Origin of B0 orientation dependent R2* (=1/T2*) in white matter

Se-Hong Oh, Young-Bo Kim, Zang-Hee Cho, Jongho Lee
2013 NeuroImage  
Recent MRI studies have demonstrated that the relative orientation of white matter fibers to the B 0 field significantly affects measurement. In this work, the origin of this effect was investigated by measuring R 2 and in multiple orientations and fitting the results to magnetic susceptibilitybased models and magic angle-based models. To further explore the source of magnetic susceptibility effect, the contribution of tissue iron to the orientation dependent contrast was investigated.
more » ... lly, the effects of temperature on and orientation dependent contrasts were studied to understand the differences reported between a fixed specimen at room temperature and in vivo at body temperature. The results suggest that the B 0 dependent variation is better explained by the magnetic susceptibility-based model with susceptibility anisotropy. However, extracting tissue iron did not reduce the orientation dependent contrast, suggesting iron is not the origin of the contrast. This leaves susceptibility effects from myelin as the most probable origin of the contrast. Temperature showed large contribution on both and orientation dependent contrasts, explaining a portion of the contrast difference between the in-vivo and invitro conditions. Keywords Magnetic susceptibility anisotropy; Magic angle effects; B 0 orientation dependent transverse magnetization (T 2 and ); MRI relaxometry
doi:10.1016/j.neuroimage.2013.01.051 pmid:23376494 pmcid:PMC3638902 fatcat:ns74ughxzrej3jpzjy4nrexyd4