RF Coil Testing Circuit Emulating Tissue Load
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in achieving high image homogeneity and quality, particularly at higher magnetic field strengths, due to dielectric resonances and tissue-like phantoms that distort the B1 field, while phantoms with low dielectric constants do not accurately simulate human tissue.
Innovation Solution
A magnetic resonance coil testing arrangement combining a phantom with an electric circuit that emulates the electrical load of organic tissue, using passive or active components to adjust the coil's load and minimize dielectric resonances, allowing for accurate simulation of human tissue-like conditions without distorting the B1 field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom with dielectric constant similar to human tissue is used, then the electrical load of RF coils is accurately simulated, but dielectric resonances are generated which greatly perturb the B1 field and degrade image homogeneity
Solution Approach 1:
The patent extracts the harmful dielectric resonance properties from the phantom material while retaining the electrical load simulation function. By using a phantom with low dielectric constant instead of tissue-mimicking dielectric constant, the harmful resonances are eliminated while the electrical load is still accurately simulated through the coupled electric circuit.
Solution Approach 2:
An electric circuit is introduced as an intermediary component that couples to the RF coil to simulate the electrical load of human tissue. This intermediary allows the phantom to have low dielectric constant (avoiding resonances) while the electric circuit provides the appropriate electrical load characteristics through impedance matching networks.
2Object-affected harmful factors
If a phantom with low dielectric constant is used, then dielectric resonances are avoided and B1 field homogeneity is maintained, but the electrical load of RF coils is not accurately simulated
Solution Approach 1:
The electric circuit acts as a mediator that bridges the gap between the low dielectric constant phantom and the required tissue-mimicking electrical load. The circuit includes impedance matching networks and variable components that adjust the electrical characteristics to match human tissue while the phantom itself maintains low dielectric constant to avoid resonances.
Solution Approach 2:
The patent uses variable electrical components (such as variable capacitors and inductors) in the electric circuit to dynamically adjust the electrical load parameters. This allows precise control of the electrical characteristics to match different tissue types while maintaining compatibility with the low dielectric constant phantom.
3Measurement precision
If phantoms with tissue-like dielectric properties are used at high magnetic field strengths, then electrical load simulation is improved, but image quality and homogeneity are degraded due to Eddy currents and field attenuation
Solution Approach 1:
The patent separates the electrical load simulation function from the dielectric properties of the phantom material. By extracting the electrical load simulation to a dedicated electric circuit, the phantom can use low dielectric constant material that does not generate harmful Eddy currents or field attenuation, while the circuit provides accurate electrical load characteristics.
Solution Approach 2:
The electric circuit serves as an intermediary that provides the electrical load characteristics of human tissue without requiring the phantom material to have tissue-mimicking dielectric properties. This eliminates the source of Eddy currents and field attenuation while maintaining accurate electrical load simulation through circuit impedance matching.
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 solution enables the simulation of various tissue-like conditions, improving image quality and coil performance by accurately emulating the electrical load of human tissue, reducing image artifacts, and allowing for calibration and tuning of MRI systems across different magnetic field strengths.
Implementation Method 1
the electric circuit is adapted for inducing the electrical load to the RF coil such that the electrical load is equivalent to an electrical load of organic tissue at the magnetic resonance frequency of the RF coil
Implementation Method 2
The basis of both NMR and MRI is the fact, that atomic nuclei with non-zero spin have a magnetic moment. The nuclear spin of elementary particles can resonate at a resonance frequency, if a strong DC magnetic field is applied.
Implementation Method 3
In order to vary these fields, such that it matches a given radio frequency only at one position, a field gradient is generated using gradient coils.
Implementation Method 4
To excite nuclear resonances, the RF coil generates a high frequency magnetic field at the nuclear resonance.
Implementation Method 5
To measure nuclear resonances, 'sensor' or 'receiver' coils are placed close to the region of interest
Implementation Method 6
The needed strong DC magnetic field (B0 field) is typically generated by superconducting magnets.
Implementation Method 7
using passive or active components to adjust the coil's load and minimize dielectric resonances
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The invention relates to a magnetic resonance coil testing arrangement (150) comprising an electric circuit (152; 302) for emulating an electrical load to a magnetic resonance coil, wherein the electric circuit (152; 302) is adapted for emulating an electrical load corresponding to an electrical load induced by organic tissue at the magnetic resonance frequency of the magnetic resonance coil.