Radiofrequency power calibration for magnetic resonance imaging using signal phase as indicator

A novel radiofrequency (rf) power calibration method for the purpose of nuc lear magnetic resonance excitations based on monitoring signal phase rather than signal amplitude is described theoretically and is demonstrated exper imentally. This unique method enables the determination of rf power require d for any desired tip angle in clinical magnetic resonance imaging procedur es with an accuracy of 1-5%, essentially independent of motion, flow, slice variations, and/or T-1 and T-2 variations. The advantages of the new metho d are discussed and are compared with currently common, amplitude-based cal ibration techniques. Magn Reson Med 1999;41:474-478, 1999. (C) 1999 Wiley-L iss, Inc.