P37.05: Prenatally diagnosed posterior fossa abnormalities: a fifteen year review

Abstract

Poster abstractsshadowing from the fetal skull, particularly in the third trimester. Extreme inclination of the scan plane through the posterior fossa can result in falsely increased to cisterna magna measurements. Fetal MRI, not suffering from these limitations, is used more in order to determine the underlying CNS abnormalities, and to confirm or provide further evidence of anomalies depicted by sonography. 3D ultrasonography has tried to overcome the limitations of 2D ultrasonography. Oblique view TM of 3D/4D ultrasonography is imaging technology which enables to examine and view threedimensional volume data in various planes without limitations. The acquisition plane can be optimized to show the cerebellar vermis and to allow measurement of the cisterna magna. A 35-year-old, twin pregnant woman was referred for suspicion of Dandy Walker malformation of one twin on routine ultrasonography at 21 weeks of gestation. In 2D ultrasonography, the cisterna magna was enlarged with a diameter of 12.6 mm and the examination of vermis was difficult due to hindering of the skull and the other twin. 3D ultrasonography was performed and the oblique view of volume data showed the presence of vermis. The fetal MRI at 23 weeks of gestation demonstrated the slightly hypoplastic inferior cerebellar vermis but the posterior fossa not enlarged. In conclusion, 3D/4D ultrasonography provides detailed information without limitation and may be an alternative technique in the evaluation of posterior fossa. P37.03Fetal cerebellar volume measurement using conventional multiplanar 3D and VOCAL rotational technique University of Naples Federico II, ItalyObjectives: To compare methods of measuring fetal cerebellar volume and to establish nomograms of fetal cerebellar volume according to gestational age for the accurate diagnosis of cerebellar anomalies. Methods: Two methods of measuring fetal cerebellar volume in 25 normal fetuses, between 19 and 32 weeks of gestation, were compared: the conventional multiplanar three dimensional (3D) mode and the Virtual Organ Computer-aided AnaLysis (VOCAL) method. A 3D ultrasound volume of the fetal cerebellum was acquired transabdominally. Linear regression was used to construct an equation for 3D volume calculation and gestational age. Fetal growth was confirmed by measuring the biparietal diameter (BPD), TCD, head circumference (HC), abdominal circumference and femur length. The presence of any relation between these indices and cerebellar volume was evalutated. Paired t test was used to compare data obtained with two different methods. Results: Cerebellar volume varied from a minimum of 1.24 cm 3 at 19 weeks to the maximum detected value 12.3 cm 3 at 32 weeks. Our results indicated that the volume of fetal cerebellum is highly correlated with gestational age in normal pregnancies and there was substantial agreement between the results of both approaches. Moreover, there was no statistically significant difference between the cerebellar volume values obtained using the 3D multiplanar or 3D VOCAL (P >...