Miniaturized Microwave Ablation Assembly Impedance Control
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Solution Overview
Problem
Microwave ablation technologies face challenges in maintaining a predictable and robust active ablation zone due to wavelength elongation in varying tissue types and heating conditions, leading to unpredictable energy delivery and ablation zone shapes.
Innovation Solution
The use of dielectric buffering with materials of unchanging dielectric constants, combined with a coaxial balun, to maintain antenna impedance match and control microwave field shape, along with a miniaturized antenna geometry that reduces radial size while maintaining energy delivery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional microwave ablation probes are used in varying tissue types and heating conditions, then wavelength elongation occurs, but this leads to unpredictable energy delivery and ablation zone shapes
Solution Approach 1:
A dielectric buffer is introduced as an intermediary material between the microwave antenna and the tissue target. This buffer layer with controlled dielectric properties (εr=2.0-4.0) acts as a mediator that stabilizes the microwave wavelength and prevents elongation effects, thereby maintaining predictable ablation zone geometry across varying tissue types and heating conditions
Solution Approach 2:
The patent controls the dielectric parameters of the buffer material to achieve wavelength stabilization. By selecting materials with specific dielectric constants and loss tangents, and by controlling buffer layer thickness (0.5-5.0 mm), the system maintains consistent wavelength characteristics despite variations in tissue properties and thermal conditions
2Volume of moving object
If antenna size is reduced for minimally-invasive procedures, then radial size decreases, but this may compromise power delivery capability
Solution Approach 1:
The patent employs a nested structure where the microwave antenna is positioned within a dielectric buffer, which is in turn contained within a cooling catheter system. This nested arrangement allows compact integration of multiple functions (energy delivery, wavelength stabilization, thermal management) in a miniaturized probe suitable for minimally-invasive procedures while maintaining adequate power delivery capability
Solution Approach 2:
The patent replaces traditional mechanical power delivery approaches with electromagnetic field optimization through dielectric buffering. By using electromagnetic principles (dielectric constant matching, wavelength control) rather than purely mechanical scaling, the system achieves effective power delivery in miniaturized antennas that would otherwise be insufficient by geometric scaling alone
3Reliability
If dielectric buffering is implemented to control wavelength, then ablation zone predictability improves, but device complexity increases
Solution Approach 1:
The dielectric buffer serves multiple functions simultaneously: it stabilizes wavelength, defines ablation zone geometry, provides thermal isolation between the antenna and surrounding tissue, and enables miniaturization of the antenna structure. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving reliable ablation zone control
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 approach enables the creation of a large, spherical, and robust active ablation zone with predictable shape and size, enhancing the focus of microwave energy on targeted tissues and improving procedural reliability in minimally-invasive procedures.
Implementation Method 1
The use of dielectric buffering with materials of unchanging dielectric constants, combined with a coaxial balun, to maintain antenna impedance match and control microwave field shape
Implementation Method 2
Once the ablation probes are properly positioned, the ablation probes induce electromagnetic fields within the tissue surrounding the ablation probes
Implementation Method 3
in the case of microwave ablation, by dielectric relaxation of water molecules within an antenna electromagnetic field
Implementation Method 4
combined with a coaxial balun, to maintain antenna impedance match
Data Source
AI summary
Microwave applicators are disclosed which include a first transmission line segment, a second transmission line segment, and a third transmission line segment. The first transmission 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 second transmission line 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 third transmission line 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. The impedance of the second transmission line segment can be adjusted by adjusting the length of the third transmission line segment.