Device and method for evaluating contact direction and contact force of double-parameter sensor and balloon catheter

Abstract

The invention relates to a device and method for evaluating the contact direction and contact force of a double-parameter sensor and a balloon catheter, and the double-parameter sensor comprises a central tube elastomer structure, a packaging material, a multimode optical fiber, and a nanometer silver powder reflection layer. The evaluation device comprises the double-parameter sensor, an optical power generation and data acquisition unit and a computer, and the evaluation method combines an array type optical fiber optical power signal with an LSTM neural network model, excavates the change characteristics of a light intensity signal in time, accurately measures and calculates the nonlinear strain and force borne by the elastomer in real time, and calculates the nonlinear strain and force of the elastomer in real time. Three-dimensional reconstruction is carried out according to the strain and force of the elastomer, and the pushing force and torque of the catheter are correspondingly adjusted directly according to the magnitude and direction of the contact force in the navigation or ablation process, so that the problem that the catheter blindly punctures the blood vessel wall in the navigation process or the pulmonary vein opening is insufficiently blocked in the balloon ablation process is solved, and the safety of an operation is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of cryoballoon catheters, in particular to a device for evaluating contact direction and contact force of a dual-parameter sensor and a balloon catheter and an evaluation method thereof. Background Art

[0002] Cryoballoon ablation is an important means of treating atrial fibrillation. This ablation method generates low temperature on the balloon surface through the evaporation and heat absorption process of the refrigerant in the balloon. The balloon-shaped contact can cause tissue damage in a large area, block the conduction path of abnormal electrical signals, and achieve ablation effect. For cryoballoon ablation, the contact direction and contact force during the ablation process are crucial to the surgical ablation effect. Under the same contact direction, too small a contact force often means a poor contact state, resulting in insufficient ablation, poor surgical treatment effect and high risk of recurrence, while excessive contact force will cause serious complications such as myocardial tissue puncture and pericardial tamponade. In addition, the coaxiality between the cryoballoon and the pulmonary vein orifice is also very important for the surgical ablation effect. Poor coaxiality will cause part of the myocardial tissue to not come into contact with the balloon, resulting in poor ablation effect. At present, coaxiality is usually evaluated by the leakage of contrast agent. However, many patients have intolerance to contrast agents, so new technologies are needed to measure coaxiality. In summary, realizing dual-parameter sensing of contact direction and contact force during cryoballoon ablation is crucial to improving the safety and efficiency of ablation surgery and reducing the risk of complications.

[0003] In order to realize the dual-parameter sensing of contact direction and contact force of cryoballoon ablation catheter, the existing technology has proposed a variety of solutions, mainly including electrical sensing methods and optical sensing methods. Electrical sensing mainly senses the contact force and direction of the catheter through changes in parameters such as resistance or capacitance. Common electrical sensors such as strain gauges and capacitive sensors can detect small deformations or pressure changes, and then reflect the changes in contact force, with the advantages of high sensitivity and easy integration. However, the application of electrical sensing in cryoballoon ablation catheters faces some key challenges. Since the cryoballoon needs to work in an environment close to -60°C, this extreme low temperature will cause the resistance value of the electrical sensor to change dramatically, resulting in sensor performance degradation or damage. At the same time, condensation or frost may appear around the catheter during the freezing process. The condensation of these water vapors will affect the reliability of the electrical sensor and may cause increased signal noise or sensor failure. In addition, electrical sensors usually rely on precise electrode and wire connections. The difference in thermal expansion coefficients of materials in a freezing environment may cause the connection points to break or fail. Therefore, electrical sensing technology is difficult to apply in cryoballoon ablation catheters.

[0004] Based on this, optical sensing technology has become an ideal choice for contact direction and contact force sensing in cryoballoon ablation catheters. Optical sensors transmit optical signals through optical fibers and have good anti-interference and reliability. Fiber Bragg Grating (FBG) is currently the most commonly used optical sensing method for contact force sensing of cryoablation catheters. It detects strain and temperature changes by wavelength shift of light waves in optical fibers, thereby sensing contact force. Optical fibers have good mechanical flexibility and can be easily integrated into the central rod structure of cryoballoon ablation catheters, which gives FBG sensing technology significant advantages in contact force sensing of cryoballoon ablation catheters. However, FBG sensors will experience significant temperature drift due to their temperature sensitivity, and their wavelength shift sensitivity will be seriously affected in extreme freezing environments, resulting in a significant reduction in the measurement accuracy of contact force.

[0005] It can be seen that a more suitable optical sensing method needs to be developed to solve the problem of dual-parameter sensing of contact direction and contact force of the cryoballoon catheter under extreme freezing conditions during navigation and ablation. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a dual-parameter sensor.

[0007] Another technical problem to be solved by the present invention is to provide a balloon catheter contact direction and contact force evaluation device including the above-mentioned dual-parameter sensor.

[0008] Another technical problem to be solved by the present invention is to provide an evaluation method for the above-mentioned balloon catheter contact direction and contact force evaluation device.

[0009] In order to solve the above technical problems, the technical solutions proposed by the present invention are as follows:

[0010] A dual-parameter sensor comprises a central tube elastomer structure, packaging material, a multimode optical fiber 15 and a nano-silver powder reflective layer 16, wherein an instrument channel 17 is provided at the center of the central tube elastomer structure, a cavity is provided between the instrument channel 17 and the outer wall of the central tube elastomer structure, a sensor elastomer 13 with a hollow structure is provided on the surface of the cavity, and the hollow part is packaged and filled with packaging material, the multi-mode optical fiber 15 is distributed at equal angle intervals at the bottom of the central tube elastomer structure, laser is emitted into the aforementioned cavity from the multi-mode optical fiber, and a nano-silver powder reflective film is plated on the top of the cavity of the central tube elastomer structure as the nano-silver powder reflective layer 16.

[0011] The above-mentioned dual-parameter sensor is used as a dual-parameter sensor of contact direction and contact force, and is used for tactile perception when the balloon part contacts the pulmonary vein orifice and causes the central catheter to deform. As an elastic force-bearing structure, the central tube elastomer structure needs to produce a sensor elastomer 13 on the wall of the tubular central catheter. The sensor elastomer 13 is designed in size through an optimization method (response surface method, genetic algorithm, etc.), and can have a higher axial stiffness and a lower lateral stiffness, so that the structure can withstand a larger force when subjected to an axial force, and undergo obvious bending deformation when subjected to a lateral force. The laser is emitted from the multimode optical fiber 15 into the cavity at a certain divergence angle, and is reflected on the nano silver powder reflective layer 16, and then re-injected into the multimode optical fiber 15.

[0012] Preferably, in the above-mentioned dual-parameter sensor, the sensor elastic body 13 includes but is not limited to hollow structures such as parallel spiral beams, multi-layer continuous beams or hinges.

[0013] Preferably, in the above-mentioned dual-parameter sensor, the material of the central tube elastomeric structure is a photocurable resin, which has good mechanical properties and can effectively isolate the interference of ambient light sources on the optical fiber, which is beneficial to improving the anti-interference ability of the system and has good biocompatibility.

[0014] Preferably, in the above-mentioned dual-parameter sensor, the packaging material is made of a material with excellent biocompatibility.

[0015] Preferably, in the above-mentioned dual-parameter sensor, the packaging material is silicone rubber 14, which contains 5-10% by volume of titanium dioxide nanoparticles, so that it has good light isolation properties to improve the system's ability to resist ambient light interference. At the same time, its lower Young's modulus can ensure that the mechanical properties of the elastomer structure are mainly based on the elastic structure designed above.

[0016] Preferably, in the above-mentioned dual-parameter sensor, the multimode optical fiber is a large-core quartz multimode optical fiber, which not only has excellent flexibility but also has a larger numerical aperture, so that it can emit and receive more light energy. In addition, the low thermal expansion coefficient enables it to have good resistance to freezing temperature interference.

[0017] Preferably, in the above-mentioned dual-parameter sensor, the material of the nano silver powder reflective layer is a mixture of PDMS and nano silver powder in a mass ratio of 3:1, has high reflectivity, and can effectively reflect the laser emitted by the optical fiber back into the optical fiber. As the elastic body deforms, the distance between the nano silver powder reflective layer and the end face of the optical fiber will change, thereby being able to characterize the contact force exerted on the elastic body.

[0018] A balloon catheter contact direction and contact force evaluation device comprises the above-mentioned dual-parameter sensor 1, an optical power generation and data acquisition unit and a computer 25, wherein the optical power generation and data acquisition unit is composed of a fiber laser light source 22, a one-to-many beam splitter 21, a one-to-two beam splitter 18, a multimode optical fiber 15, a photodiode 23 and a signal acquisition board 24, wherein the dual-parameter sensor is connected to the output end of each of the one-to-two beam splitters 18 via the multimode optical fiber 15, one of the input ends of each of the one-to-two beam splitters 18 is respectively connected to one of the multiple output ends of the one-to-many beam splitter 21, and the other input end is respectively connected to the photodiode 23, wherein the photodiode 23 is connected to the computer 25 via the signal acquisition board 24, wherein the computer comprises a data processing unit and a navigation process contact force evaluation unit and an ablation process effective contact level evaluation unit, and the input end of the one-to-many beam splitter 21 is connected to the fiber laser light source 22.

[0019] In the above-mentioned balloon catheter contact direction and contact force evaluation device, when the laser of the fiber laser light source 22 is coupled to the input end of the one-to-many splitter 21, the laser signal will be evenly distributed to one input end of the multiple one-to-two splitters 18, and the other input end is connected to a photodiode to detect the change of optical power. The photodiode converts the optical power signal into an electrical signal and then uses the signal acquisition board 24 to collect data.

[0020] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, both ends of the optical fiber connector 19 are respectively connected to optical fiber joints 20, and the input end of the one-to-two splitter 18 is connected to the output end of the one-to-many splitter 21 through the optical fiber joint 20 and the optical fiber connector 19.

[0021] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, the data processing unit is composed of a contact direction evaluation algorithm based on an array-type optical fiber sensing structure, an elastic body structure nonlinear deformation and contact force evaluation algorithm based on a neural network model, and a cryoballoon ablation catheter three-dimensional reconstruction algorithm. After the data is collected by the signal acquisition board of the optical power generation and data acquisition unit, the algorithm is used on the computer side to perform data processing.

[0022] Preferably, the above-mentioned balloon catheter contact direction and contact force evaluation device, the navigation process contact force evaluation and ablation process effective contact level evaluation unit are jointly determined by the contact direction and contact force dual parameters, the contact force is solved through the data processed by the computer end, and the effective contact level is evaluated based on the contact force.

[0023] The above-mentioned balloon catheter contact direction and contact force evaluation device, the optical power generation and data acquisition unit is used to couple the laser emitted by the laser into the dual-parameter sensing unit, and collect the optical power signal of the dual-parameter sensing unit; the optical fiber laser light source can generate stable light intensity laser, can be directly connected to the optical fiber and couple the laser into the optical fiber. The data processing unit processes the multi-channel data collected by the optical power generation and data acquisition unit to realize the measurement of the contact direction and contact force under the nonlinear deformation of the elastomer, and performs three-dimensional reconstruction of the contact state, including a contact direction evaluation algorithm for an array optical fiber sensing structure, an elastic body structure nonlinear deformation and contact force evaluation algorithm based on a neural network model, and a cryoballoon ablation catheter three-dimensional reconstruction algorithm: the contact direction evaluation algorithm for the array optical fiber sensing structure aims to use the difference between the optical power changes of the array-arranged multimode optical fibers to determine the bending of the elastomer in three-dimensional space, so as to determine the contact direction between the balloon and the pulmonary vein orifice; the elastic body structure nonlinear deformation and contact force evaluation algorithm based on a neural network model aims to establish a strong nonlinear functional relationship between the elastic body structure deformation and the elastic body structure contact force; the cryoballoon ablation catheter three-dimensional reconstruction algorithm aims to reconstruct the three-dimensional model of the balloon and the central tube according to the measured nano-silver powder reflective layer posture, and infer the contact direction and contact force between the balloon and the pulmonary vein orifice according to the force and force direction exerted on the elastic body of the central tube, so as to realize the visualization of the contact state of the cryoballoon catheter. The navigation process contact force evaluation and ablation process effective contact level evaluation unit safely navigates the cryoballoon ablation catheter in the uninflated state from the femoral artery to the vicinity of the pulmonary vein orifice according to the contact force size given by the data processing unit. The contact force between the catheter end and the blood vessel wall during navigation provides a basis for the operator to apply a push or twist force to avoid damage to the blood vessel caused by excessive contact force during navigation, and realizes safe navigation of the catheter intervention process. In addition, it is also necessary to evaluate and divide the contact state according to the contact direction (catheter deflection angle) given by the data processing unit, the contact force of the central tube elastic body, and the contact force on the balloon surface, and classify the contact degree and coaxiality according to the tissue contact degree index comparison table, and use this index to assist in judging the contact degree and coaxiality between the cryoballoon and the tissue, so as to reduce the damage of fluoroscopic radiation and contrast agent, and improve the safety and effectiveness of the operation. The tissue contact degree index comparison table is determined by a series of experiments, and different coaxialities are divided by the catheter deflection angle, and it is determined whether the applied contact force is within the sufficient contact range under different angle ranges.

[0024] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, the optical fibers of the one-to-many beam splitter and the one-to-two beam splitter adopt the same type of multimode optical fibers as those in the above-mentioned dual-parameter sensor.

[0025] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, the contact direction evaluation algorithm of the array optical fiber sensing structure is specifically as follows: the distance d from the optical fiber end face of the dual-parameter sensing unit to the reflective surface of the nano silver powder i and the optical power variation ΔP i The linear proportional relationship is obtained by experimental calibration to fit the optical power-distance function d of each optical fiber arranged in an array. i =f(P i ), the change in optical power is used to measure the change in distance, according to the distance d from the end face of the optical fiber to the reflection surface of the nano silver powder i The least squares method is used to optimize the objective function to inversely calculate the three-dimensional pose of the reflection plane of the nanosilver powder, and the three-dimensional pose is projected into the plane coordinate system to characterize the contact direction.

[0026] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, the elastic body structure nonlinear deformation and contact force evaluation algorithm based on the neural network model is specifically: using a long short-term memory network (LSTM) to process the time series light intensity data of the optical fiber, the model is suitable for modeling the dynamic deformation and contact force changes of the elastic body structure at different time points. In the LSTM neural network model, the optical power P t As a time series input, it passes through the input gate i of the neural network t 、Forget gate t , output gate o t Update cell state G t And calculate the hidden state h t Extract data features and adjust the weight matrix W f With the bias term b f To accurately predict the contact force F t The size of the optical power P t With contact force F t This method can monitor and evaluate the stress state of the elastomer under different conditions in real time, providing accurate support for practical applications.

[0027] Preferably, in the above-mentioned balloon catheter contact direction and contact force evaluation device, the cryoballoon ablation catheter three-dimensional reconstruction algorithm is specifically as follows: combining the displacement field ε(x, y, z) of the elastic body to perform three-dimensional reconstruction of the deflection of the central tube, setting the balloon body as a shell unit, and using the inverse finite element method to infer the stress field distribution of the balloon body. Generally, the force exerted on the balloon body and the central tube elastic body is in a ratio of 3:1, and the specific value is related to the structure of the elastic body and the degree of deformation.

[0028] The evaluation method of the above-mentioned balloon catheter contact direction and contact force evaluation device comprises the following specific steps:

[0029] (1) The handle double-end interface 8 at the end of the operating handle 7 is connected to the signal excitation and acquisition system 11 and the catheter supporting system 12 respectively, and the dual-parameter sensor 1 is placed in the balloon ablation catheter and is in working state;

[0030] (2) During the navigation process, the balloon portion of the catheter is in an uninflated state. When the distal tip 3 of the catheter contacts the vascular tissue, the dual-parameter sensor 1 is deformed by force. The signal excitation and acquisition system 11 collects the optical power change caused by the deformation of the dual-parameter sensor 1. The time series light intensity data of the optical fiber transmission is processed by LSTM, and the optical power signal of each time step is used as input. The dynamic change of the contact force is calculated and extracted by using a neural network;

[0031] (3) During the ablation process, the catheter supporting system 12 inflates the balloon part of the catheter, the balloon of the catheter expands, and the balloon surface contacts the tissue of the pulmonary vein orifice. The signal excitation and acquisition system 11 collects the optical power change caused by the deformation of the dual-parameter sensor 1, establishes the optical power-distance function of the distance between the optical fiber end face and the nano-silver powder reflective surface, and combines the distances from different optical fiber end faces to the reflective layer to inversely calculate the three-dimensional position of the nano-silver powder reflective layer, thereby determining the contact direction;

[0032] (4) During the ablation process, the catheter posture is adjusted according to the contact direction determined in step (3), and the dual-parameter sensor 1 is deformed during the contact process. The time series light intensity data of the optical fiber transmission is processed by LSTM to obtain the force acting on the dual-parameter sensor 1. The deflection of the sensor elastomer 13 is reconstructed in three dimensions based on the displacement field, and the balloon body is set as a shell unit. The inverse finite element method is used to infer the stress field distribution on the balloon surface, and the force condition on the balloon surface is fed back to the operator in a visual form.

[0033] Technical Effects

[0034] The above-mentioned dual-parameter sensor is an optical fiber sensor based on light intensity modulation, which is only millimeter-level and can be integrated with a cryoballoon catheter. The elastic structure of its sensing part makes the central tube have a certain axial stiffness and lateral stiffness. During navigation or ablation, when the catheter tip or the balloon body is subjected to force, it will drive the central tube to deform axially and laterally, so that the central tube can sense the contact direction and contact force; at the same time, based on the array optical fiber sensing principle of light intensity modulation, the difference in optical power changes between different optical fibers when the sensor elastic body is deformed is used to judge the contact angle and triaxial contact force between the balloon and the pulmonary vein orifice. The multimode optical fiber is distributed at a certain angle interval in the inner wall at the bottom of the central tube elastic body. The top of the central tube elastic body is coated with a nano silver powder reflective film, which can diffusely reflect the light emitted by the optical fiber back into the optical fiber. After the elastic body is deformed, the reflection distance will change. The contact direction and contact force can be sensed according to the change in optical power in the optical fiber caused by the axial or lateral deformation of the central tube.

[0035] The balloon catheter contact direction and contact force evaluation device assembled by the dual-parameter sensor is an interventional cryoballoon balloon catheter contact direction and contact force evaluation device. Combined with the tissue contact index comparison table, the contact state between the cryoballoon catheter and the pulmonary vein orifice can be evaluated. The dual-parameter sensor used is based on the optical fiber measurement principle of the light intensity system. The distance from the optical fiber end face to the nano silver powder reflection surface is calculated according to the change in the optical power inside the optical fiber to measure the three-dimensional force on the central tube, and the difference in the optical power change between the array optical fibers is used to calculate the deflection angle and contact direction of the central tube. This principle has strong resistance to low-temperature environment disturbances, high sensitivity, good long-term stability and low manufacturing cost. The sensor elastomer can achieve high axial stiffness and low lateral stiffness mechanical structure design through structural parameter optimization. It has large axial force bearing capacity and large deflection angle bending ability, so that the contact force and contact direction can be measured using the optical fiber sensing method, so that the sensor has a large range and excellent resolution; the signal excitation and acquisition system uses a combination of multiple one-to-many splitters to evenly distribute the laser from the same laser to each array optical fiber, avoiding the interference noise and signal quality differences caused by laser differences. The combination of photodiodes and optical fibers for data acquisition can ensure the synchronization of multi-channel signal data, thereby improving the stability of the sensor.

[0036] The evaluation method combines the array fiber optical power signal with the LSTM neural network model to explore the temporal variation characteristics of the light intensity signal, accurately measure the nonlinear strain and force of the elastic body in real time, and perform three-dimensional reconstruction based on the strain and force of the elastic body. During the navigation process, the catheter push force and torque are adjusted accordingly according to the size and direction of the contact force to ensure that the catheter will not blindly pierce the blood vessel wall or the pulmonary vein orifice is insufficiently blocked during balloon ablation, ensuring the safety of the operation. During the ablation process, the inverse finite element method is used to measure the balloon stress field distribution according to the three-dimensional model, which is conducive to the visualization of the contact state between the cryoballoon ablation catheter and the pulmonary vein orifice, reducing the frequency of use of fluoroscopy equipment during the operation and thus reducing radiation damage. Combined with the tissue contact degree index comparison table, the contact state and coaxiality between the cryoballoon ablation catheter and the pulmonary vein orifice can be judged without the use of contrast agent, improving the sequelae of contrast agent in interventional surgery. In summary, the present invention realizes a high-precision dual-parameter sensing scheme with excellent resistance to the influence of freezing environment, miniaturization and high sensitivity design, high signal stability and high synchronization in the sensor structure design, and provides technical support for the contact direction and contact force evaluation between the cryoballoon ablation catheter and the pulmonary vein orifice without the use of contrast agents and fluoroscopy assistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1Schematic diagram of the dual-parameter sensing system for contact direction and contact force of the cryoballoon ablation catheter.

[0038] Figure 2 Schematic diagram of the structure and working principle of the dual-parameter sensor.

[0039] Figure 3 Schematic diagram of the signal excitation and acquisition system of the dual-parameter sensor.

[0040] Figure 4 Schematic diagram of sensor bending when the cryoballoon ablation catheter contacts the blood vessel wall.

[0041] Figure 5 Schematic diagram of sensor bending when the cryoballoon ablation catheter and the pulmonary vein orifice are in different contact postures.

[0042] Figure 6 This is a framework diagram of the contact force prediction model based on LSTM.

[0043] Figure 7 Figure 2 is a flowchart of the workflow for adjusting the catheter posture according to the sensor deflection angle during the alignment phase.

[0044] Figure 8 Schematic diagram of the workflow for assessing contact status based on sensor axial force during the ablation phase.

[0045] In the figure: 1- dual parameter sensor 2- fluid delivery catheter 3- distal tip 4- outer balloon

[0046] 5-Inner balloon 6-Catheter body 7-Operating handle 8-Handle double-end interface

[0047] 9- Fiber optic signal cable 10- Catheter supporting system cable 11- Signal excitation and acquisition system

[0048] 12-catheter supporting system 13-sensor elastomer 14-silicon rubber 15-multimode optical fiber

[0049] 16-Nano silver powder reflective layer 17-Instrument channel 18-One-to-two beam splitter

[0050] 19-Fiber Optic Connector 20-Fiber Optic Connector 21-One-to-Multiple Splitter

[0051] 22-Fiber laser light source 23-Photodiode 24-Signal acquisition board

[0052] 25-computer 26-bending state sensor 27-pulmonary vein 28-pulmonary vein tissue

[0053] 29-Alignment status sensor DETAILED DESCRIPTION

[0054] The device for evaluating contact direction and contact force of a balloon catheter according to the present invention will be described in detail below in conjunction with the embodiments and drawings.

[0055] Example 1

[0056] like Figure 2 As shown, a dual-parameter sensor includes a central tube elastic structure, a packaging material, a multimode optical fiber 15 and a nano silver powder reflective layer 16, wherein an instrument channel 17 is provided at the center of the central tube elastic structure for passing other auxiliary instruments, a cavity is provided between the instrument channel 17 and the outer wall of the central tube elastic structure, a sensor elastomer 13 with a hollow structure is provided on the surface of the cavity, a parallel spiral beam-shaped hollow structure is processed by precision processing technology, the design and optimization of the hollow structure make the overall structure of the elastomer have higher axial rigidity and lower lateral rigidity, so that it can have a certain force bearing capacity in the axial direction while being able to bend laterally, the hollow part is packaged and filled with silicone rubber 14 as a packaging material, the multimode optical fiber 15 is distributed at equal angles at the bottom of the central tube elastic structure, laser is injected into the aforementioned cavity from the multimode optical fiber, and the top of the cavity of the central tube elastic structure is plated with a nano silver powder reflective film as the nano silver powder reflective layer 16.

[0057] Specifically, the encapsulation material silicone rubber 14 used for the hollow part of the sensor elastomer 13 is prepared by mixing the prepolymer (taking polydimethylsiloxane as an example) and the curing agent (taking methyltriethoxysilane as an example) in a mass ratio of 35:1 (25-35:1 is acceptable) to form PDMS, and evenly mixing titanium dioxide nanoparticles with PDMS in a volume ratio of 5%-10%, and placing in a vacuum box to evacuate for 5 minutes to remove bubbles in the mixture to obtain silicone rubber 14, and then encapsulating the hollow part of the sensor elastomer 13 with the prepared silicone rubber 14. The low-rigidity silicone rubber 14 can encapsulate the sensor without affecting the deformation of the elastomer, so as to prevent the ambient light from affecting the optical fiber sensing performance, and to prevent the frozen liquid and the frozen gas from damaging the sensing structure inside the sensor. The nano silver powder reflective layer 16 is made by mixing PDMS and nano silver powder in a ratio of 3:1. After PDMS and nano silver powder are evenly stirred, they are placed in a vacuum box at room temperature to remove bubbles, and the liquid mixture is injected into the top of the sensor elastic body 13 using a syringe. The sensor is placed upside down on a vibration table and vibrated for 30 seconds. Then the inverted sensor is placed in a constant temperature heating box and heated at 60°C for 5 minutes to solidify the nano silver powder reflective layer 16 to form a high reflective surface. An array optical fiber is arranged at the bottom of the sensor elastic body 13 (the number and arrangement of optical fibers are determined according to requirements. This embodiment takes the arrangement of 4 multi-mode optical fibers at equal angles as an example). The laser is emitted from the multi-mode optical fiber 15 into the cavity at a certain divergence angle, and is reflected on the nano silver powder reflective layer 16, and then re-injected into the multi-mode optical fiber 15. The interference of the emitted light between the array optical fibers can be optimized by the number and arrangement of the optical fibers.

[0058] The light flux re-incident to the multimode optical fiber 15 is related to the deformation of the sensor elastic body 13. The larger the deformation of the sensor elastic body 13, that is, the smaller the distance from the end face of the multimode optical fiber 15 to the nano silver powder reflective layer 16, the larger the light flux re-incident to the multimode optical fiber 15. In addition, the optical fibers arranged in an array can reflect the three-dimensional posture of the plane where the nano silver powder reflective layer 16 is located in space through the difference in the amount of change of the light flux between the optical fibers. Therefore, the deformation and three-dimensional posture of the sensor elastic body 13 in space can be reflected by measuring the optical power data of the multimode optical fiber 15, and then the bending direction and the force received by the sensor elastic body 13 can be measured, and the contact force received by the balloon surface can be inversely calculated using the inverse finite element model according to the three-dimensional posture, deformation and force received by the sensor elastic body 13.

[0059] Assume that the distance between the end face of each optical fiber and the reflection plane is d i (i=1, 2, 3, 4), the normal vector of the nano silver powder reflective layer 16 in three-dimensional space is n, and a point on the plane of the nano silver powder reflective layer 16 is P, then according to the reflected light power change P of the multimode optical fiber 15 i , and the distance di Create a function model:

[0060] d i =f(P i )

[0061] The function model described in formula (1) can be determined by experimental calibration, so a set of (P i , d i ) data. Let x be the position of the optical fiber end face, then the plane determined by the nano silver powder reflective layer 16 can be described by equation (2), and the distance between the nano silver powder reflective layer 16 and the end face of the multimode optical fiber 15 can be described by equation (3):

[0062]

[0063] In order to accurately calculate the three-dimensional pose of the reflection plane, it is necessary to use the least squares method to optimize the objective function to estimate n and P:

[0064]

[0065] like Figure 3 As shown, the optical fiber laser light source 22 generates a laser with stable light intensity (5 mW power, 633 nm wavelength) and is injected into the input end of a one-to-two splitter 21 (the number of output ends of the one-to-two splitter is determined according to the number of array optical fibers, and the present invention is explained by taking four output ends as an example) and is evenly distributed to the four output ends. The four output ends of the one-to-two splitter 21 are connected to one of the input ends of the one-to-two splitter 18 through an optical fiber connector 20 and an optical fiber connector 19. In this way, the laser is injected into each multimode optical fiber 15 and transmitted to the dual-parameter sensor 1. The laser is emitted from the end face of the multimode optical fiber and reflected back to the multimode optical fiber 15 by the nano silver powder reflective layer 16, and finally emitted from the other input end of the one-to-two splitter 18, and the optical power signal is converted into an electrical signal by a photodiode 23, which is collected by a signal acquisition board 24 and processed by a computer 25.

[0066] The state of the cryoballoon ablation catheter tip when it contacts the blood vessel wall during navigation Figure 4 As shown. The uninflated cryoballoon ablation catheter tip 3 comes into contact with the blood vessel wall during the catheter navigation process. The contact force during the contact process acts on the ablation catheter tip 3, causing the sensor elastic body to deform. Based on this, the contact force calculation model can be combined to calculate the magnitude of the contact force between the ablation catheter tip 3 and the blood vessel wall during the navigation process. The operator can adjust the force of pushing or twisting the catheter according to the magnitude of the contact force to avoid excessive contact force from the ablation catheter tip 3 on the blood vessel wall, thereby causing blood vessel damage or puncture.

[0067] The bending of the sensor when the cryoballoon ablation catheter and the pulmonary vein orifice are in different contact postures. Figure 5 As shown. In the facing stage, the balloon of the cryoballoon catheter expands to the working pressure and begins to try to block the pulmonary vein 27. When the catheter and the pulmonary vein 27 are not in coaxial contact, the balloon with a certain stiffness first contacts the pulmonary vein tissue 28, thereby driving the sensor with lower stiffness to bend and deform. In this case, the contact direction (deflection angle) of the bending state sensor 26 can be measured by the sensor. In this case, it is necessary to adjust the coaxiality of the catheter and the pulmonary vein 27 by adjusting the position of the catheter body. When the position of the catheter is adjusted to the point where the difference in the optical power change of the array optical fiber is not large, it can be regarded as the facing state and enter the ablation stage. At this time, by solving the force and deformation amount of the alignment state sensor 29 and inverse finite element analysis, the contact between the outer balloon 4 and the pulmonary vein tissue 28 can be inversely calculated. By continuously squeezing the pulmonary vein opening, the contact force between the balloon of the cryoballoon catheter and the pulmonary vein tissue is maintained between 0.4 and 0.6N, which can be regarded as sufficient contact between the balloon and the pulmonary vein, good coaxiality, and complete blockage.

[0068] Example 2

[0069] like Figure 1As shown, a balloon catheter contact direction and contact force evaluation device includes the dual-parameter sensor 1 described in Example 1, an optical power generation and data acquisition unit and a computer 25, wherein the optical power generation and data acquisition unit is composed of a fiber laser light source 22, a one-to-many splitter 21, a one-to-two splitter 18, a multimode optical fiber 15, a photodiode 23 and a signal acquisition board 24, the dual-parameter sensor is connected to the output end of each of the one-to-two splitters 18 through the multimode optical fiber 15, and optical fiber connectors 20 are respectively connected to both ends of the optical fiber connector 19, one of the input ends of the one-to-two splitter 18 is connected to one of the multiple output ends of the one-to-many splitter 21 through the optical fiber connector 20 and the optical fiber connector 19, and the other input end is respectively connected to the photodiode 23. The photodiode 23 is connected to the computer 25 through the signal acquisition board 24. The computer includes a data processing unit and a navigation process contact force evaluation and ablation process effective contact level evaluation unit. The data processing unit is composed of a contact direction evaluation algorithm based on an array fiber optic sensing structure, an elastic structure nonlinear deformation and contact force evaluation algorithm based on a neural network model, and a cryoballoon ablation catheter three-dimensional reconstruction algorithm. After the data is collected by the signal acquisition board of the optical power generation and data acquisition unit, the algorithm is used to process the data on the computer side. The navigation process contact force evaluation and ablation process effective contact level evaluation unit are jointly determined by the contact direction and contact force dual parameters. The contact force is solved through the data processed by the computer side, and the effective contact level is evaluated based on the contact force. The input end of the one-to-many splitter 21 is connected to the fiber laser light source 22. When the laser of the fiber laser light source 22 is coupled to the input end of the one-to-many splitter 21, the laser signal will be evenly distributed to one input end of the multiple one-to-two splitters 18. The other input end is connected to a photodiode to detect changes in optical power. The photodiode converts the optical power signal into an electrical signal and then uses the signal acquisition board 24 to collect data.

[0070] During the application of the above-mentioned balloon catheter contact direction and contact force evaluation device, a contact direction and contact force dual-parameter sensor 1 is integrated on the central tube located inside the distal balloon of the cryoballoon catheter. The elastic structure of the sensor can achieve three-dimensional bending deformation through structural design and optimization. The higher axial stiffness and lower lateral stiffness of the elastic body are conducive to the sensor being easy to bend while bearing a certain range of axial forces. The fluid delivery catheter 2 in the balloon delivers the cryogenic fluid to the inner balloon 5. The cryogenic fluid absorbs heat from the inner balloon 5, the outer balloon 4 and other devices and evaporates. The evaporated gas returns to the pumping system from the interlayer between the inner balloon 5 and the outer balloon 4. The evaporation process causes the inner balloon 5, the outer balloon 4 and the distal tip 3 of the catheter to generate low temperatures, which can be used for point ablation or surface ablation. The delivery and evaporation of the cryogenic fluid causes the inner balloon 5 to expand to a certain pressure value. At this pressure value, the inner balloon has a certain rigidity. When the outer balloon 4 is subjected to a load, the balloon as a whole can drive the elastic body of the dual-parameter sensor 1 to deform. An array fiber optic sensor is installed at the bottom of the elastomer. The optical signal transmission section of the optical fiber is arranged in the catheter body 6. After passing through the operating handle 7 and the handle double-head interface 8, the optical fiber signal cable 9 is connected to the signal excitation and acquisition system 11 (the above-mentioned optical power generation and data acquisition unit and the computer 25 together constitute the signal excitation and acquisition system 11). The other working parts of the cryoballoon ablation catheter are connected to the catheter supporting system 12 (existing equipment, see the reservoir and fluid return reservoir in CN1 05339035A) through the catheter supporting system cable 10 after passing through the operating handle 7 and the handle double-head interface 8 to perform operations such as pumping liquid and returning liquid.

[0071] The evaluation device combines the optical power variation of the arrayed optical fiber with the neural network algorithm to evaluate the nonlinear deformation of the elastic body, and performs three-dimensional reconstruction of the cryoballoon catheter to achieve visualization of the cryoballoon catheter and the pulmonary vein orifice, and divides the effective contact level for different contact force ranges under different contact directions, thereby evaluating the coaxiality between the cryoballoon catheter and the pulmonary vein orifice. The specific steps for the evaluation are as follows:

[0072] (1) The handle double-end interface 8 at the end of the operating handle 7 is connected to the signal excitation and acquisition system 11 and the catheter supporting system 12 respectively, and the dual-parameter sensor 1 is placed in the balloon ablation catheter and is in working state;

[0073] (2) During the navigation process, the balloon portion of the catheter is in an uninflated state. When the distal tip 3 of the catheter contacts the vascular tissue, the dual-parameter sensor 1 is deformed by force. The signal excitation and acquisition system 11 collects the optical power change caused by the deformation of the dual-parameter sensor 1. The time series light intensity data of the optical fiber transmission is processed by LSTM, and the optical power signal of each time step is used as input. The dynamic change of the contact force is calculated and extracted by using a neural network;

[0074] (3) During the ablation process, the catheter supporting system 12 inflates the balloon part of the catheter, the balloon of the catheter expands, and the balloon surface contacts the tissue of the pulmonary vein orifice. The signal excitation and acquisition system 11 collects the optical power change caused by the deformation of the dual-parameter sensor 1, establishes the optical power-distance function of the distance between the optical fiber end face and the nano-silver powder reflective surface, and combines the distances from different optical fiber end faces to the reflective layer to inversely calculate the three-dimensional position of the nano-silver powder reflective layer, thereby determining the contact direction;

[0075] (4) During the ablation process, the catheter posture is adjusted according to the contact direction determined in step (3), and the dual-parameter sensor 1 is deformed during the contact process. The time series light intensity data of the optical fiber transmission is processed by LSTM to obtain the force acting on the dual-parameter sensor 1. The deflection of the sensor elastomer 13 is reconstructed in three dimensions based on the displacement field, and the balloon body is set as a shell unit. The inverse finite element method is used to infer the stress field distribution on the balloon surface, and the force condition on the balloon surface is fed back to the operator in a visual form.

[0076] Example 3

[0077] Contact force calculation algorithm of the balloon catheter contact direction and contact force evaluation device described in Example 2

[0078] Since the process of the cryoballoon ablation catheter contacting the pulmonary vein tissue is a dynamic and continuous nonlinear process, the deformation and stress state of the elastomer are affected by the historical load. Therefore, the use of LSTM is very suitable for solving the nonlinear force of the sensor elastomer 13. Figure 6 The framework diagram of the contact force prediction model based on LSTM is shown. In the laboratory environment, a high-precision force sensor is used to perform axial dynamic loading on the sensor, and the force sensor loading time series data F is recorded at the same time. t And the corresponding optical power voltage signal time series data P t Each dynamic loading is carried out for a long time in the range of 0.14-0.20N (corresponding to the contact force of 0.4-0.6N between the balloon and the pulmonary vein tissue) so that the LSTM model can obtain the mechanical characteristics of the elastic material such as creep effect and stress relaxation. t , F t ) The training set and the test set are divided into 7:3 ratios to train the LSTM model. t Normalize it and input it into the hidden layer of LSTM as the input layer. The hidden layer calculates the output value Y of LSTM cell according to the forward calculation method. t , the output value Y t After denormalization, the predicted force F is obtained t size, and calculate the output and loss, using the optimizer for the input gate it 、Forget gate t , output gate o t The equal weights are updated and the above calculation process is repeated until the loss function converges to generate the optimal LSTM contact force prediction model. Subsequently, the real-time array fiber optic light intensity time series data is input into the optimal LSTM contact force prediction model to obtain the force applied to the sensor elastic body 13.

[0079] A finite element model is established based on the geometric shape and material properties of the elastomer, and the strain field and stress field of the catheter center tube are constructed using the force magnitude and deformation amount of the sensor elastomer 13 calculated above as boundary conditions and applied to the model for inverse finite element model solution. The contact stress field between the outer balloon 4 of the cryoballoon catheter and the pulmonary vein tissue is back-calculated, and the contact state is evaluated based on this.

[0080] The specific steps are as follows:

[0081] Step 1: After the catheter is inserted into the blood vessel, it is slowly pushed forward. When the contact force is close to the safety threshold, the force of pushing the catheter is appropriately reduced and the change of the contact force is observed in real time: if the contact force continues to increase, the torque of the delivery catheter is slightly changed until the contact force is reduced, and then it is pushed further. When the contact force exceeds the safety threshold, the pushing is stopped immediately, and then the bending state of the catheter end is adjusted according to the direction of the contact force, so that it bends in the opposite direction of the contact force until the contact force is reduced to close to 0. The above operations are repeated until the catheter is safely delivered to the target position;

[0082] Step 2: Push the cryoballoon catheter to the vicinity of the pulmonary vein orifice, deliver cryofluid into the balloon to inflate it to a certain pressure value, and then enter the alignment stage;

[0083] Step 3: If Figure 7 As shown in the figure, in the alignment stage, if the cryoballoon is in non-coaxial contact with the pulmonary vein, the balloon will preferentially contact the pulmonary vein tissue, causing the sensor segment to bend, resulting in differences in the change value of the array fiber optic light intensity. After the deflection angle is calculated by the solution model, if the deflection angle is less than 5°, it can be considered that the coaxiality is good and the ablation stage can be entered. Otherwise, it is necessary to control the operating handle to adjust the ablation balloon posture and re-evaluate the coaxiality until the coaxiality is good.

[0084] Step 4: If Figure 8As shown, during the ablation stage, the cryoballoon catheter is pushed to make axial contact with the pulmonary vein tissue. The computer uses the LSTM algorithm to calculate the axial force of the sensor based on the light intensity voltage information of the array optical fiber, and inversely calculates the contact force between the balloon surface and the pulmonary vein tissue through the inverse finite element model. If the calculated contact force is within the range of 0.4 to 0.6N, it can be considered that good contact is achieved. Under this contact force range, the pulmonary vein occlusion effect is the best and the ablation force is the best. The operator needs to maintain this contact force until the end of the ablation operation, otherwise it is necessary to control the operating handle to apply appropriate pressure;

[0085] Step 5: The operator determines the degree of tissue contact based on the indicators described in Table 1 and evaluates the effectiveness of the surgery.

[0086] Table 1 Comparison table of indicators used to determine the degree of tissue contact

[0087]

[0088]

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual parameter sensor, characterized in that: It comprises a central tube elastomer structure, packaging material, multimode optical fiber and a nano silver powder reflective layer, wherein an instrument channel is provided at the center of the central tube elastomer structure, a cavity is provided between the instrument channel and the outer wall of the central tube elastomer structure, a sensor elastomer with a hollow structure is provided on the surface of the cavity, and the hollow part is packaged and filled with packaging material, the multimode optical fiber is distributed at equal angles at the bottom of the central tube elastomer structure, and a nano silver powder reflective film is plated on the top of the cavity of the central tube elastomer structure as a nano silver powder reflective layer.

2. The dual parameter sensor according to claim 1, characterized in that: The material of the central tube elastomer structure is light-curing resin; the packaging material is silicone rubber, which contains 5-10% by volume of titanium dioxide nanoparticles; the multimode optical fiber is a large-core quartz multimode optical fiber; the material of the nano-silver powder reflective layer is a mixture of PDMS and nano-silver powder in a mass ratio of 3:

1.

3. A balloon catheter contact direction and contact force evaluation device, characterized in that: It comprises the dual-parameter sensor as claimed in claim 1 or 2, an optical power generation and data acquisition unit and a computer, wherein the optical power generation and data acquisition unit is composed of a fiber laser light source, a one-to-many splitter, a one-to-two splitter, a multimode optical fiber, a photodiode and a signal acquisition board, wherein the dual-parameter sensor is connected to the output end of each of the one-to-two splitters through a multimode optical fiber, one of the input ends of each of the one-to-two splitters is respectively connected to one of the multiple output ends of the one-to-many splitter, and the other input end is respectively connected to a photodiode, wherein the photodiode is connected to the computer through a signal acquisition board, wherein the computer comprises a data processing unit and a navigation process contact force evaluation unit and a ablation process effective contact level evaluation unit, and the input end of the one-to-many splitter is connected to the fiber laser light source.

4. The device for evaluating contact direction and contact force of a balloon catheter according to claim 3, characterized in that: Both ends of the optical fiber connector are connected with optical fiber joints respectively, and the input end of the one-to-two optical splitter is connected with the output end of the one-to-many optical splitter through the optical fiber joint and the optical fiber connector.

5. The balloon catheter contact direction and contact force evaluation device according to claim 3, characterized in that: The data processing unit is composed of a contact direction evaluation algorithm based on an array optical fiber sensing structure, an elastic body structure nonlinear deformation and contact force evaluation algorithm based on a neural network model, and a cryoballoon ablation catheter three-dimensional reconstruction algorithm. After the data is collected by a signal acquisition board of the optical power generation and data acquisition unit, the algorithm is used on the computer side for data processing; The contact force evaluation unit during navigation and the effective contact level evaluation unit during ablation are jointly determined by the contact direction and contact force parameters. The contact force is solved through the data processed by the computer end, and the effective contact level evaluation is performed based on the contact force.

6. The balloon catheter contact direction and contact force evaluation device according to claim 3, characterized in that: The optical fibers of the one-to-many optical splitter and the one-to-two optical splitter adopt the same type of multimode optical fibers as those in the dual-parameter sensor.

7. The balloon catheter contact direction and contact force evaluation device according to claim 5, characterized in that: The contact direction evaluation algorithm of the array optical fiber sensing structure is specifically as follows: the distance d from the optical fiber end face of the dual-parameter sensing unit to the reflective surface of the nano silver powder i and the optical power variation ΔP i The linear proportional relationship is obtained by experimental calibration to fit the optical power-distance function d of each optical fiber arranged in an array. i =f(P i ), the change in optical power is used to measure the change in distance, according to the distance d from the end face of the optical fiber to the reflection surface of the nano silver powder i The least squares method is used to optimize the objective function to inversely calculate the three-dimensional pose of the reflection plane of the nanosilver powder, and the three-dimensional pose is projected into the plane coordinate system to characterize the contact direction.

8. The balloon catheter contact direction and contact force evaluation device according to claim 5, characterized in that: The nonlinear deformation and contact force evaluation algorithm of the elastic body structure based on the neural network model is specifically as follows: the time series light intensity data of the optical fiber is processed by using the long short-term memory network LSTM. The model is suitable for modeling the dynamic deformation and contact force changes of the elastic body structure at different time points. In the LSTM neural network model, the optical power P t As a time series input, it passes through the input gate i of the neural network t 、Forget gate t , output gate o t Update cell status C t And calculate the hidden state h t Extract data features and adjust the weight matrix W f With the bias term b f To accurately predict the contact force F t The size of the optical power P t With contact force F t The non-linear relationship between them.

9. The balloon catheter contact direction and contact force evaluation device according to claim 5, characterized in that: The three-dimensional reconstruction algorithm of the cryoballoon ablation catheter is specifically as follows: the deflection of the central tube is three-dimensionally reconstructed in combination with the displacement field ε(x, y, z) of the elastic body, the balloon body is set as a shell unit, and the stress field distribution of the balloon body is inferred using the inverse finite element method.

10. The evaluation method of the balloon catheter contact direction and contact force evaluation device according to any one of claims 3 to 9, characterized in that: The specific steps are as follows: (1) The handle double-end interface at the end of the operating handle is connected to the signal excitation and acquisition system and the catheter supporting system respectively, and the dual-parameter sensor is placed in the balloon ablation catheter and is in working state; (2) During navigation, the balloon part of the catheter is in an uninflated state. When the distal tip of the catheter contacts the vascular tissue, the dual-parameter sensor is deformed by force. The signal excitation and acquisition system collects the optical power change caused by the deformation of the dual-parameter sensor. The time series light intensity data of the optical fiber transmission is processed by LSTM, and the optical power signal of each time step is used as input. The dynamic change of the contact force is calculated and extracted using a neural network. (3) During the ablation process, the catheter supporting system inflates the balloon part of the catheter, the balloon of the catheter expands, and the balloon surface contacts the tissue of the pulmonary vein orifice. The signal excitation and acquisition system collects the optical power change caused by the deformation of the dual-parameter sensor, establishes the optical power-distance function of the distance between the optical fiber end face and the nano-silver powder reflective surface, and combines the distances from different optical fiber end faces to the reflective layer to inversely calculate the three-dimensional position of the nano-silver powder reflective layer, thereby determining the contact direction; (4) During the ablation process, the catheter posture is adjusted according to the contact direction determined in step (3), and the dual-parameter sensor is deformed during the contact process. The time series light intensity data of the optical fiber transmission is processed by LSTM to obtain the force acting on the dual-parameter sensor. The deflection of the sensor elastic body is reconstructed in three dimensions based on the displacement field, and the balloon body is set as a shell unit. The inverse finite element method is used to infer the stress field distribution on the balloon surface, and the force condition on the balloon surface is fed back to the operator in a visual form.

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