R2 as a Marker for Corticospinal Tract Integrity in Aging

Motivation: Improving evaluations of corticospinal tract (CST) microstructure has implication for normal aging, motor diseases (ALS), and treatment outcomes. Goal(s): The goal of this study is to evaluate R2 as a marker for CST microstructure in aging. Approach: Multi-echo spin echo and multi-shell diffusion acquisitions were used to derive R2 values and diffusion metrics in 35 older subjects and 20 young subjects. Results: Reductions in CST R2 were found in older adults relative to younger adults (P<10-3). Within older adults, CST R2 was negatively associated with age (P=0.008) and with CST diffusivity (Ps<10-3). Impact: The relationship between R2 and diffusivity in CST suggests that R2 is sensitive to subtle differences in tissue microstructure seen in normal aging. Better measurements of CST could improve early detection of ALS or predict post-stroke rehabilitation outcomes.