Imaging the carotid bifurcation using continuous-wave Doppler-shift ultrasound and spectral analysis

A non-invasive method is described for visualizing the carotid bifurcation using a continuous-wave Doppler-shift technique simultaneously with spectral analysis of the blood velocities from all parts of the vessel lumen. The system is directional so that arteries can be visualized in the presence of signals from adjacent veins. The technique uses a transducer which is attached to a position-sensing arm so that the position of the ultrasound beam on the neck, when sensing arterial blood flow-velocities, can be translated onto a storage oscilloscope. By repeated passes of the transducer across the vessel lumen a 2 dimensional image of the carotid bifurcation is formed. As each image point is marked, the full spectrum of blood-velocities corresponding to that position is continuously displayed on a second oscilloscope beside the image scope. Ultrasound images are compared with arteriograms and both continuous-wave and pulsed Doppler ultrasound imaging systems are discussed.