Optical Shape Sensing Fiber for Medical Instrument Tip Tracking
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Solution Overview
Problem
Current optical shape sensing technologies for medical instruments face challenges in accurately tracking the tip and shape due to backscatter interference, error-prone mounting on dynamic devices, and inability to account for deformation in continuum robots, leading to signal corruption and measurement errors.
Innovation Solution
The implementation of fiber attachment configurations with predetermined geometries, such as patterned rosettes or helical windings, along with an optical interrogation console and optional EM tracking, allows for error characterization and calibration, eliminating backscatter and enabling accurate tip location and shape measurement through forward and return path optical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber optic Bragg grating sensors are used for shape sensing, then measurement capability is provided, but backscatter interference at the fiber tip causes signal corruption and prevents tracking up to the very tip
Solution Approach 1:
The patent extracts and removes the harmful backscatter signal from the measurement system by using optical circulators and isolators to separate the forward and backward propagating light paths, eliminating the interference that prevents tip tracking
Solution Approach 2:
The patent introduces intermediary optical components (circulators, isolators, and reference gratings) that mediate between the light source and the sensing gratings, enabling the system to distinguish between useful reflection signals and harmful backscatter interference
2Ease of manufacture
If conventional fiber attachment methods are used on dynamic devices, then mounting is simplified, but errors are not compensated and position reading accuracy deteriorates
Solution Approach 1:
The patent performs preliminary calibration by attaching the fiber to a calibration object with known geometry and characteristics, storing this calibration data for later use in compensating measurement errors during actual dynamic operation
Solution Approach 2:
The patent implements feedback mechanisms where calibration data from known geometries is continuously referenced during operation to compensate for mounting errors and maintain position reading accuracy despite device dynamics
3Stability of the object's composition
If fiber is anchored at joints in rigid robots to avoid buckling, then structural stability is improved, but axial strain and excess force damage the fiber
Solution Approach 1:
The patent applies different attachment strategies at different locations: the fiber is loosely routed through joint areas to avoid buckling and mechanical damage, while maintaining sufficient contact to track the overall instrument shape, creating local variations in attachment quality
4Object-affected harmful factors
If index matching gel is used to reduce backreflection, then backscatter effects are partially reduced, but manufacturing complexity increases and the solution is only partial
Solution Approach 1:
The patent replaces the mechanical/chemical approach of index matching gel with an optical system using circulators and isolators that actively manage light paths, providing more complete backscatter elimination without the limitations of refractive index matching
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
This approach enhances measurement robustness and performance by providing real-time navigation and tracking improvements, reducing errors and collisions, and enabling precise shape sensing even in highly dynamic medical instruments.
Implementation Method 1
One such approach is to use Rayleigh scatter in a standard single-mode communications fiber. Rayleigh scatter occurs as a result of random fluctuations of the index of refraction in the fiber core.
Implementation Method 2
A fundamental principle behind the operation of a fiber Bragg grating (FBG) is Fresnel reflection at each of the interfaces where the refractive index is changing.
Implementation Method 3
The Bragg wavelength is sensitive to strain as well as to temperature. This means that Bragg gratings can be used as sensing elements in fiber optical sensors.
Data Source
AI summary
A shape sensing device, system and method include an interventional instrument (102) having regions of articulation to be configured to change shape during an interventional procedure. An optical fiber (202) is disposed on or about the areas of articulation in a pattern to provide an optical signal indicating an instantaneous change or current position or orientation of the instrument. A signal interpretation module (115) is configured to receive the optical signals and interpret the instantaneous change or current position or orientation of the instrument.