Ultrasonic Surgical Instrument Control System for Constant Power Delivery

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Solution Overview

Problem

Ultrasonic surgical instruments are highly responsive to surgeon pressure, leading to inconsistent power delivery and potential tissue damage due to excessive energy application, as they lack effective mechanisms to maintain a constant power profile despite varying pressure levels.

Innovation Solution

A control system that regulates electrical energy supplied to the ultrasonic surgical instrument, maintaining constant power by adjusting voltage and current based on measured impedance to ensure consistent power delivery regardless of applied force, thereby preventing excessive tissue damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If ultrasonic surgical instruments are made highly responsive to surgeon pressure to enable precise control, then ease of operation is improved, but power consistency deteriorates leading to tissue damage

Engineering Contradiction:

Improveresponsiveness to surgeon pressureVSAvoidpower consistency

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control system continuously monitors the impedance of the ultrasonic instrument and uses this feedback to dynamically adjust the electrical energy supplied by the generator. This closed-loop control maintains constant power delivery despite variations in surgeon-applied pressure, resolving the contradiction between responsiveness and power consistency.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical pressure-control mechanisms (such as springs in the actuation assembly) with an electrical control system that regulates power through impedance monitoring. This substitution eliminates the limitations of mechanical systems while maintaining ease of operation and ensuring reliable power consistency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If mechanical pressure control mechanisms (springs) are added to limit applied pressure, then power consistency is improved, but device complexity increases

Engineering Contradiction:

Improvepower consistencyVSAvoidmechanical control mechanisms

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent eliminates complex mechanical pressure-control mechanisms by implementing an electrical control system that monitors impedance and regulates power delivery. This approach achieves power consistency through electronic feedback rather than mechanical constraints, significantly reducing device complexity while maintaining reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If higher ultrasonic energy levels are transmitted to improve cutting effectiveness, then productivity is improved, but tissue damage increases due to excessive power

Engineering Contradiction:

Improvecutting effectivenessVSAvoidtissue damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The control system uses real-time impedance monitoring to feedback-regulate the electrical energy supplied to the ultrasonic instrument. This ensures that optimal power levels are maintained for effective cutting while preventing excessive energy transmission that would cause tissue damage, thus resolving the contradiction between productivity and safety.

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

The system ensures consistent power application to tissue, reducing the risk of tissue damage and instrument malfunction by maintaining a constant power profile, even under varying pressure conditions, thus improving surgical precision and safety.

Implementation Method 1

Vibrations generated by the transducer are transmitted to the surgical end-effector via an ultrasonic waveguide extending from the transducer section to the surgical end-effector

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

an electrically excited transducer that may be constructed of one or more piezoelectric or magneto-resistive elements in the instrument handpiece

Methodology Applied

Scientific EffectMagneto-resistive effect: Magnetoresistance

Implementation Method 3

the electrical energy supplied by the generator being controlled such that power applied by the instrument is maintained constant once a predetermined pressure threshold is met

Methodology Applied

Scientific EffectImpedance measurement: Electrical Resistance

Implementation Method 4

adjusting the current and voltage applied to the ultrasonic surgical instrument so as to maintain the power applied by the ultrasonic surgical instrument at approximately the nominal power

Methodology Applied

Scientific EffectPower regulation: Electrical Resistance

Data Source

PatentUS7821143B2System for controlling ultrasonic clamping and cutting instruments

Publication Date: 2010.10.26 CILAG GMBH INTERNATIONAL

AI summary

A control system for use with an ultrasonic surgical instrument includes a generator supplying electrical energy to an ultrasonic surgical instrument, the electrical energy supplied by the generator being controlled such that power applied by the instrument is maintained constant once a predetermined pressure threshold is met. The control system operates by assigning a nominal power at which the ultrasonic instrument is to operate and adjusting the current and voltage applied to the ultrasonic surgical instrument so as to maintain the power applied by the ultrasonic surgical instrument at approximately the nominal power.