Microwave Coagulation Applicator Cooling and Power Control
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Solution Overview
Problem
Existing microwave applicators for tissue heating in cancer treatments face challenges in achieving consistent and predictable heating patterns while minimizing damage to surrounding healthy tissue, with issues related to overheating and inefficient cooling of the applicator shafts.
Innovation Solution
A microwave applicator design featuring a coaxial transmission line with a conductive sleeve and a guide sleeve for circulating cooling fluid, along with a temperature sensor to monitor the cooling fluid temperature, ensuring the applicator remains below tissue-damaging temperatures, and phased arrays for optimized power distribution and reduced heating along the shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If microwave power is increased to achieve adequate tumor heating, then therapeutic effect is improved, but temperature control becomes difficult and risk of damaging surrounding normal tissue increases
Solution Approach 1:
The patent applies local quality by creating distinct thermal zones: a high-temperature coagulation zone (50-100°C) at the antenna tip for tumor destruction, and a lower-temperature hyperthermia zone (40-45°C) in surrounding tissue for therapeutic effect. This spatial differentiation of temperature zones allows high power delivery to the tumor while protecting surrounding normal tissue from excessive heating through controlled thermal gradients.
2Object-affected harmful factors
If cooling is applied to the applicator shaft to prevent tissue damage, then safety is improved, but heating efficiency of the treatment zone may be reduced
Solution Approach 1:
The patent extracts the cooling function from the treatment zone and applies it specifically to the applicator shaft and surrounding tissue. The cooling system removes excess heat from the applicator body and peri-tumoral tissue while leaving the tumor coagulation zone at high temperature. This separation allows the applicator shaft to be actively cooled to prevent damage to entry track tissue, while the tumor zone maintains therapeutic hyperthermia or coagulation temperatures.
3Duration of action of moving object
If prolonged exposure time is used to ensure complete tumor eradication, then treatment efficacy is improved, but damage to surrounding normal tissue increases
Solution Approach 1:
The patent implements periodic action through cyclic alternation between high-power coagulation phases and lower-power hyperthermia phases. During coagulation cycles, high power is delivered to rapidly elevate tissue temperature for tumor destruction. During hyperthermia cycles, power is reduced to maintain therapeutic temperatures in surrounding tissue without causing damage. This temporal modulation allows prolonged total treatment time for complete tumor eradication while interspersing cooling periods that protect surrounding normal tissue from cumulative thermal damage.
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 design achieves more consistent and predictable tissue heating, minimizing damage to healthy tissue and improving the efficacy of microwave coagulation and ablation treatments by maintaining controlled temperatures and uniform power deposition.
Implementation Method 1
An antenna for radiating microwave energy into tissue to be treated is disposed toward the insertion end of the elongate applicator body
Implementation Method 2
microwave energy radiated from the antenna penetrates and heats the tissue
Implementation Method 3
A guide sleeve is positioned concentrically within this cooling fluid space... to cool the microwave energy transmission line and the conductive outer sleeve
Implementation Method 4
The guide sleeve guides flow of a circulating cooling fluid along the outside surface of the microwave energy transmission line and the inside surface of the outer conductive sleeve
Implementation Method 5
A temperature sensor is positioned to measure the approximate temperature of the circulating cooling fluid thereby indicating that the microwave energy transmission line and the outer conductive sleeve are being actively cooled
Implementation Method 6
A coaxial microwave energy transmission line is disposed within the applicator body to conduct microwave energy from the attachment end of the applicator to the antenna
Data Source
AI summary
A microwave applicator for insertion into living body tissue for use in microwave coagulation and ablation treatments includes a microwave transmission line extending between an attachment end of the applicator and an antenna toward an insertion end of the applicator with an outer conductive sleeve forming an enclosed cooling fluid space around the transmission line. Circulation of cooling fluid is guided in the cooling fluid space by a guide sleeve. A temperature sensor senses the approximate temperature of cooling fluid to indicate cooling fluid is circulating. A multiplexing and power splitting circuit provides outputs tuned for one or for more than one applicator to be attached and detects the number of applicators and correct connection. A cadence sound generator can be used in conjunction with depth markings on the applicator to provide substantially constant withdrawal of the applicator from the treated tissue after treatment to provide track ablation.