DIFFERENT 3D TECHNIQUES IN THE STUDY OF FETAL CORPUS CALLOSUM AND ROLE OF 5D CNS PLUS

INTRODUCTION In daily practice it is difficult to visualize all the normal fetal cerebral midline structures using the axial planes. These planes do not allow direct evaluation of the corpus callosum (CC) and other midline brain structures, thus limiting detection of these midline anomalies on screening scans. The present paper aims to evaluate the role of 3D techniques in the identification of Central Nervous System (CNS) structures. METHODS Fetal cerebral midline structures from 300 low-risk pregnant women were studied prospectively by 2D and 3D ultrasound between 19-23 weeks of gestation during last 5 years. Fetal brain was evaluated by various 3D mode functions such as Oblique technique (OT), OVIX (Oblique View eXtended Imaging), VOCAL and Multi-Slice view. The 3D Multiplanar Imaging allows a simultaneous analysis of the acquired volume in three planes and is used as the first step in the process of volume acquisition, as it is the pre-requisite for later analysis. This allows the section plans to be oriented. If this alignment is properly obtained on C plan, the sagittal and the midsagittal plane containing the CC can be easily visualized. Each volume was processed using the OT and OVIX in order to improve the image resolution in the reconstructed planes. More specifically, a midsagittal view of the midline was obtained, and the OVIX box was adjusted on its central core using a slice thickness of 3mm in order to achieve a coronal view of the CC. Multi-Slice View transforms 3D volume data obtained from a regular ultrasound scan into a series of sequential images captured at intervals of 0.5mm to 5mm segments. Users can instantly view, analyze and understand the more in-depth data, and thereby gain greater diagnostic confidence and accuracy. VOCAL displays sequential parallel slices of 3D anatomy to facilitate more precise volume analysis of the structures. 48 out of 300 patients were also evaluated by 5D CNS plus technique. This technique allows to obtain all the recommended views of the fetal brain for neurosonography, starting from a single axial scan of the fetal head. RESULTS The CC anatomy was accurately reconstructed from axial to sagittal plane in all 48 cases. The CC was visualized as a hypoechoic structure and was divided in four parts: rostrum, genu, body and splenium. This approach allows easily the visualization of the CC, to evaluate its shape, to distinguish normal from abnormal CNS volumes and provide possible diagnoses for abnormal volumes. A complete reconstruction of fetal cerebral views was obtained in 45 of 48 patients, submitted to 5D CNS plus technique. CONCLUSIONS 3D ultrasound enables a precise visualization of the normal and abnormal CC in the median plane. 5D CNS plus was shown to be a reliable technique to obtain in a very short time all the required fetal brain views. No difference was found in terms of time elapsing between the various 3D technique. The OVIX technique may be the most appropriate for the study of CC.