Parallel-Series RF Coil Arrangement for MRI Shim Inductance
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Solution Overview
Problem
Existing magnetic resonance tomography (MRT) systems face challenges in compensating for non-homogeneities in the static magnetic field (B0), which affect data quality, and using individual RF loops as shim coils results in low inductance and potential safety issues due to high currents.
Innovation Solution
A coil arrangement where multiple RF loops are connected in parallel for RF signals and in series for direct current signals, utilizing a multilayer board structure with capacitors and inductors to increase inductance and reduce ohmic losses, allowing for enhanced sensitivity and reduced current requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If individual RF loops are used as shim coils, then the structure is simple, but the inductance is low and high currents are required causing safety issues
Solution Approach 1:
The patent combines multiple RF loops into a single coil arrangement where the loops are connected in parallel for RF signals and in series for DC shim currents. This merging approach increases the effective inductance for DC currents, allowing shim operation at lower, safer current levels while maintaining the functional simplicity of a unified coil structure.
2Reliability
If multiple RF loops are connected in series for DC signals, then the inductance increases, but the device complexity increases
Solution Approach 1:
The coil arrangement is designed to serve multiple functions through a single unified structure. The same coil assembly that functions as RF receive antennas also serves as the shim coil, with connection switches that reconfigure the same physical loops for different purposes (parallel for RF, series for DC). This eliminates the need for separate shim coils and reduces overall device complexity.
Solution Approach 2:
The patent employs dynamic reconfiguration of the coil connections using switches controlled by a control unit. The connection topology changes based on the operational mode: during RF acquisition, loops are connected in parallel for optimal RF performance; during shim adjustment, the same loops are reconfigured in series to increase inductance. This dynamic adaptability allows a single structure to optimize both functions.
3Device complexity
If RF loops are used for both RF reception and shim functions, then the device complexity is reduced, but the sensitivity of receive antennas may be affected
Solution Approach 1:
The system dynamically reconfigures the coil connections based on operational requirements. During RF signal reception, the loops are connected in parallel to maximize sensitivity and signal-to-noise ratio. During shim current application, the same loops are reconfigured in series to provide adequate inductance. This temporal separation of functions through dynamic switching preserves sensitivity while enabling dual functionality.
Solution Approach 2:
The coil arrangement alternates between different connection configurations in periodic cycles corresponding to the MRI pulse sequence timing. Between RF excitation and detection periods, the system periodically switches to series configuration for shim adjustments, then returns to parallel configuration for RF reception. This periodic reconfiguration allows both functions to operate optimally at different times without compromising overall system performance.
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 configuration improves the sensitivity of receive antennas, reduces ohmic losses, and minimizes current requirements, effectively compensating for magnetic field non-homogeneities while ensuring patient safety and comfort.
Implementation Method 1
A coil arrangement for a magnetic resonance tomography device is proposed, wherein a plurality of antennas At1, At2, At3 which, for RF signals, are connected in parallel to one another, are connected in series to one another for direct current signals
Implementation Method 2
utilizing a multilayer board structure with capacitors and inductors to increase inductance and reduce ohmic losses
Implementation Method 3
utilizing a multilayer board structure with capacitors and inductors to increase inductance and reduce ohmic losses
Implementation Method 4
Magnetic resonance devices (MRTs) for examining objects or patients using magnetic resonance tomography
Data Source
AI summary
A coil arrangement for a magnetic resonance tomography device includes at least two antennas connected in parallel to one another for RF signals and connected in series with one another for direct current signals.