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Speckle phenomena in optics12/10/2023 Finally, the key power-law parameter estimated from speckle is capable of discriminating between tissues and thus introduces a new biomarker for clinical use. A comparison of the new distributions with distributions found in the literature are presented based on clinically relevant ex vivo and in vivo samples, and the power-law distributions are shown to provide a superior description of the speckle statistics. Metrics for assessing appropriate regions of interest (ROIs) and evaluating the statistical validity of the distributions are also presented. In this paper, this novel framework for speckle is extended to OCT scans of various biological tissues. These were the Burr type XII distribution, the Lomax distribution, and the generalized logistic distribution. The results apply generally to multi-scale distributions of scattererers and three new and distinct probability distributions were found to characterize ultrasound speckle in biological tissue. Recently, a new model hypothesized that in normal soft tissue, the dominant scattering elements are cylinders from fractal branching vasculature. Īlthough OCT is an interferometric technique and ultrasound utilizes time-of-flight measurements, the mathematics describing wave propagation and wave phenomena such as speckle can be applicable to both acoustical and optical imaging modalities. Studies of speckle amplitude statistics in acoustics and optics have led to the usage of various probability density functions (PDFs) such as the Rayleigh distribution, the K distribution, the Rice distribution, gamma distributions, and many others. Other studies choose to utilize speckle for physical modeling or characterization of tissue samples. For some applications such as high-resolution imaging, speckle is considered to be undesirable noise and many studies attempt to eliminate its presence. Optical coherence tomography (OCT) and ultrasound are two medical imaging modalities with prominent speckle. The study of speckle phenomena has a long history dating back to the time of Isaac Newton, with an increasing multitude of recent applications in optics, radar, and ultrasound. Speckle is a granular pattern seen in signals or images that is caused by the interference of coherent waves with random phases and known or random amplitudes. Thus, the overall framework brings to the field new biomarkers from OCT measures of speckle in tissues, grounded in basic biophysics and with wide applications to diagnostic imaging in clinical use. The results indicate that across OCT datasets of various tissue types, the proposed power-law distributions are more appropriate models yielding novel parameters for characterizing the physics of scattering from biological tissue. The distributions are also compared with classical models such as the Rayleigh, K, and gamma distributions. Experimentally, these three distributions are fitted to histogram data from nine optical coherence tomography scans of various samples and biological tissues, in vivo and ex vivo. Specifically, these are the Burr type XII distribution for speckle amplitude, the Lomax distribution for intensity, and the generalized logistic distribution for log amplitude. Thus, multi-scale scattering sites including the fractal branching vasculature will contribute to power-law probability distributions of speckle statistics. Here, we propose a new theoretical framework based on power-law functions, where we hypothesize that an underlying power-law distribution governs scattering from tissues. As with the first edition, a multitude of areas of application are covered.The speckle statistics of optical coherence tomography images of biological tissue have been studied using several historical probability density functions. This second edition offers improvements of several topics and addition of significant amounts of new material, including discussion of: generalized random walks, speckle in the eye, polarization speckle (and the statistics of the Stokes parameters in a speckle pattern), the effects of angle and wavelength changes on speckle, the statistics of speckle from "smooth" surfaces, and a spectrometer based on speckle. This book provides comprehensive coverage of this subject, including both the underlying statistical theory and the applications of this phenomenon. Speckle, a granular structure appearing in images and diffraction patterns produced by objects that are rough on the scale of an optical wavelength, is a ubiquitous phenomenon, appearing in optics, acoustics, microwaves, and other fields. Bibliography Includes bibliographical references and index Publisher's summary
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