The normal neonatal brain: MR imaging, diffusion tensor imaging, and 3D MR spectroscopy in healthy term neonates

There is a lack of normative diffusion tensor imaging (DTI) and 3D MR spectroscopy (MRS) data in the early neonatal period. We report quantitative values from a cohort of healthy term neonates to serve as baseline data for studies assessing brain development and injury.

Sixteen healthy term neonates (median age, 7 days) were studied with spin-echo T1- and T2-weighted MR imaging, DTI, and 3D point-resolved spectroscopy sequence (PRESS) MRS without sedation on a 1.5 T scanner. Average diffusivity (D(av)), fractional anisotropy (FA), eigenvalues (EV), and metabolite ratios (N-acetylaspartate [NAA]/choline, lactate/choline) were calculated by automated processing in 7 brain regions. Neurodevelopment was assessed by blinded and validated neuromotor examinations and the Bayley II test at 3 and 14 months.

Two neonates were excluded from the cohort: one had brain injury on T2-weighted imaging, and the other, who had normal MR imaging, showed mildly delayed cognition at 14 months. The mean DTI values of the remaining 14 neonates were between these ranges: D(av)=0.98-1.48 10(-3) mm(2)/s, FA=0.14-0.30, EV1=1.21-1.88, EV2=0.95-1.46, and EV3=0.77-1.24 (all x 10(-3) mm(2)/s). The NAA/choline ratio ranged between 0.58 and 0.73, and minimal lactate/choline (<0.15) could be detected in each neonate. All neonates exhibited clinically normal neuromotor status.

Our study demonstrates the feasibility of obtaining high-quality quantifiable MR data in nonsedated healthy term neonates that can be used to study normal early brain development and as control data in studies of perinatal brain injury.