Abstract #0747

Selective degeneration of crossing fibres and its relationship with fractional anisotropy

Jordan A. Chad^1,2, Ofer Pasternak³, David H. Salat⁴, and J. Jean Chen^1,2

¹Rotman Research Institute, Baycrest Health Sciences, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada, ³Departments of Psychiatry and Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States, ⁴MGH/HST Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States

Selective degeneration of crossing fibres has been reported in diffusion MRI studies of Alzheimer’s disease alongside increased fractional anisotropy (FA). Similar albeit more subtle selective degeneration has been suggested in healthy aging, but increased FA with age has not been reported on cross-sectional studies of aging. In this work, we use DTI tractography to measure selective degeneration of crossing fibres in healthy aging among 212 subjects. Increased FA with age is found in this cohort only after applying free water elimination (FWE), suggesting that increasing extracellular water in aging may introduce variability that obscure finer structural phenomena in cross-sectional designs.

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