Three-dimensional sonographic calculation of the volume of intracranial structures in growth-restricted and appropriate-for-gestational age fetuses.

OBJECTIVES: To evaluate the feasibility and reproducibility of volume segmentation of fetal intracranial structures using three-dimensional (3D) ultrasound imaging, and to estimate differences in the volume of intracranial structures between intrauterine growth-restricted (IUGR) and appropriate-for-gestational age (AGA) fetuses.
METHODS: Total intracranial, frontal, thalamic and cerebellar volumes were measured using 3D ultrasound imaging and Virtual Organ Computer-aided AnaLysis (VOCAL) in 39 IUGR and 39 AGA fetuses matched for gestational age, at 28-34 weeks of gestation. Volumes of, and ratios between, structures were estimated, and differences between IUGR and AGA fetuses were calculated. Volume measurements were performed by two observers, and interobserver and intraobserver intraclass correlation coefficients (ICCs) were calculated for each structure.
RESULTS: Volumes were satisfactorily obtained in all fetuses. All net volumes except those for the thalamus (P = 0.23) were significantly smaller (P = 0.001) in IUGR fetuses. After adjusting volumes for biparietal diameter the frontal volume was significantly smaller (P = 0.02) and the thalamic volume significantly greater (P = 0.03) in IUGR fetuses than in AGA fetuses. Significant intergroup differences in the ratios between structures were found only in those involving the frontal region. Interobserver ICCs were as follows: total intracranial 0.97 (95% CI, 0.92-0.98), cerebellar 0.69 (95% CI, 0.44-0.75), frontal 0.66 (95% CI, 0.42-0.79) and thalamic 0.54 (95% CI, 0.37-0.72).
CONCLUSIONS: IUGR fetuses show differences in the volume of intracranial structures compared with AGA fetuses, with the largest difference found in the frontal region. These differences might be explained by in-utero processes of neural reorganization induced by chronic hypoxia.