Double Cross Magnetic Wall Decoupling for Quadrature Transceiver RF Array Coils using Common-Mode Differential-mode Resonators

Abstract: In contrast to linearly polarized RF coil arrays, quadrature transceiver coil arrays are capable of improving signal-to-noise ratio (SNR), spatial resolution and parallel imaging performance. Owing to a reduced excitation power, low specific absorption rate can be also obtained using quadrature RF coils. However, due to the complex nature of their structure and their electromagnetic proprieties, it is challenging to achieve sufficient electromagnetic decoupling while designing multichannel quadrature RF coil arrays, particularly at ultrahigh fields. In this work, we proposed a double cross magnetic wall decoupling for quadrature transceiver RF arrays and implemented the decoupling method on common-mode differential mode quadrature (CMDM) quadrature transceiver arrays at ultrahigh field of 7T. The proposed magnetic decoupling wall comprised of two intrinsic decoupled loops is used to reduce the mutual coupling between all the multi-mode current present in the quadrature CMDM array. The decoupling network has no physical connection with the CMDMs' coils giving leverage over size adjustable RF arrays. In order to validate the feasibility of the proposed cross magnetic decoupling wall, systematic studies on the decoupling performance based on the impedance of two intrinsic loops are numerically performed. A pair of quadrature transceiver CMDMs is constructed along with the proposed decoupling network and their scattering matrix is characterized using a network analyzer. The measured results show all the current modes coupling are concurrently suppressed using the proposed cross magnetic wall. Moreover, field distribution, and SNR intensity are numerically obtained for a well-decoupled 8-channel quadrature knee-coil array.