Proper RF excitation of a human body in prostate and cardiac MRI at the ultra-high field is only possible to achieve by using phased arrays of antennas attached to the body (so-called surface coils). All previously demonstrated approaches were based on resonant structures such as e. g. dipoles, loops TEM-line sections, supporting standing waves that produce current at the surface. Because of the standing wave behavior, excited at the object’s surface current has the same phase at different points of the coil. However, it was shown in work [1], that in-phase current is not optimal for obtaining a maximum signal-to-noise ratio (SNR) in the center region of the object. Also, this is correct for the filed during transmission : equal phase does not maximize the transmission efficiency, i.e. the ratio between a radio-frequency magnetic field in the region of interest to the square root of accepted power.

In this study, one show that we can optimize the RF-magnetic field of single antenna using an line of slots, aligned along the Z-axis by optimizing the amplitude and phase of their excitation.

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