Optical Fiber Shape Sensor Compensation for Surgical Instruments
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Solution Overview
Problem
Minimally invasive surgical instruments face challenges in accurately determining the shape, position, and orientation due to factors like temperature variations and axial loading, which compromise the accuracy of shape sensors used in navigational assist systems.
Innovation Solution
A shape sensing apparatus and method that incorporates an elongated optical fiber parallel to the neutral axis of a surgical instrument shaft, along with a shape sensor compensation device, to receive and compensate data for calculating precise bend measurements, thereby reducing measurement errors caused by temperature and axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shape sensor uses an optical fiber at a radial distance from the neutral axis to measure bend, then bend measurement capability is improved, but measurement precision deteriorates due to temperature variations and axial loading
Solution Approach 1:
The patent divides the measurement function into two separate components: a shape sensor optical fiber for measuring bend and a compensation optical fiber for measuring temperature and axial loading. Each fiber is positioned at different radial distances from the neutral axis, allowing independent measurement of different physical quantities. This segmentation enables the system to distinguish between bend-induced strain and environmental/axial effects.
Solution Approach 2:
The compensation optical fiber acts as an intermediary that measures the environmental and axial effects (temperature and axial loading) separately. By positioning this fiber on the neutral axis where bend-induced strain is zero, it serves as a reference that captures only the harmful factors. The tracking system then uses this intermediary measurement to compensate the shape sensor readings, removing the unwanted effects.
2Reliability
If the shape sensor optical fiber is positioned away from the neutral axis to detect bending, then bend detection capability is improved, but reliability deteriorates due to interference from axial forces
Solution Approach 1:
The measurement system is segmented into two independent measurement channels: one for bend detection (shape sensor fiber off-neutral-axis) and one for axial force detection (compensation fiber on neutral axis). This allows the system to separately quantify and compensate for axial force interference, improving the reliability of bend measurements.
Solution Approach 2:
The system implements a feedback mechanism where the compensation fiber continuously monitors axial loading and temperature effects. This information is fed back to the tracking system, which automatically adjusts the bend measurements by subtracting the measured interference components. This closed-loop approach enhances measurement reliability by dynamically compensating for varying axial forces during instrument operation.
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
The solution enhances the accuracy and precision of shape sensing in surgical instruments by effectively separating and compensating for temperature and axial force-induced errors, leading to improved navigational assist systems and reduced measurement errors.
Implementation Method 1
a first shape sensor with an elongated optical fiber generally parallel to and at a first radial distance from the neutral axis of the elongated shaft
Implementation Method 2
receiving compensating data from the shape sensor compensation device for use in calculating a bend measurement for the instrument
Data Source
AI summary
A shape sensing apparatus comprises an instrument including an elongated shaft with a neutral axis. The shape sensing apparatus also includes a first shape sensor with an elongated optical fiber extending within the elongated shaft at a first radial distance from the neutral axis. The apparatus also includes a shape sensor compensation device extending within the elongated shaft. The apparatus also comprises a tracking system for receiving shape data from the first shape sensor and compensating data from the shape sensor compensation device for use in calculating a bend measurement for the instrument.