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

A novel radiofrequency (rf) power calibration method for the purpose of nuclear magnetic resonance excitations based on monitoring signal phase rather than signal amplitude is described theoretically and is demonstrated experimentally. This unique method enables the determination of rf power required for any desired tip angle in clinical magnetic resonance imaging procedures with an accuracy of 1-5%, essentially independent of motion, flow, slice variations, and/or T1 and T2 variations. The advantages of the new method are discussed and are compared with currently common, amplitude-based calibration techniques.