Microwave Electrosurgical Forceps with Lossy Transmission Line
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Solution Overview
Problem
Conventional electrosurgical forceps using RF energy face challenges in safely and efficiently coagulating or sealing biological tissue due to high voltage requirements and the risk of accidental damage, such as burns or explosions, especially when used in confined spaces like the human body.
Innovation Solution
The development of electrosurgical forceps with a non-resonant unbalanced lossy transmission line structure within the jaws to deliver microwave energy, which prevents radiation and allows for efficient power delivery into tissue with lower peak voltages, reducing the risk of damage and enhancing control over the coagulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RF energy is used in electrosurgical forceps, then tissue coagulation can be achieved, but high voltage requirements and risk of accidental damage (burns or explosions) increase
Solution Approach 1:
The patent changes the operating frequency parameter from conventional RF (e.g., 50-400 kHz) to microwave frequencies (e.g., 2.45 GHz). This parameter change enables tissue heating through dielectric heating mechanisms rather than resistive heating, thereby reducing the voltage requirements and eliminating the harmful high-voltage arcs and explosions associated with conventional RF electrosurgery
Solution Approach 2:
The patent replaces the conventional RF electrical field mechanism with a microwave electromagnetic field mechanism. The microwave energy is delivered through a non-resonant unbalanced lossy transmission line structure that creates a controlled electric field for dielectric heating of tissue, substituting the high-voltage RF arc mechanism with a lower-voltage microwave field approach
2Power
If microwave energy is delivered through a resonant structure, then efficient power delivery can be achieved, but radiation and standing waves are created causing harmful effects
Solution Approach 1:
The patent deliberately designs the transmission line structure to be non-resonant, specifically avoiding quarter-wavelength and half-wavelength dimensions that would create standing waves. This preliminary design choice prevents the formation of harmful radiation patterns and standing waves before they can occur, while still achieving efficient power delivery through controlled traveling wave propagation and optimized lossy transmission line characteristics
Solution Approach 2:
The patent accepts and utilizes the inherent losses in the unbalanced lossy transmission line structure rather than trying to eliminate them. These losses, which would normally be considered harmful inefficiencies, are converted into beneficial localized heating of the tissue through the controlled attenuation of the microwave traveling wave, achieving both power delivery and tissue coagulation
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 solution enables safer and more controlled tissue coagulation with lower peak voltages, reducing the risk of accidental damage and improving the efficiency of power delivery into the tissue, while maintaining effectiveness across various surgical procedures.
Implementation Method 1
microwave energy is delivered into biological tissue from a non-resonant unbalanced lossy transmission line structure
Implementation Method 2
a non-uniform unbalanced lossy transmission line to support the microwave energy as a travelling wave
Implementation Method 3
the geometry of the transmission line is selected, e.g. on the basis of simulations or the like, such that it exhibits high loss in biological tissue at the frequency of the microwave energy
Implementation Method 4
the microwave energy is delivered into tissue through leakage from the transmission line structure
Data Source
AI summary
Electrosurgical forceps for delivering microwave energy into biological tissue from a non-resonant unbalanced lossy transmission line structure located within or formed by the jaws of the forceps. The transmission line structure may be formed across the gap between the jaw element by opposed conductive elements, which are respectively electrically connected to inner and outer conductors of a coaxial cable. Alternatively, each jaw element may comprise its own lossy transmission line, whereby a power splitter is used to divide microwave energy from the coaxial cable. The forceps may be used endoscopically in the gastrointestinal tract or laparoscopically or in open surgery.