New acoustical approaches to perfusion and other vascular dynamics

Manipulation of bubble‐based ultrasound contrast has been examined for the purpose of perfusion measurement. By exposing a dialysis tube (0.6 cm diam) of flowing blood (20 to 50 ml/min) containing albumin‐stabilized contrast agent to a burst of a 0.75‐MHz field at 0.2 MPa, the additional Doppler and b mode signal produced by the microbubbles was interrupted and then increased beyond the initial level. The experiment was also performed using a constant infusion of contrast agent into the blood flow and a much lower amplitude acoustic field (0.05 MPa) was able to start and stop the flow of bubbles. Similar control over bubble flow was observed in a kidney perfusion phantom where a standard colored microsphere technique indicated that the washin–washout time for the contrast scaled linearly with perfusion. Finally an experimental system has been developed which generates a contrast bolus in vivo without the introduction of stabilized microbubbles. The bolus generated by this system in the descending aorta of...