[Simple extension of an ultrasound B image device to a cw duplex scanner for carotid artery studies].

In contrast to cw-Doppler sonography, ultrasound B-mode imaging is rarely applied in routine examinations for carotid artery stenosis. This may be due to the fact that B-mode imaging without accompanying Doppler sonography lacks reliability, and that Duplex scanners with pulsed Doppler modules are expensive. In this paper a method is described for constructing a cw-Duplex scanner by slight modification and combination of conventional B-mode and cw-Doppler devices. Our experience with this equipment shows that it facilitates clear distinction of the carotid branches on the B-mode image, and that it is capable of visualising carotid occlusions as well as overlapping and atypical vascular courses, all of which frequently limit the diagnostic potential of Doppler sonography. For routine examinations of the carotid bifurcation, ease of application and considerably lower costs make the cw-Duplex scanner preferable to pulsed Duplex devices.