comprising the following steps:

[0006] S1. Establish a finite element simulation model and solve it by coupling the electromagnetic field with the Pennes bioheat transfer equation based on the interaction between the electromagnetic field, heat conduction, and biological tissue, thus constructing a numerical model for single-needle multi-point microwave ablation.

[0007] S2. Perform ablation simulation using a single-needle multi-point microwave ablation numerical model, output multi-point ablation result data, quantify the size and shape of the coagulation zone, and perform spatial overlap analysis on the isosurface in the multi-point ablation result data to obtain the characteristics of the coagulation zone;

[0008] S3. By setting multiple antenna pullback distance and ablation time parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model, and combined with analysis of the characteristics of the coagulation zone, the optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment.

[0009] The beneficial effects of the present invention are as follows: the present invention constructs a finite element simulation model based on single-needle multi-point microwave ablation, realizes multi-target superimposed ablation through a single puncture, and proposes overlapping characterization of coagulation zones constructed based on simulation output data, as well as parameter optimization for different antenna pullback distances and time allocation strategies, thereby improving the accuracy of numerical simulation predictions for large tumor treatment, increasing the ablation temperature, reducing simulation time and usage costs, and ensuring accurate antenna positioning.

[0010] Furthermore, the S1 includes the following steps:

[0011] S101. Construct a cylindrical liver tumor model based on a preset radius and height, establish a three-dimensional coordinate system with the microwave antenna's emission point as the center of the circle, insert the microwave antenna longitudinally from the center of the cylinder's bottom at a preset insertion depth, and establish a finite element simulation model.

[0012] S102. Based on the interaction between electromagnetic fields, heat conduction, and biological tissues, the electromagnetic field is calculated using the Helmholtz harmonic equation. Combined with the specific absorption rate and the Pennes bioheat transfer equation, the finite element simulation model is solved to construct a single-needle multi-point microwave ablation numerical model.

[0013] Furthermore, the finite element simulation model is used to simulate the pullback process between microwave antennas in microwave ablation clinical surgery, and includes: a first simulation model and a second simulation model;

[0014] The first simulation model is used to simulate the first ablation process, including the first heating process and the cooling process;

[0015] The second simulation model is constructed based on the temperature parameters generated during the cooling process of the first simulation model, and is used to simulate the second ablation process.

[0016] The beneficial effects of the above further scheme are as follows: the present invention establishes a finite element simulation model, adopts the method of coupling the electromagnetic field and the biological thermal field, utilizes the classic Pennes bioheat transfer equation, and performs numerical modeling based on temperature-changing tissue parameters to establish a reliable prediction model for single-needle multi-point microwave ablation, thereby improving the accuracy and practicality of the numerical simulation of large tumor treatment.

[0017] Furthermore, the S2 includes the following steps:

[0018] S201. Performing ablation simulation using a single-needle multi-point microwave ablation numerical model, and using a specific heat capacity function based on water content variation and a linearly varying thermal conductivity function to describe thermal and electrical parameters of the simulated liver tissue in the single-needle multi-point microwave ablation numerical model, and outputting multi-point ablation result data;

[0019] S202. Based on the multi-point ablation results data, the isotherm threshold method is used to assess the degree of tumor necrosis and characterize the size and morphology of the coagulation zone;

[0020] S203 . Based on the characterized multi-point ablation result data, spatially overlap the isosurfaces and quantify the coagulation zone to obtain the characteristics of the coagulation zone.

[0021] Furthermore, the multi-point ablation result data includes a first simulation model ablation result and a second simulation model ablation result;

[0022] In the step S203 , spatial overlap analysis is performed on the isosurfaces, specifically by spatially overlapping the coagulation zone generated in the ablation result of the first simulation model with the coagulation zone generated in the ablation result of the second simulation model.

[0023] The beneficial effects of the above further scheme are: the present invention improves the accuracy of coagulation zone characterization by merging the coagulation zones of the first and second ablations, overcomes the limitations of coagulation zone evaluation, and provides methodological support for optimizing the clinical application strategy of microwave ablation; establishes a finite element simulation model to study the effects of the first and second ablations on the coagulation zone; forms the effect of coagulation zone superposition in single-needle multi-point microwave ablation simulation, and achieves the same simulation situation as multi-antenna microwave ablation simulation at a significantly reduced cost.

[0024] Furthermore, the S3 includes the following steps:

[0025] S301, based on constant power and total ablation time, setting different antenna pullback distances and first and second ablation times, and combining them into a parameter combination;

[0026] S302. Based on various parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model to obtain the effect of the antenna pullback distance on the morphological characteristics of the coagulation zone and the effect of the first ablation process on the coagulation area.

[0027] S303. Based on the influence of the antenna pullback distance on the morphological characteristics of the coagulation zone and the influence of the first ablation process on the coagulation area, and combined with the characteristics of the coagulation zone, an optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment.

[0028] Furthermore, the effect of the antenna pull-back distance on the morphological characteristics of the coagulation zone is specifically as follows: the greater the antenna pull-back distance, the longer the long axis of the coagulation zone;

[0029] The effect of the first ablation process on the coagulation area is specifically as follows: the longer the first ablation process is, the larger the coagulation area is.

[0030] The beneficial effects of the above-mentioned further scheme are as follows: the present invention sets a combination of antenna pullback distance and ablation time parameters, and obtains the influence of the ablation time allocation strategy and the first and second ablation needle distances on the coagulation zone morphology and temperature distribution through ablation simulation, thereby improving the pertinence and effectiveness of the simulation data, and achieving the optimal parameter combination for dealing with various tumor conditions, thereby improving the applicability and accuracy of the numerical simulation of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flow chart of the method of the present invention.

[0032] Figure 2 This is a geometric diagram of the first simulation model of this embodiment.

[0033] Figure 3 This is a geometric diagram of the second simulation model of this embodiment.

[0034] Figure 4 This is a schematic diagram of the 54°C isothermal surface in this embodiment.

[0035] Figure 5 This is a schematic diagram of spatially overlapping isosurfaces in multi-point ablation result data in this embodiment. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0037] Before describing this embodiment, the following terms are explained:

[0038] MWA: microwave ablation;

[0039] Pennes bioheat transfer equation: a mathematical model proposed by Pennes that describes heat conduction in biological tissues and heat exchange through blood perfusion;

[0040] COMSOL software: a multi-physics numerical simulation software;

[0041] CT: computed tomography.

[0042] Example

[0043] like Figure 1 As shown, the present invention provides a numerical simulation method for treating large tumors with single-needle multi-point microwave ablation, and its implementation method is as follows:

[0044] S1. Establish a finite element simulation model. Based on the interaction between electromagnetic fields, heat conduction, and biological tissues, solve the finite element simulation model by coupling the electromagnetic field with the Pennes bioheat transfer equation to construct a numerical model for single-needle multi-point microwave ablation. Specifically, the model includes:

[0045] S101. Construct a cylindrical liver tumor model based on a preset radius and height, establish a three-dimensional coordinate system with the microwave antenna's emission point as the center of the circle, insert the microwave antenna longitudinally from the center of the cylinder's bottom at a preset insertion depth, and establish a finite element simulation model.

[0046] S102. Based on the interaction between electromagnetic fields, heat conduction, and biological tissues, the electromagnetic field is calculated using the Helmholtz harmonic equation. Combined with the specific absorption rate and the Pennes bioheat transfer equation, the finite element simulation model is solved to construct a single-needle multi-point microwave ablation numerical model.

[0047] In this example, a three-dimensional simulation model was established using COMSOL software. A cylindrical liver tumor model was constructed based on a preset radius of 50 mm and height of 110 mm. A three-dimensional coordinate system was established with the microwave antenna's emission point as the center of the circle. The microwave antenna was inserted longitudinally at the center of the bottom circle with a preset insertion depth of 61.5 mm. To simulate the pullback process between microwave antennas during clinical microwave ablation surgery, this study divided the microwave ablation process into two models. The first simulation model was used to simulate the first ablation process, achieving the first point of single-needle multi-point ablation. The second simulation model was used to simulate the second ablation process, achieving the second point of single-needle multi-point ablation.

[0048] In clinical trials, after the first ablation, a CT or ultrasound scan is required to re-plan the path for the second ablation. During this time, the antenna stops heating and the tissue temperature drops. Therefore, the first ablation process is divided into a heating process and a cooling process.

[0049] The second simulation model is established based on the temperature parameters generated after the cooling process is completed, that is, the temperature parameters output by the first simulation model are used as the initial parameters of the second simulation model; Figure 2 and Figure 3 As shown, the first and second simulation models use the automatic meshing method to perform free tetrahedral meshing. The first simulation model contains 682,364 tetrahedral elements (115,895 vertices); the second simulation model contains 607,141 tetrahedral elements (104,299 vertices), completing the establishment of the finite element simulation model.

[0050] In this embodiment, based on the interaction between electromagnetic field, heat conduction and biological tissue, a method of coupling electromagnetic field and biological thermal field is used to solve the single-needle multi-point MWA finite element simulation model;

[0051] Specifically, the Helmholtz harmonic equation is used to calculate electromagnetic energy deposition and specific absorption rate in tissues, and the Pennes bioheat transfer equation is used to solve transient heat transfer in tissues, and a numerical model of single-needle multi-point microwave ablation is constructed.

[0052] The expression of the numerical model of single-needle multi-point microwave ablation is as follows:

[0053]

[0054] in, represents the curl, is a vector differential operator, μ r Relative magnetic permeability (μ r =1), E represents the electric field strength (unit: V / m), k0 represents the free space wave number, ε r represents the relative dielectric constant of biological tissue, j represents the imaginary unit, σ represents the conductivity of biological tissue (unit: s / m), ω represents the angular frequency, ε0 ​​represents the relative dielectric constant of vacuum, ρ represents the tissue density, SAR represents the specific absorption rate, C p represents the specific heat capacity of the liver (unit: J / (kg·℃)), δ represents the derivative symbol, T represents temperature (unit: ℃), t represents time (unit: s), k represents thermal conductivity, T b represents blood temperature, c b represents the specific heat capacity of blood (unit: J / (kg·℃)), ω b Indicates blood perfusion (unit kg / (m 3 ·s)), Q met Indicates the heat generated by tissue metabolism (unit W / m 3 ).

[0055] S2. Use the single-needle multi-point microwave ablation numerical model to perform ablation simulation, output multi-point ablation result data, quantify the size and shape of the coagulation zone, and perform spatial overlap analysis on the isosurface in the multi-point ablation result data to obtain the characteristics of the coagulation zone, including:

[0056] S201. Perform ablation simulation using a single-needle multi-point microwave ablation numerical model, and use a specific heat capacity function based on water content changes and a linearly changing thermal conductivity coefficient function to describe the thermal parameters and electrical parameters of the simulated liver tissue in the single-needle multi-point microwave ablation numerical model, and output multi-point ablation result data.

[0057] In this embodiment, a single-needle multi-point microwave ablation numerical model was used for ablation simulation. A specific heat capacity function based on water content variation and a linearly varying thermal conductivity function were used to describe the thermal and electrical parameters of the simulated liver tissue in the single-needle multi-point microwave ablation numerical model, thereby obtaining multi-point ablation result data.

[0058] The expression of the specific heat capacity function based on the change of water content is as follows:

[0059]

[0060] Among them, C P (T) represents the specific heat capacity function, C P25℃ Indicates the specific heat capacity at 25°C, C P70℃ Indicates the specific heat capacity at 70℃, k w It represents the coefficient of linear growth of specific heat capacity with temperature change, and α represents the latent heat of tissue phase change;

[0061] The expressions of the relative dielectric constant ε, electrical conductivity σ (unit: s / m) and thermal conductivity k are as follows:

[0062]

[0063] k(T)=k 25℃ +0.00111·(T-25);

[0064] Among them, k 25℃ Indicates the thermal conductivity at 25°C.

[0065] S202. Based on the multi-point ablation results data, the isotherm threshold method is used to assess the degree of tumor necrosis and characterize the size and morphology of the coagulation zone;

[0066] S203 . Based on the characterized multi-point ablation result data, spatially overlap the isosurfaces and quantify the coagulation zone to obtain the characteristics of the coagulation zone.

[0067] In this embodiment, since the liver tissue is between 50°C and 60°C, it will denature in a short time. Figure 4 As shown, this embodiment uses the degree of tumor necrosis based on the 54°C isotherm threshold to evaluate and characterize the size and morphology of the coagulation zone;

[0068] like Figure 5 As shown in the figure, based on the characterized multi-point ablation result data, a new coagulation zone characterization method is proposed, which uses the spatial overlap of the isosurface based on the first and second ablation result data. By merging the coagulation zones of the first and second ablations, an accurate characterization of the final coagulation zone is achieved. This overcomes the limitations of coagulation zone assessment and provides methodological support for optimizing the clinical application strategy of microwave ablation. Figure 5 The medium blue and yellow areas represent the coagulation zones formed by the first and second ablations, respectively, and the green area represents the overlapping portion of the coagulation zones produced by the two ablations. The coagulation zone formed by combining the yellow and blue areas is the characteristic of the coagulation zone ultimately formed by single-needle multi-point microwave ablation.

[0069] S3. By setting multiple antenna pullback distance and ablation time parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model. Combined with analysis of the characteristics of the coagulation zone, the optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment. Specifically, the following are included:

[0070] S301, based on constant power and total ablation time, setting different antenna pullback distances and first and second ablation times, and combining them into a parameter combination;

[0071] S302. Based on various parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model to obtain the effect of the antenna pullback distance on the morphological characteristics of the coagulation zone and the effect of the first ablation process on the coagulation area.

[0072] S303. Based on the influence of the antenna pullback distance on the morphological characteristics of the coagulation zone and the influence of the first ablation process on the coagulation area, and combined with the characteristics of the coagulation zone, an optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment.

[0073] In this embodiment, based on a constant power of 50 W and a total ablation time of 8 minutes, the antenna pullback distances were set to 5 mm and 10 mm, and the time allocation schemes for the first and second ablation time combinations were 2 min-6 min and 4 min-4 min, respectively. The interval between the two ablations was set to 40 seconds. Based on the above-mentioned settings of the antenna pullback distance and the first and second ablation times, four groups of parameter combinations were obtained: 5 mm-4 min-4 min, 10 mm-4 min-4 min, 5 mm-2 min-6 min, and 10 mm-2 min-6 min.

[0074] Based on various parameter combinations, ablation simulations were performed using a single-needle multi-point microwave ablation numerical model. Simulation results showed that the antenna pullback distance was a significant factor affecting the long axis of the coagulation zone, and the greater the antenna pullback distance, the longer the long axis of the coagulation zone.

[0075] like Figure 5 The simulation results show that Figure 5 (a) indicates an ablation time of 4 min-4 min and an ablation distance of 5 mm, (b) indicates an ablation time of 4 min-4 min and an ablation distance of 10 mm, (c) indicates an ablation time of 2 min-6 min and an ablation distance of 5 mm, and (d) indicates an ablation time of 2 min-6 min and an ablation distance of 10 mm. Compared with the 4 min-4 min time allocation scheme, the 2 min-6 min scheme produces a narrower and longer coagulation zone, so the first ablation process has a significant impact on the coagulation area. Moreover, the longer the first ablation process, the larger the coagulation area.

[0076] Based on the simulated influence of the antenna pullback distance on the long axis of the coagulation zone and the influence of the first ablation process on the coagulation area, a practical analysis was conducted in combination with the characteristics of the coagulation zone. Specific settings were made according to the shape, size, and location of the actual patient's tumor to obtain the optimal parameter combination and achieve accurate numerical simulation.

[0077] In this embodiment, the accuracy and reliability of the simulation results of the present invention were verified through in vitro experiments, providing valuable simulation basis for clinicians, helping to optimize personalized single-needle multi-point microwave ablation plans, and improving the accuracy and safety of single-needle multi-point microwave ablation.

Claims

1. A numerical simulation method for single-needle multi-point microwave ablation of large tumors, characterized in that: The following steps are involved: S1. Establish a finite element simulation model and solve it by coupling the electromagnetic field with the Pennes bioheat transfer equation based on the interaction between the electromagnetic field, heat conduction, and biological tissue, thus constructing a numerical model for single-needle multi-point microwave ablation. S2. Perform ablation simulation using a single-needle multi-point microwave ablation numerical model, output multi-point ablation result data, quantify the size and shape of the coagulation zone, and perform spatial overlap analysis on the isosurface in the multi-point ablation result data to obtain the characteristics of the coagulation zone; S3. By setting multiple antenna pullback distance and ablation time parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model, and combined with analysis of the characteristics of the coagulation zone, the optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment.

2. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 1, characterized in that: Said S1 comprises the following steps: S101. Construct a cylindrical liver tumor model based on a preset radius and height, establish a three-dimensional coordinate system with the microwave antenna's emission point as the center of the circle, insert the microwave antenna longitudinally from the center of the cylinder's bottom at a preset insertion depth, and establish a finite element simulation model. S102. Based on the interaction between electromagnetic fields, heat conduction, and biological tissues, the electromagnetic field is calculated using the Helmholtz harmonic equation. Combined with the specific absorption rate and the Pennes bioheat transfer equation, the finite element simulation model is solved to construct a single-needle multi-point microwave ablation numerical model.

3. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 2, characterized in that: The finite element simulation model is used to simulate the pullback process between microwave antennas in microwave ablation clinical surgery, and includes: a first simulation model and a second simulation model; The first simulation model is used to simulate the first ablation process, including the first heating process and the cooling process; The second simulation model is constructed based on the temperature parameters generated during the cooling process of the first simulation model, and is used to simulate the second ablation process.

4. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 3, characterized in that: The S2 comprises the following steps: S201. Performing ablation simulation using a single-needle multi-point microwave ablation numerical model, and using a specific heat capacity function based on water content variation and a linearly varying thermal conductivity function to describe thermal and electrical parameters of the simulated liver tissue in the single-needle multi-point microwave ablation numerical model, and outputting multi-point ablation result data; S202. Based on the multi-point ablation results data, the isotherm threshold method is used to assess the degree of tumor necrosis and characterize the size and morphology of the coagulation zone; S203 . Based on the characterized multi-point ablation result data, spatially overlap the isosurfaces and quantify the coagulation zone to obtain the characteristics of the coagulation zone.

5. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 4, characterized in that: The multi-point ablation result data includes a first simulation model ablation result and a second simulation model ablation result; In the step S203 , spatial overlap analysis is performed on the isosurfaces, specifically by spatially overlapping the coagulation zone generated in the ablation result of the first simulation model with the coagulation zone generated in the ablation result of the second simulation model.

6. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 3, characterized in that: The S3 includes the following steps: S301, based on constant power and total ablation time, setting different antenna pullback distances and first and second ablation times, and combining them into a parameter combination; S302. Based on various parameter combinations, ablation simulation is performed using a single-needle multi-point microwave ablation numerical model to obtain the effect of the antenna pullback distance on the morphological characteristics of the coagulation zone and the effect of the first ablation process on the coagulation area. S303. Based on the influence of the antenna pullback distance on the morphological characteristics of the coagulation zone and the influence of the first ablation process on the coagulation area, and combined with the characteristics of the coagulation zone, an optimal parameter combination is obtained to complete the numerical simulation of large tumor treatment.

7. The numerical simulation method for treating large tumors with single-needle multi-point microwave ablation according to claim 6, characterized in that: The effect of the antenna pull-back distance on the morphological characteristics of the solidification zone is specifically as follows: the larger the antenna pull-back distance, the longer the long axis of the solidification zone; The effect of the first ablation process on the coagulation area is specifically as follows: the longer the first ablation process is, the larger the coagulation area is.

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