Phase Contrast MRI for Induced RF Current Measurement
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Solution Overview
Problem
Current methods for measuring induced radio frequency currents in conductive structures during MRI scans are inefficient, often requiring lengthy procedures, limited to single-point measurements, and not applicable for in vivo applications, leading to potential temperature rises and safety concerns.
Innovation Solution
A method using phase contrast MRI techniques to automatically quantify induced RF currents in conductive structures by analyzing phase artifacts in a single MRI image, allowing for rapid and flexible measurements without manual intervention or hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fiber optic temperature probe is used to measure temperature, then measurement accuracy is improved, but measurement time increases and in vivo application becomes impossible
Solution Approach 1:
The patent replaces the mechanical fiber optic temperature probe with a magnetic resonance imaging (MRI) based measurement system. The MRI system uses magnetic fields and radio frequency pulses to measure temperature changes in tissue surrounding conductive structures, eliminating the need for physical probe insertion while maintaining measurement capability through non-contact thermal mapping.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the MRI system's existing magnetic resonance signals to indirectly measure temperature changes. Instead of directly measuring temperature with a probe, the system detects changes in the magnetic resonance properties of tissue that correlate with temperature, providing a non-invasive thermal measurement method.
2Measurement precision
If fiber optic temperature probe is used, then temperature measurement is accurate, but spatial coverage is limited to one or a few points
Solution Approach 1:
The patent transitions from point-based temperature measurement (1D/0D) to volumetric temperature mapping (3D). The MRI system acquires temperature data across the entire imaged volume, allowing simultaneous measurement of temperature at multiple locations throughout the tissue surrounding the conductive structure, thereby providing comprehensive spatial coverage.
Solution Approach 2:
The MRI system performs multiple functions simultaneously: it maintains its primary imaging capability while also providing temperature measurement across the entire field of view. This multi-functional approach allows the same system to generate both anatomical images and thermal maps, covering the full spatial region of interest without requiring separate measurement devices.
3Adaptability or versatility
If induced current is measured to predict SAR distribution, then in vivo applicability is improved, but measurement complexity increases
Solution Approach 1:
The patent utilizes the MRI system's existing transmit and receive capabilities to perform both imaging and induced current measurement functions. The same magnetic resonance sequences used for anatomical imaging are adapted to detect the magnetic field perturbations caused by induced currents, eliminating the need for separate specialized measurement hardware and reducing overall system complexity.
Solution Approach 2:
The MRI system measures induced currents using its own inherent magnetic fields and signal detection capabilities. The transmit magnetic field (B1) that is already present during MRI operation induces currents in conductive structures, and the same receive coils used for imaging detect the resulting magnetic field changes, allowing the system to self-measure without external sensors or additional complex equipment.
4Reliability
If reverse polarized transmission is used to detect induced current, then detection reliability is improved, but quantitative measurement capability is lost
Solution Approach 1:
The patent implements a feedback-based quantitative measurement approach by comparing the measured phase artifacts with expected phase patterns from forward polarized transmission. The system uses the known relationship between transmit polarization and induced current direction to calculate the magnitude and phase of induced currents, transforming qualitative detection into quantitative measurement through systematic comparison and analysis.
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
Enables safe and efficient measurement of induced RF currents, reducing testing time and allowing for safer MRI procedures by predicting heating behavior, which can be applied to various medical devices and configurations.
Implementation Method 1
The induced RF current flowing on the wire during MRI creates a magnetic field in the vicinity of the wire, at the Larmor frequency (excitation frequency of the magnetic field). This magnetic field couples to the transmit magnetic field
Implementation Method 2
This magnetic field couples to the transmit magnetic field, causing a noticeable artifact in both magnitude and phase MR images containing the wire
Data Source
AI summary
A method for automatically measuring currents induced on conducting structures positioned in the bore of a magnetic resonance imaging (“MRI”) scanner using a single magnetic resonance image is provided. A conductive structure is positioned within the bore of the MRI scanner during imaging. When the MRI system is transmitting an RF field, a current is induced in the conductive structure. The current creates a magnetic field at the Larmor frequency, which couples to the RF magnetic field in the vicinity of the conductive structure. The modified magnetic field results in an artifact being generated in phase images. The artifact in the phase image is then analyzed to determine the current induced in the conductive structure.