An MRI apparatus includes a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, an RF coil assembly having at least a first port and a second port, an RF transceiver system having a pulse module and configured to transmit RF signals to the first port and the second port, and a computer programmed to drive the RF coil assembly in quadrature through the at least first port and the second port, measure a B1 field using at least one flux probe at two or more angular orientations within the RF coil assembly, and characterize and optimize performance of the MRI system based on the measurements of the B1 field.