Abstract
In conventional neonatal MRI, the T2 hyperintensity (T2h) in cerebral white matter (WM) at term-equivalent age due to immaturity or impairment is still difficult to identify. To clarify such issue, this study used the metrics derived from a two-compartment WM model of diffusional kurtosis imaging (WM-DKI), including intra-axonal, extra-axonal axial and radial diffusivities (Da, De,// and De,⊥), to compare WM differences between the simple T2h and normal control for both preterm and full-term neonates, and between simple T2h and complex T2h with hypoxic-ischemic encephalopathy (HIE). Results indicated that compared with control, the simple T2h showed significantly increased De,// and De,⊥, but no significant change in Da in multiple premyelination regions, indicative of expanding extra-axonal diffusion microenvironment; while myelinated regions showed no changes. However, compared with simple T2h, the complex T2h with HIE had decreased Da, increased De,⊥ in both premyelination and myelinated regions, indicative of both intra- and extra-axonal diffusion alterations. While diffusion tensor imaging (DTI) failed to distinguish simple T2h from complex T2h with HIE. In conclusion, superior to DTI-metrics, WM-DKI metrics showed more specificity for WM microstructural changes to distinguish simple T2h from complex T2h with HIE.
Highlights
Including the mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD), but without significant change in FA due to the oligodendrocytes and membranes proliferation; Third, “true” myelination stage by showing a shortening signal intensity on T2 weighted image (T2WI), decreased RD and increased FA due to the oligodendrocytes spiral ensheathment around the axon and compact packaged fibers
The results provide the novel insights into the possible abnormal changes underlying simple T2 hyperintensity (T2h), which were similar between preterm and full-term neonates
Above findings of white matter (WM)-diffusional kurtosis imaging (DKI) metrics suggest that simple T2h and complex T2h with HIE may originate from differing WM microstructural changes
Summary
Including the mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD), but without significant change in FA due to the oligodendrocytes and membranes proliferation; Third, “true” myelination stage by showing a shortening signal intensity on T2WI, decreased RD and increased FA due to the oligodendrocytes spiral ensheathment around the axon and compact packaged fibers. With respect to the T2h, diffusion weighted imaging (DWI) and DTI have revealed that such WM abnormality is associated with significant region-specific changes, such as decreased FA, and increased apparent diffusion coefficient (ADC), AD and RD7,23–25. It remains the difficulty for DTI in identifying whether these abnormal diffusivities are due to intra- or extra-axonal microstructural changes. Aiming at verifying such hypothesis by using the DKI-WM metrics, the case-control neonate study was conducted to clarify the intra- and extra-axonal microstructure changes between normal control and simple T2h; between simple T2h and complex T2h
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