Microwave Ablation Shaft Segmentation for Stiffness and Insulation
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Solution Overview
Problem
Microwave ablation applicators face challenges in achieving a narrow and lightweight shaft with high stiffness, as carbon fibre reinforced plastics (CFRP) materials are electrically conductive and can interfere with microwave energy radiation and heat up undesirably, while non-conductive fibre reinforced plastics (FRP) materials compromise on stiffness.
Innovation Solution
A shaft assembly comprising a carbon fibre reinforced plastics (CFRP) portion for stiffness and a non-electrically conductive fibre reinforced plastics (FRP) portion, with alternating elements for engagement, allowing for a narrow diameter and high stiffness while preventing electrical conductivity issues, and an electrically insulating applicator tip to ensure effective microwave energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fibre reinforced plastics (CFRP) material is used for the shaft, then the shaft achieves high stiffness and can be made narrower, but the shaft becomes electrically conductive which prevents microwave energy radiation and causes overheating
Solution Approach 1:
The shaft is divided into multiple segments with different material properties. The proximal shaft portion uses CFRP for high stiffness, while the distal shaft portion uses non-conductive FRP to prevent electrical conductivity issues near the applicator tip. This segmentation allows each portion to fulfill its specific functional requirement.
Solution Approach 2:
Different material qualities are applied to different locations of the shaft. The proximal portion (farther from the applicator tip) has high stiffness and strength properties, while the distal portion (closer to the applicator tip) has electrical insulation properties. This local differentiation resolves the contradiction between needing stiffness overall and avoiding conductivity locally.
2Object-affected harmful factors
If non-electrically conductive fibre reinforced plastics (FRP) material is used for the shaft, then the shaft avoids electrical conductivity issues, but the shaft stiffness is reduced
Solution Approach 1:
The shaft is segmented so that only the distal portion near the applicator tip uses non-conductive FRP material, while the proximal portion uses CFRP for high stiffness. This minimizes the length of non-conductive material needed while maintaining overall shaft strength.
Solution Approach 2:
Electrical insulation properties are applied locally only where needed (distal shaft portion near the applicator tip), while the rest of the shaft maintains high stiffness properties through CFRP material. This localized application resolves the contradiction without compromising overall structural integrity.
3Length of moving object
If the shaft is made narrower and lightweight, then the applicator is more minimally invasive, but the shaft stiffness is compromised
Solution Approach 1:
The shaft uses composite construction combining CFRP and FRP materials. CFRP provides exceptional stiffness-to-weight ratio and high strength, allowing the shaft to be made narrower while maintaining required stiffness. The composite structure enables miniaturization without sacrificing mechanical properties.
Solution Approach 2:
The shaft is segmented into proximal and distal portions with different materials optimized for their specific requirements. The proximal CFRP portion provides high stiffness for structural support, while the overall narrow diameter is achieved through the high strength-to-weight ratio of the composite materials.
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 provides a shaft assembly that balances stiffness and conductivity, enabling efficient microwave energy delivery with reduced risk of overheating, thus improving the effectiveness and safety of microwave ablation procedures.
Implementation Method 1
a second shaft portion which extends longitudinally from the engagement region to the second end of the elongate shaft, the second shaft portion being of a fibre reinforced plastics material which has fibres that are non-electrically conductive
Implementation Method 2
delivering a controlled amount of microwave energy into the tumour
Implementation Method 3
The antenna assembly also includes a coaxial conductor which extends along the inner volume of the shaft in order to connect the dipole antenna element to a source of microwave energy
Implementation Method 4
Carbon fibre reinforced plastics (CFRP) materials enable the provision of a narrower side wall, and hence narrower shaft overall, due to the higher strength and stiffness of a CFRP material
Implementation Method 5
conductive fibres may be heated by the microwave to unacceptably high temperatures
Data Source
AI summary
A shaft assembly for a microwave ablation applicator having a shaft assembly and an antenna assembly located within the shaft assembly is disclosed. The shaft assembly comprises an elongate shaft which extends from a first end to a second end thereof and an applicator tip mounted on the second end of the elongate shaft.