Abstract #4499

Modeling the Influence of TR and Excitation Flip Angle on the MTR Obtained from 3D FLASH MRI

Gunther Helms¹, Henning Dathe², Peter Dechent¹

¹MR-Research in Neurology and Psychiatry, University of Gttingen, Gttingen, Germany; ²Biomechanics Group, Dept. of Orthodontics, Universityhospital, Gttingen, Germany

Modeling and optimization of the magnetization transfer ratios (MTR) obtained from FLASH MRI is often based on continuous-wave models that only implicitly account for excitation and relaxation during TR. These effects were explicitely modeled by an approximation of free relaxation between the RF pulses and verified on the human brain in vivo at 3T by variation of flip angle and TR. The influence of inhomogeneous RF fields could be readily incorporated. Choice of short TR and larger flip angles improved the MTR contrast and reduced the influence of RF inhomogeneity.