Electromagnetic Impedance Tomography Sub-voxel Localization
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Solution Overview
Problem
Conventional electromagnetic impedance tomography and spectroscopy methods face limitations in accurately characterizing and selecting specific volumes beneath the surface of materials under test, particularly in distinguishing between different tissue types like blood and skin tissue, due to limitations in depth penetration and impedance measurement precision.
Innovation Solution
The use of a four-terminal electrode array system that transmits electromagnetic impedance signals and obtains return readings to calculate physical properties of selected sub-volumes by comparing them to expected impedance responses, employing Volume Differentiation and Removal (VDR) methodology to isolate and characterize specific volumes based on impedance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional two-terminal sensor arrays are used for electromagnetic impedance measurements, then the device complexity is reduced, but the measurement precision and ability to distinguish between different tissue types deteriorates
Solution Approach 1:
The patent divides the measurement system into four separate terminals (two current electrodes and two voltage electrodes) instead of using a simple two-terminal configuration. This segmentation allows independent control of current injection and voltage measurement, eliminating the influence of contact impedance and improving measurement precision for distinguishing different tissue types.
Solution Approach 2:
The patent introduces intermediate processing steps including impedance normalization, differentiation from expected responses, and volumetric localization algorithms. These intermediary processes act as mediators between the raw impedance measurements and the final tissue characterization, enhancing the precision of distinguishing blood-rich areas from other tissues.
2Length of stationary object
If electromagnetic impedance signals are transmitted at greater depths into the material under test, then the measurement coverage is improved, but the impedance measurement precision deteriorates due to signal attenuation
Solution Approach 1:
The patent employs periodic electromagnetic impedance signals transmitted at multiple frequencies across a spectrum. This periodic action at varying frequencies allows the signals to penetrate to different depths, with lower frequencies penetrating deeper and higher frequencies providing surface detail, thus maintaining measurement precision across different depth ranges.
Solution Approach 2:
The patent changes the frequency parameter of the electromagnetic impedance signals to optimize depth penetration and measurement precision. By sweeping through a range of frequencies, the system can adjust the penetration depth dynamically, with each frequency providing optimal measurement precision for specific depth ranges within the material under test.
3Measurement precision
If multiple electromagnetic impedance signals are transmitted and analyzed to characterize selected sub-volumes, then the measurement precision for specific volumes is improved, but the loss of time increases due to multiple measurements
Solution Approach 1:
The patent performs preliminary transmission of multiple electromagnetic impedance signals across a frequency spectrum to build a complete impedance spectrum for each volume element before selection. This preliminary action creates a comprehensive database of impedance characteristics that enables rapid identification and characterization of selected sub-volumes without requiring additional measurement time.
Solution Approach 2:
The patent transmits electromagnetic impedance signals at more frequencies than strictly necessary for basic characterization, collecting excessive data that can then be selectively processed. This excessive action provides redundant information that speeds up the identification and characterization of selected sub-volumes, reducing the time required for precise physical property determination.
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 precise characterization of physical properties within selected sub-volumes, such as blood-rich areas, by differentiating impedance values and correlating them with desired physical attributes, improving the accuracy and depth of measurement in materials like human tissue.
Implementation Method 1
instructing a sensor system to transmit a plurality of electromagnetic impedance signals into the MUT from a surface of the MUT; obtaining a plurality of sets of return electromagnetic impedance readings from the sensor system, including impedance information about the MUT
Data Source
AI summary
Approaches include selecting a desired location for the measurement of electromagnetic spectroscopic impedance data for correlation with a physical property of a material under test (MUT) with electromagnetic impedance tomography. The MUT is first characterized tomographically with a series of four-terminal electrode patterns at a single current frequency. Measured and computed values of electromagnetic impedance for the voxels and sub-voxels of the MUT are determined. The sub-voxel with a targeted value of impedance is selected and matched with the specific four-terminal electrode pattern related to that sub-voxel. The spectrographic electromagnetic impedance measurements are made across a range of frequencies for the selected sub-voxel, using all of the four-terminal electrode patterns required to compute the tomographic impedance value of the selected sub-voxel. The computed spectrographic electromagnetic impedance value for the selected sub-voxel is then correlated to a physical property of the MUT.