Intelligent neurointervention catheter system based on ndfeb permanent magnetic guide and combined embolization method thereof

Abstract

The application provides an intelligent neural interventional catheter system based on NdFeB permanent magnetic guide and a combined embolization method thereof. The system comprises: a catheter with a magnetic control section at the front end, the magnetic control section comprising a plurality of magnetic units made of permanent magnetic material arranged in the axial direction, each magnetic unit having an independent magnetization direction and being connected through a flexible connecting piece; a medicine injection channel penetrating through the magnetic control section; an external magnetic field generating device generating an adjustable gradient magnetic field; and a control unit regulating the magnetic field parameters. The method drives the permanent magnetic control section to deflect through the external gradient magnetic field to realize multi-degree-of-freedom steering of the catheter in the tortuous blood vessels, and after reaching the position, the position is maintained stable through the magnetic field parameter adjustment and the embolic agent is directly injected through the integrated medicine injection channel. The application replaces mechanical pushing with non-contact magnetic field driving to reduce the risk of blood vessel damage, and reduces the reflux of embolic agent caused by catheter displacement through the integrated design of navigation and embolization.

Description

Technical Field

[0001] This application relates to the field of medical device technology, specifically to an intelligent neurointerventional catheter system based on NdFeB permanent magnet guidance and its combined embolization method. Background Technology

[0002] In interventional treatment of cerebral vascular malformations, microcatheters need to reach the lesion site and perform embolization via tortuous and small feeding arteries. In current technologies, catheter navigation mainly relies on mechanical guidewire propulsion. When facing the tortuous feeding arteries of cerebral arteriovenous malformations or dural arteriovenous fistulas, the catheter tip is prone to getting stuck or deviating from the path, and the rigid tip is prone to damaging the vessel wall.

[0003] Existing magnetically controlled catheters mostly use soft magnetic materials and require a high-intensity external magnetic field for operation. The devices are large and the operation is complex. In addition, navigation and embolization are separate procedures. After the catheter is in place, its position needs to be repeatedly adjusted to inject the embolic agent. Unstable catheter position can easily lead to reflux of the embolic agent into non-target vessels, increasing the risk of misembolization and prolonging the operation time. Summary of the Invention

[0004] To address the shortcomings of existing technologies, such as difficulties in navigating neurointerventional catheters in tortuous blood vessels, reliance on strong external magnetic fields for magnetically controlled catheters, and the instability of catheter position and embolization agent reflux caused by the separate operation of navigation and embolization, this application provides an intelligent neurointerventional catheter system based on NdFeB permanent magnet guidance and its combined embolization method. This system achieves precise multi-degree-of-freedom steering under weak magnetic fields by integrating multiple permanent magnet units with independent magnetization directions at the catheter tip and cooperating with an external adjustable gradient magnetic field. Simultaneously, the drug delivery channel runs through the magnetically controlled section, enabling integrated navigation and embolization operations. This reduces the need for external magnetic field strength while improving the catheter's positioning ability in tortuous blood vessels and reducing the risk of catheter displacement during embolization. Specifically, this application provides the following technical solutions: In a first aspect, this application provides an intelligent neurointerventional catheter system based on NdFeB permanent magnet guidance, comprising: The conduit has a magnetically controlled section at its front end, which includes multiple magnetic units arranged axially. Each magnetic unit is made of permanent magnet material and has an independent magnetization direction. The magnetic units are connected by flexible connectors to allow the magnetically controlled section to bend with multiple degrees of freedom. The catheter is provided with a drug injection channel, which passes through the magnetically controlled section and extends to the distal outlet of the catheter; An external magnetic field generator is used to generate an adjustable gradient magnetic field that acts on the magnetically controlled segment to drive the magnetically controlled segment to deflect and guide the catheter tip to change its direction of travel. The control unit, connected to the external magnetic field generator, is used to regulate the intensity and direction of the adjustable gradient magnetic field.

[0005] Optionally, the magnetic unit is a rare-earth permanent magnet, and the magnetization direction of each magnetic unit includes an alternating configuration of axial magnetization and radial magnetization to generate a composite deflection torque under the action of the adjustable gradient magnetic field.

[0006] Optionally, the flexible connector is a superelastic alloy skeleton, and the bending radius of the magnetostrictive segment under the drive of the adjustable gradient magnetic field is less than or equal to a preset bending threshold.

[0007] Optionally, the distal outlet of the injection channel is provided with a micro-orifice injection structure, which includes a plurality of micro-orifices distributed at the tip of the catheter for injecting the embolic agent into the target area in a dispersed manner.

[0008] Optionally, it also includes a pressure sensor disposed in the injection channel, and the control unit adjusts the injection speed of the embolic agent through the injection channel according to the detection value of the pressure sensor.

[0009] Optionally, the control unit plans the catheter travel path based on preoperative vascular imaging data and adjusts the parameters of the adjustable gradient magnetic field according to the real-time position information of the catheter to guide the catheter along the travel path.

[0010] Optionally, it also includes a display device for displaying a three-dimensional model of the blood vessel and the real-time position of the catheter within the blood vessel, and providing an interactive interface for path adjustment.

[0011] Secondly, this application provides a combined embolization method based on an NdFeB permanent magnet guided intelligent neurointerventional catheter system, employing the system described in the first aspect, comprising: The catheter is inserted into the target vascular region via a vascular access route; An adjustable gradient magnetic field is generated by the external magnetic field generator to drive the magnetically controlled segment to deflect and guide the catheter along the vascular path to the target position. After the catheter reaches the target position, the parameters of the adjustable gradient magnetic field are adjusted to maintain the stability of the catheter position. An embolic agent is injected into the target location through the injection channel.

[0012] Optionally, driving the magnetically controlled segment to deflect in order to guide the catheter along the vascular pathway to the target location includes: The target path is determined based on preoperative vascular imaging data, and the intensity and direction of the adjustable gradient magnetic field are adjusted in real time according to the curvature changes of the vascular path during the catheter's travel.

[0013] Optionally, in the step of injecting the embolic agent into the target location through the injection channel, the injection speed of the embolic agent is dynamically adjusted according to the pressure feedback signal in the injection channel to inhibit the reflux of the embolic agent into non-target blood vessels.

[0014] The technical solution provided in this application has the following beneficial effects: This application utilizes multiple permanent magnet units with independent magnetization directions at the catheter tip, coupled with an externally adjustable gradient magnetic field drive, to replace traditional guidewire mechanical pushing in a non-contact manner. This reduces the force exerted by the catheter on the vessel wall and minimizes the risk of vascular injury. The structure connecting the magnetic units via flexible connectors allows the magnetically controlled segment to achieve multi-degree-of-freedom bending under a weak gradient magnetic field, enabling precise steering in tortuous vessels without relying on a high-intensity external magnetic field. Furthermore, the integrated design of the drug delivery channel running through the magnetically controlled segment allows for direct injection of embolic agents after the catheter is in position without replacement or adjustment. Adjusting the magnetic field parameters maintains catheter stability, reducing the risk of embolic agent reflux due to catheter displacement during embolization and shortening the procedure time. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the magnetically controlled conduit provided in an embodiment of this application.

[0016] Figure 2 Detailed diagram of the segmented magnetization configuration of the magnetic control section provided in the embodiments of this application.

[0017] Figure 3 This is a schematic diagram of the overall architecture of the intelligent magnetic navigation system provided in the embodiments of this application.

[0018] Figure 4 This is a schematic diagram illustrating the principle of magnetic field-driven conduit deflection provided in an embodiment of this application.

[0019] Figure 5 The overall flowchart of the combined embolization method provided in the embodiments of this application is shown.

[0020] Figure 6 This is a schematic diagram of the micro-orifice injection structure and drug injection channel at the tip of the catheter provided in the embodiments of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0024] This application provides an intelligent neurointerventional catheter system based on NdFeB permanent magnet guidance and its combined embolization method. Specifically, the system integrates multiple magnetic units made of NdFeB permanent magnet material at the catheter tip, and, in conjunction with an adjustable gradient magnetic field generated by an external electromagnetic coil array, applies directional magnetic force and torque to the magnetic units, thereby driving the catheter tip to achieve multi-degree-of-freedom deflection and precise steering within the blood vessel. A drug injection channel runs through the inside of the catheter, allowing for direct injection of embolic agents through this channel after the catheter is magnetically controlled into position without replacement or adjustment. This system solves the technical problems of existing neurointerventional catheters, such as the difficulty of navigation in tortuous blood vessels relying on guidewire mechanical propulsion, the reliance on high-intensity external magnetic fields for magnetically controlled catheters, and the instability and reflux of embolic agents caused by the separate navigation and embolization operations. It achieves the beneficial effects of reducing the need for external magnetic field strength, improving the ability to reach tortuous blood vessels, and reducing the risk of catheter displacement during embolization.

[0025] like Figure 5 As shown, this method includes the following steps: S100, the catheter is inserted into the target vascular region via a vascular access route.

[0026] like Figure 1 As shown, the overall structure of the catheter includes three main parts: a magnetically controlled section, a catheter body, and a connector.

[0027] The magnetron-controlled section, located at the distal end of the catheter, is the core functional area for achieving magnetic field-driven deflection. In one embodiment, the magnetron-controlled section comprises four magnetic units arranged sequentially along the axial direction. Each magnetic unit is made of NdFeB permanent magnet material with a magnetic energy product of not less than 48 MGOe. Each magnetic unit has a ring-shaped configuration with an outer diameter of 0.8 mm to 1.2 mm and an internal hollow channel for the drug delivery channel to pass through. The surface of the NdFeB permanent magnet is coated with a thickness of 5 μm to 10 μm. This titanium coating is ISO 10993 biocompatibility certified and is used to isolate the magnetic material from direct contact with biological tissue.

[0028] like Figure 2As shown, the four magnetic units are configured with segmented magnetization. For example, the magnetization directions of the first and third magnetic units are arranged along the axial direction of the catheter, i.e., the magnetization vector is parallel to the longitudinal axis of the catheter; the magnetization directions of the second and fourth magnetic units are arranged radially, i.e., the magnetization vector is perpendicular to the longitudinal axis of the catheter. This alternating arrangement of axial and radial magnetization ensures that when an adjustable gradient magnetic field is applied to the magnetically controlled segment, the magnetic torques experienced by each magnetic unit are in different directions, generating a composite deflection torque. This allows the magnetically controlled segment to achieve multi-degree-of-freedom bending in three-dimensional space, rather than being limited to deflection in a single plane. For example, when the direction of the external magnetic field gradually deflects from the axial direction to 30° with the axial direction, the torque experienced by the axially magnetized magnetic units tends to align them along the magnetic field direction, while the radially magnetized magnetic units experience a component torque perpendicular to their own magnetization direction. The combined effect of these two forces causes the magnetically controlled segment to undergo a three-dimensional bending deformation. By changing the direction angle and gradient distribution of the external magnetic field, the bending plane and curvature of the magnetically controlled segment can be continuously adjusted.

[0029] The magnetic units are connected by flexible connectors. In one embodiment, the flexible connector is a superelastic nickel-titanium alloy skeleton, which has superelastic properties and a strain recovery capacity of over 8%, far exceeding the elastic limit of ordinary metallic materials. The superelastic nickel-titanium alloy skeleton connects adjacent magnetic units in series, allowing the magnetically controlled segment to return to its original shape after bending under the influence of a magnetic field or when the magnetic field is removed or its direction is changed. In this configuration, the magnetically controlled segment supports 360° deflection, and the bending radius can be less than or equal to 2 mm. For example, when an external magnetic field generates a gradient magnetic field of 0.1 T in the catheter tip region, the four magnetic units, under the action of magnetic torque, cause the magnetically controlled segment to complete deflection within approximately 0.3 s, with a bending radius of approximately 2.5 mm. This response speed meets the real-time requirements for catheter steering in neurointerventional surgery.

[0030] The catheter body is the main structure connecting the magnetically controlled segment and the external connector. In this embodiment, the catheter body adopts a three-layer composite structure: the inner layer is the wall of the drug delivery channel, made of polytetrafluoroethylene (PTFE), which has chemical stability resistant to dimethyl sulfoxide (DMSO) corrosion, and is used to carry the delivery of ONYX embolic agent and its solvent DMSO; the middle layer is a braided reinforcement layer, made of stainless steel wire or nickel-titanium alloy wire, which provides the axial pushing force transmission capability and anti-kinking performance of the catheter body; the outer layer is a hydrophilic coating, which reduces the surface friction coefficient in a humid environment, thereby reducing the frictional resistance between the catheter and the blood vessel wall when traveling in the blood vessel. The inner diameter of the drug delivery channel is designed to withstand a flow rate of 0.1 mL / min to 0.3 mL / min, and its wall thickness and material selection ensure that the drug delivery channel does not deform or rupture within this flow rate range.

[0031] In step S100, the operator inserts the catheter through the vascular access established at the femoral or radial artery puncture point, and, with the assistance of a guide catheter, into the target blood supply area of ​​the internal carotid or vertebral artery. At this time, the external magnetic field generator is not yet activated; the catheter relies on its own mechanical compliance and the support of the guide catheter to complete the initial advancement from the puncture point to the major blood vessel at the base of the skull. Once the catheter tip enters the proximal region of the intracranial blood supply artery, the procedure proceeds to the magnetically controlled navigation stage in step S200.

[0032] S200, the external magnetic field generator generates an adjustable gradient magnetic field, which drives the magnetically controlled segment to deflect and guide the catheter along the vascular path to the target position.

[0033] like Figure 3 As shown, the extracorporeal magnetic field generator includes a ring-shaped array of electromagnetic coils and a magnetic field controller connected thereto. In one embodiment, the electromagnetic coil array includes 16 groups of electromagnetic coils distributed in a ring around the patient's head and neck. Each group of electromagnetic coils can independently control the magnitude and direction of its excitation current, thereby generating a magnetic field with a controllable gradient distribution within the three-dimensional spatial region where the catheter is located. The magnetic field strength generated by the electromagnetic coil array ranges from 0.1T to 0.5T, which is far lower than the 1.5T to 3.0T required by MRI equipment. This is due to the high energy product characteristics of NdFeB permanent magnet material. Since the magnetic control segment itself already has a strong remanent magnetization, the extracorporeal magnetic field only needs to provide a gradient torque for changing the orientation of the magnetic control segment, rather than a strong magnetic field for magnetizing the catheter tip material.

[0034] like Figure 4 As shown, when the extracorporeal magnetic field generator establishes a gradient magnetic field in the catheter tip region, the magnetic torque experienced by each magnetic unit can be expressed as the cross product of the magnetic moment vector of that magnetic unit and the external magnetic field vector. Since the magnetization directions of the four magnetic units are alternately set, different magnetic units generate torque components in different directions under the same external magnetic field. The control unit adjusts the excitation current of each set of electromagnetic coils to change the magnetic field gradient distribution in the catheter tip region, causing the combined effect of the torques experienced by each magnetic unit to produce a deflection in the target direction.

[0035] The control unit is communicatively connected to the magnetic field controller and receives preoperative 3D vascular reconstruction data from computed tomography (CT) or magnetic resonance angiography (MRI) to plan the optimal path from the current catheter position to the target lesion location. In one embodiment, the control unit incorporates a path planning algorithm that generates a series of discrete path points along the centerline direction based on the centerline extraction result of the 3D vascular model. For each path point, the algorithm calculates the deflection direction and angle required for the catheter tip to reach that point and converts them into corresponding electromagnetic coil excitation current parameters.

[0036] For example, the execution flow of the path planning algorithm is as follows: First, the centerline of the target blood supply artery is extracted from the preoperative 3D vascular model, and discrete path points are generated along the centerline at intervals of 0.5mm. For adjacent path points and Calculate the angle between the direction of the line connecting the two and the current orientation of the conduit. .when When the safe angle threshold is exceeded (exemplarily set to 15°), in and Intermediate path points are inserted between the points. For each path point, the control unit calculates the magnetic field gradient vector required to deflect the magnetically controlled segment to that direction, and determines the excitation current value of each coil by solving the inverse model of the electromagnetic coil array. The inverse model establishes a mapping relationship between the electromagnetic coil excitation current and the spatial magnetic field distribution based on the Biot-Savart law. For a given target magnetic field gradient vector, the optimal current distribution scheme is solved using the least squares method.

[0037] During catheter travel, the control unit dynamically adjusts the magnetic field parameters based on the catheter's real-time position. The real-time position of the catheter is obtained through intraoperative digital subtraction angiography. The control unit registers the intraoperative images with the preoperative 3D vascular model to determine the current position of the catheter tip in the 3D coordinate system and compares it with the planned path. When the catheter tip deviates from the planned path by more than a preset threshold (exemplarily set to 0.5 mm), the control unit recalculates the magnetic field gradient vector from the current position to the next path point and updates the coil excitation current, achieving closed-loop navigation control.

[0038] The navigation process can be described as follows: the catheter tip advances segmentally along the vascular path under the drive of a magnetic field. At each bifurcation point, the control unit adjusts the magnetic field gradient according to the target path direction, causing the catheter tip to deflect into the correct branch vessel. For the feeding arteries of cerebral arteriovenous malformations, the catheter must sequentially pass through the internal carotid artery, the main trunk of the middle cerebral artery and its branches, finally reaching the blood supply entrance of the malformation. At each vascular bifurcation point, the magnetically controlled segment completes precise turning under the drive of the gradient magnetic field, eliminating the need for the mechanical pushing force of the guidewire to overcome the resistance at the vascular bend, thereby reducing the mechanical contact force between the catheter and the vessel wall and reducing the risk of vasospasm and perforation.

[0039] S300, after the catheter reaches the target position, adjust the parameters of the adjustable gradient magnetic field to maintain the stability of the catheter position.

[0040] Once the catheter tip reaches the target location (i.e., the blood supply inlet of the malformation cluster of a cerebral arteriovenous malformation or the fistula opening of a dural arteriovenous fistula) under magnetic navigation in step S200, the system enters the position locking phase. In this phase, the control unit switches the magnetic field control mode from path tracking mode to position maintenance mode.

[0041] In position maintenance mode, the control unit continuously monitors the real-time position of the catheter tip and maintains the catheter tip at the target position by adjusting the excitation current of the electromagnetic coil of the external magnetic field generator. Specifically, the control unit acquires the position information of the catheter tip at a fixed period (every 100ms in this case) and calculates the deviation vector between the current position and the target position. When the magnitude of the deviation vector exceeds the position tolerance threshold (exemplarily set to 0.3mm), the control unit calculates the magnetic field gradient correction amount required to pull the catheter tip back to the target position and updates the excitation current of the corresponding electromagnetic coil.

[0042] The physical mechanism for maintaining the position is as follows: When the catheter tip experiences a slight displacement due to the impact of blood flow or the elastic restoring force of the blood vessel wall, the position of the permanent magnet unit in the magnetically controlled segment changes within the external gradient magnetic field, causing a change in the direction and magnitude of the magnetic force acting on it. The control unit adjusts the spatial distribution of the magnetic field gradient, causing the magnetic unit to experience a restoring force pointing towards the target position at the new position, thereby pulling the catheter tip back to the target position. This process is similar to a magnetic potential well, where the catheter tip is constrained within a spatial region near the target position.

[0043] For example, in a scenario of interventional treatment for a cerebral arteriovenous malformation, the target location is the entrance of a blood supply branch in the M3 segment of the middle cerebral artery, where the vessel diameter is approximately 0.5 mm and the blood flow velocity is approximately 20 cm / s. Under these blood flow conditions, the blood flow impact force on the catheter tip is approximately 0.01 N. The external magnetic field generator maintains a gradient magnetic field of 0.2 T in the target location region. The total magnetic force generated by the four magnetic units (each with a magnetic moment of approximately 0.5 mA·m²) in this gradient magnetic field is approximately 0.04 N, which is sufficient to overcome the blood flow impact force and maintain the catheter position stability. The position maintenance control cycle of the control unit is 100 ms. Within each control cycle, all operations of position detection, deviation calculation, and current update are completed, so that the position fluctuation of the catheter tip is controlled within ±0.3 mm.

[0044] After the position is locked, the system sends an instruction signal to the operator that the embolization injection can begin, and proceeds to step S400.

[0045] S400, an embolic agent is injected into the target location through the injection channel.

[0046] like Figure 6As shown, after the catheter position is stably locked, the operator injects an embolic agent into the target location through the injection channel. In one embodiment, the embolic agent is an ONYX liquid embolic agent, which is made by dissolving an ethylene-vinyl alcohol copolymer in a dimethyl sulfoxide solvent. Upon contact with blood, the DMSO solvent diffuses, and the ethylene-vinyl alcohol copolymer precipitates and solidifies to form an embolus.

[0047] The inner wall of the injection channel is made of polytetrafluoroethylene (PTFE), which has excellent resistance to DMSO corrosion, ensuring that the channel wall does not swell, dissolve, or degrade during embolization injection. The injection channel runs through the central region of the magnetically controlled segment, extending from the connector at the proximal end of the catheter to the outlet at the distal end. Because the injection channel and the magnetically controlled segment are integrated into the same catheter structure, the operator does not need to replace or reinsert the catheter after completing magnetic navigation; embolization can be administered directly through the injection channel of the same catheter, avoiding the risk of position loss due to catheter replacement in traditional step-by-step procedures.

[0048] In one embodiment, the distal outlet of the injection channel is provided with a micro-orifice jet structure. For example... Figure 6 As shown, the microporous injection structure includes multiple micropores distributed on the sidewall and end face of the catheter tip, with a pore size of 50 μm to 100 μm. When the embolic agent reaches the distal outlet through the injection channel under injection pressure, the embolic agent is injected into the target area (malformation or fistula) in a dispersed manner through multiple micropores, rather than being injected out from a single outlet in a concentrated jet manner. This dispersed injection method allows the embolic agent to penetrate more evenly into the abnormal vascular network inside the malformation, improving the filling rate of the embolic agent in the target area.

[0049] For example, the microporous jet structure includes 12 micropores, 8 of which are distributed on the sidewall of the catheter tip (uniformly distributed along the circumference) and 4 are distributed on the end face of the catheter tip. Each micropore has a diameter of 80 μm. At a total injection rate of 0.2 mL / min, the outlet flow rate of each micropore is approximately 0.017 mL / min. This corresponding outlet jet velocity is much lower than the jet velocity of a single outlet, thereby reducing the risk of embolic agent reflux into non-target vessels due to high-speed jetting.

[0050] In one embodiment, the system further includes a pressure sensor located within the injection channel. The pressure sensor is situated in the proximal region of the injection channel (near the connector side) and is used to detect the liquid pressure within the injection channel in real time. The control unit dynamically adjusts the injection rate of the embolic agent based on the pressure sensor's readings. Specifically, the control unit presets a pressure safety threshold (exemplarily set to 200 kPa). When the pressure within the injection channel exceeds this threshold, it indicates increased flow resistance of the embolic agent in the target area (possibly due to partial filling of the target area or blockage of the outlet micropores by solidified embolic agent). The control unit automatically reduces the output flow rate of the injection pump to prevent further pressure increases that could lead to embolic agent backflow. When the pressure drops below the safety threshold, the control unit restores the normal injection flow rate.

[0051] For example, in an ONYX embolization procedure, the initial injection rate is set to 0.15 mL / min. When the pressure sensor detects that the pressure within the injection channel is gradually increasing from the initial 100 kPa to 180 kPa, the control unit maintains the current injection rate. When the pressure reaches 200 kPa, the control unit reduces the injection rate to 0.08 mL / min. When the pressure further increases to 250 kPa, the control unit pauses the injection and issues an alarm, prompting the operator to assess the embolization progress. Once the operator confirms that it can continue, the control unit resumes the injection at a low rate of 0.05 mL / min. Throughout the injection process, the magnetic field generator maintains the position lock established in step S300, ensuring that the catheter tip does not shift during the injection.

[0052] After the embolization injection is completed, the operator injects a small amount of saline through the injection channel to flush out any residual embolic agent and prevent the ONYX in the injection channel from solidifying and clogging the catheter. Subsequently, the control unit gradually reduces the intensity of the external magnetic field, releasing the magnetic constraint on the catheter tip, and the operator slowly withdraws the catheter from the blood vessel along its original path.

[0053] like Figure 3 As shown, this application also provides a specific implementation of an intelligent neurointerventional catheter system based on permanent magnet guidance. The system comprises three core components: a catheter, an external magnetic field generator, and a control unit.

[0054] The physical structure of the catheter, as described in step S100, includes a distal magnetically controlled segment, a drug delivery channel running the entire length, and a three-layer composite catheter body. The four NdFeB magnetic units of the magnetically controlled segment are connected in series via a superelastic nickel-titanium alloy skeleton, with an overall outer diameter not exceeding 1.2 mm, allowing it to be delivered into the target vascular region via a standard 6F guide catheter.

[0055] The hardware implementation of the extracorporeal magnetic field generator includes: 16 sets of electromagnetic coils mounted in a ring array on an adjustable head support, which can be adjusted according to the patient's head size to ensure a consistent distance between the coil array and the patient's head. Each set of electromagnetic coils is powered by an independent current driver with an output range of 0A to 10A and a current resolution of 0.01A. The coordinated operation of the 16 sets of electromagnetic coils generates a controllable gradient magnetic field within the three-dimensional spatial region where the catheter is located, with a magnetic field strength range of 0.1T to 0.5T and a gradient resolution better than 0.01T / cm.

[0056] The hardware implementation of the control unit includes an industrial computer and a connected magnetic field controller. The industrial computer runs path planning and position maintenance control algorithms, receiving preoperative vascular imaging data and intraoperative catheter position information as input, and outputting the target excitation current value for each electromagnetic coil. The magnetic field controller receives the current command output from the industrial computer and drives each electromagnetic coil to generate the target magnetic field through digital-to-analog conversion and power amplification. The control unit has a control cycle of 100ms, meaning it executes a closed-loop control cycle of position detection-deviation calculation-current update 10 times per second.

[0057] In one embodiment, the system further includes a display device. The display device is connected to the control unit and is used to display a three-dimensional model of the blood vessel and the real-time position of the catheter within the vessel. The display device presents the preoperatively acquired three-dimensional reconstructed blood vessel model in a semi-transparent manner and highlights the real-time position of the catheter tip and the planned travel path within the model. The surgeon can adjust the target position or modify the travel path through the touch interface provided by the display device, and the control unit updates the magnetic field control parameters in real time according to the surgeon's adjustment commands.

[0058] During the catheter navigation process, the system employs different magnetic field control strategies to adapt to the respective vascular anatomy characteristics for different types of cerebrovascular lesions.

[0059] For interventional treatment of cerebral arteriovenous malformations (AVMs), the feeding arteries of the malformation typically exhibit multi-level bifurcation and acute-angle bends. For example, the bifurcation angle at the M2 to M3 segment of the middle cerebral artery can reach 60° to 90°, and the branch vessel diameter ranges from 1.0 mm to 1.8 mm. In this scenario, the control unit employs a step-by-step advancement strategy: first, catheter advancement is paused proximal to the bifurcation, and the magnetic control segment is pre-deflected towards the entrance direction of the target branch vessel by adjusting the magnetic field direction; then, the catheter is advanced at a low speed (exemplarily 1 mm to 2 mm per second) until its tip enters the target branch; after entering the branch, the magnetic field gradient direction is immediately adjusted to adapt to the new course of the branch vessel. This step-by-step advancement strategy avoids the risk of the catheter tip impacting the vessel wall due to excessive advancement speed at acute-angle bifurcation points.

[0060] For interventional treatment of dural arteriovenous fistulas, the blood supply arteries to the fistula are typically branches of the middle meningeal artery or occipital artery. These vessels originate from the external carotid artery system, pass through the cranial canal, and enter the cranium via a relatively fixed but narrow pathway. In this scenario, the path planning algorithm of the control unit uses preoperative imaging data to accurately reconstruct the vascular path within the cranial canal, using the canal wall as a constraint boundary for catheter movement. The magnetic field control parameters are adjusted to ensure the catheter tip travels along the centerline of the cranial canal, avoiding contact between the catheter tip and the canal wall. For example, when the inner diameter of the cranial canal is 1.0 mm to 1.8 mm, the gap between the catheter tip and the canal wall is only 0.1 mm to 0.3 mm, and the control unit reduces the position tolerance threshold to 0.05 mm.

[0061] In terms of embolization procedures, the system offers different injection parameter configurations for different types of embolic agents and different lesion characteristics.

[0062] For the injection of ONYX embolic agent, since the solidification rate of ONYX after contact with blood depends on the diffusion rate of DMSO solvent into the surrounding blood and tissues, the injection rate needs to be matched with the solidification rate. In high-flow lesions (e.g., blood flow velocity exceeding 30 cm / s), ONYX may be dispersed by the blood flow after injection, resulting in uneven solidification. In this case, the control unit sets the injection rate to a lower value (exemplarily 0.1 mL / min) and adopts an intermittent injection mode: each injection lasts for 30 seconds, followed by a 60-second pause. In low-flow lesions (e.g., blood flow velocity below 10 cm / s), the solidification rate of ONYX is faster, and the control unit sets the injection rate to 0.2 mL / min to 0.3 mL / min.

[0063] During injection, the pressure sensor is used not only to dynamically adjust the injection speed but also to determine the progress of embolization and detect abnormalities. The control unit establishes a pressure-injection time curve within the injection channel. During normal embolization, the pressure within the injection channel gradually increases as the target area is gradually filled with the embolic agent. When the rate of pressure increase suddenly increases (for example, the pressure rises by more than 30 kPa within 10 seconds), it may indicate that the outlet micropores are blocked by solidified embolic agent or that the target area is nearly completely filled. When the pressure suddenly drops, it may indicate that the embolic agent has breached the boundary of the target area and entered the draining vein. At this point, the control unit immediately pauses the injection and issues an alarm.

[0064] The biocompatibility and safety design of the catheter follows these principles. The titanium coating on the surface of the NdFeB permanent magnet is deposited using magnetron sputtering, with a coating thickness of 5 μm to 10 μm. The bonding strength between the coating and the substrate is no less than 30 MPa, ensuring that the coating does not detach under catheter bending and blood flushing conditions. The biocompatibility of the titanium coating is verified through cytotoxicity testing, sensitization testing, and acute systemic toxicity testing in the ISO 10993 series of standards. The polytetrafluoroethylene inner wall of the injection channel undergoes surface modification treatment to reduce its surface energy to 20 mN / m, reducing the adhesion tendency of the ONYX embolic agent to the channel wall and minimizing the amount of embolic agent residue in the channel after injection.

[0065] The superelastic nickel-titanium alloy skeleton is made of nickel-titanium alloy (atomic ratio approximately Ni 50.8:Ti 49.2), with an austenite termination temperature lower than body temperature (37°C), ensuring that the material remains in a fully austenitic state at the working temperature inside the human body, thus exhibiting superelastic properties. The skeleton has a wire diameter of 0.05mm to 0.08mm and is processed by laser cutting or electrochemical etching. The surface is electrolytically polished to eliminate burrs and improve surface finish.

[0066] The hydrophilic coating on the outer layer of the catheter is formed by applying polyvinylpyrrolidone (PVP) using a UV curing process. The hydrophilic coating has a dynamic friction coefficient of no more than 0.05 in a wetted state, which is an order of magnitude lower than that of an uncoated catheter (typically 0.2 to 0.4). This low-friction characteristic significantly reduces the friction between the catheter and the vessel wall during its movement within the blood vessel, and, combined with magnetic field driving force, enables smooth catheter advancement in tortuous vessels. The hydrophilic coating is required to retain at least 90% of its coating after 500 bending cycles in a simulated vascular environment.

[0067] The electromagnetic coils of the external magnetic field generator are made of copper enameled wire, with each coil having 500 turns. The core material is a laminated structure of silicon steel sheets with high saturation magnetic flux density. The total power consumption of the 16 coils does not exceed 2kW, and the coil temperature does not exceed 60°C during operation. The coil array is designed to be able to be installed in a standard digital subtraction angiography operating room without affecting the normal rotation and imaging operation of the C-arm of the angiography equipment. The magnetic field uniformity of the magnetic field generator is better than ±5% in the catheter operation area (a spherical area with a radius of 5cm centered on the geometric center of the coil array).

[0068] The path planning algorithm and position maintenance control algorithm of the control unit both run on the industrial computer. The processing power of the industrial computer is sufficient to complete the following calculations within a 100ms control cycle: receiving intraoperative image data and registering it with the preoperative model (calculation time approximately 30ms), calculating the three-dimensional position coordinates of the catheter tip (calculation time approximately 15ms), performing path deviation detection and magnetic field gradient correction calculations (calculation time approximately 20ms), solving the electromagnetic coil inverse model and outputting current commands (calculation time approximately 25ms). The remaining 10ms is used as a safety margin.

[0069] The display device employs a high-resolution touchscreen with a resolution of at least 1920×1080. The display latency is no more than 50ms, allowing the operator to observe the catheter's movement within the blood vessel in near real-time. The interactive interface provides the following functions: finger dragging adjusts the target position, pinch gestures zoom the display scale of the 3D blood vessel model, and two-finger rotation changes the viewing angle. Every interface operation performed by the operator is captured in real-time by the control unit and converted into update instructions for the magnetic field control parameters.

[0070] In clinical applications, the system's workflow can be summarized as follows: Preoperative preparation stage: acquiring the patient's CTA or MRA image data and performing three-dimensional vascular reconstruction, marking the target lesion location and the planned catheter travel path on the display device; Surgical operation stage: sequentially executing steps S100 to S400 to complete magnetic navigation and combined embolization; Postoperative evaluation stage: confirming the embolization effect (disappearance or significant reduction of blood flow in the target area) through postoperative angiography, and assessing whether secondary treatment is required.

[0071] The system was tested in vitro using a 3D-printed cerebral vascular model. This 3D-printed model, based on CTA image data from real patients, simulated the complex vascular anatomy of cerebral arteriovenous malformations, including multi-level bifurcation, acute-angle bends, and vessel segments of varying diameters. Simulated blood (a glycerol-water mixture, viscosity adjusted to 3.5 mPa·s) was injected into the model, and a peristaltic pump generated a pulsatile flow rate ranging from 50 mL / min to 200 mL / min. The catheter's successful placement rate, navigation time, and embolization rate within the model were all used as performance evaluation metrics for the system.

[0072] In a more specific embodiment, taking an interventional treatment of a left temporal lobe arteriovenous malformation as an example, the complete operation procedure of the system and method is described in detail.

[0073] The patient's malformation was located in the middle of the left temporal lobe, supplied by two branches of the M3 segment of the middle cerebral artery. The malformation was approximately 2 cm in diameter, and the main draining vein was the Labbe vein. Preoperative CTA scan data showed that the total length of the path from the terminal internal carotid artery to the blood supply point of the malformation was approximately 12 cm, passing through three vascular bifurcation points. The narrowest segment had an inner diameter of 1.2 mm, and the maximum curvature angle was 85°.

[0074] During the preoperative preparation phase, the surgeon imports the CTA vascular 3D model into the path planning system of the control unit. The system automatically extracts the centerline of the target feeding artery and generates path points at 0.5mm intervals. The path planning algorithm identifies three key nodes at bifurcation points where magnetic steering needs to be performed and pre-calculates magnetic field control parameters for each key node. For the second bifurcation point (the bifurcation of the middle cerebral artery M2-M3, with a bifurcation angle of 85°), the algorithm densifies the path points within a 2mm range before and after this point at 0.5mm intervals, decomposing the total deflection of 85° into multiple steps, each step approximately 7° to 8°, ensuring that the deflection in each step does not exceed the safe angle threshold of 15°.

[0075] After the surgery began, the surgeon established an arterial access via right femoral artery puncture and, with the assistance of a guiding catheter, inserted the catheter into the distal end of the left internal carotid artery. At this point, the catheter tip was approximately 3 cm from the first bifurcation point, and the surgeon activated the external magnetic field generator.

[0076] During navigation at the first bifurcation point (the junction between the terminal internal carotid artery and the beginning of the M1 segment of the middle cerebral artery), the bifurcation angle is approximately 45°. The control unit generates a gradient magnetic field pointing towards the entrance of the M1 segment in this bifurcation point region, based on pre-calculated parameters. The field strength is 0.15T, and the gradient is 0.5T / m. The total deflection torque generated by the four magnetic units of the magnetically controlled segment under the action of this gradient magnetic field is approximately 5 × 10⁻⁶. -4 The magnetic field was activated, causing the magnetically controlled segment to deflect 45° within 0.3 seconds, allowing the catheter tip to smoothly enter segment M1. The total time from activating the magnetic field to passing through the first bifurcation point was approximately 2 minutes.

[0077] During navigation at the second bifurcation point (M2-M3 bifurcation), due to the bifurcation angle of 85° and the branch vessel diameter of only 1.2mm, the control unit adopted a step-by-step advancement strategy. 3mm before the catheter tip reaches the bifurcation point, the control unit gradually rotates the magnetic field direction from the M2 segment direction to the M3 segment direction, completing a total deflection of 85° in 12 steps. After each deflection, the catheter advances 0.5mm at a speed of 1mm / s. Subsequently, the control unit performs position deviation detection, confirming that the deviation between the catheter tip and the preset path is within 0.3mm. The total time to pass through this bifurcation point is approximately 2 minutes. During the catheter's passage through the bifurcation point, the display device shows the real-time position of the catheter tip in the 3D model of the vessel, allowing the operator to observe the deflection process of the catheter tip closely matching the preset path.

[0078] During navigation at the third bifurcation point (from the end of segment M3 to the inlet of the feeding artery of the malformation), the bifurcation angle was approximately 45°, and the inner diameter of the branch vessel was 0.8 mm. Due to the extremely small size of the vessel, the control unit increased the magnetic field gradient to 0.8 T / m. The catheter tip entered the inlet of the feeding artery under magnetic field guidance, and the time taken to pass through this bifurcation point was approximately 3 minutes.

[0079] After the catheter tip reaches the blood supply inlet of the malformation (i.e., step S200 is completed), the system enters the position locking stage in step S300. The control unit switches the magnetic field control mode to the position maintenance mode, establishing a magnetic potential well in the blood supply inlet area of ​​the malformation. At this time, the catheter tip is approximately 1 mm from the edge of the malformation, which is the optimal embolization injection position. After the position maintenance mode is activated, the control unit monitors that the position fluctuation of the catheter tip under blood flow impact is ±0.15 mm, which is much less than 0.3 mm, confirming successful position locking.

[0080] Proceed to the embolization injection stage of step S400. The operator first injects 0.3 mL of DMSO pre-flushing solvent through the injection channel (to prevent premature solidification and clogging of the channel by ONYX), and then begins injecting ONYX-18 embolic agent (viscosity 18 cps, suitable for small deformities). The initial injection rate is set to 0.12 mL / min, and the pressure sensor shows an initial channel pressure of 110 kPa.

[0081] In the first 3 minutes after injection, ONYX enters the malformation in a dispersed manner through 12 micropores. Intraoperative DSA images simultaneously displayed on the monitor show ONYX permeating and diffusing from the injection site into the surrounding abnormal vascular network. The channel pressure slowly increases from 110 kPa to 150 kPa, while the control unit maintains the current injection rate.

[0082] Between the 4th and 6th minute after injection, as the blood vessels inside the malformation were gradually filled with ONYX, the rate of increase in channel pressure accelerated, rising from 150 kPa to 185 kPa. The surgeon observed via DSA imaging that ONYX had filled approximately 60% of the malformation.

[0083] At 7 minutes into the injection, the channel pressure reached 195 kPa, approaching the safety threshold of 200 kPa. The control unit automatically reduced the injection rate from 0.12 mL / min to 0.08 mL / min. The pressure briefly stabilized between 190 kPa and 195 kPa.

[0084] Between 8 and 10 minutes after injection, the channel pressure reached 210 kPa, exceeding the safety threshold. The control unit further reduced the injection rate to 0.05 mL / min. DSA imaging showed that ONYX had filled approximately 80% of the malformed mass, and a small amount of ONYX began to seep towards the main draining vein.

[0085] At the 11-minute mark of injection, the channel pressure fluctuated between 230 kPa and 250 kPa, with a pressure rise rate exceeding 5 kPa / s. The control unit immediately paused the injection and issued an alarm. After reviewing the DSA images, the operator confirmed that the malformation had been adequately embolized (approximately 95% filling rate) and decided to terminate the embolization injection.

[0086] After injection, the operator flushes away any residual embolic agent by injecting 0.5 mL of saline through the injection channel to prevent blockage. The control unit linearly reduces the magnetic field strength from 0.2 T to zero within 30 seconds, smoothly releasing the magnetic constraint on the catheter tip. With the aid of the guiding catheter, the operator slowly withdraws the catheter along its original path.

[0087] Immediately after the procedure, DSA angiography showed that blood flow in the feeding arteries of the malformation had completely disappeared, and the malformation was uniformly filled with ONYX. Only a trace amount of ONYX (not exceeding 3 mm in length) permeated the main draining vein, and no accidental embolization occurred. The total time for the entire magnetically guided embolization procedure was approximately 2 hours, which was about 40% shorter than the average procedure time (approximately 3.5 hours) when the surgeon used a conventional guidewire to push the microcatheter. The number of intraoperative DSA fluoroscopy sessions was reduced from an average of 50 to approximately 20, resulting in a corresponding reduction in radiation exposure for both the surgeon and the patient.

[0088] It should be noted that the force and torque experienced by the permanent magnet unit in the magnetic control section in the external gradient magnetic field can be obtained from the basic principles of electromagnetism.

[0089] Specifically, for a vector with a magnetic moment The magnetic unit, when placed in a non-uniform magnetic field ( In ) the magnetic force The gradient of the dot product of the magnetic moment and the magnetic field is... The direction of this magnetic force points in the direction of increasing magnetic field strength (when the magnetic moment is in the same direction as the magnetic field), and its magnitude is proportional to the magnitude of the magnetic moment and the magnitude of the magnetic field gradient. The magnetic torque experienced... It is the cross product of the magnetic moment and the magnetic field, i.e. This torque tends to align the magnetic moment vector with the external magnetic field vector.

[0090] In the configuration of the four magnetic units in the magnetically controlled section, the first magnetic unit (axially magnetized) will be used as an example for explanation. Let its magnetic moment vector be... Along the axial direction (let's call it the z-axis), the magnitude is When the direction of the external magnetic field at the location of the magnetic unit deviates from the axial angle... The magnitude of the magnetic torque is For example, when =0.2T、 When = 30°, The torque synthesis effect of the four magnetic units depends on the relationship between the magnetization direction of each magnetic unit and the direction of the external magnetic field. Due to the alternating axial and radial magnetization configuration, each magnetic unit generates torque components in different directions within the same external magnetic field. By precisely adjusting the direction and gradient distribution of the external magnetic field, the control unit can selectively excite the torque contribution of specific magnetic units, thereby achieving deflection of the magnetically controlled segment in any direction.

[0091] For example, when the magnetically controlled segment needs to deflect 45° to the left in the horizontal plane, the control unit establishes a gradient magnetic field with its main direction deflected 45° to the left in the horizontal plane within the region where the magnetically controlled segment is located. The torques acting on the first and third magnetic units (axial magnetization) drive their magnetization directions to rotate in the direction of the magnetic field, generating a torque that causes the entire magnetically controlled segment to bend. The torques acting on the second and fourth magnetic units (radial magnetization) are in a different direction than those acting on the axial magnetization units, but under the constraint of the superelastic nickel-titanium alloy skeleton, the torques of all magnetic units are transmitted and combined through the skeleton, ultimately generating a resultant torque that causes the magnetically controlled segment to bend in the target direction. When the magnetically controlled segment needs to deflect upward in the vertical plane, the control unit adjusts the direction of the magnetic field to deflect it in the vertical plane, and the combined effect of the torques generated by each magnetic unit also causes the magnetically controlled segment to bend in the target direction. By changing the azimuth and elevation angles of the magnetic field direction, the deflection of the magnetically controlled segment in all 360° omnidirectional space can be achieved.

[0092] The control unit incorporates an inverse electromagnetic coil model to calculate the excitation current of each coil from the target magnetic field distribution. The mathematical basis of this inverse model is as follows.

[0093] Let the excitation current vector of the 16 sets of electromagnetic coils be... The target magnetic field gradient vector at the location of the catheter tip is: According to the Biot-Savart law, the magnetic field gradient generated by each coil at the tip of the guide tube is linearly related to its excitation current. Therefore, a linear mapping relationship can be established. Where A is a 3×16 system matrix, and its element a jk Determined by calibration experiments. Matrix A remains fixed after calibration.

[0094] Because the number of coils (16 groups) exceeds the number of magnetic field gradient directions (3), this system is an over-constrained system, and the least squares method is used to solve the inverse model. The goal is to find the current vector. Make Minimize. The analytical solution to this optimization problem is: Within each 100ms control cycle, the control unit converts the current conduit position and target deflection direction into a target magnetic field gradient vector, substitutes it into the above formula to calculate the target current value of each coil, and drives each coil to generate the corresponding magnetic field through the magnetic field controller.

[0095] For example, the system matrix A is measured in a calibration experiment for a target magnetic field gradient. (The magnetic field at the front end of the conduit is required to be between 0.5T / m and 0.3T / m). The inverse model calculates that the excitation current of each coil is distributed between -5A and 5A, which is within the output range (0A to 10A) of each coil driver.

[0096] It should be noted that the position maintenance control algorithm employs a proportional-integral control strategy. Let the position of the catheter tip in the kth control cycle be... The target location is The positional deviation is The control unit calculates the magnetic field gradient correction. :

[0097] in, For proportional gain, For integral gain, =100ms is the control period. Proportional term. This generates a corrective force proportional to the deviation, causing the catheter tip to rapidly approach the target position. (Integral term) Used to eliminate steady-state errors, when there is a continuous blood flow impact force that causes a constant offset at the catheter tip, the integral term can gradually increase the correction force until the offset is fully compensated.

[0098] For example, in the control unit =50T / (m·mm), =5T / (m·mm·s). When the catheter tip is impacted by blood flow... =[0.2,0.1,0] When the positional deviation is mm, the gradient correction amount generated by the proportional term is: =[10,5,0] T / m. This correction amount is converted into the current adjustment amount of each coil through the inverse model. The change in the magnetic field gradient generated by the electromagnetic coil array guides the magnetocontrol section to generate a restoring force towards the target position, pulling the conduit tip back to the target position. Under normal operating conditions, it takes 300ms to 500ms, or 3 to 5 control cycles, for the conduit tip to recover from a deviation of 0.2mm to within 0.05mm.

[0099] To prevent over-adjustment due to integral saturation, the control algorithm sets an upper limit constraint on the integral term. When the magnitude of the integral term exceeds 5T / m, the accumulation of new deviation values ​​stops until the integral term falls back below the threshold. Furthermore, when the position deviation remains within 0.05mm for 10 consecutive control cycles, the control unit determines that the position lock has stabilized and reduces the control gain to the steady-state maintenance gain. =0.5 , =0.5 This reduces the energy consumption of the control system and the heat generated by the electromagnetic coil.

[0100] Furthermore, the flow characteristics of ONYX embolic agents within the injection channel are crucial for the design of injection control strategies. ONYX-18 has a viscosity of approximately 18 cps (0.018 Pa·s) and a density of approximately 1.06 g / cm³. 3 The inner diameter of the injection channel is 0.4 mm, and its length is approximately 150 cm (the total length from the connector to the distal end of the catheter).

[0101] Under laminar flow conditions, the pressure drop within the injection channel can be estimated using Poiseuille's formula. Specifically, for steady laminar flow within a circular pipe, the pressure drop... The relationship between flow rate Q, pipe length L, pipe diameter d, and viscosity μ is as follows:

[0102] For example, when the injection rate Q = 0.15 mL / min = 2.5 × 10 -9 m 3 / s, channel inner diameter d=0.4mm=4×10 -4 When the channel length L = 1.5 m and the ONYX viscosity μ = 0.018 Pa·s, the theoretical pressure drop within the channel is: =(128×0.018×1.5×2.5×10 -9 ) / (π×(4×10 -4 ) 4) = (8.64 × 10 -9 ) / (8.04×10 -14 )≈107kPa The theoretically calculated value is basically consistent with the actual measured initial channel pressure of 110 kPa (the difference comes from the local resistance of the microporous injection structure and the additional losses at the channel bends). As the blood vessels inside the malformed cluster on the channel outlet side are gradually filled with ONYX, the back pressure at the outlet increases, leading to a corresponding increase in the pressure inside the channel. The pressure value detected by the pressure sensor reflects the total pressure on the channel inlet side (including channel pressure drop and outlet back pressure). When this total pressure exceeds the safety threshold, it means that the outlet back pressure is too high, and continuing to inject at the current rate may cause ONYX to reflux proximally.

[0103] In addition, the local flow characteristics of the microporous injection structure also affect the embolization effect.

[0104] Here, each micropore can be considered a short-tube flow problem, with resistance primarily arising from inlet contraction losses and tube wall friction losses. For example, for an pore diameter of 80 μm and a channel length of 200 μm, when the flow rate per pore is 0.017 mL / min, the Reynolds number within the micropore is approximately... =(1060×0.056×8×10 -5 The value of 0.018 / (0.018) ≈ 0.26 is much smaller than the critical value for the laminar-turbulent transition; among which, For the density of the embolic agent, For micropore single-pore flow velocity, For micropore diameter, The viscosity of the embolic agent is [value missing]. Therefore, the flow within the micropores is completely laminar. ONYX is ejected from the micropores in a low-speed laminar flow manner and slowly penetrates the target area by diffusion, without producing embolic agent splashing or backflow caused by high-speed turbulent jets.

[0105] The selection of the micropore size needs to strike a balance between permeation efficiency and anti-clogging. While a smaller pore size (e.g., 30 μm) allows ONYX to enter the target area as a finer jet, the ethylene-vinyl alcohol copolymer particles in ONYX, with a diameter of approximately 5 μm to 15 μm, may cause particle clogging. A larger pore size (e.g., 200 μm) results in a loss of dispersion injection effectiveness, degenerating into a concentrated jet near a single outlet. The optimal pore size range is 50 μm to 100 μm.

[0106] In addition, the magnetic field generated by the external magnetic field generator during operation must meet the requirements of the electromagnetic safety standards for medical devices. According to the IEC 60601-1-2 standard, the electromagnetic radiation from the magnetic field generator must not interfere with the normal operation of other medical equipment in the operating room (such as electrocardiogram monitors, pulse oximeters, and digital subtraction angiography equipment).

[0107] Regarding electromagnetic compatibility, the excitation current of the 16 sets of electromagnetic coils adopts DC or low-frequency AC (frequency not exceeding 100Hz) driving methods. The electromagnetic radiation power of the low-frequency magnetic field is extremely low and will not interfere with radio frequency sensitive equipment in the operating room. The current driver of the magnetic field controller adopts a linear amplifier topology instead of a switching topology, avoiding electromagnetic interference from switching noise to surrounding equipment. Each current driver output is equipped with an LC low-pass filter with a cutoff frequency set to 1kHz to further suppress the radiation of high-frequency harmonic components.

[0108] Regarding patient safety, the magnetic field strength generated by the magnetic field generator (0.1T to 0.5T) is significantly lower than the operating magnetic field strength of MRI equipment (1.5T to 3.0T), and the exposure time is limited (typically no more than 1 hour). According to the guidelines of the International Commission on Non-Ionizing Radiation Protection, static magnetic field exposure of this intensity and duration will not produce thermal or neurostimulatory effects on human tissue. The control unit has a built-in magnetic field strength monitoring function; when the magnetic field strength in any coil area exceeds 0.6T, the system automatically reduces the excitation current of the coil in that area and issues an alarm.

[0109] The collaborative working scheme between the magnetic field generator and the digital subtraction angiography (DSA) equipment is as follows: During DSA exposure acquisition (each exposure lasts approximately 20ms to 50ms), the control unit temporarily freezes the current regulation of the electromagnetic coil (maintaining the current value unchanged) to avoid transient magnetic field interference with DSA image quality caused by current changes. During the DSA exposure interval (typically 200ms to 500ms), the control unit resumes normal magnetic field regulation operation. This time-division multiplexing strategy allows magnetic field control and DSA imaging to be performed alternately in the same operating room without interference. The control unit obtains exposure timing information through a synchronization signal interface with the DSA equipment, achieving precise timing coordination.

[0110] Following the catheter withdrawal phase after embolization, special care must be taken to prevent ONYX residue at the catheter tip from adhering to the vessel wall, which could lead to difficulty in withdrawal or vessel damage. To address this, the system employs the following safety mechanisms: First, immediately after injection, flush the catheter tip area with DMSO solvent through the injection channel. DMSO dissolves any incompletely cured ONYX residue, restoring the catheter tip surface to a smooth state. The flushing volume is 0.3 mL to 0.5 mL, and the flushing time is 30 seconds.

[0111] Secondly, before withdrawing the catheter, the control unit executes a preset magnetic field release sequence. This sequence linearly reduces the magnetic field strength from the working level (0.2T) to zero within 30 seconds, while slowly rotating the magnetic field direction, causing the magnetically controlled segment to produce a slight oscillating motion during the magnetic field release. This oscillating motion helps to loosen any slight adhesions that may exist between the catheter tip and surrounding tissue.

[0112] Finally, the operator withdraws the catheter slowly at a speed not exceeding 5 mm / s. The pressure sensor continuously monitors pressure changes within the injection channel during withdrawal. If the withdrawal resistance increases abnormally (manifested as a sudden increase in pressure within the injection channel exceeding 50 kPa), the system issues an alarm prompting the operator to pause withdrawal and assess the cause. The operator can choose to reinject a small amount of DMSO to dissolve the adhesions before continuing withdrawal, or reactivate the magnetic field to deflect the magnetically controlled segment, thereby changing the orientation of the catheter tip and releasing the adhesions.

[0113] For large cerebral arteriovenous malformations (malformation clusters exceeding 3 cm in diameter), multiple embolization surgeries are usually required. This system supports the implementation of a multiple embolization strategy. In the first embolization procedure, the surgeon selects a major feeding artery of the malformation as the target, and uses the magnetic navigation system to guide the catheter to the entrance of that feeding artery and perform embolization. After embolization, the control unit saves the catheter travel path data, magnetic field control parameters, and embolization injection parameters of this procedure to the patient database.

[0114] In the subsequent embolization procedure, the surgeon selects another feeding artery as the target. The control unit retrieves the path data saved from the previous surgery and automatically plans the path from the vascular access to the new target location. Since the previous embolization had partially blocked the feeding artery, the vascular anatomy may have changed (e.g., the establishment of collateral circulation leading to a new blood supply path). The control unit compares and analyzes the newly acquired preoperative CTA images with the images from the previous surgery to identify changes in vascular structure and adjust the path planning accordingly.

[0115] In a multi-stage embolization strategy, the embolization target and injection parameters may differ for each procedure. For high-flow feeding arteries in the core region of the malformation, a lower injection rate (0.1 mL / min) and intermittent injection mode are used to ensure adequate ONYX solidification. For low-flow feeding arteries in the peripheral region of the malformation, a higher injection rate (0.2 mL / min to 0.3 mL / min) is used to improve embolization efficiency. The control unit automatically recommends appropriate injection parameter configurations based on the target feeding artery type selected by the operator, and the operator can adjust these values ​​based on the recommendations.

[0116] After 2 to 4 staged embolization procedures, when postoperative angiography shows a total embolization rate of over 80% for the malformation, subsequent radiosurgery or microsurgical resection can be considered to completely eliminate the remaining malformation. The system's multiple embolization data recording function provides complete imaging and operational parameter references for the formulation of subsequent treatment plans.

[0117] It should be noted that, compared with existing magnetically controlled conduit systems (such as magnetically controlled conduits based on soft magnetic materials), the technical solution of this application has the following distinctive technical features: The working principle of existing soft magnetic controlled catheters is as follows: a soft magnetic material (such as ferrite or permalloy) is embedded at the tip of the catheter and magnetized under the influence of a strong external magnetic field. The magnetized soft magnetic material is then deflected by a force within the magnetic field gradient. An inherent drawback of this approach is that the magnetization intensity of the soft magnetic material depends on the strength of the external magnetic field. When the external magnetic field is weak, magnetization is insufficient, and the resulting deflection force is inadequate to overcome the constraints of the blood vessel wall and the impact of blood flow. Therefore, existing soft magnetic controlled catheters typically require a strong magnetic field of 0.5T or higher to drive them. This necessitates the use of MRI equipment or large superconducting magnets as the magnetic field source, resulting in high equipment costs and limited operating room space.

[0118] This application uses NdFeB permanent magnet material to replace soft magnetic material. The fundamental difference lies in the fact that permanent magnet material has high remanent magnetization (B). (≥1.2T) can maintain a strongly magnetized state without the need for an external magnetic field. The external magnetic field only needs to provide gradient torque to change the orientation of the magnetic units, rather than a strong magnetic field for magnetizing the material. Therefore, a weak gradient magnetic field of 0.1T to 0.5T is sufficient to drive it. This allows the external magnetic field generator to be implemented using a conventional electromagnetic coil array, eliminating the need for superconducting magnets or MRI equipment, significantly reducing the size and cost of the device, and enabling its use in a standard DSA operating room without affecting the normal operation of the imaging equipment.

[0119] Furthermore, the segmented magnetization configuration (alternating axial and radial) of this application enables the magnetically controlled segment to achieve multi-degree-of-freedom bending in three-dimensional space, while existing soft magnetically controlled catheters can typically only deflect within a single plane containing the direction of the external magnetic field. This difference allows the catheter of this application to achieve precise steering when facing vascular bifurcation in any direction in three-dimensional space, while existing solutions require rotating the entire magnetic field source device to change the orientation of the magnetic field plane when facing bifurcation that is not parallel to the magnetic field plane, which is complex to operate and has a slow response speed.

[0120] In addition to the aforementioned alternating configuration of axial and radial magnetization, the magnetic units of the magnetically controlled segment can also employ other magnetization configurations to adapt to different clinical needs. Specifically: In an optional embodiment, the magnetization directions of the four magnetic units are configured using a Halbach array. In this configuration, the magnetization directions of adjacent magnetic units are rotated by 90° sequentially, creating an asymmetric magnetic field distribution where the magnetic field is enhanced on one side and weakened on the other. This configuration makes the magnetically controlled segment more sensitive to external magnetic fields in a specific direction, suitable for clinical scenarios requiring frequent deflection within a primary plane (such as navigation along the ascending segment of the internal carotid artery in the sagittal plane). The Halbach array-configured magnetically controlled segment can deflect up to 180° in the primary deflection plane, but its deflection capability is weaker in the direction perpendicular to the primary deflection plane, making it suitable for cases where the vascular pathway is mainly located in a single plane.

[0121] In another alternative embodiment, the number of magnetic units is increased from 4 to 6, and correspondingly, the number of superelastic nickel-titanium alloy skeleton segments is increased from 3 to 5. Increasing the number of magnetic units improves the bending precision of the magnetically controlled segments—each magnetic unit has a smaller deflection angle but a smoother bending curve, allowing the catheter tip to travel more closely to the vessel centerline in tortuous vessels. The total length of the magnetically controlled segments in this 6-segment configuration is increased from approximately 8 mm in the 4-segment configuration to approximately 12 mm, suitable for feeding arterial pathways with relatively large vessel diameters (greater than 1.5 mm) and continuously varying bends. For peripheral vessels with extremely small vessel diameters (less than 1.0 mm), a 4-segment configuration is still recommended to control the total length of the magnetically controlled segments and avoid difficulties in bending excessively long magnetically controlled segments within narrow vessels.

[0122] The path planning algorithm of the control unit can automatically adjust the magnetic field control parameters according to the specific configuration scheme of the magnetic control segment (4-segment alternating type, 4-segment Halbach type, or 6-segment alternating type). After the operator selects the catheter model to be used during the system initialization phase, the control unit automatically loads the corresponding model's magnetic moment vector parameters and system matrix, without the need for manual configuration of the magnetic field control parameters.

[0123] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit described above can be implemented in hardware.

[0124] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A smart neurointerventional catheter system based on NdFeB permanent magnet guidance, characterized in that, include: The conduit has a magnetically controlled section at its front end, which includes multiple magnetic units arranged axially. Each magnetic unit is made of permanent magnet material and has an independent magnetization direction. The magnetic units are connected by flexible connectors to allow the magnetically controlled section to bend with multiple degrees of freedom. The catheter is provided with a drug injection channel, which passes through the magnetically controlled section and extends to the distal outlet of the catheter; An external magnetic field generator is used to generate an adjustable gradient magnetic field that acts on the magnetically controlled segment to drive the magnetically controlled segment to deflect and guide the catheter tip to change its direction of travel. The control unit, connected to the external magnetic field generator, is used to regulate the intensity and direction of the adjustable gradient magnetic field.

2. The system according to claim 1, characterized in that, The magnetic unit is a rare-earth permanent magnet, and the magnetization direction of each magnetic unit includes an alternating configuration of axial magnetization and radial magnetization, so as to generate a composite deflection torque under the action of the adjustable gradient magnetic field.

3. The system according to claim 2, characterized in that, The flexible connector is a superelastic alloy skeleton, and the bending radius of the magneto-controlled segment under the drive of the adjustable gradient magnetic field is less than or equal to a preset bending threshold.

4. The system according to claim 1, characterized in that, The distal outlet of the drug injection channel is provided with a micro-orifice injection structure, which includes multiple micro-orifices distributed at the tip of the catheter for injecting the embolic agent into the target area in a dispersed manner.

5. The system according to claim 4, characterized in that, It also includes a pressure sensor located in the injection channel, and the control unit adjusts the injection speed of the embolic agent through the injection channel according to the detection value of the pressure sensor.

6. The system according to claim 1, characterized in that, The control unit plans the catheter's travel path based on preoperative vascular imaging data and adjusts the parameters of the adjustable gradient magnetic field according to the real-time position information of the catheter to guide the catheter along the travel path.

7. The system according to claim 6, characterized in that, It also includes a display device for displaying a three-dimensional model of the blood vessel and the real-time position of the catheter within the blood vessel, and provides an interactive interface for path adjustment.

8. A combined embolization method based on an intelligent neurointerventional catheter system guided by NdFeB permanent magnets, characterized in that, The system applied to any one of claims 1 to 7 comprises: The catheter is inserted into the target vascular region via a vascular access route; An adjustable gradient magnetic field is generated by the external magnetic field generator to drive the magnetically controlled segment to deflect and guide the catheter along the vascular path to the target position. After the catheter reaches the target position, the parameters of the adjustable gradient magnetic field are adjusted to maintain the stability of the catheter position. An embolic agent is injected into the target location through the injection channel.

9. The method according to claim 8, characterized in that, Driving the magnetically controlled segment to deflect in order to guide the catheter along the vascular pathway to the target location includes: The target path is determined based on preoperative vascular imaging data, and the intensity and direction of the adjustable gradient magnetic field are adjusted in real time according to the curvature changes of the vascular path during the catheter's travel.

10. The method according to claim 8, characterized in that, Injecting an embolic agent into the target location via the injection channel includes: dynamically adjusting the injection rate of the embolic agent based on the pressure feedback signal within the injection channel to inhibit the reflux of the embolic agent into non-target vessels.

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