Fractional anisotropy in white matter tracts of very-low-birth-weight infants.

Background: Advances in neonatal intensive care have not yet reduced the high incidence of neurodevelopmental disability among very-low-birth-weight (VLBW) infants. As neurological deficits are related to white-matter injury, early detection is important. Diffusion tensor imaging (DTI) could be an excellent tool for assessment of white-matter injury.

Objective: To provide DTI fractional anisotropy (FA) reference values for white-matter tracts of VLBW infants for clinical use.

Methods: We retrospectively analysed DTI images of 28 VLBW infants (26-32 weeks gestational age) without evidence of white-matter abnormalities on conventional MRI sequences, and normal developmental outcome (assessed at age 1-3 years). For DTI an echoplanar sequence with diffusion gradient (b = 1,000 s/mm(2)) applied in 25 non-collinear directions was used. We measured FA and apparent diffusion coefficient (ADC) of different white-matter tracts in the first 4 days of life.

Results: A statistically significant correlation was found between gestational age and FA of the posterior limb of the internal capsule in VLBW infants (r = 0.495, P<0.01).

Conclusions: Values of FA and ADC were measured in white-matter tracts of VLBW infants. FA of the pyramidal tracts measured in the first few days after birth is related to gestational age.