Microwave Electrosurgical Tip Cooling Without Liquid Coolant
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Solution Overview
Problem
Conventional electrosurgical instruments face challenges in delivering microwave energy to treatment sites within the body due to cable heating, which can damage surrounding tissue, and require coolant circulation that hinders miniaturization.
Innovation Solution
An electrosurgical instrument with a non-liquid thermal energy transfer mechanism using a heat sink at the distal end of a coaxial cable to draw heat away from the tip, combined with a thermal gradient provided by a thermally conductive material and active cooling at the proximal end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coaxial cable is used to convey microwave energy to the treatment site, then microwave energy can be delivered to target tissue, but cable heating occurs which can damage surrounding biological tissue
Solution Approach 1:
The patent extracts the thermal management function from the microwave delivery system by introducing a separate heat sink component. The heat sink is thermally coupled to the coaxial cable to draw heat away from the cable and surrounding tissue, while the microwave energy delivery function remains intact through the original cable pathway.
Solution Approach 2:
The heat sink acts as an intermediary thermal management component between the microwave energy source and the biological tissue. It provides a dedicated thermal conduction pathway that separates the microwave energy delivery function from the thermal control function, allowing heat to be drawn away from the cable without interfering with microwave transmission.
2Temperature
If a liquid coolant circulation system is used to cool the cable, then cable heating is reduced, but the space required for coolant circulation prevents further miniaturisation of the cable and distal probe
Solution Approach 1:
The patent extracts the cooling function from the cable structure itself and places it in a separate heat sink component. This eliminates the need for internal coolant circulation channels within the cable, allowing the cable and distal probe to be miniaturized while thermal management is handled by the external heat sink.
Solution Approach 2:
The patent replaces the mechanical liquid coolant circulation system with a thermal conduction-based cooling system. The heat sink uses thermal conduction through thermally conductive material to draw heat away from the cable, eliminating the need for pumps, channels, and fluid circulation mechanisms that would increase cable diameter.
3Volume of moving object
If the cable diameter is reduced for miniaturisation, then access to finer body regions is enabled, but cable heating becomes more concentrated and potentially more harmful
Solution Approach 1:
The patent addresses the thermal management problem by adding a spatial dimension to the cooling system. The heat sink extends along a portion of the cable length and provides a distributed thermal conduction pathway, spreading the heat dissipation function across multiple locations rather than concentrating it at a single point.
Solution Approach 2:
The heat sink creates additional thermal conduction pathways that parallel the cable structure. By providing multiple thermal contact points and conduction paths through the thermally conductive material, the system distributes the heat dissipation load across multiple channels, preventing concentration of thermal loss.
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
Prevents unwanted tissue damage by thermal loss while allowing for smaller device diameters, enabling access to finer body regions without coolant circulation space.
Implementation Method 1
a heat sink mounted at an interface between the flexible coaxial transmission line and radiating tip portion, wherein the heat sink is in thermal communication with a proximal end of the distal coaxial transmission line and configured to draw thermal energy from the radiating tip portion
Implementation Method 2
Water molecules have a permanent electric dipole moment, meaning that a charge imbalance exists across the molecule. This charge imbalance causes the molecules to move in response to the forces generated by application of a time varying electric field as the molecules rotate to align their electric dipole moment with the polarity of the applied field. At microwave frequencies, rapid molecular oscillations result in frictional heating and consequential dissipation of the field energy in the form of heat. This is known as dielectric heating.
Data Source
AI summary
Various embodiments provide an electrosurgical instrument comprising: a flexible coaxial transmission line arranged to convey microwave energy; a radiating tip portion connected at a distal end of the flexible coaxial transmission line and configured to receive the microwave energy, the radiating tip portion comprising: a distal coaxial transmission line for conveying the microwave energy; and a needle tip mounted at a distal end of the distal coaxial transmission line, the needle tip being arranged to deliver the microwave energy into biological tissue; and a heat sink mounted at an interface between the flexible coaxial transmission line and radiating tip portion. The heat sink is in thermal communication with a proximal end of the distal coaxial transmission line and configured to draw thermal energy from the radiating tip portion. Also, a maximum outer diameter of the radiating tip portion is smaller than an outer diameter of the flexible coaxial transmission line. An associated electrosurgical system is also disclosed.