Double cross magnetic wall decoupling for quadrature transceiver RF array coils using common-mode differential-mode...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Engineering
• Biomedical Engineering

Background:

• Quadrature transceiver RF coil arrays offer improved signal-to-noise ratio (SNR), spatial resolution, and parallel imaging performance compared to linearly polarized arrays.
• Reduced excitation power in quadrature RF coils leads to a lower specific absorption rate (SAR), enhancing patient safety.
• Achieving electromagnetic decoupling in multichannel quadrature RF coil arrays is challenging, especially at ultra-high fields (UHF), due to complex structures and electromagnetic properties.

Purpose of the Study:

• To propose and implement a novel electromagnetic decoupling method for multichannel quadrature transceiver RF coil arrays at 7 Tesla (7T).
• To reduce mutual coupling between multi-mode currents in common-mode differential mode quadrature (CMDM) arrays using a double-cross magnetic wall.
• To validate the decoupling performance and assess its impact on field distribution and SAR for an 8-channel knee coil array.

Main Methods:

• A double-cross magnetic wall decoupling strategy was designed, comprising two intrinsically decoupled loops, to minimize mutual coupling in quadrature transceiver RF arrays.
• The decoupling method was implemented on common-mode differential mode quadrature (CMDM) quadrature transceiver arrays for UHF MRI at 7T.
• Numerical simulations were performed to study decoupling performance based on impedance, and experimental characterization using a network analyzer was conducted on a constructed CMDM array with the decoupling network.

Main Results:

• The proposed magnetic decoupling wall effectively reduced mutual coupling between all multi-mode currents in the quadrature CMDM array.
• The decoupling network demonstrated no physical connection with the CMDM resonators, offering flexibility for size-adjustable RF arrays.
• Numerical simulations of an 8-channel quadrature knee-coil array showed suppressed current coupling and provided data on field distribution and local SAR.

Conclusions:

• The double-cross magnetic wall is a feasible and effective method for achieving electromagnetic decoupling in multichannel quadrature transceiver RF arrays at ultra-high fields.
• This decoupling technique enhances the performance of UHF MRI systems by improving SNR and potentially reducing SAR.
• The proposed method offers design flexibility and contributes to the development of advanced RF coil arrays for high-performance MRI applications.