MRI Multi-Channel Impedance Matching Network
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems with multiple radio-frequency transmit channels face inefficiencies due to varying patient loading conditions and radio-frequency coupling between antenna elements, leading to suboptimal power usage and image quality.
Innovation Solution
The system employs an adjustable impedance matching network that characterizes radio-frequency properties to optimize power distribution across antenna elements, using a radio-frequency model to adjust impedance matching in real-time based on measured properties and patient-specific conditions, thereby minimizing reflections and coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-element antennas are tuned to function with a variety of subjects, then versatility is improved, but power efficiency deteriorates due to varying loading conditions
Solution Approach 1:
The patent implements dynamically adjustable impedance matching networks with variable capacitors and inductors that can be tuned in real-time based on the subject's loading conditions. This dynamic adjustment allows the antenna system to maintain optimal power efficiency across different patient sizes and positions while preserving versatility.
Solution Approach 2:
The system changes electrical parameters (impedance values, capacitance, inductance) of the matching networks based on measured radio-frequency properties. By adjusting these parameters according to the specific loading conditions, the system optimizes power efficiency for each subject while maintaining the ability to work with a variety of patients.
2Power
If radio-frequency power is applied to antenna elements, then imaging capability is improved, but harmful coupling between elements increases
Solution Approach 1:
The patent measures the radio-frequency coupling between antenna elements and uses this information to adjust the impedance matching networks. By converting the harmful coupling effect into useful information, the system compensates for the coupling through parameter adjustments, allowing full utilization of radio-frequency power while eliminating the harmful interference.
Solution Approach 2:
The system implements a feedback mechanism where radio-frequency properties including coupling between elements are measured and used to adjust the impedance matching networks. This closed-loop control allows the system to maintain optimal performance by continuously compensating for harmful coupling effects while delivering the necessary radio-frequency power for imaging.
3Loss of energy
If impedance matching is adjusted for different drive vectors, then power efficiency is improved, but device complexity increases
Solution Approach 1:
The patent divides the impedance matching system into multiple independent adjustable matching networks, each associated with a specific antenna element. This segmentation allows independent optimization of each element's impedance matching based on the drive vector, improving overall power efficiency while keeping each individual matching network relatively simple and manageable.
Solution Approach 2:
The system uses a universal adjustable impedance matching network design that can handle multiple drive vectors and different imaging scenarios. By creating a multi-functional matching network that can adapt to various conditions, the system improves power efficiency across different operations without requiring separate complex matching networks for each scenario.
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 enhances power efficiency and image quality by ensuring proper impedance matching and power distribution, reducing reflected power and improving homogeneity of the B1 field, even with varying patient sizes and positions.
Implementation Method 1
an adjustable impedance matching network which characterises radio-frequency properties of the antenna elements and uses a radio-frequency model to adjust impedance matching
Implementation Method 2
Radio Frequency (RF) pulses generated by a transmitter or amplifier and an antenna cause perturbations to the local magnetic field and can be used to manipulate the orientation of the nuclear spins relative to the B0 field
Implementation Method 3
A magnetic field is used in Magnetic Resonance Imaging to align the nuclear spins of atoms as part of the procedure for producing images within the body of a patient. This magnetic field is referred to as the B0 field
Implementation Method 4
The radio-frequency antenna comprises multiple antenna elements. There is also radio-frequency coupling between the individual antenna elements
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The Magnetic Resonance Imaging (MRI) system includes a radio-frequency transmitter with multiple transmit channels. The MRI system includes an impedance matching network (320, 1402, 1502, 1602) for matching the radio-frequency transmitter to a remotely adjustable radio-frequency antenna (310, 1504, 1602) with multiple antenna elements (312, 314, 316, 318, 1404). The MRI system includes a processor (336) for controlling the MRI system. The execution of the instructions by the processor causes it to: measure (100, 200) a set of radio-frequency properties (352) of the radio-frequency antenna, calculate (102, 202) a matching network command (354) using the set of radio-frequency properties and a radio frequency model (366), and adjust (104, 204) the impedance matching network by sending the matching network command to the impedance matching network, thereby enabling automatic remote impedance matching.