Anna Hurshkainen, Masoud Sharifian Mazraeh Mollaei, Marc Dubois, Sergei Kurdjumov, Redha Abdeddaim,Stefan Enoch, Stanislav Glybovski and Constantin Simovski, Decoupling of Closely-Spaced Dipole Antennasfor Ultra-High Field MRI with Metasurfaces, in IEEE Transactions on Antennas and Propagation
Phased antenna arrays of dipoles are widely used in ultra-high field magnetic resonance imaging for creating the controllable radio-frequency magnetic field distributions in a human body. Due to safety and imaging quality reasons each individual channel of the array should be decoupled – electromagnetically isolated from the others. The required number of channels is large and in some techniques the dipole antennas should be located in the close proximity of the human body. Their ultimately dense arrangement leads to a strong mutual coupling and makes the conventional decoupling structures inefficient. This coupling needs to be suppressed without a significant distortion of radio-frequency fields in the imaged area. In this work, we propose and study a novel decoupling technique for two ultra-high field transceiver on-body dipole antennas. The decoupling is performed by a periodic structure of five parallel resonant wires referred to as a metasurface. In contrast to conventional decoupling with a single resonant wire, the metasurface decoupled by means of excitation of a higher-order coupled mode of the wires, which field is highly confined. The main advantage is a low distortion of the RF-field in the central region of the body.
Keywords : Dipole antennas, decoupling, metasurfaces, ultra-high field magnetic resonance imaging