title: Excitation of polymer-shelled contrast agents with high-frequency ultrasound.
abstract: Few experimental and complementary theoretical studies have investigated high-frequency (>20 MHz) nonlinear responses from polymer-shelled ultrasound contrast agents. Three polymer agents with different shell properties were examined for their single-bubble backscatter when excited with a 40 MHz tone burst. Higher-order harmonic responses were observed for the three agents; however, their occurrence was at least partly due to nonlinear propagation. Only one of the agents (1.1 microm mean diameter) showed a subharmonic response for longer excitations (approximately 10-15 cycles) and midlevel pressure excitations ( 2.5 MPa). Theoretical calculations of the backscattered spectrum revealed behavior similar to the experimental results in specific parameter regimes.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Ketterling
authors.forename: Jonathan
authors.initials: J
authors.lastname: Mamou
authors.forename: John S
authors.initials: JS
authors.lastname: Allen
authors.forename: Orlando
authors.initials: O
authors.lastname: Aristizábal
authors.forename: Rene G
authors.initials: RG
authors.lastname: Williamson
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Turnbull
mesh_terms: D000162:Acoustics; D000818:Animals; D003287:Contrast Media; D006801:Humans; D017711:Nonlinear Dynamics; D011108:Polymers; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D011108:Polymers