TY - CHAP M1 - Book, Section TI - Application of Pulsed Wave and Continuous-Wave Doppler in the Assessment and Measurement of Cardiac and Systemic Blood Flow* A1 - Noori, Shahab A2 - Siassi, Bijan A2 - Noori, Shahab A2 - Acherman, Ruben J. A2 - Wong, Pierre C. PY - 2018 T2 - Practical Neonatal Echocardiography AB - The measurement of blood flow through any vascular structure using ultrasound requires two basic pieces of information: the velocity of blood flow and the cross-sectional area of the vessel. The velocity of blood flow can be measured using spectral Doppler. As pulsed wave (PW) Doppler allows for measurement of velocity at a specific point in the vessel (ie, range resolution), it is the preferred mode of spectral Doppler. When measuring the velocity, the echocardiographer must take care to use an angle of insonation as parallel as possible to the direction of flow. If the ultrasound beam is intercepting the blood flow at an angle, the velocity will be underestimated (see Chapter 6). In clinical practice, an angle of less than 20° is generally considered acceptable, as the effect on velocity is negligible. An angle greater than 20° will require angle correction, which often produces inconsistent results. Another important point in measuring the velocity is that, in the presence of a turbulent flow, the measured velocity by PW Doppler cannot be used to estimate the flow because of aliasing that occurs with higher velocities (see Chapters 1 and 4). Therefore, the operator should assess the flow by color Doppler first to ensure that the flow is laminar before attempting to obtain the velocity by PW Doppler. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1161424003 ER -