Impulse response method for characterization of echogenic liposomes

Jason L. Raymond (Corresponding Author), Ying Luan, Tom van Rooij, Klazina Kooiman, Shao-Ling Huang, David D. McPherson, Michel Versluis, Nico de Jong, Christy K. Holland

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)


An optical characterization method is presented based on the use of the impulse response to characterize the damping imparted by the shell of an air-filled ultrasound contrast agent (UCA). The interfacial shell viscosity was estimated based on the unforced decaying response of individual echogenic liposomes (ELIP) exposed to a broadband acoustic impulse excitation. Radius versus time response was measured optically based on recordings acquired using an ultra-high-speed camera. The method provided an efficient approach that enabled statistical measurements on 106 individual ELIP. A decrease in shell viscosity, from 2.1 × 10−8 to 2.5 × 10−9 kg/s, was observed with increasing dilatation rate, from 0.5 × 106 to 1 × 107 s−1. This nonlinear behavior has been reported in other studies of lipid-shelled UCAs and is consistent with rheological shear-thinning. The measured shell viscosity for the ELIP formulation used in this study [κs = (2.1 ± 1.0) × 10−8 kg/s] was in quantitative agreement with previously reported values on a population of ELIP and is consistent with other lipid-shelled UCAs. The acoustic response of ELIP therefore is similar to other lipid-shelled UCAs despite loading with air instead of perfluorocarbon gas. The methods described here can provide an accurate estimate of the shell viscosity and damping for individual UCA microbubbles
Original languageEnglish
Pages (from-to)1693-1703
Number of pages11
JournalJournal of the Acoustical Society of America
Issue number4
Publication statusPublished - 2015


  • Acoustical properties
  • Liposomes
  • Bubble dynamics
  • Lipids
  • Contrast agents
  • Phospholipid
  • Oscillators
  • Signal processing
  • Ultrasound
  • Shear thinning


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