Multi-Frequency Impedance Assessment for Ablation Lesion Depth
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Solution Overview
Problem
Current methods for assessing the efficacy and characteristics of tissue ablation lesions, such as those created by radiofrequency or cryogenic ablation, face challenges in providing real-time feedback on lesion depth and quality due to limitations in impedance measurements, which often result in binary data and do not account for varying tissue levels.
Innovation Solution
A method and system that utilize multi-frequency and multi-polarity impedance measurements to assess tissue contact, lesion quality, and depth by comparing baseline and post-treatment impedance characteristics, including impedance magnitude and phase, to generate an indication of treatment efficacy, allowing for adjustments during the procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-frequency impedance measurements are used to assess ablation lesions, then the measurement process is simple, but the assessment precision is insufficient to determine lesion depth and quality
Solution Approach 1:
The patent divides the impedance measurement into multiple frequency components (e.g., 50 Hz, 400 Hz, 1 kHz, 10 kHz) to separately assess different tissue properties. Each frequency provides specific information about lesion characteristics, enabling precise depth and quality assessment without requiring complex imaging systems.
Solution Approach 2:
The patent transitions from single-frequency (one-dimensional) impedance measurement to multi-frequency (multi-dimensional) measurement. By adding the frequency dimension, the system extracts additional information about tissue properties, enabling differentiation between viable and necrotic tissue and assessment of lesion depth.
2Measurement precision
If catheter tip temperature monitoring is used for feedback control, then energy delivery control is simplified, but the temperature measurement accuracy is insufficient because catheter tip temperature differs from tissue temperature
Solution Approach 1:
The patent uses impedance measurements as an intermediary parameter to indirectly assess tissue temperature and lesion formation. Instead of directly measuring tissue temperature (which requires complex thermocouples in contact with tissue), the system measures impedance changes that correlate with temperature-induced tissue property changes, providing accurate tissue temperature assessment without direct thermal contact.
Solution Approach 2:
The patent replaces the mechanical/thermal measurement system (thermocouples requiring physical contact with tissue) with an electrical measurement system (impedance measurements). This substitution eliminates the temperature differential problem between catheter tip and tissue while providing continuous, non-invasive monitoring of tissue thermal state.
3Loss of information
If impedance measurements are used to identify treated tissue regions, then the detection process is simple, but the information provided is binary and insufficient for real-time assessment of lesion characteristics
Solution Approach 1:
The patent changes the measurement parameter from single-frequency impedance magnitude to multi-frequency complex impedance (including magnitude and phase). This parameter expansion transforms the binary viable/necrotic distinction into a continuous spectrum of tissue states, enabling real-time assessment of lesion depth, quality, and formation rate 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 precise assessment of tissue ablation treatment efficacy by providing real-time feedback on lesion characteristics, improving the accuracy of treatment depth and quality, and allowing for adjustments during the procedure to ensure effective energy delivery.
Implementation Method 1
obtaining baseline impedance characteristics at a first plurality of frequencies with the medical device; obtaining post-treatment impedance characteristics at a second plurality of frequencies with the medical device
Data Source
AI summary
A method of assessing a tissue ablation treatment, including positioning a medical device adjacent a target tissue; measuring a first impedance magnitude a first frequency with the medical device; measuring a first impedance phase at a second frequency with the medical device; ablating at least a portion of the target tissue with the medical device; measuring at second impedance magnitude at a third frequency with the medical device; measuring a second impedance phase at a fourth frequency with the medical device; comparing at least one of (i) the first and second impedance magnitudes and (ii) the first and second impedance phases; and providing an indication of the efficacy of the ablation treatment based at least in part on the comparison.