Doppler sonography

Doppler sonography of the extracranial carotid and vertebral arteries was introduced as a routine clinical method in the mid-1970s, some years later, ultrasound imaging techniques became available. Early studies using continuouswave (CW) Doppler sonography established criteria for normal and abnormal hemodynamic conditions in the carotid and vertebral artery systems which were later validated in numerous other investigations (Arbeille et al., 1984; Hennerici et al., 1981a; Pourcelot, 1974; von Reutern et al., 1976; Trockel et al., 1984). Due to the reliability of these criteria and the inexpensive technology, CW-Doppler sonography (‘pencil Doppler’) is still used in many neurovascular laboratories regardless of the immediate availability of modern sonographic imaging devices with integrated pulsed wave (PW) Doppler systems. However, since recording of the Doppler flow signals as an analogue envelope curve had significant disadvantages, display of the Doppler frequency spectrum became the preferred method of documentation providing several parameters for hemodynamic analysis (Jacobs et al., 1985; Johnston et al., 1986; Rittgers et al., 1983; Robinson et al., 1988; Taylor & Strandness, 1987; Zwiebel & Knighton, 1990).

Carotid artery

The different extracranial arteries are characterized by distinct acoustic Doppler signals and Doppler spectra, respectively, depending on whether they supply brain tissue with low vascular resistance (internal carotid artery, vertebral artery), muscles and skin with high peripheral resistance (external carotid artery, subclavian artery), or both (common carotid artery) (Fig. 14.1).