Nucleation threshold of carbon black ultrasound contrast agent

Abstract

Most ultrasound contrast agents used in ultrasonic imaging comprise shell-encapsulated microbubbles, whose ingredients have been associated with adverse bioeffects. In this study, we investigated the nucleation behaviour of carbon black dispersion, whose hydrophobic nanoparticles are used intradermally. For a hypothetical, perfectly spherical carbon black particle surrounded by a perfectly spherical gaseous void, we derived a theoretical nucleation threshold of only 1.3× the resting radius. Carbon black particles and aggregates thereof were investigated using high-speed photography during 1.0 MHz sonication. The nucleation threshold found experimentally is lower than the Blake cavitation threshold of 2.0× the resting radius of free, unencapsulated microbubbles. Therefore, carbon black dispersion may be a promising ultrasound contrast agent.

On the rigidity of four hundred Pickering-stabilised microbubbles

“…The video sequences were stored on a personal computer and processed offline using a method previously published. 28) The first oscillation cycle was taken into account to determine R max . The outcome of the processing were R(t) curves for all 400 microbubbles, and their respective R max values.…”

“…[24][25][26][27] As we concentrate on disruption in the paper, we are less interested in the accuracy of the model beyond the first two cycles. Therefore, we may use a rather simple model, whose derivation we presented earlier, 28) whilst ignoring any solid potentially present inside the microbubble and by adding damping terms and a shell stiffness parameter. 25,29) For an encapsulated microbubble driven by an acoustic wave, the fundamental equation is then given by…”

The ultrasound-triggered explosion of an endoskeletal antibubble yields a predictable fragment size distribution

“…Although endoskeletal microbubbles without cores have not been produced, we may assume that their Laplace pressure is even lower than droplet-containing endoskeletal antibubbles. 10) Assuming no other tensile stress components of relevance and assuming identical acoustic conditions, the resulting fragment distribution should be exponential then, too. As the characteristic length follows from the solid material characteristics and the tensile stress applied, the characteristic diameter of an endoskeletal microbubbles should be on the same order as an endoskeletal antibubble.…”

High-speed photography of gas release from bioactive glass

“…[5][6][7] For the purposes of this study, we may ignore nonspherical terms and multiple scattering, [8][9][10] as we concentrate on the first pulsation cycles. A simplified equation for ultrasound-driven microbubble pulsation has been derived in a prior publication, 11) and modified to incorporate viscous, reradiation, and thermal damping terms. 12) If the kinetic energy of the gas-liquid bubble interface surpasses its surface energy, 13) bubble fragmentation may occur during the contraction phase.…”