MRI RF array decoupling method with magnetic wall distributed filters

Area of Science:

• Medical Imaging
• Electromagnetics
• RF Engineering

Background:

• Ultra-high field (≥ 7T) magnetic resonance imaging (MRI) faces radio-frequency (RF) challenges.
• Multi-channel transmit coil arrays are crucial for parallel RF transmission and tailored excitation.
• Mutual coupling between coils in RF arrays hinders performance.

Purpose of the Study:

• To introduce and validate a novel decoupling method for multi-channel RF transmit arrays.
• To suppress mutual coupling in RF arrays using a bandstop filter, termed "magnetic wall" (MW).
• To analyze and experimentally verify the performance of the MW decoupling technique at 7T.

Main Methods:

• A novel bandstop filter ("magnetic wall") inspired by periodic resonator designs was implemented.
• Equivalent circuit analysis was used to model both magnetic and electric coupling.
• Frequency- and time-domain full-wave simulations were performed.
• Experimental validation was conducted on a three-coil 7T array setup.

Main Results:

• The magnetic wall filter effectively suppressed RF energy transmission between array coils.
• The MW rejection band was tunable, providing high isolation.
• Both first-order and higher-order coupling were successfully mitigated.
• Experimental results confirmed the simulation predictions.

Conclusions:

• The proposed magnetic wall filter is an effective solution for decoupling coils in ultra-high field MRI RF transmit arrays.
• This method significantly reduces mutual coupling, enhancing parallel RF transmission capabilities.
• The MW technique offers a tunable approach to improve RF array performance and imaging quality at 7T.