Impedance-Based Force Sensing in Laparoscopic Forceps
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Solution Overview
Problem
Current robot-assisted laparoscopic surgery systems lack the ability to effectively perceive and quantify the contact forces exerted on tissues during surgical interventions, due to limitations in sensor technology and spatial constraints within the surgical tool.
Innovation Solution
A sensory perception system that utilizes an electrosurgical forceps coupled with an impedance measurement circuit and an electrocautery radiofrequency signal generator to measure contact impedance between the forceps and tissue, converting this impedance into a force vector, which is then used to provide sensory feedback to the surgeon without additional sensors on the forceps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical sensors or elastic elements are integrated on the cannula to measure contact forces, then force measurement capability is improved, but device complexity and spatial constraints are worsened
Solution Approach 1:
The patent replaces mechanical sensors and elastic elements with an electrical impedance measurement system. The forceps incorporate electrodes that measure electrical impedance between the forceps and tissue, which correlates with contact force. This substitution eliminates the need for mechanical force sensors integrated on the cannula, reducing device complexity while maintaining force measurement capability.
Solution Approach 2:
The patent introduces electrical impedance as an intermediary parameter to indirectly measure contact force. Instead of directly measuring mechanical force with sensors on the forceps, the system measures electrical impedance between electrodes on the forceps and the tissue, which serves as a mediator that correlates with contact force magnitude.
2Loss of information
If additional sensors are added to the forceps for force detection, then sensory feedback capability is improved, but the size and complexity of the surgical tool are worsened
Solution Approach 1:
The patent replaces mechanical force sensors with electrical impedance measurement circuitry. The forceps contain electrodes connected to an impedance measurement system that detects contact force through electrical properties rather than mechanical sensing, avoiding the need for complex mechanical sensor integration on the forceps structure.
Solution Approach 2:
The forceps are designed to perform multiple functions: surgical manipulation, electrocautery delivery, and force measurement through impedance sensing. The same electrical conductors used for electrocautery can also serve as measurement electrodes, allowing the forceps to function as both a surgical tool and a sensing device without requiring separate dedicated sensor components.
3Measurement precision
If mechanical transmission systems are used to transfer force signals from the distal end, then force perception is improved, but device complexity and spatial requirements are worsened
Solution Approach 1:
The patent replaces mechanical transmission systems with electrical signal transmission. Instead of using mechanical linkages or elastic elements to transmit force information from the distal end of the forceps to the proximal end, the system uses electrical impedance measurements conducted through electrodes and measured by an impedance meter, transmitting force information as electrical signals rather than mechanical deformations.
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 accurate detection and quantification of contact forces, allowing for improved surgical precision and safety by providing sensory feedback to the surgeon without increasing the size or complexity of the surgical tool, and allows for the construction of a three-dimensional model of the surgical environment.
Implementation Method 1
measuring a signal indicative of a magnitude corresponding to the value of a contact impedance between the electrosurgical forceps and a patient's tissue
Implementation Method 2
an electrocautery radiofrequency signal generator electrically coupled to the impedance measurement circuit and operable for supplying energy, as both monopolar and bipolar energy, to the electrosurgical forceps
Data Source
AI summary
The present invention proposes a sensory perception system for robot-assisted laparoscopic surgery. The invention comprises an electrosurgical forceps coupled to a surgical tool, an electrocautery radiofrequency signal generator and an impedance measurement circuit. The latter includes a measurement sensor for measuring a signal indicative of a magnitude corresponding to the value of contact impedance between the forceps and a patient's tissue; an oscillator; a first electrical circuit with resistors and a voltage limiter for protecting the measurement sensor and the oscillator; and a second electronic circuit with switches. The sensor and the oscillator are connected to the forceps by means of a power cable of the surgical tool. A processor connected to the measurement circuit receives said measured signal and converts same into a force vector, the modulus of which is a function of the contact impedance being measured and the argument is a function of the trajectory being followed.