1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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.