Passive b1 field shimming

A magnetic resonance system, comprising:

• an examination region for receiving a subject to be examined;
• a plurality of radiofrequency (RF) coil elements adjacent to the examination region which generate an excitation field in the examination region according to a generated excitation signal;
• two or more RF transmitters, each which generates an excitation signal for transmission via at least one of the plurality of RF coils to generate a B1 excitation field;
• a passive shimming device including at least one of:
• a rod composed of a solid dielectric material without a proton signal and with a permittivity greater than 100 disposed in the examination region at a prearranged position below the subject to passively shim the generated B1 excitation field;
• a plurality of tubes configured to receive a variable volume of dielectric fluid disposed adjacent to the plurality of RF coil elements to passively shim the generated B1 excitation field;
• and
• a shimming processor which analyzes uniformity of the B1 excitation field in the examination region and therefrom determines at least one of (a) at least one of a position, dimensions, and/or dielectric permittivity of the rod, (b) the volume of dielectric fluid in each tube and/or the dielectric permittivity of the dielectric fluid supplied to each tube, (c) amplitude and/or phase settings for the two or more RF transmitters.