Active guidewire and design method

Abstract

The application discloses an active guide wire, which comprises a front end guide wire and a rear end handle, wherein the front end guide wire comprises a central framework, a spring sheath sleeved at the front end of the central framework, and at least one shape memory alloy arranged on the central framework and located behind the spring sheath; the shape memory alloy is wound on the central framework through a micro capillary tube; the shape memory alloy is arranged on two sides or one side of the central framework in an even interval along the axial direction of the central framework; and one end of each shape memory alloy is connected with the power supply of the rear end handle through a wire. The front end of the guide wire is bent by the contraction of the SMA material under the action of electricity, so as to adapt to the complex blood vessel environment in the operation process; compared with the existing passive guide wire, the active guide wire can improve the operation efficiency, reduce the damage to the blood vessel, has higher flexibility and stronger practicability.

Description

Technical Field

[0001] This invention belongs to the field of medical guidewire technology, specifically relating to an active guidewire and its design method. Background Technology

[0002] To achieve active medical guidewires, many new driving methods have been proposed to actively control the bending of the guidewire, such as SMA driving, electroactive polymer driving, pressure driving, integrated fine-tuning driving, rope driving, and magnetic driving. Among them, the method of using SMA, especially Ni-Ti based SMA, for driving is widely used in vascular guidewire robots due to its good biocompatibility, corrosion resistance, and thermal processing performance.

[0003] Existing guidewires using SMA material for active bending often have large diameters and are difficult to standardize and modularize, making them incompatible with other medical devices. Therefore, they are difficult to apply in minimally invasive clinical surgery. Compared to the cardiovascular system, the small size and tortuous nature of cerebral blood vessels necessitate more effective treatment methods and guidewires with even smaller diameters. Interventional vascular surgery is an effective treatment for cerebrovascular diseases, but it heavily relies on the surgeon's skill and experience. A crucial step in this procedure is navigation to the pathological location. Current techniques require the simultaneous insertion of several different guidewires and catheters to reach the treatment area. Navigation is relatively simple in some vessels related to the femoral artery, but most vessels are much more complex. These complex vessels often have significant tortuosity, making navigation almost impossible. Furthermore, friction and loss of control during manipulation can easily occur, all of which seriously affect the safety, effectiveness, and timeliness of interventional surgery. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an active guidewire with variable curvature and its design method.

[0005] To address the shortcomings of existing technologies, this invention designs an active guidewire, comprising a front guidewire and a rear handle. The front guidewire includes a central skeleton, a spring sheath fitted at the front end of the central skeleton, and at least one shape memory alloy arranged on the central skeleton and located behind the spring sheath. The shape memory alloy is wound around the central skeleton through a microcapillary tube. The shape memory alloy is evenly spaced on both sides or one side along the axial direction of the central skeleton. One end of each shape memory alloy is connected to the power supply of the rear handle through a wire.

[0006] Furthermore, the top surface of the spring sheath is a soft spherical surface.

[0007] Furthermore, the front end of the central skeleton is a proximal push section with a gradually decreasing diameter, and the area between the top of the proximal push section and the top of the spring sheath serves as a transition section.

[0008] Furthermore, the outer edge of the central skeleton is coated with an insulating coating.

[0009] Furthermore, the front guidewire is also fitted with a TPU sheath.

[0010] A design method for an active guidewire as described above is also provided, characterized in that:

[0011] Calculate the length L of the shape memory alloy based on the bending angle θ:

[0012]

[0013] Where: L is the length of the shape memory alloy before shrinkage upon energization; i is the moment of inertia of the central skeleton; α is the shrinkage rate of the SMA; E is the moment of inertia of the central skeleton; F is the maximum load force of the SMA;

[0014] The relationship between the maximum load force F of the SMA and the current I is as follows:

[0015]

[0016] Where A1, A2, A2, B1, B2, and B3 are all constants;

[0017] F0 is the calculated load force of the SMA; k is a constant; e is an exponent; t is the energizing time; R is the internal resistance of the SMA; h is the heat conduction parameter; A s The heat exchange area is πdL + πd 2 / 2, d is the diameter of the SMA; m is the mass of the SMA; c is the specific heat capacity of the SMA;

[0018] The SMA load capacity F0 is calculated based on the magnitude of the current and time using the above formula. If the calculated SMA load capacity F0 is greater than the recommended SMA load capacity F corresponding to the SMA diameter d, then the designed current I and time t are appropriate.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The active guidewire of the present invention uses SMA material to generate electricity and contract to drive the tip of the guidewire to bend, so as to adapt to the complex vascular environment during the operation. Compared with the existing passive guidewire, it can improve the efficiency of the operation, reduce damage to the blood vessels, and has greater flexibility and practicality. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the active guidewire structure of the present invention;

[0021] Figure 2 for Figure 1 Schematic diagram of the mid-front guidewire structure;

[0022] Figure 3 for Figure 2 A schematic diagram of the front end. Detailed Implementation

[0023] The following reference Figure 1 The present invention will be further described in detail with reference to specific embodiments to facilitate a clearer understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0024] The active guidewire includes a front guidewire 2 and a rear handle 1. The front guidewire 2 includes a central skeleton 3, a spring sleeve 4 fitted on the front end of the central skeleton 3, and at least one shape memory alloy 5 arranged on the central skeleton 3 and located behind the spring sleeve 4. The top surface of the spring sleeve 4 is a soft spherical surface 7. The shape memory alloy 5 (SMA) is wound on the central skeleton 3 through a microcapillary tube. The shape memory alloy 5 is evenly spaced on both sides or one side along the axial direction of the central skeleton 3. One end of each shape memory alloy 5 is connected to the power supply of the rear handle 1 through a wire.

[0025] In this embodiment, combined with Figure 3 The front end of the central skeleton 3 shown is a proximal push section 6 with a gradually decreasing diameter, and the top of the proximal push section 6 and the top of the spring sheath 4 serve as a transition section 8. In addition, the outer edge of the central skeleton is coated with an insulating coating, and the front guide wire is also fitted with a TPU (thermoplastic polyurethane elastomer) sheath.

[0026] The transition section serves as a transition, and its length determines the support and compliance of the front guidewire. There is no push rod in the transition section, which enhances the maneuverability and directional control of the front guidewire head. The diameter of the front push rod section of the central skeleton gradually decreases, which can control the compliance and tracking ability of the guidewire.

[0027] Calculate the length L of the shape memory alloy based on the bending angle θ:

[0028]

[0029] Where: L is the length of the shape memory alloy before shrinkage upon energization, in mm; i is the moment of inertia of the central skeleton (ignoring the SMA and the front spring), with a value of 0.7845 × 10⁻⁶. -3 mm 4 α is the shrinkage rate of the SMA; E is the moment of inertia of the central skeleton, which is taken as 193 kN / mm² since the material is 304 stainless steel. 2 F represents the maximum load capacity of the SMA. Recommended maximum load capacity values ​​for SMAs of different diameters are shown in Table 1.

[0030] Table 1

[0031]

[0032] The relationship between the maximum load force F of the SMA and the current I is as follows:

[0033]

[0034] Where A1, A2, A2, B1, B2, and B3 are all constants;

[0035] F0 is the calculated load capacity of the SMA; k is a constant; e is an exponent; t is the energizing time, s; R is the internal resistance of the SMA, Ω; h is the thermal conductivity parameter, W / (m²). 2 ·K); A s The heat exchange area is πdL + πd 2 / 2, d is the diameter of the SMA; m is the mass of the SMA, kg; c is the specific heat capacity of the SMA, J / kg·K.

[0036] The SMA load capacity F0 is calculated based on the magnitude of the current and time using the above formula. If the calculated SMA load capacity F0 is greater than the recommended SMA load capacity F corresponding to the SMA diameter d, then the designed current I and time t are appropriate.

[0037] In this embodiment, the central skeleton is made of 304 stainless steel with a diameter of 0.3556 mm; the SMA has a diameter of 0.2 mm; the two are connected in parallel by a microcapsule with an inner diameter of 0.7 mm and a wall thickness of 0.05 mm. Therefore, the overall diameter of the guidewire is relatively small, making it suitable for different application scenarios.

[0038] This invention utilizes a variable curvature, actively bending vascular guidewire robot driven by a micro-motor (SMA) to assist medical personnel in interventional procedures. The guidewire diameter is controlled at approximately 0.035 inches (0.889 mm), allowing it to be used in conjunction with existing standard-sized instruments, increasing its versatility. Active bending (with overall insulation) can be achieved by applying electricity to the guidewire tip. Its excellent biocompatibility and small size enable it to handle complex vascular environments, thereby reducing the workload of medical personnel, shortening interventional procedure time, improving the safety and stability of vascular interventional procedures, and reducing surgical difficulty. This is of great significance for the treatment of cerebrovascular diseases in my country.

Claims

1. An active guidewire, characterized by: The front-end guide wire (2) comprises a center skeleton (3), a spring sheath (4) sleeved on the front end of the center skeleton (3), and at least one shape memory alloy (5) arranged on the center skeleton (3) and located behind the spring sheath (4), the shape memory alloy (5) is wound on the center skeleton (3) through a micro capillary, the shape memory alloy (5) is uniformly arranged on both sides or one side along the axial direction of the center skeleton (3), one end of each shape memory alloy (5) is connected with the power supply of the rear-end handle (1) through a wire; the front end of the center skeleton (3) is a proximal pushing section with gradually reduced diameter, the top end of the proximal pushing section to the top end of the spring sheath serves as a transition section; the outer edge surface of the center skeleton (3) is coated with an insulating coating.

2. The active guide wire of claim 1, wherein: The top end surface of the spring sheath (4) is a soft spherical surface.

3. The active guide wire of claim 1, wherein: The front-end guide wire (2) is further sleeved with a TPU sheath.

4. A design method of the active guide wire according to claim 1, characterized in that: The length L of the shape memory alloy is calculated according to the bending angle θ of the shape memory alloy: Wherein: L is the length of the shape memory alloy before power supply contraction; i is the moment of inertia of the center skeleton; α is the contraction rate of the SMA; E is the elastic modulus of the center skeleton; F is the maximum load of the SMA; The relationship between the maximum load F of the SMA and the current I is as follows: Wherein, A1, A2, A3, B1, B2, B3 are constants; F0 is the calculated SMA load force; k is a constant; e is an exponent; t is the energization time; R is the internal resistance of the SMA; h is the heat transfer parameter; A s is the heat exchange area, i.e. πdL + πd 2 / 2, d is the SMA diameter; m is the mass of the SMA; c is the specific heat capacity of the SMA; The calculated SMA load F0 is obtained according to the size and time of the current based on the above relationship, if the calculated SMA load F0 is greater than the recommended value of the SMA load F corresponding to the SMA diameter d, then the designed current I and time t are appropriate.

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