Step-down Coaxial Microwave Ablation Applicator Design
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Solution Overview
Problem
Existing microwave ablation applicators face challenges in maintaining the shape and size of the active ablation zone due to wavelength elongation caused by tissue dehydration and varying dielectric constants across different tissue types, leading to unpredictable ablation outcomes.
Innovation Solution
The development of a reduced-size microwave ablation applicator that incorporates dielectric buffering and a coaxial balun to maintain the antenna impedance match and field shape, thereby controlling wavelength elongation and ensuring a robust, spherical active ablation zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microwave ablation is performed without dielectric buffering, then the device structure is simpler, but wavelength elongation occurs due to tissue dehydration and varying dielectric constants, leading to unpredictable ablation zone shape and size
Solution Approach 1:
A dielectric buffering segment is introduced as an intermediary component between the microwave antenna and the tissue. This buffer maintains a consistent dielectric environment, preventing wavelength elongation caused by tissue dehydration and varying dielectric constants. The buffer acts as a mediator that stabilizes the electromagnetic field propagation, ensuring predictable ablation zone geometry without requiring complex real-time adjustment mechanisms.
Solution Approach 2:
The patent employs a stepped dielectric constant approach where the dielectric buffer transitions through different dielectric constant values along its length. This parameter change allows the system to compensate for variations in tissue dielectric properties and maintain optimal impedance matching across different operating conditions, thereby preserving ablation zone predictability while avoiding overly complex adaptive systems.
2Volume of moving object
If the microwave applicator size is reduced, then the procedure is less invasive, but maintaining impedance match and field shape becomes more difficult
Solution Approach 1:
The patent implements local quality variations through a stepped dielectric structure where different sections of the dielectric buffer have different dielectric constants. This allows localized optimization of electromagnetic field distribution within the compact applicator, maintaining proper impedance matching and field shape despite the reduced overall size. Each local section is tailored to compensate for specific geometric constraints.
Solution Approach 2:
The microwave applicator utilizes composite construction combining multiple materials with different dielectric properties in a stepped configuration. This composite approach enables the compact design to maintain proper impedance transformation and field shaping capabilities that would otherwise require larger dimensions, achieving both miniaturization and performance preservation.
3Manufacturing precision
If dielectric buffering is implemented, then wavelength elongation is reduced and ablation zone is more predictable, but the device complexity increases
Solution Approach 1:
The dielectric buffer is segmented into discrete sections with different dielectric constants rather than using a single continuous material. This segmentation allows precise control over the electromagnetic field distribution and wavelength elongation compensation while keeping each individual segment relatively simple in design. The stepped structure achieves complex field control through simple geometric divisions.
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
This solution effectively reduces wavelength elongation, maintains the focus of microwave energy, and achieves a predictable and robust ablation zone, enhancing the reliability and effectiveness of microwave ablation procedures.
Implementation Method 1
a dielectric buffering segment configured to reduce wavelength elongation
Implementation Method 2
coaxial balun to maintain the antenna impedance match
Implementation Method 3
by dielectric relaxation of water molecules within an antenna electromagnetic field
Implementation Method 4
maintain the shape and size of the active ablation zone due to wavelength elongation
Data Source
AI summary
Microwave ablation applicators and methods for manufacturing the microwave ablation applicators are disclosed. A microwave ablation applicator includes a feed-line segment, a step-down segment, and a radiator base segment. The feed-line segment includes a first inner conductor, a first dielectric disposed on the first inner conductor, and a first outer conductor disposed on the first dielectric. The step-down segment includes a second inner conductor, a second dielectric disposed on the second inner conductor, and a second outer conductor disposed on the second dielectric. The radiator base segment includes a third inner conductor disposed on the third inner conductor, a third outer conductor disposed on the proximal end of the third dielectric so as to form a feed gap at a distal end of the radiator base segment, a balun dielectric disposed on the third outer conductor, and a balun outer conductor disposed on the balun dielectric.