RF Drive Circuit Phase Shifting for MRI Field Uniformity
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Solution Overview
Problem
Current RF transmitting coils in MRI systems face challenges in generating a uniform RF field due to limitations in the number of coil legs, leading to reduced field uniformity and increased costs associated with multiple RF amplifiers.
Innovation Solution
A drive circuit for RF transmitting coils that includes a controller, digital-to-analogue converter, RF amplifier, power divider, and phase shifters, which generates multiple signals with equal power and adjusts phases to ensure uniform signal distribution across feed ports, reducing the need for multiple RF amplifiers and improving field uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple RF amplifiers are used to drive multiple coil legs, then the RF field uniformity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent segments the RF signal distribution function by using a power divider to split the signal from a single RF amplifier into multiple paths, each path then using phase shifters to adjust the phase for different coil legs. This segmentation allows uniform RF field generation without requiring multiple RF amplifiers, thus resolving the contradiction between field uniformity and device complexity.
Solution Approach 2:
The patent employs phase shifters that can dynamically adjust the phase of RF signals for each coil leg independently. This dynamic phase adjustment capability allows the system to maintain uniform RF field distribution across all coil legs while using a single RF amplifier, thereby improving field uniformity without increasing the number of amplifiers.
2Manufacturing precision
If the number of coil legs is increased to improve field uniformity, then the RF field uniformity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent makes a single RF amplifier serve multiple functions by using it to drive multiple coil legs through a power divider and phase shifters. This multi-functionality allows the system to maintain uniform RF field generation without increasing the number of coil legs or RF amplifiers, thus resolving the contradiction between field uniformity and device complexity.
Solution Approach 2:
The patent changes the phase parameter of RF signals for each coil leg using phase shifters, allowing uniform RF field distribution to be achieved by adjusting signal parameters rather than increasing the number of coil legs. This parameter-based approach resolves the contradiction by maintaining field uniformity without increasing structural complexity.
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
The proposed drive circuit enhances the uniformity of the RF field generated by the RF transmitting coil while reducing the number of RF amplifiers required, thereby lowering costs and improving the signal-to-noise ratio.
Implementation Method 1
a digital to analogue converter (DAC) coupled with the controller and configured to perform D/A conversion for the drive signal to output an analogue drive signal
Implementation Method 2
a RF amplifier coupled with the DAC and configured to amplify the analogue drive signal to obtain an amplified analogue drive signal
Implementation Method 3
a power divider coupled with the RF amplifier and configured to generate at least three signals based on the amplified analogue drive signal, wherein the power divider has at least three output ports each configured to output a respective signal of the at least three signals
Implementation Method 4
a plurality of phase shifters coupled with the power divider, each of the phase shifters being coupled with a respective output port of the at least three output ports and configured to adjust a phase of the respective signal output by the respective output port to obtain a phase adjusted signal
Data Source
AI summary
A drive circuit of a radio-frequency (RF) transmitting coil and a magnetic resonance imaging (MRI) device are provided. According to an example, the drive circuit includes a controller, a digital-to-analogue converter (DAC) coupled with the controller, a RF amplifier coupled with the DAC, a power divider coupled with the RF amplifier, and a plurality of phase shifters respectively coupled with at least three output ports of the power divider.