Time-resolved light scattering and fluorescence spectroscopy in biomedical and model random media.
Item
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Title
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Time-resolved light scattering and fluorescence spectroscopy in biomedical and model random media.
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Identifier
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AAI9405516
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identifier
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9405516
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Creator
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Das, Bidyut Baran.
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Contributor
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Adviser: R. R. Alfano
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Optics | Engineering, Biomedical | Engineering, Electronics and Electrical
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Abstract
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Optical spectroscopy, light scattering and ultrafast time-gated imaging have been shown to offer novel approaches to study the optical characteristics of various biomedical and other random media.;Fluorescence spectra from human malignant and nonmalignant breast tissues were measured at 300 nm excitation and a significant spectral difference was found between the two tissue types by using the ratio of fluorescence intensities at 340 and 440 nm.;Optical density measurements on thin breast tissues show that the scattering cross-sections of breast tissues are relatively constant over the visible and the uv region.;Transport mean free paths and the absorption lengths for various tissues and model random media were measured using time-resolved transmission. The scattering coefficients for human breast and chicken tissues were found to remain relatively constant in 570-630 nm wavelength region while they change significantly at 1064 nm. Chicken breast and fat tissues were found to be good models for human breast tissues as the values of the optical parameters of the two tissue types are about the same. The less scattering observed at 1064 nm makes tissues more transparent in the NIR region making it easier to image in thick tissues.;Time-resolved backscattering measurements show that the scattering and the absorption parameters of a random medium can be obtained accurately in a two-fiber configuration as long as the radial distance is more than about seven times the transport mean free path of the sample. The single point source-detection configuration provides a tool to diagnose breast malignancy though it fails to give accurate values of the optical parameters of tissues. This failure is attributed to the invalidity of the diffusion approximation in this experimental configuration.;A 2.5 mm thin chicken fat strip was imaged inside a 40 mm thick chicken breast tissue using snake photons at 625 nm with ultrafast time-gated detection.;A simple model to describe the effect of small objects embedded inside a highly scattering medium on the attenuation of snake photons is developed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
