Our studies are directed towards the development of a pulsed laser based optoacoustic technique to visualize absorbed light distribution in irradiated tissues. Optoacoustic technique utilizes the time-resolved detection of laser-induced stress transients to visualize absorbed laser fluence distribution in opaque and heterogeneous tissues. The acoustic signal induced under confined stress conditions of irradiation by an Nd:YAG laser pulse displays Z-axial light distribution and may be used for imaging the tissue layers where a temperature-rise of about 1 degree(s)C is achieved. Scanning of the acoustic transducer along the tissue surface line by line until entire surface of interest is tested, permits reconstruction of a 3D optoacoustic image of the irradiated tissue. Z-axial resolution of optoacoustic imaging is defined as a product of the temporal resolution of piezoelectric transducer and the speed of sound in tissues. Lateral (radial) resolution of optoacoustic images is a funtion of piezoelectric detector diameter, the diameter of laser-induced acoustic wave, and a depth of optoacoustic probing (acoustic diffraction factor). The role of various parameters, such as tissue optical properties, tissue thickness, laser beam diameter, and diameter of piezoelectric element, were evaluated for imaging resolution in lateral direction. The results of our studies demonstrated that a broad- band acoustic transducer may become a useful tool for in vivo diagnostic imaging and feed- back information during clinical laser procedures. First in vivo measurements were performed and found to be in agreement with tissue histology. This study is a very first step in the basic design of optoacoustic tomographic technology for light absorbing tissues.

Date Published: 30 May 1995
PDF: 11 pages
Proc. SPIE 2389, Optical Tomography, Photon Migration, and Spectroscopy of Tissue and Model Media: Theory, Human Studies, and Instrumentation, (30 May 1995); doi: 10.1117/12.209986

Published in SPIE Proceedings Vol. 2389:
Optical Tomography, Photon Migration, and Spectroscopy of Tissue and Model Media: Theory, Human Studies, and Instrumentation
Britton Chance; Robert R. Alfano, Editor(s)