Monitoring of soil aggregate breakdown remains, even at the micro-plot scale, a challenge. Remote sensing has shown its potential to assess many different soil properties and is a fast and non-destructive method to investigate soil susceptibility to water erosion. We designed an outdoor experiment to monitor soil aggregates breakdown under natural rainfall at a micro-plot scale using a regular camera. Five soils susceptible to detachment (silty loam with various organic matter content, loam and sandy loam) were photographed once per day. We collected images and rainfall data from November 2014 until February 2015. Considering that the soil surface roughness causes shadow cast, the blue/red band ratio is used to observe the soil aggregates changes. In addition, a Gray Level Co-occurrence Matrix (GLCM) is used to extract the image texture entropy which reflects the process of soil aggregates breakdown. In our research the entropy calculated at 135 degrees along the direction of shadows gives best results. Our results show that both entropy and shadow index follow the wetting and drying cycles with a decrease due to a rain event. This decrease is small due to low rainfall intensity (< 2.5 mmh-1) for the entire period that the experiment ran. However, the biggest rain event of 20 mmday-1 resulted in a decrease in entropy, meaning that sufficient rainfall energy was present to trigger the soil aggregates break down. This research concludes that both entropy and shadow index obtained with a regular camera enable the monitoring of soil aggregate breakdown at a high spatial resolution.
We determined the scattering coefficient and scattering anisotropy of blood samples with varying hematocrit using
optical coherence tomography measurements and a curve fitting procedure. Initial results show much lower scattering
coefficient and scattering anisotropy than theoretically expected, which are likely attributed to the highly forward
scattering nature of blood.
Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n and the attenuation coefficient µt using optical coherence tomography (OCT) of individual vascular wall layers and plaque components. Moreover, since the temperature dependence of optical properties is widely known, we compare measurements at room and body temperatures. A decrease of n and µt is observed in all samples, with the most profound effect on samples with high lipid content. The sample temperature is of influence on the quantitative measurements within OCT images. For extrapolation of ex-vivo experimental results, especially for structures with high lipid content, this effect should be taken into account.
Optical properties of tissues and tissue components are important parameters in biomedical optics. We report measurements of tissue refractive index n, and the attenuation coefficient μt using optical coherence tomography of individual vascular wall layers and plaque components. Moreover, since the temperature dependence of optical properties is widely known, we compared measurements at room and body temperatures. A decrease of n and μt was observed in all samples, with most profound effect on samples with high lipid content. The sample temperature is of influence on the quantitative measurements within OCT images. For extrapolation of ex vivo experimental results, especially for structures with high lipid content, this effect should be taken into account.
We determined the scattering coefficient and scattering anisotropy of blood samples with varying hematocrit using optical coherence tomography measurements and a curve fitting procedure. Initial results show much lower scattering coefficient and scattering anisotropy than theoretically expected. Alternative fitting strategies will be explored.
Optical coherence tomography (OCT) was used to determine optical properties of pelleted human fibroblasts in which necrosis or apoptosis was induced. We analyzed the OCT data including both the scattering properties of the medium and the axial point spread function of the OCT system. We measured that the optical attenuation coefficient in necrotic cells decreased from 2.2 ± 0.3 mm-1 to 1.3 ± 0.6 mm-1, whereas with the apoptotic cells a clear increase (up to 6.4 ± 1.7 mm-1) in scattering was observed.
The results on cultured cells a presented in this study indicate the ability of OCT to detect and differentiate between viable, apoptotic and necrotic cells based on their backscatter properties. This functional supplement to high-resolution OCT imaging can be of great clinical benefit, enabling on line monitoring of tissues, e.g. for feedback in cancer treatment.
Imaging of human autopsy samples was performed from the luminal side with a high (3.5 μm axial and 7 μm lateral) resolution OCT system (around 800 nm) or a regular (15-20 μm axial and 20 μm lateral resolution) OCT system (around 1300 nm). For each sample, dimensions were measured by histomorphometry and OCT and the optical attenuation was measured. Quantitative analysis showed a strong and significant correlation between OCT and histology cap thickness measurements for both OCT systems. For both systems, the measured attenuation coefficients of diffuse intimal thickening and lipid-rich regions differed significantly from media and calcifications. Both the high and regular resolution OCT systems can precisely image the atherosclerotic plaques. Quantitative analysis of the OCT signals allowed in situ determination of the intrinsic optical attenuation coefficient of atherosclerotic tissue components within regions of interest, which can further help to discriminate the plaque and arterial wall components.
Imaging of human autopsy samples was performed from the luminal side with a high (3.5 μm axial and 7 μm lateral) resolution OCT system (around 800 nm) or a regular (15-20 μm axial and 20 μm lateral resolution) OCT system (around 1300 nm). For each sample, dimensions were measured by histomorphometry and OCT and the optical attenuation was measured. Quantitative analysis showed a strong and significant correlation between OCT and histology cap thickness measurements for both OCT systems. For both systems, the measured attenuation coefficients of diffuse intimal thickening and lipid-rich regions differed significantly from media and calcifications. Both the high and regular resolution OCT systems can precisely image the atherosclerotic plaques. Quantitative analysis of the OCT signals allowed in situ determination of the intrinsic optical attenuation coefficient of atherosclerotic tissue components within regions of interest, which can further help to discriminate the plaque and arterial wall components.
KEYWORDS: Optical coherence tomography, Signal attenuation, Tissue optics, Tissues, Optical properties, Coherence imaging, Arteries, Backscatter, In vivo imaging, Imaging systems
The feasibility to detect and characterize vulnerable plaques by Optical Coherence Tomography (OCT) is currently under investigation. It has been shown that in some cases, by using qualitative criteria, the OCT images can be used to differentiate between different types of plaque. However, the quality of the image and the experience of the observer greatly influences the interpretation of the images, which indicates the necessity of a quantitative analysis of the OCT data. As OCT measures the depth resolved backscattering it is possible to calculate the light attenuation coefficient (μt) in the different areas in the image and use that to identify the different plaque constituents in the target tissue. In this study, we present in vitro data on μt, measured in atherosclerotic lesions.
We studied the axial point spread function of OCT for Gaussian intensity profiles emitted from and coupled back into single mode fibers for signals from a scattering medium. The determined Rayleigh length of the axial point spread function was roughly twice the one measured from the reflection of a mirror. Using the measured point spread function in combination with the single backscatter model allowed determination of the attenuation coefficient of the suspension.
A several kilometres thick sequence of mostly marine salt with inter-bedded gypsum, shale and dolomite rock of Pliocene to Pleistocene age build several salt diapirs in the Dead Sea area. The Lisan Peninsula salt diapir is elongated in the N-S direction, and includes several sub-domes and a structural depression. Differential interferograms were generated for several time intervals of seven to ninety three months between 1992 and 1999 and show a large diversity of uplift and subsidence features in the peninsula. The uplift rate, which has been measured, is in correspondence to the geological rate evaluated by other geological researches. The subsidence, mainly in the south dome and the cape are much more significant. Inversion deformation in the cape between the year 1995-1996 suggested to be linked to the 22 November 1995 Nuweiba earthquake. This paper suggested a tectonic mechanism connecting the salt deformation in the Lisan Peninsula with the activity of Boqeq fault.
The Dead Sea is very harsh environment even for microorganisms adapted to hypersaline environment. Not only does the Dead Sea contain the highest salt concentration of all natural lakes inhabited by living organisms, but the peculiar ionic composition of its water, with its high concentration of divalent cations magnesium and calcium, is highly inhibitory even to those microorganisms that are the most adapted to life in the sea. In this research imaging spectroscopy and microbiological studied used to investigate the spatial distribution of various Archaea populations according to the salty saturation of Mor swamp, Dead Sea Basin. Data from the DLR airborne sensor DAIS-7915 in the spectral range between 0.4 to 2.4 micrometers were acquired along with field and laboratory spectral measurements. The spatial and spectral data were completed by microbiological analysis. The spectral information helped to detect a concentric distribution of the Archaea population, which seems linked to the state of the salty substrate. In the wet muddy central zone lives an Archaea with the relatively lowest salt tolerance. From this centre to the peripheries, the tolerance to salt of the Archaea population was found to be increasing, as the substation changes from salty pools to salty muds and finally to massive salt layers.
The feasibility of using Optical Coherence Tomography (OCT) for oxygenation determination of whole blood was investigated on porcine blood samples. Our data show a sensitivity in the OCT spectral content to changes in oxygenation that qualitatively correspond to expectations based on the absorption spectra of oxidized hemoglobin and hemoglobin.
Apoptosis is the effector of regulated cell death and plays a role in many physiologic and pathologic processes. It is characterized by a highly regulated condensation and fragmentation of the cell nucleus, and breakup of the entire cell into vesicles, (apoptotic bodies) containing cell organelles and fragments of the nucleus. Previous experiments indicate that changes in optical properties after induction of apoptosis might be detected using optical imaging systems, such as optical coherence tomography (OCT), due to an increase in scattering of apoptotic cells. The previous in vitro experiments are extended to ex vivo and in vivo experiments. A nearly two-fold increase in attenuation coefficient is observed in a tissue culture of porcine carotid artery, in which apoptosis is induced by balloon dilation, and a significant 20 % increase in an in vivo setup. The preliminary results of this study indicate that the apoptotic process may also be detected ex vivo and in vivo using optical imaging systems, such as optical coherence tomography (OCT), due to an increase in scattering by the typical disintegration of cellular material.
The feasibility of Optical Coherence Tomography to determine the oxygenation of whole blood was investigated on porcine blood samples. Our experimental data show a sensitivity in the OCT spectral content to changes in oxygenation that qualitatively correspond to expectations based on the absorption spectra of oxidized and reduced hemoglobin, using a broadband source operating at the isobestic wavelength of 800 nm.
Apoptosis is the effector of regulated cell death and plays a role in many physiologic and pathologic processes. It is characterized by a highly regulated condensation and fragmentation of the cell nucleus, a large scatterer, and breakup of the entire cell into vesicles, (apoptotic bodies) containing cell organelles and fragments of the nucleus. A two-fold increase in attenuation coefficient ((mu) ) is observed in cell culture after chemical induction of apoptosis. An identical increase in scattering is observed in a tissue culture of porcine carotid artery, in which apoptosis is induced by balloon dilation. These observations are theoretically supported by calculations based on MIE theory. The preliminary results of this study indicate that the apoptotic process may be detected using OCT due to an increase in scattering by the typical disintegration of cellular material. The described increase in scattering may also be detected by other optical techniques.
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