Four-dimensional ultrasound for detection of fetal abnormalities and comparation with two-dimensional ultrasound

Ultrasonography is a safe and useful method in detecting fetal anomalies in utero, and with the aid of rapidly advancing technologies, is forever developing. Currently the area of prenatal diagnosis has been flooded with articles concerning new tools such as 3D/ 4D ultrasonography. There are various studies comparing the detection rates of fetal anomalies with conventional 2D and 3D modalites. However the sole use of 4D Ultrasonography has yet to be thoroughly explored. The aim of this study is to evaluate and compare the detection rates of 2D versus 4D ultrasonography.This study included a restrospective account of 1379 pregnant woman who applied to Gazi University Hospital, Department of Obstretics and Gynecology at 16-28 gestational weeks. These women underwent routine second level detailed ultrasonographic scanning and all outcomes were noted. In addition to these patients, women at varying gestational ages with fetal anomalies were included. Detected anomalies were then classified into two groups, i.e. superficial and non-superficial malformations. Then the ultrasonographic visualization and detection of anomalies were compared and evaluated as being "imaged better", "worse" or "imaged in a similar way" for both ultrasonographic modalities.Amongst the 1433 fetuses scanned, a total of 194 anomalies were detected in 176 fetuses. Of these, 61 were classed as superficial (31.4%) while 133 were not (68.6%). When all anomalies were taken into account, 139 (71.6%) were considered to be detected better with 2D ultrasound, 30 (15.5%) better with 4D, and the remaining 25 (12.9%) anomalies were evaluated similarly with both methods. When the superficial anomalies were evaluated separately 30 (49.2%) were visualized better with 4D ultrasound, 12 (19.7%) were detected beter with 2D ultrasound, whereas 19 (31.1%) were considered similar with both methods.The comparison between the entire study group and superficial anomalies only supported the idea that 2 D ultrasound was better at detecting anomalies (p<0.001). However, 4D ultrasound proved to be advantageous in that it diagnosed superficial pathologies due to better visual quality, resolution and the distinction between surrounding structures (p<0.005). 2D ultrasound accurately defined all of the 194 malformations, that were either supported by other antenatal tests or later confirmed postnatally or postmortem findings. 4D ultrasound was accurate in 84 cases (43.3%; p<0.01). 54 (88.5%) of these cases were included superficial anomalies. Hence, bearing the total group of anomalies 2D ultrasound was significantly better at detecting fetal anomalies in comparison with 4D ultrasound. When both superficial malformations and non superficial anomalies were compared, the detection rate was greatly increased by using both 2D and 4D ultrasound imaging. The opposite must also be considered: the detection of non-superficial anomalies were increased by solely using 2D imaging (p<0.001).Our results conclude that 4D ultrasound is superior to 2D ultrasonography when the fetal face, extremities and other skeletal structures are in question. However this advantage does not uphold with the evaluation of intrafetal structures. Since the routine use of 2D imaging procedes the application of 4D scanning, it does not seem possible to benefit from 4D on its own.The current role of 4D ultrasonography is to compliment and support 2D findings. Due to the inclusion of superficial anomalies, the generalisation of the entire group would not be just. Extensive prospective studies concerning the role of 4D ultrasonography in midtrimester second level ultrasound scanning using different imaging techniques, advanced equipment capable of supplying various desired cross-sections must be performed.