Dependence of Fractional Anisotropy on Diffusion Time: A Frequency-Domain Analysis Using Temporal Diffusion Spectroscopy

Junzhong Xu¹, Ha-Kyu Jeong¹, Mark D. Does¹, Adam W. Anderson¹, Li Min Chen¹, John C. Gore¹

The FA dependence on diffusion time was studied using temporal diffusion spectroscopy, which employs an oscillating gradient spin echo sequence and has the ability to probe much shorter diffusion times. A clear dependence of white matter factional anisotropy on effective diffusion time has been observed in a fixed monkey brain. The results were also predicted by computer simulations. The dependence observed in this study provides a means to probe diffusion restriction and hindrance at sub-cellular length scales, e.g. intracellular structures, and may provide insights into the microstructure of biological tissues and clarify the origins of anisotropy diffusion in white matter.