Optical Shape Sensing Launch Point Calibration
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Solution Overview
Problem
Current optical shape sensing systems for minimally-invasive surgical procedures face challenges in accurately reconstructing the shape of optical fibers due to measurement noise and sensitivity to environmental fluctuations, and require a known launch point for accurate reconstruction, which is prone to errors and positional changes.
Innovation Solution
An optical shape sensing system employing reference markers with identifiable tracking positions and orientations within a coordinate system, combined with tracking technologies like optical and electromagnetic tracking, to identify and compensate for changes in the launch point, ensuring accurate shape reconstruction of optical fibers embedded in devices like endoscopes or guidewires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If optical shape sensing systems are used for real-time shape reconstruction, then the ability to display fiber shape in real-time is improved, but measurement noise and environmental fluctuations cause errors in launch point identification that propagate through the reconstruction
Solution Approach 1:
The patent introduces an intermediary calibration process using a tool calibrator with known geometric relationships between markers and the tool axis. This intermediary reference frame allows the system to establish accurate launch point positions before actual use, separating the precision requirement from the real-time measurement process and eliminating propagation of identification errors during shape reconstruction.
Solution Approach 2:
The system performs preliminary calibration actions by positioning the tool in a tool calibrator and establishing the relationship between markers and tool axis before actual surgical procedures. This preliminary establishment of reference frames ensures that launch point identification is accurate before real-time shape reconstruction begins, preventing error propagation during the actual measurement process.
2Measurement precision
If multiple markers with known geometric relationships are used to identify launch points, then launch point identification accuracy is improved, but the device complexity increases due to additional markers and calibration requirements
Solution Approach 1:
The tool calibrator serves multiple functions: it provides a reference frame for launch point identification, establishes geometric relationships between markers and tool axis, and can be used for different tools with varying diameters. This multi-functionality reduces the need for separate calibration systems for each tool type, thereby managing complexity while maintaining precision.
Solution Approach 2:
The system uses a copy of the tool (the tool calibrator) with identical marker geometry and known relationships to the tool axis. This physical copy allows calibration without requiring the actual surgical tool, simplifying the overall system by separating the calibration function from the measurement function while maintaining geometric fidelity.
3Measurement precision
If the tool is rotated in a tool calibrator to determine the axis of rotation, then launch point identification is improved, but the time required for calibration increases
Solution Approach 1:
The calibration process uses periodic rotation of the tool in the tool calibrator at known angles (e.g., 90 degrees) to efficiently determine the tool axis and launch point positions. This periodic sampling approach requires fewer measurement points than continuous measurement, reducing calibration time while maintaining sufficient precision for launch point identification.
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 system provides reliable identification and compensation for launch point changes, overcoming limitations of existing technologies by enhancing accuracy and robustness against noise and environmental fluctuations, ensuring precise shape reconstruction of optical fibers in real-time.
Implementation Method 1
an optical interrogation system to execute a shape reconstruction of the optical fiber based on the identification of the reconstruction launch point
Implementation Method 2
The reference tracking system identifies the reference tracking position and/or the reference tracking orientation of each reference marker within the reference coordinate system
Data Source
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AI summary
An optical shape sensing system employing an optical fiber (20) and one or more reference markers (41). Each reference marker (41) has an identifiable reference tracking position within a reference coordinate system (42). The optical fiber (20) has a reconstruction launch point (21)within the reference coordinate system (42) serving as a basis for an execution of a shape reconstruction of the optical fiber (20) within the reference coordinate system (42). The reconstruction launch point (21)of the optical fiber (20) has a known spatial relationship with each reference marker (41) to facilitate an identification of the reconstruction launch point (21)within the reference coordinate system (42).