The ultimate objective of laser speckle flowmetry (and a host of specific implementations such as Laser Speckle Contrast Analysis -LASCA or LSCA, Laser Speckle Spatial Contrast Analysis -LSSCA, Laser Speckle Temporal Contrast Analysis -LSTCA, etc.) is to infer flow velocity from the observed speckle contrast. A proper inversion of this association depends critically on the correct model for the statistical relationship between motion of the scatterers and the resulting spatial and temporal speckle contrast. Many researchers use the Lorentzian model for such a relationship. In fact, the Lorentzian is a homogeneous line profile appropriate only for Brownian motion. In such a case, the dynamics of a single particle are representative of the ensemble. The other extreme is an inhomogeneous (Gaussian) profile which corresponds to a process in which the dynamics are particular to the individual scatterers. The proper model for complex motion such as blood flow is undoubtedly intermediate between these two extremes. One such model for the net effect of these two stochastically independent processes is a Voigt profile. In this paper we explore the quantitative relationship between the statistics of speckle contrast and ordered flow. The study addresses the effects of speckle size relative to that of the pixel, temporal integration time relative to the decorrelation times associated with ordered and un-ordered motion, and the spatio-temporal processing schemes used to quantify speckle contrast.

Abstract. The characterization of tissue morphology in murine models of pathogenesis has traditionally been carried out by excision of affected tissues with subsequent immunohistological examination. Excision-based histology provides a limited two-dimensional presentation of tissue morphology at the cost of halting disease progression at a single time point and sacrifice of the animal. We investigate the use of noninvasive reflectance mode confocal scanning laser microscopy ͑rCSLM͒ as an alternative tool to biopsy in documenting epidermal hyperplasia in murine models exposed to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate ͑TPA͒. An automated technique utilizing average axial rCSLM reflectance profiles is used to extract epidermal thickness values from rCSLM data cubes. In comparisons to epidermal thicknesses determined from hematoxylin and eosin ͑H&E͒ stained tissue sections, we find no significant correlation to rCSLM-derived thickness values. This results from method-specific artifacts: physical alterations of tissue during H&E preparation in standard histology and specimen-induced abberations in rCSLM imaging. Despite their disagreement, both histology and rCSLM methods reliably measure statistically significant thickness changes in response to TPA exposure. Our results demonstrate that in vivo rCSLM imaging provides epithelial biologists an accurate noninvasive means to monitor cutaneous pathogenesis.

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Herein, we discuss the remote assessment of the subwavelength organizational structure of a medium. Specifically, we use spectral imaging polarimetry, as the vector nature of polarized light enables it to interact with optical anisotropies within a medium, while the spectral aspect of polarization is sensitive to small-scale structure. The ability to image these effects allows for inference of spatial structural organization parameters. This work describes a methodology for revealing structural organization by exploiting the Stokes/Mueller formalism and by utilizing measurements from a spectral imaging polarimeter constructed from liquid crystal variable retarders and a liquid crystal tunable filter. We provide results to validate the system and then show results from measurements on a mineral sample.

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