Slit Scanning Research Articles

Excimer laser photorefractive keratectomy for high myopia

One hundred and thirty-three eyes of 103 patients had photorefractive keratectomy with a slit scan mode excimer laser for myopia ranging from −6.00 to −22.00 diopters (D). The epithelium was removed with 20% ethanol, and the ablation was done with a tapered profile surrounding the optical zone. Patients were divided into two groups based on preoperative myopia: Group A, −6.00 D to −12.00 D (88 eyes); Group B, −12.50 D to −22.00 D (45 eyes). In Group A, mean preoperative refraction was −9.59 ± 1.79 D. Mean postoperative refraction was −0.29 ± 1.47 D at one month, −0.85 ± 1.68 D at three months, −1.17 ± 2.04 D at six months, and −0.56 ± 0.74 D at one year. Anterior stromal haze was greatest at the end of the first month; it diminished thereafter. This haze did not reduce the best corrected visual acuity in any eye in Group A. Mean preoperative refraction in Group B was −14.69 ± 5.27 D. Mean postoperative refraction was −1.34 ± 2.02 D at one month, −0.76 ± 2.08 D at three months, −3.88 ± 2.32 D at six months, and −5.50 ± 5.00 D at one year. Three eyes in Group B lost one or two lines of best corrected visual acuity as a result of severe stromal haze and epithelial scarring. Group A's results were similar to those obtained in eyes with low myopia. In Group B, although a percentage of eyes obtained fairly good results, the lower degree of predictability and large variation in the results suggest that using this technique is unadvisable in eyes with extremely high myopia except in selected cases.

Early Results on Phototherapeutic Keratectomy with Scanning Slit Technique

Early Results on Phototherapeutic Keratectomy with Scanning Slit Technique

Scanning Slit Confocal Microscopic Observation of Cell Morphology and Movement within the Normal Human Anterior Cornea

Noninvasive in vivo observations of the anterior human cornea were performed to study cell structure and dynamics. Cellular elements were identified by their location, morphology, and pattern of movement. The hypothesis that cells in the epithelial layer of the normal cornea migrate centripetally was tested. Using a scanning slit confocal microscope with a new 0.75-numeric aperture contact objective, individual cells of normal human corneas were observed over time, quantifying the velocity and direction of cellular movement within the basal epithelial layer. Basal epithelial cells, wing cells, the basal epithelial nerve plexus, and the subepithelial nerve plexus were identified readily. Centripetal motion was observed for three corneal cell types: basal epithelial cells, basal epithelial nerves, and unidentified cellular elements (possibly Langerhans cells). The unidentified cellular elements moved along the length of the basal epithelial nerves. The basal epithelial nerve plexus maintained a roughly stable topology as it slid centripetally. New nerve material appeared at the site of entry of the nerve into the epithelium. No growth cones were present at the distal termini of the growing epithelial nerves. In the midperiphery of the normal human cornea, basal epithelial cells and nerves slide centripetally, probably in concert. Unidentified cellular elements used the basal epithelial nerve plexus as a pathway for intraepithelial movement. Observations in this study suggest that neurite growth occurred by the addition of new membrane material along the length of the axon rather than at a distal growth cone.

Early Results on Phototherapeutic Keratectomy with Scanning Slit Technique

Early Results on Phototherapeutic Keratectomy with Scanning Slit Technique

Real-time scanning slit confocal microscopy of the in vivohuman cornea

We describe a new, nonapplanating, real-time scanning slit confocal microscope that produces unique real-time video images of the in vivo human cornea. This new real-time slit scanning confocal microscope produces en face, single-video-frame images (2-µm sections) with high contrast through the full thickness (500 µm) of the normal cornea. No frame averaging or digital image enhancement is required. The images of superficial epithelial cells, wing cells, basal epithelial cells, corneal innervation, nuclei of stromal keratocytes, and the cell bodies of the stromal keratocytes in the posterior stromal region demonstrate the unique real-time imaging characteristics. The microscope is equipped with waterimmersion microscope objectives of high numerical aperture. The microscope objective does not flatten or distort the cornea; a polymer gel is used to couple the microscope objective optically to the cornea.

Identification and cytogenetic analysis of an abnormal pig chromosome for flow cytometry and sorting.

For cytogenetics of pig (Sus scrofa domestica) and the influence of chromosome aberrations on pig production, high interest exists in flow sorted chromosomes for gene mapping, to establish DNA-libraries, or to produce DNA-probes. Flow karyotyping and sorting as well as slit scan flow analysis of metaphase chromosomes of an abnormal cell type carrying a translocation marker chromosome 6/15 are described. Flow sorting of the largest chromosomes of these cells was performed. After sorting the chromosomes still had a well preserved morphology and were identified microscopically by G-banding. The quality of the band pattern of the sorted chromosomes was compatible to that of isolated chromosomes not subjected to flow cytometry. The sorted fraction showed an enrichment of chromosome 6/15 and chromosome 1 which have quantitatively about the same integrated fluorescence intensity. Slit scan flow analysis was performed to discriminate these two chromosomes. Metacentric and submetacentric chromosomes were analyzed according to their bimodal slit scan profiles. Profiles of the largest chromosomes were distinguished by their different centromeric indices. Two groups were interpreted as the normal chromosome 1 and the translocation chromosome 6/15.

Subsurface Microscopical visualization of brain tissue in vivo: Present, problems and prospects

The location of the brain within the cranium has prevented in vivo studies with microscopical resolution for a long time. Cranial window techniques provide microscopical access to the brain surface, but subsurface structures cannot be visualized with conventional microscopy. Confocal microscopy with its increased depth of penetration and optical sectioning capabilities is ideally suited for the investigation of thick biological specimens. Due to the scanning process, however, temporal resolution is limited, a significant disadvantage in the in vivo setting. In this article we demonstrate that confocal laser scanning microscopy can be utilized to study brain cortex microvascular morphology, capillary hemodynamics, leukocyte behaviour and intracellular ion concentrations in anesthetized rats through a closed cranial window. Three different confocal microscopes are compared: a Biorad MRC-600 with multiline Kr/Ar-Laser (488/568/647 nm), a Noran Odyssey acousto-optic scanning microscope with multiline Ar-Laser (458/488/514/529 nm) and a Biorad Viewscan DVC-250 slit scanning microscope with Ar-Laser (488/514 nm). With all microscopes a Zeiss × 40 water immersion objective, n.a. 0.75 is used. A Laser-Doppler flowmeter continuously measures regional cerebral blood flow in the area of microscopical investigation. As fluorescent dyes we used: fluorescein sodium as blood plasma marker (given I.V.); rhodamine 6G to label leukocytes (given I.V.); and the AM-esters of BCECF (pH-sensitive), Fluo-3 and Calcium-Green (both calcium-sensitive) as intracellular ion-concentration markers (loaded via superfusion over the cranial window). With this setup, we are able to study the flow dynamics in the capillary network of the cortex (erythrocyte flow velocities and flux rates), the behaviour of leukocytes in capillaries and postcapillary veins (plugging of capillaries, adhesion to the endothelium, extravasation into the parenchyma), and intracellular changes of [H +] and [Ca 2+] under physiological and pathophysiological conditions (cerebral ischemia and meningitis). The comparison between the conventional CLSM (Biorad 600) and the real time CLSMs revealed that the increase in temporal resolution afforded by the real time instruments is offset by a reduction in spatial resolution and, most importantly, in the signal to noise ratio, resulting in a lower depth of penetration into the tissue and necessitating frame averaging.

Moiré topography by slit beam scanning

A new method of moiré topography is suggested in which a slit beam is used in a scanning mode to generate moiré fringes. One remarkable feature of this method is that, as opposed to existing shadow and projection types, height differences between two consecutive fringes become constant so that absolute fringe orders need not be identified. This advantage makes it possible to measure three-dimensional surface profiles in an automatic manner simply by using a computer-aided image-processing technique. In addition this method can be easily implemented in a conventional coordinate measuring machine with a minimum addition of optical hardware.

New flow cytometric capabilities at the national flow cytometry resource

The authors provide a brief review of flow cytometry and a broad view of new flow cytometry technologies. A brief introduction to flow cytometry and cell sorting is provided along with a summary of current commercial capabilities. New developments designed to overcome current limitations are described in terms of capabilities and a characterization of their performance. New capabilities include Fourier transform flow cytometry, phase sensitive detection, digital data acquisition, data clustering algorithms, high speed sorting, and slit scanning.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Automatic specklegram fringe analysis by using symmetry evaluation of the Θ-scanning function

New approaches are applied to overcome the difficulty of accurate angle measurements in specklegram information processing by introducing a prism rotator for compensation and by using symmetry evaluation. Together with slit scanning and the fast Fourier transform procedure, speckle random noise has been effectively suppressed, and accurate measurements of Theta and s are achieved. The method we present makes it possible to process the specklegram information automatically. The experimental setup is described in detail. The principles and experimental curves are given.

Analysis of an abnormal pig chromosome by cytogenetics flow cytometry and slit scanning

Analysis of an abnormal pig chromosome by cytogenetics flow cytometry and slit scanning

Slit scan illumination for dynamic focusing

This mode describes a modification of the spot scan mode1 in which areas on a photographic plate are exposed one after the other using small illuminating spots. The spot scan mode in transmission electron microscopes (TEM) reduces specimen damage and specimen drift. In addition to this it allows dynamic focussing at high tilt angles of the specimen.High-resolution, 3-D specimen reconstruction and reflection electron imaging using specimen tilt angles of up to 90° require dynamic focussing rectangular to the tilt axis of the goniometer for imaging of off-axis specimen areas. A slit-type illumination of the specimen parallel to the goniometer tilt axis may provide a better solution for such types of problems.

Slit Scan Flow Cytometry Of Isolated Chromosomes Following Fluorescence Hybridization: An Approach Of Online Screening For Specific Chromosomes And Chromosome Translocations

The recently developed methods of non radioactive in situ hybridization of chromosomes offer new aspects for chromosome analysis. Fluorescent labelling of hybridized chromosomes or chromosomal subregions allows to facilitate considerably the detection of specific chromosomal abnormalities. For many biomedical applications (e.g. biological dosimetry in the low dose range), a fast scoring for aberrations (e.g. dicentrics or translocations) in required. Here, we present an approach depending on fluorescence in situ hybridization of isolated suspension chromosomes that indicates the feasibility of a rapid screening for specific chromosomes or translocations by slit scan flow cytometry. Chromosomes of a Chinese hamster x human hybrid cell line were hybridized in suspension with biotinylated human genomic DNA. This DNA was decorated with FITC by a double antibody system against biotin. For flow cytometry the chromosomes were stabilized with ethanol and counterstained with DAPI or propidium iodide (PI). An experimental data set of several hundred double profiles was obtained by two parameter slit scan flow cytometry and evaluated automatically. The evaluation algorithm developed allowed a classification of chromosomes according to the number of centromeres and their chromosomal positions in less than 1 msec per individual profile. Approximately 20% of the measured DAPI profiles showed a bimodal distribution with a significant centromeric dip indicating a "normal" chromosomal morphology and a correct alignment in the flow system. In many cases, profiles of a "normal" bimodal fluorescence distribution of the DNA stain (DAPI, PI) were correlated with a "normal" FITC profile. Due to their centromeric indices these profiles agreed well to the expected human chromosomes of the cell line. In some cases of "normal" DAPI (PI) profiles, "aberrant" FITC profiles were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aniosmotic media on the volume of the T-lymphocyte nucleus

Time-resolved measurements of the nuclear volume response of human peripheral T-lymphocytes, under aniosmotic conditions, are presented. In the experiments slit scanning FlowCytometry methods were used. We propose an extension to the standard solid viscoelastic model to interpret the observed dynamical behavior of the nucleus. It is shown that experimental and theoretical evidence indicates a passive nuclear response merely induced by a mechanical link (i.e., the cytoskeleton) between the cell membrane and the nuclear envelope. Implications of this work to the field of cellular mechanics and cytoskeletal rheology are surveyed.

A slit laser scanning moire method and a simple method for distinguishing between depression and elevation

Three-dimensional shape measurement is a very important subject for the shape recognition of three-dimensional objects. Moire topography is a very useful method for three-dimensional shape measurement because the moire image is formed as a contour line image and it includes three-dimensional shape information. However, in practical use, moire topography has several problems, such as the formation of high-contrast and uniform moire images in an illuminated room, a method for distinguishing between depression and elevation, and a simple method for extracting three-dimensional shape data by image processing. This paper presents a new moire formation method using slit laser scanning and the image accumulation properties of a TV camera, a simple method for distinguishing between depression and elevation, and an automatic image processing measurement system. This new moire method enables the formation of a moire image in an illuminated room, which is a realistic industrial environment. The proposed method for distinguishing between depression and elevation is based on a binary image distinguished by whether the gradient of the measuring surface is positive or negative. This binary image is formed by processing the video signal from a deformed grating image at the same time as the moire image is formed.

Slit scanning of Saccharomyces cerevisiae cells: quantification of asymmetric cell division and cell cycle progression in asynchronous culture.

Slit scanning flow cytometry has been applied to the analysis of the cell cycle and cell-cycle-dependent events in Saccharomyces cerevisiae, yielding information on the low-resolution spatial distribution of cellular components in single cells of unperturbed cell populations. Because this process is rapid, large numbers of cells can be analyzed to give distributions of parameters in a given population. To study asymmetric cell division and cell cycle progression, forward-angle light scattering (FALS) signals together with fluorescence signals from acriflavine-stained nuclei have been measured in cells from exponentially growing yeast populations. An algorithm has been developed that assigns the position of the bud neck in the FALS signals so that both FALS and DNA signals can be analyzed in terms of the contributions from the mother cell and the cell bud. The data indicate that mother cell FALS, on average, remains constant while FALS due to the cell bud increases as a cell progresses through the cell cycle. By identifying mitotic cells and measuring their properties, we have found that the coefficient of variation for the distribution of FALS is smallest within the dividing cell population and largest within the newborn cell population, in accordance with the critical size control mechanism of yeast cell growth. The use of this experimental approach to provide data for statistical population models is discussed.

Confocal Scanning Slit Microscopy using a Linear Detector Array

Confocal microscopy has been shown to produce improved lateral and axial image resolution compared with conventional microscopy. Image degradation due to scattering is reduced since only those portions of the specimen in the focal plane of the objective will contribute to image formation at the light detector. Previous work has shown that slit apertures can be used instead of pinholes to achieve the advantages of confocal microscopy with increased illumination and deceased scan line artifact. Slit scanning microscopes are also simpler in design than pinhole scanners but their aperture forms an asymmetric point spread function. We have developed a confocal scanning microscope utilizing a slit aperture and a linear charge coupled device (CCD) as a photodetector. We characterize its resolution for imaging a thick luminescent specimen as a function of scanning axis, wavelength, and tissue depth.A schematic of the new confocal microscope is shown in figure 1. The illumination source is a 150 watt incandescent bulb.

Real-time multiprocessing of slit scan chromosome profiles

The multiprocessor NERV and its application to slit scan flow cytometry is described. Up to 320 processors and 640 MBytes of RAM may be used in one VME crate, providing a computing power of ≤ 1300 MIPS. The multiprocessor is controlled by a host computer that provides a friendly user interface and comfortable program development tools. All hardware and software has been tested on a prototype NERV system with 5 processors. For a real-time classification/detection of normal and aberrant chromosomes, the centromeric index or the number of centromeres are computed or specifically labeled DNA sequences are detected. The program is partitioned into 60 tasks that can be executed concurrently. A total analysis time of < 600 μs including system overhead will be achieved according to timing measurements which have been done for all individual tasks.

Diffraction-limited astronomical infrared imaging through the turbulent atmosphere

The authors have applied speckle interferometric techniques to 1D near-infrared ( lambda =2.2 mu m; K band) astronomical data to obtain diffraction-limited images. They have investigated a number of phase retrieval techniques applied to slit scanning data and they find that bispectrum analysis provides the best results. They also show preliminary results obtained with 1D projections from specklegrams obtained with the NOAO InSb 58*62 array.

Integration Errors in the Quantitative Evaluation of Flat Bed Separations

Abstract The paper discusses sources of errors which affect the accuracy of optical densitometry for the quantitative evaluation of TL chromatograms and flat bed electropherograms. Both 1D and 2D separations are considered. Relevant error sources fall into two classes. One which is deterministic in nature and one which has stochastic character. The main source of deterministic errors is the non-linear relation between densitometric response and concentration distribution. Linearizing transforms of the reponse signal are available which significantly reduce the magnitude of the error. They are most effective when “point” scanning is used but much less so with slit scanning. Stochastic sources produce noise which affects the measured value of the signal amplitude. Most important is generally the “optical” noise of the blank medium. In most cases it is this factor, which ultimately determines sensitivity and accuracy of the method. Efforts to reduce optical noise are, therefore, an important design feature for high performance instrument. Most effective in this regard is two wave lengths scanning. The technique is, however, applicable only if the response characteristic of the medium is spectrally flat over a range which is significantly wider than the spectral absorbance characteristic of the separate.