Document Detail

Acoustic response of compliable microvessels containing ultrasound contrast agents.
MedLine Citation:
PMID:  17019026     Owner:  NLM     Status:  MEDLINE    
The existing models of the dynamics of ultrasound contrast agents (UCAs) have largely been focused on an UCA surrounded by an infinite liquid. Preliminary investigations of a microbubble's oscillation in a rigid tube have been performed using linear perturbation, under the assumption that the tube diameter is significantly larger than the UCA diameter. In the potential application of drug and gene delivery, it may be desirable to fragment the agent shell within small blood vessels and in some cases to rupture the vessel wall, releasing drugs and genes at the site. The effect of a compliant small blood vessel on the UCA's oscillation and the microvessel's acoustic response are unknown. The aim of this work is to propose a lumped-parameter model to study the interaction of a microbubble oscillation and compliable microvessels. Numerical results demonstrate that in the presence of UCAs, the transmural pressure through the blood vessel substantially increases and thus the vascular permeability is predicted to be enhanced. For a microbubble within an 8 to 40 microm vessel with a peak negative pressure of 0.1 MPa and a centre frequency of 1 MHz, small changes in the microbubble oscillation frequency and maximum diameter are observed. When the ultrasound pressure increases, strong nonlinear oscillation occurs, with an increased circumferential stress on the vessel. For a compliable vessel with a diameter equal to or greater than 8 microm, 0.2 MPa PNP at 1 MHz is predicted to be sufficient for microbubble fragmentation regardless of the vessel diameter; however, for a rigid vessel 0.5 MPa PNP at 1 MHz may not be sufficient to fragment the bubbles. For a centre frequency of 1 MHz, a peak negative pressure of 0.5 MPa is predicted to be sufficient to exceed the stress threshold for vascular rupture in a small (diameter less than 15 microm) compliant vessel. As the vessel or surrounding tissue becomes more rigid, the UCA oscillation and vessel dilation decrease; however the circumferential stress is predicted to increase. Decreasing the vessel size or the centre frequency increases the circumferential stress. For the two frequencies considered in this work, the circumferential stress does not scale as the inverse of the square root of the acoustic frequency va as in the mechanical index, but rather has a stronger frequency dependence, 1/va.
Shengping Qin; Katherine W Ferrara
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2006-09-22
Journal Detail:
Title:  Physics in medicine and biology     Volume:  51     ISSN:  0031-9155     ISO Abbreviation:  Phys Med Biol     Publication Date:  2006 Oct 
Date Detail:
Created Date:  2006-10-04     Completed Date:  2006-12-21     Revised Date:  2014-09-12    
Medline Journal Info:
Nlm Unique ID:  0401220     Medline TA:  Phys Med Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  5065-88     Citation Subset:  IM    
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MeSH Terms
Contrast Media*
Echocardiography / methods*
Image Enhancement / methods*
Image Interpretation, Computer-Assisted / methods*
Microcirculation / physiology*,  ultrasonography*
Models, Cardiovascular*
Particle Size
Stress, Mechanical
Grant Support
CA 103828/CA/NCI NIH HHS; CA 76062/CA/NCI NIH HHS; R01 CA076062/CA/NCI NIH HHS; R01 CA076062-06/CA/NCI NIH HHS; R01 CA103828/CA/NCI NIH HHS; R01 CA103828-05/CA/NCI NIH HHS
Reg. No./Substance:
0/Contrast Media

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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