MR volumetry of brain and CSF in fetuses referred for ventriculomegaly.

OBJECTIVE. The purpose of this study was to validate the method of performing fetal brain volumetry. In particular, our objectives were to assess which imaging plane is most reproducible for the performance of brain volumetry measurements and to ascertain inter- and intraobserver variability in determining brain volume in fetuses referred for ventriculomegaly (VM). SUBJECTS AND METHODS. In this prospective study, 50 consecutive fetuses at 17 - 37 weeks of gestational age referred for MRI for VM underwent fast spin-echo T2-weighted imaging. Supratentorial brain parenchyma, lateral ventricles, and extraaxial and cerebellar volumetric measurements were manually obtained in three planes by three radiologists. Inter- and intraobserver variability were assessed. The relationship between volumes and gestational age, and lateral ventricular diameter were assessed. RESULTS. Volumes increased with gestational age. The presence of VM correlated with increased lateral ventricle diameter. The effect of imaging plane was negligible. Inter- and intraobserver variability were low. CONCLUSION. Supratentorial parenchyma and lateral ventricular volumes can be reliably measured on fetal MRI, and imaging plane was not an important factor in measurement. Further studies are needed to correlate these indexes with long-term postnatal outcomes.