Future directions in ultrasound contrast agent research

Abstract

Since the introduction of Levovist® in Europe and Albunex® in the United States, interest in ultrasound contrast agents has increased enormously. This change is reflected in the ensuing rapid pace of technical development, and the depth of the discussions during this topical meeting. Before Albunex®, it was essentially impossible to convince an equipment manufacturer to devote time to the development of contrast-specific imaging modalities. After Albunex®, harmonic gray-scale imaging was in the clinic within the year, followed by harmonic color Doppler imaging, power Doppler, pulse inversion gray scale, pulse inversion Doppler, power modulation, coherent contrast imaging, and so on. The trend continues today as old techniques are improved, new techniques (e.g., subharmonic imaging) are tested and new approaches (e.g., phase-shift imaging) are conceived. Similarly, rapid advances have occurred in other areas, with models now including the details of shell viscoelasticity, in vitro studies now imaging single bubble dynamics to microsecond resolution, and specially designed microbubbles being used for targeted imaging, drug delivery, and gene therapy. Even bioeffects research has ‘‘advanced’’ with the discovery of imaging-modality-dependent contrast agent effects such as induction of premature ventricular contractions. Selected aspects of each of these areas will be discussed.