Objectives: To evaluate the development of myelination in normal fetuses quantitatively using magnetic resonance (MR) imaging in relation to gestational age (GA).
Methods: Fetal MR images were obtained from 101 fetuses between 26 and 39 weeks of gestation with no neurological problems. Regions of interest were designated in frontal lobe, corona radiata, optic radiation, thalamus, pons, cerebellar vermis, and vitreous body. The signal intensity ratio (SIR) was calculated by the signal intensity of each of these designated areas to that of the vitreous body and analyzed in relation to GA.
Results: The SIR of the frontal lobe did not vary significantly with GA. The SIR of the corona radiata and the optic radiation decreased significantly with GA (P < 0.05); after 34 weeks of gestation, they decreased sharply. The SIR of the thalamus, the pons, and the cerebellar vermis was significantly smaller than that of the cerebral white matter at 26 weeks of gestation (P < 0.05) and decreased significantly with GA (P < 0.05).
Conclusion: Changes in the SIR approximately corresponded to the time-course of progression of myelination in the previous histopathological reports. Semiquantitative evaluation on MR images may allow prenatal diagnosis of a delay or deficit of myelination.
Copyright 2004 John Wiley & Sons, Ltd.