Multi-Channel MRI RF Coil Phase Alignment
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Solution Overview
Problem
Multi-channel magnetic resonance imaging (MRI) RF coils face challenges in maintaining a well-defined phase relationship between RF signals due to varying electrical lengths of transmission lines, especially in systems with four or more channels, leading to complex and cumbersome phase adjustments during manufacturing and installation.
Innovation Solution
The RF coil design ensures that the differences in electrical length between transmission lines are set to kλ/4, where k is an integer and λ is the wavelength of the RF signal, allowing for the use of standardized cables and eliminating the need for phase adjustments, with integrated impedance matching networks and phase shifting circuits to maintain a consistent phase relationship across all channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional birdcage resonators are directly fed at the coil ports using matching circuits, then power matching is achieved, but the electrical lengths of transmission lines vary causing complex phase adjustments during manufacturing and installation
Solution Approach 1:
The patent applies preliminary action by pre-configuring the electrical lengths of transmission lines to satisfy specific phase relationship conditions (kλ/4 differences) during the manufacturing stage. This eliminates the need for complex phase adjustments during installation and operation, as the phase relationships are established in advance through controlled transmission line length design.
Solution Approach 2:
The patent changes the electrical length parameter of transmission lines to satisfy specific phase relationship conditions. By controlling the length differences between transmission lines to be kλ/4, the system achieves well-defined phase relationships without requiring complex adjustment mechanisms during operation.
2Adaptability or versatility
If transmission lines of varying electrical lengths are used in multi-channel RF coils, then individual channel flexibility is improved, but phase relationship stability deteriorates
Solution Approach 1:
The patent controls the electrical length parameter of transmission lines to satisfy specific phase relationship conditions (kλ/4 differences). This parameter control maintains phase relationship stability while allowing flexibility in channel configuration through the systematic application of phase shifting circuits and impedance matching networks.
Solution Approach 2:
The patent introduces phase shifting circuits and impedance matching networks as intermediary components between the transmission lines and coil elements. These intermediaries enable independent adjustment of each channel's electrical characteristics while maintaining the overall phase relationship stability through controlled length differences.
3Manufacturing precision
If phase adjustments are performed during installation of multi-channel RF coils, then phase relationship accuracy is improved, but installation time and complexity increase
Solution Approach 1:
The patent performs preliminary configuration of transmission line electrical lengths to satisfy phase relationship conditions during manufacturing. This preliminary action eliminates the need for time-consuming phase adjustments during installation, as the system is pre-configured to achieve the desired phase relationships through controlled transmission line length design.
4Ease of operation
If standardized cables are used for all channels, then installation ease is improved, but phase relationship control becomes difficult
Solution Approach 1:
The patent introduces phase shifting circuits and impedance matching networks as intermediary components that compensate for the lack of individualized cable length control. These intermediaries enable precise phase relationship control even when standardized cables of identical lengths are used, by providing adjustable phase shift and impedance transformation at each channel.
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 design simplifies the electrical connection of RF sources to the MRI system, reduces electromagnetic interference, and facilitates easier installation by allowing the use of identical cables, maintaining a well-defined phase relationship and improving the orthogonality of the coil.
Implementation Method 1
each socket being adapted for receiving a plug for receiving from the outside an RF signal that then is provided via the respective first transmission line to the respective coil element
Implementation Method 2
To excite nuclear resonances, the RF coil generates a high frequency magnetic field at the nuclear resonance
Implementation Method 3
The needed strong DC magnetic field (B0 field) is typically generated by superconducting magnets
Implementation Method 4
In order to vary this field, such that it matches a given radio-frequency only at one position, a field gradient is generated using gradient coils
Data Source
AI summary
The present disclosure relates to a multi-channel magnetic resonance imaging RF coil (114) with at least four channels and comprising a coil element for each of the channels, the RF coil (114) further comprising for each coil element a socket (300-306) that is electrically coupled to said coil element via a respective first transmission line (209), each socket (300-306) being adapted for receiving a plug for providing an RF signal via the respective first transmission line (209) to the respective coil element, wherein with respect to a predefined RF signal the differences in electrical length between any of the transmission lines is kλ/4 where k is an integer and λ is the wavelength of the RF signal.