期刊
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
卷 122, 期 2, 页码 1191-1200出版社
ACOUSTICAL SOC AMER AMER INST PHYSICS
DOI: 10.1121/1.2747204
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资金
- NCI NIH HHS [CA 103828] Funding Source: Medline
- PHS HHS [112356] Funding Source: Medline
Many thousands of contrast ultrasound studies have been conducted in clinics around the world. In addition, the microbubbles employed in these examinations are being widely investigated to deliver drugs and genes. Here, for the first time, the oscillation of these microbubbles in small vessels is directly observed and shown to be substantially different than that predicted by previous models and imaged within large fluid volumes. Using pulsed ultrasound with a center frequency of 1 MHz and peak rarefactional pressure of 0.8 or 2.0 MPa, microbubble expansion was significantly reduced when microbubbles were constrained within small vessels in the rat cecum (P < 0.05). A model for microbubble oscillation within compliant vessels is presented that accurately predicts oscillation and vessel displacement within small vessels. As a result of the decreased oscillation in small vessels, a large resting microbubble diameter resulting from agent fusion or a high mechanical index was required to bring the agent shell into contact with the endothelium. Also, contact with the endothelium was observed during asymmetrical collapse, not during expansion. These results will be used to improve the design of drug delivery techniques using microbubbles. (C) 2007 Acoustical Society of America.
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