Optical Shape Sensing Fiber Twist Isolation Guide Tube
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Solution Overview
Problem
Optical shape sensing fibers in medical instruments face instability and reduced accuracy due to excessive twist along the longitudinal axis, which limits their ability to differentiate phase differences and maintain accurate shape reconstruction, especially in clinical procedures where significant torque is applied.
Innovation Solution
A shape sensing system that includes a guide tube and an optical shape sensing device with optical fibers, where the device is unconstrained and free to slip within the guide tube, preventing torsional friction and allowing the fiber to rotate independently of the instrument, using a clutch mechanism to limit rotation and prevent over-twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the optical shape sensing device is rigidly fixed to the instrument, then the instrument can be torqued effectively, but excessive twist is introduced to the fiber causing loss of shape reconstruction accuracy
Solution Approach 1:
The system divides the optical shape sensing device into multiple independent optical fibers that can move relative to each other and the guide tube. This segmentation allows each fiber to independently accommodate torsional forces without transferring twist to other fibers, maintaining measurement precision while enabling effective torque transmission through the guide tube.
Solution Approach 2:
A guide tube is introduced as an intermediary component between the optical shape sensing device and the instrument. The guide tube allows the optical fibers to move freely within it, acting as a mediator that decouples the torque transmission function from the shape sensing function, preventing twist transfer to the fibers while maintaining effective instrument operation.
2Measurement precision
If the optical fiber is allowed to move freely within the instrument lumen, then twist is minimized, but friction between the fiber and lumen wall may still introduce rotational constraints
Solution Approach 1:
The guide tube serves as an intermediary that provides a low-friction environment for the optical fibers. By allowing the fibers to move freely within the guide tube lumen, friction-induced twist is minimized while the guide tube itself can transmit torque effectively, thus protecting measurement precision without compromising force transmission.
Solution Approach 2:
The system changes the physical parameters of the interaction between the optical fiber and the instrument lumen by introducing the guide tube. This alters the friction characteristics and allows the fiber to slide more freely, reducing friction-induced twist while maintaining the ability to transmit necessary forces during the procedure.
3Ease of operation
If multiple π turns of torque are applied during vascular procedures, then the instrument can be manipulated effectively, but cumulative twist exceeds the 2π limit causing loss of stability
Solution Approach 1:
The optical shape sensing device is segmented into multiple independent optical fibers that can rotate independently within the guide tube. This allows the instrument to undergo multiple π turns of torque manipulation while each fiber independently accommodates the rotation without accumulating excessive twist, maintaining shape sensing stability throughout the procedure.
Solution Approach 2:
The system transitions from a static fixed configuration to a dynamic configuration where the optical fibers can move and rotate freely within the guide tube. This dynamic arrangement allows the instrument to be manipulated through multiple torque cycles while the fibers continuously adapt their position, preventing cumulative twist from exceeding stability limits.
Data Source
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AI summary
A shape sensing system includes a guide tube (304) and an optical shape sensing device (104) including one or more optical fibers and being proximally fixed at a fixation point and being disposed within the guide tube. An interventional instrument (102) is rigidly attached to a handle (212) to prevent rotation of the instrument relative to the handle. The instrument has a lumen configured to receive the guide tube therein such that the optical shape sensing device is unconstrained throughout the instrument and the handle, and the guide tube is free to slip relative to at least rotation of the instrument and the handle without transferring torsional friction to optical shape sensing device.