Diffusion tensor imaging (DTI) using variable diffusion times (
tdiff) was performed to investigate wild-type (wt) mice, myelin-deficient
shiverer (
shi) mutant mice
and shi mice transplanted with wt neural precursor cells that differentiate
and function as oligodendrocytes. At
tdiff = 30 ms, the diffusion anisotropy “volume ratio” (VR), diffusion perpendicular to the fibers (
λ![perpendicular](http://www.sciencedirect.com/scidirimg/entities/22a5.gif)
),
and mean apparent diffusion coefficient (<
D>) of the corpus callosum of
shi mice were significantly higher than those of wt mice by 12 ± 2%, 13 ± 2%,
and 10 ± 1%, respectively; fractional anisotropy (FA)
and relative anisotropy (RA) were lower by 10 ± 1%
and 11 ± 3%, respectively. Diffusion parallel to the fibers (
λ//) was not statistically different between
shi and wt mice. Normalized T
2-weighted signal intensities showed obvious differences (27 ± 4%) between wt
and shi mice in the corpus callosum but surprisingly did not detect transplant-derived myelination. In contrast, diffusion anisotropy maps detected transplant-derived myelination in the corpus callosum
and its spatial distribution was consistent with the donor-derived myelination determined by immunohistochemical staining. Anisotropy indices (except
λ//) in the corpus callosum showed strong
tdiff dependence (30–280 ms),
and the differences in
λ
and VR between wt
and shi mice became significantly larger at longer
tdiff, indicative of improved DTI sensitivity at long
tdiff. In contrast, anisotropy indices in the hippocampus showed very weak
tdiff dependence
and were not significantly different between wt
and shi mice across different
tdiff. This study provides insights into the biological signal sources
and measurement parameters influencing DTI contrast, which could lead to developing more sensitive techni
ques for detection of demyelinating diseases.