阅读说明：本技术 一种用于肝脏的微波消融碳化调控方法 (Microwave ablation carbonization regulation and control method for liver ) 是由 蔡惠明 钱志余 冯宇 方舟 晋晓飞 于 2020-06-23 设计创作，主要内容包括：本发明公开了一种用于肝脏的微波消融碳化调控方法,包括以下步骤：S1、肝脏微波消融仿真模型构建,采用二维轴对称组件进行消融针、肝脏仿真几何模型构建；S2、电磁辐射与生物热传导参数设置；S3、输入功率与时间的调频调幅函数,设定消融时间,开始仿真消融；S4、对仿真数据可视化处理,绘制仿真全过程温度场图像；S5、搭建离体肝脏微波消融系统,开始消融；S6、对比实验结果与仿真结果以进行判断。该方法能够实现消融体积大,消融时间短的消融过程,并且达到少碳化、甚至无碳化的消融治疗效果。(The invention discloses a microwave ablation carbonization regulation and control method for a liver, which comprises the following steps: s1, constructing a liver microwave ablation simulation model, and constructing an ablation needle and a liver simulation geometric model by adopting a two-dimensional axisymmetric assembly; s2, setting parameters of electromagnetic radiation and biological heat conduction; s3, inputting a frequency modulation and amplitude modulation function of power and time, setting ablation time, and starting simulation ablation; s4, performing visualization processing on the simulation data, and drawing a simulation whole-process temperature field image; s5, building an in-vitro liver microwave ablation system and starting ablation; and S6, comparing the experimental result with the simulation result for judgment. The method can realize the ablation process with large ablation volume and short ablation time, and achieve the ablation treatment effect of little carbonization and even no carbonization.)

1. A microwave ablation carbonization regulation and control method for liver is characterized by comprising the following steps:

s1, constructing a liver microwave ablation simulation model, constructing an ablation needle and a liver simulation geometric model by adopting a two-dimensional axisymmetric assembly, selecting the two-dimensional axisymmetric assembly, setting the length unit as mm, and constructing the liver ablation model;

s2, setting parameters of electromagnetic radiation and biological heat conduction;

s3, inputting a frequency modulation and amplitude modulation function of power and time, setting ablation time, and starting simulation ablation;

s4, performing visual processing on the simulation data to obtain temperature field distribution data, and drawing a simulation whole-process temperature field image;

s5, constructing an in-vitro liver microwave ablation system, enabling an upper computer to realize the output of a microwave ablation continuous mode and a frequency modulation and amplitude modulation mode, setting an output mode consistent with the simulation optimal function model for the microwave source power, and starting ablation;

and S6, comparing the experimental result with the simulation result to judge, and continuing to judge by taking the ablation major diameter error as less than or equal to +/-5 mm, the ablation minor diameter as less than or equal to +/-3 mm and the maximum width error of the carbonization area as a standard, wherein if the standard is met, the frequency modulation and amplitude modulation model is effective, and if the standard is not met, the function model needs to be corrected until the standard is met.

2. The microwave ablation carbonization regulating method for liver as claimed in claim 1, wherein the step S1 includes the steps of:

s11, carrying out simulation design on the ablation needle according to the structure of a KY-2450A ablation needle, wherein the needle body comprises a puncture head, a stainless steel sleeve, a coaxial cable and an insulating medium sleeve, and the coaxial cable comprises an inner conductor, an insulating medium and an outer conductor;

s12, the inner conductors of the puncture head and the coaxial cable are combined into a domain by the simplified model, the insulating medium and the insulating medium sleeve of the coaxial cable are combined into a domain, the liver is a domain, and the other domains are set as the boundaries of ideal electric conductors to construct a two-dimensional axisymmetric model liver microwave ablation geometric figure.

3. The microwave ablation carbonization regulating method for liver as claimed in claim 1, wherein the step S2 includes the steps of:

s21, the electromagnetic radiation field includes a liver and an ablation needle material portion,firstly, setting constant pressure heat capacity Cp, heat conductivity coefficient kappa, density rho and relative dielectric constant of liver_rThe conductivity 0 is respectively:

κ＝0.512 293.15≤T≤473.15

293.15≤T≤403.15

293.15≤T≤473.15；

s22, setting parameters of ablation needle material_PTFE＝2，σ_PTFE＝0；

S23, setting the boundary temperature T of the inner conductor, the outer conductor and the stainless steel sleeve of the ablation needle₀293.15, the ablation water cooling effect was simulated.

4. The microwave ablation carbonization regulating method for liver as claimed in claim 1, wherein the step S4 includes the steps of:

and S41, drawing isothermal lines of 55 degrees and 130 degrees, and correcting the function model according to the carbonization degree of the ablation region.

Technical Field

The invention relates to the field of medical treatment, in particular to a microwave ablation carbonization regulation and control method for a liver.

Background

The microwave thermal ablation technology has the advantages of high temperature, strong tissue penetrability, large ablation range, minimal invasion, realization of multi-point ablation and the like, and is widely used for treating solid tumors such as liver cancer, lung cancer, kidney cancer and the like. Microwave ablation is incorporated into the international (NCCN) and domestic guidelines for tumor therapy by conventional tumor therapy techniques, and more than 500 hospitals across the country are in clinical use. The current clinical treatment of microwave ablation can cause the tissue in the central area of ablation to be carbonized due to high temperature, and the formation of the carbonized area can cause some side effects on the ablation effect, including: the carbonization area is adhered to the ablation needle, and secondary damage is caused to liver tissues when the ablation needle is pulled out; the carbonized area can block the heat transmission of the antenna and limit the range of ablation therapy; the carbonized tissue left in the human body can cause the postoperative fever and inflammation of the patient. At present, no good carbonization regulation and control technology exists, so how to realize little carbonization or even no carbonization of a microwave ablation region of a patient based on control of microwave transmission power and timely adjustment according to result feedback is a problem to be solved urgently.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a microwave ablation carbonization regulation and control method for livers, and the following technical scheme is adopted for solving the technical problems:

a microwave ablation carbonization regulation and control method for liver comprises the following steps:

s1, constructing a liver microwave ablation simulation model, constructing an ablation needle and a liver simulation geometric model by adopting a two-dimensional axisymmetric assembly, selecting the two-dimensional axisymmetric assembly, setting the length unit as mm, and constructing the liver ablation model;

s2, setting parameters of electromagnetic radiation and biological heat conduction;

s3, inputting a frequency modulation and amplitude modulation function of power and time, setting ablation time, and starting simulation ablation;

s4, performing visual processing on the simulation data to obtain temperature field distribution data, and drawing a simulation whole-process temperature field image;

s5, constructing an in-vitro liver microwave ablation system, enabling an upper computer to realize the output of a microwave ablation continuous mode and a frequency modulation and amplitude modulation mode, setting an output mode consistent with the simulation optimal function model for the microwave source power, and starting ablation;

and S6, comparing the experimental result with the simulation result to judge, and continuing to judge by taking the ablation major diameter error as less than or equal to +/-5 mm, the ablation minor diameter as less than or equal to +/-3 mm and the maximum width error of the carbonization area as a standard, wherein if the standard is met, the frequency modulation and amplitude modulation model is effective, and if the standard is not met, the function model needs to be corrected until the standard is met.

Preferably, step S1 includes the steps of:

s11, carrying out simulation design on the ablation needle according to the structure of a KY-2450A ablation needle, wherein the needle body comprises a puncture head, a stainless steel sleeve, a coaxial cable and an insulating medium sleeve, and the coaxial cable comprises an inner conductor, an insulating medium and an outer conductor;

s12, the inner conductors of the puncture head and the coaxial cable are combined into a domain by the simplified model, the insulating medium and the insulating medium sleeve of the coaxial cable are combined into a domain, the liver is a domain, and the other domains are set as the boundaries of ideal electric conductors to construct a two-dimensional axisymmetric model liver microwave ablation geometric figure.

Preferably, step S2 includes the steps of:

s21, setting constant pressure heat capacity Cp, thermal conductivity к, density rho and relative dielectric constant of liver, wherein the electromagnetic radiation domain comprises liver and ablation needle material part_rThe electrical conductivity σ is:

κ＝0.512 293.15≦T≦473.15

293.15≦T≦403.15

293.15≦T≦473.15；

s22, setting parameters of ablation needle material_PTFE＝2，σ_PTFE＝0；

S23, setting the boundary temperature T of the inner conductor, the outer conductor and the stainless steel sleeve of the ablation needle₀293.15, the ablation water cooling effect was simulated.

Preferably, step S4 includes the steps of:

and S41, drawing isothermal lines of 55 degrees and 130 degrees, and correcting the function model according to the carbonization degree of the ablation region.

Compared with the prior art, the invention adopting the technical scheme has the following technical effects:

the frequency modulation and amplitude modulation mode is changed according to the carbonization degree feedback of the carbonization area of the ablation center, the process of heating the tissue is related to the structure of the tissue and the microwave power output, the most suitable frequency modulation and amplitude modulation mode is determined, the ablation process with large ablation volume and short ablation time can be realized, and the ablation treatment effect of little carbonization and even no carbonization can be achieved.

Drawings

Fig. 1 is a flow chart of a microwave ablation carbonization control method for liver according to the present invention;

FIG. 2 is a two-dimensional axisymmetric model liver microwave ablation geometry constructed in accordance with the present invention;

FIG. 3 is a graph of the results of a 60W ablation 600s simulation in a continuous mode of microwave ablation in accordance with the present invention;

FIG. 4 is a graph of the results of a 600s pig liver in vitro experiment using a continuous microwave ablation mode with 60W ablation according to the present invention;

FIG. 5 is a graph of the frequency and amplitude modulation mode and power output function of the microwave ablation simulation of the present invention;

FIG. 6 is a graph of the microwave ablation FM mode temperature field results of the present invention;

FIG. 7 is a graph showing the results of substantially no carbonization in the ablation center region in FM/AM mode of microwave ablation in accordance with the present invention;

FIG. 8 is a comparison graph of simulation results in the frequency modulation and amplitude modulation mode of microwave ablation and in-vitro microwave ablation experimental results.

Detailed Description

The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the present invention provides a flow chart of a microwave ablation carbonization control method for a liver, taking a two-dimensional simulation model of liver microwave ablation as an example, including the following steps:

s1, constructing a liver microwave ablation simulation model; through the COMSOL Multiphysics of many physics simulation software, adopt two-dimentional axial symmetry subassembly to melt needle, liver simulation geometric model and construct, include:

1. selecting a two-dimensional axisymmetric component, and setting the length unit as mm;

2. a liver ablation model is constructed and mainly comprises a liver and an ablation needle body. The ablation needle is designed in a simulation mode according to the structure of a KY-2450A ablation needle, the needle body comprises a puncture head (the front end is 11mm), a stainless steel sleeve (the diameter is 1.9mm), a coaxial cable (comprising an inner conductor, an insulating medium and an outer conductor) and an insulating medium sleeve (PTFE), the puncture head and the inner conductor of the coaxial cable are combined into a domain by a simplified model, the insulating medium and the insulating medium sleeve of the coaxial cable are combined into a domain, a liver is a domain, and the rest of the liver is set as an ideal electric conductor boundary to construct a two-dimensional axisymmetric model liver microwave ablation geometric figure, as shown in figure 2.

S2, setting electromagnetic radiation and biological heat conduction parameters, setting corresponding material parameters for the divided domains in S1, wherein the parameters are dynamic parameters changing along with the temperature T (K), and the parameters comprise:

1. the electromagnetic radiation domain comprises liver and PTFE material part, and the constant pressure heat capacity Cp, the thermal conductivity к, the density rho and the relative dielectric constant of the liver are firstly set_rThe electrical conductivity σ is:

κ＝0.512 293.15≦T≦473.15

2. setting ablation needle material (PTFE Polytetrafluoroethylene) parameters_PTFE＝2，σ_PTFE＝0；

3. Setting the boundary temperature T of the inner and outer conductors of the ablation needle and the stainless steel sleeve₀293.15, the ablation water cooling effect was simulated.

S3, inputting a frequency modulation and amplitude modulation function of power and time, setting ablation time, and starting simulated ablation, wherein the method comprises the following steps:

1. the top end of the ablation needle is provided with a microwave transmission port which is a coaxial port, and the microwave frequency is set to be 2450 MHz;

2. as shown in FIG. 5, a preset FM-AM function an4 is input to the electromagnetic field input port, and in the FM-AM power output mode, in the first 77s, the high power is 80W for 3s, the low power is 40W for 4s, the period T is 7s to realize rapid heating of the ablation region, in the last 77-600s, the high power is 65W for 3s, the low power is 25W for 4s, and the period T is 7s to keep the temperature to slowly heat the enlarged ablation region. The temperature of the ablation center is effectively controlled within a certain range.

The formula can be expressed as:

an1＝0*(t>＝0&&t<＝4)+1*(t>＝4&&t<＝7)

an2＝40*an1(t)+40

an3＝0*(t>＝0&&t<＝77)+(-15)*(t>＝77&&t<＝600)

an4＝an2(t)+an3(t)

3. adding a time domain research step, setting ablation time for 10min and step length for 1s, saving the solution per second, saving the result per second, and starting ablation.

S4, performing visual processing on the simulation data to obtain temperature field distribution data; drawing a simulation whole-process temperature field image, drawing isotherms of 55 degrees and 130 degrees, wherein the isotherms within the range of 55 degrees represent effective ablation volume, the central region higher than 130 degrees represents a carbonization region, and the function mathematical model is corrected according to the carbonization degree of the ablation region, namely, if the ablation central region has a larger carbonization region, the power output size, time and duty ratio of a frequency modulation and amplitude modulation mode need to be changed, and on the premise of ensuring larger ablation volume and shorter ablation time, better ablation treatment effects of no carbonization and less carbonization of the ablation central region are realized. Fig. 3 is a graph showing the results of a simulation of ablation 600s at 60W power in continuous mode. As shown in fig. 4, which is a graph of the experimental results of the microwave ablation continuous mode with 60W power ablation of 600s pig liver in vitro, the middle black part is a carbonization zone. As shown in fig. 6, ablation results were obtained at fm-am power mode an4 of fig. 5. Compared with the carbonization degree of the continuous mode ablation region in the figure 3, the continuous mode carbonization region has the maximum diameter of about 10mm, and the maximum diameter of about 6mm in the frequency modulation and amplitude modulation mode, so that the carbonization region of the ablation center is obviously and effectively reduced, and a better ablation effect is achieved. In the ablation mode, according to the carbonization temperature feedback modification function, in the first 105s, the high power is 48W for 3s, the low power is 23W for 4s, and the period T is 7s, the ablation region is rapidly heated, in the last 105s and 600s, the high power is 36W for 3s, the low power is 11W for 4s, and the period T is 7s, the temperature is kept for slowly heating and expanding the ablation region. Under the function an8, the ablation area is basically free of carbonization under a certain ablation volume, and the requirement that the maximum width of the ablation carbonization area is less than 6mm is met, as shown in fig. 7. The formula can be expressed as:

an5＝0*(t>＝0&&t<＝4)+1*(t>＝4&&t<＝7)

an6＝25*an5(t)+15

an7＝8*(t>＝0&&t<＝105)+(-4)*(t>＝105&&t<＝600)

an8＝an6(t)+an7(t)

s5, building an in-vitro liver microwave ablation system, enabling the upper computer to realize the output of a microwave ablation continuous mode and a frequency modulation and amplitude modulation mode, setting an output mode consistent with the simulation optimal function model for the microwave source power, and starting ablation.

S6, comparing the experimental result with the simulation result, and taking the ablation major diameter error less than or equal to +/-5 mm, the ablation minor diameter error less than or equal to +/-3 mm and the maximum width error of the carbonization area less than or equal to 2mm as the standard, if the standard is met, the frequency modulation and amplitude modulation model is effective; if the criterion is not met, the function model needs to be modified until the criterion is met.

The frequency modulation and amplitude modulation mode power output is subjected to an in-vitro liver microwave ablation experiment in a function an4 mode, and the obtained in-vitro experiment result and simulation result pair is shown in fig. 8, wherein the simulation ablation area has a long diameter of 4.2cm and a short diameter of 3.1cm, the maximum width of a carbonization area is about 6mm, the in-vitro pig liver microwave ablation experiment ablation area has a long diameter of 3.9cm, a short diameter of 2.8cm and a maximum width of a carbonization area is about 5mm, and the error standard is met. The maximum diameter of the carbonization area is about 10mm in the continuous mode, so that the carbonization of the ablation center area is reduced, and the ablation center is basically not carbonized under a certain volume of the ablation area in the frequency modulation and amplitude modulation mode.

Therefore, the frequency modulation and amplitude modulation mode is changed according to the feedback of the carbonization degree of the carbonization area of the ablation center, the ablation process with large ablation volume and short ablation time can be realized, and the ablation treatment effect of less carbonization and even no carbonization can be achieved.

The foregoing is only a preferred embodiment of the present invention; the scope of the invention is not limited thereto. Any person skilled in the art should be able to cover the technical scope of the present invention by equivalent or modified solutions and modifications within the technical scope of the present invention.