Abstract #5495

The role of ferritin and myelin in orientation dependent R2* measured from susceptibility-weighted MR signal in white matter

Daniel Kor^1,2, Jonathan Doucette^1,3, Tianyou Xu⁴, and Alexander Rauscher^1,3,5

¹UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada, ²Engineering Physics, University of British Columbia, Vancouver, BC, Canada, ³Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ⁴Oxford Centre for Functional MRI of the Brain, University of Oxford, Headington, Oxford, United Kingdom, ⁵Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada

The R₂^* relaxation in brain's white matter(WM) exhibits a dependency on WM fibre orientation relative to the external magnetic field, B₀. Here, we introduce a computational model based on first principles derived from magnetic field inhomogeneities generated by ferritin and myelin. We investigate their effects on the multi gradient-echo signal by fitting simulated R₂^*, over angles 0–90^o, to experimental R₂^*(R²=0.94). By comparing different myelin concentrations, we present how ferritin is required to complement myelin in describing the orientation dependency in R₂^*. Additionally, we propose a model for mapping R₂^* as a function of fibre orientation, myelin and iron concentration.

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