Open AccessImaging of angiogenesis using Cadence™ contrast pulse sequencing and targeted contrast agents
Author(s) -
Stieger Susanne M.,
Dayton Paul A.,
Borden Mark A.,
Caskey Charles F.,
Griffey Stephen M.,
Wisner Erik R.,
Ferrara Katherine W.
Publication year - 2008
Publication title -
contrast media & molecular imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.714
H-Index - 50
eISSN - 1555-4317
pISSN - 1555-4309
DOI - 10.1002/cmmi.224
Subject(s) - microbubbles , angiogenesis , ultrasound , in vivo , biomedical engineering , medicine , materials science , cancer research , radiology , biology , microbiology and biotechnology
Objectives Low‐power multipulse contrast ultrasound imaging provides a promising tool to quantify angiogenesis noninvasively when used with contrast agents targeted to vascular markers expressed by the angiogenic endothelium. Targeted ultrasound contrast agents, with a diameter on the order of micrometers, cannot extravasate and therefore are targeted solely to receptors expressed by the vascular endothelium. The aim of this study was to evaluate the potential of a low‐power multipulse imaging sequence, Cadence TM contrast pulse sequencing (CPS), combined with targeted contrast agents to quantify angiogenesis. Material and Methods Targeted microbubbles were prepared by conjugating echistatin via biotin–avidin linkage to the surface of a phospholipid microbubble shell. The density of echistatin present on the shell was confirmed with flow‐cytometry and quantified by total fluorescence. The binding of targeted microbubbles was evaluated in vitro by quantifying the adherence of targeted microbubbles to rat aortic endothelial cells, compared with control (nontargeted) microbubbles. The circulation time and adherence of targeted microbubbles was evaluated in vivo in a Matrigel model in rats and compared with control microbubbles using CPS in addition to a destructive ultrasound pulse. Results Using only the low‐power CPS pulse, the echo intensity produced in the neovasculature of the Matrigel pellet was significantly greater with targeted microbubbles than with the control contrast agent ( p < 0.001). Combining CPS with the destructive pulse, the processed image was significantly different in intensity ( p < 0.001) and spatial extent between targeted and control agents ( p < 0.001). When the morphology of the histological sample and ultrasound image correlated, the microvessel density count and the percentage of the circular area enhanced by ultrasound were correlated ( p < 0.05). Conclusion Low‐power multipulse imaging in combination with targeted echistatin‐bearing microbubbles facilitated a noninvasive, quantitative evaluation of early angiogenesis during real‐time imaging. The addition of high‐intensity destructive pulses facilitated estimation of the spatial extent of angiogenesis. Copyright © 2008 John Wiley & Sons, Ltd.