Ara Ghazaryan

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We present an automated and systematic two-dimensional discrete Fourier transform (2D-FFT) approach to analyze collagen fiber organization through the use of second harmonic generation (SHG) microscopy. Average orientations of individual domains and Ising-like order parameters introduced to characterize the correlation between orientations of adjacent(More)
PURPOSE To qualify and quantify structural alterations in keratoconic corneas ex vivo by the use of second-harmonic generation (SHG) microscopy and two-dimensional fast Fourier transform (2D-FFT) analysis. METHODS Two keratoconic and three normal human corneal specimens were imaged with a multiphoton microscope. Forward and backward second-harmonic(More)
PURPOSE To evaluate the efficacy of using forward second harmonic generation (SHG) and 2-dimensional fast Fourier-transform (2D-FFT) analysis for the label-free characterization and quantification of morphologic changes in the corneal stroma after collagen crosslinking (CXL). SETTING Department of Physics, National Taiwan University, Taipei, Taiwan. (More)
Tissue glycation from diabetes and aging can result in complications such as renal failure, blindness, nerve damage and vascular diseases. In this work, we applied multiphoton microscopy for imaging and characterizing the extent of tissue glycation. The characteristic features of multiphoton autofluorescence (MPAF) and second harmonic generation (SHG)(More)
Photophysical mechanisms of collagen photomodification (CFP) by the use of a 80 MHz, 780 nm femtosecond titanium-sapphire laser were investigated. Our observation that the decrease in collagen second harmonic generation and increase in two-photon autofluorescence intensity occurred primarily at sites where photoproducts were present suggested that the(More)
BACKGROUND Tissue glycation, the main cause of many diabetes-related complications, results in the accumulation of advanced glycation endproducts (AGE). OBJECTIVES These AGEs are endogenous fluorophores that can serve as a viable pathological indicator for disease diagnostics. Here we explore the capabilities of multiphoton microscopy to non-invasively(More)
Oxidative-based diseases including diabetes, chronic renal failure, cardiovascular diseases and neurological disorders are accompanied by accumulation of advanced glycation endproducts (AGE). Therefore, AGE-associated changes in tissue optical properties could yield a viable pathological indicator for disease diagnostics and monitoring. We investigated(More)
We discuss the recent advances in the development and applications of second-order susceptibility as a contrast mechanism in optical microscopy for biological tissues. We review nonlinear optical methods and approaches for differentiation of tissue structures and discrimination of normal and pathological skin tissues, which have been demonstrated for the(More)
In recent years, two-photon excitation fluorescence and second harmonic generation microscopy has become an important tool in biomedical research. The ability of two-photon microscopy to achieve optical sectioning with minimal invasiveness is particularly advantageous for biomedical diagnosis. Advances in the miniaturization of the imaging system have(More)
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