To Doppler or Not to Doppler: From Doppler Ultrasound to Color Doppler to Doppler in 3D and Beyond

This review aims to provide the reader with an update on the present and potential clinical applications in Doppler ultrasound in perinatal medicine. Umbilical artery Doppler plays an important role in the management of intrauterine growth restriction (IUGR) and pre-eclampsia and aids in twin-to-twin transfusion syndrome management while notching in the waveform is a predictor of umbilical cord abnormalities. Middle cerebral artery Doppler reliably detects fetal anemia and may be useful in the assessment of IUGR as well. Abnormal uterine artery Doppler may play a role in predicting growth restriction, hypertensive disorders of pregnancy and preterm delivery. Abnormal ductus venosus waveforms can also be used to predict adverse fetal outcome and may allow for better timing of delivery while umbilical venous pulsations may be a sensitive marker for fetal heart failure in hydropic pregnancies. 3D power Doppler allows better small vessel visualization that is not affected by angle of insonation and has been used to diagnose placental and cord abnormalities. Significant improvements have recently occurred, improving the visualization and evaluation of placental vascularity, resulting from enhancements in delineation of tissue detail through electronic compounding and harmonics as well as enhancements in signal processing of frequencyand/or amplitude-based color Doppler ultrasound. Spatial representation of vascularity can be improved by utilizing 3D processing. Greater sensitivity of 3D Doppler ultrasound to macroand microvascular flow has provided improved anatomic and physiologic assessment throughout pregnancy. The rapid development of these new ultrasound techniques will continue to enlarge the scope of clinical applications in placental studies. As clinical experience with these new technologies increases and as the technology improves further, it is reasonable to expect that 3D Doppler and 4D ultrasound will be complementary addition to well-established 2D Doppler ultrasound imaging.