Continuous-Wave Doppler Ultrasound

Abstract

Early noninvasive vascular diagnostic procedures relied heavily on continuous-wave (CW) Doppler ultrasound techniques. Development of CW Doppler instrumentation began in the mid 1950's in Japan with the work of physicist Shigeo Satomura. Donald Baker, an engineer at the University of Washington, working under the direction of pediatric cardiologist Robert F. Rushmer, lead a team that developed the first CW Doppler instrument in the United States in the early 1960's. CW Doppler instruments use two elements to continuously transmit ultrasound waves and to receive signals from moving reflectors within the ultrasound field. CW instruments are less costly and electronically less complex than pulsed Doppler systems. The major disadvantage of CW Doppler is the absence of depth discrimination. Display options include simple “audio” interpretation, analog recordings produced by a zero crossing detector, and spectral Doppler waveforms using fast Fourier analysis. Despite the limitations of CW Doppler techniques, they remain popular today in the assessment of patients in various clinical settings.