End-sensor and haptics feedback interventional catheter and its autonomous navigation method

Abstract

The present application relates to a kind of end sensor and tactile feedback type interventional catheter and its autonomous navigation method, the end sensor includes hemispherical light waveguide, compound eye array lens, multimode optical fiber and optical fiber image bundle, the front end of the optical fiber image bundle is equipped with compound eye array lens, the front of the compound eye array lens is equipped with hemispherical light waveguide, its bottom is placed four multimode optical fibers along circumference and certain incident angle is made into light waveguide, so that optical fiber end surface and light waveguide bottom surface coincide;The tactile feedback type interventional catheter is built-in the end sensor, based on the wide-angle imaging function provided by compound eye array lens and the force feedback function provided by light waveguide contact causes light leakage, can autonomously navigate and provide accurate force feedback and contact point position, need not guide wire as guiding device, can directly intervene blood vessel and in the intervention process, real-time feedback catheter and blood vessel wall contact mechanics information and position information, and change catheter intervention direction as required.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to an end sensor and tactile feedback type interventional catheter and an autonomous navigation method thereof. Background Art

[0002] In modern medicine, interventional procedures have become a primary treatment for major cardiovascular diseases. Traditional cardiovascular interventional procedures require physicians to deftly manipulate instruments such as catheters and guidewires with the assistance of fluoroscopic imaging devices such as CT scans. Catheters are essential for delivering interventional instruments to the lesion for further interventional treatment. However, current interventional catheters lack navigation capabilities, necessitating the use of guidewires as guiding devices to guide the catheter to the lesion. However, guidewires are typically composed of soft, slender structures, resulting in significant force transmission losses at the distal end. This deprives physicians of tactile information about the relationship between the interventional instrument and cardiovascular tissue, often leading to unexpected events such as vascular perforation and heart wall perforation. To avoid these issues, physicians typically use fluoroscopic imaging to observe the guidewire's position and shape to prevent excessive contact force between the guidewire and the vessel wall. However, the ionizing radiation generated during fluoroscopic imaging can pose a risk of radiation exposure to both physicians and patients. Therefore, physicians minimize the use of fluoroscopic imaging during interventional procedures, relying instead on surgical experience to blindly navigate interventional instruments. This practice significantly increases the likelihood of vascular injury or perforation.

[0003] At present, the following two methods are mainly used to avoid ionizing radiation exposure to doctors and patients during interventional surgery and ensure the safety of the surgery:

[0004] One approach is to use ionizing-free magnetic resonance imaging (MRI) equipment to navigate interventional devices. While this approach can avoid radiation risks, it carries a high risk because most current interventional devices and their associated equipment contain metal materials, and some patients have a history of treatment with metal implants such as vascular stents. This, in turn, limits the method's practical application.

[0005] Another method is to embed shape and force sensors at the front end of the interventional device to track the shape of the interventional device during navigation. Although this method can avoid perforation events caused by excessive operating force during blind navigation, it cannot ensure that the interventional device is always in the correct path during blind navigation. In addition, the design of the front-end force sensor may cause the guidewire to be unable to achieve the required plastic deformation in complex blood vessels, thereby greatly limiting its ability to pass through narrow or tortuous blood vessels. Therefore, although the integration of force sensors helps to reduce the risk of perforation, in actual operation, it may face the problem of the guidewire being unable to adapt to complex vascular paths, limiting its actual application effect. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an end sensor.

[0007] Another technical problem to be solved by the present invention is to provide a tactile feedback interventional catheter including the above-mentioned end sensor.

[0008] Another technical problem to be solved by the present invention is to provide an autonomous navigation method for the above-mentioned tactile feedback interventional catheter.

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

[0010] A tip sensor includes a hemispherical optical waveguide 4, a compound-eye array lens 5, a multimode optical fiber 6 (used as an optical fiber tendon) and an optical fiber imaging bundle 7. The front end of the optical fiber imaging bundle 7 is provided with a compound-eye array lens 5, and the front of the compound-eye array lens is provided with a hemispherical optical waveguide 4. Four multimode optical fibers 6 are placed circumferentially at the bottom of the hemispherical optical waveguide and couple light into the optical waveguide at a certain incident angle so that the end face of the optical fiber coincides with the bottom surface of the optical waveguide.

[0011] The fiber-optic imaging bundle is combined with a pre-placed compound-eye array lens device and its optical system to achieve contact state imaging and image transmission. The compound-eye array lens is designed and optimized using ray tracing software and printed using micro-nano manufacturing technology.

[0012] Preferably, in the above-mentioned end sensor, the four multimode optical fibers are arranged in a cross shape.

[0013] Preferably, in the above-mentioned end sensor, the optical waveguide is a PMMA optical waveguide.

[0014] Preferably, in the above-mentioned end sensor, the multimode optical fiber is a multimode optical fiber whose outer circumference (the entire circumference, except for the two end faces for light input and light output) is coated with polyimide.

[0015] Preferably, in the above-mentioned end sensor, the optical fiber imaging bundle is made of quartz glass.

[0016] Preferably, the above-mentioned end sensor is based on large sensing angle tactile feedback, and its dynamic contact force calibration and characterization method starts from the contact force and establishes a theoretical model of visual image and dynamic and static contact force based on light spot pattern analysis. The contact force between the catheter and the blood vessel wall during the intervention process is calculated through this model.

[0017] Preferably, the theoretical model of the static contact force of the above-mentioned end sensor is to calibrate the three-axis contact force of the cardiovascular visual-tactile navigation sensor using a static force calibration device, and to evaluate the isotropy of its force measurement using a sensitivity matrix.

[0018] Preferably, the theoretical model of the dynamic contact force of the above-mentioned end sensor is that the refractive index distribution of the materials on both sides of the optical waveguide in the non-contact state constitutes a total reflection condition, while the change in the refractive index distribution of the contact part in the contact state destroys the total reflection condition in the area, thereby forming light energy leakage in the contact area; during the dynamic contact process, the contact area of ​​the optical waveguide at the end of the catheter will undergo local deformation, thereby generating bending loss of part of the optical waveguide, causing the contact light spot area to present a non-uniform light intensity distribution, and quantitatively characterizing the lost light energy of this part.

[0019] Preferably, the above-mentioned end sensor adopts a leakage light energy-contact force conversion model. When the end sensor contacts the blood vessel wall, the optical waveguide on the surface is deformed, causing the light inside the optical waveguide to leak. The leaked light is captured by the compound eye array lens in the center and forms a light spot pattern at the end face of the optical fiber imaging bundle. The magnitude and direction of the contact force are obtained by analyzing the light spot pattern.

[0020] A tactile feedback interventional catheter comprises a catheter body, the catheter body having the above-mentioned end sensor built therein, the compound eye array lens of the end sensor being placed at the end of the catheter body, the compound eye array lens being connected to the optical fiber imaging bundle of the end sensor being arranged at the center of the inner cavity of the catheter body, the compound eye array lens being combined with the hemispherical optical waveguide of the end sensor, the hemispherical optical waveguide being fixedly connected to the end of the catheter body for encapsulating the compound eye array lens 5, multimode optical fiber 6 and optical fiber imaging bundle 7 of the end sensor in the catheter body, an instrument channel 3 for inserting surgical instruments being provided at an eccentric position of the cross section of the catheter body, and a hole for specifically placing the surgical instrument channel being reserved at a corresponding position on the optical waveguide.

[0021] Preferably, in the above-mentioned tactile feedback interventional catheter, a section of the catheter body close to the hemispherical optical waveguide is made of a flexible base material, and a section away from the hemispherical optical waveguide is made of a rigid base material.

[0022] Preferably, in the above-mentioned tactile feedback interventional catheter, the length of the catheter body using the flexible base material segment does not exceed 30% of the total length of the catheter body.

[0023] Preferably, in the above-mentioned tactile feedback interventional catheter, the rigid base material is made of shape memory polymer or other polymers with good biocompatibility, and the flexible base material is made of polymer materials with good biocompatibility and better flexibility such as polytetrafluoroethylene, so as to achieve large curvature deformation of the catheter end. At the same time, due to the shape memory effect of the shape memory polymer, it can ensure that the catheter returns to its original shape after long-term storage, which is convenient for storage.

[0024] Preferably, in the above-mentioned tactile feedback interventional catheter, the shape memory polymer is a polyurethane (PU)-based shape memory polymer.

[0025] Preferably, in the above-mentioned tactile feedback interventional catheter, the hemispherical optical waveguide of the end sensor is located at the end of the catheter body and its inner diameter and outer diameter are consistent with those of the catheter body.

[0026] In the above-mentioned autonomous navigation method of the tactile feedback interventional catheter, when the catheter enters the blood vessel, the pushing mechanism pushes the catheter forward. If the catheter encounters a change in the curvature of the blood vessel during advancement, causing the end of the catheter to contact the blood vessel wall, and the contact force shows a significant increase (with a tendency to transition contact), the sensor will feed back the tiny force change to the PC end, and the PC end will output an instruction to the pushing mechanism to drive the optical fiber tendon in the catheter to make the end of the catheter make a corresponding bending action to reduce it to 0 or a safe contact force range. The navigation process repeatedly cycles the above process to complete the closed-loop control of autonomous navigation.

[0027] Technical Effects

[0028] The tip sensor described above is a structure for an autonomously navigated catheter based on tactile feedback with a large sensing angle. This tactile feedback-based interventional catheter, assembled from this tip sensor, can be used in cardiovascular interventional procedures, enabling precise navigation to and treatment of lesions directly through the catheter without the need for a guidewire.

[0029] The tactile feedback interventional catheter is based on the synergistic effect of the large-angle imaging function provided by the compound eye array lens and the force feedback function provided by light leakage caused by the contact of the optical waveguide. It can autonomously navigate and provide precise force feedback and contact point location. This catheter does not require a guidewire as a guiding device. It can directly intervene in the blood vessel and provide real-time feedback on the mechanical and positional information of the contact between the catheter and the blood vessel wall during the intervention process. When the doctor needs it, the four optical fiber tendons on the catheter wall can be driven to change the direction of the catheter intervention. It has extremely high safety, real-time performance, and high precision during the navigation process. The specific advantages are as follows:

[0030] (1) Quantitative observation of contact force under large sensing angles was achieved. By introducing a compound eye array lens device at the front end of the catheter, the field of view of the sensor was increased, and large sensing angle measurement and sensor miniaturization design were achieved. An optical waveguide was placed in front to achieve quantitative observation of contact force in cardiovascular visual and tactile catheters.

[0031] (2) A method for calibrating and characterizing dynamic and static contact forces based on large sensing angle tactile feedback was proposed. Based on the optimized design and calibration of the compound eye array lens, a leakage light energy-contact force conversion model was proposed by combining the contact mechanics theoretical model and the waveguide optics theoretical model. The dynamic calibration and characterization of the contact force was realized based on the dynamic force calibration method.

[0032] (3) An autonomous navigation method and its closed-loop control method based on the safe contact force range were designed. Different navigation strategies were proposed in combination with different navigation task characteristics, so that the sensor can adapt to the large curvature changes of the vascular pathway and enhance its adaptability and navigation safety.

[0033] (4) The designed autonomous navigation catheter based on large sensing angle feedback can help doctors and patients avoid the effects of ionizing radiation. While achieving navigation, it can directly intervene with instruments for treatment, ensuring safety while improving the efficiency of surgery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall appearance structure of the tactile feedback interventional catheter of the present invention.

[0035] Figure 2 It is an enlarged schematic diagram of the structure of the end sensor described in the present invention.

[0036] Figure 3 It is a schematic diagram of the cross-sectional structure of the end sensor of the present invention.

[0037] Figure 4 It is a schematic diagram of the sensing principle of the sensor in the tactile feedback interventional catheter of the present invention.

[0038] Figure 5 It is a schematic diagram showing that the interventional blood vessel of the present invention does not contact the blood vessel wall.

[0039] Figure 6 It is a schematic diagram of the bending control after the interventional blood vessel contacts the blood vessel wall according to the present invention.

[0040] Figure 7 Schematic diagram of the navigation control mechanism of the tactile feedback interventional catheter of the present invention.

[0041] In the figure: 1- Rigid base material segment 2- Flexible base material segment 3- Instrument channel 4- Optical waveguide

[0042] 5- Compound eye array lens 6- Multimode optical fiber 7- Optical fiber image bundle 8- Catheter pushing mechanism

[0043] 9-Inner wall of blood vessel 10-Outer wall of blood vessel 11-Blood DETAILED DESCRIPTION

[0044] The tactile feedback interventional catheter device of the present invention is described in detail below with reference to the embodiments and drawings.

[0045] Example 1

[0046] like Figure 2 、 Figure 3As shown, the tip sensor comprises a hemispherical optical waveguide 4, a compound-eye array lens 5, a multimode optical fiber 6 (serving as an optical fiber tendon), and an optical fiber imaging bundle 7. The optical waveguide is a PMMA optical waveguide, manufactured using soft lithography due to its large size. The multimode optical fiber is a multimode optical fiber coated with polyimide on its outer periphery. The optical fiber imaging bundle is made of quartz glass, which offers excellent light transmittance, a wide wavelength range, and high resolution. The front end of the optical fiber imaging bundle 7 is equipped with a compound-eye array lens 5, which is used to transmit speckle images, enabling contact state imaging and image transmission. The compound-eye array lens was designed and optimized using ray tracing software and printed using femtosecond laser processing micro-nanofabrication technology. A hemispherical optical waveguide 4 is positioned in front of the compound-eye array lens. Four multimode optical fibers 6 are placed circumferentially at its bottom. These four multimode optical fibers are arranged in a cross pattern. The multimode optical fibers couple light into the optical waveguide at a specific angle of incidence, causing the fiber end faces to coincide with the bottom surface of the optical waveguide.

[0047] The above-mentioned tip sensor is based on large sensing angle tactile feedback. Its dynamic contact force calibration and characterization method starts from the contact force and establishes a theoretical model of visual image and dynamic and static contact force based on spot pattern analysis. Through this model, the contact force between the catheter and the blood vessel wall during the intervention process is calculated. While achieving integrated visual and tactile measurement, interventional treatment can be directly performed, greatly improving the efficiency of the operation.

[0048] The theoretical model of static contact force is to calibrate the three-axis contact force of the cardiovascular visual-tactile navigation sensor using a static force calibration device, and evaluate the isotropy of its force measurement using the sensitivity matrix.

[0049] The theoretical model of dynamic contact force is that the refractive index distribution of the materials on both sides of the optical waveguide in the non-contact state constitutes the total reflection condition, while the change in the refractive index distribution of the contact part in the contact state destroys the total reflection condition in this area, resulting in light energy leakage in the contact area; during the dynamic contact process, the contact area of ​​the optical waveguide at the end of the catheter will undergo local deformation, resulting in bending loss of part of the optical waveguide, making the contact spot area present a non-uniform light intensity distribution, and the loss of light energy in this part is quantitatively characterized.

[0050] Using the leakage light energy-contact force conversion model, when the end sensor contacts the blood vessel wall, the optical waveguide on the surface deforms, causing light inside the optical waveguide to leak. The leaked light is captured by the central compound eye array lens and forms a light spot pattern at the end face of the optical fiber image bundle. The magnitude and direction of the contact force can be obtained by analyzing the light spot pattern.

[0051] The dynamic and static contact force calibration and characterization of the above-mentioned tip sensor are as follows:

[0052] The optical waveguide at the catheter tip is designed to be hemispherical. Since the curvature radius of cardiovascular tissue is much larger than that of the catheter tip, and the rigidity of the catheter tip is much greater than that of cardiovascular tissue, the contact model can be assumed to be the contact between a flexible plane and a rigid hemispherical shape. Based on the contact mechanics theory, the contact indentation morphology during the contact process is described as follows:

[0053]

[0054] Where h is the contact indentation shape, V is the Poisson's ratio of biological soft tissue, E is the elastic modulus of biological soft tissue, and R t is the outer diameter of the optical waveguide, x is the lateral displacement value, and P is the positive pressure F N The normal pressure generated. k1, k2, η1 are the spring coefficient and viscosity coefficient respectively, which are obtained by fitting through relaxation and creep experiments. ε0 is the initial strain, Δγ is the adhesion energy (the work done by the contact body from the equilibrium position to infinity), G is the shear modulus, F T is the shear force, the pull-off force F o =-3πΔγR t / 2, s is the distance from the point to the shear force, r is the distance from the shear force to the center of the probe contact surface, θ is the angle between the shear force and the x-axis, and a is the contact radius.

[0055] In the non-contact state, the refractive index distribution of the materials on both sides of the optical waveguide constitutes a total reflection condition. However, in the contact state, the change in the refractive index distribution of the contact part destroys the total reflection condition in this area, resulting in light energy leakage in the contact area. The contact area between the catheter tip and cardiovascular tissue can be quantitatively described using Equation (1), and the functional mapping relationship between the leakage light energy area s1 and the contact area s2 is described using Equation (2):

[0056]

[0057] Where s1 is the spot area, s2 is the contact area, n1 is the refractive index of the waveguide substrate, n2 is the refractive index of the waveguide core, n3 is the refractive index of the contact object, d is the thickness of the waveguide, c is the speed of light in vacuum, and f′(s) is the fitting curve of the contact area and the spot area, which is obtained through calibration experiments.

[0058] During the dynamic contact process, the contact area of ​​the optical waveguide at the catheter end will undergo local deformation, resulting in bending loss of part of the optical waveguide, making the contact spot area present a non-uniform light intensity distribution. The overflow loss light energy is quantitatively characterized by formula (3):

[0059]

[0060] Where, β is the propagation constant, k0 is the wave number of light in vacuum, P1 is the light power increment of the pixel in the light sensing area of the image sensor, P2 is the light power increment of the unit in the contact area, g'(P2) is the fitting curve of the light power increment of the pixel and the light power increment of the unit, and is obtained through a calibration experiment.

[0061] Based on the above light-force conversion model theory, the light energy leakage distribution map of the catheter tip in the contact process with the cardiovascular tissue in a large field of view angle range can be obtained based on the compound eye array device. The light energy spatial distribution gradient in the light energy leakage distribution map contains the contact force distribution information in the x-axis and y-axis directions, and the contact force distribution information in the z-axis direction is contained by comparing the light energy space-time distribution gradient in the z-axis direction. The gradients of the light intensity in the three directions of the light energy leakage distribution map are obtained by image processing technology. According to formula (4), the three-axis contact forces of the cardiovascular tactile navigation sensor are calibrated by using a static force calibration device, and the isotropy of the force measurement is evaluated by using the sensitivity matrix.

[0062]

[0063] A static force calibration device is used to apply a force to the sensor in the range of 0-2N with a step of 0.05N, and the sensitivity matrix of formula (4) is obtained. The 0-2N sensing range can ensure that the sensor realizes a large range of tactile feedback in the blood vessel, and at the same time can ensure that the catheter is not damaged when it is inserted into the sheath. When the contact force is subsequently calculated, only the inverse matrix of the sensitivity matrix needs to be calculated and multiplied by the contact force distribution information in the light energy leakage distribution map to calculate the actual contact force between the optical waveguide and the blood vessel wall.

[0064] The frequency response method is used to overcome the influence of the blood flow environment on the contact between the catheter and the blood vessel wall. A sinusoidal force is used as an input signal, and the dynamic sensitivity and other parameters of the sensor are analyzed according to the output frequency response function of the tactile navigation sensor according to formula (5).

[0065]

[0066] In the formula, G(jω) is the dynamic sensitivity, e j∠G(jω) is the phase frequency characteristic and the output hysteresis of the sensor in the steady state.

[0067] In the above dynamic contact force calibration and characterization method of the navigation catheter end sensor, a visual image and dynamic and static contact force theoretical model is established based on the analysis of the contact force and the light spot map, which can accurately calculate the contact force between the catheter and the blood vessel wall in the intervention process.

[0068] Example 2

[0069] As Figure 1-4As shown, the tactile feedback interventional catheter includes a catheter body, which has the end sensor described in Example 1 built in the catheter body, and the compound eye array lens 5 of the end sensor is placed at the end of the catheter body. The compound eye array lens 5 is connected to the optical fiber imaging bundle 7 of the end sensor and is arranged at the center of the inner cavity of the catheter body. At the same time, the compound eye array lens 5 is combined with the hemispherical optical waveguide 4 of the end sensor. The hemispherical optical waveguide 4 is located at the end of the catheter body and its inner diameter and outer diameter are consistent with those of the catheter body. The hemispherical optical waveguide 4 is fixedly connected to the end of the catheter body to encapsulate the compound eye array lens 5, multimode optical fiber 6 and optical fiber imaging bundle 7 of the end sensor in the catheter body. An instrument channel 3 for inserting surgical instruments is provided at an eccentric position of the cross section of the catheter body, and a hole for specifically placing the surgical instrument channel is left at a corresponding position on the optical waveguide. The section of the catheter body close to the hemispherical optical waveguide uses a flexible base material, and the section away from the hemispherical optical waveguide uses a rigid base material. The length of the catheter body using the flexible base material section 2 does not exceed 30% of the total length of the catheter body, and the rest is the rigid base material section 1. The rigid base material section 1 uses a polyurethane (PU)-based shape memory polymer as a base to ensure that the force applied to the forward movement of the catheter can be effectively transmitted and the catheter will not undergo large deformation to affect the intervention; the flexible base material section 2 uses polytetrafluoroethylene as a base to achieve large curvature deformation of the catheter end and ensure that the catheter end can be well controlled to bend by the four optical fiber tendons when encountering complex vascular conditions. At the same time, due to the shape memory effect of the shape memory polymer, it can be ensured that the catheter can return to its original shape after long-term storage, which is convenient for storage.

[0070] In this embodiment, the inner diameter of the catheter body is designed to be 2mm, and the outer diameter is designed to be 2.2mm. This diameter is suitable for most interventional surgeries, such as cardiovascular interventional surgeries. The compound eye array lens connected to the optical fiber image transmission bundle is placed in the center of the catheter, and its diameter is designed to be 0.6mm, which can transmit optical signals well; the surgical instrument channel is placed in an eccentric position, and its diameter is designed to be 0.8mm, which can accommodate interventional treatments with instruments of different diameters. Four identical polyimide-coated multimode optical fibers are evenly placed on the inner wall of the catheter, and their diameter is about 0.2mm. The multimode optical fibers used have good bending resistance, mechanical strength and corrosion resistance. They mainly have the following two functions: one is to illuminate the hemispherical PMMA optical waveguide at the end of the catheter. The four evenly distributed multimode optical fibers can ensure that the light intensity is sufficient and evenly distributed when illuminating the optical waveguide; the other is that due to its good bending resistance and mechanical strength, it can act as an optical fiber tendon. When encountering complex vascular conditions, the optical fiber tendon is driven to adjust the bending of the flexible part of the catheter, ensuring safety while further intervening in the blood vessel.

[0071] One end of the tactile feedback interventional catheter is connected to a catheter pushing mechanism 8, which consists of a linear drive module and a torsional drive module (An Enhanced Dual-finger Robotic Hand for Catheter Manipulating in Vascular Intervention: A Preliminary Study*, Proceeding of the IEEE International Conference on Information and Automation Yinchuan, China, August 2013). The linear drive module uses a 24V DC motor with a rated power of 70W. This motor has two steel wheels and a regulator. The knob on the regulator can adjust the diameter of the pushing catheter and the opening and closing of the mechanism. The motor drive module uses an H-bridge L298 logic driver, which can drive two DC motors simultaneously, with a single-channel power output of 7A and built-in isolation and undervoltage protection. The STM32F103C8T6 microcontroller used for linear drive control is a 32-bit microcontroller based on the Cortex-M3 core. Its internal 8MHz HSI clock can be multiplied up to 64MHz, and its external 8MHz HSE clock can be multiplied up to 72MHz. It also features up to four built-in timers, each with different modes and frequency counts. Furthermore, the microcontroller's low-power design is ideally suited to the motor, minimizing power consumption while maintaining high DC motor performance. The PWM code for motor speed control is written in C, with a set frequency of 310Hz and a duty cycle of 6% to 8%. The catheter twisting module consists of a stepper motor and two rollers, which rotate upward and downward to achieve catheter twisting. A 42mm linear screw stepper motor controls the vertical movement of one of the rollers. This stepper motor has a travel of 50mm, a lead of 2mm, a rated torque of 0.7N·m, and a length of 60mm. The motor driver uses the TB6600 driver. Its interface utilizes high-speed optocoupler isolation and offers strong resistance to high-frequency interference. It also features input voltage reverse polarity protection, as well as overheating, overcurrent, and short-circuit protection, offering excellent performance and safety. A 3-position DIP switch allows for seven levels of subdivision control (1, 2 / A, 2 / B, 4, 8, 16, and 32), and eight levels of current control (0.5A, 1A, 1.5A, 2A, 2.5A, 2.8A, 3.0A, and 3.5A). The driver's pulse signal accepts 3.3V, 5V, and 24V signals, eliminating the need for a series resistor. The power supply requires only 9-40V DC. The outer surface of the catheter is evenly coated with a hydrophilic coating, ensuring smooth insertion into complex vascular structures.

[0072] The optical fiber image transmission bundle is a collection of thin optical fibers that can transmit imaging information from the catheter tip to an imaging system at the other end, which can capture image information from the optical waveguide for detecting and analyzing light leakage. The hemispherical PMMA optical waveguide is located at the end of the catheter body and its inner diameter and outer diameter are consistent with the catheter, and the optical waveguide is in contact with the blood vessel wall through its surface, and when contact occurs, the light in the optical waveguide will leak at the contact point. The compound eye array lens at the catheter tip is directly connected to the optical fiber image transmission bundle, and the compound eye array lens is composed of multiple micro lenses, which is responsible for capturing the leaked light inside the optical waveguide, ensuring that the image transmission bundle can image the leaked light and transmit it to the external imaging system. The four multi-mode optical fibers on the inner wall of the catheter are arranged in a cross shape, not only as tendon control for the bending movement of the catheter end, but also responsible for providing light source for the optical waveguide. The multi-mode optical fiber can transmit different modes of light beams to produce uniform illumination inside the optical waveguide, facilitating the detection of light leakage. During the catheter intervention process, the four multi-mode optical fibers continuously light the hemispherical optical waveguide at the end of the catheter, and the light intensity and other parameters remain unchanged. Once the optical waveguide contacts the biological tissue and deforms, the optical waveguide will immediately leak light, and the leaked light will be captured by the compound eye array lens at the center of the catheter, which will present a light spot pattern at a certain height on the end face of the optical fiber image transmission bundle and be transmitted to the computer through the optical fiber image transmission bundle. Due to the bending of the catheter end sensor driven by the optical fiber tendon, the optical fiber image transmission bundle may also bend together, which may cause distortion of the transmitted light spot pattern, which needs to be repaired. The present application repairs the distorted image based on the ResNet (Residual Neural Network) model in the neural network. ResNet solves the problem of gradient disappearance caused by the increase of network layers by introducing residual blocks (Residual Blocks). It allows the input to directly jump (skip connections) when passing through multiple layers of convolution, allowing the model to better preserve the original image information and avoid information loss. First, determine the data set, the optical fiber bending angle from 0 degrees to 180 degrees, and each 1 degree of bending corresponds to a distorted sample, which provides relatively rich supervised learning data for the model, 80% of the samples are used for training, 10% for verification, and 10% for testing.The model then uses the distorted 224×224×1 light spot image as input. The first convolutional layer uses a 7×7 kernel with a stride of 2 and 64 output channels, followed by a batch normalization (BN) layer for stable training and a Rectified Linear Unit (ReLU) activation function. The maximum pooling layer uses a 3×3 kernel with a stride of 2 to downsample the input. Residual blocks 1-2 each contain two 3×3 convolutions with 64 output channels; residual blocks 3-4 each contain two 3×3 convolutions with 128 output channels; residual blocks 5-6 each contain two 3×3 convolutions with 256 output channels; and residual blocks 7-8 each contain two 3×3 convolutions with 512 output channels. A global average pooling layer reduces the convolution output to 1D, and the fully connected layer maps it to the restored light spot image. Next, two loss functions are combined to improve the restoration effect: mean square error (MSE) and structural similarity index (SS iM).

[0073] MSE is used to calculate the pixel difference between the restored image and the original image, which can be expressed as formula (10):

[0074]

[0075] SSIM is used to measure the perceptual similarity between the restored image and the original image, which can be expressed as formula (11):

[0076]

[0077] Where μ x 、μ y is the image mean, σ x , σ y is the image variance, σ xy is the covariance.

[0078] We used the Adam adaptive learning rate optimizer, with an initial learning rate of 0.001, ββ1 = 0.9, ββ2 = 0.999, a batch size of 16 to 32, and a training epoch number of 50 to 100. The learning rate was adjusted based on validation set performance, with the learning rate decayed by half after every 10 epochs. After all parameters were set, we trained the ResNet model using the training set data, monitoring the changes in the Mean Sequence (MSE) and SSIM on the validation set. We then evaluated the model performance on the test set, calculating the MSE, SSIM, and PSNR (Peak Signal-to-Noise Ratio, a measure of image restoration quality).

[0079] According to the repaired spot image output by the neural network, the established "light-force" conversion model is used to calculate the magnitude, direction and other information of the contact force.

[0080] The catheter navigation control mechanism of the above-mentioned haptic feedback interventional catheter is as follows:

[0081] Since the cardiovascular tissue is more fragile than the myocardial tissue, the feedback of the tiny dynamic contact force during the catheter navigation is very important for the safety of the operation, so the safe contact force range suitable for the blood vessel navigation is determined through a biological experiment. The designed biological experiment selects the cardiovascular tissue sample of a rat as the experimental object, accurately controls the catheter to exert a pressure in the range of 0-1N on the inner wall of the blood vessel sample by a force sensor with a step of 0.05N, evaluates the blood vessel damage under different contact forces through histological analysis, including intimal injury, inflammatory reaction, and endothelial cell peeling, etc., obtains the influence of different contact forces on the blood vessel tissue, and determines the safe contact force range without damaging the blood vessel wall. Before determining the specific control mechanism, the position of the light energy leakage of the optical waveguide, i.e., the specific position of the contact point between the blood vessel wall and the optical waveguide on the optical waveguide, needs to be determined. A three-dimensional Cartesian coordinate system (x, y, z) is established with the center of the end face of the image fiber bundle as the origin, the surface of the hemispherical optical waveguide is located at z=0, the outer diameter is R t , the position of the contact point on the surface of the optical waveguide is represented by P(x p , y p , z p ), and the following relationship is obtained:

[0082] x p 2 +y p 2 +z p 2 =R t 2 (6)

[0083] Since the optical waveguide is hemispherical, the contact point is on the upper part of the hemisphere, so z p ≥0. When the optical waveguide contacts the blood vessel wall and light leakage occurs, the direction of the leaked light can be represented by formula (7):

[0084]

[0085] In the formula, θ is the direction of the leaked light, θ p is the leakage angle of the light when the light enters the external air from the inside (core layer) of the optical waveguide, which is the included angle between the light and the normal line, is the azimuth angle of the light leakage, which is the rotation angle of the light in the horizontal direction relative to the xy plane, and can be represented by formula (8):

[0086]

[0087] where θ2 is the incident angle of light propagating in the waveguide core layer (relative to the normal), n2 is the refractive index of the waveguide core layer, and n0 is the refractive index of air. The propagation of light in the fly's eye array lens follows a simple ray tracing model, and a spot pattern is imaged at the end face z = h of the image fiber bundle. Let the center position of the spot in the spot pattern at the end face of the image fiber bundle be C(x c , y c , z c ), we can deduce the specific coordinates of the contact point P(x p , y p , z p ) as follows:

[0088]

[0089] To achieve autonomous navigation control, a closed-loop control mechanism of the interventional sensor based on micro contact force feedback is designed to precisely control the catheter. When the catheter enters the blood vessel, the pushing mechanism pushes the catheter forward. If the catheter encounters a change in the curvature of the blood vessel during the forward movement of the catheter, the catheter end contacts the blood vessel wall, and the contact force increases significantly (with a transition contact tendency), the sensor feeds back the change in the micro force to the PC end, and the PC end outputs instructions to the pushing mechanism to drive the optical fiber tendon in the catheter to make the catheter end make a corresponding bending action to reduce to 0 or a safe contact force range. The navigation process repeats the above process to complete the closed-loop control of autonomous navigation. The large deformation controllability of the catheter enables it to adapt to the large curvature change of the blood vessel passage, ensuring the safety and effectiveness of the autonomous navigation process.

[0090] Example 3

[0091] The application example of the tactile feedback type interventional catheter described in Example 2 is as follows:

[0092] As shown in Figure 5 , after the catheter is pushed into the blood vessel by the pushing mechanism, it only contacts the blood 11, but the force exerted by the blood 11 on the sensor is negligible compared to the contact force of the sensor with the inner wall 9 of the blood vessel. Here we only consider the contact force. Therefore, the catheter is in a non-contact state with the inner wall 9 of the blood vessel at the initial stage of intervention. At this time, because the curvature of the blood vessel does not change much, the catheter is unlikely to contact the inner wall 9 of the blood vessel, the optical waveguide does not leak light, and the catheter end does not need to be bent, and the pushing can continue.

[0093] As shown in Figure 6As shown, when encountering a blood vessel bifurcation or a large change in blood vessel curvature, the end of the catheter will contact the inner wall 9 of the blood vessel, and both the inner wall 9 and the outer wall 10 of the blood vessel will produce slight deformations. When the deformation of the outer wall 10 of the blood vessel is too large, the blood vessel will rupture. At this time, light leakage can be generated by the optical waveguide of the end sensor, and the spatial position of the contact point can be calculated according to the established model. Then, the corresponding optical fiber tendon is driven to make the catheter end bend in the opposite direction of the contact point. At this time, the catheter is away from the blood vessel wall or its contact force is in a safe contact range.

[0094] like Figure 7 As shown, since a guidewire is not required for pre-implanted navigation, the catheter can be inserted directly after the sheath is inserted. When the catheter is not in contact with the vessel wall, no light leakage occurs, and advancement can continue until the lesion is reached. Once the vessel contacts the vessel wall, light leakage occurs in the optical waveguide. The contact force and the specific location of the contact point are calculated using the spot pattern. A drive device then bends the catheter tip to a safe contact range. Once within this range, the catheter is further advanced, and its curvature and path information are recorded. The navigation progress is then calculated based on this recorded information. Sensors at the catheter tip further measure mechanical information. If the contact force is within the safe range, the catheter is further advanced. If the contact force exceeds the safe range, the fiber optic tendon is adjusted until the contact force is within the safe range. The catheter is then driven within the safe contact range until it reaches the navigation endpoint. During this period, if the contact force increases significantly but remains within the safe range, the multimode fiber is fine-tuned to optimize the contact force or avoid contact. This ensures safe advancement of the catheter against the vessel wall and allows for a clear derivation of the navigation path. When the catheter safely reaches the navigation endpoint, that is, the lesion, the required surgical instruments can be introduced through the instrument channel to directly perform treatment, which can greatly improve the efficiency of the operation while ensuring safety.

[0095] The drive control of multimode optical fiber (fiber optic tendon) can be done manually or automatically. Take PID autonomous control as an example: Since the vascular intervention process is a real-time dynamic process, a PID controller is used to control the drive of the fiber optic tendon through the PID algorithm. The PID controller can adjust the control output in real time according to the current error. The proportional part can quickly reduce the error, while the differential part can predict the error change, thereby speeding up the response speed of the system. It is suitable for dynamically changing systems. The specific coordinates of the contact point have been obtained from the previous derivation, and P = (x p ,y p , z p ) indicates that the tensions of tendon 1 (upper), tendon 2 (lower), tendon 3 (left), and tendon 4 (right) are T1, T2, T3, and T4 respectively, and the reference value is T0. The target position to which the optical fiber needs to be adjusted is expressed as: SP = (SP x , SPy , SP z ), then the error vector can be expressed as:

[0096] e(t)=SP-P=(SP x -x p , SP y -y p , SP z -z p ) (12)

[0097] Further according to the PID principle, the control signal of each dimension is obtained:

[0098]

[0099] Where K p is the proportional gain, K i is the differential gain, K d is the integral gain. Further discretizing the above formula, we can get the control signal of each dimension:

[0100]

[0101] Where Δt is the control period. Similarly, the digital control signals of the x, y, and z axes can be expressed as formula (13):

[0102]

[0103] Combined with the tendon tension, the tendon control logic can be obtained:

[0104] The sizes of T1 and T2 are given by u y [n] Control, from a top-down perspective, increasing the tension of the upper tendon T1 will cause the catheter to bend upward, and increasing the tension of the lower tendon T2 will cause the catheter to bend downward:

[0105]

[0106] Where K1 and K2 are proportional coefficients, and their specific values ​​are set according to actual conditions.

[0107] The sizes of T3 and T4 are determined by u x [n] Control, increasing the tension of the left tendon T3 will make the catheter bend to the left, increasing the tension of the right tendon T4 will make the catheter bend to the right:

[0108]

[0109] Where K3 and K4 are proportional coefficients, and their specific values ​​are set according to actual conditions.

[0110] After the driving catheter reaches the designated position, the required surgical instruments are inserted through the surgical instrument channel to achieve the goal of efficient and safe treatment.

[0111] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A tactile feedback interventional catheter, comprising a catheter body, a built-in end sensor in the catheter body, a compound-eye array lens of the end sensor disposed at the end of the catheter body, the compound-eye array lens connected to a fiber optic imaging bundle of the end sensor disposed at the center of the inner cavity of the catheter body, the compound-eye array lens being combined with a hemispherical optical waveguide of the end sensor, the hemispherical optical waveguide being fixedly connected to the end of the catheter body for encapsulating the compound-eye array lens of the end sensor, the multimode optical fiber, and the fiber optic imaging bundle within the catheter body, an instrument channel for inserting a surgical instrument being provided at an eccentric position of the catheter body cross section, and a hole for specifically placing the surgical instrument channel being reserved at a corresponding position on the optical waveguide, characterized in that: The end sensor includes a hemispherical optical waveguide, a compound eye array lens, a multimode optical fiber, and an optical fiber imaging bundle. The front end of the optical fiber imaging bundle is provided with a compound eye array lens, and the front of the compound eye array lens is provided with a hemispherical optical waveguide. Four multimode optical fibers are placed along the circumference of the bottom of the hemispherical optical waveguide and light is coupled into the optical waveguide at a certain incident angle so that the end face of the optical fiber coincides with the bottom surface of the optical waveguide. The section of the catheter body close to the hemispherical optical waveguide is made of a flexible base material, and the section away from the hemispherical optical waveguide is made of a rigid base material; The multimode optical fiber can act as an optical fiber tendon cord, and when encountering complex blood vessel conditions, the optical fiber tendon cord can be driven to adjust the bending condition of the flexible portion of the catheter; The autonomous navigation method of the tactile feedback interventional catheter is as follows: when the catheter enters the blood vessel, the pushing mechanism pushes the catheter forward. If the catheter encounters a change in blood vessel curvature during advancement, causing the end of the catheter to contact the blood vessel wall and the contact force to increase significantly, the sensor feeds back the small force change to the PC end. The PC end outputs an instruction to the pushing mechanism to drive the optical fiber tendon in the catheter to make the end of the catheter perform a corresponding bending action to reduce the contact force to 0 or a safe contact force range. The navigation process repeatedly cycles the above process to complete the closed-loop control of autonomous navigation.

2. The tactile feedback interventional catheter according to claim 1, characterized in that: The rigid base material is a shape memory polymer, and the flexible base material is polytetrafluoroethylene.

3. The tactile feedback interventional catheter according to claim 1, wherein: The four multimode optical fibers are arranged in a cross shape.

4. The tactile feedback interventional catheter according to claim 1, wherein: The optical waveguide is a PMMA optical waveguide; the multimode optical fiber is a multimode optical fiber with polyimide coated on the periphery; and the optical fiber image transmission bundle is made of quartz glass.

5. The tactile feedback interventional catheter according to claim 1, characterized in that: The end sensor is based on large sensing angle tactile feedback. Its dynamic contact force calibration and characterization method starts from the contact force and establishes a theoretical model of visual images and dynamic and static contact forces based on light spot pattern analysis. The contact force between the catheter and the blood vessel wall during the intervention process is calculated through this model.

6. The tactile feedback interventional catheter according to claim 5, characterized in that: The theoretical model of the static contact force of the end sensor is to calibrate the three-axis contact force of the cardiovascular visual-tactile navigation sensor using a static force calibration device, and to evaluate the isotropy of its force measurement using a sensitivity matrix; the theoretical model of the dynamic contact force is that the refractive index distribution of the materials on both sides of the optical waveguide in the non-contact state constitutes a total reflection condition, while the change in the refractive index distribution of the contact part in the contact state destroys the total reflection condition in the area, thereby forming light energy leakage in the contact area; during the dynamic contact process, the contact area of ​​the optical waveguide at the end of the catheter will undergo local deformation, thereby generating bending loss of part of the optical waveguide, causing the contact light spot area to present a non-uniform light intensity distribution, and quantitatively characterizing the lost light energy of this part.

7. The tactile feedback interventional catheter according to any one of claims 1 to 6, characterized in that: The end sensor adopts a leakage light energy-contact force conversion model. When the end sensor contacts the blood vessel wall, the optical waveguide on the surface is deformed, causing light inside the optical waveguide to leak. The leaked light is captured by the compound eye array lens in the center and forms a light spot pattern at the end face of the optical fiber transmission bundle. The magnitude and direction of the contact force are obtained by analyzing the light spot pattern.

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