This chapter provides a basic understanding of the most important physical principles and an introduction into the basics of ultrasound techniques. It is important to consider that the three-dimensional ultrasound beam is not an ideal, linear beam, but has a cylindrical near zone and a cone-shaped far field. Live moving 3D displays are now possible with this technique, which has accordingly been named 4D echocardiography or real-time 3D echocardiography. Lowering the pulse repetition frequency suddenly gives the impression that the cyclic movement is running backwards at a much lower frequency. This is called signal aliasing. In Doppler echocardiography, aliasing occurs if the frequency of the Doppler shift is higher than half of the pulse repetition frequency. Imaging artifacts occur with all imaging modalities. Electronic interference artifacts in the 2D and Doppler modes result from other electric instruments with inadequate shielding, for example electric cauterizing and continuous cardiac output devices.