title: Interactions between microbubbles and ultrasound: in vitro and in vivo observations.
abstract: OBJECTIVE
  We attempted to examine the interactions between ultrasound and microbubbles.
  
  
  BACKGROUND
  The interactions between microbubbles and ultrasound are poorly understood. We hypothesized that 1) ultrasound destroys microbubbles, and 2) this destruction can be minimized by limiting the exposure of microbubbles to ultrasound.
  
  
  METHODS
  We performed in vitro and in vivo experiments in which microbubbles were insonated at different frequencies, transmission powers and pulsing intervals. Video intensity decay was measured in vitro and confirmed by measurements of microbubble size and concentrations. Peak video intensity and mean microbubble myocardial transit rates were measured in vivo.
  
  
  RESULTS
  Imaging at lower frequencies and higher transmission powers resulted in more rapid video intensity decay (p = 0.01), and decreasing exposure of microbubbles to ultrasound minimized their destruction in vitro. Although these effects were also noted in vivo with venous injections of microbubbles, they were not seen with aortic root or direct coronary artery injections.
  
  
  CONCLUSIONS
  Ultrasound results in microbubble destruction that is more evident at lower frequencies and higher acoustic powers. Reducing the exposure of microbubbles to ultrasound minimizes their destruction. This effect is most marked in vivo with venous rather than aortic or direct coronary injections of microbubbles. These findings could lead to effective strategies for myocardial perfusion imaging with venous injections of microbubbles.
authors.affiliation: Cardiovascular Division, University of Virginia, Charlottesville 22908, USA.
authors.forename: K
authors.initials: K
authors.lastname: Wei
authors.forename: D M
authors.initials: DM
authors.lastname: Skyba
authors.forename: C
authors.initials: C
authors.lastname: Firschke
authors.forename: A R
authors.initials: AR
authors.lastname: Jayaweera
authors.forename: J R
authors.initials: JR
authors.lastname: Lindner
authors.forename: S
authors.initials: S
authors.lastname: Kaul
mesh_terms: D000418:Albumins; D000818:Animals; D003287:Contrast Media; D004285:Dogs; D004452:Echocardiography / Q000379:methods*; D005466:Fluorocarbons; D007091:Image Processing, Computer-Assisted; D008863:Microspheres; D009206:Myocardium / Q000378:metabolism; D013010:Sonication; D013997:Time Factors; D014741:Video Recording
chemical_list: D000418:Albumins; C060687:Albunex; D003287:Contrast Media; C099458:FS 069; D005466:Fluorocarbons