MRI-Based SAR Determination via Thermal Inversion
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Solution Overview
Problem
Existing methods for determining the specific absorption rate (SAR) of radio frequency (RF) radiation, such as using electric field probes, suffer from translational delays and errors due to point-by-point movement, and temperature-based assessments require prolonged heating to detect changes, which can lead to inaccuracies.
Innovation Solution
A system and method that utilize thermal information, including temperature difference maps from magnetic resonance imaging, to determine SAR through inversion of the bioheat equation, using a finite difference approach and L1 weighted norm minimization, to calculate both local and spatially averaged SAR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric field probes are used to measure SAR point-by-point in a grid-like fashion, then measurement coverage can be achieved, but translational delays and translational errors occur due to mechanical movement
Solution Approach 1:
The patent replaces the mechanical probe movement system with an MRI-based thermal mapping system. Instead of physically moving electric field probes through a grid pattern, the invention uses MRI to capture temperature distributions across the entire phantom volume simultaneously, eliminating mechanical translational delays and errors while maintaining comprehensive measurement coverage
Solution Approach 2:
The patent transitions from one-dimensional point-by-point probe measurements to three-dimensional volumetric temperature mapping using MRI. This dimensional expansion allows simultaneous capture of temperature data throughout the entire phantom volume, eliminating the need for mechanical translation and providing comprehensive SAR distribution information
2Measurement precision
If heating duration is kept low to minimize heat diffusion, then temperature distribution accuracy is improved, but detectable temperature change becomes difficult for low power RF emitting devices
Solution Approach 1:
The patent employs iterative feedback between temperature measurements and SAR calculations. Multiple temperature maps are acquired at different time points, and the SAR distribution is repeatedly calculated and refined based on the observed temperature evolution, allowing accurate SAR determination even when individual temperature changes are small
Solution Approach 2:
The patent performs preliminary measurement of thermal properties (conductivity, heat capacity, perfusion) before the actual SAR measurement experiment. These pre-measured thermal parameters are then used in the heat diffusion equation to accurately interpret small temperature changes and calculate SAR, enabling detection of temperature changes from low power devices
3Power
If heating duration is prolonged to detect temperature change in low power devices, then detectable temperature change is achieved, but heat diffusion increases causing inaccuracies
Solution Approach 1:
The patent uses iterative feedback where temperature maps are acquired at multiple time points during heating, and SAR calculations are repeatedly updated based on the observed temperature evolution. This feedback loop allows the system to compensate for heat diffusion effects by comparing temperature changes against the heat diffusion model predictions
Solution Approach 2:
The patent changes the approach from trying to minimize heating duration to instead measuring thermal properties (conductivity, heat capacity, perfusion) and using these parameters in a heat diffusion model. By incorporating these parameter changes into the calculation framework, the system can accurately determine SAR even when heat diffusion occurs during prolonged heating
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 efficient calculation of SAR, reducing errors and providing precise measurements of RF radiation absorption, even with short heating durations, by leveraging thermal properties and temperature changes.
Implementation Method 1
temperature difference maps from magnetic resonance imaging
Implementation Method 2
Exposure to the RF radiation can result in an increased heating of tissue via Joule and Dielectric heating mechanisms
Implementation Method 3
Exposure to the RF radiation can result in an increased heating of tissue via Joule and Dielectric heating mechanisms
Data Source
AI summary
Systems, methods and computer-accessible mediums for determining a specific absorption rate (SAR) of a radio frequency (RF) radiation on an object(s) can be provided, which can, for example hardware arrangement configured to receive thermal information for a portion(s) of the at least one object, and determine the SAR based on the thermal information.