Share Email Print

Proceedings Paper

Ultrasonic detection of photothermal interaction of lasers with tissue using a pulsed Doppler system
Author(s): Hao Ying; Aamer Azeemi; Craig J. Hartley; Massoud Motamedi; Brent A. Bell; Sohi Rastegar; L. C. Sheppard
Format Member Price Non-Member Price
PDF $17.00 $21.00

Paper Abstract

Thermal therapy using various heating sources such as lasers or microwaves to destroy benign and malignant lesions has recently gained widespread acceptance. However, the accurate prediction of thermal damage in tissue according to theoretical or computer modeling is difficult and unreliable due to target variability with respect to physical properties, geometry, and blood perfusion. Thus, one of the major obstacles to application of thermal therapies has been the lack of a noninvasive, real-time method that could determine the extent and geometry of treated tissue. To evaluate the effects of laser heating on tissue, we have developed an analog-digital hybrid Doppler ultrasound system to measure the phase and amplitude of ultrasonic echoes returned from the heated tissue. The system consists of an eight-gate pulsed Doppler detector, a 16-channel 12-bit A/D converter, and a signal analysis and visualization software package. In vitro studies using canine liver showed two distinct types of modulation of the echoes along the ultrasound beam path during laser irradiation using an 810 nm diode laser. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 1 signals showed a small and slow variation in amplitude and phase, and were attributed to tissue coagulation. Type 2 signals showed large and rapid variations in amplitude and phase which usually appeared after tissue surface explosion and were indicative of tissue ablation. We hypothesize that the observed phase changes in type 1 signals are due to thermal effects within the tissue consistent with tissue expansion and contraction while the phase changes in type 2 signals are likely due to formation and motion of gas bubbles in the tissue. A further development of the Doppler ultrasound technique could lead to the generation of feedback information needed for monitoring and automatic control of thermal treatment using various heating modalities such as laser, high intensity focused ultrasound, microwaves, or radio frequency waves.

Paper Details

Date Published: 22 May 1995
PDF: 7 pages
Proc. SPIE 2391, Laser-Tissue Interaction VI, (22 May 1995); doi: 10.1117/12.209918
Show Author Affiliations
Hao Ying, Univ. of Texas Medical Branch/Galveston (United States)
Aamer Azeemi, Texas A&M Univ. (United States)
Craig J. Hartley, Baylor College of Medicine (United States)
Massoud Motamedi, Univ. of Texas Medical Branch/Galveston (United States)
Brent A. Bell, Univ. of Texas Medical Branch/Galveston (United States)
Sohi Rastegar, Texas A&M Univ. (United States)
L. C. Sheppard, Univ. of Texas Medical Branch/Galveston (United States)

Published in SPIE Proceedings Vol. 2391:
Laser-Tissue Interaction VI
Steven L. Jacques, Editor(s)

© SPIE. Terms of Use
Back to Top
Sign in to read the full article
Create a free SPIE account to get access to
premium articles and original research
Forgot your username?