Current field source self-correction positioning method and system in multiple disturbance environment
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2026-04-21
- Publication Date
- 2026-05-29
Smart Images
Figure CN122096970A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of medical device and precision measurement technology, and relates to a method and system for current field source correction and positioning under multiple disturbance environments. Background Technology
[0002] Interventional procedures such as lung nodule biopsy and tumor ablation play a crucial role in the early treatment of lung cancer, and their success highly depends on precise navigation and localization of the lesion. In recent years, the rapid development of bronchoscopic navigation technology and robot-assisted systems has provided new avenues for minimally invasive biopsy and ablation treatment of lung nodules. However, the navigation efficiency of these methods in actual clinical practice is still severely limited by the mismatch between preoperative imaging and the intraoperative human body. This stems from the dynamic deformation of the lung parenchyma caused by respiration and heartbeat, resulting in a significant deviation between the navigation path constructed based on preoperative static CT data and the actual spatial coordinates of the lesion during surgery; the drift error can typically exceed 10 mm. Although intraoperative imaging technologies such as cone-beam computed tomography (CBCT) can provide real-time position compensation, their high equipment cost, complex clinical procedures, and continuous ionizing radiation limit their large-scale application.
[0003] However, most existing electrical methods are based on quasi-static, linear physical models, neglecting the complex physiological environment of the thoracic cavity. In actual interventional surgery, lung deformation caused by respiration and periodic disturbances caused by heartbeat not only cause mechanical displacement of the instrument tip but also lead to dynamic shifts in the distribution of effective conductivity within the thoracic cavity. This dual coupling effect of geometric deformation and physical property evolution causes severe nonlinear distortion in the current field, resulting in non-negligible coordinate drift in traditional positioning algorithms based on static libraries or fixed sensitivity matrices. Summary of the Invention
[0004] In view of this, the purpose of the present invention is to provide a current field source source correction and positioning method and system under multiple disturbance environments.
[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for correcting and locating the source of current field under multiple disturbances includes the following steps: S1: Establish a quasi-static current field in the space region to be measured, and use the dynamic coupling matrix to describe the coupling relationship between the current field change, deformation gradient and conductivity fluctuation caused by physiological disturbance. S2: Construct a multiphysics correlation model, collect the boundary potential signal of the body surface electrode array, and simultaneously acquire the physiological perturbation phase signal characterizing the geometric deformation of the space region to be measured; S3: Based on the physiological disturbance phase signal, retrieve and extract the corresponding deformation compensation factor from the preset deformation feature database, correct the parameters of the pre-constructed numerical simulation field equation, and generate a dynamic Jacobian matrix that matches the current deformation state. S4: The boundary potential signal acquired in real time is used as a constraint condition and substituted into the dynamic Jacobian matrix to solve the inverse problem, thereby decoupling the pseudo-displacement component caused by the physiological disturbance and calculating the absolute coordinates of the current field source in three-dimensional space.
[0006] Furthermore, the establishment of a quasi-static current field in the test space region described in step S1 includes: injecting a weak alternating current with constant amplitude and frequency into the non-uniform conductive medium in the test space region through an interventional probe, so as to establish a quasi-static current field in the test space region.
[0007] Furthermore, step S1, which describes the coupling relationship between the current field change, deformation gradient, and conductivity fluctuation caused by physiological disturbance using a dynamic coupling matrix, includes the following steps: First, consider the basic Poisson equation for the current field under quasi-static conditions:
[0008] in, Indicates the potential distribution. Indicates the conductivity distribution. Represents the coordinates of the current source as it shifts over time; Assume the reference coordinate system in the undeformed state is The spatial coordinate system of the real-time deformation state is Location mapping relationship: ,in, It is a displacement field caused by respiration and heartbeat, introducing a deformation gradient tensor. :
[0009] It is a unit tensor, representing the undistorted state, and defines a Jacobian determinant. , to represent the rate of change of volume, that is: Assume that the local effective conductivity and volume change satisfy a linear exponential relationship:
[0010] Under small deformations, it simplifies to a linear perturbation:
[0011] Indicates the reference conductivity. This indicates the electrical conductivity disturbance caused by pulmonary respiration. This represents the conductivity perturbation caused by the heartbeat; the governing equations in the spatial coordinate system are transformed into the reference coordinate system to establish the relationship between the measured voltage and the initial model; and the effective coupled conductivity tensor in the reference frame is obtained using the Piola transform. Expressed as:
[0012] Expanding and linearizing the above equation, we obtain the total differential expression of the boundary measurement potential:
[0013] in, This represents the sensitivity matrix to potential changes caused by source coordinate shift. This is the dynamic conductivity-deformation coupling matrix, which includes geometric terms. and property terms The geometric terms The physical property item is used to describe the change in the direction of current lines due to tissue stretching / compression. Used to describe the change in resistivity of a medium due to lung inflation; Changes in boundary measurement voltage after finite element discretization Written as:
[0014] Coupling matrix The component form is represented as:
[0015] This represents the sensitivity distribution of the boundary measurement electrodes. The disturbance vector is represented as follows: The decoupled current field is expressed as:
[0016] The source displacement perturbation, representing respiration and heartbeat, is calculated by combining it with the measured total boundary potential matrix. The corrected point source coordinates are obtained.
[0017] Furthermore, step S2 specifically includes the following steps: The current injection electrode is installed at the tip of the interventional probe. After the current flows into the surgical area, it flows out from a certain measuring electrode. The reference electrode is fixed as electrode N. The current outflow electrode and the measuring electrode are reused. When an external electrode is used as the current outflow electrode, that electrode is not used for potential measurement in this measurement. The voltage of other external electrodes is measured. Electrode 1 through N-1 is used as the current outflow electrode in turn. During the cycle, the potential values of the remaining N-2 electrodes are collected to form a set of independent potential results. After traversing all the current-outflowing electrodes, a generator containing The measured potential matrix of each potential result :
[0018] This indicates that when the current flows out at the first point... When the first electrode is used, the vector composed of the potentials of all other measuring electrodes, with each component representing the measurement result of a pair of current electrodes, ultimately forms a complete measurement potential matrix. This is the total number of measuring electrodes.
[0019] Furthermore, step S3 specifically includes the following steps: In the preprocessing layer, signal decoupling is performed. Through FFT frequency domain processing, the current respiratory and heartbeat frequencies are identified, the signal is decomposed into components of different scales, ripples related to heartbeat and respiration are removed, and components reflecting probe displacement are retained. In the physical compensation layer, the dynamic sensitivity matrix is corrected by monitoring the mean fluctuation of the global potential, based on the sensitivity matrix. Respiratory phase signals are extracted, and a complete heart-respiratory cycle is divided into multiple discrete phases. Based on the current respiratory and heart-respiratory phase, the corresponding matrix is retrieved from the pre-calculated multi-state sensitivity library. This enables nonlinear compensation for geometric deformation and changes in conductivity.
[0020] Furthermore, in step S3, the extraction steps for the respiratory phase are as follows: S31: Constructing Feature Signals: In order to extract multi-channel body surface potential To extract respiratory features, a proxy signal sensitive to changes across the entire field is first constructed. The expansion and contraction of the lungs due to respiration cause an overall shift in the boundary potential. Calculate the real-time arithmetic mean of the potentials of all electrodes:
[0021] S32: Dynamic Baseline Drift Elimination: The proxy signal contains a low-frequency trend term caused by probe movement. Median sliding window filtering is used to estimate the signal baseline in real time. And remove it to obtain the pure respiratory wave component. :
[0022] S33: Phase Mapping and State Division: Analyzing the Processed Fluctuation Signal Using Hilbert Transform: Calculate analytic signals ; Extracting instantaneous phase ,in ; The continuous phases are divided into four typical respiratory physiological states: during inspiration, at the end of inspiration, during expiration, and at the end of expiration.
[0023] Furthermore, when the instantaneous phase range for At that time, the process is divided into the final intake state, and the maximum deformation correction matrix is called. Make corrections; when the instantaneous phase range for At that time, the state is divided into exhalation state, and the dynamic linear interpolation matrix is invoked. Make corrections; when the instantaneous phase range for At that time, the state is divided into the end-expiratory state, and the reference resting state matrix is invoked. Make corrections; when the instantaneous phase range for At that time, the state is divided into inhalation state, and the fast expansion correction matrix is invoked. Make corrections.
[0024] Furthermore, step S4 includes the following steps: In the inverse problem solving stage, coordinate calculation is performed using the compensated model. The coordinates are solved by minimizing the residual between the measured potential and the model's predicted potential using the least squares method. :
[0025] Iteration using the modified Jacobian matrix:
[0026] in It includes the partial derivatives of the contribution of the deformation gradient to the current field.
[0027] Furthermore, after calculating the absolute coordinates of the current field source in three-dimensional space, a Kalman filter is used to smooth the trajectory to ensure time continuity, and the optimized three-dimensional coordinates are output. .
[0028] On the other hand, the present invention provides a current field source calibration and positioning system under multiple disturbance environments, including a constant current source, an electrode array, an analog switch array, a signal detection and data acquisition circuit, a microprocessor, and a host computer; The constant current source includes a digitally synthesized sine wave signal source and a sine wave constant current source, used to generate a constant amplitude sine current. The analog switch array circuit is used to control the inflow of sinusoidal current into the electrode array; The signal detection and data acquisition circuit is used to realize the voltage measurement, potential detection and RMS conversion of the analog switch array, as well as signal filtering and amplification. Finally, after AD conversion, the signal is transmitted to the microprocessor. The microprocessor is used to control the selection of analog switches, control the constant current of the constant current source and the frequency of the digitally synthesized sine wave signal, and upload the collected signal to the host computer for processing via an opto-isolated serial port. The host computer is equipped with the current field self-correction and positioning method under multiple disturbance environments as described above, which is used to realize the current field self-correction and positioning.
[0029] The beneficial effects of this invention are as follows: by decoupling multiple perturbation components, this invention achieves self-correction and reconstruction of coordinates, thereby improving the accuracy of coordinate positioning at the end of surgical instruments.
[0030] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description
[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the field source coordinate self-calibration method; Figure 2 Electrode potential acquisition strategy; Figure 3 The current outflow electrode reuse and rotation strategy; Figure 4 The overall logic flowchart of the self-calibration positioning method provided by the present invention; Figure 5 The dynamic physical model of the thoracic cavity is shown, where (a) represents the distribution of physiological tissues and (b) represents the path of movement. Figure 6 To compare the experimental results before and after the introduction of the coordinate self-correction method; where (a) is the coordinate reconstruction trajectory of path ④, and (b) is the instantaneous error distribution diagram; Figure 7 This is a structural diagram of a field source coordinate self-calibration positioning system. Detailed Implementation
[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0033] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0034] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.
[0035] Example 1: This invention provides a method for correcting and locating the source of a current field under multiple disturbances. A quasi-static current field is established by injecting a constant-frequency, constant-current signal into a non-uniform conductive medium using an invasive probe, and boundary potential signals are acquired in real time using a surface electrode array. Simultaneously, a phase recognition algorithm is used to extract phase signals of physiological disturbances such as respiration or heartbeat. Finally, and most importantly, based on the real-time phase signals, the system Jacobian matrix is dynamically indexed from a pre-set deformation feature database and corrected to construct an inverse problem-solving model that matches the current deformation state. This decouples the pseudo-displacement components caused by physiological disturbances, achieving high-precision inversion and reconstruction of the three-dimensional coordinates of the source field.
[0036] Field source coordinate self-correction positioning, such as Figure 1 As shown, the movement of the field source causes changes in the current field, which in turn leads to regular changes in the boundary potential. Therefore, the coordinates of the field source can be deduced by measuring the boundary potential. However, the spontaneous activities (heartbeat, respiration) of physiological tissues (heart, lungs) cause deformation and conductivity evolution, which introduces new disturbances and coupling components into the boundary potential, leading to inaccurate positioning of the surgical instrument end-effector coordinates. This method is mainly aimed at solving this problem by decoupling multiple disturbance components to achieve self-correction and reconstruction of coordinates.
[0037] This method includes the following steps: Step 1: Establishing a quasi-static excitation current field: A weak alternating current with constant amplitude and frequency is injected into the non-uniform conductive medium in the space region to be measured through an interventional probe to establish a quasi-static current field in the space region to be measured. Step 2: Construct a multiphysics correlation model: Collect the boundary potential signal of the body surface electrode array, and simultaneously acquire the physiological perturbation phase signal characterizing the geometric deformation of the space region to be measured; Step 3: Dynamically correct the system feature matrix: Based on the physiological perturbation phase signal, retrieve and extract the corresponding deformation compensation factor from the preset deformation feature database, correct the parameters of the pre-constructed numerical simulation field equation, and generate a dynamic Jacobian matrix that matches the current deformation state. Step 4: Coordinate self-calibration inversion reconstruction: The boundary potential signal acquired in real time is used as a constraint condition and substituted into the dynamic Jacobian matrix to solve the inverse problem, thereby decoupling the pseudo displacement component caused by the physiological disturbance and calculating the absolute coordinates of the interventional probe in three-dimensional space.
[0038] In step one, the core challenge in locating the field source under multiple physiological perturbations (respiration, heartbeat) lies in the fact that the geometric deformation of the physical domain and the evolution of electrical properties occur simultaneously. To decouple these perturbations, it is necessary to derive and establish a coupling matrix that describes the change in current field, deformation gradient, and conductivity fluctuation.
[0039] First, consider the basic Poisson equation for the current field under quasi-static conditions:
[0040] in, Indicates the potential distribution. Indicates the conductivity distribution. This represents the coordinates of the current source as it shifts over time.
[0041] Assume the reference coordinate system (undeformed state) is The spatial coordinate system (real-time deformation state) is Location mapping relationship: ,in, It is a displacement field caused by respiration and heartbeat, introducing a deformation gradient tensor. :
[0042] It is a unit tensor, representing the undistorted state, and defines a Jacobian determinant. , to represent the rate of change of volume, that is: In actual interventional surgery, pulmonary conductivity dynamically changes with respiration (air volume). For simplicity, we assume that the local effective conductivity and volume change follow a linear exponential relationship:
[0043] It usually simplifies to a linear perturbation under small deformations:
[0044] Indicates the reference conductivity. This indicates the electrical conductivity disturbance caused by pulmonary respiration. This represents the conductivity perturbation caused by the heartbeat. The governing equations in the spatial coordinate system are transformed into the reference coordinate system to establish the relationship between the measured voltage and the initial model. Using the Piola transform, the effective coupled conductivity tensor in the reference frame is obtained. Expressed as:
[0045] Expanding and linearizing the above equation, we obtain the total differential expression of the boundary measurement potential:
[0046] in, This represents the sensitivity matrix to potential changes caused by source coordinate shift. This is the dynamic conductivity-deformation coupling matrix, which consists of two parts: 1. Geometric terms ( ): Describes the change in the direction of current lines due to the stretching / compression of tissue.
[0047] 2. Physical property terms ( ): Describes the change in resistivity of a medium due to lung inflation.
[0048] Changes in boundary measurement voltage after finite element discretization It can be written as:
[0049] Coupling matrix The component form is usually represented as:
[0050] This represents the sensitivity distribution of the boundary measurement electrodes. This represents the disturbance vector (breathing and heart rate and amplitude). Therefore, the decoupled current field can be expressed as:
[0051] By combining the perturbation vectors representing respiration and heartbeat with the measured total boundary potential matrix, the decoupled source displacement perturbation can be determined. The corrected point source coordinates are obtained.
[0052] In step two, coordinate calculation relies on the measurement of boundary potentials. However, obtaining complete boundary potentials is very difficult; only discrete potential values can be acquired using a limited number of measuring electrodes. The self-calibration solution for coordinates is nonlinear and ill-conditioned. More known boundary potentials are more beneficial for coordinate calculation. Therefore, rapidly acquiring a large number of independent boundary potentials with limited measuring electrodes is crucial. This paper proposes an electrode potential acquisition strategy for the coordinate self-calibration method, such as... Figure 2 As shown, N represents the number of boundary measurement electrodes.
[0053] The current injection electrode (positioning electrode) is installed at the tip of the interventional probe. After the current flows into the surgical area, it flows out from a certain measuring electrode. The reference electrode is fixed as electrode number N (zero potential). To obtain more independent measurement results, the current-outflow electrode and the measuring electrode are multiplexed. When an external electrode is used as the current-outflow electrode, that electrode is not used for potential measurement in this measurement; instead, the voltage of other external electrodes is measured. The electrode rotation strategy is as follows: Figure 3 As shown, electrodes 1 through N-1 are used as current-flowing electrodes in turn, and the potential values of the remaining N-2 electrodes are collected during the cycle to form a set of independent potential results.
[0054] After traversing all the current-outflowing electrodes, a generator containing The measured potential matrix of each potential result .
[0055]
[0056] This indicates that when the current flows out at the first point... When the first electrode is used, the vector composed of the potentials of all other measuring electrodes, with each component representing the measurement result of a pair of current electrodes, ultimately forms a complete measurement potential matrix. This is the total number of measuring electrodes.
[0057] In step three, after establishing the dynamic coupling matrix and collecting the boundary potential data, coordinate self-calibration calculation is performed. The measured signal is regarded as the superposition of the target displacement signal and the physiological background noise, and the two are decoupled by the physical model-driven method.
[0058] First, in the preprocessing layer, signal decoupling is carried out. Respiration and heartbeat have obvious characteristic distributions compared with excitation signals. Through FFT frequency domain processing, the current main frequencies of respiration and heartbeat are identified, the signals are decomposed into components of different scales, the ripples related to heartbeat and respiration are removed, and the components reflecting probe displacement are retained.
[0059] Then, in the physical compensation layer, the dynamic sensitivity matrix is corrected. Due to tissue deformation, the sensitivity matrix... It changes over time. By monitoring the mean fluctuation of the global potential, the respiratory phase signal is extracted, and a complete heartbeat and respiratory cycle is divided into multiple discrete phases. Based on the current respiratory and heartbeat phase, the corresponding matrix is called from the pre-calculated "multi-state sensitivity library". This enables nonlinear compensation for geometric deformation and changes in conductivity.
[0060] In step four, during the inverse problem solving stage, the compensated model is used to calculate the coordinates. The coordinates are solved by minimizing the residual between the measured potential and the model's predicted potential using the least squares method. :
[0061] Iteration using the modified Jacobian matrix:
[0062] in It includes the partial derivatives of the contribution of the deformation gradient to the current field.
[0063] like Figure 4 The diagram illustrates the process from signal input to coordinate output, highlighting the processing methods for two key steps: physiological perturbation phase recognition and dynamic correction of the Jacobian matrix. The overall flow of this method can be described as follows: Input: Measurement of real-time boundary potential Pre-calculate the dynamic coupling basic matrix library; Step 1: Signal decoupling, using wavelet decomposition to extract respiratory signals. and heartbeat Element; Step 2: Phase estimation from extracted respiratory disturbance potentials China has determined ; Step 3: Model Adjustment: Apply different sensitivity matrices based on the phase. Step 4: Coordinate calculation, initialization starting from the previous frame. The adjusted sensitivity matrix is updated using the Gauss-Newton iterative method. ; Step 5: Output. The trajectory is smoothed using a Kalman filter to ensure time continuity; Return: Optimized 3D coordinates .
[0064] It should be noted that in step 2, the phase extraction follows these rules: (1) Constructing characteristic signals: In order to obtain multi-channel body surface potential To extract respiratory features, a proxy signal sensitive to changes across the entire field is first constructed. The expansion and contraction of the lungs due to respiration cause an overall shift in the boundary potential. Calculate the real-time arithmetic mean of the potentials of all electrodes:
[0065] (2) Dynamic baseline drift elimination: The proxy signal contains a low-frequency trend term caused by probe movement, and the signal baseline is estimated in real time using median sliding window filtering. And remove it to obtain the pure respiratory wave component. :
[0066] (3) Phase mapping and state division: Analyzing the processed wave signal using the Hilbert transform: ① Calculate the analytical signal: ; ② Extracting the instantaneous phase: ,in ; ③ State mapping: The continuous phases are divided into four typical respiratory physiological states, as shown in Table 1: Table 1
[0067] To further illustrate the specific implementation of the field source coordinate self-calibration method and verify its accuracy and feasibility in puncture surgery positioning, a simplified physical model of the thoracic cavity and a simulation puncture surgery platform were constructed, such as... Figure 5 As shown in (a) and (b), a robotic arm carrying a surgical probe is used as the actuator.
[0068] A layer of fresh pigskin and fat was laid along the inner circumference of a cylindrical water tank to simulate the chest wall interface. The tank was filled with a transparent gelatin solution, and the conductivity was adjusted to 0.7 S / m to approximate human blood. Fresh pig heart and lung tissue was placed above the tank to simulate the anatomical heterogeneity and anisotropy of the lungs.
[0069] A small slice of pig lung was designated as the surgical target (nodule). To assess the system's anti-interference capability, a copper cylinder was placed in the field to simulate the conductivity of surgical instruments or implants. A local current source was integrated at the tip of the puncture probe (2 mm in diameter), and the insertion angle and speed were controlled by a high-precision robotic arm.
[0070] Dynamic physiological movement is achieved by connecting an external low-power air pump to the pig's trachea via a sealed catheter. By controlling the air pump frequency (set to 0.25 Hz, or 15 breaths / minute) and tidal volume, rhythmic expansion and contraction of the lung tissue are induced, dynamically altering the lung geometry and its effective electrical conductivity.
[0071] A constant current with an amplitude of 1mA and a frequency of 1kHz is injected through the probe tip. The boundary potential is measured by a 16-channel surface electrode array. The raw boundary potential data is processed in real time by a self-calibration algorithm, which decouples the potential fluctuations induced by respiration from the point source signal and finally outputs three-dimensional coordinates.
[0072] Place the probe tip at the model starting point. The air pump is started to control the rhythmic contraction and relaxation of the pig lungs (0.25Hz, 15 times / minute). After the respiratory rate stabilizes for 2-3 cycles, the data acquisition system is started. The probe travels along the preset path ④ at a speed of 1mm / s to the target point (-60,0) to a depth of 30mm, and records the real coordinates returned by the robotic arm encoder. Simultaneously, 16-channel potentials are acquired. ,Will Align the air pump phase and probe coordinates with a unified timestamp, extract the respiratory phase, and call the corresponding deformation Jacobian matrix. deal with Calculate the final positioning trajectory and error.
[0073] Figure 6 To compare the experimental results before and after introducing the coordinate self-calibration method, Figure 6 In Figure (a), the coordinate reconstruction trajectory of path ④ is shown. The red curve represents the traditional static reconstruction trajectory (with significant undulations); the green curve represents the self-correcting reconstruction trajectory of this invention (which is straight); and the straight black dashed line represents the actual path preset by the probe. The comparison of the two curves visually demonstrates the beneficial effects of this invention in eliminating physiological motion artifacts and achieving high-precision coordinate reconstruction and positioning. Static reconstruction (red, without self-correction) exhibits severe sinusoidal oscillations in the direction perpendicular to the path axis, which is a coordinate shift caused by respiratory disturbances. In contrast, the introduction of the self-correction method (green) effectively suppresses these artifacts and maintains a linear trajectory consistent with the actual situation. Figure 6(b) is the instantaneous error distribution plot. The static method shows periodic error spikes synchronized with the respiratory rate, while the self-calibration method (green) shows robust coordinate tracking performance, with the root mean square error (RMSE) decreasing from 2.97 mm to 0.29 mm.
[0074] Example 2: like Figure 7 As shown, this embodiment provides a current field self-calibration positioning system under multiple disturbance environments, including a constant current source, an electrode array, an analog switch array, a signal detection and data acquisition circuit, a microprocessor, and a host computer. The constant current source generates a constant amplitude sinusoidal current and measures the electrical signal on the body surface electrodes through the analog switch array circuit and the signal detection and data acquisition circuit. The measured data is then sent to the microprocessor via a serial port and then transmitted to the host computer to provide data for coordinate self-calibration reconstruction.
[0075] The signal detection and data acquisition circuit is used to realize the voltage measurement, potential detection and RMS conversion of the analog switch array, as well as signal filtering and amplification. Finally, after AD conversion, the signal is transmitted to the microprocessor.
[0076] The microprocessor is used to control the selection of analog switches, control the constant current of the constant current source and the frequency of the digitally synthesized sine wave signal, and upload the acquired signal to the host computer for processing via an opto-isolated serial port.
[0077] The host computer is equipped with the current field source self-correction and positioning method under multiple disturbance environments as described in Example 1, so as to realize the current field source self-correction and positioning.
[0078] Example 3: An electronic device, including a memory and a processor; The memory is used to store computer programs; The processor is configured to implement the method described in Embodiment 1 when executing the computer program.
[0079] Example 4: A computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described in Embodiment 1.
[0080] Example 5: A computer program product includes a computer program that, when executed by a processor, implements the method described in Example 1.
[0081] In the above embodiments, the reference to "this embodiment" in the specification indicates that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least some embodiments, but not necessarily all embodiments. Multiple appearances of "this embodiment" do not necessarily refer to the same embodiment.
[0082] In the above embodiments, although the invention has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory structures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed. The embodiments of the invention are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims.
[0083] As will be understood by those skilled in the art, the computer-readable storage medium described in this embodiment allows for the implementation of all or part of the steps in the above method embodiments by computer program-related hardware. The aforementioned computer program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.
[0084] The electronic terminal provided in this embodiment includes a processor, a memory, a transceiver, and a communication interface. The memory and the communication interface are connected to the processor and the transceiver and complete communication between them. The memory is used to store computer programs, the communication interface is used to perform communication, and the processor and the transceiver are used to run the computer programs, so that the electronic terminal performs the steps of the above method.
[0085] In this embodiment, the memory may include random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device.
[0086] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.
[0087] This invention can be used in a wide range of general-purpose or special-purpose computing system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.
[0088] This invention can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.
[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for correcting and locating the source of a current field under multiple disturbances, characterized in that: Includes the following steps: S1: Establish a quasi-static current field in the space region to be measured, and use the dynamic coupling matrix to describe the coupling relationship between the current field change, deformation gradient and conductivity fluctuation caused by physiological disturbance. S2: Construct a multiphysics correlation model, collect the boundary potential signal of the body surface electrode array, and simultaneously acquire the physiological perturbation phase signal characterizing the geometric deformation of the space region to be measured; S3: Based on the physiological disturbance phase signal, retrieve and extract the corresponding deformation compensation factor from the preset deformation feature database, correct the parameters of the pre-constructed numerical simulation field equation, and generate a dynamic Jacobian matrix that matches the current deformation state. S4: The boundary potential signal acquired in real time is used as a constraint condition and substituted into the dynamic Jacobian matrix to solve the inverse problem, thereby decoupling the pseudo-displacement component caused by the physiological disturbance and calculating the absolute coordinates of the current field source in three-dimensional space.
2. The current field source source correction and positioning method under multiple disturbance environments according to claim 1, characterized in that: The step S1 of establishing a quasi-static current field in the space region to be measured includes: injecting a weak alternating current with constant amplitude and frequency into the non-uniform conductive medium in the space region to be measured through an interventional probe, so as to establish a quasi-static current field in the space region to be measured.
3. The current field source source correction and positioning method under multiple disturbance environments according to claim 1, characterized in that: Step S1 describes the coupling relationship between the changes in the current field caused by physiological disturbances, deformation gradient, and conductivity fluctuations using a dynamic coupling matrix. Includes the following steps: First, consider the basic Poisson equation for the current field under quasi-static conditions: in, Indicates the potential distribution. Indicates the conductivity distribution. The coordinates of the current source are represented by its displacement over time. Assume the reference coordinate system in the undeformed state is The spatial coordinate system of the real-time deformation state is Location mapping relationship: ,in, It is a displacement field caused by respiration and heartbeat, introducing a deformation gradient tensor. : It is a unit tensor, representing the undistorted state, and defines a Jacobian determinant. , to represent the rate of change of volume, that is: Assume that the local effective conductivity and volume change satisfy a linear exponential relationship: Under small deformations, it simplifies to a linear perturbation: Indicates the reference conductivity. This indicates the electrical conductivity disturbance caused by pulmonary respiration. This represents the conductivity perturbation caused by the heartbeat; the governing equations in the spatial coordinate system are transformed into the reference coordinate system to establish the relationship between the measured voltage and the initial model; and the effective coupled conductivity tensor in the reference frame is obtained using the Piola transform. Expressed as: Expanding and linearizing the above equation, we obtain the total differential expression of the boundary measurement potential: in, This represents the sensitivity matrix to potential changes caused by source coordinate shift. This is the dynamic conductivity-deformation coupling matrix, which includes geometric terms. and property terms The geometric terms The physical property item is used to describe the change in the direction of current lines due to tissue stretching / compression. Used to describe the change in resistivity of a medium due to lung inflation; Changes in boundary measurement voltage after finite element discretization Written as: Coupling matrix The component form is represented as: This represents the sensitivity distribution of the boundary measurement electrodes. The disturbance vector is represented as follows: The decoupled current field is expressed as: The source displacement perturbation, representing respiration and heartbeat, is calculated by combining it with the measured total boundary potential matrix. The corrected point source coordinates are obtained.
4. The current field source source correction and positioning method under multiple disturbance environments according to claim 1, characterized in that: Step S2 specifically includes the following steps: The current injection electrode is installed at the tip of the interventional probe. After the current flows into the surgical area, it flows out from a certain measuring electrode. The reference electrode is fixed as electrode N. The current outflow electrode and the measuring electrode are reused. When an external electrode is used as the current outflow electrode, that electrode is not used for potential measurement in this measurement. The voltage of other external electrodes is measured. Electrode 1 through N-1 is used as the current outflow electrode in turn. During the cycle, the potential values of the remaining N-2 electrodes are collected to form a set of independent potential results. After traversing all the current-outflowing electrodes, a generator containing The measured potential matrix of each potential result : This indicates that when the current flows out at the first point... When the first electrode is used, the vector composed of the potentials of all other measuring electrodes, with each component representing the measurement result of a pair of current electrodes, ultimately forms a complete measurement potential matrix. This is the total number of measuring electrodes.
5. The current field source source correction and positioning method under multiple disturbance environments according to claim 1, characterized in that: Step S3 specifically includes the following steps: In the preprocessing layer, signal decoupling is performed. Through FFT frequency domain processing, the current respiratory and heartbeat frequencies are identified, the signal is decomposed into components of different scales, ripples related to heartbeat and respiration are removed, and components reflecting probe displacement are retained. In the physical compensation layer, the dynamic sensitivity matrix is corrected by monitoring the mean fluctuation of the global potential, based on the sensitivity matrix. Respiratory phase signals are extracted, and a complete heart-respiratory cycle is divided into multiple discrete phases. Based on the current respiratory and heart-beat phase, the corresponding matrix is retrieved from the pre-calculated multi-state sensitivity library. This enables nonlinear compensation for geometric deformation and changes in conductivity.
6. The current field source source correction and positioning method under multiple disturbance environments according to claim 5, characterized in that: In step S3, the steps for extracting the respiratory phase are as follows: S31: Constructing Feature Signals: In order to extract multi-channel body surface potential To extract respiratory features, a proxy signal sensitive to changes across the entire field is first constructed. The expansion and contraction of the lungs due to respiration cause an overall shift in the boundary potential. Calculate the real-time arithmetic mean of the potentials of all electrodes: S32: Dynamic Baseline Drift Elimination: The proxy signal contains a low-frequency trend term caused by probe movement. Median sliding window filtering is used to estimate the signal baseline in real time. And remove it to obtain the pure respiratory wave component. : S33: Phase Mapping and State Division: Analyzing the Processed Fluctuation Signal Using Hilbert Transform: Calculate analytic signals ; Extracting instantaneous phase ,in ; The continuous phases are divided into four typical respiratory physiological states: during inspiration, at the end of inspiration, during expiration, and at the end of expiration.
7. The current field source source correction and positioning method under multiple disturbance environments according to claim 6, characterized in that: When the instantaneous phase range for At that time, the process is divided into the final intake state, and the maximum deformation correction matrix is called. Make corrections; when the instantaneous phase range for At that time, the state is divided into exhalation state, and the dynamic linear interpolation matrix is invoked. Make corrections; when the instantaneous phase range for At that time, the state is divided into the end-expiratory state, and the reference resting state matrix is invoked. Make corrections; when the instantaneous phase range for At that time, the state is divided into inhalation state, and the fast expansion correction matrix is invoked. Make corrections.
8. The current field source source correction and positioning method under multiple disturbance environments according to claim 1, characterized in that: Step S4 includes the following steps: In the inverse problem solving stage, coordinate calculation is performed using the compensated model. The coordinates are solved by minimizing the residual between the measured potential and the model's predicted potential using the least squares method. : Iteration using the modified Jacobian matrix: in It includes the partial derivatives of the contribution of the deformation gradient to the current field.
9. The current field source source correction and positioning method under multiple disturbance environments according to claim 8, characterized in that: After calculating the absolute coordinates of the current field source in three-dimensional space, a Kalman filter is used to smooth the trajectory to ensure time continuity, and the optimized three-dimensional coordinates are output. .
10. A current field source correction and positioning system under multiple disturbance environments, characterized in that: Includes constant current source, electrode array, analog switch array, signal detection and data acquisition circuit, microprocessor and host computer; The constant current source includes a digitally synthesized sine wave signal source and a sine wave constant current source, used to generate a constant amplitude sine current. The analog switch array circuit is used to control the inflow of sinusoidal current into the electrode array; The signal detection and data acquisition circuit is used to realize the voltage measurement, potential detection and RMS conversion of the analog switch array, as well as signal filtering and amplification. Finally, after AD conversion, the signal is transmitted to the microprocessor. The microprocessor is used to control the selection of analog switches, control the constant current of the constant current source and the frequency of the digitally synthesized sine wave signal, and upload the collected signal to the host computer for processing via an opto-isolated serial port. The host computer is equipped with a current field self-correction and positioning method under multiple disturbance environments as described in any one of claims 1-9, for realizing current field self-correction and positioning.