Document Detail

On the relationship between encapsulated ultrasound contrast agent and pressure.
MedLine Citation:
PMID:  15866417     Owner:  NLM     Status:  MEDLINE    
Noninvasive measurement of pressure within the heart cavities and other internal organs (e.g., kidney, liver) has significant clinical value, but currently is not feasible. Noninvasive pressure estimation using encapsulated ultrasound (US) contrast agents (UCA) as sensors is a challenge because they supposedly respond to their ambient pressure, but they are more rigid and less sensitive to pressure than gas microbubbles. Here, Optison sensitivity was studied (f(resonance) = approximately 2 MHz) to varying pressures, when excited at 2 times and also at 0.5 times f(resonance). Cyclic momentary increases in ambient pressure of 0 to 5, 0 to 10, 0 to 15 or 0 to 20 kPa at 1.0 Hz, mimicking left ventricular (LV) pressure changes, caused amplitude decrease of echoes at 0.5, 1 and 2 times the transmitted frequency and decrease of attenuation. Changes at 0.5 times the transmitted frequency correlated best, but only after 70 to 150 s. The correlations (mean +/- SD) during 150 to 300 s were 0.706 +/- 0.072 for 0 to 10 kPa, 0.844 +/- 0.042 for 0 to 15 kPa and 0.859 +/- 0.031 for 0 to 20 kPa. Attenuation presented less correlation. For 1.0 Hz, 10 to 15 kPa or 15 to 20 kPa pressures, mimicking systemic pressures, the attenuation decayed fast and even faster for slow (0.05 Hz) cyclic varying pressures, or elevated steady-state pressures (of 10 kPa and 20 kPa). Thus, cyclic pressure effects on UCA are demonstrated to be reversible, but elevated static pressures cause UCA destruction. This allows cyclic pressure variations to be detected, using the subharmonics of the transmitted frequency, down to 10 kPa.
Dan Adam; Michal Sapunar; Elina Burla
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Ultrasound in medicine & biology     Volume:  31     ISSN:  0301-5629     ISO Abbreviation:  Ultrasound Med Biol     Publication Date:  2005 May 
Date Detail:
Created Date:  2005-05-03     Completed Date:  2005-10-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0410553     Medline TA:  Ultrasound Med Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  673-86     Citation Subset:  IM    
Department of Biomedical Engineering, Technion-I.I.T., Haifa 32000, Israel.
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MeSH Terms
Blood Pressure / physiology*
Contrast Media*
Coronary Circulation / physiology
Echocardiography / methods
Image Processing, Computer-Assisted / methods
Models, Cardiovascular
Reg. No./Substance:
0/Albumins; 0/Contrast Media; 0/FS 069; 0/Fluorocarbons

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