ANNALS OF IBADAN POSTGRADUATE MEDICINE
J.A. Akinmoladun1,2, V.O. Oboro1 , and T.I. Adelakun1
Introduction: Two-Dimensional ultrasound (2DUS) has been the preferred screening method for fetal abnormalities for several decades. Three-dimensional ultrasound (3DUS) is a technique that converts standard 2D grayscale ultrasound images into a volumetric dataset which allows visualization of the fetus in all three dimensions at the same time. It provides an improved overview and a more clearly defined demonstration of adjusted anatomical planes. The use of 3D imaging is however limited to being an adjunct to 2DUS in the visualization of fetal anomalies. The objective of this study is to highlight the importance of adding three-dimensional ultrasound (3DUS) to two-dimensional ultrasound (2DUS) during fetal anomaly screening.
Methodology: This is a descriptive study conducted at a private fetal diagnostic center, in Nigeria between January 2014 and December 2016. The diagnosis of fetal anomalies was first made with 2DUS after which they were evaluated with 3D ultrasound images displayed on the monitor.
Results: Nine fetuses with various fetal anomalies diagnosed on 2DUS were selected for further evaluation with 3DUS. These anomalies include a neck mass, lumbar spinal abnormality, bilateral cleft lip, thanatophoric dysplasia, anencephaly, omphalocele, posterior urethral valve with anhydramnios and ambiguous genitalia diagnosed. These anomalies were better demonstrated on 3DUS.
Conclusion: 2DUS remains the mainstay imaging modality in screening for fetal anomalies. However, 3DUS may complement 2DUS by allowing better delineation of anomalies and gives the parents a better visualization and understanding of identified anomalies, thereby assisting in informed decision making.
Keywords: Two-dimensional; Three-dimensional; Ultrasound; Fetal; Anomalies.
Dr. J.A. Akinmoladun
Department of Radiology,
Faculty of Clinical Sciences,
College of Medicine,
University of Ibadan,
Two-Dimensional ultrasound (2DUS) has been the preferred screening method for fetal abnormalities for several decades1,2. This is because of its advantages which include safety for the mother and fetus, cost-effectiveness, easy accessibility and real time imaging. Also, the images on 2DUS are obtained more easily, rapidly, efficiently and accurately with most fetal abnormalities being detected2,3. Screening for fetal abnormalities otherwise known as fetal anomaly scans was initially done in the second trimester between 18- 22 weeks. However, in the last decade, this screening has moved from the second into the ûrst trimester because of the advent of high resolution ultrasound machines which image the fetus in greater detail at all gestational ages4,5. In the hands of experienced sonologists/sonographers, anatomic surveys between 11 and 14 weeks can now be carried out with good visualization rates of many structures. Some structural anomalies will nearly always be detectable in the first trimester e.g. anencephaly, holoprosencephaly, facial cleft and conjoined twins5-8 .
Three-dimensional ultrasound (3DUS) is a technique that converts standard 2D grayscale ultrasound images into a volumetric dataset. The technique was developed for problem-solving (particularly in obstetric/gynecologic examinations) and to potentially reduce the operator dependence of ultrasound imaging9,10. 3DUS allows visualization of the fetus in all three dimensions at the same time, providing an improved overview and a more clearly defined demonstration of adjusted anatomical planes10 . It allows visualization of the fetal surface as well as more accurate volume and weight measurements thus improving the detection rate of structural fetal abnormalities in early gestation11,12. The use of 3D imaging as a primary screening tool is however limited, therefore it can only be best utilized as a second-stage test11. Many studies have been done to determine the advantages of 3DUS over 2DUS10-13. Some of these studies showed that 3DUS only act as an adjunct to 2DUS in the visualization of fetal anomalies 10-12 . However, some studies were able to discover some more complicated fetal malformations on 3DUS that were missed by 2DUS13 .
3DUS has only been recently introduced to this part of our country and it has been shown to clearly demonstrate the abnormalities seen on 2DUS and also helps the parents in understanding the anomalies better11. We hereby present some of the anomalies detected by 2DUS that were confirmed with 3DUS with a review of literature. Future studies will be aimed at determining if 3DUS is able to detect more anomalies than 2DUS.