Timo Liimatainen1, Dennis Sorce1, Michael Garwood1, Shalom Michaeli1
1Center for Magnetic Resonance Research, Dept. of Radiology, University of Minnesota, Minneapolis, MN, USA
A method is described to create MRI contrast using rapid amplitude and frequency modulated RF irradiation in a sub-adiabatic condition, referred to relaxation along a fictitious field (RAFF). Bloch simulation of RAFF shows that magnetization follows a fictitious field when magnetization is oriented initially along the fictitious field. Theoretical calculations show sensitivity of RAFF to slow molecular motions with similar sensitivity as the continuous wave spin-locking experiment. The data obtained from human brain shows images with significant contribution of steady state which can be accounted for in the analysis.