Spectral Doppler: Basic Principles and Instrumentation

Abstract

Spectral Doppler ultrasound velocimetry involves systematic analysis of the spectrum of frequencies that constitute the Doppler signal. This chapter presents a general perspective on Doppler signal anlyses and describes the spectral Doppler ultrasound devices commercially available for clinical use. They include continuous-wave (CW) Doppler, pulsed-wave (PW) Doppler and duplex Doppler devices. Within the realm of obstetric usage, the application needs are diverse and require various choices of equipment. For example, fetal Doppler echocardiography requires advanced duplex ultrasound instrumentation, which combines the capabilities of high-resolution two-dimensional imaging with the PW Doppler mode and an acoustic power output appropriate for fetal application. For umbilical arterial hemodynamic assessment, simpler, substantially less expensive CW Doppler equipment with a spectral analyzer may be sufficient. It is essential therefore that one develop a basic understanding of the implementation of Doppler ultrasound technology.