The effect of turbulence on the variation of the ultrasonic Doppler amplitude within the cardiac cycle

The effect of turbulence on the variation of the ultrasonic Doppler signal within the cardiac cycle have been evaluated experimentally using a pulsatile flow loop model. Turbulence has been generated in the model by adding a screen mesh in the tube. Porcine red cells suspended in saline solution at 40% hematocrit were used as the scattering fluid. Experiments were performed at a mean flow velocity of 12 cm/s and a maximal flow velocity at peak systole of approximately 60 cm/s. The amplitude of the Doppler signal in presence of turbulence was found to increase during systole with a maximum occurring early after peak systole, and to decrease in diastole during deceleration of flow. It is postulated that the variation of the Doppler amplitude within the flow cycle is associated with a cyclic change in the correlation among red cells.