In Vitro Doppler Ultrasound Investigation of Turbulence Intensity in Pulsatile Flow With Simulated Cardiac Variability

Meghan L. Thorne, Tamie L. Poepping, Hristo N. Nikolov, Richard N. Rankin, David A. Steinman, David W. Holdsworth

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

An in vitro investigation of turbulence intensity (TI) associated with a severe carotid stenosis in the presence of physiological cardiac variability is described. The objective of this investigation was to determine if fluctuations due to turbulence could be quantified with conventional Doppler ultrasound (DUS) in the presence of normal physiological cycle-to-cycle cardiac variability. An anthropomorphic model of a 70% stenosed carotid bifurcation was used in combination with a programmable flow pump to generate pulsatile flow with a mean flow rate of 6 mL/s. Utilizing the pump, we studied normal, nonrepetitive cycle-to-cycle cardiac variability (±3.9%) in flow, as well as waveform shapes with standard deviations equal to 0, 2 and 3 times the normal variation. Eighty cardiac cycles of Doppler data were acquired at two regions within the model, representing either laminar or turbulent flow; each measurement was repeated six times. Turbulence intensity values were found to be 11 times higher (p < 0.001), on average, in the turbulent region than in the laminar region, with a mean difference of 24 cm/s. Twenty cardiac cycles were required for confidence in TI values. In conclusion, these results indicate that it is possible to quantify TI in vitro, even in the presence of normal and exaggerated cycle-to-cycle cardiac variability. (E-mail: david.holdsworth@imaging.robarts.ca).

Original languageEnglish (US)
Pages (from-to)120-128
Number of pages9
JournalUltrasound in Medicine and Biology
Volume35
Issue number1
DOIs
StatePublished - Jan 2009

Bibliographical note

Funding Information:
The authors acknowledge ATL (Advanced Technology Laboratories, Philips, Bothell, WA, USA) for the UM8 ultrasound unit. Financial support has been provided by the Heart and Stroke Foundation of Ontario (Grant # T-6427). Vessel models were fabricated with support from the Canadian Institutes for Health Research (group grant #MOP-77964). Drs. Holdsworth and Steinman are Career Investigators supported by the Heart and Stroke Foundation of Ontario.

Keywords

  • Blood flow velocity
  • Cardiac variability
  • Carotid artery bifurcation
  • Coherent fluctuation
  • Doppler ultrasound
  • Ensemble average
  • Flow phantom
  • Incoherent fluctuation
  • Spectral analysis
  • Turbulence intensity

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