Excitation of polymer-shelled contrast agents with high-frequency ultrasound.
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.
Ketterling
Jeffrey A
JA
Mamou
Jonathan
J
Allen
John S
JS
Aristizábal
Orlando
O
Williamson
Rene G
RG
Turnbull
Daniel H
DH
D000162:Acoustics; D000818:Animals; D003287:Contrast Media; D006801:Humans; D017711:Nonlinear Dynamics; D011108:Polymers; D014463:Ultrasonography / Q000379:methods*
D003287:Contrast Media; D011108:Polymers