Experimental investigations of nonlinearities and destruction mechanisms of an experimental phospholipid-based ultrasound contrast agent.
OBJECTIVE
We sought to characterize the acoustical behavior of the experimental ultrasound contrast agent BR14 by determining the acoustic pressure threshold above which nonlinear oscillation becomes significant and investigating microbubble destruction mechanisms.


METHODS
We used a custom-designed in vitro setup to conduct broadband attenuation measurements at 3.5 MHz varying acoustic pressure (range, 50-190 kPa). We also performed granulometric analyses on contrast agent solutions to accurately measure microbubble size distribution and to evaluate insonification effects.


RESULTS
Attenuation did not depend on acoustic pressure less than 100 kPa, indicating this pressure as the threshold for the appearance of microbubble nonlinear behavior. At the lowest excitation amplitude, attenuation increased during insonification, while, at higher excitation levels, the attenuation decreased over time, indicating microbubble destruction. The destruction rate changed with pressure amplitude suggesting different destruction mechanisms, as it was confirmed by granulometric analysis.


CONCLUSIONS
Microbubbles showed a linear behavior until 100 kPa, whereas beyond this value significant nonlinearities occurred. Observed destruction phenomena seem to be mainly due to gas diffusion and bubble fragmentation mechanisms.
Casciaro
Sergio
S
Institute of Clinical Physiology, National Council of Research, Lecce, Italy. casciaro@ifc.cnr.it
Palmizio Errico
Rosa
R
Errico
Rosa Palmizio
RP
Conversano
Francesco
F
Demitri
Christian
C
Distante
Alessandro
A
D003287:Contrast Media / Q000737:chemistry* / Q000528:radiation effects*; D045423:Microbubbles; D017711:Nonlinear Dynamics; D010316:Particle Size; D010743:Phospholipids / Q000737:chemistry* / Q000528:radiation effects*; D013010:Sonication; D014463:Ultrasonography
D003287:Contrast Media; D010743:Phospholipids