Friction Wheel Position Sensing for Intravascular Catheters

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Solution Overview

Problem

Existing intravascular imaging and pressure measurement systems face inaccuracies in determining the translation and position of catheter components due to unreliable velocity measurement and estimation, leading to errors in vascular imaging and pressure gradient calculations.

Innovation Solution

A system comprising a catheter with a sensor and cable connected to friction wheels, where the cable's motion causes rotation of the wheels, and a position sensor with a movable element relative to a reference element, generating a position signal, is used to accurately determine the catheter's position and translation within the vasculature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If velocity measurement and estimation methods are used to determine catheter translation, then the system can track catheter movement, but measurement inaccuracies lead to errors in position determination and image construction

Engineering Contradiction:

Improvecatheter position measurement precisionVSAvoidvelocity measurement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces velocity-based measurement methods with a direct position sensing system using encoders on friction wheels. Instead of calculating position from velocity measurements over time, the system directly measures cable displacement through encoder signals from the friction wheels, eliminating cumulative errors and improving both measurement precision and reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a catheter is used to measure pressure gradient across a lesion, then pressure measurements can be obtained, but the catheter introduces additional flow obstruction that exaggerates the measured pressure gradient

Engineering Contradiction:

Improvepressure gradient measurement precisionVSAvoidflow obstruction by catheter

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the pressure sensing function from a physical catheter that would obstruct flow. Instead of using a catheter-based pressure sensor, the system uses a pressure sensing guidewire that can measure pressure with minimal flow obstruction, thereby eliminating the harmful effect of additional blockage while maintaining measurement capability.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If a guidewire with pressure sensor is used to measure pressure drop, then flow obstruction is minimized, but the guidewire must be repositioned across multiple lesions which is time-consuming

Engineering Contradiction:

Improveflow obstructionVSAvoidtime for guidewire repositioning

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The patent creates a multi-functional system where a single catheter assembly integrates both position sensing capabilities (through friction wheels and encoders) and pressure measurement capabilities. This unified system can track the position of multiple sensors simultaneously and associate measurements with locations, eliminating the need to reposition the guidewire for each measurement point.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Measurement precision

If friction wheels are used to sense cable motion, then position can be accurately determined, but the system complexity increases with additional sensing components

Engineering Contradiction:

Improvecable displacement measurement precisionVSAvoidposition sensing system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the position sensing function into the existing cable-driven catheter control mechanism. The friction wheels are integrated with the cable system that already exists for controlling catheter rotation and translation. By combining position sensing with the existing mechanical control system, the patent achieves accurate measurement without proportionally increasing overall system complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 system provides reliable position sensing, enabling precise construction of 360-degree images and accurate pressure gradient measurements, reducing errors and improving diagnostic accuracy in intravascular procedures.

Implementation Method 1

A friction wheel may be pressed against a cable of a catheter such that proximal and distal motion of the cable causes rotation of the friction wheel

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP3457947B1Position sensing in intravascular processes

Publication Date: 2023.03.22 ACIST MEDICAL SYSTEMS INC

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AI summary

Systems can include at least one friction wheel configured to engage a catheter of an intravascular system such that proximal or distal motion of the catheter causes the friction wheel to rotate. A position sensor can include a reference element and a movable element, wherein the movable element is configured to move relative to the reference element in response to rotation of the at least one friction wheel. The position sensor can provide a position signal representative of the rotation of the at least one friction wheel. An intravascular processing engine can receive both the position signal from the position sensor and an intravascular signal from the catheter.