Normal reference values of ratios of blood flow velocities in internal carotid artery to those in common carotid artery using Doppler sonography

Abstract Purpose. The ratios of of blood flow velocities in the internal carotid artery (ICA) to those in the common carotid artery (CCA) (V ICA /V CCA ) are used to identify patients with critical ICA narrowing, but their normal reference values have not been established. We provide reference data for the V ICA /V CCA ratios for the peak systolic velocity (PSV), mean velocity (MV), and end‐diastolic velocity (EDV) measured in a large group of healthy subjects. Methods. We examined 343 healthy subjects with color duplex sonography. They were divided into 3 age groups: group I, <40 years; group II, 40–60 years; group III, >60 years. Results. The values of V ICA /V CCA ratio for the PSV were as follows [mean (upper and lower reference values)]. In women, group I: 0.81 (0.48–1.14), group II: 0.88 (0.36–1.40), group III: 0.9 (0.36–1.40). In men, group I: 0.65 (0.32–0.98), group II: 0.72 (0.39–1.05), group III: 0.91 (0.27–1.56). The V ICA /V CCA ratio for PSV increased with age only in men and its values were significantly higher in women than in men in the group I and group II age groups. Conclusion. This study provides normal reference values for the V ICA /V CCA ratios for PSV and shows that the ratio varies with age and sex. The upper reference limit for the ratio can serve as an aid in the more specific identification of patients with minor or mild ICA narrowing. © 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2009