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At least 1,153 records · Page 64Linked to original sources
PubMed2000

Preliminary evaluation of dual wavelength phased array imaging on neonatal brain function.

Imaging of human tissue using noninvasive techniques has been of great interest in biomedical fields. Optical imaging has attracted a lot of attention because of its portability and economy. The possibility that a highly portable, fast, safe, and affordable imaging system which could obtain interpretable images of brain function for pre- and full-term neonates in a few seconds, has been explored in this article. We have used a sensitive optical topography system, termed phased array, in which a pair of equal-amplitude and antiphase light sources are applied to generate a sharp amplitude null and phase transition plane. This two-wavelength (750 and 830 nm), frequency encoded (50 and 52 MHz) phased array imaging system can indicate the blood concentration and oxygenation changes in blood model studies and during parietal brain activation in neonates. Significant functional responses, particularly to parietal stimulation in normal and pathological states of neonatal brain, have been revealed in our study. The preliminary clinical results are presented in this article.

Blood Flow Velocity↗
PubMed1999

Optical coherence tomography images of spontaneous macular hole closure.

PURPOSE: To investigate optical coherence tomography images of spontaneous macular hole closure. METHOD: Case report. In a 60-year-old woman with full-thickness macular hole, posterior vitreous detachment, and previous branch retinal vein occlusion, we observed the entire course of spontaneous macular hole closure by use of optical coherence tomography. RESULTS: Spontaneous macular hole closure began as the inward protrusion of the tissue around the margin of the macular hole. The protruding tissue then connected to bridge the macular hole, which mimicked a foveal retinal detachment. The bridged tissue gradually thickened, and the foveal detachment and perifoveal cysts resolved. The fovea eventually regained its normal configuration. CONCLUSIONS: The bridging of the protruding retinal tissue over the macular hole plays a key role in spontaneous macular hole closure.

Cysts↗
PubMed2005

Fluorescence imaging of the activity of glucose oxidase using a hydrogen-peroxide-sensitive europium probe.

A method for optical imaging of the activity of glucose oxidase (GOx) using a fluorescent europium(III) tetracycline probe for hydrogen peroxide is presented. A decay time in the microsecond range and the large Stokes shift of 210 nm of the probe facilitate intensity-based, time-resolved, and decay-time-based imaging of glucose oxidase. Four methods for imaging the activity of GOx were compared, and rapid lifetime determination imaging was found to be the best in giving a linear range from 0.32 to 2.7 m Unit/mL. The detection limit is 0.32 m Unit/mL (1.7 ng mL(-1)) which is similar to that of the time-resolved (gated) imaging using a microtiterplate reader. Fluorescent imaging of the activity of GOx is considered to be a useful tool for GOx-based immunoassays with potential for high-throughput screening, immobilization studies, and biosensor array technologies.

Biosensing Techniques↗
PubMed2005

Relationship between microscanned image quality and fill factor of detectors.

Microscanning is an important technique in high-resolution electro-optical imaging. It can increase the resolution and improve the performance of imaging systems. For optimum design of a staring imaging system with microscanning modes it is necessary to choose the optimum microscanning mode according to the fill factor of the detector. Hence it is important to study the effect of the fill factor on the microscanning image quality. With some assumptions, we introduce the sampling-averaging modulation transfer function of a detector array at the spatial Nyquist frequency with which to study quantitatively the improvement in image quality of various microscanning modes for selected fill factors (1, 2/3, and 1/2). Analytical results show that the amount of improvement is closely associated with the fill factor. Finally, typical sampling imaging of focal plane arrays with these fill factors are simulated. Experimental results qualitatively describe the effect of the fill factor on the microscanning image and show good agreement with theoretical analysis.

Journal Article↗
PubMedDate not supplied

Grayscale and proportion-corrected optical coherence tomography images.

BACKGROUND AND OBJECTIVE: The commercially available optical coherence tomography (OCT) scanner displays images in a pre-set window regardless of the projected scan length on the retinal surface. The aim of this study was to demonstrate the true dimensions of proportion-corrected OCT images and the additional information present in grayscale images. MATERIALS AND METHODS: OCT raw data were exported to an IBM-compatible PC and processed to show grayscale and proportion-corrected images using an automated software of our own design. RESULTS: Eyes with cystoid macular edema and retinal pigment detachment were analyzed. Grayscale images showed a finer gradation of signal reflectance. Scan lengths of 2, 4, 6, and 8 mm on the retinal surface showed different qualitative appearances using proportion-corrected software from the printed or on-screen images. CONCLUSIONS: Grayscale OCT images can be used to demonstrate additional information not present in false-color images. The disparity between the standard OCT image format and proportion-corrected images emphasizes the need for quantitative rather than qualitative evaluation of retinal dimensions and internal reflectance.

Algorithms↗
PubMedDate not supplied

MRI monitoring of laser ablation using optical flow.

The optical flow method is used for visualizing and quantifying the dynamics of tissue changes observed by MRI during thermal ablations. An approach was implemented for parallel two-dimensional optical flow calculations including the replacement of spurious velocities. Velocity magnitude results were found to be accurate in low-noise cases in tests using series of synthetic images. Optical flow results are presented from thermal ablation experiments utilizing a homogeneous polyacrylamide gel phantom and heterogeneous rabbit liver tissue in vivo, exhibiting heating and cooling with the accompanying quantitative characterization of the dilation and contraction of the thermally affected region. Results demonstrate that optical flow is capable of noninvasive real-time monitoring and control of interstitial laser therapy (ILT).

Acrylic Resins↗
PubMed1986

Review of optical storage technology for archiving digital medical images.

Digital optical recording (DOR) is a data-acquisition and storage technology important to the development of picture archiving and communication systems (PACS). DOR offers attractive advantages in high-density, low-cost archival storage of images and other information. At present, film is used as the storage medium for archiving images generated by both conventional equipment and digital technologies such as computed tomography, digital subtraction angiography, magnetic resonance imaging, and nuclear medicine. The basic methods of DOR data storage are discussed together with requirements essential for making DOR an acceptable alternative to film archiving. The impact of DOR technology on the operation of an imaging department is projected.

Costs and Cost Analysis↗
PubMed1982

Individual sarcomere length determination from isolated cardiac cells using high-resolution optical microscopy and digital image processing.

Discrete sarcomere lengths have been determined from dynamically contracting isolated cardiac cells with a high-speed, high-resolution direct optical imaging system. Calcium-tolerant cardiac cells from the rat are isolated by perfusion with collagenase and hyaluronidase. Individual sarcomere lengths can be determined by directly imaging the cell's striation pattern onto a solid-state charge-coupled device (CCD) detector interfaced with a digital computer. The precision of detection in a real light microscopic optical system is discussed in relation to the type of image detector, optical contract enhancement techniques, and digital image processing. The optical performance of the direct striation pattern image apparatus has been determined empirically with test grids under standard bright-field and Nomarski-differential interference contrast (DIC) conditions for application to real muscle imaging. Discrete striation positions of isolated cells have been detected and followed with high precision during phasic contraction-relaxation cycles down to average sarcomere lengths as short as 1.43 +/- 0.053 microns. The maximum rates of contraction and relaxation are rapid and synchronous in time course along the length of the cell. These results indicate that direct optical imaging can provide an accurate means to monitor discrete striations and sarcomere lengths along the length of Ca2+-tolerant heart cells.

Animals↗
PubMed2003

[Molecular imaging in rheumatoid arthritis].

Advances in molecular biology and technical developments in the field of imaging are increasingly allowing for non-invasive visualization and quantitation of biological processes at the molecular level. Such technologies, defined as molecular imaging, promise early diagnosis and improved classification of the stage and severity of disease, objective assessment of treatment efficacy, and reliable prognosis based on so-called molecular markers. Furthermore, molecular imaging is an important tool for the evaluation of physiological and pathophysiological processes and for drug development. Various different imaging modalities are available, such as conventional radiography (CR), computed tomography (CT), nuclear imaging, magnetic resonance imaging (MRI), ultrasound (US), as well as other methods including fluorescence-based optical imaging. These methods differ with respect to resolution and their potential to gather information at the anatomical, physiological, cellular and molecular level. Therefore, the choice of the imaging modality for molecular imaging depends on the questions that need to be answered. This review discusses the potential of imaging modalities for molecular imaging in rheumatoid arthritis (RA).

Animals↗
PubMedDate not supplied

Visual guidance based on optic flow: a biorobotic approach.

This paper addresses some basic questions as to how vision links up with action and serves to guide locomotion in both biological and artificial creatures. The thorough knowledge gained during the past five decades on insects' sensory-motor abilities and the neuronal substrates involved has provided us with a rich source of inspiration for designing tomorrow's self-guided vehicles and micro-vehicles, which will be able to cope with unforeseen events on the ground, under water, in the air, in space, on other planets, and inside the human body. Insects can teach us some useful tricks for designing agile autonomous robots. Since constructing a "biorobot" first requires exactly formulating the biological principles presumably involved, it gives us a unique opportunity of checking the soundness and robustness of these principles by bringing them face to face with the real physical world. "Biorobotics" therefore goes one step beyond computer simulation. It leads to experimenting with real physical robots which have to pass the stringent test of the real world. Biorobotics provide us with a new tool, which can help neurobiologists and neuroethologists to identify and investigate worthwhile issues in the field of sensory-motor control. Here we describe some of the visually guided terrestrial and aerial robots we have developed since 1985 on the basis of our biological findings. All these robots behave in response to the optic flow, i.e., they work by measuring the slip speed of the retinal image. Optic flow is sensed on-board by miniature electro-optical velocity sensors. The very principle of these sensors was based on studies in which we recorded the responses of single identified neurons to single photoreceptor stimulation in a model visual system: the fly's compound eye.

Animals↗
PubMed2002

Dural substitute for long-term imaging of cortical activity in behaving monkeys and its clinical implications.

We present a transparent silicone dural substitute, which we have been using for the last 7 years for imaging cortical dynamics in awake behaving monkeys. This substitute enabled us to record optically for more than a year intrinsic or voltage sensitive dye signals. It is thin and elastic enough to allow microelectrode to pass through without any damage, using full visual control to target the electrode to the desirable recording site. This implant has proved crucial for maintaining the cortex in a good physiological condition and for preserving its optical characteristics that are necessary for optical imaging. We describe the details of the surgical implantation of the silicone dural substitute, the maintenance of the exposed cortex over long periods of time, the cortical reaction to this implant and its possible clinical implications in humans, and the rehabilitation procedure in monkeys.

Animals↗
PubMed1997

Mechanisms of visual object recognition: monkey and human studies.

The feature-based representations of object images in the inferotemporal cortex of macaque monkeys have been further characterized by optical imaging experiments. Recently, the close correlation between the activity of inferotemporal cells and the perception of object images has been revealed by single-unit recordings from behaving monkeys. The human homologue of the monkey inferotemporal cortex has been identified through use of new non-invasive techniques.

Animals↗
PubMed1998

New technology for high-speed and high-resolution optical coherence tomography.

Optical coherence tomography (OCT) is an optical imaging technique that is capable of performing micron-scale, cross-sectional imaging of internal microstructure in biological systems. OCT is analogous to ultrasound B mode imaging except that it uses light rather than sound and performs imaging by measuring the back-scattered intensity of light from structures in tissue. We describe recent advances in OCT technology including the application of short pulse solid state lasers based on Ti: Al2O3 and Cr: Mg2SiO4 to enable high-resolution, high-speed imaging as well as the development of OCT catheter/endoscope delivery to permit imaging of internal organ systems. OCT enables the nonexcisional, in situ, real-time imaging of tissue microstructure and is thus a powerful and promising technique for optical biopsy.

Animals↗
PubMedDate not supplied

Data predictability for compression of digital fluorography images.

Images obtained by digital fluorography were checked for compressability. These images include images of coronary vessels and images of peripheral vessels. These images have a very low signal-to-noise ratio compared to the optical images usually used for developing compression methods. Configurational entropy was used to represent the information content of these images. Reversible prediction algorithms were extensively checked in a search for minimal residual information, enabling more efficient reversible compression. Optimal results were obtained for algorithms based on two or three neighboring pixels and a semiempirical rule, based on the noise level, was found which decides on the best approach. It was found that raw data images are more predictable than subtracted images although the latter are visually preferred.

Algorithms↗
PubMed2002

Morphologic detail of aging bone in human vertebrae.

To investigate aging bone structure of humans--here, in the lumbar vertebral bodies-requires methodologies that have sufficiently high resolving power yet still have sufficient width and depth of field. No clinical imaging method can come close to meeting the first requirement, leading to the disadvantage of being limited to postmortem studies. Few microscopic methods meet the second and third requisites. The three-dimensional (3D) images of bone in this article were obtained using deep-field 3D optical imaging, X-ray imaging, and scanning electron microscopy (SEM) of macerated plane parallel slices. The study of bone as a 3D object provides a different perspective from conventional two-dimensional images, and enriches our understanding of how modeling and remodeling processes regulate bone structure and connectivity. The study of ultraflat block surfaces by quantitative back-scattered electron imaging permits acquisition of data on mineral distributions and densities within a very thin layer (a continuous and perfect very thin section) in the block face. With this information, bone can be viewed as a spectrum of tissue types varying in degree of mineralization.

Adult↗
PubMed1991

3D grating optics of human vision.

The approximately 6-7 layers of closestpacked photoreceptor cell bodies in the outer nuclear layer of the human retina are interpreted as hexagonal multilayer phase or three-dimensional gratings with refractive index differences between the cell nucleus and the cytoplasm. A multilayer 3D grating of this type allows incident light to be processed by Fresnel interference in the plane of focus of the geometrical-optical system of the human eye, forming triplets of chromatic interference maxima made available, at discrete concentric locations, to the outer segments of the cones and rods for further processing. Transformation of the 3D grating spacing (in the sense of a stimulus-adaptive optic) into the dimensional periodicity of the spectral stimulus which is processed with maximum amplitude in the 111 color channel gives three chromatic signals at 559/537/447 nm in the visible 'spectral window', i.e. at spectral locations which match the 3 wavelengths of (photochemically determined) maximum spectral sensitivity in photopic vision. Variation of the cell geometry in the 3D grating gives rise to the Purkinje shift with fusion of the RED-GREEN diffraction orders at 512 nm. Color proves mathematically to be the product (varied by the diffraction order triplets) of the speed of light and the three-dimensional geometry. The chemistry of the photoreceptors, i.e. the programming of the visual pigments, would consequently be based on 3D grating optics. The human eye would process trichromatic Fourier signals, not geometrical-optical images. The first stage of color vision would be based on 3D grating optics, without the involvement of neuronal networks. New interpretations ensue for color constancy, color adaptation, color visual field, inter alia. The eye, as a trichromatic Fresneloptical modulator of the information present in the amplitude, phase and frequency of the processed light, receives considerably more information on perceived objects than it passes on to the brain. Cellular 3D gratings may also be models for the interference of acoustic, chemical and other waves in cortical processing centers.

Color Perception↗
PubMed2006

Imaging single-channel calcium microdomains.

The Ca(2+) microdomains generated around the mouth of open ion channels represent the basic building blocks from which cytosolic Ca(2+) signals are constructed. Recent improvements in optical imaging techniques now allow these microdomains to be visualized as single channel calcium fluorescence transients (SCCaFTs), providing information about channel properties that was previously accessible only by electrophysiological patch-clamp recordings. We review recent advances in single channel Ca(2+) imaging methodologies, with emphasis on total internal reflection fluorescence microscopy (TIRFM) as the technique of choice for recording SCCaFTs from voltage- and ligand-gated plasmalemmal ion channels. This technique of 'optical patch-clamp recording' is massively parallel, permitting simultaneous imaging of hundreds of channels; provides millisecond resolution of gating kinetics together with sub-micron spatial resolution of channel locations; and is applicable to diverse families of membrane channels that display partial permeability to Ca(2+) ions.

Animals↗