Microwave Ablation Applicator Shaft with Segmented Fibre Reinforced Plastics
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Solution Overview
Problem
Microwave ablation applicators face challenges in achieving a narrow and lightweight shaft with high stiffness, as well as a strong attachment method for the applicator tip, due to the electrical conductivity of carbon fibre reinforced plastics (CFRP) and inadequate previous attachment techniques.
Innovation Solution
A shaft assembly using fibre reinforced plastics with elongate fibres bound in a plastics material, where at least some fibres extend into and around an annular slot of the applicator tip, providing a secure and non-conductive attachment, and an antenna assembly with a coaxial conductor and dielectric layers for microwave energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fibre reinforced plastics (CFRP) are used for the shaft to achieve higher strength and stiffness, then the shaft can be narrower and lighter, but the electrical conductivity of carbon fibres prevents attachment to the electrically conductive antenna tip
Solution Approach 1:
The shaft is divided into multiple sections with different fibre orientations and material compositions. The distal section uses non-conductive fibres (glass or aramid) to ensure electrical compatibility with the antenna tip, while proximal sections can use CFRP for maximum stiffness. This segmentation allows each section to be optimized for its specific functional requirements.
Solution Approach 2:
Different regions of the shaft have different material properties tailored to local requirements. The distal end near the antenna tip uses electrically insulating fibres to prevent conductivity issues, while other regions use CFRP for enhanced mechanical performance. This local differentiation resolves the contradiction between electrical compatibility and structural strength.
2Length of moving object
If the shaft is made narrower to reduce overall size, then the applicator is more minimally-invasive, but the shaft stiffness becomes insufficient
Solution Approach 1:
The shaft employs composite fibre-reinforced plastics with fibres oriented at specific angles (including circumferential orientations) to maximize stiffness-to-diameter ratio. This allows the shaft to maintain high stiffness while keeping the outer diameter narrow, enabling minimally-invasive application without sacrificing structural integrity.
Solution Approach 2:
Instead of increasing shaft diameter to improve stiffness, the invention uses circumferential fibre orientation to enhance stiffness in the radial direction. This dimensional approach to reinforcement allows narrow shaft design while maintaining adequate stiffness through strategic fibre placement.
3Ease of manufacture
If previous attachment techniques are used for the applicator tip, then the assembly is simple to manufacture, but the attachment is not strong enough to prevent tip separation during use
Solution Approach 1:
The fibres are positioned and oriented during shaft manufacturing to extend into the tip engagement region before the tip is attached. This preliminary preparation creates optimal bonding conditions, allowing strong mechanical interlocking when the tip is subsequently attached, thereby ensuring strong attachment without complex post-processing.
Solution Approach 2:
The use of fibre-reinforced plastics provides inherent mechanical strength and bonding capability at the tip-shaft interface. The fibres extend into the engagement region and create strong mechanical interlocking with the tip, ensuring robust attachment that prevents separation during use while maintaining manufacturing feasibility.
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 a shaft assembly that is both narrow and stiff, with a secure attachment of the applicator tip, ensuring effective microwave energy radiation and preventing tip separation during use.
Implementation Method 1
at least a part of the shaft is of a fibre reinforced plastics material having a plurality of elongate fibres bound in a plastics material
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
CFRP materials contain carbon fibres that are electrically conductive, and are, therefore, not suitable for attachment to an electrically conductive tip of the antenna assembly, since the conductivity of the carbon would prevent radiation of microwave energy from the applicator tip
Implementation Method 5
a fibre reinforced plastics material having a plurality of elongate fibres bound in a plastics material
Data Source
AI summary
A shaft assembly for a microwave ablation applicator which includes 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 which defines therein a hollow inner volume and a longitudinal axis of the antenna assembly, and an applicator tip mounted on the second end of the elongate shaft. The applicator tip defines an annular slot with which the second end of the elongate shaft engages. At least part a portion of the second end of the shaft is of a fibre reinforced plastics material having a plurality of elongate fibres bound in a plastics material, at least some of the fibres extending at least partially circumferentially around the annular slot of the applicator tip.