TY - CHAP M1 - Book, Section TI - Color Doppler Sonography in Obstetrics A1 - Paladini, Dario A1 - Donarini, Gloria A1 - Volpe, Paolo A2 - Fleischer, Arthur C. A2 - Abramowicz, Jacques S. A2 - Gonçalves, Luis F. A2 - Manning, Frank A. A2 - Monteagudo, Ana A2 - Timor, Ilan E. A2 - Toy, Eugene C. Y1 - 2017 N1 - T2 - Fleischer's Sonography in Obstetrics and Gynecology: Textbook and Teaching Cases, 8e AB - Key TermsAliasing: aliasing of a Doppler signal occurs when the Nyquist limit has been exceeded. This resulting “wrapped around” appearance of either the pulsed Doppler or color Doppler signal leads to ambiguity in the direction and velocity information being displayed.Angle of insonation: the angle between the long axis of a vessel and direction of the ultrasound beam. This value is dependent upon fetal position in relation to transducer placement.B-flow: an angle-independent technique by which blood flow is detected by analyzing the signal amplitudes of moving red blood cells within vessels. This technique uses a subtraction algorithm that displays only moving blood flow but does not display stationary structures such as the vessel wall.CDUS/PDUS: color Doppler ultrasonography/power Doppler ultrasonography.Glassbody rendering: a three-dimensional volume rendering technique that displays vessels using color or power Doppler ultrasonography. These vascular structures are simultaneously displayed with surrounding anatomic structures that are reconstructed from variably transparent grayscale voxels.Nyquist limit: the theoretical limit to the rate that is required to sample an ultrasound signal that contains data with a specified maximum frequency. It represents the highest frequency that can be coded for a given sampling rate (PRF) to fully reconstruct the ultrasound signal. If the frequency is greater than half the sampling frequency, the Nyquist limit is exceeded.Pulse repetition frequency (PRF): the number of transmitted pulsed Doppler pulses per second. The greatest velocity that can be measured by a specific transducer depends on the distance between the probe and vessel, as well as the PRF.Umbilical coiling index (UCI): the UCI is obtained by dividing the total number of complete vascular coils by the umbilical cord length. Hypercoiling has been defined as a UCI >0.3 coils/cm, whereas hypocoiling as a UCI <0.1 coils/cm. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/12/11 UR - obgyn.mhmedical.com/content.aspx?aid=1151032500 ER -