Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond.
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 (1)H magnetic resonance of the human brain at 1 GHz (23.5 T).


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 (1)H 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.


CONCLUSIONS
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.
Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Strasse 10, 13125, Berlin, Germany.
Lukas
L
Winter
Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine, Robert-Roessle-Strasse 10, 13125, Berlin, Germany. thoralf.niendorf@mdc-berlin.de.|Experimental and Clinical Research Center (ECRC), A Joint Cooperation Between the Charité and the Max Delbrück Center for Molecular Medicine, Berlin, Germany. thoralf.niendorf@mdc-berlin.de.|MRI.TOOLS GmbH, Berlin, Germany. thoralf.niendorf@mdc-berlin.de.
Thoralf
T
Niendorf
D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology; D001931:Brain Mapping / Q000379:methods; D003198:Computer Simulation; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D005240:Feasibility Studies; D006257:Head / Q000033:anatomy & histology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D019047:Phantoms, Imaging; D011846:Radio Waves
Electrodynamics; Electron paramagnetic resonance ultrahigh field MR; Magnetic resonance; Radiofrequency antenna