Abstract 2148: Combined Use of avb3-Targeted Nanoparticles and Entropy-Based Signal Detectors for Ultrasound Molecular Imaging of Angiogenesis in the Papilloma Virus Transgenic Mouse
Background: To detect binding of molecularly targeted nanoparticles to sparse avb3 epitopes in primordial angiogenesis, we developed novel, entropy-based signal receiver (Hc), sensitive to subtle changes in the shape of a radio frequency (RF) signal as contrasted with conventional signal processing. We compared the sensitivity of both approaches for delineation of early neovascularization in the ears of an angiogenic mouse.
Methods: Eight K14-HPV16 transgenic mice were treated with either normal saline (n=3) or 0.3 mg/kg i.v. of αvβ3 -targeted nanoparticles (n=5) and imaged for two hours using a research ultrasound imager (Vevo 660 w/30MHz probe). All RF data were processed off-line to reconstruct conventional and Hc images. Image segmentation was performed by thresholding measurements at the 97% level for both data sets. The mean value of pixels segmented was computed at each time post-injection.
Results: With conventional image processing techniques, no targeted contrast signal could be detected in angiogenic vessels in the ears. However, the subtle changes in signal features induced by binding of αvβ3-targeted nanoparticles to neovasculature were clearly distinguished by Hc from surrounding echoes (P<0.005). Control mice demonstrated no contrast enhancement, regardless of the image processing method applied.
Conclusion: These data demonstrate the ability and complementarity of entropy-based receivers in conjunction with targeted nanoparticles to elucidate the presence of αvβ3-integrins in primordial neovasculature, particularly in acoustically unfavorable environments.