Patent ID: 8198891

Claim:
A magnetic resonance imaging (MRI) apparatus comprising: a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet, and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images; and a computer programmed to: apply a first off-resonant radio frequency (RF) pulse at a first frequency to a plurality of nuclei excited at a resonant frequency, wherein the first frequency is different than the resonant frequency; acquire a first signal from the plurality of nuclei after application of the first off-resonant RF pulse; determine a phase shift from the first signal, wherein the phase shift is based on the first off-resonant RF pulse; determine a B 1 field based on the phase shift relative to a reference scan; and store the B 1 field on a computer readable storage medium.