CAROTID-ARTERY VOLUME FLOW - IN-VIVO MEASUREMENT WITH TIME-DOMAIN-PROCESSING US

PURPOSE: To evaluate carotid artery volume-flow measurements with time -domain-processing ultrasonography (US). MATERIALS AND METHODS: Volume -flow measurements were obtained in the carotid arteries of nine swine with time-domain-processing US. Four swine were prepared with a model of an arteriovenous shunt mow through the carotid artery was varied b y means of a number of physiologic and pharmacologic interventions. Th e reference standard for volume flow consisted of measurements with tr ansit-time US flowmetry. At a limited number of measurement points, th is reference standard was validated against true volume flow measured with timed collection. RESULTS: For now rates less than 500 mL/min, a linear correlation existed between measurements with time-domain proce ssing and the US flow meter (r(2) = .96, P < .001, slope = 1.117). Val ues above 500 mL/min were less well correlated with the reference stan dard. True flow was underestimated with both methods, less so with tim e-domain processing than with US flowmetry (underestimation, 10% versu s 21%). Measurements were significantly less reproducible with time-do main processing than with US flowmetry (P < .001). Interobserver varia bility was negligible. CONCLUSION: Because of operator errors, measure ments with time-domain processing should be repeated at least three ti mes to ensure accuracy and may be inaccurate in flow rates over 500 mL /min.