Difference between contrast agents containing gas bubbles and bubble free preparations

For the evaluation and characterization of ultrasonic contrast agents it is important to decide whether the received contrast is due to backscatter signals produced by microbubbles or other means without microbubbles. An experimental setup consisting of a combination of a bubble detection apparatus and a medical ultrasound scanner has been used to answer this question. The bubble detector monitors bubbles in the range from 0.75- mu m to 8- mu m radius, and the ultrasound scanner monitors the received backscatter signal during the experiment. Examples of both an experiment with backscatter from microbubbles and one without microbubbles are given.<>