Probing Cytoarchitectural Heterogeneity in the Human Hippocampus with Oscillating Gradient Diffusion Tensor Imaging

Manisha Aggarwal¹, Jiangyang Zhang¹, Susumu Mori¹

We investigate the effect of gradient frequency on diffusion tensor contrasts derived using oscillating-gradient diffusion MRI in the postmortem fixed human hippocampus. Using DTI data acquired at 11.7T with pulsed-gradient and oscillating-gradient diffusion sensitizing gradient waveforms (with modulation frequencies of 50, 100, and 150 Hz), distinct frequency-dependent contrasts were observed in specific layers of the human hippocampus. ADC, parallel and perpendicular diffusivity measurements showed progressive region-specific increases with increasing gradient frequency. The results demonstrate that selective sampling of the diffusion spectrum with oscillating-gradient diffusion MRI can generate contrasts that are uniquely sensitive to the cytoarchitectural heterogeneity of different layers in the hippocampus.