Apparent diffusion coefficient determination in normal fetal brain: a prenatal MR imaging study

Abstract

Background and purpose: Diffusion-weighted MR imaging studies of normal brain development have focused on premature babies who were free of focal lesions on conventional MR images. The condition of prematurity, however, is dissimilar to intrauterine life. We sought to establish normal values of fetal brain apparent diffusion coefficient (ADC) to highlight its abnormal changes in pathologic conditions and to obtain information about normal brain development.

Methods: We measured the ADC, in utero, by using an echo-planar three-axes diffusion-sensitized sequence (b factor, 0 and 600 s/mm(2)), in frontal and occipital white matter and basal ganglia gray matter of 15 fetuses. Their gestational ages ranged from 22 to 35 weeks, and the postnatal MR images or sonograms revealed normal brain.

Results: Mean ADC value was 1.96 +/- 0.1 micro m(2)/ms (SD) in frontal white matter, 1.95 +/- 0.1 micro m(2)/ms in occipital white matter, and 1.56 +/- 0.1 micro m(2)/ms in basal ganglia. A significant negative correlation between ADC and gestational age was found for basal ganglia, whereas only a trend was present for frontal white matter.

Conclusion: Although moderately higher, the ADC determinations we obtained are consistent with those reported in the literature in postnatal studies performed in premature babies.

Fig 1.

Representative case (fetus 10 in Table). A, T2-weighted echo-planar image (b = 0 s/mm²), B, corresponding DW image, and C, resultant trace ADC map illustrate typical ROIs (circles in A and C) traced on an axial section at the basal ganglia level.

Fig 2.

Graph shows the mean ADC values (bars indicate 2 SDs) for frontal and occipital white matter, basal ganglia, and CSF ROIs. The mean ADC of basal ganglia is significantly lower than that of white matter ROIs. * indicates P < .0001 (paired t test).

Fig 3.

Graphs show the correlation between ADC values for the ROIs traced and gestational age. A significant negative correlation was present only for the basal ganglia ROI. A, Basal ganglia: Y = 2.222 − 0.024X; R² = 0.471; P = .0096. B, Frontal white matter: Y = 2.394 − 0.015X; R² = 0.182; P = .1457. C, Occipital white matter: Y = 2.14 − 0.007X; R² = 0.028; P = .5654.