Spatial fourier transform processing of cRGD microbubble echoes in mousetumors

Xiaowen Hu, Chris Anderson, Joshua Rychak, Katherine Ferrara

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The development of targeted ultrasound contrast agents has broughtultrasound imaging into the arena of molecular imaging. In particular, targetedmicrobubbles are now utilized to detect angiogenesis in the early phase of tumordevelopment. The detection of bound agents in a low mechanical index imagingscheme is desirable for clinical application. Here, we present a novelquantitative ultrasound contrast imaging method using the 2D Fourier transformfor such targeted contrast agents. In this study, microbubbles coated with RGDpeptides were used to target v3-bearing endothelial cells. The quantitativeimaging method was based on the low mechanical-index contrast pulse sequencing(CPS) technology (Siemens Medical Solutions) and employed time-domain averagingto suppress echoes from freely circulating microbubbles, thus enhancing echoesfrom bound microbubbles. Intensity normalization over the ROI was employed tocompensate for variations encountered during in vivo studies, such asdifferences in injected microbubble dose and vascular morphology. The spatialFourier transform of the time-averaged images was calculated to assess imagesmoothness. Then, we compared the spatial Fourier spectra of the images andcalculated the 6 dB Fourier width with and without high amplitude microbubbledestruction. The proposed imaging method was verified in vitro. Images wereacquired from Met-1 syngeneic tumors in mice after injection, 7 minutes later,and after a destructive sequence. The normalized intensity of bound microbubblesin the tumor region was 0.80.1, compared with a normalized intensity of0.020.02 in the same region for a control (non-targeted) microbubble and 0.10.1for a scrambled peptide. The normalized intensity of bound microbubbles in thesurrounding vessels and tissues was negligible. The 6 dB Fourier width was2.70.2 cycles/mm for targeted and 0.80.1 cycles/mm for freely circulatingcontrol microbubbles. With the application of image averaging, subtraction ofthe microbubble-image intensity after a destructive pulse was not required forbound bubble discrimination. The quantitative strategy using the spatial FourierTransform was successfully implemented and is independent of attenuation.

Original languageEnglish (US)
Title of host publicationProceedings - IEEE Ultrasonics Symposium
Number of pages4
StatePublished - 2010
Event2010 IEEE International Ultrasonics Symposium, IUS 2010 - San Diego, CA, United States
Duration: Oct 11 2010Oct 14 2010


Other2010 IEEE International Ultrasonics Symposium, IUS 2010
Country/TerritoryUnited States
CitySan Diego, CA


  • microbubble
  • spatial Fourier transform
  • targeted imaging
  • tumor

ASJC Scopus subject areas

  • Acoustics and Ultrasonics


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