Pulsed Electrode System for Brain Tissue Conductivity Estimation
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Solution Overview
Problem
Existing methods for measuring electrical conductivity in biological tissues, particularly in the brain, fail to accurately account for biophysical processes at the electrode-tissue interface and interaction mechanisms between the electric field and brain tissue.
Innovation Solution
A system and method that utilize at least two electrodes to deliver local pulsed electrical stimulation, coupled with a predefined analytic model that accounts for contributions from the electrode-electrolyte interface, allowing for a fast and reliable estimation of electrical conductivity in biological tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard bioimpedance measurement methods are used, then the measurement process is simple, but the measurement precision is poor due to failure to account for electrode-tissue interface effects
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing impulse response functions for various tissue conductivities in a lookup table before actual measurement. During measurement, the system retrieves the appropriate impulse response from memory and compares it with the measured signal, avoiding complex real-time calculations. This resolves the contradiction by maintaining high measurement precision through sophisticated modeling while keeping the actual measurement process simple and fast.
Solution Approach 2:
The patent uses copying by creating a computational model (impulse response function) that replicates the physical electrode-tissue interface behavior. Instead of directly measuring complex interface effects, the system generates synthetic impulse responses that copy the expected signal characteristics for different tissue conductivities, then matches the measured signal against these copies to determine the actual conductivity.
2Measurement precision
If complex biophysical modeling is applied to account for electrode interface effects, then the measurement precision improves, but the calculation time increases
Solution Approach 1:
The patent pre-calculates impulse response functions for a range of tissue conductivities and stores them in memory before actual measurements. During the measurement process, the system performs a simple lookup and comparison rather than solving complex differential equations in real-time. This resolves the contradiction by shifting the computational burden to a pre-processing stage, making real-time measurements both precise and fast.
Solution Approach 2:
The system uses periodic impulse stimulation to elicit transient responses from the tissue. By applying repeated impulse currents and analyzing the transient voltage responses, the system can efficiently characterize tissue conductivity through time-domain analysis, reducing the measurement time while maintaining precision through the use of the pre-computed impulse response library.
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
The method provides absolute changes in brain tissue conductivity, outperforming standard bioimpedance measurements by accurately accounting for electrode-tissue interface effects, thereby enhancing diagnostic capabilities in neurological disorders like epilepsy.
Implementation Method 1
an analytical model of the electric field generated by the electrodes
Implementation Method 2
a double layer model generated at the electrode-medium interface
Implementation Method 3
an acquisition unit comprising a signal amplifier configured to acquire and amplify an electric potential recorded by the electrodes
Data Source
Figure 1~2
Figure 3(a)~4
Figure 5
AI summary
This system (1), intended for the estimation of at least one physical parameter of a region of a medium (M) comprising at least one electrolyte, comprises at least two electrodes (2), i.e. at least one working electrode and one counter electrode; a current generator (3) configured to deliver to the electrodes (2) a train of electric pulses of current, each electric pulse having a pulse duration; a computer-readable memory (4) comprising at least one predefined analytic model of an electric potential, between the working electrode and the counter electrode, as a function of time, receiving as inputs at least the current and the pulse duration and comprising at least one physical parameter of the medium (M) to be estimated; an acquisition unit (5) comprising a signal amplifier configured to acquire and amplify an electric potential recorded by the electrodes; and a processor (6) comprising a stimulation module (61) configured to control the current generator (3) so as to deliver a biphasic charge-balanced current during a stimulation duration; an acquisition module (62) configured to trigger an acquisition of an electric potential variation as a function of time during a time window comprised in the stimulation duration; and a calculation module (63) configured to receive the acquired electric potential variation of the region of the medium (M) as a function of time, fit the acquired electric potential variation using the predefined analytic model, and output a value of the physical parameter obtained from the fitting of the predefined analytic model.