Impulse response method for characterization of echogenic liposomes.
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 × 10(6) to 1 × 10(7) 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.
Biomedical Engineering Program, University of Cincinnati, Cardiovascular Center 3940, 231 Albert Sabin Way, Cincinnati, Ohio 45267-0586.
Jason L
JL
Raymond
Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, Netherlands.
Ying
Y
Luan
Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, Netherlands.
Tom
T
van Rooij
Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, Netherlands.
Klazina
K
Kooiman
Department of Internal Medicine, Division of Cardiology, University of Texas Health Science Center, Houston, Texas 77030.
Shao-Ling
SL
Huang
Department of Internal Medicine, Division of Cardiology, University of Texas Health Science Center, Houston, Texas 77030.
David D
DD
McPherson
Physics of Fluids Group, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands.
Michel
M
Versluis
Department of Biomedical Engineering, Thoraxcenter, Erasmus Medical Center, P.O. Box 2040, 3000 CA, Rotterdam, Netherlands.
Nico
N
de Jong
Department of Internal Medicine, Division of Cardiovascular Health and Disease and Biomedical Engineering Program, University of Cincinnati, Cardiovascular Center 3935, 231 Albert Sabin Way, Cincinnati, Ohio 45267-0586.
Christy K
CK
Holland
D000162:Acoustics; D003287:Contrast Media; D008081:Liposomes / Q000737:chemistry*; D045423:Microbubbles; D000069453:Ultrasonic Waves; D014783:Viscosity
D003287:Contrast Media; D008081:Liposomes