Reflectance spectroscopy for diagnosis of precancerous changes in human epithelium

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1998.Includes bibliographical references.by Vadim Backman.M.S

Early diagnosis of cancer using LSS

Thesis (Ph. D.)--Harvard--Massachusetts Institute of Technology Division of Health Sciences and Technology, 2001.Includes bibliographical references.This thesis presents a novel optical technique, light scattering spectroscopy (LSS), developed for quantitative characterization of tissue morphology as well as in vivo detection and diagnosis of the diseases associated with alteration of normal tissue structure such as precancerous and early cancerous transformations in various epithelia. LSS employs a wavelength dependent component of light scattered by epithelial cells to obtain information about subcellular structures, such as cell nuclei. Since nuclear atypia is one of the hallmarks of precancerous and cancerous changes in most human tissues, the technique has the potential to provide a broadly applicable means of detecting epithelial precancerous lesions and noninvasive cancers in various organs, which can be optically accessed either directly or by means of optical fibers. We have developed several types of LSS instrumentation including 1) endoscopically compatible LSS-based fiber-optic system;(cont.) 2) LSS-based imaging instrumentation, which allows mapping quantitative parameters characterizing nuclear properties over wide, several cm2, areas of epithelial lining; and 3) scattering angle sensitive LSS instrumentation (a/LSS), which enables to study the internal structure of cells and their organelles, i.e. nuclei, on a submicron scale. Multipatient clinical studies conducted to test the diagnostic potential of LSS in five organs (esophagus, colon, bladder, cervix and oral cavity) have shown the generality and efficacy of the technique and indicated that LSS may become an important tool for early cancer detection as well as better biological understanding of the disease.by Vadim Backman.Ph.D

Determination of particle size by using the angular distribution of backscattered light as measured with low-coherence interferometry

We employ a novel interferometer to measure the angular distribution of light backscattered by a turbid medium. Through comparison of the measured data with the predictions of Mie theory, we are able to determine the size of the scatterers comprising the medium with subwavelength precision. As the technique is based on low-coherence interferometry, we are able to examine the evolution of the angular distribution of scattered light as it propagates into the medium. The effects of multiple scattering as a function of penetration depth in the medium are analyzed. We also present various considerations for extending this technique to determining structural information in biological tissues, such as the effects of a distribution of particle sizes and the need to average out speckle contributions

Bleaching Response of Coral Species in the Context of Assemblage Response

Caribbean coral reefs are declining due to a mosaic of local and global stresses, including climate change-induced thermal stress. Species and assemblage responses differ due to factors that are not easily identifiable or quantifiable. We calculated a novel species-specific metric of coral bleaching response, taxon-α and -β, which relates the response of a species to that of its assemblages for 16 species over 18 assemblages. By contextualizing species responses within the response of their assemblages, the effects of environmental factors are removed and intrinsic differences among taxa are revealed. Most corals experience either a saturation response, overly sensitive to weak stress (α \u3e 0) but under-responsive compared to assemblage bleaching (β \u3c 1), or a threshold response, insensitive to weak stress (α \u3c 0) but over-responsive compared to assemblage bleaching (β \u3e 1). This metric may help reveal key factors of bleaching susceptibility and identify species as targets for conservation