A study of the effect of PEG-40 surfactant concentration on thestability of microbubbles post-injection through various needle sizes and its ultrasound imaging performance

摘要

Microbubbles stabilized by surfactant shells have been established as ultrasound contrast agents for the past severaldecades. The microbubbles often get destroyed as these are delivered to the region of interest using catheters withdifferent needle sizes. Optimizing the concentration of the surfactants on its shell is crucial for minimizing microbubbledestruction. In terms of shell material for this work; polyoxyethylene glycol 40 (PEG-40) stearate which is a non-ionicsurfactant, polypropylene glycol and glycerol were used to stabilize the microbubbles with a nitrogen gas core. Presenceof surfactants greatly influence the size and stability of the microbubbles and thus four different surfactant concentrations(2, 5, 10 and 15%) of PEG-40 and two different polypropylene glycol + glycerol (GPW) mixtures (10% and 15%) wereexamined. Nitrogen microbubbles were synthesized through high-shear rotor homogenizer and pushed through threedifferent needle sizes (23, 27 and 30 gauge) using a syringe pump to examine their sensitivity to needle injection. Asample volume of 100 μl containing microbubbles were collected at a constant flow rate of 43.63 ul/min which is themaximum flow rate of the syringe pump used in our experiments. The microbubbles collected at the outlet of the needleswere sandwiched between two glass slides for their stability characterization using optical microscopy. The resultsdemonstrated that solution containing 10% PEG-40, 10% polypropylene glycol and 10% glycerol had the highestconcentration of microbubbles post injection for all three needle sizes. Finally, phantom experiments were conducted tocalculate the signal-to-noise (SNR) ratios of the microbubbles with the different surfactant concentrations using a clinicalultrasound system.