Acoustic behaviour of current ultrasound contrast agents.

A general law gives the approximate change in signal level obtained in a particular imaging mode when a suitable contrast agent is added. It also shows that reduction of background signals is essential to overcome limitations found mainly in conventional (linear) ultrasound contrast imaging. Contrast agents contain stabilized microbubbles with very helpful non-linear properties. Acoustic methods for non-destructive and destructive testing of microbubbles are briefly discussed. In the main part, the linear and non-linear acoustic behaviour of various types of contrast agent are described. The latter is useful for new applications in diagnostic ultrasound.