title: Carotid artery volume flow: in vivo measurement with time-domain-processing US.
abstract: OBJECTIVE
  To evaluate carotid artery volume-flow measurements with time-domain-processing ultrasonography (US).
  
  
  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. Flow through the carotid artery was varied by means of a number of physiologic and pharmacologic interventions. The reference standard for volume flow consisted of measurements with transit-time US flowmetry. At a limited number of measurement points, this reference standard was validated against true volume flow measured with timed collection.
  
  
  RESULTS
  For flow rates less than 500 mL/min, a linear correlation existed between measurements with time-domain processing and the US flow meter (r2 = .96, P < .001, slope = 1.117). Values above 500 mL/min were less well correlated with the reference standard. True flow was underestimated with both methods, less so with time-domain processing than with US flowmetry (underestimation, 10% versus 21%). Measurements were significantly less reproducible with time-domain processing than with US flowmetry (P < .001). Interobserver variability was negligible.
  
  
  CONCLUSIONS
  Because of operator errors, measurements with time-domain processing should be repeated at least three times to ensure accuracy and may be inaccurate in flow rates over 500 mL/min.
authors.affiliation: Department of Radiological Sciences, University of California, School of Medicine, Los Angeles 90095-1721, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Westra
authors.forename: D J
authors.initials: DJ
authors.lastname: Levy
authors.forename: J C
authors.initials: JC
authors.lastname: Chaloupka
authors.forename: J A
authors.initials: JA
authors.lastname: Hill
authors.forename: J M
authors.initials: JM
authors.lastname: Robert
authors.forename: J W
authors.initials: JW
authors.lastname: Sayre
authors.forename: F
authors.initials: F
authors.lastname: Viñuela
mesh_terms: D000818:Animals; D001165:Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000503:physiopathology; D001783:Blood Flow Velocity; D001810:Blood Volume; D002302:Cardiac Output; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging* / Q000502:physiology / Q000503:physiopathology; D002550:Cerebral Veins / Q000002:abnormalities; D004195:Disease Models, Animal; D015588:Observer Variation; D015203:Reproducibility of Results; D012212:Rheology; D013552:Swine; D014463:Ultrasonography / Q000379:methods*; D014655:Vascular Resistance