title: A model for ultrasound absorption and dispersion in dilute suspensions of nanometric contrast agents.
abstract: Ultrasound dispersion and absorption are examined in dilute suspensions of contrast agents of nanometric size, with a typical radius around 100 nm. These kinds of contrast agents are designed for targeted delivery of drugs for cancer treatment. Compared to standard contrast agents used for imaging, particles are of smaller size to pass through the endothelial barrier, their shell, made up of biocompatible polymer, is stiffer to undergo a longer lifetime, and they have a liquid core instead of a gaseous one. Ultrasound propagation in dilute suspension is modeled by combining two modes for particle oscillations. The first one is a dilatational mode assuming an incompressible shell with a rheological behavior of Kelvin-Voigt or Maxwell type. The second one is a translational mode induced by visco-inertial interaction with the ambient fluid. The relative importance of these two modes of interaction on both dispersion and absorption is quantified and analyzed for a model system and for two radii (75 and 150 nm) and the two rheological models. The influence of shell parameters (Young modulus, viscosity, and relative thickness) is finally discussed.
authors.affiliation: Université Pierre et Marie Curie-Paris 6, Institut Jean Le Rond d'Alembert, UMR CNRS 7190, 4 place Jussieu, 75252 Paris cedex 05, France. francois.coulouvrat@upmc.fr
authors.forename: François
authors.initials: F
authors.lastname: Coulouvrat
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Thomas
authors.forename: Ksenia
authors.initials: K
authors.lastname: Astafyeva
authors.forename: Nicolas
authors.initials: N
authors.lastname: Taulier
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Conoir
authors.forename: Wladimir
authors.initials: W
authors.lastname: Urbach
mesh_terms: D000042:Absorption; D003287:Contrast Media; D055119:Elastic Modulus; D005583:Fourier Analysis; D016014:Linear Models; D008962:Models, Theoretical; D009038:Motion; D053758:Nanoparticles; D009991:Oscillometry; D010316:Particle Size; D011108:Polymers; D011312:Pressure; D012212:Rheology; D013016:Sound; D013997:Time Factors; D014465:Ultrasonics / Q000379:methods*; D014783:Viscosity
chemical_list: D003287:Contrast Media; D011108:Polymers