CN116808406A - Optical fiber interventional type guide wire capable of realizing multi-dimensional force measurement of tip - Google Patents

Abstract

The invention provides an optical fiber interventional guidewire that can realize tip multi-dimensional force measurement. It consists of an interventional guidewire, a multi-core optical fiber, a multi-core optical fiber grating, a thermal diffusion coupler, a single-mode optical fiber, an optical fiber movable connector, It consists of grating demodulator and computer. A multi-core fiber grating is placed at the tip of the core of the guide wire for sensing tip force. Bragg gratings with different reflection wavelengths are engraved on each fiber core at the same axial position of the multi-core fiber. The guide wire can be realized through the intermediate core reference. Simultaneous measurement of tip temperature and resistance. The thermal diffusion coupler can couple multi-core optical fiber signals into single-mode optical fibers, enabling single-channel measurement and improving device integration. The invention can realize the detection of multi-dimensional force at the tip of an interventional guide wire, and has broad application prospects in the field of minimally invasive surgical robots.

Description

A fiber optic interventional guidewire that enables cutting-edge multi-dimensional force measurement

(1) Technical field

The invention relates to the field of medical robots, and in particular to an optical fiber interventional guidewire that can realize cutting-edge multi-dimensional force measurement.

(2) Background technology

Peripheral artery disease is a common disease, affecting approximately 155 million people worldwide in 2015, with an increase of approximately 34.4% from 2005 to 2015. The minimally invasive surgery (MIS) required to treat this condition involves manually navigating thin metal wires (0.36 to 0.89 mm outer diameter), called "guidewires," through tortuous vascular dissection to reach blocked or diseased arteries. After the guidewire is inserted and navigated to the diseased artery, various catheters can be introduced over this guidewire to perform various tasks at the location of the diseased artery.

Since ordinary medical catheters or guidewires do not have the ability to advance forward and select directions, during minimally invasive interventional procedures, they are manually controlled by the surgeon to advance or retreat, and point or turn into the target blood vessel through proximal twisting. . Since the blood vessels in the human body are tortuous, the force and torque exerted at the proximal end cannot be smoothly and completely transmitted to the distal end along the flexible catheter. That is to say, there is no clear movement relationship between the proximal and distal ends, which brings great uncertainty and surgical difficulty to their insertion and steering. Therefore, there is a need to provide an interventional guidewire with force feedback function. When operating the surgical robot, the force acting on the tissue can be felt through the force sensor at the end of the guide wire, and then the information such as the compliance, hardness, texture and temperature of the tissue felt is fed back, allowing the doctor to get a true feeling of the tissue. , so as to make accurate judgments and operations.

Patent CN114191082A proposes a vascular interventional surgery robot guidewire clamping and guidewire resistance measuring device. A guidewire axial resistance detection module is added to the device, which will be installed on the guidewire delivery module to detect the guidewire during advancement. resistance. However, it can only detect axial resistance, and the measured resistance of the entire guidewire when pushed cannot provide accurate feedback on the resistance of the guidewire tip in contact with the blood vessel.

The slender structure of the guidewire determines that the volume and mass of the sensor must be small enough, and the method of application in the body makes it must be resistant to electromagnetic interference. This requirement makes fiber optic sensors the first choice for measuring guidewire tip force. Patent CN114152370A proposes a minimally invasive surgical tip puncture force sensor based on fiber optic light. By placing a fiber grating between the sensor housing and the plane spring, axial deformation is generated under the puncture force. Measurement can be achieved through the grating. . The sensor can measure the tip force, but it can only measure one-dimensional axial force and cannot determine the direction of the tip force.

(3) Contents of the invention

The object of the present invention is to provide an optical fiber interventional guidewire that can realize multi-dimensional force measurement at the tip. In order to solve the problem that the existing guide wire tip force measurement cannot realize the direction and size measurement and temperature detection at the same time, an interventional method is proposed to achieve the tip multi-dimensional force and temperature measurement by improving the structure of the guide wire and introducing multi-core fiber grating. guide wire. This guide wire has the advantages of compact structure, simultaneous measurement of temperature and contact force, and strong anti-interference ability. It can effectively improve the safety of micro-interventional surgery, ensure patient safety, and increase the success rate of surgery.

The purpose of the present invention is achieved as follows:

An optical fiber interventional guidewire that can realize cutting-edge multi-dimensional force measurement. It consists of an interventional guidewire, a multi-core optical fiber, a multi-core fiber grating, a thermal diffusion coupler, a single-mode optical fiber, an optical fiber movable connector, a grating demodulator and Computer composition.

The thermal diffusion coupler is obtained by heating multi-core optical fiber, and can couple the single-mode optical fiber signal and the signal of the multi-core optical fiber to each other, thereby realizing single-channel measurement of the entire sensor and improving the integration of the device. Multicore optical fiber contains a middle core and no less than three side cores. The middle core of the multi-core optical fiber is located at the geometric center of the optical fiber. Its size matches that of the single-mode optical fiber and is used for temperature measurement. The side core is used to detect the stress on the guide wire tip. The single-mode optical fiber is connected to the grating demodulator through the optical fiber movable connector.

The interventional guidewire includes a push rod, a guidewire core, a core tip, and a guidewire tip; the guidewire tip is connected to the guidewire core, and can transmit the force received by the guidewire tip to the guidewire core tip. The tip of the guide wire is connected to the push rod through a spring coil sheath. The entire interventional guidewire is a hollow structure, into which an optical fiber can be placed. The optical fiber is fixed at the tip of the core, and the center of the optical fiber cross-section coincides with the center of the guidewire core cross-section.

The grating is inscribed on a multi-core optical fiber placed within the tip of the guidewire core. Bragg gratings with different reflection wavelengths are engraved on each core of the multi-core fiber at the same axial position. When single-channel measurement is used, the wavelength signals reflected back by each core do not interfere with each other. The strain and temperature of each fiber core can be obtained through the sensitivity matrix, thereby obtaining the stress on the tip of the interventional guidewire.

When a force is applied to the guidewire, the force is transmitted through the guidewire tip to the core tip of the guidewire. The entire guidewire tip is regarded as a cantilever beam, so when force is applied, the core tip will bend, causing the wavelength of the multi-core fiber grating placed in the core tip to drift. The specific principles are as follows:

The Bragg grating reflection center wavelength λ _B is determined by the following formula:

λ _B =2n _eff Λ (1)

In the formula, Λ is the grating period, n _eff is the effective refractive index of the grating area.

According to photoelastic theory, the wavelength change caused by axial strain and temperature is:

In the formula: ε is the applied strain, P _i,j is the Pockels piezoelectric coefficient of the photoelastic tensor, ν is the Poisson's ratio, α is the thermal expansion coefficient of the optical fiber material; ΔT is the temperature change.

The center wavelength of the fiber grating is shifted due to modulation by external signals, and the wavelength change Δλ _B can be measured by demodulating it. Without considering temperature changes, equation (2) can be simplified to:

Here, P=n _eff [p ₁₂ -ν(P ₁₁ +P ₁₂ )]/2 is the effective elastic coefficient of the optical fiber.

Under pure bending conditions, for an elastic beam of circular cross-section, the following relationship exists between axial strain and curvature:

In formula (4), ε is the axial surface linear strain value of the fiber Bragg grating sensor sensing position, ρ is the curvature radius of the sensor sensing position, C is the corresponding curvature, and D is the distance from the sensor to the neutral plane. When D and C are given, the strain of the fiber grating can be found. It can be seen from formulas (3) and (4) that the strain is proportional to the center wavelength shift Δλ _B of the fiber grating, so the curvature C is proportional to Δλ _B. In this way, by monitoring the center wavelength shift Δλ _B of the fiber Bragg grating sensor, the change in the optical fiber curvature C can be obtained, and thus the stress on the optical fiber can be obtained.

Compared with the prior art, the advantages of the present invention are:

1. The guidewire tip force sensor of the present invention, by transforming the core tip structure of the guidewire and combining it with a multi-core fiber grating, can not only measure the force of the guidewire tip, but also realize the identification of the force direction. At the same time, the temperature detection is also realized.

2. In the guidewire tip force sensor of the present invention, the force signal measurement on the guidewire tip is converted into multi-core fiber grating signal detection, and a thermal diffusion coupler is used to replace the current multi-core fiber grating signal detection that must be used. Fan-in and fan-out devices improve device integration.

(4) Description of drawings

Figure 1 is a schematic structural diagram of an optical fiber interventional guidewire that realizes tip multi-dimensional force measurement;

Figure 2 is a schematic structural diagram of a thermal diffusion coupler;

Figure 3 is a schematic diagram of four-core optical fiber bending measurement;

Figure 4 shows the four-core fiber grating reflection spectrum measured in a single channel;

Figure 5 shows the relationship between the wavelength drift of the multi-core fiber grating due to the force exerted on the guidewire tip in different directions (a) Core 4-2, (b) Core 4-3, (c) Core 4-4;

In the picture: 1-interventional guide wire, 1-1-push rod, 1-2-guide wire core, 1-3-guide wire core tip, 1-4-guide wire tip, 2-multi-core optical fiber, 3-Multi-core fiber grating, 4-Thermal diffusion coupler, 5-Single mode fiber, 6-Fiber movable connector, 7-Grating demodulator, 8-Computer, 9-Thermal diffusion coupler.

(5) Specific implementation methods

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Embodiments. Based on the described embodiments, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Taking the four-core optical fiber shown in Figure 3 as an example, the present invention discloses an optical fiber interventional guidewire that can realize multi-dimensional force measurement at the tip. Its structure is shown in Figure 1. The interventional guidewire and multi-core optical fiber , multi-core fiber grating, thermal diffusion coupler, single-mode optical fiber, optical fiber movable connector, grating demodulator and computer.

The thermal diffusion coupler is obtained by heating the welding point of the four-core optical fiber. As shown in Figure 2, when heated, the doped elements in the optical fiber core will diffuse, causing the middle core signal of the four-core optical fiber to couple with the side core. When the coupling ratio When desired belg is reached, stop heating. At this time, the light emitted from the single-mode fiber will be coupled to the four cores of the four-core fiber along the middle core of the four-core fiber through the thermal diffusion area. The three side cores of the four-core fiber used are arranged at 120° intervals, and the core spacing is 35 microns. When heated for 100 minutes, the signal coupling between the middle core and the edge core of the four-core optical fiber can be achieved.

The interventional guidewire consists of a push rod, a tapered guidewire core, a core tip and a guidewire tip. The guidewire tip is connected to the push rod through a spring coil sheath, and the guidewire core tip is connected to the guidewire tip. The guide wire has a hollow structure as a whole. After the optical fiber is placed, it is filled with colloid with a Young's modulus similar to the core tip material to fix the optical fiber. The entire guide wire tip has a cantilever beam structure. When the guidewire tip encounters external resistance, the force will be transmitted to the guidewire core tip, causing the multi-core optical fiber in the guidewire core tip to bend, causing the grating reflection wavelength of each fiber core to drift.

In order to effectively distinguish the stress changes of each fiber core when using a single channel to demodulate multi-core fiber signals, a core-by-core writing method should be used when grating writing on multi-core fiber, so that the four-core fiber has four cores. with different Bragg grating reflection wavelengths. The spectrum measured through a single channel at this time is shown in Figure 4. The spectrum contains four reflection peaks with different wavelengths, corresponding to the four cores of the four-core optical fiber.

The principle of tip force measurement using the four-core fiber grating shown in Figure 3 is:

Four-core fiber is mainly composed of a middle core located in the center of the cladding and three side cores arranged in an equilateral triangle. When the optical fiber is bent with a radius of curvature ρ along the BB' axis, the distance from the core i to the neutral plane NN' can be obtained from the geometric relationship in Figure 3:

d _i =r _i sin(θ _b -π/2-θ _i ) (5)

Substituting equation (5) into equations (4) and (3), we can obtain the relationship between the grating center wavelength shift and the radius of curvature on the fiber core i:

In an actual grating bending sensing system, the grating center wavelength offset Δλ _i /λ _i can be obtained from experimental data. In this way, there are only three unknown quantities ρ, θ _b and θ _i in formula (6) (here, according to the four-core Fiber core arrangement, θ ₁ , θ ₂ and θ ₃ have a fixed positional relationship), so the grating center wavelength shift equation corresponding to the three cores is combined to obtain:

And there is a fixed positional relationship between θ ₁ , θ ₂ and θ ₃ :

By combining the grating center wavelength shift equation (formula (6)) corresponding to the three fiber cores and the fixed positional relationship of θ ₁ , θ ₂ and θ ₃ (formula (8)), ρ, θ _b and θ can be solved ₁ , θ ₂ and θ ₃ .

When the optical fiber is bent under force, the grating wavelength on it drifts. As shown in Figure 5, the drift directions and drift amounts of the three fiber cores are different. Therefore, when obtaining the grating wavelength change on the three edge cores, the above The bending size and direction of the four-core optical fiber can be derived through the formula, and the stress on the guide wire tip can be obtained.

Since the middle core of a four-core fiber is located in the geometric center, it will not be affected when the fiber is bent. The grating on it only responds to temperature. Therefore, by measuring the intermediate core grating, the temperature value of the guide wire tip can be obtained.

Claims (5)

1. An optical fiber interventional type guide wire capable of realizing multi-dimensional force measurement of a tip consists of an interventional type guide wire, a multi-core optical fiber grating, a thermal diffusion coupler, a single-mode optical fiber, an optical fiber movable connector, a grating demodulator and a computer; the multi-core fiber grating is arranged at the tip of the guide wire and used for sensing the tip force; bragg gratings with different reflection wavelengths are carved on each fiber core at the same axial position of the multi-core fiber, and the simultaneous measurement of the temperature and the resistance of the tip of the guide wire can be realized through the reference of the middle core; the thermal diffusion coupler can couple the multi-core optical fiber signals into a single-mode optical fiber, and single-channel measurement is realized.

2. The optical fiber interventional guide wire capable of realizing multi-dimensional force measurement of a tip according to claim 1, wherein the optical fiber interventional guide wire is characterized in that: the thermal diffusion coupler is obtained by heating the multi-core optical fiber.

3. The optical fiber interventional guide wire capable of realizing multi-dimensional force measurement of a tip according to claim 1, wherein the optical fiber interventional guide wire is characterized in that: the interventional guide wire is of a hollow structure, and the optical fiber can be placed in the hollow hole of the interventional guide wire.

4. The optical fiber interventional guide wire capable of realizing multi-dimensional force measurement of a tip according to claim 1, wherein the optical fiber interventional guide wire is characterized in that: the multi-core fiber grating is fixed on a central shaft of the tip of the interventional type guide wire core, and the tip of the guide wire core is connected with the tip of the guide wire.

5. The optical fiber interventional guide wire capable of realizing multi-dimensional force measurement of a tip according to claim 1, wherein the optical fiber interventional guide wire is characterized in that: the multi-core optical fiber comprises a middle core and at least three side cores.