Catheter Dithering Mechanism for Force Sensing
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Solution Overview
Problem
Current minimally invasive medical procedures face challenges in accurately sensing forces applied to the distal end of steerable catheters due to the compliant nature of instruments and frictional loads, making it difficult for physicians to gauge contact forces with tissue structures.
Innovation Solution
A medical instrument system with a dithering mechanism that axially displaces the distal tip of the catheter relative to the proximal portion, coupled with force sensors to measure forces applied to the push-pull member, allowing for accurate calculation of net external axial forces applied to the catheter tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a robotically controlled catheter is used, then the catheter can be precisely positioned and controlled, but the operator cannot tactilely sense forces applied to the distal end
Solution Approach 1:
The patent replaces the mechanical tactile sensing system with an electronic force sensing system. Force sensors (strain gauges, load cells, or capacitive sensors) are integrated into the catheter shaft to directly measure forces applied to the distal end, converting mechanical force information into electrical signals that can be transmitted to the operator interface.
Solution Approach 2:
The patent introduces force sensors as intermediary elements between the catheter and the operator. These sensors act as mediators that capture force information at the distal end and transmit it through the robotic system to the operator interface, enabling indirect tactile feedback without direct mechanical coupling.
2Measurement precision
If force sensors are integrated into the catheter, then force measurement capability is achieved, but device complexity increases
Solution Approach 1:
The patent designs the catheter shaft to serve multiple functions: it acts as both the structural support element and the mounting platform for force sensors. The same shaft that provides mechanical strength also houses the sensing elements, eliminating the need for separate sensor mounting structures and reducing overall device complexity.
Solution Approach 2:
The patent merges the force sensing function with the existing catheter structure. Strain gauges are bonded directly to the catheter shaft, and load cells are integrated into the shaft assembly, combining structural and sensing functions into a single unified component rather than adding separate sensing systems.
3Adaptability or versatility
If the catheter shaft is made compliant for navigation, then the catheter can navigate tortuous pathways, but force sensing accuracy deteriorates due to shaft deformation
Solution Approach 1:
The patent divides the catheter into distinct functional segments: a compliant navigation section that allows tortuous pathway traversal and a stiffer sensing section that houses the force sensors and provides accurate force measurement. This segmentation allows each section to optimize its properties for its specific function without compromising the other.
Solution Approach 2:
The patent applies different mechanical properties to different parts of the catheter. The distal portion is made highly compliant for navigation, while the proximal portion containing the force sensors is made stiffer to minimize deformation during force measurement, ensuring accurate readings despite overall catheter compliance.
4Ease of operation
If frictional loads are present in the catheter system, then the catheter can be controlled remotely, but accurate force sensing at the distal end becomes difficult
Solution Approach 1:
The patent extracts the force sensing function from the distal tip and places it at the proximal end of the catheter, near the operator interface. By measuring forces at the proximal end where frictional effects are minimal and directly transmitting these measurements to the operator, the system eliminates the problem of frictional loads masking distal force information.
Solution Approach 2:
The patent implements a feedback system where force sensors continuously measure forces applied to the catheter and transmit this information to the operator interface in real-time. This feedback loop allows the operator to perceive distal forces despite frictional loads by providing direct measurement data rather than relying on tactile sensation through the compliant shaft.
Data Source
AI summary
A medical system comprises a medical probe including an elongated probe body, a lumen extending within the probe body, an axially flexible section, and a push-pull member slidably disposed within the lumen. The system comprises a ditherer mechanically coupled to the member for cyclically displacing it axially back and forth within the lumen, such that the ends of the probe body are axially displaced relative to each other via the axially flexible section. The system further comprises a sensor for sensing a force axially applied to the distal end of the probe body. A method comprises introducing a medical probe into a patient, axially dithering the distal end of the medical probe back and forth relative to the proximal end of the medical probe, and sensing a force applied between tissue of the patient and the distal end of the medical probe while the distal end is axially dithered.