Recent theoretical calculations by our group (2134-14) indicate that regional optical absorption of radiation within highly scattering media, such as biologic tissue, can be localized by detecting photo-acoustic waves that are produced during regional, optical absorption. This paper reports our initial experimental verification that measurable ultrasonic waves are produced when differential optical absorption takes place within turbid media simulating biologic tissue. For these experiments, an aquarium filled with a 0.5% intralipid solution was used to simulate the scattering properties of biologic tissue. Regional, optical absorption was produced by suspending black, latex spheres (3 - 10 mm diameter) within the intralipid bath. A broadband, xenon flash lamp (1 microsecond(s) ec rise time) was used for one set of experiments and a Nd:YAG laser ((lambda) equals 1064 nm, pulse width < 10 ns) was used for another set. A variety of focused, ultrasound transducers (0.5 - 2.5 MHz) were used successfully to detect and localize photo-acoustic waves. Lateral scanning of the transducers was used to localize the position of the absorption cells with a spatial resolution approximately 1 mm.

Date Published: 17 August 1994
PDF: 3 pages
Proc. SPIE 2134, Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards, (17 August 1994); doi: 10.1117/12.182926

Published in SPIE Proceedings Vol. 2134:
Laser-Tissue Interaction V; and Ultraviolet Radiation Hazards
Steven L. Jacques; David H. Sliney; Michael Belkin M.D., Editor(s)