Multi-Frequency Tissue Wetness Detection via Resistivity Ratios
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Solution Overview
Problem
Current methods for determining tissue wetness, particularly lung wetness, are unreliable and inaccurate due to their dependence on body geometry and electrolyte balance, leading to low accuracy and variability in measurements.
Innovation Solution
The use of a non-invasive system with an array of electrodes that applies currents at multiple frequencies to determine the relative spatial change in subsurface resistivities, providing a geometry-independent measure of tissue wetness through the calculation of relative percent differences in resistivity between high and low frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-frequency electrical impedance methods are used to determine tissue wetness, then the measurement process is simple, but the accuracy and reliability are low due to dependence on body geometry and electrolyte balance
Solution Approach 1:
The patent applies parameter changes by using multiple current frequencies (at least two different frequencies) instead of a single frequency. This allows the system to determine relative percent differences in resistivity between frequencies, which eliminates dependence on body geometry and electrolyte balance. The change in frequency parameter enables accurate tissue wetness measurement without requiring complex geometric corrections.
2Reliability
If multi-frequency electrical impedance tomography is used to improve measurement accuracy, then tissue wetness determination becomes more reliable, but the device complexity and computational requirements increase significantly
Solution Approach 1:
The patent extracts only the essential information needed for tissue wetness determination by calculating relative percent differences in resistivity between frequencies. Instead of performing full electrical impedance tomography reconstruction, the system extracts the specific parameter (relative resistivity difference) that directly correlates with tissue wetness, eliminating the need for complex geometric modeling and reducing computational requirements while maintaining high reliability.
3Ease of operation
If geometry-dependent electrical impedance methods are used, then the measurement setup is straightforward, but the results show high variability due to differences in body habitus and electrode placement
Solution Approach 1:
The patent uses parameter changes (multi-frequency measurement) to eliminate geometry dependence. By measuring resistivity at multiple frequencies and calculating the relative percent difference, the system obtains a parameter that is independent of body geometry and electrode placement. This maintains ease of operation while dramatically improving measurement consistency across different subjects and measurement conditions.
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 allows for accurate and reproducible monitoring of tissue wetness, including lung fluid status, independent of subject body geometry, enabling effective management of heart failure and other conditions by providing a reliable index of extravascular interstitial fluid levels.
Implementation Method 1
determining the relative spatial change in subsurface resistivities across frequencies for a region of tissue beneath an array of electrodes placed on the surface of a body
Data Source
AI summary
Non-invasive devices and systems to determine tissue wetness/hydration based on relative changes in subsurface resistivities in tissue below an electrode array applied to a human body across different frequencies. For example, these a sensor including arrays of current-injecting and voltage-sensing electrodes may be placed on a subject's back to determine lung wetness. Systems and methods for determining tissue water content, systems and methods for determining lung wetness, sensors for determining relative changes in subsurface resistivities across frequencies and systems and methods to determine which arrays of electrodes in a sensor to use to determine relative changes in subsurface resistivities across frequencies are all described.