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Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond

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Abstract

Objective

This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B +1 ) and RF power deposition of dipole antenna arrays for 1H magnetic resonance of the human brain at 1 GHz (23.5 T).

Materials and methods

Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300 MHz (7.0 T) to 3 GHz (70.0 T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1 GHz.

Results

Our results demonstrate that transmission fields suitable for 1H MR of the human brain can be achieved at 1 GHz. An increase in transmit channel density around the human head helps to enhance B +1 in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0 T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array.

Conclusion

The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5 T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system.

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Acknowledgments

This work was funded (in part, T.N.) by the Helmholtz Alliance ICEMED—Imaging and Curing Environmental Metabolic Diseases, through the Initiative and Network Fund of the Helmholtz Association (ICEMED-Project 1210251). The authors wish to thank Russell Hodge (Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany) for brainstorming as well as for editing and proofreading the manuscript.

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  1. Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Strasse 10, 13125, Berlin, Germany

    Lukas Winter & Thoralf Niendorf

  2. Experimental and Clinical Research Center (ECRC), A Joint Cooperation Between the Charité and the Max Delbrück Center for Molecular Medicine, Berlin, Germany

    Thoralf Niendorf

  3. MRI.TOOLS GmbH, Berlin, Germany

    Thoralf Niendorf

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Thoralf Niendorf is founder and CEO of MRI.TOOLS GmbH, Berlin, Germany.

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Winter, L., Niendorf, T. Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond. Magn Reson Mater Phy 29, 641–656 (2016). https://doi.org/10.1007/s10334-016-0559-y

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