Document Detail

Ultrasonic Doppler detection of laser-tissue interaction.
MedLine Citation:
PMID:  7810026     Owner:  NLM     Status:  MEDLINE    
Laser therapy for the safe and effective coagulation and ablation of tissues requires precise control of the amount of energy delivered to and absorbed by the volume of tissue of interest. We propose that an ultrasonic transducer pointing in the same direction as the laser fiber could be used to monitor the changes in ultrasonic properties caused by the absorption of light by the tissue. A modified 20 MHz pulsed Doppler was used to evaluate the ultrasonic effects of 35 exposures of beef liver and muscle to a high power diode laser in vitro in real time. We found two distinct levels of acoustic activity in the tissue. Type 1 activity consisted of slow variations in the phase and small changes in the amplitude of the echoes, while type 2 activity consisted of large and rapid fluctuations in amplitude and phase. We found that the residual increase in echogenicity of the tissue and the delay to the onset of type 2 activity were functions of laser power and tissue type and were correlated to lesion severity. We hypothesize that type 1 activity corresponds to motion (thermal expansion and contraction) of the tissue, and that type 2 activity corresponds to the creation of gas bubbles (vaporization) in the tissue. We conclude that the absorption of energy changes the acoustic properties of tissue during and after exposure and that Doppler signal processing can be used to differentiate various levels of laser-tissue interaction in real time.
C J Hartley; H Ying; M Motamedi
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Ultrasound in medicine & biology     Volume:  20     ISSN:  0301-5629     ISO Abbreviation:  Ultrasound Med Biol     Publication Date:  1994  
Date Detail:
Created Date:  1995-02-02     Completed Date:  1995-02-02     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0410553     Medline TA:  Ultrasound Med Biol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  655-63     Citation Subset:  IM    
Department of Medicine, Baylor College of Medicine, Houston, TX 77030.
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MeSH Terms
Laser Therapy*
Liver / surgery,  ultrasonography
Muscles / surgery,  ultrasonography
Ultrasonography, Doppler*
Grant Support

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