Acoustoelectric Mapping of Bio-Electric Fields
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Solution Overview
Problem
Current methods for mapping electrical current in living tissue lack sufficient spatial resolution and invasiveness, particularly in epilepsy surgery, where precise localization of brain tissue is crucial for surgical interventions.
Innovation Solution
A system utilizing the acoustoelectric effect, combining ultrasound transducers with recording electrodes to detect acoustoelectric voltage signals, allowing for non-invasive 2-D and 3-D mapping of current source densities in living tissue by focusing ultrasound waves to induce conductivity changes and measure voltage modulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If EEG recording from many electrodes on the skull is used, then coverage area is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent introduces an ultrasound wave as an intermediary to modulate tissue conductivity locally. This intermediary enables the recording electrodes to detect voltage modulations that are spatially encoded by the ultrasound focus position, thereby achieving high spatial resolution without requiring invasive electrodes or sacrificing coverage area.
Solution Approach 2:
The patent replaces the mechanical approach of placing many physical electrodes directly on or in the tissue with an acoustic field-based approach. Ultrasound waves modulate conductivity in a focused region, and this modulation is detected electrically, substituting mechanical electrode placement with acoustic field manipulation to achieve superior spatial resolution.
2Measurement precision
If subdural and depth electrodes are used, then spatial precision is improved, but invasiveness worsens
Solution Approach 1:
The ultrasound wave serves as a non-invasive intermediary that delivers spatially selective conductivity modulation to the target tissue region. This allows the external recording electrodes to achieve the spatial precision previously only attainable with invasive electrodes, by using acoustic focusing to encode position information in the detected voltage signal.
Solution Approach 2:
The patent substitutes the mechanical insertion of depth and subdural electrodes with an acoustic field-based measurement system. Ultrasound waves provide the necessary spatial selectivity without physical invasion, replacing the mechanical probing approach with acoustic modulation and electrical detection.
3Measurement precision
If ultrasound waves are focused to a small region, then spatial resolution is improved, but measurement sensitivity worsens
Solution Approach 1:
The patent changes the physical parameter being measured from direct voltage to ultrasound-modulated voltage. By detecting the modulation of voltage caused by ultrasound-induced conductivity changes, the system achieves high spatial resolution through ultrasound focusing while maintaining sensitivity through the use of external recording electrodes that detect the modulated signal.
Solution Approach 2:
The applied current field serves as an intermediary that, when modulated by the ultrasound wave, produces a detectable voltage signal. This intermediary current field enables the detection of small conductivity changes in the focused ultrasound region, maintaining measurement sensitivity even with high spatial resolution focusing.
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 provides high spatial resolution and sensitivity, enabling precise localization of current sources in living tissue, potentially improving surgical outcomes by reducing invasiveness and enhancing spatial selectivity in procedures like epilepsy surgery.
Implementation Method 1
Based on the acoustoelectric effect (AE effect or AEE), an interaction between local pressure and density, we assess whether ultrasound can be used to improve contrast and resolution of traditional electrical recording. An acoustic pressure wave P traveling in a biologic medium induces a local change in conductivity (given by d(ρ)/ρ=K1(dP))
Implementation Method 2
an ultrasound transducer emitting an ultrasound wave traveling along an ultrasound beam directed at a mapping field in a region of living tissue
Implementation Method 3
a plurality of recording electrodes positioned in contact with the living tissue operable to detect an acousticelectric voltage signal generated at a bioelectric current source and within a focal zone of said ultrasound beam
Data Source
AI summary
A current source density mapping system includes an ultrasound transducer emitting an ultrasound wave traveling along an ultrasound beam directed at a mapping field in a region of living tissue and an ultrasound pulser delivering a transmit pulse to said ultrasound transducer. The system includes a timing device producing controlled excitation of the transmit pulse; a plurality of recording electrodes positioned in contact with the living tissue detecting an acoustoelectric voltage signal generated at a bioelectric current source and within a focal zone of said ultrasound beam. An amplifier operatively connected to the recording electrodes amplifying the acoustoelectric voltage signal at a predetermined gain; and an analyzing component comprising a digitizer, a sampling device, a signal processor and a display unit operatively connected to the amplifier determining the location of the bioelectric current source by analyzing the acoustoelectric voltage signal detected by the recording electrodes in response to an interaction between the ultrasound wave and the presence of a current source in the mapping field.