MRI-Based Electrical Property Mapping Using RF Field Patterns
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Solution Overview
Problem
Current techniques for noninvasive mapping of electrical properties of tissues and materials face limitations in spatial resolution, robustness, and the ability to provide detailed information about the internal distribution of electrical conductivity and permittivity, which hinders applications in diagnostics and other fields.
Innovation Solution
The proposed solution involves an apparatus and method using a combination of RF coils and MRI to generate electromagnetic field patterns and process MR images to determine electrical properties, employing Maxwell equations and parallel transmit/receive systems to constrain and resolve electrical property distributions, even with corrupted phase data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface-based electrical impedance tomography techniques are used, then noninvasive measurement is achieved, but spatial resolution and measurement precision are limited
Solution Approach 1:
The patent uses MRI as an intermediary tool to noninvasively measure internal electromagnetic fields (B1+ and B1-) that serve as mediators between the external RF fields and the electrical properties. By measuring these intermediary field quantities via MRI phase and magnitude data, the system achieves high-resolution electrical property mapping without direct contact with tissues, resolving the contradiction between noninvasive measurement and measurement precision.
2Measurement precision
If injected-current-based techniques are used, then interior electrical property data is obtained, but invasive measurement and patient safety concerns arise
Solution Approach 1:
The patent replaces the mechanical/electrical injection method with an electromagnetic field-based measurement approach. Instead of injecting currents through electrodes, the system uses externally applied RF electromagnetic fields and measures the induced internal fields via MRI. This substitution eliminates invasive contacts and associated safety risks while maintaining the ability to detect interior electrical properties.
3Measurement precision
If MRI-based electromagnetic field measurement is used, then noninvasive interior field detection is achieved, but phase data corruption and measurement robustness issues occur
Solution Approach 1:
The patent implements a feedback mechanism by acquiring both phase and magnitude data from MRI measurements, then using iterative optimization algorithms that compare measured data with simulated data based on estimated electrical properties. The algorithm continuously refines the electrical property estimates by feeding back the difference between measured and simulated observations, thereby correcting for phase data corruption and improving measurement reliability.
Solution Approach 2:
The system changes measurement parameters by acquiring data at multiple RF frequencies and using both phase and magnitude information. By varying the frequency and using multiple measurement parameters, the system creates an over-determined system that allows robust estimation of electrical properties even when individual phase measurements are corrupted, thereby improving reliability.
4Measurement precision
If multiple RF measurements at different frequencies are performed, then electrical property mapping accuracy is improved, but measurement time and productivity decrease
Solution Approach 1:
The patent applies partial action by selecting a limited number of strategically chosen RF frequencies rather than measuring across the entire spectrum. The optimization algorithm uses these partial measurements at discrete frequencies to reconstruct the complete electrical property distribution, achieving accurate mapping without the excessive time required for continuous frequency scanning, thus balancing precision and productivity.
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 noninvasive, high-resolution mapping of electrical properties, facilitating improved diagnostics and characterization of materials, and enabling accurate monitoring and correction of energy deposition in MRI, while addressing the limitations of existing techniques.
Implementation Method 1
at least one transmitter configured to generate a plurality of electromagnetic field distribution patterns directed at an object
Implementation Method 2
a magnetic resonance imaging (MRI) apparatus configured to produce at least one image of the object using at least one of a magnitude or a phase modulated by the electromagnetic field distribution patterns
Data Source
AI summary
An assembly for determining at least one electrical property of an object. The assembly includes at least one transmitter that can generate a plurality of electromagnetic field distribution patterns directed at an object. The assembly also includes a data apparatus with an MRI apparatus and a data processor. The MRI apparatus can produce at least one image of the object using a magnitude or a phase modulated by the electromagnetic field distribution patterns. The processor can then process data associated with the object to determine the at least one electrical property the object.