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Phase Contrast (phase + contrast)
Terms modified by Phase Contrast Selected AbstractsRapid quantitation of cardiovascular flow using slice-selective fourier velocity encoding with spiral readoutsMAGNETIC RESONANCE IN MEDICINE, Issue 4 2007Joao L. A. Carvalho Abstract Accurate flow visualization and quantitation is important for the assessment of many cardiovascular conditions such as valvular stenosis and regurgitation. Phase contrast based methods experience partial volume artifacts when flow is highly localized, complex and/or turbulent. Fourier velocity encoding (FVE) avoids such problems by resolving the full velocity distribution within each voxel. This work proposes the use of slice selective FVE with spiral readouts to acquire fully localized velocity distributions in a short breath-hold. Scan-plane prescription is performed using classic protocols, and an automatic algorithm is used for in-plane localization of the flow. Time and spatially-resolved aortic valve velocity distributions with 26-msec temporal resolution and 25 cm/sec velocity resolution over a 600 cm/sec field-of-view were acquired in a 12-heartbeat breath-hold. In carotid studies, scan time was extended to achieve higher spatial resolution. The method was demonstrated in healthy volunteers and patients, and the results compared qualitatively well with Doppler ultrasound. Acquisition time could be reduced to 7 heartbeats (a 42% reduction) using partial Fourier reconstruction along the velocity dimension. Magn Reson Med 57:639,646, 2007. © 2007 Wiley-Liss, Inc. [source] Monitoring of laser micromanipulated optically trapped cells by digital holographic microscopyJOURNAL OF BIOPHOTONICS, Issue 7 2010Björn Kemper Abstract For a precise manipulation of particles and cells with laser light as well as for the understanding and the control of the underlying processes it is important to visualize and quantify the response of the specimens. Thus, we investigated if digital holographic microscopy (DHM) can be used in combination with microfluidics to observe optically trapped living cells in a minimally invasive fashion during laser micromanipulation. The obtained results demonstrate that DHM multi-focus phase contrast provides label-free quantitative monitoring of optical manipulation with a temporal resolution of a few milliseconds. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Flow cytometry with gold nanoparticles and their clusters as scattering contrast agents: FDTD simulation of light,cell interactionJOURNAL OF BIOPHOTONICS, Issue 8-9 2009Stoyan Tanev Abstract The formulation of the finite-difference time-domain (FDTD) approach is presented in the framework of its potential applications to in-vivo flow cytometry based on light scattering. The consideration is focused on comparison of light scattering by a single biological cell alone in controlled refractive-index matching conditions and by cells labeled by gold nanoparticles. The optical schematics including phase contrast (OPCM) microscopy as a prospective modality for in-vivo flow cytometry is also analyzed. The validation of the FDTD approach for the simulation of flow cytometry may open up a new avenue in the development of advanced cytometric techniques based on scattering effects from nanoscale targets. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stability of Lactobacillus reuteri in Different Types of MicrocapsulesJOURNAL OF FOOD SCIENCE, Issue 1 2006Parthiban Muthukumarasamy ABSTRACT: This study was designed to find the most suitable method and wall material for microencapsulation of the probiotic bacterium Lactobacillus reuteri to maintain cell viability during gastric challenge. Five L. reuteri strains were individually encapsulated using alginate, alginate plus starch, K-carrageenan with locust bean gum, or xanthan with gellan by extrusion or phase separation (emulsion). The morphology of the microcapsules was studied using phase contrast and cryo-scanning electron microscopy (cryo-SEM). The resistance of these microcapsules and the viability of contained L. reuteri to simulated gastric juice were studied. The shape and size of the microcapsules produced varied with the preparation method and type of wall material. Extruded microcapsules were larger and more uniformly shaped. Survival of microencapsulated L. reuteri was significantly better than that of planktonic cells and varied with the strain, method of microencapsulation, and wall material used. In general, microencapsulation using alginate and alginate with starch by both extrusion and phase separation were found to provide bacteria significantly greater protection (P < 0.05) against simulated gastric juice. [source] Determination of transmural, endocardial, and epicardial radial strain and strain rate from phase contrast MR velocity dataJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2008Jana G. Delfino PhD Abstract Purpose To develop a method for computing radial strain (,) and strain rate (SR) from phase contrast magnetic resonance (PCMR) myocardial tissue velocity data. Materials and Methods PCMR tissue velocity maps were acquired at basal and mid-short-axis slices in the myocardium in 10 healthy volunteers. An algorithm for computing radial strain and SR from PCMR tissue velocity data was developed. PCMR strain values were compared to values computed independently from contours drawn on cine steady-state free procession (SSFP) images. Peak endocardial and epicardial strain and SR values from PCMR data were compared. Results Excellent agreement was observed between peak strain values computed by PCMR and cine SSFP contours (38.1 ± 5.4% vs. 38.1 ± 6.2%; P = not significant [NS]). The presence of an endocardial-epicardial gradient was demonstrated in both strain and SR: peak endocardial values were larger than peak epicardial values in the basal and mid-short-axis slices (P < 0.05). Conclusion This study presents a method for determining radial strain and SR values from PCMR velocity data. This technique illustrates a difference in strain and SR across the myocardium with peak endocardial values being greater than peak epicardial values. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Morphological and hemodynamic magnetic resonance assessment of early neonatal brain injury in a piglet modelJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2004Berit H. Munkeby MD Abstract Purpose To investigate the utility of functional and morphological magnetic resonance imaging (MRI) to assess the extent of brain injury in a hypoxia-ischemia (HI) piglet model and further to validate that the desired ischemic injury was successfully induced. Materials and Methods MRI was performed at 1.5 T in anesthetized piglets (N = 10, age = 12-36 hours). Relative cerebral blood flow (rCBF), time-to-peak (TTP) contrast, and apparent diffusion coefficient (ADC) were estimated at different time points pre-, during, and post-HI. The effect following bilateral clamping of the carotid arteries was assessed by contrast-enhanced MR angiography (MRA) and phase contrast MR angiography (PCA) (N = 4). Results A linear correlation was observed between relative cerebral perfusion reduction and cerebral ADC during HI (r2 = 0.85, P < 0.05). There was no correlation between rCBF reduction during 30 minutes of HI and cerebral ADC after 30 or 150 minutes of reperfusion/reoxygenation (RR). Conclusion The combination of morphological and functional (perfusion and diffusion) MRI enabled consistent assessment of both the presence and absence of complete occlusion as well as the functional significance of the occlusion. J. Magn. Reson. Imaging 2004;20:8,15. © 2004 Wiley-Liss, Inc. [source] Characterization of combustion-derived individual fine particulates by computer-controlled scanning electron microscopyAICHE JOURNAL, Issue 11 2009Lian Zhang Abstract Particulate matter (PM) emission from the combustion of solid fuels potentially poses a severe threat to the environment. In this article, a novel approach was developed to examine the properties of individual particles in PM. With this method, PM emitted from combustion was first size-segregated. Subsequently, each size was characterized by computer-controlled scanning electron microscopy (CCSEM) for both bulk property and single particle analysis. Combustion of bituminous coal, dried sewage sludge (DSS) and their mixture were conducted at 1200°C in a laboratory-scale drop tube furnace. Three individual sizes smaller than 2.5 ,m were investigated. The results indicate that a prior size-segregation can greatly minimize the particle size contrast and phase contrast on the backscattered images during CCSEM analysis. Consequently, high accuracy can be achieved for quantifying the sub-micron particles and their inherent volatile metals. Regarding the PM properties as attained, concentrations of volatile metals including Na, K, and Zn have a negative relationship with particle size; they are enriched in the smallest particles around 0.11 ,m as studied here. Strong interactions can occur during the cofiring of coal and DSS, leading to the distinct properties of PM emitted from cofiring. The method developed here and results attained from it are helpful for management of the risks relating to PM emission during coal-fired boilers. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Quantitative X-ray projection microscopy: phase-contrast and multi-spectral imagingJOURNAL OF MICROSCOPY, Issue 2 2002S. C. Mayo Summary We outline a new approach to X-ray projection microscopy in a scanning electron microscope (SEM), which exploits phase contrast to boost the quality and information content of images. These developments have been made possible by the combination of a high-brightness field-emission gun (FEG)-based SEM, direct detection CCD technology and new phase retrieval algorithms. Using this approach we have been able to obtain spatial resolution of < 0.2 µm and have demonstrated novel features such as: (i) phase-contrast enhanced visibility of high spatial frequency image features (e.g. edges and boundaries) over a wide energy range; (ii) energy-resolved imaging to simultaneously produce multiple quasi-monochromatic images using broad-band polychromatic illumination; (iii) easy implementation of microtomography; (iv) rapid and robust phase/amplitude-retrieval algorithms to enable new real-time and quantitative modes of microscopic imaging. These algorithms can also be applied successfully to recover object,plane information from intermediate-field images, unlocking the potentially greater contrast and resolution of the intermediate-field regime. Widespread applications are envisaged for fields such as materials science, biological and biomedical research and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to projection microscopy using other sources of radiation, such as visible light and electrons. [source] Multiple-beam X-ray interferometry for phase-contrast microtomographyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2001Ulrich Bonse The first successful operation of an X-ray interferometer under conditions of non-planar three-beam diffraction for phase-contrast X-ray microtomography is reported. Intrinsic phase differences of the reflections used cancel from the three-dimensional phase image of the specimen. With simultaneous hkl and reflections of a synchrotron radiation beam in a side-by-side geometry, the size of the usable field of view is doubled and the investigated specimen volume is increased by a factor of four. As an example, the reconstructed slice of a mouse kidney is shown in phase contrast at 71,keV. Optimized choices of three-beam reflections and matching interferometer geometries useful for applications are presented. [source] Proplatelet formation in heterozygous Bernard-Soulier syndrome type BolzanoJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 3 2009A. BALDUINI Summary.,Background: Although mutations of GPIb, are among the most frequent causes of inherited platelet disorders, the mechanisms for the onset of thrombocytopenia and platelet macrocytosis are still poorly defined. Objective: In this work we analyzed in vitro megakaryocyte differentiation and proplatelet formation in six subjects heterozygous for the Ala156Val mutation in the GPIb, (Bolzano mutation). Methods: Human megakaryocytes were obtained by differentiation of patient cord blood-derived CD34+ cells and peripheral blood-derived CD45+ cells. Proplatelet formation was evaluated by phase contrast and fluorescence microscopy. Results: Megakaryocyte differentiation from both cord blood (one patient) and peripheral blood (five patients) was comparable to controls. However, proplatelet formation was reduced by about 50% with respect to controls. An identical defect of proplatelet formation was observed when megakaryocytes were plated on fibrinogen, von Willebrand factor or grown in suspension. Morphological evaluation of proplatelet formation revealed an increased size of proplatelet tips, which was consistent with the increased diameters of patients' blood platelets. Moreover, ,-tubulin distribution within proplatelets was severely deranged. Conclusions: Megakaryocytes from patients carrying a Bolzano allele of GPIb, display both quantitative and qualitative abnormalities of proplatelet formation in vitro. These results suggest that a defect of platelet formation contributes to macrothrombocytopenia associated to the Bolzano mutation, and indicate a key role for GPIb, in proplatelet formation. [source] Phase-contrast velocimetry with hyperpolarized 3He for in vitro and in vivo characterization of airflowMAGNETIC RESONANCE IN MEDICINE, Issue 6 2006Ludovic de Rochefort Abstract This paper describes a technique that combines radial MRI and phase contrast (PC) to map the velocities of hyperpolarized gases (3He) in respiratory airways. The method was evaluated on well known geometries (straight and U-shaped pipes) before it was applied in vivo. Dynamic 2D maps of the three velocity components were obtained from a 10-mm slice with an in-plane spatial resolution of 1.6 mm within 1 s. Integration of the in vitro through-plane velocity over the slice matched the input flow within a relative precision of 6.4%. As expected for the given Reynolds number, a parabolic velocity profile was obtained in the straight pipe. In the U-shaped pipe the three velocity components were measured and compared to a fluid-dynamics simulation so the precision was evaluated as fine as 0.025 m s,1. The technique also demonstrated its ability to visualize vortices and localize characteristic points, such as the maximum velocity and vortex-center positions. Finally, in vivo feasibility was demonstrated in the human trachea during inhalation. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Imaging of cochlear tissue with a grating interferometer and hard X-raysMICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2009Claus-Peter Richter Abstract This article addresses an important current development in medical and biological imaging: the possibility of imaging soft tissue at resolutions in the micron range using hard X-rays. Challenging environments, including the cochlea, require the imaging of soft tissue structure surrounded by bone. We demonstrate that cochlear soft tissue structures can be imaged with hard X-ray phase contrast. Furthermore, we show that only a thin slice of the tissue is required to introduce a large phase shift. It is likely that the phase contrast image of the soft tissue structures is sufficient to image the structures even if surrounded by bone. For the present set of experiments, structures with low-absorption contrast have been visualized using in-line phase contrast imaging and a grating interferometer. The experiments have been performed at the Advanced Photon Source at Argonne National Laboratories, a third generation source of synchrotron radiation. The source provides highly coherent X-ray radiation with high-photon flux (>1012 photons/s) at high-photon energies (5,70 keV). Radiographic and light microscopy images of the gerbil cochlear slice samples were compared. It has been determined that a 20-,m thick tissue slice induces a phase shift between 1/3, and 2/3,. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] Autofocusing in computer microscopy: Selecting the optimal focus algorithmMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2004Yu Sun Abstract Autofocusing is a fundamental technology for automated biological and biomedical analyses and is indispensable for routine use of microscopes on a large scale. This article presents a comprehensive comparison study of 18 focus algorithms in which a total of 139,000 microscope images were analyzed. Six samples were used with three observation methods (brightfield, phase contrast, and differential interference contrast (DIC)) under two magnifications (100× and 400×). A ranking methodology is proposed, based on which the 18 focus algorithms are ranked. Image preprocessing was also conducted to extensively reveal the performance and robustness of the focus algorithms. The presented guidelines allow for the selection of the optimal focus algorithm for different microscopy applications. Microsc. Res. Tech. 65:139,149, 2004. © 2004 Wiley-Liss, Inc. [source] Vascular Mimicry of Granulosa Cells: a New Concept of Corpeus Luteum Development?ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005R. M. Hirschberg So far, it was generally accepted that newly formed blood vessels are exclusively comprised of endothelial cells, and complemented by pericyte and myocyte recruitment during vessel maturation. Accordingly, participation of non-endothelial cells in the formation of blood vessels has rarely been suggested. Recently, evidence supporting the existence of tumour vessels lined by non-endothelial cells has emerged. Consequently, the concept of the inherent capacity of non-endothelial cells to behave like endothelial cells has been discussed for tumours, and this pathomechanism has been termed vascular mimicry. The corpus luteum is one of the most intensely vascularized tissues, and angiogenesis in the corpus luteum is more effective than in highly malignant tumours. Our results indicate active involvement of granulosa cells in luteal angiogenesis, and the aim of this study was to shed more light on this exciting prospect. The study was based on cultured granulosa cells isolated from the bovine ovary in different stages of follicle maturation. Morphology of angiogenic granulosa cells was studied by phase contrast, transmission electron and scanning electron microscopy. Expression of angiogenesis-regulating factors and their receptors was demonstrated by polymerase chain reaction (RT-PCR). Cultured granulosa cells underwent changes reminiscent of endothelial angiogenesis, i.e., migration, proliferation, differentiation and three-dimensional organization, and expressed angiogenesis-regulating factors and their receptors. Our results suggest a tight regulatory and structural association of endothelial and granulosa cells in luteal angiogenesis, suggesting physiological vascular mimicry in the ovary. [source] Soil-borne wheat mosaic virus inclusion bodies: structural, compositional and staining propertiesANNALS OF APPLIED BIOLOGY, Issue 2 2003L J LITTLEFIELD Summary Anatomy and cytochemistry of inclusion bodies induced by Soil-borne wheat mosaic virus infection were studied in roots and leaves to learn more about the nature of inclusions and their roles in pathogenesis. Acid Fuchsin, Giemsa stain, Toluidine Blue and Trypan Blue stains facilitated visualization of inclusion bodies. Combined, simultaneous staining with Acid Fuchsin and Toluidine Blue clearly differentiated inclusion bodies from host nuclei. The overall anatomy, composition and structure of virus inclusions in leaves and roots were generally similar, as shown by phase contrast, differential interference contrast, epifluorescence, laser scanning confocal and transmission electron microscopy. Both were often closely associated with host nuclei; both were comprised of intertwined masses of tubular material, presumably endoplasmic reticulum, and in which varied numbers and sizes of vacuolar cavities occurred. Leaf inclusions, however, were typically larger and more vacuolate than those in roots. Lipids were found to be significant constituents of both the tubular and vacuolar components of inclusions, indicated by positive staining with Nile Red and Sudan Black. Inclusion bodies in both leaves and roots lost their structural and compositional integrity, eventually becoming disorganized and devoid of clearly identifiable components as host tissue aged and symptom expression advanced. Significant results of this study include the first published examination of virus inclusion bodies in root tissue, the degree of structural detail of inclusion body anatomy revealed by laser scanning confocal microscopy and the presence of an extensive lipid component in virus inclusion bodies. [source] Assessment of physiological conditions in E. coli fermentations by epifluorescent microscopy and image analysisBIOTECHNOLOGY PROGRESS, Issue 3 2009Sónia Carneiro Abstract The development of monitoring methods for assessing the physiological state of microorganisms during recombinant fermentation processes has been encouraged by the need to evaluate the influence of processing conditions in recombinant protein production. In this work, a technique based on microscopy and image analysis was developed that allows the simultaneous quantification of parameters associated with viability and fluorescent protein production in recombinant Escherichia coli fermentations. Images obtained from light microscopy with phase contrast are used to assess the total number of cells in a given sample and, from epifluorescence microscopy, both protein producing and injured cells are evaluated using two different fluorochromes: propidium iodide and enhanced yellow fluorescent protein. This technique revealed the existence of different cell populations in the recombinant E. coli fermentation broth that were evaluated along four batch fermentations, complementing information obtained with standard techniques to study the effects of the temperature and induction time in recombinant protein production processes. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Simultaneous IR Material Recognition and Conductivity Mapping by Nanoscale Near-Field Microscopy,ADVANCED MATERIALS, Issue 17 2007J. Huber IR scattering-type near-field microscopy is applied to simultaneously map material composition and conduction properties in cross-sectional samples of industrial bipolar and metal-oxide- semiconductor devices with nanoscale spatial resolution. Within a single mid-IR image, all relevant materials such as metals, Si, Si3N4, and oxides can be identified by material-specific amplitude and phase contrasts. [source] | ||||||||||||||||||||||||||||