Plasma electrode, impedance measurement signal injection method, tumor margin identification method

Abstract

The application discloses a plasma electrode, an impedance measurement signal injection method and a tumor edge recognition method, and relates to the technical field of electrosurgical instruments and biological tissue detection. In order to solve the problems that traditional plasma surgery cannot collect tissue electrical characteristics in situ in real time and cannot accurately recognize the tumor edge, the application integrates two pairs of micro measurement electrodes on the active electrode, and ceramic insulation micro channels are arranged on the back side; a 1kHz-5MHz logarithmic frequency point multi-frequency signal is superimposed, and the phase is optimized by a genetic algorithm, and then the signal is injected in parallel within 10ms; Cole relaxation frequency is extracted based on distributed relaxation time, and offline precalculation and online processing are used to realize fast recognition of the tumor edge. The application realizes deep integration of ablation and sensing, can judge the type of tissue in advance, and improves the accuracy and safety of tumor resection.

Description

Technical Field

[0001] This invention relates to the field of electrosurgical instruments and biological tissue detection technology, specifically to plasma electrodes, impedance measurement signal injection methods, and tumor edge recognition methods. Background Technology

[0002] Plasma surgical electrodes, as an important branch of electrosurgical instruments, generate a low-temperature plasma layer through radiofrequency energy, enabling minimally invasive ablation, cutting, and hemostasis of diseased tissues. They play a crucial role in areas such as precise resection of malignant tumors. During surgery, the load impedance naturally carries rich information about the surgical process, allowing for the assessment of changes in the pathophysiological characteristics of biological tissues and helping surgeons better understand the intraoperative situation.

[0003] However, traditional impedance testing often relies on independent spectrum analyzers or offline testing systems, making it difficult to achieve deep integration of ablation and sensing on surgical electrodes. This prevents the real-time, in-situ synchronous acquisition of local tissue electrical property data during surgery. Consequently, surgeons are forced to rely on visual observation and experience to determine tissue properties, making it difficult to accurately identify the boundary between tumors and normal tissues, and increasing the risk of residual tumor or excessive damage to normal tissues. Summary of the Invention

[0004] This invention proposes a plasma electrode structure that enables synchronous acquisition of local bioelectrical impedance data; it also proposes a rapid injection method for impedance measurement signals, which can rapidly inject multi-frequency components from 1k to 5MHz to achieve impedance measurement; and it proposes a rapid tumor edge identification method based on relaxation frequency, which can determine the tissue type affected by the scalpel tip in advance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A plasma electrode integrating broadband impedance sensing function includes an active electrode and a reflux electrode.

[0007] It also includes two pairs of impedance measurement electrodes and four signal lines;

[0008] The back side of the active electrode has a micron-sized groove, and a ceramic coating is laid in the groove to form four independent insulating microchannels.

[0009] The two pairs of impedance measurement electrodes are respectively disposed on the surface of the active electrode to form four contacts: A1, B1, B2, and A2.

[0010] The four signal lines pass through the corresponding insulated microchannels and are laser-microwelded or bonded to the back of the four contacts using conductive adhesive.

[0011] Preferably, the ceramic coating is an insulating material with high temperature resistance and high dielectric strength.

[0012] Preferably, when the two pairs of impedance measurement electrodes are working, one pair of electrodes acts as a signal excitation source to inject broadband current into the biological tissue, while the other pair of electrodes detects the voltage change of the biological tissue. This separates the excitation path from the detection path, effectively eliminating the influence of polarization impedance at the electrode-tissue interface, and the measurement loop path passes through the ablated tissue area.

[0013] An impedance measurement signal injection method for a plasma surgical system, using the aforementioned plasma electrode with integrated broadband impedance sensing function, is characterized by comprising the following steps:

[0014] Twenty-one frequency points are selected in a frequency range of 1 kHz to 5 MHz, which are logarithmically evenly distributed. The sinusoidal function of the corresponding frequency point is used as the basic signal, and multiple sinusoidal functions are superimposed to form a multi-frequency sinusoidal excitation signal.

[0015] A genetic algorithm is used to globally optimize the initial phase of each frequency point in a multi-frequency sinusoidal excitation signal, thereby optimizing the peak factor of the signal.

[0016] The optimized multi-frequency sinusoidal excitation signal was injected in parallel into the biological tissue to be measured, and the injection of the broadband impedance measurement signal was completed within 10 milliseconds.

[0017] Preferably, the multi-frequency sinusoidal excitation signal is composed of multiple sinusoidal functions with different amplitudes and phases superimposed.

[0018] Preferably, after the phase is optimized by a genetic algorithm, the peak factor of the multi-frequency sinusoidal excitation signal is no greater than 2.8.

[0019] A tumor edge recognition method for a plasma surgical system, using a plasma electrode with integrated broadband impedance sensing function, includes an offline initialization calculation stage and an online real-time processing stage, the specific steps of which are as follows:

[0020] Offline initialization calculation phase:

[0021] Construct an integral kernel matrix, introduce a regularization operator to solve the ill-conditioned problem of linear inversion, and calculate the regularized pseudo-inverse matrix;

[0022] The regularized pseudo-inverse matrix is ​​stored in system memory as a constant lookup table;

[0023] Online real-time processing stage:

[0024] Broadband complex impedance spectrum of biological tissue in contact with the tip of the cutter;

[0025] The relaxation distribution function of the biological tissue is calculated by calling the regularized pseudo-inverse matrix stored in memory;

[0026] The main peak position is quickly located in the relaxation distribution function, the relaxation time of biological tissue is extracted, and then the corresponding relaxation frequency is obtained.

[0027] Based on the relaxation frequency of biological tissues, the tissue type targeted by the scalpel can be determined, thereby enabling the identification of tumor margins.

[0028] Preferably, the impedance model of biological tissue corresponds to the series structure of parallel RC units, and each parallel RC unit corresponds to a bell-shaped peak in the relaxation distribution function, with the center position of the bell-shaped peak corresponding to the relaxation time of the biological tissue.

[0029] Preferably, the relaxation frequency range of normal biological tissue is 0.001 to 0.1 MHz, and the relaxation frequency range of cancerous tissue is 0.1 to 2 MHz. By comparing the relaxation frequency of the tissue to be tested with the above range, it can be determined whether the tissue has become cancerous.

[0030] Preferably, a broadband microcurrent is injected into the biological tissue before plasma is excited, and a broadband complex impedance spectrum is collected to enable early judgment of the current contact tissue type.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] The plasma electrode integrates ablation and broadband impedance sensing, eliminating the need for additional sensing probes. The four-electrode measurement method completely eliminates the influence of polarization impedance at the electrode-tissue interface, significantly improving measurement accuracy. The special ceramic insulated microchannel is heat-resistant and interference-resistant, and the signal line connection is robust, ensuring stable operation throughout the entire procedure.

[0033] The impedance measurement signal injection method employs multi-frequency parallel injection to rapidly complete broadband impedance spectrum acquisition, meeting real-time monitoring requirements. By optimizing the signal phase through a genetic algorithm, the peak factor is reduced, the system signal-to-noise ratio is improved, and high-precision data is obtained within a short measurement window.

[0034] The tumor edge recognition method extracts feature parameters based on distributed relaxation time, eliminating the need for time-consuming model fitting; offline pre-computation of the pseudo-inverse matrix allows for millisecond-level recognition with only simple matrix operations online; it can determine tissue type in advance before plasma excitation, effectively avoiding accidental cutting of normal tissue and significantly improving the accuracy and safety of tumor resection. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a novel plasma electrode structure;

[0036] Figure 2 This is a schematic diagram of the four-electrode method measurement;

[0037] Figure 3The following are time-domain plots of the multi-frequency impedance measurement signal, where (a) is the time-domain plot of the signal under zero phase, and (b) is the time-domain plot of the signal after optimization by the genetic algorithm.

[0038] Figure 4 Frequency domain diagram of multi-frequency impedance measurement signal;

[0039] Figure 5 This is a schematic diagram illustrating the principle of extracting Cole relaxation frequencies from biological tissues based on Distribution of Relaxation Times (DRT).

[0040] Figure 6 A diagram of biological tissue impedance model;

[0041] Figure 7 This is a flowchart illustrating the rapid extraction of the Cole relaxation time τ based on distributed relaxation time (DRT).

[0042] In the diagram: 1. Active electrode; 2. Ceramic coating; 3. Reflux electrode; 4. Measuring electrode; 5. Signal line. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] Example 1

[0045] This embodiment proposes a plasma electrode structure, such as... Figure 1 As shown, two pairs of miniature impedance measurement electrodes 4 are integrated at the active electrode 1 of the plasma electrode, realizing the integrated function of plasma ablation and broadband impedance sensing. This eliminates the need for additional independent sensing probes and does not require changes to the main structure and operation process of the existing plasma surgery system, ensuring the continuity and minimal invasiveness of the surgical operation.

[0046] Micrometer-level grooves are formed on the back side of the metal active electrode 1, and a high-temperature resistant, high-dielectric-strength ceramic coating 2 is laid to form four independent insulating microchannels. The high-temperature resistance can withstand the localized high temperatures generated during plasma surgery, preventing the coating from melting or carbonizing and ensuring stable insulation performance throughout the procedure. The high dielectric strength ensures complete electrical isolation between the four miniature signal lines 5 and between the signal lines 5 and the active electrode 1, effectively preventing signal crosstalk between different signal lines 5 and avoiding interference from the high-power radio frequency energy of the active electrode 1 with the weak impedance measurement signal. The four miniature signal lines 5 pass through their respective insulating microchannels and are laser-welded or bonded to the back of contacts A1, B1, B2, and A2 using conductive adhesive, ensuring extremely low contact resistance and a strong physical connection. The extremely low contact resistance ensures that the weak impedance measurement signal is transmitted without significant loss, preserving the original characteristics of the signal to the maximum extent and improving measurement accuracy. The strong physical connection can withstand repeated bending, rotation, and vibration of the electrode during surgery, avoiding poor contact or wire breakage and ensuring the safety of the procedure.

[0047] The principle of four-electrode impedance measurement is as follows: Figure 2 As shown, four miniature measuring electrodes 4 are distributed on the surface of the active electrode 1, forming an impedance detection circuit when in contact with local biological tissue. During operation, electrode pair A injects a broadband current as a signal excitation source, while electrode pair B detects voltage changes. The four-electrode method separates the excitation path from the detection path, effectively eliminating the influence of polarization impedance at the electrode-tissue interface compared to the traditional two-electrode method. Polarization impedance is the most significant source of error in two-electrode measurements, and its value varies with various factors such as contact pressure, tissue humidity, and electrode surface condition, leading to unstable measurement results and poor repeatability. The four-electrode method used in this invention completely eliminates this error in principle, and the measurement results only reflect the impedance characteristics of the biological tissue itself. Simultaneously, the measuring circuit path effectively passes through the ablated tissue area, accurately characterizing the real-time state changes of the local tissue during the ablation process, providing continuous and accurate feedback information for the surgical procedure.

[0048] Example 2

[0049] This embodiment provides a method for injecting impedance measurement signals into a plasma surgical system. This embodiment uses a multi-frequency sinusoidal function as the signal excitation source, and its time-domain and frequency-domain diagrams are shown below. Figure 3 , Figure 4 As shown. The excitation signal consists of N frequencies. Amplitude Phase is It is formed by the superposition of sine functions, and its mathematical expression is as follows:

[0050]

[0051] To achieve wideband coverage in a very short time, 21 frequency points were selected in a logarithmically uniform distribution within the 1kHz–5MHz frequency range. This frequency range covers the main distribution range of Cole relaxation frequencies in biological tissues, enabling the complete capture of the electrical characteristic differences between normal and cancerous tissues. The logarithmically uniform frequency distribution ensures sufficient sampling density in both low and high frequency bands, avoiding insufficient sampling in areas of drastic impedance changes in the low-frequency band and guaranteeing the overall measurement accuracy of the impedance spectrum. Compared to the traditional point-by-point frequency sweep method, this parallel injection method significantly shortens the impedance spectrum acquisition cycle and is the core technical foundation for achieving rapid characterization of local tissue impedance. The traditional point-by-point frequency sweep method requires sequential measurement at each frequency point, and completing the acquisition of the entire frequency band typically takes hundreds of milliseconds or even several seconds, which cannot keep up with the rapid changes in tissue state during surgery.

[0052] In multi-frequency sinusoidal signals, directly using zero phase for each frequency component will generate extremely high instantaneous peak voltages, reducing the system's signal-to-noise ratio. Therefore, a genetic algorithm is used to globally optimize the initial phase of each frequency point in the multi-frequency sinusoidal excitation signal, thereby optimizing the signal's peak factor. For example... Figure 3 As shown, the peak factor of the signal at zero phase is 4.5082. After optimization using a genetic algorithm, the peak factor is reduced to 2.7907. The optimized signal exhibits a more uniform energy distribution in the time domain, significantly reducing instantaneous peak voltage and preventing distortion caused by the signal exceeding the system's linear operating range. Simultaneously, it maximizes the average power of the injected current, ensuring high-precision impedance data is acquired within an extremely short measurement window on the order of 10ms. This 10ms measurement window meets the real-time monitoring requirements for rapid changes in tissue state during plasma surgery, enabling synchronous impedance measurement and plasma ablation operations, and avoiding surgical errors caused by measurement lag.

[0053] Example 3

[0054] This embodiment provides a tumor edge recognition method for a plasma surgical system, using the Cole relaxation frequencies of cancerous and non-cancer tissues. Significant differences exist. Cancer reduces cell polarization capacity, thereby decreasing cell capacitance. The Cole relaxation frequency of normal tissue is 0.001–0.1 MHz, while in cancerous tissue it shifts to a higher frequency (0.1–2 MHz). This difference in electrical properties is the physical basis for tumor edge recognition in this embodiment. Essentially, the cell membrane structure and function change after cell carcinogenesis, leading to a significant change in cell polarization characteristics. Based on the significant difference in the Cole relaxation frequency between benign and cancerous tissues, this embodiment uses distributed relaxation times (DRT) to rapidly extract the Cole relaxation frequency of biological tissue, achieving rapid tumor edge recognition. The measuring electrode 4 integrated on the active electrode 1 injects a broadband microcurrent into A before plasma excitation, enabling early determination of the current contact tissue type. This allows for confirmation of tissue nature before ablation, avoiding accidental removal of normal tissue and improving the accuracy and safety of tumor resection.

[0055] The principle of extracting the Cole relaxation frequency of biological tissue based on distributed relaxation times (DRT) is as follows: Figure 5 As shown. The Distributed Relaxation Time (DRT) method treats the total impedance as an infinite number of parallel resistor-capacitor units connected in series with a relaxation time τ. The core of this method lies in using mathematical transformations to obtain the impedance spectrum from the measured impedance spectrum. Relaxation time distribution function of the unconverted impedance model Compared to traditional parameter fitting methods based on pre-defined models, the distributed relaxation time (DRT) method does not require prior assumptions about the impedance model structure of biological tissues, avoiding fitting errors caused by inappropriate model selection. Furthermore, the computational process is more efficient, making it suitable for real-time processing in embedded surgical devices. For an ideal resistive-capacitive (RC) unit, the relaxation time distribution function... The expression is a discrete Dirac function, and its position is... equal Each RC constant phase (RQ) unit is in The middle corresponds to a bell-shaped peak, the center of which is located The width of the peak is determined by the exponential function. Decide, The smaller the value, the wider the peak in the spectrum, indicating a more dispersed temporal distribution of the relaxation process.

[0056] Impedance models of biological tissues, such as Figure 6 As shown, the bioimpedance model consists of a resistance value of The resistor is connected in parallel with a constant-phase element Q with parameters Q and α, and then connected with a resistor with a resistance of α. The equivalent impedance Z of the series resistors is expressed as follows:

[0057]

[0058]

[0059] in, This is the low-frequency limit of Z, corresponding to the resistance of the extracellular fluid in biological tissues; Z is the high-frequency limit, corresponding to the total resistance of intracellular and extracellular fluids in biological tissues; It measures frequency. It is the Cole relaxation frequency. For Cole's relaxation time, It is a dimensionless constant. This reflects the degree to which the impedance characteristics of biological tissue deviate from an ideal RC circuit.

[0060] Biological tissue models are typical resistor-capacitor constant-phase (RQ) circuits; therefore, the Cole relaxation time τ can be rapidly extracted based on distributed relaxation time (DRT) without the need for time-consuming model parameter identification. The flowchart for rapidly extracting the Cole relaxation time τ based on distributed relaxation time (DRT) is shown below. Figure 7 As shown, the process is divided into two stages: offline initialization computation and online real-time processing. In the offline initialization stage, the integral kernel matrix A is constructed, and the Tikhonov regularization operator is introduced. To solve the ill-conditioned problem of linear inversion, calculate the regularized pseudo-inverse matrix. The calculated constant matrix The data is stored in memory as a constant lookup table. The offline computation process pre-completes the computationally intensive matrix inversion operation, significantly reducing the computational burden in the online processing stage and enabling the entire recognition process to be completed in milliseconds. In the online real-time processing stage, the broadband complex impedance spectrum collected from the cutter head tip is acquired. Calling memory ,implement This step requires only simple matrix multiplication, resulting in extremely fast computation and low hardware requirements for the surgical equipment. The calculated relaxation distribution function... Quickly locate the main peak position This method enables rapid extraction of characteristic parameters. The main peak position corresponds to the most important relaxation process in biological tissues, which can accurately reflect the overall electrical properties of tissues and is a key characteristic parameter for distinguishing normal tissues from cancerous tissues.

[0061] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. A plasma electrode integrating broadband impedance sensing function, comprising an active electrode and a reflux electrode, characterized in that, It also includes two pairs of impedance measurement electrodes and four signal lines; The back side of the active electrode has a micron-sized groove, and a ceramic coating is laid in the groove to form four independent insulating microchannels. The two pairs of impedance measuring electrodes are respectively disposed on the surface of the active electrode to form four contacts A1, B1, B2, and A2; The four signal lines pass through the corresponding insulating microchannels and are laser micro-welded or bonded to the back of the four contacts using conductive adhesive. When the two pairs of impedance measurement electrodes are working, one pair of electrodes acts as a signal excitation source to inject broadband current into the biological tissue, while the other pair of electrodes detects the voltage change of the biological tissue, thus separating the excitation path from the detection path, and the measurement loop path passes through the ablated tissue area.

2. The plasma electrode with integrated wideband impedance sensing function according to claim 1, characterized in that, The ceramic coating is an insulating material that is resistant to high temperatures and has high dielectric strength.

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