1,721,048 research outputs found
Ultrahigh resolution optical coherence elastography using a Bessel beam for extended depth of field
No full textVisualizing stiffness within the local tissue environment at the cellular and sub-cellular level promises to provide insight into the genesis and progression of disease. In this paper, we propose ultrahigh-resolution optical coherence elastography, and demonstrate three-dimensional imaging of local axial strain of tissues undergoing compressive loading. The technique employs a dual-arm extended focus optical coherence microscope to measure tissue displacement under compression. The system uses a broad bandwidth supercontinuum source for ultrahigh axial resolution, Bessel beam illumination and Gaussian beam detection, maintaining sub-2 μm transverse resolution over nearly 100 μm depth of field, and spectral-domain detection allowing high displacement sensitivity. The system produces strain elastograms with a record resolution (x,y,z) of 2×2×15 μm. We benchmark the advances in terms of resolution and strain sensitivity by imaging a suitable inclusion phantom. We also demonstrate this performance on freshly excised mouse aorta and reveal the mechanical heterogeneity of vascular smooth muscle cells and elastin sheets, otherwise unresolved in a typical, lower resolution optical coherence elastography system
Modeling the optical coherence tomography geometry using the extended Huygens-Fresnel principle and Monte Carlo simulations
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Two-photon fluorescence correlation microscopy for biophysical studies
No full textTwo-photon correlation spectroscopy enables the deeper insight into the living tissue in comparison to single photon spectroscopy and visualise the biophysical processes occuring there. We present the basic features of an experimental set-up based on a research Nikon microscope and preliminary experimental results of suitable dye with two-photon excitation for pharmacokinetic studies. Despite some technical problems the proposed design differs by its simplicity, requires relatively low-cost optics and has a reasonably low dispersion on the optical elements
Investigating the utility of refractive index tomography based on OCT
No full textWe describe tomographic imaging of the refractive index of turbid media based on optical coherence tomography (OCT). We describe a variant OCT technique, bifocal optical coherence refractometry (BOCR), in which the optical pathlength difference between two foci simultaneously present in a medium of interest is measured. This technique is potentially suitable for dynamic measurements of the refractive index of biological tissues. We describe different schemes for realization of BOCR including one based on an adaptive liquid-crystal lens. We present experimental results from a range of tissue phantoms and from human skin in vivo that demonstrate the unique possibilities of BOCR for refractive index tomography, including its intrinsic immunity to motion artefacts and suitability for dynamic measurements
Refractive index tomography of turbid media by bifocal optical coherence refractometry
No full textWe demonstrate tomographic imaging of the refractive index of turbid media using bifocal optical coherence refractometry (BOCR). The technique, which is a variant of optical coherence tomography, is based on the measurement of the optical pathlength difference between two foci simultaneously present in a medium of interest. We describe a new method to axially shift the bifocal optical pathlength that avoids the need to physically relocate the objective lens or the sample during an axial scan, and present an experimental realization based on an adaptive liquid-crystal lens. We present experimental results, including video clips, which demonstrate refractive index tomography of a range of turbid liquid phantoms, as well as of human skin in vivo
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