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

Abstract

The present application relates to the field of thermal ablation systems and their control, and discloses a thermal ablation system and a method for controlling a flow medium in the 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, wherein the heat exchange evaporation unit is provided with a gas-liquid separator; the control method includes: adjusting the rear end flow resistance of the gas-liquid separator to control the temperature of the nitrogen flowing into the ablation probe to be maintained within a predetermined temperature range; 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 radiofrequency power so that the head temperature is the target temperature. The embodiments of the present application avoid tissue carbonization caused by the high temperature around the probe while providing a larger ablation range.

Description

Technical Field

[0001] The present application relates to the field of thermal ablation systems and their control, and in particular to a method and system for controlling a flow medium in a thermal ablation system. Background Art

[0002] Thermal ablation is primarily categorized as radiofrequency ablation (RFA) and microwave ablation. If a thermal ablation system lacks a fluid medium, the greatest impact on RF ablation is rapid dehydration and carbonization of the tissue surrounding the probe during the ablation process, disrupting the RF circuit and preventing further RF ablation, resulting in incomplete ablation of the target lesion. Microwave ablation also faces the problem of carbonized tissue affecting ablation efficiency. Furthermore, carbonized tissue adheres to the ablation probe, potentially causing tissue tearing and hindering post-treatment withdrawal. Furthermore, microwave probes can experience significant self-heating, potentially burning normal tissue near the needle tract.

[0003] 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. In addition, the protection ability of biological tissue is insufficient, and the area of ​​tissue dehydration and carbonization is only about 2 mm away from the surface of the ablation probe, which is not enough to expand the ablation range. 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. However, 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 may burn out.

[0004] Additionally, the prior art discloses a method called "Solution 3," which uses high-pressure gas as the flow medium within the RF ablation probe. This method uses a throttling principle to control the cooling power. While this method offers the advantage of greater controllability, the gas pressure under this method is typically higher than 2 MPa, requiring certain transportation and storage qualifications. Furthermore, this method suffers from slow cooling and complex equipment, requiring significant pre-cooling time and resulting in high equipment costs. Furthermore, the paper "Control Mode of a Novel Air-Cooled RF Ablation System," based on Solution 3, only describes the use of a conventional PID algorithm to control the probe temperature at 80°C-90°C during the RF process. This system exhibits significant hysteresis and low precision, and still presents the problem of extensive carbonization of tissue surrounding the probe. Summary of the Invention

[0005] 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.

[0006] The present application discloses a method for controlling a flow medium in a thermal ablation system, wherein 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, wherein the heat exchange evaporation unit is provided with a gas-liquid separator;

[0007] The control method includes:

[0008] 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;

[0009] 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.

[0010] 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.

[0011] In a preferred embodiment, step B further comprises:

[0012] Detecting the head temperature of the ablation probe, calculating 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 using the first and second formulas, 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,

[0013] The first formula is:

[0014] The second formula is: error N =TT set ;

[0015] Among them, error N is the temperature error at the current moment, k P is the power term proportional coefficient, k T is the temperature term proportional 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.

[0016] In a preferred embodiment, step A further comprises:

[0017] detecting the nitrogen temperature of the ablation probe;

[0018] 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.

[0019] In a preferred embodiment, it also includes:

[0020] Steps A to B are performed in real time or periodically to keep the head temperature at the target temperature.

[0021] 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;

[0022] The thermal ablation system further comprises:

[0023] 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;

[0024] 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 to make the head temperature reach the target temperature.

[0025] 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.

[0026] In a preferred embodiment, the second flow resistance control unit includes a second temperature detection device, a second voltage adjustment module and a second flow regulating device provided at the rear end of the ablation probe;

[0027] The second temperature detection device is configured to detect the temperature of the head of the ablation probe;

[0028] 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 proportional coefficient, k T is the temperature term proportional 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.

[0029] In a preferred embodiment, the first flow resistance control unit includes a first temperature detection device, a first voltage adjustment module and a first flow regulating device provided at the rear end of the gas-liquid separator;

[0030] The temperature detection device is configured to detect the nitrogen temperature of the ablation probe;

[0031] 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.

[0032] In a preferred example, the first flow resistance control unit and the second flow resistance control unit are alternately and periodically executed to keep the head temperature at the target temperature.

[0033] The embodiments of the present application include at least the following advantages and beneficial effects:

[0034] During radiofrequency ablation, liquid nitrogen is evaporated 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 subzero temperature range. Compared with traditional technical solutions, this 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 between 0°C and -40°C, absorb more excess heat, delay the occurrence of tissue carbonization, and obtain a larger ablation range, which helps 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.

[0035] Furthermore, an improved radiofrequency ablation control algorithm is proposed to address the characteristics of the large hysteresis system of the internal cooling cycle radiofrequency ablation. This algorithm can quickly control and / or maintain the low-temperature nitrogen obtained by phase change at a predetermined subzero temperature, with minimal overshoot and fluctuation. Therefore, compared with Technical Solution 3, the improved control algorithm proposed in the embodiment of the present application can better address the large hysteresis problem of such systems, with minimal overshoot and high precision. Moreover, since the low-temperature nitrogen is obtained by evaporating liquid nitrogen, it is cheap and easy to obtain.

[0036] 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 of this application (i.e., technical solutions) are to be listed, the specification will be too lengthy. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of this application, the various technical features disclosed in the various embodiments 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 all deemed to have been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that play the same role. Technically, only one of them can be used, and it is impossible to use them at the same time. Feature E can be technically combined with feature C. Then, the solution of A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution of A+B+C+E should be considered as having been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic structural diagram of a thermal ablation system according to the first embodiment of the present application.

[0038] Figure 2 It is a flow chart of a method for controlling a flow medium in a thermal ablation system according to the second embodiment of the present application.

[0039] Figure 3 It is a flow chart of a method for controlling a flowing medium during thermal ablation according to one embodiment of the present application.

[0040] Figure 4 This is a diagram of the control voltage of the proportional valve at the rear end of the probe and the needle tip temperature control results according to an embodiment of the present application.

[0041] Figure 5 This is a diagram showing the 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 DESCRIPTION

[0042] In the following description, many technical details are provided to help readers better understand this application. However, those skilled in the art will understand that even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented.

[0043] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0044] The first embodiment of the present application relates to a thermal ablation system, such as Figure 1 As shown, 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 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 through the pipeline to the ablation probe. Liquid nitrogen is liquid nitrogen and 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 gas. 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, resulting in too long heat exchange time and too high temperature after reaching the ablation probe. Therefore, the heat exchange evaporation unit also includes a gas-liquid separator. By adjusting the flow resistance at the rear end of the gas-liquid separator, the liquid nitrogen flow rate is controlled to ensure that the nitrogen gas entering the ablation probe has a sufficiently low temperature.

[0045] Optionally, the thermal ablation system further includes a control unit, comprising a first flow resistance control unit and a second flow resistance control unit. The first flow resistance control unit is configured to adjust the flow resistance at the rear end 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. Optionally, the first flow resistance control unit includes a first temperature detection device, a first voltage adjustment module, and a first flow control device disposed 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 control device at the rear end of the gas-liquid separator or reduce the control voltage applied to the first flow control device when the detected nitrogen temperature is less than a first threshold, and to open the flow control device at the rear end of the gas-liquid separator and / or increase the control voltage applied to the first flow control device when the detected nitrogen temperature is greater than a second threshold, so as to control the temperature of the nitrogen gas flowing into the ablation probe to remain within the predetermined temperature range between the first and second thresholds. For example, in one embodiment, the first flow resistance control unit includes a temperature measurement device disposed at the liquid nitrogen inlet and a flow control 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 control device may be a proportional valve, or a flow control device or structure such as a solenoid valve or a manual valve. For example, if the first flow control 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, the nitrogen temperature is considered too high; when the temperature measured by the thermocouple at the liquid nitrogen inlet is lower than -140°C, the nitrogen temperature is considered too low. At this time, the proportional valve at the rear end of the gas-liquid separator is closed, i.e., the applied voltage is 0V.

[0046] Furthermore, 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 proportional coefficient, k Tis the temperature term proportional 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.

[0047] The second temperature detection device is integrated into the ablation probe head, for example but not limited to a thermocouple, and is buried inside the ablation probe, so that the comprehensive thermal effect of the internal flow medium and thermal ablation can be measured.

[0048] 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.

[0049] In one embodiment, the system adjusts the flow resistance at the rear end of the ablation probe based on the temperature value detected by the second flow resistance control unit, thereby controlling the flow rate of low-temperature nitrogen gas to maintain the temperature of the nitrogen gas flowing into the ablation probe 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 is further 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 target temperature range may also be other values, for example, those obtained through pipeline structure experiments.

[0050] The second embodiment of the present application relates to a method for controlling a flow medium in a thermal ablation system, wherein 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, wherein the heat exchange evaporation unit is provided with a gas-liquid separator, and the control method flow is as follows: Figure 2 As shown, the control method includes the following steps:

[0051] 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;

[0052] 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.

[0053] 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.

[0054] 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. and the second formula error N =TT setCalculate the control voltage of the flow regulating device at the rear end of the ablation probe, and generate and output the control voltage to the control end of the flow regulating device at the rear end of the ablation probe to adjust the flow resistance at the rear end of the ablation probe. N is the temperature error at the current moment, k P is the power term proportional coefficient, k T is the temperature term proportional 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.

[0055] Optionally, step 201 further includes the following steps 201a and 201b:

[0056] Step 201a, detecting the nitrogen temperature of the ablation probe;

[0057] 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.

[0058] 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.

[0059] In order to better understand the beneficial effects of the present application, the following is an example of heating an isolated 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. Figure 3 , including the following steps:

[0060] Step 301: First, open the valve of the liquid nitrogen tank, which has a pressure between 0.8 MPa and 1.2 MPa. Driven by pressure, the liquid nitrogen flows through the pipeline connecting the ablation probe and the pressurized liquid nitrogen source, exchanging heat and evaporating into low-temperature nitrogen gas. A gas-liquid separator is located in the pipeline. The flow rate of the liquid nitrogen is controlled by adjusting the flow resistance behind the gas-liquid separator, ensuring that the nitrogen entering the ablation probe has a sufficiently low temperature. Adjusting the flow resistance of the gas-liquid separator adjusts the control voltage of the proportional valve behind the gas-liquid separator.

[0061] Step 302: Acquire the temperature measured by the thermocouple at the tip of the radiofrequency ablation needle, store it in a storage medium, and read it in real time by a program.

[0062] 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 to calculate the control voltage of the proportional valve at the rear end of the ablation probe using the following control equation:

[0063]

[0064] error N =TT set

[0065] Where V is the calculated control voltage of the proportional valve at the rear end of the ablation probe, k P is the power term proportional coefficient, k T is the temperature term proportional coefficient, error N is the temperature error at the current moment, T set The target tip temperature of the RF ablation needle is: Figure 4 shown.

[0066] 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.

[0067] Step 305 is to determine whether the nitrogen temperature is low enough. In this embodiment, when the temperature measured by the thermocouple at the liquid nitrogen inlet is higher than -130°C, 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°C, 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.

[0068] Step 306: When it is determined in step 305 that the nitrogen temperature is too high, the proportional valve at the rear end of the gas-liquid separator in step 301 needs to be opened. In this embodiment, the voltage applied to the proportional valve at the rear end of the gas-liquid separator is 1V. This voltage can also be other values. The value in this embodiment is obtained based on the pipeline structure experiment. 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 306. Figure 5 Show.

[0069] Through the analysis and experiments of this embodiment, it can be known 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℃ to -40℃, with the maximum overshoot within 3℃ and the fluctuation after stabilization less than ±0.5℃, thereby avoiding overcooling or overheating around the ablation probe and achieving the purpose of controlling the ablation range.

[0070] The first embodiment is a method embodiment corresponding to the present embodiment. The technical details in the first embodiment can be applied to the present embodiment, and the technical details in the present embodiment can also be applied to the first embodiment.

[0071] 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 the flow. The temperature measuring unit can be a thermocouple built into the ablation probe, or an optical fiber, an external thermocouple, or a non-contact MR, ultrasonic temperature measurement, etc. In addition, the present application can use the proposed improved temperature control algorithm, or can use adaptive control algorithms such as PID control, sliding mode control, fuzzy control, neural network, genetic algorithm, predictive control, quadratic optimal control, time delay control, and uncertainty 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.

[0072] 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 solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a set of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "comprising a" does not preclude the presence of other identical elements in the process, method, article, or device comprising the element. In the application documents of this patent, reference to performing an action according to an element means performing the action according to at least that element, including two situations: performing the action according to that element alone, and performing the action according to that element and other elements. Expressions such as "multiple," "multiple," and "multiple" include "two," "twice," "two kinds," and "more than two," "more than two times," and "more than two kinds."

[0073] All documents mentioned in this application are considered to be included in their entirety in the disclosure of this application so that they can be used as a 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 may make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A thermal ablation system, characterized in that: 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. Liquid nitrogen flows into the heat exchange evaporation unit, and nitrogen gas flows out of the heat exchange evaporation unit. 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 during radiofrequency ablation to control the temperature of the nitrogen gas flowing into the ablation probe to remain within a predetermined temperature range; The second flow resistance control unit is configured to detect the head temperature of the ablation probe during radiofrequency ablation, and adjust the rear end flow resistance of the ablation probe according to the detected head temperature and the set radiofrequency power so that the head temperature is the target temperature, which is between 0°C and -40°C.

2. The thermal ablation system according to claim 1, wherein: The predetermined temperature range is -140°C to -130°C.

3. The thermal ablation system according to claim 2, wherein: The second flow resistance control unit includes a second temperature detection device, a second voltage adjustment module and a second flow regulating device provided at the rear end of the ablation probe; The second temperature detection device is configured to detect the temperature of the head 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 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 proportional coefficient, k T is the temperature term proportional 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.

4. The thermal ablation system according to claim 2, wherein: 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.

5. The thermal ablation system according to any one of claims 1 to 4, characterized in that: The first flow resistance control unit and the second flow resistance control unit are alternately and periodically executed to maintain the head temperature at the target temperature.

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