Doppler ultrasound derived measurement of turbulence intensity.

摘要

Doppler ultrasound measurements of turbulence may provide important hemodynamic information that is complementary to current clinical measurements of peak systolic velocity in diseased blood vessels. The overall hypothesis of this thesis is that accurate and precise measurements of turbulence intensity (TI) can be obtained in human carotid arteries using conventional Doppler ultrasound (DUS) equipment with the addition of data acquisition hardware and analysis software. In this thesis, we develop and validate the principles of DUS TI measurements through three experimental objectives. In the first objective we demonstrate that TI can be quantified in an in vitro flow system under conditions of steady flow using a well-established blood-mimicking fluid. In the second objective we extend the in vitro flow tests to include pulsatile flow in an anthropomorphic stenosed carotid bifurcation model with added physiologically realistic cycle-to-cycle cardiac variability. In the third objective we implement a novel approach to enable DUS based turbulence characterization in human subjects, where concurrent ECG data may not be available. This new approach, which uses a frequency domain Fourier filter technique, demonstrates the feasibility for accurate characterization of TI in human subjects in future clinical research applications.;Keywords: Doppler ultrasound, carotid artery atherosclerosis, blood flow velocity, advanced spectral analysis, turbulence intensity, coherent fluctuation, incoherent fluctuation, ensemble average, high-pass frequency filter, in vitro modeling, blood-mimicking fluid, in vivo.