CN115661347A - Three-dimensional reconstruction method of active shape sensing surgical probe of multi-core optical fiber - Google Patents
Three-dimensional reconstruction method of active shape sensing surgical probe of multi-core optical fiber Download PDFInfo
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- CN115661347A CN115661347A CN202211300790.6A CN202211300790A CN115661347A CN 115661347 A CN115661347 A CN 115661347A CN 202211300790 A CN202211300790 A CN 202211300790A CN 115661347 A CN115661347 A CN 115661347A
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Abstract
The invention provides a three-dimensional reconstruction method of an active shape sensing surgical probe of a multi-core optical fiber, which comprises the following steps: a. when the soft detection component deforms, acquiring the wavelength of the Bragg grating of each fiber core in the multi-core optical fiber; b. calibrating a wavelength-strain curve of each fiber core in the multi-core optical fiber, and calculating the strain of each fiber core according to the calibrated wavelength-strain curve; c. and d, performing curvature fitting through the bending curvature of each fiber core, and performing three-dimensional reconstruction through a Flenar frame. The invention combines the fiber grating sensing theory and the kinematics model, and utilizes the physical quantity information of the measuring strain of each point of the probe structure to fit and reconstruct the three-dimensional structure form of flexible deformation by embedding the multi-core fiber grating sensor in the probe, thereby monitoring and regulating the probe in real time and ensuring the smooth and successful operation.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a three-dimensional reconstruction method of an active shape sensing surgical probe of a multi-core optical fiber.
Background
Currently, the sensing measurement method of the medical probe mainly comprises visual and subjective tactile measurement and the like. However, the existing methods have problems that are difficult to solve due to the limitations of the probe body material and the application environment, such as: most physicians determine the pose of the probe based on the resistance felt through the probe, subject to technical principles and instrument size limitations. Moreover, because the probe body is soft and small, the traditional rigid sensor is difficult to integrate on the probe; the flexible electronic sensor is susceptible to electromagnetic interference, incompatible with a nuclear magnetic resonance guidance system, poor in calibration and repeatability and large in measurement error. Therefore, the existing sensing method and device do not realize accurate measurement of the probe and closed-loop control, which restricts the application of the technology in minimally invasive surgery.
In recent years, the optical fiber sensing technology has been developed rapidly, and the software structure measurement technology based on the optical fiber sensor has become the research and development direction of the precision measurement technology of the medical instrument. Different from the traditional sensing method, the optical fiber sensor utilizes optical signals transmitted by the optical fiber to carry out sensing measurement, has the advantages of good flexibility, small volume, light weight, strong anti-electromagnetic interference capability and the like, can be embedded into a probe to form a sensing network, measures parameters such as pose and the like, and realizes feedback closed-loop control. This provides a new approach to accurate sensing measurements of the probe. However, most of the existing optical fiber probe sensing technology researches use single-core optical fiber, so that the robustness is poor, the bendable deformation range is small, and the measurement requirement of bending deformation in all directions of probe interventional operations is difficult to meet
Disclosure of Invention
In order to solve the technical problems that an optical fiber probe in the prior art is poor in robustness, small in bendable deformation range and difficult to meet the measurement requirement of probe interventional surgery on each direction of bending deformation, the invention aims to provide a three-dimensional reconstruction method of an active shape sensing surgical probe of a multi-core optical fiber, and the three-dimensional reconstruction method comprises the following steps:
a. when the soft detection component deforms, acquiring the wavelength of the Bragg grating of each fiber core in the multi-core optical fiber;
b. calibrating a wavelength-strain curve of each fiber core in the multi-core optical fiber, and calculating the strain of each fiber core according to the calibrated wavelength-strain curve;
c. calculating a bending curvature of each core from the strain of each core, wherein each core bending curvature is calculated by:
k is the bending curvature of each fiber core, epsilon is the strain of each fiber core, and delta is the distance between the center of each fiber core of the bending section and the tangent plane of the central bending plane of the multi-core fiber when the multi-core fiber is bent;
d. curvature fitting is performed through the bending curvature of each fiber core, and three-dimensional reconstruction is performed through a Flenar frame.
In some preferred embodiments, the wavelength-strain curve of the multi-core fiber is calibrated as follows:
bending a multicore fiber and recording the bending strain epsilon of each fiber core 1 And Bragg grating wavelength λ 1 ；
The above process was repeated and the bending strain epsilon of each core was recorded 2 、ε 3 、…、ε n And Bragg grating wavelength λ 2 、λ 3 、…、λ n 、；
Wavelength-strain curves were plotted for each core: λ = a ∈ + b, where a, b are wavelength-strain curve parameters.
In some preferred embodiments, the distance between the center of each core of the bending section and the tangent plane of the central bending plane of the multicore fiber is a fixed value when the multicore fiber is bent.
In some preferred embodiments, the multicore fiber is bent such that the center of each core of the bend section is the same distance from the tangent plane of the central bending plane of the multicore fiber.
In some preferred embodiments, the multicore fiber is bent such that the center of each core of the bend section is at a different distance from the tangent plane of the central bending plane of the multicore fiber.
The invention provides a three-dimensional reconstruction method of an active shape sensing operation probe of a multi-core optical fiber, which combines an optical fiber grating sensing theory and a kinematic model, utilizes the physical quantity information of the measurement strain of each point of a probe structure to fit and reconstruct a flexibly deformed three-dimensional structure form by embedding a multi-core optical fiber grating sensor in the probe, monitors and regulates the probe in real time, and ensures the smooth and successful operation.
According to the three-dimensional reconstruction method of the multi-core optical fiber active shape sensing surgical probe, the optical fiber sensor is embedded into the probe, the wavelength change of the grating in the probe is sensed sensitively and quickly, the three-dimensional shape of the probe can be obtained simply and easily by using the three-dimensional shape reconstruction method, and the state of the probe is adjusted in real time. The system is simple and easy to realize, and is very suitable for being applied in interventional operations.
The three-dimensional reconstruction method of the active shape sensing surgical probe of the multi-core fiber provided by the invention can sense information such as strain displacement and the like generated by structural deformation of the probe sensitively and quickly by using the body-implanted fiber grating sensor, thereby realizing the three-dimensional shape reconstruction of the probe. The invention has simple structure and high stability, and can realize the shape reconstruction of different structures according to requirements.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 schematically shows a structural diagram of an active shape sensing surgical probe based on a multi-core optical fiber according to an embodiment of the present invention.
FIG. 2 is a schematic structural diagram of a multi-core optical fiber embedded in a probe software detection component according to an embodiment of the present invention.
FIG. 3 shows a schematic representation of the bending of a multicore fiber in one embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating a curved cross-section of a bend in a multi-core optical fiber according to an embodiment of the present invention.
FIG. 5 shows a schematic representation of coordinate transformation using a Flrenaner frame in one embodiment of the invention.
Detailed Description
In order to make the above and other features and advantages of the present invention more apparent, the present invention is further described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting.
In order to solve the technical problems that the optical fiber probe in the prior art has poor robustness and a small bendable deformation range and is difficult to meet the measurement requirement of the probe interventional surgery on the bending deformation in all directions, fig. 1 shows a schematic structural diagram of an active shape sensing surgical probe based on a multi-core optical fiber in one embodiment of the invention, and fig. 2 shows a schematic structural diagram of a multi-core optical fiber embedded in a probe software detection component in one embodiment of the invention.
According to an embodiment of the present invention, an active shape sensing surgical probe 1 based on a multi-core optical fiber is provided, comprising a soft body probe component 101. The multi-core optical fiber 2 is arranged in the soft detection component 101, the multi-core optical fiber comprises a plurality of fiber cores, the plurality of fiber cores surround the central shaft of the multi-core optical fiber 2, the fiber cores are uniformly arrayed in the multi-core optical fiber 2, and a plurality of Bragg gratings (FBGs) are arrayed on each fiber core at equal intervals.
In the embodiment, three cores are disposed in the multicore fiber 2, and the first core 201, the second core 202, and the third core 203 are disposed in the multicore fiber 2. The first fiber core 201, the second fiber core 202 and the third fiber core 203 surround the central axis of the multicore fiber 2, and are uniformly arrayed in the multicore fiber 2, 4 bragg gratings 2011 are arrayed on the first fiber core 201 at equal intervals, 4 bragg gratings 2021 are arrayed on the second fiber core 202 at equal intervals, and 4 bragg gratings 2031 are arrayed on the third fiber core 203 at equal intervals.
According to an embodiment of the present invention, the bragg grating of each core is aligned with the bragg grating of an adjacent core. Specifically, the 4 bragg gratings 2011 of the first core 201 are aligned with the 4 bragg gratings 2021 of the second core 202, respectively. The 4 bragg gratings 2021 of the second core 202 are respectively aligned with the 4 bragg gratings 2031 on the third core 203. The 4 bragg gratings 2031 on the third core 203 are aligned with the 4 bragg gratings 2011 of the first core 201, respectively.
In some preferred embodiments, after the bragg grating is written on each fiber core of the multi-core optical fiber by the ultraviolet exposure method, the probe is implanted into the soft detection component 101. Because the pretightening force and the annealing time applied in the Bragg grating writing process are slightly different, the center wavelength of the Bragg grating is selected to be 1547.6037nm-1547.5910nm, the length of a grating region is 10mm, the reflectivity is 90 percent, and the side mode suppression ratio is 20dB.
According to the embodiment of the invention, when the soft detection component 101 deforms, the multi-core optical fiber 2 implanted in the soft detection component 101 is subjected to bending deformation, so that each fiber core of the multi-core optical fiber 2 is subjected to bending deformation, and three-dimensional reconstruction is carried out by acquiring the strain of each fiber core.
In a specific embodiment, according to an embodiment of the present invention, a three-dimensional reconstruction method for an active shape sensing surgical probe of a multicore fiber includes:
s1, when the soft detection component 101 deforms, the wavelength of the Bragg grating of each fiber core in the multi-core optical fiber is acquired.
When incident light of a certain frequency passes through a Bragg grating (FBG), it will have a wavelength of λ B Nearby light waves are reflected back and light waves of the remaining wavelengths will be transmitted through the bragg grating (FBG). Lambda B For the wavelength of a bragg grating (FBG), the following formula is satisfied:
λ B ＝2n eff ·Λ
wherein n is eff Lambda is the effective index of the fiber and lambda is the grating period.
And S2, calibrating a wavelength-strain curve of each fiber core in the multi-core optical fiber, and calculating the strain of each fiber core according to the calibrated wavelength-strain curve.
The wavelength of Bragg grating is linearly related to strain B And (5) drawing a wavelength-strain curve in a calibration mode to obtain wavelength-strain curve parameters a and b.
The wavelength-strain curve of the bragg grating of the multi-core fiber 2 is calibrated according to the following method:
bending the multicore fibers 2 and recording the bending strain epsilon of each core 1 And Bragg grating wavelength λ 1 。
The above process was repeated and the bending strain ε of each core was recorded 2 、ε 3 、…、ε n And Bragg grating wavelength λ 2 、λ 3 、…、λ n 。
Wavelength-strain curves were plotted for each core: lambda [ alpha ] B And = a epsilon + b, wherein a and b are wavelength-strain curve parameters.
S3, calculating the bending curvature of each fiber core through the strain of each fiber core, wherein the bending curvature of each fiber core is calculated in the following mode:
wherein k is the bending curvature of each fiber core, epsilon is the strain of each fiber core, and delta is the distance between the center of each fiber core of the bending section and the bending plane of the center of the multi-core fiber when the multi-core fiber is bent.
As shown in fig. 3, a schematic diagram of the bending of the multi-core fiber in one embodiment of the present invention, and a schematic diagram of the bending section of the multi-core sub-fiber in one embodiment of the present invention, which is shown in fig. 4, take the first core 201 of the multi-core fiber 2 as an example, when the multi-core fiber 2 is subjected to bending deformation, the first core 201 is also subjected to bending deformation, and the bending section of the multi-core fiber 2 is cut, so that the center of the first core 201 of the multi-core fiber 2 and the tangent plane 205 of the central bending plane 204 of the multi-core fiber form a distance δ in the bending section 200.
The bending strain of the first core 201 satisfies:
the above equation is converted to a curvature-strain relationship:
the multi-core fiber center curved surface 204 is a curved surface on which the center axis of the multi-core fiber 2 is located when the multi-core fiber 2 is bent. The curved cross-section 200 is perpendicular to a tangent plane 205 of the central curved facet 204 of the multi-core optical fiber when the curved cross-section 200 is taken from the curved section.
In the same manner, the bending curvature of each core can be obtained by measuring the bending strain of each core, and the bending curvature is obtained from the wavelength-strain curve of the bragg grating by measuring the wavelength of the bragg grating.
In a specific embodiment, the difference between the distance δ between the center of each core of the curved cross-section 200 and the tangent plane 205 of the central curved surface 204 of the multi-core fiber is small when the bending deformation is performed in different directions. The change in the distance δ between the center of each core of the curved cross-section 200 and the tangent plane 205 of the central curved surface 204 of the multicore fiber due to the bending deformation in different directions is ignored, and the distance δ between the center of each core of the curved cross-section 200 and the tangent plane 205 of the central curved surface 204 of the multicore fiber is set to a fixed value as a parameter of the multicore fiber 2.
Therefore, by measuring the wavelength of the Bragg grating, the strain capacity is obtained from the wavelength-strain curve of the Bragg grating, and then the bending curvature of each fiber core is obtained according to the curvature-strain relation.
In some preferred embodiments, the center of each core of the curved cross-section 200 is located at the same distance from the tangent plane 205 of the central curved surface 204 of the multicore fiber when the multicore fiber is bent. That is, in the curved cross-section 200, the distances δ between the centers of the first core 201, the second core 202, and the third core 203 and the tangent plane 205 of the central curved surface 204 of the multicore fiber are the same fixed values as parameters of the multicore fiber 2.
In some preferred embodiments, the center of each core of the curved cross-section 200 is at a different distance from the tangent plane 205 of the central curved surface 204 of the multicore fiber when the multicore fiber is bent. That is, in the curved cross-section 200, the distances δ between the centers of the first core 201, the second core 202, and the third core 203 and the tangent plane 205 of the central curved surface 204 of the multicore fiber are different. The distance between the center of each core of the curved cross-section 200 and the tangent plane 205 of the central curved surface 204 of the multicore fiber is different, and the distance between the center of each core and the tangent plane 205 of the central curved surface 204 of the multicore fiber is three different fixed values as parameters of the multicore fiber 2.
And S4, curvature fitting is carried out through the bending curvature of each fiber core, and three-dimensional reconstruction is carried out through a Ferner standard frame.
According to the embodiment of the present invention, the bending curvature of each core is fitted by selecting a suitable fitting manner by those skilled in the art, such as but not limited to cubic spline interpolation, least square fitting, and the present invention is not limited in detail.
For three-dimensional reconstruction, according to an embodiment of the present invention, three-dimensional reconstruction is performed by a Frenet frame (Frenet frame). Referring to fig. 5, a schematic diagram of coordinate transformation using a flener scale frame according to an embodiment of the present invention, in one embodiment, the flener scale frame coordinate change is calculated as follows:
local coordinate system { x i-1 ,z i-1 To a local coordinate system x i ,z i The change matrix of
Is composed of
Consider raster point Oi +1 as being in the local coordinate system { x } i ,z i In the equation, the geometric relationship is known, and the point Oi +1 is relative to the local coordinate system { x } i ,z i Coordinates of } c
Comprises the following steps:
finally through homogeneous transformation
To calculate the position of the origin in the global coordinate system
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (5)
1. A method for three-dimensional reconstruction of an active shape-aware surgical probe with multiple core fibers, the method comprising:
a. when the soft detection component deforms, acquiring the wavelength of the Bragg grating of each fiber core in the multi-core optical fiber;
b. calibrating a wavelength-strain curve of each fiber core in the multi-core fiber, and calculating the strain of each fiber core through the calibrated wavelength-strain curve;
c. calculating a bending curvature of each core from the strain of each core, wherein each core bending curvature is calculated by:
wherein k is the bending curvature of each fiber core, epsilon is the strain of each fiber core, and delta is the distance between the center of each fiber core of the bending section and the tangent plane of the central bending plane of the multi-core fiber when the multi-core fiber is bent;
d. curvature fitting is performed through the bending curvature of each fiber core, and three-dimensional reconstruction is performed through a Flenar frame.
2. The three-dimensional reconstruction method of claim 1, wherein the wavelength-strain curve of the multi-core fiber is calibrated according to the following method:
bending the multicore fibers and recording the bending strain epsilon of each fiber core 1 And Bragg grating wavelength λ 1 ；
The above process was repeated and the bending strain epsilon of each core was recorded 2 、ε 3 、…、ε n And Bragg grating wavelength λ 2 、λ 3 、…、λ n 、；
Wavelength-strain curves were plotted for each core: λ = ε + b, where a, b are the wavelength-strain curve parameters.
3. The three-dimensional reconstruction method as claimed in claim 1, wherein a distance between a center of each core of the curved cross-section and a tangent plane of the central curved plane of the multicore fiber is a fixed value when the multicore fiber is curved.
4. The three-dimensional reconstruction method as claimed in claim 1, wherein the center of each core of the curved cross-section is located at the same distance from the tangent plane of the central curved surface of the multicore fiber when the multicore fiber is bent.
5. The three-dimensional reconstruction method as claimed in claim 1, wherein the multicore fiber is bent such that the center of each core of the bent section is spaced apart from the tangent plane of the central bending plane of the multicore fiber.
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