Volumetric analysis of the germinal matrix and lateral ventricles performed using MR images of postmortem fetuses

BACKGROUND AND PURPOSE: The volumetric changes of the ventricular system an d germinal matrix are important to understand brain maturation and the mech anism of subependymal hemorrhage, Our purpose was to show the 3D configurat ion of the brain, germinal matrix, and lateral ventricles and to discuss th e volumetric changes of each structure with maturation by using high-resolu tion MR imaging. METHODS: Three-dimensional MR images of 13 formalin-fixed fetal brains rang ing from 7 to 28 weeks' gestational age (GA) were obtained on a 4.7-T unit. Each 3D configuration of the brain surface, germinal matrix, and ventricle s was rendered from the cross-sectional imaging data sets and its volume me asured. RESULTS: The germinal matrix was detected on MR images at 9 weeks' GA. Its volume exponentially increased by 23 weeks' GA (maximum, 2346 mm(3)) and th en sharply decreased at 28 weeks' CA. The volume of the lateral ventricles increased gradually and reached 2646 mm(3) peak volume at 23 weeks' GA. Bet ween 11 and 23 weeks' GA, total brain and germinal matrix volumes were expo nentially increasing, but the volume ratio of germinal matrix to brain was stable at about 5%. On the other hand, the volume ratio of lateral ventricl es to brain was large between 10 and 13 weeks' GA. This period corresponded to the lateral ventricle showing a "vesicular" aspect with a thin mantle, and the developing mantle thickness of the hemisphere resulted in the decre asing ratio. CONCLUSION: Volumetric information concerning the germinal matrix and later al ventricles may be useful in the accurate interpretation of clinical echo grams and MR images of the fetal brain in utero.