Quantitative diffusion tensor imaging of the brain in young adults shows age-related structural changes in gray and white matter

A comparison of microstructural maturational changes of the corpus callosum in preterm and full-term children: a diffusion tensor imaging study

INTRODUCTION

Preterm children with thinning of the corpus callosum (CC) frequently achieve poor neurodevelopmental outcomes despite the absence of a definite brain lesion. Here, the authors compared the microstructural characteristics of the CC in preterm and full-term children using diffusion tensor imaging (DTI).

METHODS

Twenty-two preterm children with no definite focal lesion but with thinning of the CC by conventional magnetic resonance imaging and 23 age-matched full-term children were investigated by DTI. CCs were subdivided into genu, rostral body, body, isthmus, and splenium, and voxel counts (VC), fractional anisotropies (FA), and apparent diffusion coefficients (ADC) were measured in each subdivision. Eleven preterm and 11 age-matched full-term subjects underwent follow-up scanning and interval changes in these parameters for each subdivision were compared.

RESULTS

VC and FA were significantly lower in the preterm group than in the full-term group, particularly in the isthmus. Furthermore, incremental changes in VC and FA were significantly smaller in the preterm group. Differences in maturation between the two groups were more pronounced with age in all subdivisions except the splenium. At all ages, noticeable FA differences between the two groups were observed in the isthmus. For white matter tracts, the preterm group displayed lower FA and fiber number, higher ADC values than the term group.

CONCLUSIONS

The present study shows that thinning of the CC is correlated with lower FA value and that it is more pronounced in preterm children. In addition, the isthmus was found to be the most vulnerable subdivision in preterm children.

Voxel-based analysis of white matter during adolescence and young adulthood

PURPOSE

To evaluate differences in age-related brain white matter by voxel-based analysis of healthy adolescents and young adults.

MATERIALS AND METHODS

Echo-planar diffusion-tensor magnetic resonance (MR) imaging was performed in healthy subjects of 3 groups (aged 11-13, 16-18 and 23-25, respectively). Linear correlative analyses were applied to determining age-related fractional anisotropy (FA) and mean diffusivity (MD), and t-test was performed to compare FA and mean diffusion maps between different age groups.

RESULTS

Significant positive correlation of FA with age was found in the internal capsule, the external capsule, the frontal white matter, and the body and genu of the corpus callosum. Compared with the 11-13 age group, FA in the 16-18 age group increased in the internal capsule, the frontal white matter, the body and the splenium of the corpus callosum. Compared to the 16-18 age group, FA in the 23-25 age group increased in the frontal white matter, the posterior limb of internal capsule, and the genu of the corpus callosum. Statistically significant negative correlation of the mean diffusion with age was found in the frontal and parietal white matter. Compared with the 11-13 age group, MD in the 16-18 age group decreased in the prefrontal and the temporo-parietal white matter. Compared with the 16-18 age group, MD in the 23-25 age group decreased in the frontal white matter.

CONCLUSION

Diffusion-tensor MR imaging results indicate that white matter maturation assessed at different ages involves increases in FA and decreases in mean diffusion of the white matter during adolescence and young adulthood. FA and mean diffusion may reflect different physiologic processes in healthy adolescents and young adults. Taken together, these data show that maturation of white matter is an important part of brain maturation during adolescence and young adulthood.