Optical Fiber Shape Sensing With Twist-Strain Correction
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Solution Overview
Problem
Existing optical fiber-based shape sensing methods struggle to distinguish between twist-induced and bend-induced strains, leading to inaccurate shape reconstruction of flexible medical instruments during minimally invasive surgeries, which rely heavily on fluoroscopic imaging and expose patients and operators to harmful radiation.
Innovation Solution
A method and system for shape sensing an optical fiber embedded in interventional devices, utilizing an outer fiber core disposed at a non-zero radial distance from the center axis, with strain sensors to generate data, corrected by a strain correction term derived from additional information sources like fluoroscopy, electromagnetic tracking, or preoperative imaging, to compensate for twist-induced strains and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If optical fiber-based shape sensing is used to avoid fluoroscopic radiation, then patient and operator safety is improved, but measurement precision deteriorates due to inability to distinguish twist-induced strain from bend-induced strain
Solution Approach 1:
The optical fiber is divided into multiple discrete sensing segments along its length, with each segment containing strain sensors that independently measure local deformation. This segmentation allows the system to reconstruct the overall shape by combining measurements from multiple points, improving accuracy while maintaining radiation-free operation.
Solution Approach 2:
The patent introduces an intermediary computational model that processes raw strain measurements and distinguishes between twist-induced and bend-induced strains through mathematical analysis. This intermediary layer transforms ambiguous strain data into accurate shape information without requiring additional physical sensors or radiation exposure.
2Device complexity
If traditional strain sensing methods are used in optical fibers, then device complexity is reduced, but measurement precision deteriorates due to dynamical twist interference
Solution Approach 1:
The patent transitions from one-dimensional strain measurement along the fiber axis to three-dimensional shape reconstruction by incorporating spatial coordinates and orientation information. This dimensional expansion allows the system to differentiate between twist and bend components that project differently in three-dimensional space, improving measurement precision without significantly increasing device complexity.
Solution Approach 2:
The system changes the parameters being measured from simple strain magnitude to strain components resolved in multiple directions. By measuring strain in different orientations and using these multi-parameter measurements, the system can mathematically separate twist-induced strain from bend-induced strain, improving accuracy while maintaining relatively simple sensor implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy of shape reconstruction by minimizing errors due to twist, reducing reliance on harmful radiation, and enabling precise shape estimation of flexible medical instruments during surgeries.
Implementation Method 1
an optical fiber-based shape sensing technique relies on measuring the mechanical strain in the optical fiber
Implementation Method 2
optical fiber comprises at least one outer fiber core disposed at a non-zero radial distance from a longitudinal center axis
Data Source
AI summary
A method for shape sensing an optical fiber embedded within an interventional device includes obtaining, from at least one strain sensor, strain-based shape sensing data of the optical fiber. The strain-based shape sensing data is corrected with a strain correction term. A strain-based reconstructed shape of the optical fiber is calculated based on the corrected data. The strain-based reconstructed shape of the optical fiber is mapped in a coordinate system. The strain correction term is derived from comparing a previous reconstructed shape of the optical fiber with additional information about the shape obtained from an additional source other than the strain sensor. Following mapping the reconstructed shape in the coordinate system, the method checks for a new set of additional information related to the shape and updates the correction term based on a comparison of the mapped shape with a reconstructed shape based on the new set of information.