CN116818155A - High-sensitivity tip force sensor for interventional guide wire - Google Patents

Abstract

The invention provides a high-sensitivity tip force sensor for an interventional guide wire, which consists of an interventional 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 core and used for sensing the tip force sense, bragg gratings with different reflection wavelengths are carved on each core of the multi-core fiber, the bending response of the position can be enhanced through differential processing, the sensitivity of the tip force sense detection is improved, and meanwhile, the crosstalk of temperature and axial strain is eliminated. The thermal diffusion coupler can couple the multi-core optical fiber signals into a single-mode optical fiber, so that single-channel measurement is realized, and the integration level of the device is improved. The invention can realize the detection of the tip force sense of the interventional guide wire and has wide application prospect in the field of minimally invasive surgery robots.

Description

High-sensitivity tip force sensor for interventional guide wire

Field of the art

The invention relates to the field of medical robots, in particular to a high-sensitivity tip force sensor for an interventional guide wire.

(II) background art

Cardiovascular and cerebrovascular diseases include cardiovascular and cerebrovascular diseases, which generally refer to ischemic or hemorrhagic diseases of heart, brain and systemic tissues caused by hyperlipidemia, blood viscosity, atherosclerosis, hypertension, etc. The major cardiovascular diseases include atherosclerosis, thrombosis, aneurysms, arrhythmias, and vascular stenosis caused by plaque build-up. Plaque and blood clots can fall off and form a thrombus, leading to blockage in the arterial system, and thus to ischemia of tissue, causing serious conditions such as heart attacks or strokes. Aneurysmal disease is also a serious disease that can lead to serious bleeding and even death. In recent years, with the birth of interventional radiology and the continuous development of interventional radiology, minimally invasive interventional surgery (MIS) has been accepted more and more, and becomes a main means for treating intravascular diseases. MIS involves the use of long flexible surgical instruments that are inserted into the body through small incisions or natural tunnels to complete the procedure as safely and quickly as possible while minimizing damage to surrounding tissue. MIS may improve surgical safety, reduce surgical scarring, shorten recovery time and hospital stay, reduce postoperative complications and pain, and the like.

Catheters or guidewires are an indispensable tool for performing minimally invasive interventional procedures. The catheter or guidewire is introduced from the skin into the blood vessel and then directed to various focal sites in the cardiovascular system. Because conventional medical catheters or guidewires do not have the ability to advance and select directions, they are manually controlled by the surgeon to advance or retract during minimally invasive interventional procedures and are directed or tipped into the target vessel by way of proximal torsions. Since the blood vessels in the human body are tortuous, the forces and torques applied at the proximal end cannot be smoothly and completely transferred along the flexible catheter to the distal end. That is, there is no clear kinematic relationship between the proximal and distal ends, which introduces great uncertainty and surgical difficulty to their insertion and steering. Meanwhile, this way of manually navigating the guide wire is laborious and requires a lot of experience, and is usually performed under X-ray irradiation during surgery, even if thick protective clothing is worn, the hands and faces of medical staff are still inevitably irradiated, which will lead to a significant increase in the incidence of diseases such as cancer, cataract and the like. And like all minimally invasive interventional procedures, the lack of visual feedback of the contact of the guide wire with the blood vessel to the operator makes it difficult for the operator to perceive the contact of the guide wire with the blood vessel, which may cause unnecessary injury to the patient.

Patent CN114191082a proposes a device for clamping a guide wire and measuring the resistance of the guide wire of a vascular interventional operation robot, in which a guide wire axial resistance detection module is added, and the device is installed on a guide wire delivery module to detect the resistance of the guide wire in the advancing process. But it can only realize the detection of axial resistance, and the resistance that whole seal wire received when the measured when promoting, can't provide the accurate feedback of seal wire head end and vascular contact's resistance.

The elongate structure of the guide wire determines that the volume and mass of the sensor must be small enough and the internal application is such that it must be resistant to electromagnetic interference, which makes the fiber optic sensor the preferred sensor for measuring the force sense at the tip of the guide wire. Patent CN114152370a proposes a minimally invasive surgery tip puncture force sensor based on fiber light, which is characterized in that a fiber grating is placed between a sensor housing and a plane spring, and is axially deformed under the action of a puncture force, and measurement can be realized through the grating. The sensor can realize the measurement of the tip force sense, but can only measure one-dimensional axial force, and cannot realize the judgment of the direction of the tip stress.

(III) summary of the invention

The invention aims to provide a high-sensitivity tip force sensor for an interventional guide wire. Aiming at the problem that the current guide wire tip force sense measurement can not realize the measurement of direction and size at the same time, the utility model provides a tip force sense detection sensor which is improved by the structure of the guide wire and introduces a multi-core fiber grating. The sensor has the advantages of high sensitivity, compact structure, strong capability of eliminating cross talk and interference resistance, and the like, can effectively improve the safety of micro-interventional operation, ensure the safety of patients and increase the success rate of the operation.

The purpose of the invention is realized in the following way:

a high-sensitivity tip force sensor for an interventional guide wire consists of an interventional 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 thermal diffusion coupler is obtained by thermally diffusing the transition optical fiber and the multi-core optical fiber after welding, and can couple the single-mode optical fiber signal and the multi-core optical fiber signal to each other, so that the single-channel measurement of the whole sensor is realized, and the integration level of the device is improved. The transition fiber includes an intermediate core that mates with a single mode fiber and a plurality of cladding layers that mate with the multi-core fiber for thermal diffusion. One end of the transition optical fiber is welded with the single-mode optical fiber, the other end of the transition optical fiber is welded with the multi-core optical fiber, and the welding point of the transition optical fiber and the multi-core optical fiber is heated, so that the mode field of the transition optical fiber is matched with the single-mode optical fiber, and signal coupling is realized. The single-mode optical fiber is connected with the grating demodulator through the optical fiber movable connector.

The interventional guide wire comprises a push rod, a guide wire core, a core tip and a guide wire head end; the end of the guide wire head is connected with the pushing rod through the spring ring sheath, the guide wire head end comprises a cylindrical structure, the cylindrical structure is sleeved outside the tip of the core, and the force applied to the end of the guide wire head can be transmitted to the tip of the guide wire core. The core tip of the guide wire is made of elastic materials, the whole interventional guide wire is of a hollow structure, an optical fiber can be placed in the guide wire, the optical fiber is fixed at the core tip, the center of the section of the optical fiber coincides with the center of the section of the core of the guide wire, and the multi-core optical fiber and the core tip are combined into a cantilever structure.

The number of the fiber cores of the multi-core optical fiber is even, each pair of the fiber cores are distributed in a central symmetry mode relative to the geometric center of the optical fiber, and the materials used by each pair of the fiber cores are the same, namely the fiber cores have the same temperature response and strain response.

The grating is inscribed on a multicore fiber placed in the tip of the guidewire core. Bragg gratings with different reflection wavelengths are carved on each fiber core of the multi-core optical fiber, and wavelength signals reflected by each fiber core are not interfered with each other when single-channel measurement is used. The bending response at this location can be enhanced by differential processing, improving the sensitivity of tip force sensing detection, while eliminating cross-talk of temperature and axial strain.

The sensitivity enhancement is obtained by differential processing of grating signals on each pair of mutually symmetrical cores of the multi-core optical fiber. When the guide wire is subjected to a force, the force is transmitted to the core tip of the guide wire through the cylindrical structure of the end of the guide wire. The core tip is regarded as a cantilever beam, so that when the force is applied, the core tip bends, and the wavelength of the multi-core fiber grating arranged in the core tip is shifted. Since each pair of cores of a multi-core fiber is symmetrical about the center of the fiber, the wavelengths of the gratings on each pair of cores drift in opposite directions when bending occurs. The sensitivity of the sensor can be doubled by differential operation, so that the sensitivity is enhanced, and meanwhile, cross talk caused by temperature and the like is eliminated.

Compared with the prior art, the invention has the advantages that:

1. according to the guide wire tip force sensor, the guide wire core tip structure is modified, the multi-core fiber bragg grating is combined with the guide wire tip force sensor, and the identification of the stress direction is realized while the measurement of the guide wire tip force is realized.

2. In the guide wire tip force sensor, the force signal received by the guide wire head end is measured and converted into the multi-core fiber bragg grating signal for detection, and a thermal diffusion coupler is adopted to replace a fan-in fan-out device which is required to be used for detecting the multi-core fiber bragg grating signal at the present stage, so that the integration level of the device is improved.

3. The guide wire tip force sensor adopts the multi-core optical fibers with the fiber cores arranged in a central symmetry manner, and can eliminate crosstalk caused by temperature and the like through differential operation, thereby improving the accuracy of a measurement result and enhancing the sensitivity of the sensor.

(IV) description of the drawings

FIG. 1 is a schematic diagram of an interventional guidewire tip force sensor;

FIG. 2 is a schematic cross-sectional view of a guidewire core tip;

FIG. 3 is a schematic cross-sectional view of a multi-core optical fiber, (a) a four-core optical fiber (b) a six-core optical fiber;

FIG. 4 is a schematic diagram of a thermal diffusion coupler based on a four-core fiber;

FIG. 5 is a reflection spectrum of an interventional guidewire tip force sensor based on a four-core optical fiber;

FIG. 6 is a change in reflectance spectrum of a four-core fiber-based interventional guidewire tip force sensor when subjected to a force;

fig. 7 shows the relationship between the force applied to the guide wire tip and the wavelength shift of the multi-core fiber grating after the difference calculation in different directions, (a) x-direction core (b) y-direction core.

In the figure: 1-interventional guide wire, 1-1-pushing rod, 1-2-guide wire core, 1-3-guide wire core tip, 1-4-guide wire head end, 2-multicore fiber, 2-1-four-core fiber, 2-2-six-core fiber, 3-multicore fiber grating, 4-thermal diffusion coupler, 5-single mode fiber, 6-fiber movable connector, 7-grating demodulator, 8-computer, 9-transition fiber.

(fifth) detailed description of the invention

For the purpose of promoting an understanding of the principles and advantages of the invention, reference will now be made to the drawings in which there will be illustrated, by way of illustration, and not as an actual or complete description, the embodiments of the invention. All other embodiments, based on the described embodiments, which a person of ordinary skill in the art would obtain without making any inventive effort, are within the scope of the invention.

Taking the four-core optical fiber shown in fig. 3 (a) as an example, the invention discloses a high-sensitivity tip force sensor for an interventional guide wire, which is structurally shown in fig. 1 and comprises an interventional 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 thermal diffusion coupler is obtained by heating a welding part of the transition optical fiber and the four-core optical fiber, the transition optical fiber is a double-clad optical fiber, as shown in fig. 4, when the thermal diffusion coupler is heated, the doped elements in the optical fiber core can be diffused, so that the mode field of the optical fiber is changed, and when the doped elements in the transition optical fiber and the multi-core optical fiber are diffused to be matched with the mode field, the thermal diffusion coupler stops heating. Light exiting the single-mode fiber at this time is coupled into the four cores of the four-core fiber along the transition fiber via the thermal diffusion region. The four-core fiber used had a spacing of 65 microns between the two cores in the x-direction. The diameter of the inner cladding of the used transition fiber is 77 micrometers, and the coupling of the single-mode fiber and the four-core fiber can be realized when the transition fiber is heated for 150 minutes.

The interventional type guide wire consists of a push rod, a conical guide wire core, a core tip and a guide wire head end, wherein the guide wire head end is connected with the push rod through a spring ring sheath, a cylindrical structure is manufactured on the guide wire head end, and the guide wire end is sleeved outside the guide wire core tip. The core tip of the guide wire is made of elastic materials, the whole guide wire is of a hollow structure, the cross section of the guide wire is shown in fig. 2, the fiber is filled with colloid with the Young modulus similar to that of the core tip material after being put in, and the core tip of the guide wire after being filled with the colloid is of a cantilever structure. After the end of the yarn guiding head receives external resistance, the force is transmitted to the tip of the yarn guiding core through the cylindrical structure, so that the stress of each fiber core of the multi-core optical fiber in the tip of the yarn guiding core is changed.

In order to effectively distinguish stress changes of each fiber core when the single channel is used for multi-core fiber signal demodulation, a mode of core-by-core writing is adopted when the multi-core fiber is subjected to grating writing, so that four fiber cores of the four-core fiber have different Bragg grating reflection wavelengths. The spectrum measured by the single channel is shown in fig. 4, and the spectrum contains four reflection peaks with different wavelengths, corresponding to four cores of the four-core optical fiber.

The principle of using four-core fiber bragg grating to perform tip force sense measurement is as follows:

when the fiber in the tip of the guide wire core is bent due to the stress of the guide wire head end, the fiber core generates strain:

wherein ε is _c For bend induced core axial strain, R is the bend radius, C is the corresponding curvature, and d is the distance of the core from the bend neutral plane. As shown in FIG. 3 (a), four cores are located on the coordinate axis, and when the optical fiber is bent along a certain angle θ, the distance from each core to the neutral plane is

i is the fiber core number, r _i Is the distance from each core to the geometric center of the fiber. The stress to which each fiber core is subjected at this time is

When the grating is subjected to bending, axial strain and temperature, the reflection wavelength of the grating shifts by the following amount

Δλ _i ＝(K _εi ·Δε _i +K _Ti ·ΔT) (4)

Wherein K is _εi And K _Ti Representing the strain sensitivity and temperature sensitivity of each core. The four cores of the four-core optical fiber are distributed geometrically symmetrically, so that when the four-core optical fiber is bent, the two grating wavelength drift amounts in the x direction are the same, but the drift directions are opposite, as shown in fig. 6, the fiber core 1 and the fiber core 3 are two fiber cores in the x direction, and the fiber core 2 and the fiber core 4 are two fiber cores in the y direction.

Because the temperature sensitivity of the four fiber cores is the same, the temperature crosstalk can be eliminated by adopting a differential operation mode, the measurement accuracy is improved, and the measurement sensitivity is enhanced. Differential operation of two gratings on the same coordinate axis

It can be seen that the variation of the wavelength after the difference operation is 2 times that of a single grating, so that the sensitivity is also 2 times that of a single grating.

The bending of the optical fiber can be regarded as a vector with magnitude and direction, and the bending in any direction can be decomposed into x-direction and y-direction changes, so that the magnitude and direction of the bending can be obtained by measuring the grating change in the x-direction and the y-direction, and the magnitude and direction of the force applied to the end of the spinneret can be obtained.

When the sensor is used, the sensor is firstly calibrated, and the relation between the tip force sense received by the sensor and the central wavelength drift amount of the multi-core fiber bragg grating is obtained. FIG. 7 is a graph showing the force versus wavelength variation obtained by differentiating two gratings on the x-axis (a) and the y-axis (b) under different stress directions. When the wavelength difference in the two axial directions is detected, the magnitude and direction of the received force can be restored by the following formula

Wherein K is _F13 and K _F24 Sensitivity is obtained for calibration.

Claims (8)

1. A high-sensitivity tip force sensor for interventional guidewires, which consists of interventional guidewires, multi-core optical fibers, multi-core fiber gratings, thermal diffusion couplers, single-mode optical fibers, optical fiber movable connectors, and grating solutions. It consists of an adjustment instrument and a computer; the multi-core fiber grating is placed at the tip of the guide wire for sensing force at the tip; each core of the multi-core fiber is engraved with Bragg gratings of different reflection wavelengths, and the bending at this position can be enhanced through differential processing response, improving the sensitivity of tip force detection while eliminating the crosstalk of temperature and axial strain; the thermal diffusion coupler is obtained by welding the transition fiber and the multi-core fiber and then thermally diffusing it, which can couple the multi-core fiber signal to a single mode In optical fiber, single-channel measurement is realized. 2. A high-sensitivity tip force sensor for interventional guidewires according to claim 1, characterized in that: the transition optical fiber contains an intermediate core that matches the single-mode optical fiber and is used for thermal diffusion with the multi-core Optical fibers match multiple claddings. 3. A high-sensitivity tip force sensor for interventional guidewires according to claim 1, characterized in that: the multi-core fiber grating is fixed on the central axis of the core tip of the interventional guidewire, Together with the core tip, it forms a cantilever beam structure. 4. A high-sensitivity tip force sensor for an interventional guidewire according to claim 1, characterized in that: the interventional guidewire is a hollow structure, and the optical fiber can be placed in the hollow of the interventional guidewire. inside the hole. 5. A high-sensitivity tip force sensor for interventional guidewires according to claim 1, characterized in that: the core tip of the interventional guidewire is made of elastic material. 6. A high-sensitivity tip force sensor for an interventional guidewire according to claim 1, characterized in that: the head end of the interventional guidewire includes a cylindrical structure, which can The force exerted on the tip is transmitted to the tip of the guidewire core. 7. A high-sensitivity tip force sensor for interventional guidewires according to claim 1, characterized in that: the multi-core optical fiber contains an even number of fiber cores, and each pair of fiber cores is related to the fiber geometry. The centers are symmetrically distributed, and the materials used in each pair of cores are the same. 8. A high-sensitivity tip force sensor for interventional guidewires according to claim 1, characterized in that: the sensitivity enhancement is through the differential grating signals on each pair of mutually symmetrical cores of multi-core optical fibers. processed.