In vivo analysis of the post-natal development of normal mouse brain by DTI

The water diffusion characteristics of wild-type mouse brains have been studied in vivo by DTI to follow developmental changes. Here, axial (lambda(//)) and radial (lambda(perpendicular)) diffusivities and fractional anisotropy were measured from the fifth day of life (P5) and at three other post-natal ages (P12, P19 and P54). Magnetic resonance images were collected from a single sagittal slice in the middle of the two hemispheres; ROI were chosen in nine different structures of both grey and white matter. Fractional anisotropy (FA) from P5 onwards distinguished structures of both white and grey matter, even though myelination had yet to occur. Between P5 and P54, a significant increase in FA was observed in the genu of the corpus callosum due to a significant decrease in lambda(perpendicular) whereas lambda(//) remained stable. Many other significant variations of lambda(//) and lambda(perpendicular) were measured in different structures. They were substantially correlated with axon and myelin maturation which are responsible for the main evolutions of the brain during its post-natal development. These quantitative data show that in vivo characterization of the anatomy and microstructure of the normal mouse brain during development is possible. The normative data will greatly improve the characterization of abnormal development in the transgenic mouse brain.