Jens Hoffmann1, Gunamony Shajan1, Rolf Pohmann1
1High Field Magnetic Resonance Center,
Max Planck Institute for Biological Cybernetics, Tuebingen,
Microstrip patch antennas, recently used for traveling-wave excitation at high field strengths, provide a fairly homogeneous excitation pattern in the human head but have high power demands especially when the Larmor frequency is near or below the cutoff frequency of the waveguide. In this work, we present a capacitively tunable patch antenna that can be brought in close proximity to the subject in order to improve efficiency. We demonstrate the image homogeneity in the human head at 9.4 Tesla as well as a simulation-based evaluation of the antennas efficiency and SAR depending on the distance to the subject.