WO2024078415A1

WO2024078415A1 - Thermal ablation system, and method for controlling flowing medium in thermal ablation system

Info

Publication number: WO2024078415A1
Application number: PCT/CN2023/123384
Authority: WO
Inventors: 王逸飞; 张爱丽
Original assignee: 上海美杰医疗科技有限公司
Priority date: 2022-10-09
Filing date: 2023-10-08
Publication date: 2024-04-18
Also published as: CN115530962A; WO2024077704A1

Abstract

The present application relates to the field of thermal ablation systems and control thereof. Disclosed are a thermal ablation system and a method for controlling a flowing medium in a thermal ablation system. The thermal ablation system comprises: a radio frequency ablation probe, a pressurized liquid nitrogen source, and a heat-exchange evaporation unit connected between the ablation probe and the pressurized liquid nitrogen source, the heat-exchange evaporation unit being provided with a gas-liquid separator. The method comprises: adjusting the rear-end flow resistance of the gas-liquid separator so as to control the temperature of nitrogen gas flowing into the ablation probe to be within a preset temperature range; and measuring the tip temperature of the ablation probe, and, according to the obtained tip temperature and a set radio frequency power, adjusting the rear-end flow resistance of the ablation probe until the tip temperature reaches a target temperature. The embodiments of the present application can avoid tissue carbonization caused by high ambient temperatures of probes while providing a larger ablation range.

Description

Thermal ablation system and method for controlling flow medium in thermal ablation system

Technical Field

The present application relates to the field of thermal ablation systems and control thereof, and in particular to a control method and system for a flow medium in a thermal ablation system.

Background technique

Thermal ablation is mainly divided into radiofrequency ablation and microwave ablation. If the thermal ablation system does not introduce a flowing medium, the biggest impact on radiofrequency ablation is that the tissue around the probe will quickly dehydrate and carbonize during the ablation process, thereby cutting off the radiofrequency circuit, making it impossible to continue radiofrequency ablation and incomplete ablation of the target lesion. Microwave ablation also faces the problem of carbonized tissue affecting ablation efficiency. At the same time, carbonized tissue adheres to the ablation probe, which may cause tissue tearing, which is not conducive to withdrawal after the treatment is completed. In addition, the microwave probe has severe self-heating and is easy to burn normal tissue near the needle track.

The commonly used flow medium at present is physiological saline driven by a peristaltic pump, and some devices also use high-pressure gas as the flow medium inside the ablation probe. For example, an existing solution 1 that uses a peristaltic pump to drive physiological saline as the flow medium has the advantage that physiological saline is simple and easy to obtain, but the parameters of the peristaltic pump are usually fixed, and the speed cannot be adjusted according to the ablation power and tissue state, and the protection ability for biological tissue is insufficient. The area of tissue dehydration and carbonization is only about 2 mm away from the surface of the ablation probe, and the effect of expanding the ablation range is insufficient. For example, an existing solution 2 that uses high-pressure gas as the flow medium inside the microwave ablation probe has the advantage that it has a stronger protection ability for biological tissue and can produce a larger ablation range than technical solution 1, but there is no mature control solution, but the disadvantage is that it relies on a manual valve to adjust the gas pressure, and there is still severe tissue carbonization in the area where the ablation probe head is not cooled, and even the ablation probe is burned out.

In addition, the prior art also discloses a method of using high pressure gas as the flow inside the radiofrequency ablation probe. The existing solution 3 of the dynamic medium needs to use the throttling principle to control the size of the freezing power. The advantage is that it is highly controllable, but the gas pressure under the throttling principle is usually higher than 2MPa, and certain transportation and storage qualifications are required. At the same time, the throttling principle has the problems of slow cooling and complex equipment, requiring a lot of time for pre-cooling, and the equipment cost is also high. In addition, the paper "Control Mode of a New Air-Cooled Radiofrequency Ablation System" proposed based on the existing solution 3 only describes the use of conventional PID algorithm to control the probe temperature at 80℃-90℃ during the radiofrequency process. The described system has large hysteresis and low precision, and there is still a problem of large amounts of carbonization of tissue around the probe.

Summary of the invention

The purpose of the present application is to provide a thermal ablation system and a method for controlling a flow medium in the thermal ablation system, so as to avoid tissue carbonization caused by high temperature around the probe while providing a larger ablation range.

The present application discloses a method for controlling a flow medium in a thermal ablation system, wherein the thermal ablation system comprises a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source, wherein the heat exchange evaporation unit is provided with a gas-liquid separator;

The control method comprises:

A. adjusting the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen gas flowing into the ablation probe to remain within a predetermined temperature range;

B detects the head temperature of the ablation probe, and adjusts the rear end flow resistance of the ablation probe according to the detected head temperature and the set radio frequency power so that the head temperature reaches the target temperature.

In a preferred example, the predetermined temperature range is -140°C to -130°C, and the target temperature is between 0°C and -40°C.

In a preferred embodiment, step B further comprises:

Detecting the head temperature of the ablation probe, and calculating the rear end flow rate of the ablation probe using the first and second formulas according to the detected head temperature, the set radio frequency power and the target temperature The control voltage of the regulating device is generated and output to the control end of the flow regulating device at the rear end of the ablation probe to adjust the rear end flow resistance of the ablation probe; wherein,

The first formula is:

The second formula is: error _N = TT _set ;

Among them, error _N is the temperature error at the current moment, k _P is the power term proportionality coefficient, k _T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set RF power, T _set is the target temperature, and V is the control voltage of the rear end flow regulating device of the ablation probe.

In a preferred embodiment, step A further comprises:

detecting the nitrogen temperature of the ablation probe;

When the detected nitrogen temperature is lower than a first threshold, the flow regulating device at the rear end of the gas-liquid separator is closed or the voltage applied to the flow regulating device is reduced; when the detected nitrogen temperature is higher than a second threshold, the flow regulating device at the rear end of the gas-liquid separator is opened and/or the voltage applied to the flow regulating device is increased to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold and the second threshold.

In a preferred embodiment, it also includes:

Steps A to B are performed in real time or periodically to keep the head temperature at the target temperature.

The present application also discloses a thermal ablation system, which includes a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source, wherein the heat exchange evaporation unit is provided with a gas-liquid separator;

The thermal ablation system further comprises:

A first flow resistance control unit, configured to adjust the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen gas flowing into the ablation probe to be maintained within a predetermined temperature range;

The second flow resistance control unit is configured to detect the head temperature of the ablation probe and The measured head temperature and the set radio frequency power are used to adjust the rear end flow resistance of the ablation probe so that the head temperature reaches the target temperature.

In a preferred example, the second flow resistance control unit includes a second temperature detection device, a second voltage adjustment module and a second flow adjustment device arranged at the rear end of the ablation probe;

The second temperature detection device is configured to detect the head temperature of the ablation probe;

The second voltage adjustment module is configured to calculate the control voltage of the second flow regulating device using the first and second formulas according to the detected head temperature of the ablation probe, the set RF power and the target temperature, and generate and output the control voltage to the control end of the first flow regulating device to adjust the rear end flow resistance of the ablation probe, wherein the first formula is The second formula is error _N = TT _set , where error _N is the temperature error at the current moment, k _P is the power term proportionality coefficient, k _T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set RF power, T _set is the target temperature, and V is the control voltage of the second flow regulating device.

In a preferred example, the first flow resistance control unit includes a first temperature detection device, a first voltage adjustment module and a first flow regulating device arranged at the rear end of the gas-liquid separator;

The temperature detection device is configured to detect the nitrogen temperature of the ablation probe;

The first voltage adjustment module is configured to close the first flow regulating device or reduce the control voltage applied to the first flow regulating device when the detected nitrogen temperature is lower than a first threshold value, and to open the flow regulating device at the rear end of the gas-liquid separator and/or increase the control voltage applied to the first flow regulating device when the detected nitrogen temperature is higher than a second threshold value, so as to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold value and the second threshold value.

In a preferred example, the first flow resistance control unit and the second flow resistance control unit are executed alternately and periodically to keep the head temperature at the target temperature.

The embodiments of the present application include at least the following advantages and beneficial effects:

During the radiofrequency ablation process, liquid nitrogen is used to evaporate into low-temperature nitrogen gas through phase change. By controlling the flow of low-temperature nitrogen gas in the system, the temperature around the ablation probe is stabilized within a predetermined temperature range below zero. Compared with the traditional technical solution, it can simultaneously solve the problems of expanding the ablation range, avoiding tissue carbonization and tissue adhesion to the probe, and is cheap and easy to obtain. Conventional water circulation generally requires above 0°C. Too low a temperature will cause ice to form around the ablation probe, affecting the output of radiofrequency energy, causing the ablation process to be unexpectedly interrupted and incomplete. Therefore, compared with water circulation, the embodiment of the present application can control the temperature of the ablation probe at 0°C to -40°C, absorb more excess heat, delay the occurrence of tissue carbonization, obtain a larger ablation range, and help to better solve the above problems. This is known through theoretical analysis and experiments. Therefore, the embodiment of the present application can achieve a larger ablation range than technical solution 1, and better controllability than technical solution 2.

Furthermore, an improved radiofrequency ablation control algorithm is proposed for the characteristics of the large hysteresis system of the internal cooling cycle radiofrequency ablation, which can quickly control and/or maintain the low-temperature nitrogen obtained by phase change at a predetermined temperature below zero, and the method has small overshoot and fluctuation. Therefore, compared with technical solution 3, the improved control algorithm proposed in the embodiment of the present application can better deal with the problem of large hysteresis of such systems, with small overshoot and high precision, and because the low-temperature nitrogen is obtained from the evaporation of liquid nitrogen, it is cheap and easy to obtain.

The specification of this application records a large number of technical features, which are distributed in various technical solutions. If all possible combinations of technical features (i.e., technical solutions) of this application are to be listed, the specification will be too lengthy. In order to avoid this problem, the various technical features disclosed in the above invention content of this application, the various technical features disclosed in the various implementation modes and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions are deemed to have been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, features A+B+C are disclosed, and in another example, features A+B+C are disclosed. Features A+B+D+E are disclosed in the patent application, and features C and D are equivalent technical means that play the same role. Technically, only one of them needs to be used, and it is impossible to use them at the same time. Feature E can be technically combined with feature C. In this case, the solution of A+B+C+D should not be regarded as having been recorded because it is technically not feasible, while the solution of A+B+C+E should be regarded as having been recorded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a thermal ablation system according to a first embodiment of the present application;

2 is a schematic flow chart of a method for controlling a flowing medium in a thermal ablation system according to a second embodiment of the present application;

FIG3 is a schematic flow chart of a method for controlling a flowing medium in thermal ablation according to an embodiment of the present application;

FIG4 is a diagram showing the control result of the voltage controlled by the proportional valve at the rear end of the probe and the temperature control of the needle tip according to an embodiment of the present application;

FIG. 5 is a diagram showing changes in the control voltage of the proportional valve at the rear end of the gas-liquid separator and the temperature of the nitrogen inlet according to an embodiment of the present application.

Detailed ways

In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

In order to make the objectives, technical solutions and advantages of the present application more clear, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

The first embodiment of the present application relates to a thermal ablation system, as shown in FIG1 . The system includes a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source. Among them, the pressure liquid nitrogen source refers to a liquid nitrogen container with a certain pressure, and the role of the pressure is to make the liquid nitrogen flow to the ablation probe through the pipeline. Liquid nitrogen is liquid nitrogen, which has the characteristic of low temperature. Under normal pressure, the temperature of liquid nitrogen is -196°C. The heat exchange evaporation unit is, for example but not limited to, a pipeline connecting the ablation probe and the pressure liquid nitrogen source. What flows into the heat exchange evaporation unit is liquid nitrogen, and what flows out of the heat exchange evaporation unit is low-temperature nitrogen. After the liquid nitrogen evaporates, it turns into nitrogen gas, which produces huge flow resistance, causing the liquid nitrogen flow to slow down or even stop, the heat exchange time is too long, and the temperature is too high after reaching the ablation probe. Therefore, the heat exchange evaporation unit also includes a gas-liquid separator, which controls the liquid nitrogen flow rate by adjusting the flow resistance at the rear end of the gas-liquid separator, thereby ensuring that the nitrogen entering the ablation probe has a sufficiently low temperature.

Optionally, the thermal ablation system further includes a control unit, which includes a first flow resistance control unit and a second flow resistance control unit. The first flow resistance control unit is configured to adjust the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen flowing into the ablation probe to remain within a predetermined temperature range. Optionally, the first flow resistance control unit includes a first temperature detection device, a first voltage adjustment module, and a first flow regulating device arranged at the rear end of the gas-liquid separator, wherein the first temperature detection device is configured to detect the nitrogen temperature of the ablation probe, and the first voltage adjustment module is configured to close the flow regulating device at the rear end of the gas-liquid separator or reduce the control voltage applied to the first flow regulating device when the detected nitrogen temperature is less than a first threshold value, and to open the flow regulating device at the rear end of the gas-liquid separator and/or increase the control voltage applied to the first flow regulating device when the detected nitrogen temperature is greater than a second threshold value, so as to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold value and the second threshold value. For example, in one embodiment, the first flow resistance control unit includes a temperature measuring device arranged at the liquid nitrogen inlet and a flow regulating device at the rear end of the gas-liquid separator. The temperature measuring device may be, but is not limited to, a thermocouple. The first flow regulating device may be a proportional valve, or a solenoid valve, a hand valve, or other flow control device and structure. For example, the first flow regulating device is a proportional valve. In one embodiment, when the temperature measured by the thermocouple at the liquid nitrogen inlet is higher than -130°C, it is considered that the nitrogen temperature is too high; when the temperature measured by the thermocouple at the liquid nitrogen inlet is lower than -140°C, it is considered that the nitrogen temperature is too low. At this time, the proportional valve at the rear end of the gas-liquid separator is closed. valve, that is, the applied voltage is 0V.

Further, the second flow resistance control unit is configured to detect the head temperature of the ablation probe, and adjust the rear end flow resistance of the ablation probe according to the detected head temperature and the set radio frequency power, so that the head temperature is the target temperature. Optionally, the second flow resistance control unit includes a second temperature detection device, a second voltage adjustment module and a second flow regulating device arranged at the rear end of the ablation probe. The second temperature detection device is configured to detect the head temperature of the ablation probe; the second voltage adjustment module is configured to calculate the control voltage of the second flow regulating device according to the detected head temperature of the ablation probe, the set radio frequency power and the target temperature using the first and second formulas and generate and output the control voltage to the control end of the second flow regulating device to adjust the rear end flow resistance of the ablation probe, wherein the first formula is The second formula is error _N = TT _set , where error _N is the temperature error at the current moment, k _P is the power term proportionality coefficient, k _T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set RF power, T _set is the target temperature, and V is the control voltage of the second flow regulating device.

The second temperature detection device is integrated into the ablation probe head, for example but not limited to a thermocouple, buried inside the ablation probe, so that the comprehensive thermal effect of the internal flow medium and thermal ablation can be measured.

Optionally, the first flow resistance control unit and the second flow resistance control unit are executed alternately and periodically to keep the head temperature at the target temperature.

In one embodiment, the system adjusts the flow resistance at the rear end of the ablation probe by detecting the temperature value obtained by the second flow resistance control unit, thereby controlling the flow rate of low-temperature nitrogen to control the temperature of the nitrogen flowing into the ablation probe to be maintained within a predetermined temperature range of -140°C to -130°C. If the first flow resistance control unit detects that the nitrogen temperature is not low enough, the flow resistance at the rear end of the gas-liquid separator will be adjusted to control the temperature of the ablation probe within a target temperature range of 0°C to -40°C. In other embodiments, the predetermined temperature range and the target temperature range may also be other values, such as those obtained from pipeline structure experiments.

The second embodiment of the present application relates to a method for controlling a flow medium in a thermal ablation system. The thermal ablation system includes a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source. The heat exchange evaporation unit is provided with a gas-liquid separator. The control method flow is shown in FIG2. The control method includes the following steps:

Step 201, adjusting the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen gas flowing into the ablation probe to be maintained within a predetermined temperature range;

Step 202, detecting the head temperature of the ablation probe, and adjusting the rear end flow resistance of the ablation probe according to the detected head temperature and the set radio frequency power, so that the head temperature reaches the target temperature.

Optionally, the predetermined temperature range is -140°C to -130°C, and the target temperature is a temperature value between 0°C and -40°C.

Optionally, step 202 may further include: detecting the head temperature of the ablation probe, and using a first formula according to the detected head temperature, the set radio frequency power and the target temperature: The control voltage of the rear flow regulating device of the ablation probe is calculated with the second formula error _N = TT _set , and the control voltage is generated and output to the control end of the rear flow regulating device of the ablation probe to adjust the rear flow resistance of the ablation probe. Wherein error _N is the temperature error at the current moment, k _P is the power term proportionality coefficient, k _T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set radio frequency power, T _set is the target temperature, and V is the control voltage of the rear flow regulating device of the ablation probe.

Optionally, step 201 further includes the following steps 201a and 201b:

Step 201a, detecting the nitrogen temperature of the ablation probe;

Step 201b, when the detected nitrogen temperature is lower than the first threshold, the flow regulating device at the rear end of the gas-liquid separator is closed or the voltage applied to the flow regulating device is reduced; when the detected nitrogen temperature is higher than the second threshold, the flow regulating device at the rear end of the gas-liquid separator is opened and/or the voltage applied to the flow regulating device is increased to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold and the second threshold.

Optionally, the control method further includes: executing steps 201 to 202 in real time or periodically to keep the head temperature at the target temperature.

In order to better understand the beneficial effects of the present application, the following is an example of heating an ex vivo pig liver with a radiofrequency ablation probe at a power of 60W to control the temperature of the ablation probe between 0°C and -40°C, as shown in FIG3, including the following steps:

Step 301: First, open the valve of the liquid nitrogen tank, the pressure of which is between 0.8MPa and 1.2MPa. Driven by pressure, liquid nitrogen flows through the pipeline connecting the ablation probe and the pressure liquid nitrogen source, and evaporates into low-temperature nitrogen through heat exchange. There is a gas-liquid separator in the pipeline, and the liquid nitrogen flow rate is controlled by adjusting the flow resistance at the rear end of the gas-liquid separator, thereby ensuring that the nitrogen entering the ablation probe has a sufficiently low temperature. Adjusting the flow resistance of the gas-liquid separator is to adjust the control voltage of the proportional valve at the rear end of the gas-liquid separator.

Step 302: The temperature measured by the thermocouple at the tip of the radiofrequency ablation needle is obtained and stored in a storage medium, and read in real time by a program.

Step 303: In this embodiment, the target tip temperature of the RF ablation needle is set between 0°C and -40°C. The set RF ablation power P and the RF ablation needle tip temperature T obtained in step 302 are used as inputs, and the control voltage of the proportional valve at the rear end of the ablation probe is calculated using the following control equation:

error _N = T + 15 error _N = TT _set

Wherein, V is the calculated control voltage of the proportional valve at the rear end of the ablation probe, _kP is the proportional coefficient of the power term, _kT is the proportional coefficient of the temperature term, _errorN is the temperature error at the current moment, and _Tset is the target tip temperature of the radiofrequency ablation needle. In this embodiment, the relationship between the control voltage V of the proportional valve at the rear end of the ablation probe and the tip temperature T of the radiofrequency ablation needle is shown in FIG4.

Step 304: applying the voltage V calculated in step 303 to the proportional valve at the rear end of the ablation probe, and the flow rate of nitrogen in the ablation probe is between 0 and 100 L/min.

Step 305, determine whether the nitrogen temperature is low enough. In this embodiment, when the liquid nitrogen inlet is hot When the temperature measured by the thermocouple is higher than -130℃, the nitrogen temperature is considered to be too high; when the temperature measured by the thermocouple at the liquid nitrogen inlet is lower than -140℃, the nitrogen temperature is considered to be too low. At this time, the proportional valve at the rear end of the gas-liquid separator is closed, that is, the applied voltage is 0V.

Step 306: When it is determined in step 305 that the nitrogen temperature is too high, it is necessary to open the proportional valve at the rear end of the gas-liquid separator in step 301. In this embodiment, the voltage applied to the proportional valve at the rear end of the gas-liquid separator is 1V. The voltage can also be other values. The values in this embodiment are obtained based on pipeline structure experiments. The control voltage of the proportional valve at the rear end of the gas-liquid separator and the change of the nitrogen inlet temperature are shown in Figure 5.

Through the analysis and experiments of this embodiment, it can be learned that while achieving a larger ablation range, the temperature of the ablation probe can be quickly stabilized at a target temperature value within a certain temperature range of 0°C to -40°C, with a maximum overshoot within 3°C and a fluctuation less than ±0.5°C after stabilization, thereby avoiding overcooling or overheating around the ablation probe and achieving the purpose of controlling the ablation range.

The first implementation manner is a method implementation manner corresponding to the present implementation manner. The technical details in the first implementation manner can be applied to the present implementation manner, and the technical details in the present implementation manner can also be applied to the first implementation manner.

It should be pointed out that the ablation probe in the present application can be a needle type, a flat head type, or other types. The flow regulating device can be a proportional valve, or a solenoid valve, a hand valve, or other devices and structures for controlling flow. The temperature measurement unit can be a thermocouple built into the ablation probe, or an optical fiber, an external thermocouple, or non-contact MR, ultrasonic temperature measurement, etc. In addition, the present application can use the proposed improved temperature control algorithm, or can use PID control, sliding mode control, fuzzy control, neural network, genetic algorithm, predictive control, quadratic optimal control, time delay control, and adaptive control algorithms based on uncertain disturbance estimation. In addition, the input of the control unit of the present application can be temperature, and can also additionally input flow, pressure, thermal ablation output power and tissue impedance. The output can be a target flow, or can simultaneously control the target output power, target pressure, and target tissue impedance of thermal ablation.

It should be noted that the embodiments of the present invention are not limited to any specific combination of hardware and software. In the application documents of this patent, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

A method for controlling a flow medium in a thermal ablation system, characterized in that the thermal ablation system comprises a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source, wherein the heat exchange evaporation unit is provided with a gas-liquid separator;

The control method comprises:

A. adjusting the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen gas flowing into the ablation probe to remain within a predetermined temperature range;

B detects the head temperature of the ablation probe, and adjusts the rear end flow resistance of the ablation probe according to the detected head temperature and the set radio frequency power so that the head temperature reaches the target temperature.
The control method according to claim 1 is characterized in that the predetermined temperature range is -140°C to -130°C, and the target temperature is between 0°C and -40°C.
The control method according to claim 1, characterized in that step B further comprises:

Detecting the head temperature of the ablation probe, using the first and second formulas to calculate the control voltage of the rear end flow regulating device of the ablation probe according to the detected head temperature, the set radio frequency power and the target temperature, and generating and outputting the control voltage to the control end of the flow regulating device at the rear end of the ablation probe to adjust the rear end flow resistance of the ablation probe; wherein,

The first formula is:

The second formula is: error N = TT set ;

Among them, error N is the temperature error at the current moment, k P is the power term proportionality coefficient, k T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set RF power, T set is the target temperature, and V is the control voltage of the rear end flow regulating device of the ablation probe.
The control method according to claim 1, characterized in that step A further comprises:

detecting the nitrogen temperature of the ablation probe;

When the detected nitrogen temperature is lower than a first threshold, the flow regulating device at the rear end of the gas-liquid separator is closed or the voltage applied to the flow regulating device is reduced; when the detected nitrogen temperature is higher than a second threshold, the flow regulating device at the rear end of the gas-liquid separator is opened and/or the voltage applied to the flow regulating device is increased to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold and the second threshold.
The control method according to any one of claims 1 to 4, further comprising:

Steps A to B are performed in real time or periodically to keep the head temperature at the target temperature.
A thermal ablation system, characterized in that the thermal ablation system comprises a radiofrequency ablation probe, a pressure liquid nitrogen source, and a heat exchange evaporation unit connected between the ablation probe and the pressure liquid nitrogen source, wherein the heat exchange evaporation unit is provided with a gas-liquid separator;

The thermal ablation system further comprises:

A first flow resistance control unit, configured to adjust the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen gas flowing into the ablation probe to be maintained within a predetermined temperature range;

The second flow resistance control unit is configured to detect the head temperature of the ablation probe, and adjust the rear end flow resistance of the ablation probe according to the detected head temperature and the set radio frequency power so that the head temperature is the target temperature.
The thermal ablation system according to claim 6, characterized in that the predetermined temperature range is -140°C to -130°C, and the target temperature is between 0°C and -40°C.
The thermal ablation system according to claim 6, characterized in that the second flow resistance control unit includes a second temperature detection device, a second voltage adjustment module and a second flow adjustment device arranged at the rear end of the ablation probe;

The second temperature detection device is configured to detect the head temperature of the ablation probe;

The second voltage adjustment module is configured to adjust the voltage according to the detected head temperature of the ablation probe, The set RF power and the target temperature are calculated using the first and second formulas to calculate the control voltage of the second flow regulating device and generate and output the control voltage to the control end of the first flow regulating device to adjust the rear end flow resistance of the ablation probe, wherein the first formula is The second formula is error N = TT set , where error N is the temperature error at the current moment, k P is the power term proportionality coefficient, k T is the temperature term proportionality coefficient, T is the detected head temperature, P is the set RF power, T set is the target temperature, and V is the control voltage of the second flow regulating device.
The thermal ablation system according to claim 6, characterized in that the first flow resistance control unit includes a first temperature detection device, a first voltage adjustment module and a first flow regulating device arranged at the rear end of the gas-liquid separator;

The temperature detection device is configured to detect the nitrogen temperature of the ablation probe;

The first voltage adjustment module is configured to close the first flow regulating device or reduce the control voltage applied to the first flow regulating device when the detected nitrogen temperature is lower than a first threshold value, and to open the flow regulating device at the rear end of the gas-liquid separator and/or increase the control voltage applied to the first flow regulating device when the detected nitrogen temperature is higher than a second threshold value, so as to control the temperature of the nitrogen flowing into the ablation probe to remain within the predetermined temperature range between the first threshold value and the second threshold value.
The thermal ablation system according to any one of claims 6 to 9, characterized in that the first flow resistance control unit and the second flow resistance control unit are executed alternately and periodically to keep the head temperature at the target temperature.