ABSTRACT
This chapter provides a basic introduction to the physical principles, instrumentation and bioeffects of ultrasonic imaging, as well as Doppler ultrasound. The frequencies used for ultrasound range from 2 to 10 MHz. A transducer is a device that changes one form of energy to another: in ultrasound, voltage is changed to sound and vice versa. An ultrasound machine is basically a computer with a set of probes. For diagnostic ultrasound imaging short sound pulses are used rather than continuous signals. Note that the tip of the ultrasound probe does not follow the crystal shape but has a protective surface. The ultrasound probes with mechanical systems steer the sound beam by physically pointing the piezoelectric crystal. During the design process of an ultrasound system certain assumptions have to be made in order to maintain a good level of accuracy of the results. There is no evidence that points to negative effects caused by the diagnostic ultrasound.
