Radiofrequency ablation catheter contact condition characterization device

Abstract

The present invention discloses a device for characterizing the contact condition of a radiofrequency ablation catheter, including a radiofrequency ablation catheter, a phase shift circuit, a phase detection circuit, a PI controller and a driving circuit. The radiofrequency ablation catheter includes a first group of electrodes consisting of a first annular electrode and a second annular electrode and a second group of electrodes consisting of a third annular electrode and a microelectrode. During the implementation of the radiofrequency ablation surgery, the two groups of electrodes used for measurement are completely in the blood at first, and the phase difference between the current signals measured by the two groups of electrodes is recorded at this time; as the radiofrequency ablation catheter goes deeper, the microelectrode contacts the tissue, and the phase difference between the two groups of current signals changes. The present invention automatically adjusts the frequency of the driving voltage so that the phase difference between the current signals of the two groups of electrodes remains consistent with the previous one, and then reflects the change in the depth of the radiofrequency ablation catheter inserted into the tissue according to the frequency change, thereby characterizing the contact condition between the radiofrequency ablation catheter and the tissue, and guiding the precise implementation of surgical treatment.

Description

Technical Field

[0001] The present invention relates to a novel device for characterizing the contact between a radiofrequency ablation catheter and human tissue, and in particular to a local characterization of the process from the radiofrequency ablation catheter contacting blood to muscle tissue. Background Art

[0002] In recent years, with the continuous development of minimally invasive ablation technology and medical imaging guidance technology, local ablation technology has become increasingly important in the treatment of tumor diseases. Compared with surgical resection, the use of local ablation technology to treat tumor diseases has the advantages of low morbidity, low mortality, low cost, and suitability for real-time monitoring. In addition, there are many factors that affect the local damage of tumor tissue during radiofrequency ablation for tumor treatment. However, since the degree of damage to tumor tissue cannot be accurately assessed during conventional ablation, we need to use other characteristics of tumor tissue during ablation to mark the actual damage to the tissue and guide the delivery of radiofrequency ablation energy.

[0003] Nowadays, in the process of radiofrequency ablation, in addition to the factors such as tissue temperature, tissue impedance characteristics, and radiofrequency ablation device power, which have a great influence on the effect of radiofrequency ablation, the contact between the electrode and the tissue is also an important factor in characterizing the effect of radiofrequency ablation. By using a constant power radiofrequency ablation power supply to conduct ablation experiments on myocardial tissue, the results show that not only the size of the electrode on the catheter and the distance between the electrodes have a certain influence on the effect of radiofrequency ablation, but also the depth of the radiofrequency ablation catheter inserted into the tissue has a particularly prominent influence on the effect of radiofrequency ablation. Therefore, during the process of radiofrequency ablation, it is necessary to monitor the contact between the tumor tissue and the catheter in real time.

[0004] The changes in the collected current signals during the radiofrequency ablation process can be used to monitor the insertion depth of the radiofrequency ablation catheter in real time, thereby characterizing the contact between the catheter and the tumor tissue, and further controlling the precise progress of the radiofrequency ablation process to a certain extent. In addition, by measuring the current information of the muscle tissue at the tip of the catheter before radiofrequency ablation, the insertion depth of the radiofrequency ablation catheter can be adjusted according to the measured value, so that the catheter is at a depth that achieves the best ablation effect during radiofrequency ablation.

[0005] Therefore, in order to ensure the effectiveness of ablation treatment and the safety of patients, the depth of insertion of the radiofrequency ablation catheter into the tissue is further measured to obtain the contact status between the catheter and human tissue, which has very important theoretical significance and practical value for monitoring the progress of radiofrequency ablation. Summary of the invention

[0006] The object of the present invention is to provide a radiofrequency ablation catheter contact condition characterization device, so as to better guide the progress of radiofrequency ablation according to the insertion depth of the radiofrequency ablation catheter into human tissue.

[0007] To achieve the above object, the present invention provides a radiofrequency ablation catheter contact condition characterization device, comprising:

[0008] A radiofrequency ablation catheter, comprising a first annular electrode, a second annular electrode and a third annular electrode arranged on its outer layer from top to bottom, and a microelectrode embedded at the tip of the radiofrequency ablation catheter, wherein the third annular electrode is arranged adjacent to the microelectrode; when the radiofrequency ablation catheter is in contact with blood only, a phase difference between a second current signal between the microelectrode and the third annular electrode and a first current signal between the first annular electrode and the second annular electrode is an initial given value, and the initial given value is 0; when the radiofrequency ablation catheter contacts muscle tissue, the second current signal between the microelectrode and the third annular electrode changes;

[0009] a phase shift circuit, used for adjusting the phase of the first current signal to reduce the phase difference between the first current signal and the second current signal;

[0010] A phase detection circuit, connected to the phase shift circuit, for measuring and detecting a phase difference between the first current signal and the second current signal;

[0011] a PI controller connected to the phase detection circuit, used for adjusting the phase difference between the first current signal and the second current signal, and calculating the difference between the phase difference and an initial given value to obtain a frequency control word; and

[0012] The driving circuit is connected to the PI controller and is used to change the frequency of the voltage signal driving the radiofrequency ablation catheter according to the obtained frequency control word, so that the phase difference between the first current signal and the second current signal remains at an initial given value of 0.

[0013] As a further improvement of the present invention, the driving circuit includes a DDS signal source connected to the PI controller, and the PI controller is capable of adjusting the frequency of the output signal of the DDS signal source to generate a non-stimulating AC voltage signal.

[0014] As a further improvement of the present invention, the driving circuit also includes a power amplifier circuit connected between the radio frequency ablation catheter and the DDS signal source, and the power amplifier circuit is respectively connected to the first ring electrode and the third ring electrode, and is used to drive and measure the current generated on the microelectrode, the third ring electrode, the second ring electrode and the first ring electrode.

[0015] As a further improvement of the present invention, a plurality of microelectrodes are provided and embedded at the tip of the radiofrequency ablation catheter at equal intervals.

[0016] As a further improvement of the present invention, the distance between the center of each microelectrode and the tip of the RF ablation catheter is the same, the diameter of each microelectrode is the same, and the distance from the center of each microelectrode to the center of the RF ablation catheter tip is also the same.

[0017] As a further improvement of the present invention, the phase shift circuit includes a power amplifier, a resistor R1 connected to the negative input terminal of the power amplifier, a capacitor C1 connected in parallel with the resistor R1 and connected to the positive input terminal of the power amplifier, and a resistor R2 having one end connected to the positive input terminal of the power amplifier and the other end grounded.

[0018] As a further improvement of the present invention, the transfer function of the phase shift circuit is:

[0019]

[0020] The transfer function has a zero at s = 1 / C1R2 and a pole at s = -1 / C1R2. Let s = jω and we get:

[0021] θ=-2 arctanωC1R2

[0022] Here, θ is the phase difference.

[0023] As a further improvement of the present invention, when the phase difference between the first current signal and the second current signal is 0, the frequency of the voltage signal driving the radio frequency ablation catheter is the resonant frequency.

[0024] As a further improvement of the present invention, when the radiofrequency ablation catheter contacts muscle tissue, the conductive medium between the microelectrode and the third ring electrode is converted into muscle tissue and blood. At this time, the phase of the second current signal between the microelectrode and the third ring electrode changes, but the phase of the first current signal between the first ring electrode and the second ring electrode remains unchanged, so that there is a phase difference.

[0025] The beneficial effects of the present invention are as follows: the present invention extracts the phase difference between the collected first current signal and the second current signal, and then changes the frequency control word of the DDS signal source through PI controller processing, so that the DDS signal source can output signals of different frequencies, thereby driving the radiofrequency ablation catheter with signals of different frequencies, recording the resonant frequency when the phase difference is the initial given value, and reflecting the depth of the radiofrequency ablation catheter inserted into the human tissue through the change of frequency, thereby more effectively guiding the progress of radiofrequency ablation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural block diagram of the radiofrequency ablation catheter contact condition characterization device of the present invention.

[0027] Figure 2 yes Figure 1 Schematic diagram of the structure of the radiofrequency ablation catheter.

[0028] Figure 3 yes Figure 2 A cross-sectional view of a radiofrequency ablation catheter is shown.

[0029] Figure 4 yes Figure 3 Cross-sectional view of the ring electrode.

[0030] Figure 5 yes Figure 3 Cross-sectional view of the microelectrode.

[0031] Figure 6 It is a trend diagram of phase difference and frequency difference obtained by simulation calculation in the present invention.

[0032] Figure 7 yes Figure 1 Circuit diagram of the phase shift circuit.

[0033] Figure 8 yes Figure 1 The working principle diagram of the DDS signal source.

[0034] Fig. 9 It is a simulation model built using COMSOL simulation software.

[0035] Fig.10 Radiofrequency ablation catheter Fig. 9 The basis moves to the simulation model after the organizational model.

[0036] Fig.11 It is a frequency change curve after the radiofrequency ablation catheter is inserted into the muscle tissue. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figures 1 to 5 As shown, based on the existing measurement method of radio frequency ablation catheter inserted into human tissue, the present invention discloses a device for characterizing the contact condition of radio frequency ablation catheter, which integrates a microelectrode 24, a third annular electrode 23, a second annular electrode 22 and a first annular electrode 21 at the tip of the radio frequency ablation catheter 2. During the process of inserting the radio frequency ablation catheter 2 into human tissue, two current signals are formed by real-time collection of current information of human tissue between the first annular electrode 21 and the second annular electrode 22 and between the third annular electrode 23 and the microelectrode 24. The phase difference between the two current signals is converted into a frequency difference with more obvious changes, so as to characterize the difference in contact condition between the radio frequency ablation catheter 2 and tissue.

[0039] Initially, the microelectrode 24, the third annular electrode 23, the second annular electrode 22 and the first annular electrode 21 are all in the blood environment, and there is no phase difference between the two current signals measured at this time. As the radiofrequency ablation catheter 2 goes deeper, the medium between the third annular electrode 23 and the microelectrode 24 gradually changes to blood and muscle tissue. Due to the change of the medium, there is a phase difference between the two current signals collected at this time, but due to the small phase difference value, it cannot accurately characterize the difference in impedance information. Therefore, the present invention processes the two current signals with phase difference through a subsequent control loop, continuously adjusts the frequency of the driving voltage during the processing process, and converts the phase difference into a more obvious frequency difference, so that the phase difference between the two current signals collected is finally 0, and the frequency value at this time is recorded. In other words, by analyzing the changes in the frequency of the voltage signal before and after processing, the changes in the depth of insertion of the radiofrequency ablation catheter 2 into the human body and the contact situation are monitored in real time, so that the posture of the radiofrequency ablation catheter 2 is appropriately adjusted externally.

[0040] Specifically, the radiofrequency ablation catheter contact condition characterization device mainly includes a radiofrequency ablation catheter 2, a phase shift circuit 3, a phase detection circuit 4, a PI controller 5 and a driving circuit, which constitute an automatic frequency tracking loop as a whole. Among them, the radiofrequency ablation catheter 2 includes a first annular electrode 21, a second annular electrode 22 and a third annular electrode 23 arranged on its outer layer from top to bottom, and a microelectrode 24 embedded at the tip of the radiofrequency ablation catheter 2, and the third annular electrode 23 is arranged adjacent to the microelectrode 24. The microelectrodes 24 are arranged in plurality and are embedded in the tip of the radiofrequency ablation catheter 2 at equal intervals. The center of each microelectrode 24 is at the same distance from the tip of the radiofrequency ablation catheter 2, the diameter of each microelectrode 24 is the same, and the center of each microelectrode 24 is at the same distance from the center of the tip of the radiofrequency ablation catheter 2.

[0041] The multiple microelectrodes 24 are very close to each other and are located at the tip of the radiofrequency ablation catheter 2, so there is no significant difference in their measurement results. In order to avoid too much data, we take the maximum impedance value obtained by multiple electrode measurements as the final result.

[0042] When the radiofrequency ablation catheter 2 enters the human body, it first comes into full contact with the blood, and the blood makes the first annular electrode 21 and the second annular electrode 22 and the third annular electrode 23 and the microelectrode 24 conductive. At this time, the phase difference between the second current signal I2 between the microelectrode 24 and the third annular electrode 23 and the first current signal I1 between the first annular electrode 21 and the second annular electrode 22 is an initial given value. Preferably, the initial given value is 0, that is, there is no phase difference between the two current signals collected. As the radiofrequency ablation catheter 2 goes deeper, when the radiofrequency ablation catheter 2 contacts the muscle tissue, the conductive medium between the microelectrode 24 and the third annular electrode 23 gradually changes to muscle tissue and blood. In this process, the phase of the second current signal I2 between the microelectrode 24 and the third annular electrode 23 changes, but the phase of the first current signal I1 between the first annular electrode 21 and the second annular electrode 22 remains unchanged, which results in a phase difference between the two current signals collected. At this time, it is also necessary to record the impedance information of the human tissue.

[0043] The microelectrode 24, the third annular electrode 23, the second annular electrode 22 and the first annular electrode 24 on the radiofrequency ablation catheter 2 are respectively located at different positions of the muscle tissue, but at this time, the local impedance value of the blood does not change. When the radiofrequency ablation catheter 2 contacts the healthy tissue, the phase change value is higher than the local impedance value in the blood, but at this time, the local impedance values ​​at different positions of the muscle tissue do not change. Each measurement time exceeds 10 seconds, during which the measured value does not fluctuate significantly. At the beginning and end of each case, there is no significant difference in the blood value at the specific muscle tissue of each patient.

[0044] The phase shift circuit 3 is connected to the radiofrequency ablation catheter 2, and is used to adjust the phase of the first current signal I1 between the first annular electrode 21 and the second annular electrode 22, so as to reduce the phase difference between the collected first current signal I1 and the second current signal I2, so that the system can track the frequency change in the resonant state more quickly. The phase detection circuit 4 is connected to the phase shift circuit 3, and is used to measure and detect the phase difference between the first current signal I1 and the second current signal I2. Specifically, since the impedance model of human tissue is a parallel RC circuit, and the autonomous resonance effect of the RC circuit alone is poor, it needs to be processed by an external circuit. Therefore, the present invention introduces a phase shift circuit 3 to process the collected current signal, and then measures the phase difference between the two current signals through the phase detection circuit 4, and adjusts the resonant frequency of the loop through the phase difference, so that the system can enter the resonant state more quickly.

[0045] The phase difference presented by the radiofrequency ablation catheter 2 when it is in contact with blood or muscle tissue is small, and cannot well reflect the change of insertion depth. In the present invention, by converting the phase difference into a more obvious frequency difference, the information of the insertion depth of the radiofrequency ablation catheter 2 can be better characterized. In addition, in order to make the change effect more obvious, the present invention converts the case where the phase difference of the collected current signal is the largest to obtain the result with the largest resonant frequency difference, thereby better reflecting the change of insertion depth.

[0046] Specifically, the simulation model was built using COMSOL finite element simulation software, and the trends of phase difference and frequency difference were obtained through simulation calculations, such as Figure 6 (a), where the horizontal axis is the frequency difference and the vertical axis is the phase difference. Figure 6 As shown in (b), the situation where the phase difference is the largest is analyzed, and the phase shift circuit 3 is used to assist, so that when the phase difference is the largest, the final phase difference is 0 by adjusting the frequency.

[0047] Furthermore, since the case where the phase difference is the largest is processed, the final requirement is that the phase difference is 0 and the system enters a resonant state. The human tissue impedance model is a parallel RC circuit, and the parallel RC circuit needs to eliminate the phase difference when entering a resonant state, so the present invention uses a phase shift circuit 3 to process the collected signal.

[0048] like Figure 7 As shown, the phase shift circuit 3 includes a power amplifier, a resistor R1 connected to the negative input terminal of the power amplifier, a capacitor C1 connected in parallel with the resistor R1 and connected to the positive input terminal of the power amplifier, and a resistor R2 having one end connected to the positive input terminal of the power amplifier and the other end grounded.

[0049] The transfer function of the phase shift circuit 3 is:

[0050]

[0051] It can be seen that the transfer function has a zero point located at s = 1 / C1R2 and a pole at s = -1 / C1R2. Let s = jω to obtain:

[0052] θ=-2 arctanωC1R2

[0053] Where θ is the phase difference. By selecting a suitable R2 value, the phase of the input signal can be modified within the range of 0 to 180°. In the present invention, the case of the largest phase difference is handled. Therefore, by selecting an R2 resistance value within a certain range, a certain phase shift can occur at a specific frequency. The phase shift curve is shown in FIG. Figure 6 (b) As shown in FIG. 3 , the system can enter the resonance state more quickly through the processing of the phase shift circuit 3 .

[0054] The PI controller 5 is connected to the phase detection circuit 4, and is used to adjust the phase difference between the first current signal I1 and the second current signal I2, and calculate the difference between the phase difference and the initial given value to obtain the frequency control word. The driving circuit is connected to the PI controller 5, and is used to change the frequency of the voltage signal driving the radiofrequency ablation catheter 2 according to the obtained frequency control word, so that the phase difference between the first current signal I1 and the second current signal I2 remains at the initial given value of 0.

[0055] Specifically, the driving circuit includes a DDS signal source 6 connected to a PI controller 5 and a power amplifier circuit 1 connected between the radiofrequency ablation catheter 2 and the DDS signal source 6. The PI controller 5 can adjust the frequency of the output signal of the DDS signal source 6 to generate a non-irritating AC voltage signal, and convert the non-irritating AC voltage into impedance by dividing it by the measured current value. The change in the AC voltage frequency during the measurement process is used to characterize the change in the depth of the catheter inserted into the human tissue.

[0056] The power amplifier circuit 1 is connected to the first annular electrode 21 and the third annular electrode 23 respectively, and is used to drive and measure the current generated on the microelectrode 24, the third annular electrode 23, the second annular electrode 22 and the first annular electrode 21. When the radiofrequency ablation catheter 2 is in contact with blood, the blood acts as a conductor between the first annular electrode 21 and the second annular electrode 22 and between the third annular electrode 23 and the microelectrode 24. At this time, the driving circuit will provide an AC voltage signal to be applied to the radiofrequency ablation catheter 2, so the current signal and impedance information of the blood are measured at first. When the radiofrequency ablation catheter 2 is inserted into the muscle tissue, the microelectrode 24 and the third annular electrode 23 are driven by an external AC voltage signal to measure the current signals of the muscle tissue and the blood respectively, and after being processed by the PI controller 5 and the DDS signal source 6, a resonant state with a phase difference of 0 is finally reached, and the resonant frequency of the AC voltage signal is recorded. The change in the frequency of the initial and final AC voltage signals reflects the change in the depth of the radiofrequency ablation catheter 2 inserted into the muscle tissue, thereby adjusting the position and posture of the radiofrequency ablation catheter 2 in the human body to achieve a better radiofrequency ablation effect.

[0057] The frequency change process is the process in which the PI controller 5 changes the frequency control word of the DDS signal source 6 according to the processed phase difference, thereby changing the frequency of the output voltage signal of the DDS signal source 6. Through the action of the PI controller 5, the system finally enters the resonant state again when the phase difference is 0, and the value of the resonant frequency at this time is recorded. In other words, the automatic frequency tracking in the present invention adopts a composite tracking strategy based on DDS and PI controller 5. The DDS signal source 6 adopts direct digital frequency synthesis technology to improve the frequency stability and accuracy of the signal generator to the same level as the reference voltage, and can accurately adjust the frequency of the output signal within a wide frequency range by changing the frequency control word.

[0058] Furthermore, in the present invention, signal sources of different frequencies are obtained by composite control of the PI controller 5 and the DDS signal source 6, and the output of signals of different frequencies by the DDS signal source 6 is obtained by changing the frequency control word of the DDS signal source 6. In the present invention, the phase difference of the collected two-way current signal is obtained by processing through the phase detection circuit 4, and different frequency control words can be obtained by processing through the PI controller 5, thereby generating signal sources of different frequencies, which are processed by the power amplifier circuit 1 and used to drive the radiofrequency ablation catheter 2.

[0059] In summary, the phase shift circuit 3 is used to adjust the phase of the collected current signal, thereby reducing the phase difference between the two collected current signals, so that the system can track the frequency change in the resonant state more quickly. The PI controller 5 specifically refers to the control deviation formed according to the given value and the actual output value, and the deviation is linearly combined by proportional and integral methods to form a control quantity to control the controlled object. The DDS signal source 6 is based on direct digital frequency synthesis technology to adjust the frequency of the signal source to an appropriate frequency. This technology has the characteristics of wide tracking range, high frequency resolution, and fast response. Its schematic diagram is shown in FIG. Figure 8 shown.

[0060] The following is an example of a simulation model built using COMSOL simulation software.

[0061] like Fig. 9 As shown in FIG. 1 , the simulation model mainly includes a tissue model 11, a blood model 12, and a radiofrequency ablation catheter model 13. When the radiofrequency ablation catheter model 13 is completely placed in the blood model 12, the phase difference between the two current signals is indeed 0, and the system is in a resonant state. As the radiofrequency ablation catheter model 13 goes deeper, the conductor between the third ring electrode 23 and the microelectrode 24 is gradually transformed from blood to blood and muscle tissue. In this process, due to the change of the conductor medium, there is a phase difference between the two current signal components collected. When the radiofrequency ablation catheter model 13 is moved to Fig.10At the position shown, COMSOL software can detect that there is a certain phase difference between the two currents, and the difference is small, which cannot well reflect the insertion depth of the radiofrequency ablation catheter model 13.

[0062] After the two current signals with phase difference are processed by the phase shift circuit 3, the situation with the largest phase difference is collected, and the PI controller 5 is used to compare and control the situation completely in the blood model 12. The frequency control word of the DDS signal source 6 is continuously updated according to the processing result, so that the DDS signal source 6 outputs signals with different frequencies, which are used to drive the radiofrequency ablation catheter model 13 after being processed by the power amplifier circuit 1. By changing the frequency, the collected phase difference value of the whole system is made smaller and smaller until the phase difference is 0 and enters the resonance state again. At this time, the phase difference of the whole system is 0, and the frequency of the driving signal is stabilized to a new value. The value of the frequency corresponding to the AC driving voltage signal is recorded at this time.

[0063] like Fig.11 As shown, it can be seen that there are obvious frequency changes and adjustment processes. The changes in the frequency before and after characterize the changes in the insertion depth of the radiofrequency ablation catheter 2 in the human body, thereby characterizing whether the radiofrequency ablation catheter 2 is in contact with the tissue. By monitoring the insertion depth of the radiofrequency ablation catheter 2, medical experts can know the specific contact between the radiofrequency ablation catheter 2 and the tissue through the change in frequency, so as to perceive the position and posture of the radiofrequency ablation catheter 2 in the human body in real time in vitro, and provide real-time feedback information in the human body for the radiofrequency ablation surgery, so that the posture of the radiofrequency ablation catheter 2 can be adjusted in real time and effectively, and finally the best radiofrequency ablation effect can be achieved. This is of great help for the surgeon to understand the condition of muscle tissue lesions and perform medical treatment.

[0064] The working principle of the present invention can be simply described as follows: initially, the radiofrequency ablation catheter 2 is completely in the blood, and the phase difference of the two current signals collected at this time is the initial value θ0 of 0, the system is in a resonant state, and the frequency value at this time is recorded; as the radiofrequency ablation catheter 2 goes deeper, the conductor between the third annular electrode 23 and the microelectrode 24 is gradually converted from blood to blood and muscle tissue. In this process, the phase of the measured current signal changes due to the change in the medium, and the phase difference between the two current signal components becomes θ1, and the system is no longer in a resonant state; at this time, the collected first current signal I1 is processed by the phase shift circuit 3, and the phase difference between the two current signals is measured by the phase detection circuit 4, and then the difference between the phase difference and the initial value is used as the deviation signal, and the frequency control word of the DDS signal source 6 is adjusted by the PI controller 5, thereby adjusting the frequency of the driving voltage to achieve the purpose of eliminating the deviation, and finally the phase difference is maintained near the initial value θ0, and the system enters the resonant state again, and the value of the frequency information corresponding to the AC voltage signal is recorded at this time. The change in frequency before and after the measurement process is used to characterize the change in the depth of the radiofrequency ablation catheter 2 inserted into the human tissue during the process, thereby reflecting the contact between the radiofrequency ablation catheter 2 and the human tissue, so as to better guide the subsequent radiofrequency ablation treatment.

[0065] In summary, the present invention extracts the phase difference of the two collected current signals, and then changes the frequency control word of the DDS signal source 6 through processing by the PI controller 5, so that the DDS signal source 6 can output signals of different frequencies, thereby driving the radiofrequency ablation catheter 2 with signals of different frequencies, and recording the resonant frequency when the phase difference is the initial given value of 0. Through the change of frequency, the depth of insertion of the radiofrequency ablation catheter 2 into the human tissue is reflected, thereby more effectively guiding the progress of radiofrequency ablation.

[0066] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A radiofrequency ablation catheter contact condition characterization device, characterized in that: include: A radiofrequency ablation catheter, comprising a first annular electrode, a second annular electrode and a third annular electrode arranged on its outer layer from top to bottom, and a microelectrode embedded at the tip of the radiofrequency ablation catheter, wherein the third annular electrode is arranged adjacent to the microelectrode; when the radiofrequency ablation catheter is in contact with blood only, a phase difference between a second current signal between the microelectrode and the third annular electrode and a first current signal between the first annular electrode and the second annular electrode is an initial given value, and the initial given value is 0; when the radiofrequency ablation catheter contacts muscle tissue, the second current signal between the microelectrode and the third annular electrode changes; a phase shift circuit, used for adjusting the phase of the first current signal to reduce the phase difference between the first current signal and the second current signal; A phase detection circuit, connected to the phase shift circuit, for measuring and detecting a phase difference between the first current signal and the second current signal; A PI controller, connected to the phase detection circuit, for adjusting the phase difference between the first current signal and the second current signal, and calculating the difference between the phase difference and an initial given value to obtain a frequency control word; as well as The driving circuit is connected to the PI controller and is used to change the frequency of the voltage signal driving the radiofrequency ablation catheter according to the obtained frequency control word, so that the phase difference between the first current signal and the second current signal remains at an initial given value of 0.

2. The radiofrequency ablation catheter contact condition characterization device according to claim 1, characterized in that: The driving circuit includes a DDS signal source connected to the PI controller, and the PI controller is capable of adjusting the frequency of the output signal of the DDS signal source to generate a non-stimulating AC voltage signal.

3. The radiofrequency ablation catheter contact condition characterization device according to claim 2, characterized in that: The driving circuit also includes a power amplifier circuit connected between the radiofrequency ablation catheter and the DDS signal source, and the power amplifier circuit is connected to the first annular electrode and the third annular electrode respectively, and is used to drive and measure the current generated on the microelectrode, the third annular electrode, the second annular electrode and the first annular electrode.

4. The radiofrequency ablation catheter contact condition characterization device according to claim 1, characterized in that: The micro-electrodes are provided in plurality and embedded at the tip of the radiofrequency ablation catheter at equal intervals.

5. The radiofrequency ablation catheter contact condition characterization device according to claim 4, characterized in that: The distance between the center of each microelectrode and the tip of the radiofrequency ablation catheter is the same, the diameter of each microelectrode is the same, and the distance from the center of each microelectrode to the center of the tip of the radiofrequency ablation catheter is also the same.

6. The radiofrequency ablation catheter contact condition characterization device according to claim 1, characterized in that: The phase shift circuit includes a power amplifier, a resistor R1 connected to the negative input terminal of the power amplifier, a capacitor C1 connected in parallel with the resistor R1 and connected to the positive input terminal of the power amplifier, and a resistor R2 having one end connected to the positive input terminal of the power amplifier and the other end grounded.

7. The radiofrequency ablation catheter contact condition characterization device according to claim 6, characterized in that: The transfer function of the phase shift circuit is: The transfer function has a zero at s = 1 / C1R2 and a pole at s = -1 / C1R2. Let s = jω: θ=-2arctanωC1R2 Here, θ is the phase difference.

8. The radiofrequency ablation catheter contact condition characterization device according to claim 1, characterized in that: When the phase difference between the first current signal and the second current signal is 0, the frequency of the voltage signal driving the radio frequency ablation catheter is the resonant frequency.

9. The radiofrequency ablation catheter contact condition characterization device according to claim 1, characterized in that: When the radiofrequency ablation catheter contacts muscle tissue, the conductive medium between the microelectrode and the third annular electrode is converted into muscle tissue and blood. At this time, the phase of the second current signal between the microelectrode and the third annular electrode changes, but the phase of the first current signal between the first annular electrode and the second annular electrode remains unchanged, so that there is a phase difference.

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