Applicator Needle PTFE Spacers for Microwave Thermoablator
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Solution Overview
Problem
Existing microwave thermoablator needles face manufacturing challenges due to the use of hand-wound dielectric spirals made from PEEK, which are prone to displacement and inconsistent pitch, affecting electrical characteristics and power dissipation, and require materials better suited for microwave applications.
Innovation Solution
The use of PTFE spacers for centering and spacing between the external and internal conductors, which are made from Polytetrafluoroethylene, providing consistent dielectric properties and low friction, facilitating assembly and ensuring reliable operation with a configuration that maintains maximum propagation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hand-wound PEEK spirals are used for electrical insulation between conductors, then the applicator needle can be manufactured, but the spiral pitch becomes inconsistent and the spiral may displace during assembly
Solution Approach 1:
The patent extracts the problematic hand-wound spiral insulation and replaces it with pre-fabricated dielectric spacers that are inserted into the assembly. This removes the source of manufacturing inconsistency while maintaining the essential insulation function between conductors.
Solution Approach 2:
The dielectric spacers are pre-formed with precise dimensions and characteristics before assembly. This preliminary preparation ensures consistent pitch and positioning without requiring manual winding during the assembly process, thereby improving manufacturing precision.
2Length of moving object
If the spiral coils are placed close together to accommodate the small needle size, then the needle maintains its small diameter, but the pitch becomes too small compared to the microwave wavelength causing unpredictable dielectric constant variation
Solution Approach 1:
The patent changes the dielectric parameters by using spacers with optimized dimensions and materials (such as PTFE with known microwave characteristics) rather than tightly wound spirals. This results in more predictable dielectric constant values and reduces power dissipation while maintaining the small needle diameter.
3Ease of manufacture
If PEEK material is used for the dielectric spiral, then the spiral can provide electrical insulation, but the material has not been characterized for microwave applications and exhibits unpredictable electromagnetic behavior
Solution Approach 1:
The patent changes the material parameters by selecting dielectric materials that have been specifically characterized for microwave applications, such as PTFE, which has well-documented electromagnetic properties including a known dielectric constant and low loss tangent. This ensures predictable and reliable microwave transmission while maintaining electrical insulation functionality.
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 PTFE spacer configuration ensures repetitive and reliable operation of the microwave thermoablator needle, improving assembly simplicity and maintaining consistent dielectric properties across a high temperature range, reducing manufacturing issues and enhancing power transmission efficiency.
Implementation Method 1
The internal conductor and the external conductor must maintain their coaxiality along the entire longitudinal development of the applicator needle... the electrical insulation between the external and internal tubular conductor significantly affects the electrical operating characteristics of the applicator needle
Implementation Method 2
PTFE is a well-characterised material for microwave applications and as a dielectric has negligible electromagnetic losses... which remain constant in a very high temperature range
Implementation Method 3
the needle will heat the tumor due to the high water content of biological tissues and raise the temperature to a level that in a few minutes the neoplastic cells will be destroyed irreversibly
Data Source
Figure 1~5
Figure 6
AI summary
Applicator needle for thermoablators with a plurality of special spacers separating the internal conductor from the external tubular conductor.