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Proceedings Paper

Ultrashort laser pulse propagation and imaging in biological tissue and model random media: steps towards optical mammography
Author(s): K. M. Yoo
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Paper Abstract

Ultrashort laser pulses passing through a random turbid medium are temporally spread into ballistic, snake, and diffuse components. The intensity and the speed of the ballistic pulse are found to depend on the scattering characteristics of the medium. The diffuse component can be approximated by the diffusion theory when the laser pulse propagates through a distance of more than 10 transport mean free path. The early arriving portion of the diffuse pulse, known as the snake component, consists of photons that propagate along zig-zag paths slightly off the straight path. The attenuation of the snake photon depends on the transport mean free path of the random medium and it decreases exponentially as its thickness increases. However, the snake photon attenuates much more slowly than the ballistic photon. Snake photons have to be used for time-resolved imaging through a thick biological tissue. Ultrafast time-resolved detection of ballistic and snake photons are illustrated for locating opaque and translucent objects hidden in highly scattering media. A thin slab of chicken fat tissue (2.5 mm thick) embedded inside a thick chicken breast tissue (40 mm) has been located by detecting snake photons at X.625 nm. Near infrared light is scattered less in tissue and can be used to image through a significantly thicker tissue. The current ultrashort pulse lasers and ultrafast time-resolved detection techniques can be potentially used to image tumors in a breast.

Paper Details

Date Published: 5 August 1993
PDF: 25 pages
Proc. SPIE 10311, Medical Optical Tomography: Functional Imaging and Monitoring, 103110P (5 August 1993); doi: 10.1117/12.2283770
Show Author Affiliations
K. M. Yoo, The City College of New York (United States)
The Hong Kong Univ. of Science and Technology (Hong Kong, China)

Published in SPIE Proceedings Vol. 10311:
Medical Optical Tomography: Functional Imaging and Monitoring
Gerhard J. Mueller, Editor(s)

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