Oscillating gradient spin-echo (OGSE) diffusion tensor imaging of the human brain

Purpose: The dependence of diffusion tensor imaging (DTI) eigenvalues and fractional anisotropy (FA) on short diffusion times was investigated using oscillating gradient spin echo (OGSE) and pulsed gradient spin echo (PGSE) DTI in the human brain in vivo.

Theory and methods: DTI was performed in seven healthy volunteers at 4.7 Tesla (T) with b = 300 s/mm(2) and diffusion times of 4.1 ms (OGSE 50 Hz), 7.4 ms (OGSE 25 Hz), 20 ms (PGSE), and 40 ms (PGSE). Eigenvalues and FA were compared in the corpus callosum body, splenium and genu, and the corticospinal, cingulum, inferior fronto-occipital, superior and inferior longitudinal fasciculi using tractography, and the thalamus and putamen using region-of-interest.

Results: Relative to 40 ms, the 4.1 ms diffusion time led to significant increases in DTI eigenvalues in seven white matter tracts (6% to 20% parallel, 13% to 40% perpendicular) and both deep gray matter regions (16% parallel, 18% to 26% perpendicular), and reductions of FA (-9% to -12%) in four tracts.

Conclusion: DTI eigenvalues and FA depend on diffusion time in both white and gray matter in the human brain. The ability to target different length scales by means of the diffusion time may improve sensitivity to changes in tissue microstructure associated with pathology.