Effect of microbubble ligation to cells on ultrasound signal enhancement: implications for targeted imaging.
OBJECTIVE
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.


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. 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.


CONCLUSIONS
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.
Lankford
Miles
M
Cardiovascular Division, University of Virginia, Charlottesville, Virginia, USA.
Behm
Carolyn Z
CZ
Yeh
James
J
Klibanov
Alexander L
AL
Robinson
Peter
P
Lindner
Jonathan R
JR
D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D042783:Endothelial Cells / Q000000981:diagnostic imaging* / Q000502:physiology*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D051379:Mice; D045423:Microbubbles; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*