Demonstration of a carotid body tumour by ultrasound

Abstract

Carotid body tumours are uncommon and are characteristically situated between the internal and external carotid arteries at the carotid bifurcation. Carotid arteriography is used to show both the splaying of these two vessels and the presence of a typical tumour vascular supply. We describe a noninvasive method utilizing Doppler-shift ultrasound for demonstrating the presence of a carotid body tumour and illustrate this with a case report. The ultrasound system has been described in detail elsewhere (Coghlan and Taylor, 1978; Lewis et al., 1978) and principally consists of a transducer and Doppler-shift velocimeter, a spectral analyser and a continuous-wave imaging system. The transducer is placed on the neck and transmits a narrow beam of ultrasound at a frequency of 5 MHz into the carotid arteries. As the erythrocytes are moving, scattered signals are altered in frequency due to the Doppler effect. Erythrocyte velocities vary across the lumen and therefore a spectrum of Doppler-shift frequencies is backscattered at each instant and detected by the transducer. The signals are then spectrally analysed and displayed instantaneously on an oscilloscope screen in the form of a sonogram (Fig. 1), giving information about the distribution and range of erythrocyte velocities in the insonated vessel. Sonograms from the common carotid external and internal carotid arteries each have a characteristic shape and so allow the examiner to identify which vessel is being insonated.