A diffusion‐weighted template for gestational age‐related apparent diffusion coefficient values in the developing fetal brain

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Abstract
Objective To determine the pattern of apparent diffusion coefficient (ADC) values in the normal fetal brain obtained with diffusion‐weighted images (DWI) on magnetic resonance imaging (MRI) as a template for normal brain development throughout gestation. Methods This was a prospective study of 46 fetuses without suspicion of brain pathology undergoing a total of 66 ultrasound examinations between 17 and 37 weeks of gestation. At T2‐weighted MRI, four left and four right brain regions were delineated on transverse slices of the native DWI using a b‐value of 0 s/mm2 (b0 images). We examined native b‐value images and calculated ADCavg, ADClow and ADChigh in the basal ganglia, cerebellar hemisphere, frontal parenchyma and occipital parenchyma. Linear regression analysis was used to assess the relationship between gestational age and b0 values as well as the calculated ADC values. Results Delineations were successful in all fetuses for all regions except for the cerebellar hemispheres in four fetuses. There was a negative correlation between gestational age and b0 values in all examined anatomical regions (Pavg, there were no significant changes in the basal ganglia with increasing gestational age, a positive correlation in the frontal (PP=0.03) parenchyma and a negative correlation in the cerebellar hemispheres (P=0.01). For ADClow, there was a negative correlation between gestational age and the cerebellum (P=0.0002) and basal ganglia (P=0.047), but no correlation for the frontal or occipital parenchyma. For ADChigh, there was a positive correlation with gestational age for the frontal parenchyma (P=0.004), occipital parenchyma (P=0.02) and basal ganglia (P=0.03) but there was no correlation for the cerebellum. Conclusions DWI b0 values decreased in the left and right basal ganglia, cerebellar hemisphere, frontal parenchyma and occipital parenchyma between 17 and 37 weeks of gestation and ADCavg values increased in two out of four cerebral regions. It remains to be determined to what extent these observations differ in fetuses with suspicion of brain anomalies and whether such measurements will be useful and more predictive of outcome compared with standard MRI sequences. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.

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