J. B. Fowlkes
J. A. Ivey
E. A. Gardner
J. M. Rubin
P. L. Carson
Dept. of Radiol., Univ. of Michigan Med. Ctr., Kresge III Res. Bldg., Rm. 3315, Ann Arbor, MI 48109-0553
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 the dog using was visible in a distal artery of the leg. Therefore it may be possible to make perfusion and vascular flow measurements without the addition of stabilized contrast agents.