Imaging in obstretrics and gynecology: current trend and future perspectives

Today ultrasonography is used to investigate the anatomy and function of every fetal structure, from the fingernails to the optic nerve. Ian Donald is credited with being the first to successfully use diagnostic ultrasonography to investigate the gravid uterus. It has facilitated invasive procedures such as chorionic villus sampling, ovum retrieval for in vitro fertilization, follicular and other cyst aspirations, and gamete intrafalloppian transfer. Color Doppler is used to study umbilical artery and vein flow and to locate these vessels for blood sampling. In the eight menstrual week (42 days or 6 weeks after conception), the embryo is clearly recognizable. The head, trunk, arms, and legs can be seen. The digits of the hands and feet are formed but are not yet complete. This is not a penis but it is the tail, which does not completely disappear until the end of the embryonic period in 2 more weeks. By mid-pregnancy, the coronal view of the head reveals that the cranium is nearly a perfect circle, which also confirms that the head is normally proportioned. The only requirement for a valid biparietal diameter (BPD) measurement is that the calipers must be perpendicular to the interhemispheric fissure and pass transversely through the thalamus. The nasal bones and septum can be seen midway between the orbits. The abdominal circumference (AC) should be measured perpendicular to the spine at the level where the umbilical vein joints the left portal vein. Just caudal to the plane for the AC measurement, the insertion of the umbilical cord can be seen. In the late third trimester or at term, sonographic fetal observations become more difficult. A fetus triples its mass in the third trimester; weight gain is from around 1200 g to approximately 3600 g. Fetal observations are more tedious because the arms, legs, face, body, placenta, and uterine wall all are often pressed together by fetal position. Three-dimensional (3D) ultrasonography is a novel advance in the application of ultrasounds in the diagnosis of a sequence of fetal pathologies. It involves a system of probes that register images in multiple layers, then the information is transferred to a computer within the instrument itself, where the threedimensional reconstruction is carried out automatically. One of the most recent novelties in ultrasonography studies has been the application of a fourth dimension. The development of the 4D system adds movement to 3D ecography; in this way, apart from obtaining exclusively anatomic information, structure from a functional perspective is evaluated.