Electrode Contact Assessment Using Frequency-Division Multiplexing
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Solution Overview
Problem
Existing methods for determining electrode contact with tissue in medical devices, such as catheters, are limited by the need for sequential determination of impedance across multiple electrode pairs, which reduces response time and can be overwhelmed by noise, especially with high-count electrode catheters.
Innovation Solution
The system applies a plurality of drive signals with unique frequencies across individual pairs of electrodes, allowing for simultaneous measurement of impedance values and synchronous demodulation of responses, thereby increasing the number of interrogable electrode pairs and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sequential determination of impedance across multiple electrode pairs is used, then device complexity is reduced, but response time increases and noise interference increases
Solution Approach 1:
The patent applies periodic action by using multiple drive signals at different frequencies that are applied simultaneously to multiple electrode pairs. Each drive signal operates periodically at its unique frequency, allowing the system to interrogate multiple electrode pairs in parallel without requiring sequential switching, thereby reducing response time while maintaining manageable device complexity through frequency-division multiplexing.
Solution Approach 2:
The patent segments the impedance measurement task by assigning unique frequencies to different electrode pairs. This frequency segmentation allows simultaneous measurement of multiple electrode pairs without signal interference, as each pair's response can be independently demodulated at its designated frequency, thus improving response time while keeping device complexity acceptable through signal separation.
2Device complexity
If sequential determination of impedance across multiple electrode pairs is used, then device complexity is reduced, but noise interference increases
Solution Approach 1:
By using periodic drive signals at unique frequencies for each electrode pair, the system enables synchronous demodulation that selectively recovers signals at their respective frequencies while rejecting noise at other frequencies. This periodic action with frequency multiplication allows parallel interrogation of multiple electrode pairs with improved signal-to-noise ratio compared to sequential measurement.
Solution Approach 2:
The patent transitions from temporal dimension (sequential measurement over time) to frequency dimension (parallel measurement using different frequencies). By adding the frequency dimension, the system can simultaneously measure multiple electrode pairs without increasing device complexity, as frequency-division multiplexing allows independent signal recovery through synchronous demodulation at each frequency, thereby reducing noise interference.
3Loss of time
If simultaneous measurement of multiple electrode pairs is implemented, then response time decreases, but device complexity increases
Solution Approach 1:
The patent uses periodic drive signals at harmonically related frequencies to enable simultaneous measurement of multiple electrode pairs. The controller generates these periodic signals and the measurement circuit uses synchronous demodulation at each frequency to recover individual impedance values, achieving fast response time while managing device complexity through frequency-based signal separation rather than requiring completely independent measurement circuits for each electrode pair.
Solution Approach 2:
The patent changes the frequency parameter of drive signals to enable simultaneous measurement of multiple electrode pairs. By assigning unique frequencies to different electrode pairs and using synchronous demodulation, the system achieves parallel measurement capability without proportionally increasing device complexity, as the same hardware infrastructure can handle multiple frequencies through parameter (frequency) differentiation.
4Reliability
If simultaneous measurement of multiple electrode pairs is implemented, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
The patent employs periodic drive signals at unique frequencies for each electrode pair, enabling synchronous demodulation that provides narrowband filtering at each frequency. This periodic action with frequency multiplication improves signal-to-noise ratio by concentrating measurement energy at specific frequencies and rejecting broadband noise, while device complexity is managed through frequency-division multiplexing rather than requiring separate dedicated circuits for each electrode pair.
Solution Approach 2:
The patent adds the frequency dimension to enable simultaneous measurement of multiple electrode pairs with improved signal-to-noise ratio. By distributing measurements across the frequency domain rather than using a single frequency or sequential time slots, the system achieves better noise rejection through frequency-selective demodulation while keeping device complexity acceptable through shared hardware resources operating at different frequency parameters.
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 reliable and efficient assessment of tissue contact and proximity for medical devices with a high number of electrodes, improving response time and signal-to-noise ratio while maintaining compliance with auxiliary current limits.
Implementation Method 1
assessing contact between an electrode and tissue using complex impedance measurements
Implementation Method 2
the impedance of an electrode is significantly higher once it comes in contact with the tissue than when the electrode is disposed within a blood pool
Implementation Method 3
measuring responses of the drive signals as applied to individual pairs of electrodes of the medical device
Implementation Method 4
The measurement circuit may include a demodulator that is configured to simultaneously demodulate the response signal(s) for each unique drive frequency
Data Source
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AI summary
The present disclosure is directed to a system and method for measuring impedance across a plurality of electrodes and assessing proximity or contact between electrodes of a medical device and patient tissue. In one embodiment, contact is assessed individual electrodes and cardiac tissue using bipolar electrode complex impedance measurements. Initially, baseline impedance values are established for each of the individual electrodes based on the responses of the electrodes to the applied drive signals. After establishing the baseline impedance values a series of subsequent impedance values are measured for each electrode. For each electrode, each subsequent impedance value may be compared to a previous baseline impedance value for that electrode. If a subsequent impedance value is less than the baseline impedance value for a given electrode, the baseline impedance value may be reset to the subsequent impedance value. Such systems and method are particularly applicable to medical devices having numerous electrodes.