Original ArticleEffect of Microbubble Ligation to Cells on Ultrasound Signal Enhancement Implications for Targeted ImagingLankford, Miles BS*; Behm, Carolyn Z. MD*; Yeh, James MBChB†; Klibanov, Alexander L. PhD*; Robinson, Peter MD*; Lindner, Jonathan R. MD‡Author Information From the *Cardiovascular Division, University of Virginia, Charlottesville, Virginia; the †National Heart and Lung Institute, Imperial College London, Hammersmith Campus, London, U.K.; and the ‡Cardiovascular Division, Oregon Health and Sciences University, Portland, Oregon. Received April 25, 2006, and accepted for publication, after revision, June 24, 2006. Supported by grants (R01-HL-074443, R01-HL-078610 and R01-DK-063508) to Dr. Lindner from the National Institutes of Health, Bethesda, Maryland; Dr. Behm is supported by a Post-doctoral Fellowship Grant from the American Heart Association Mid-Atlantic Affiliate, Baltimore, Maryland. Reprints: Jonathan R. Lindner, MD, Cardiovascular Division, UHN-62, Oregon Health and Sciences University, Portland, OR 97221. E-mail: [email protected]. Investigative Radiology: October 2006 - Volume 41 - Issue 10 - p 721-728 doi: 10.1097/01.rli.0000236825.72344.a9 Buy Metrics Abstract Objectives: Molecular imaging with contrast-enhanced ultrasound (CEU) relies on the detection of microbubbles retained in regions of disease. The aim of this study was to determine whether microbubble attachment to cells influences their acoustic signal generation and stability. Materials and Methods: Biotinylated microbubbles were attached to streptavidin-coated plates to derive density versus intensity relations during low- and high-power imaging. To assess damping from microbubble attachment to solid or cell surfaces, in vitro imaging was performed for microbubbles charge-coupled to methacrylate spheres and for vascular cell adhesion molecule-1-targeted microbubbles attached to endothelial cells. Results: Signal enhancement on plates increased according to acoustic power and microbubble site density up to 300 mm−2. Microbubble signal was reduced by attachment to solid spheres during high- and low-power imaging but was minimally reduced by attachment to endothelial cells and only at low power. Conclusion: Attachment of targeted microbubbles to rigid surfaces results in damping and a reduction of their acoustic signal, which is not seen when microbubbles are attached to cells. A reliable concentration versus intensity relationship can be expected from microbubble attachment to 2-dimensional surfaces until a very high site density is reached. © 2006 Lippincott Williams & Wilkins, Inc.