title: Changes in lipid-encapsulated microbubble population during continuous infusion and methods to maintain consistency.
abstract: Stabilized microbubbles are used as ultrasound contrast agents. These micron-sized gas capsules are injected into the bloodstream to provide contrast enhancement during ultrasound imaging. Some contrast imaging strategies, such as destruction-reperfusion, require a continuous injection of microbubbles over several minutes. Most quantitative imaging strategies rely on the ability to administer a consistent dose of contrast agent. Because of the buoyancy of these gas-filled agents, their spatial distribution within a syringe changes over time. The population of microbubbles that is pumped from a horizontal syringe outlet differs from initial population as the microbubbles float to the syringe top. In this manuscript, we study the changes in the population of a contrast agent that is pumped from a syringe caused by microbubble flotation. Results are presented in terms of change in concentration and change in mean diameter, as a function of time, suspension medium and syringe diameter. Data illustrate that the distribution of contrast agents injected from a syringe changes in both concentration and mean diameter over several minutes without mixing. We discuss the application of a mixing system and viscosity agents to keep the contrast solution more evenly distributed in a syringe. These results are significant for researchers using microbubble contrast agents in continuous-infusion applications where it is important to maintain consistent contrast agent delivery rate, or in situations where the injection syringe cannot be mixed immediately before administration.
authors.affiliation: Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Kaya
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Gregory
authors.forename: Paul A
authors.initials: PA
authors.lastname: Dayton
mesh_terms: D003287:Contrast Media / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D006801:Humans; D007262:Infusions, Intravenous; D008055:Lipids / Q000008:administration & dosage*; D045423:Microbubbles; D008962:Models, Theoretical; D010316:Particle Size; D012212:Rheology; D013594:Syringes; D014463:Ultrasonography / Q000379:methods; D014783:Viscosity
chemical_list: D003287:Contrast Media; D008055:Lipids