Medical Device Contact Force Estimation via Geometry and Feedback

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Solution Overview

Problem

Current interventional medical systems face challenges in establishing and maintaining adequate contact force between medical devices and three-dimensional tissue surfaces within the body, particularly during procedures like cardiac arrhythmia treatment, where precise contact is crucial but difficult to achieve and control.

Innovation Solution

A method that estimates contact force by obtaining three-dimensional geometry information for the medical device, constructing a curve from the pivot point to the tip, estimating local rotation rates, and determining the net bending moment and torque applied, allowing for the application of an external magnetic field to achieve desired contact force against the tissue surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If computer assisted navigation and imaging systems are used to control medical device navigation, then device positioning accuracy is improved, but the ability to establish and control adequate contact force with the tissue surface deteriorates

Engineering Contradiction:

Improvedevice positioning accuracyVSAvoidcontact force control

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The system calculates contact force by integrating device geometry, orientation, and mechanical properties (bending stiffness) to provide real-time feedback on the force applied to the tissue surface. This allows the operator to adjust device positioning while maintaining controlled contact force, resolving the contradiction between precise positioning and contact force control.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces direct mechanical control of contact force with a computational model that calculates force based on device geometry and orientation data from the navigation system. This substitution allows precise control of contact force through software algorithms rather than direct mechanical manipulation, improving both positioning accuracy and force control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Length of moving object

If the medical device is extended to reach the target destination, then access to deep tissue locations is improved, but control of contact force at the distal tip deteriorates

Engineering Contradiction:

Improvedevice reachVSAvoiddistal tip control

Core Design Contradiction:

Length of moving objectVSEase of operation

Solution Approach 1:

The patent introduces a computational model as an intermediary between the operator and the distal tip of the extended device. This model calculates contact force at the distal tip by integrating data from the navigation system with device mechanical properties, allowing control of the distal tip without direct mechanical connection or complex manual manipulation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If adequate contact force is established with the tissue surface, then treatment effectiveness is improved, but risk of tissue damage from excessive force increases

Engineering Contradiction:

Improvetreatment effectivenessVSAvoidtissue damage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system provides real-time calculation of contact force based on device geometry and orientation, enabling feedback control that maintains force within the optimal range for treatment effectiveness while preventing excessive force that could cause tissue damage. This resolves the contradiction between ensuring adequate contact and preventing harm.

Inventive Principle:

Principle #23Feedback

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

Enables precise and controlled contact force estimation and application, enhancing the accuracy and effectiveness of medical procedures by ensuring firm device-tissue interaction, which is critical for treatments like cardiac arrhythmia analysis and ablation.

Implementation Method 1

From the geometry of the medical device, a net bending moment may be estimated for the distal portion of the medical device

Methodology Applied

Scientific EffectBending moment:

Implementation Method 2

estimating the contact force based on this data and the (known) bending stiffness and the total torque applied to the flexible portion of the medical device

Methodology Applied

Scientific EffectTorque: Torque

Implementation Method 3

allowing for the application of an external magnetic field to achieve desired contact force against the tissue surface

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS8192374B2Estimation of contact force by a medical device

Publication Date: 2012.06.05 STEREOTAXIS INC

AI summary

A method is provided for establishing contact of a medical device against a tissue surface within a subject body, the method comprising determination of the geometrical configuration of the distal portion of the medical device, and using this together with known control variable information to determine and control the contact force of the distal tip of the medical device against the tissue surface.