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Results for “MICROSCOPY, PHASE”

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At least 37 records · Page 2Linked to original sources
PubMed2004

Lorentz phase microscopy of magnetic materials.

We propose a method of Lorentz phase microscopy for in situ studies and imaging magnetic materials in transmission electron microscopy (TEM) based on the solution of the magnetic transport-of-intensity equation. We also describe the appropriate way of solving this equation that may be useful for understanding and practical use of non-holographic methods for phase retrieval in electron microscopy, especially in imaging magnetic materials. The method is simple, since it is primarily based on classical Fresnel imaging. On the other hand, it is quantitative and can be applied in any TEM without changing the basic hardware. Therefore, it may well find important practical applications in ultramicroscopy and modern magnetic materials research.

Journal Article↗
PubMed1995

Recent developments in electron holography for phase microscopy.

This paper reports on the recent remarkable progress made in electron phase microscopy, especially due to the development of both a "coherent" field-emission electron beam and the related image processing techniques. With these techniques, the phase distribution of an electron beam transmitted through a specimen can now be measured with a precision of within 1/100 of the electron wavelength to observe the thickness distribution of a uniform specimen at the atomic level, the magnetic domain structures in a ferromagnetic thin film, and individual vortices in a superconducting thin film. Vortices in superconducting thin films have become dynamically observable by Lorentz microscopy.

Holography↗
PubMed2004

Quantitative phase microscopy: a new tool for measurement of cell culture growth and confluency in situ.

Quantitative phase microscopy (QPM) is a recently developed computational approach that provides quantitative phase measurements of specimen images obtained under bright-field conditions without phase- or interference-contrast optics. To perform QPM, an in-focus bright-field image is acquired, together with one positive and one negative de-focus image. An algorithm is then applied to produce a specimen phase map. In this investigation we demonstrate that manipulation of the phase map intensity histogram using novel, non-subjective thresholding and segmentation methods provides enhanced delineation of cells in culture. QPM was utilised to measure the growth behaviour of cultured airway smooth muscle cells over a 92-h period. There was a high degree of correlation between parallel QPM-derived confluency measurements and haemocytometry-derived counts of airway smooth muscle cells over this time period. Using QPM, translucent cells can be visualised with improved cell boundary definition allowing precise and reproducible measurements of cell culture confluency. Quantitative phase imaging provides a rapid, optically simple and non-destructive approach for measurement of cellular morphology. Further development of the QPM-based analysis methodology has the potential to provide even more refined measures of cellular growth.

Algorithms↗
PubMedDate not supplied

Erythrocyte structure and dynamics quantified by Hilbert phase microscopy.

We present a new quantitative method for investigating red blood cell morphology and dynamics. The instrument integrates quantitative phase microscopy with an inverted microscope, which makes it particularly suitable for the noninvasive assessment of live erythrocytes. In particular, we demonstrate the ability of this approach to quantify noninvasively cell volume and dynamic morphology. The subnanometer path-length sensitivity at the millisecond time scales is exemplified by measuring the hemoglobin flow out of the cell during hemolysis.

Cell Size↗
PubMed2005

Spectral-domain phase microscopy.

Broadband interferometry is an attractive technique for the detection of cellular motions because it provides depth-resolved phase information via coherence gating. We present a phase-sensitive technique called spectral-domain phase microscopy (SDPM). SDPM is a functional extension of spectral-domain optical coherence tomography that allows for the detection of nanometer-scale motions in living cells. The sensitivity of the technique is demonstrated, and its calibration is verified. A shot-noise limit to the displacement sensitivity of this technique is derived. Measurement of cellular dynamics was performed on spontaneously beating cardiomyocytes isolated from chick embryos.

Animals↗
PubMed1986

[Morphologic study of microscopic hematuria using phase contrast microscopy].

Phase contrast microscopic examination of the urine has been recently reported to be valuable in predicting whether hematuria is due to glomerulonephritis or not. Phase contrast microscopy can differentiate glomerular red cells from nonglomerular ones since the former varies in size and shape with distortion, whereas the latter is uniform in size and shape. Urinalysis of 217 cases of microscopic hematuria was performed at our Hospital. Red blood cells were classified into two types, glomerular and nonglomerular type. Ninety percent of the cases of bladder leukoplakia as well as all cases of glomerulonephritis had glomerular type red blood cells.

Diagnosis, Differential↗
PubMed1975

Use of peroxidatic-enzyme staining to enhance resolution of cultured mammalian cells under phase microscopy.

Staining of glutaraldehyde-fixed mammalian cells with peroxidatic enzymes (horseradish peroxidase or horse heart cytochrome c) greatly enhances resolution of their structure under phase microscopy. The topography of cell processes and regions of intercellular contact and overlapping is resolved precisely, even in dense cultures mounted in media which ordinarily do not permit clear demonstration of these areas. The technique is therefore a useful aid to the study of cultured cells with phase optics. Labeling depends on introducing free aldehydes into cells through the use of bifunctional fixatives such as glutaraldehyde. Acetone or formaldehyde fixation prevents staining, and labeling intensity is greatly diminished by pretreatment with spermine, a polyamine that reacts with glutaraldehyde. Electron microscopy reveals that peroxidase tags membranes preferentially; some areas are labeled smoothly, others in a punctate manner. Ribosomes are sharply contrasted, but nuclei remain unstained. Cytochrome c labels condensed nuclear chromatin intensely, and also stains ribosomes and portions of the cytoplasmic ground substance; membranes are mostly unmarked.

Animals↗
PubMed2005

Coherent phase microscopy in cell biology: visualization of metabolic states.

Visualization of functional properties of individual cells and intracellular organelles still remains an experimental challenge in cell biology. The coherent phase microscopy (CPM) provides a convenient and non-invasive tool for imaging cells and intracellular organelles. In this work, we report results of statistical analysis of CPM images of cyanobacterial cells (Synechocystis sp. PCC 6803) and spores (Bacillus licheniformis). It has been shown that CPM images of cyanobacterial cells and spores are sensitive to variations of their metabolic states. We found a correlation between one of optical parameters of the CPM image ('phase thicknesses' Deltah) and cell energization. It was demonstrated that the phase thickness Deltah decreased after cell treatment with the uncoupler CCCP or inhibitors of electron transport (KCN or DCMU). Statistical analysis of distributions of parameter Deltah and cell diameter d demonstrated that a decrease in the phase thickness Deltah could not be attributed entirely to a decrease in geometrical sizes of cells. This finding demonstrates that the CPM technique may be a convenient tool for fast and non-invasive diagnosis of metabolic states of individual cells and intracellular organelles.

Bacillus↗
PubMed2006

Single cell volume measurement by quantitative phase microscopy (QPM): a case study of erythrocyte morphology.

The measurement of the volume of intact, viable cells presents challenging problems in many areas of experimental and diagnostic science involved in the evaluation of cellular morphology, growth and function. This investigation details the implementation of a recently developed quantitative phase microscopy (QPM) method to measure the volume of erythrocytes under a range of osmotic conditions. QPM is a computational approach which utilizes simple bright field optics to generate cell phase maps which, together with knowledge of the cellular refractive index, may be used to measure cellular volume. Rat erythrocytes incubated in imidazole-buffered solutions (22 degrees C) of graded tonicity were analysed using QPM (n=10 cells/group, x63, 0.8 NA objective). Erythrocyte refractive index (1.367) was measured using a combination of phase and morphological data obtained from cells adopting spherical geometry under hypotonic conditions. Phase-computed volume increased with decreasing solution osmolality: 42.8 +/- 2.4, 48.7 +/- 2.3, 62.6 +/- 2.3, 90.8 +/- 7.7 microm3 in solutions of 540, 400, 240, and 170 mosmol/kg respectively. These volume changes were associated with crenated, bi-concave and spherical morphological states associated with increasing tonicity. This investigation demonstrates that QPM is a valid, simple and non-destructive approach for measuring cellular phase properties and volume. QPM cell volume analysis represents a significant advance in viable cell experimental capability and provides for acquisition of 'real-time' data - an option not previously available using other approaches.

Animals↗