ABSTRACT
The use of ultrasound in medical diagnosis is best associated with its ability to image internal structures of the body. This chapter examines the Doppler effect when the source and receiver transducers are collinear and stationary with respect to the moving reflector. It considers closed-loop ultrasonic ranging systems that operate under constant-phase conditions with a moving reflector. The chapter describes an experimental system that may have application in the noninvasive measurement blood glucose concentration in a tissue such as an earlobe. This system is based on the closed-loop, constant-phase principle used in the no-touch ocular pulse measurement, NOTOPM system, except that the ultrasound is transmitted rather than reflected. The Doppler effect can easily be observed with both electromagnetic and sound waves. The chapter also describes how the Doppler effect used with continuous-wave (CW) and pulsed ultrasound can measure blood velocity, as well as the velocity of moving tissues in the body, such as aneurisms, fetal heartbeat, cardiac diagnosis.
