Document Detail

Different effects of microbubble destruction and translation in Doppler measurements.
MedLine Citation:
PMID:  16212258     Owner:  NLM     Status:  MEDLINE    
In flow measurements in which microbubbles are involved, the amplitude and phase of the received echo signal are noticeably influenced by the transmitted ultrasound intensity. Previous studies have shown that, when such intensity is progressively increased, the Doppler spectrum is accordingly distorted, i.e., it is asymmetrically broadened toward the negative frequency side. Such deformation has been attributed to radiation force, which pushes the microbubbles into the sound propagation direction, thus yielding additional phase delays in the received echoes. However, the possible contribution of microbubble destruction to this spectral deformation has not been considered yet. In this paper, this issue is investigated by analyzing the experimental spectra produced by two different types of microbubbles suspended in a moving fluid and insonified in pulsed wave (PW) mode at programmable pulse repetition frequency (PRF) and pressure. Conditions are created in which either the radiation force or the destruction mechanism is expected to be dominant. Effects produced by the two phenomena on the Doppler spectrum are shown to be different. When the PRF is low (2 kHz), so that, according to theoretical simulations, the radiation force effect is negligible, a 26 dB noise floor increase is observed for a 13 dB pressure increment. For a higher PRF (16 kHz), the same pressure increase not only affects the noise floor, but also causes the bubbles to deviate from their original streamlines, yielding a Doppler bandwidth increase by a factor of 5. It is concluded that asymmetrical spectral broadening is mainly due to radiation force, and microbubble destruction mainly results in an increased noise floor without affecting the spectral shape.
Piero Tortoli; Enrico Boni; Massimo Corsi; Marcel Arditi; Peter Frinking
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Publication Detail:
Type:  Letter; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  IEEE transactions on ultrasonics, ferroelectrics, and frequency control     Volume:  52     ISSN:  0885-3010     ISO Abbreviation:  IEEE Trans Ultrason Ferroelectr Freq Control     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-10-10     Completed Date:  2005-11-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9882735     Medline TA:  IEEE Trans Ultrason Ferroelectr Freq Control     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1183-8     Citation Subset:  IM    
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MeSH Terms
Contrast Media*
Echocardiography / instrumentation,  methods*
Echocardiography, Doppler / instrumentation,  methods*
Image Enhancement / methods*
Image Interpretation, Computer-Assisted / methods*
Phantoms, Imaging
Reg. No./Substance:
0/Contrast Media

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