Assessment of inflammation with contrast ultrasound

Future clinical applications of contrast-enhanced ultrasound will likely expand beyond the assessment of microvascular perfusion. One promising direction is the development of site-targeted microbubbles that are retained within regions of a specific disease process and thereby allow phenotypic characterization of tissue. Inflammation is an ideal disease state for targeting with microbubbles because the pathophysiologic processes that initiate and support the inflammatory response occur within the microcirculation, where microbubbles reside. This review describes methods that have been used to direct microbubbles to regions of inflammation. These methods rely on either (1) intrinsic properties of albumin or lipid microbubbles that promote their attachment to leukocyte adhesion molecules, or (2) conjugation of monoclonal antibodies or other ligands to the microbubble surface that recognize specific endothelial cell adhesion molecules. This review also considers ultrasound imaging methods that may be used to detect microbubbles retained within inflamed tissue.