The Doppler efect is widely used in almost all fields of medicine, starting from radiology, through gynecology and orthopedics, to internal medicine. Generally speaking, the Doppler effect is a change in the frequency of sound, light or other waves, caused by the relative movement of the source of the waves, i.e. emitters and receivers. The use of the Doppler effect in medicine is based on the difference between the frequencies of emitted and detected sound waves obtained by the reflection of ultrasound on erythrocytes. It is used in a way that the ultrasound beam is directed towards a blood vessel and thereby analyze the Doppler shifts of ultrasound waves scattered across the erythrocytes are being analyzed. In this way, there occurs a picture of blood flow presented using audio display, spectral frequency analysis and Doppler indices. During Doppler use various artifacts may appear but are removed by optimizing the Doppler display. Several Doppler techniques are in use today, most important of which are continuous and pulsed Doppler as well as colored and power Doppler. The ultrasound intensities are obtained by using Doppler far exceed those of a conventional B-mode ultrasound. According to the recommendations of the US FDA, one should strive to decrease the intensity and exposure time of the ultrasound beam, while the National Council for Radiation Protection of the United States officially considered that the benefits of ultrasound use surpass assumed risks.