Dynamically Tuned Microwave Ablation Probe
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Solution Overview
Problem
Conventional microwave probes have a narrow operational bandwidth, leading to impedance mismatch between the microwave delivery system and tissue during ablation procedures due to changes in tissue dielectric constant, resulting in ineffective energy delivery and dispersion.
Innovation Solution
A microwave ablation probe that can be dynamically tuned by adjusting the shape, size, and dielectric properties of its components, such as the length of conductors and insulating layers, to maintain an optimal impedance match during tissue ablation, using mechanisms like sliding inner conductors and thermally changing dielectric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional microwave probes with fixed structure are used, then the probe construction is simple, but the operational bandwidth is narrow and impedance match is lost during ablation due to tissue dielectric constant changes
Solution Approach 1:
The patent applies dynamics by making the probe structure adjustable during operation. The inner conductor can be moved axially within the outer conductor to change the radiating element length, and the dielectric material properties change with temperature. This dynamic adjustment allows the probe to maintain impedance match across different tissue states during ablation, resolving the contradiction between simple construction and broad operational bandwidth.
Solution Approach 2:
The patent changes physical parameters of the probe components during operation. The dielectric constant of the insulating material changes with temperature (thermally changing dielectric properties), and the electrical length of the radiating element changes as the inner conductor moves axially. These parameter changes enable the probe to adapt to tissue dielectric constant changes, expanding operational bandwidth without excessive structural complexity.
2Reliability
If the probe structure is fixed, then manufacturing is simple, but the probe detunes as tissue is cooked and dielectric constant decreases, causing impedance mismatch
Solution Approach 1:
The patent implements feedback through the thermal coupling between the probe and tissue. As tissue is ablated and its dielectric constant changes, the temperature of the probe and surrounding dielectric material changes, automatically adjusting the dielectric properties and conductor length to maintain impedance match. This passive feedback mechanism improves reliability without requiring complex active control systems.
Solution Approach 2:
The probe structure serves itself by using the thermal energy already present during ablation to adjust its own dielectric properties. The thermally changing dielectric material automatically adapts its constant in response to temperature changes, and the movable inner conductor allows the structure to self-adjust its electrical length, maintaining impedance match without external intervention.
3Productivity
If conventional narrow band probes are used, then device complexity is low, but energy delivery becomes ineffective when wavelength increases beyond probe bandwidth
Solution Approach 1:
The patent uses dynamics to maintain energy delivery efficiency throughout the ablation process. By allowing axial movement of the inner conductor and using thermally changing dielectric materials, the probe dynamically adjusts its resonant frequency and impedance to match the changing tissue conditions, preventing detuning and maintaining effective energy delivery despite wavelength changes.
Solution Approach 2:
The patent changes the electrical parameters of the probe during operation. The dielectric constant of the insulating material varies with temperature, and the effective length of the radiating element changes as the inner conductor moves. These parameter changes enable the probe to maintain resonance and efficient energy transfer across the full range of tissue dielectric constant changes during ablation.
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
Enables efficient and consistent microwave energy delivery throughout the ablation procedure by maintaining an optimal impedance match, ensuring effective tissue denaturation while minimizing damage to surrounding healthy cells.
Implementation Method 1
The inner conductor is slidably disposed within the secondary inner conductor
Implementation Method 2
dielectric properties of the radiating portion are adjusted by using materials with thermally changing dielectric properties; thus, as the temperature of the tissue and the probe changes during ablation the dielectric properties of the probe are automatically adjusted
Implementation Method 3
microwave energy is used to coagulate and/or ablate tissue to denature or kill the cancerous cells
Implementation Method 4
microwave energy is applied via microwave ablation antenna probes which penetrate tissue to reach tumors
Data Source
AI summary
A microwave ablation probe for providing microwave energy to tissue is disclosed. The probe includes a feedline having an inner conductor, a secondary inner conductor, an insulating spacer, and an outer conductor. The inner conductor is slidably disposed within the secondary inner conductor. The feedline also includes a radiating portion having an extruded portion of the inner conductor centrally disposed therein, wherein longitudinal movement of the inner conductor relative to the feedline tunes the radiating portion.