Deriving and characterizing fiber tract specific anisotropic R2 from DTI

Motivation: The orientation dependence of transverse relaxation R2 in the human brain white matter could be exploited as a potential myelin specific biomarker for assessing demyelinating pathologies. Goal(s): To investigate the feasibility of characterizing fiber tract specific anisotropic R2 solely based on DTI. Approach: A high-resolution public domain Connectome DTI dataset was used for the demonstration. Two major fiber tracts, corpus callosum and corticospinal tract, were segmented, and corresponding orientation dependent R2 profiles were quantified based on a recently developed model. Results: Results suggested that anisotropic R2 could be extracted effectively from DTI, facilitating easy access to a potential myelin specific biomarker. Impact: In this work, we demonstrated that a single T2-weighted image (i.e., b=0) effectively separates anisotropic R2 from its isotropic counterpart offering an efficient alternative to conventional lengthy R2 mapping method of incorporating in-vivo axon fiber orientation information from DTI.