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.

This chapter discusses the clinical merits and limitations of conventional ultrasound (US) techniques for evaluation of both early and advanced carotid disease. A number of complementary ultrasonographic techniques such as B-mode scanning, duplex sonography, and contrast harmonic imaging are available for imaging of the carotid arteries. The first morphological abnormalities of arterial walls can be imaged by B-mode ultrasonography. This technique is one of the best methods for detection of early stages of atherosclerotic disease, because it is easily applicable, readily available, and demonstrates the wall structure with better resolution than magnetic resonance angiography or conventional angiography. In the initial period of cerebrovascular ultrasonographic insonation, the ophthalmic artery was used as an indirect test for detection of significant carotid artery stenosis. Targeted US techniques combine US imaging technology with specific contrast agents for the assessment of molecular or genetic signatures for disease.