title: In vitro study of the effects of volume changes on parameters of the radiofrequency amplitude versus time curve with sonicated albumin.
abstract: The ultrasound time intensity curve parameters obtained from an intracoronary injection of either sonicated albumin or Albunex are used to quantify coronary flow changes. How much the volume changes that accompany the flow changes affect various time intensity curve parameters is unknown. Accordingly, we designed a variable-volume in vitro chamber connected to a flow pump operating at four predetermined flow settings (44 to 184 ml/minute). Injections of either sonicated albumin or Albunex were given proximal to a mixing chamber, which then passed through the scanning chamber at three different volume settings. The parameters studied were area under the curve, corrected peak contrast intensity, ascending and descending slopes of the curve, time to peak radiofrequency signal, the time required to reach half peak intensity (half time up), the time required to decay to half peak intensity (half time down), and total transit time (the time from appearance to disappearance of 10% of peak intensity). Although area, half time up, half time down, and transit time all correlated with flow when volume was held constant, only transit time (and the natural logarithm of the transit time) correlated strongly with flow changes when simultaneous changes in volume occurred. Transit time also correlated with volume changes when flow was held constant, but was more sensitive to flow changes. These data may explain why transit time variables may still be able to detect flow changes in the coronary circulation despite a simultaneous change in myocardial blood volume.
authors.affiliation: McGuire Veterans Administration Medical Center, Medical College of Virginia, Richmond.
authors.forename: T R
authors.initials: TR
authors.lastname: Porter
authors.forename: R
authors.initials: R
authors.lastname: Pretlow
authors.forename: A
authors.initials: A
authors.lastname: D'Sa
authors.forename: J V
authors.initials: JV
authors.lastname: Nixon
mesh_terms: D000418:Albumins; D002309:Cardiology / Q000295:instrumentation*; D003287:Contrast Media; D003326:Coronary Circulation / Q000502:physiology*; D004452:Echocardiography; D006801:Humans; D066298:In Vitro Techniques; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D012039:Regional Blood Flow
chemical_list: D000418:Albumins; C060687:Albunex; D003287:Contrast Media