An R2* model of white matter for fiber orientation and myelin concentration

- A new R2* model for fiber orientation and myelin concentration is proposed.
- The model explains the total myelin effects on R2* in white matter.
- The myelin effects on R2* were subtracted to generate a new myelin-removed R2* map.
- The corrected R2* map reveals reduced R2* heterogeneity in white matter.

Myelin, which consists of lipid bilayers, is one of the major constituents of white matter in the brain and has been suggested as a primary source of magnetic susceptibility contrasts. In this study, a new R2* model that simultaneously explains the effects of fiber orientation and myelin concentration is proposed and tested. In addition, a new approach that produces R2* maps without the effects of myelin is suggested. Experimental results demonstrate that the model reveals a high goodness of fit for the R2* distribution of white matter compared to a model that explains either fiber orientation or myelin concentration. The proposed R2* map shows a relatively uniform spatial distribution of R2* compared to the uncorrected R2* map and the fiber orientation or myelin concentration corrected R2* map.

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