David A. Rudko1, L. M. Klassen1,
Sonali N. de Chickera2, Greg A. Dekaban2, Ravi S. Menon1
1Centre for Functional
& Metabolic Mapping, Robarts Research Institute, London, Ontario, Canada;
2Biotherapeutics Research Group, Robarts Research Institute,
London, Ontario, Canada
In this study, microscopic field (B0) maps were used to asses the Generalized Lorentzian model (GLmodel) of field shifts in healthy rat brain at 9.4 T. Experimentally measured B0 at multiple sampling orientations was within measured error tolerance compared to the GLmodel shifts in subcortical GM and cerebral veins. The enhanced complexity of white matter field shifts was addressed by examining: (i) the elliptical cylinder and (ii) the circular cylinder approximations for axonal bundle fields. The circular cylinder approximation produced negative field shifts comparable to B[0 estimates and the fields around phospholipid-like susceptibility inclusions. χ and R2* maps were reconstructed independently to estimate iron concentration around susceptibility inclusions.