Ultrasonic doppler detection of laser-tissue interaction

Craig J. Hartley, Hao Ying, Massoud Motamedi

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)655-663
Number of pages9
JournalUltrasound in Medicine and Biology
Volume20
Issue number7
DOIs
StatePublished - 1994
Externally publishedYes

Fingerprint

Ultrasonics
Lasers
ultrasonics
lasers
interactions
Acoustics
Tissue Expansion
Semiconductor Lasers
Volatilization
Laser Therapy
acoustic properties
Transducers
coagulation
muscles
liver
lesions
ablation
contraction
fiber lasers
signal processing

Keywords

  • Contrast effect
  • Doppler signal processing
  • Laser ablation
  • Laser coagulation
  • Phase and amplitude modulation
  • Pulsed Doppler ultrasound
  • Scattering
  • Spectral analysis
  • Tissue motion

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

Ultrasonic doppler detection of laser-tissue interaction. / Hartley, Craig J.; Ying, Hao; Motamedi, Massoud.

In: Ultrasound in Medicine and Biology, Vol. 20, No. 7, 1994, p. 655-663.

Research output: Contribution to journalArticle

Hartley, Craig J. ; Ying, Hao ; Motamedi, Massoud. / Ultrasonic doppler detection of laser-tissue interaction. In: Ultrasound in Medicine and Biology. 1994 ; Vol. 20, No. 7. pp. 655-663.
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