Xiang He1, Jie Luo2, Dmitriy A. Yablonskiy1
1Mallinckrodt Institute of Radiology, Washington University in St Louis, School of Medicine, St. Louis, MO, United States; 2Department of Chemistry, Washington University in St Louis, St Louis, MO, United States
Previously proposed generalized Lorentzian approach that allows evaluation of magnetic susceptibility induced MR signal frequency shift in brain tissue is validated here using ex vivo fresh rat optic nerve positioned in the buffer solution. The frequency shift within and around the optic nerve is measured using double-echo gradient echo MRI at two orientations of optic nerve parallel and perpendicular to the external magnetic field. Our results demonstrate that generalized Lorentzian approach, which takes into account cellular anisotropic microstructure of axons, provides satisfactory explanation of experimental data while Lorentzian sphere approximation fails to describe experimental measurements.