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.