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At least 973 records · Page 54Linked to original sources
PubMed2002

[Visual impression of photographic density of the brain in head CT images: verification of optical illusion by visual subjective evaluation of medical images].

The purpose of this study was to clarify the psychological influence of optical illusion on the photographic density of the brain in head CT images. In this study, I attempted to compare the visual impression of photographic density of the brain using visual subjective evaluation according to observers and cases. The results showed that the visual impression of photographic density of the brain at cerebellar CT depended upon the mode of appearance of the optical illusion (assimilation, contrast, picture frame effect, etc.). In addition, that impression varied according to differences in cases (difference of picture pattern) and observers. Further, it was clarified that the optical illusion had been observed according to individual differences among observers. Moreover, cases could be divided into two main classes. Some cases were recognized as a kind of outline figure (the white skull was recognized as an induction color, and the brain as a non-induction color) with assimilation, and consequently the brain seemed whitish. In other cases (the white skull was not recognized as an induction color) in which there was no assimilation, the brain did not seem whitish. This was considered to have occurred because the degree of influence of the skull on the visual impression of the photographic density of the brain had changed according to differences in cases.

Brain↗
PubMed1981

Video-enhanced contrast, differential interference contrast (AVEC-DIC) microscopy: a new method capable of analyzing microtubule-related motility in the reticulopodial network of Allogromia laticollaris.

A new method called Allen Video-enhanced Contrast, Differential Interference Contrast (AVEC-DIC) microscopy is shown to be sufficiently sensitive to detect several new features of microtubule-related motility in the reticulopodial network of the foraminifer, Allogromia. The method takes advantage of the variable gain and offset features of a binary video camera to operate the DIC microscope under conditions highly favorable for video imaging, but in which the optical image is virtually invisible to the eye yet retains its full information when viewed by a suitable video camera. The improvements are made possible by setting a dé Senarmont compensator to lambda/9-lambda/4 at maximal working aperture of internally corrected planapochromatic objectives. Under these conditions, the offset feature of the video camera can reject so much stray light from the instrument and specimen that contrast compares favorably with that observed in high-extinction images, and polarizing rectifiers offer scarcely any advantage. Freed from the constraints of the light-limited conditions of DIC microscopy, video images can be recorded 60 times per second, or over 1,000 times the rate of photomicrographs at comparable magnifications under high-extinction conditions. Application of this method to the reticulopodial network of Allogromia has shown that cytoplasmic organelles are translocated only in contact with single microtubules or bundles of microtubules, and that these organelles fail to move when separated from microtubules. Microtubules themselves undergo both axial translatory ("sliding") and lateral "zipping and unzipping" movements that have been suggested to occur during mitosis and other biological processes.

Animals↗
PubMed1992

HOME: highly optimized microscope environment.

The Highly Optimized Microscope Environment (HOME) is a computerized microscope designed to assist pathologists and cytotechnicians in clinical routine tasks. The prototype system consists of a IBM-PC compatible computer and a light microscope in which a built-in high-resolution computer display image is superimposed on the optical image of the specimen. Also, a manually operated encoding stage and objective turret encoder are used to provide continuous monitoring of the stage coordinates and microscope magnification to the computer. This allows any position on a slide to be uniquely defined and makes it possible to measure interactively lengths and areas larger than the size of the microscope field. Software, written in the C language and operating under the MS-DOS/MS-Windows environment, is controlled by means of a mouse-driven cursor moving over menu light-buttons displayed on the microscope image. The HOME microscope workstation is potentially useful in a wide range of applications such as i) tagging information on particular cells and tissue structures that can thus be accurately located and relocated, ii) performing morphometric measurement, differential counting, and stereological assessment of biological specimens, and iii) training and educating laboratory personnel. Finally, HOME will offer in the near future a user-friendly interface for automatic image processing of cells and tissue entities in interactively selected specimen areas.

Animals↗
PubMed1994

Combining patch-clamp and optical methods in brain slices.

Combining patch-clamp and optical imaging techniques in brain slices offers several advantages for physiological studies of nerve cells. Numerous practical considerations weigh heavily in this design of an apparatus suitable for such combined measurements. These considerations include the thickness of the slices, the type of microscope to be used for imaging and the kind of optical signal to be measured. A system that combine optical and patch-clamp methods can be modified readily to permit studies of intracellular and extracellular signaling pathways via flash photolysis of caged compounds.

Animals↗
PubMed1994

Dendritic morphology in epileptogenic cortex from TRPE patients, revealed by intracellular Lucifer Yellow microinjection and confocal laser scanning microscopy.

Biopsy material was obtained from cortical epileptogenic zones (eight temporal, one occipital, one parietal and one frontal) of eleven patients aged 1.5-47 years with therapy-resistant partial epilepsy (TRPE) undergoing epilepsy surgery. Control autopsy material (two temporal, two occipital, one parietal and one frontal) was removed from six neurologically healthy cases within 6-10 hours postmortem delay. In each specimen, 100-300 pyramidal and non-pyramidal neurons were visualized by intracellular Lucifer Yellow microinjection. Single neurons were imaged using CLSM generated serial optical sections; 2-D reconstruction of each neuron was made using z-projection of serial optical images, and 3-D reconstructions and rotations were computerized. Neuronal maps from TRPE biopsies, compared to control autopsies, show markedly increased numbers of dendritic abnormalities of single pyramidal and non-pyramidal neurons in layers I, II-III, V-VII, and in the subcortical white matter. The abnormalities include: (1) increased number of non-pyramidal cells in layer I; (2) many pyramidal cells with two or three dendrites originating apically, rather than one single apical dendrite, in layers II-III; (3) atypical orientation of oblique apical and basal dendrites in pyramidal neurons of layers II-VII; (4) increased number of atypical 'dinosaur-like' and fusiform cells in layers V-VII; (5) numerous neurons in the white matter. These abnormalities may be etiological in cases with early onset, and predisposing in cases with late onset.

Adolescent↗
PubMed1992

Inherent problems of attempts to apply sonar and vibrotactile sensory aid technology to the perceptual needs of the blind.

A program of research dealing with two types of sensory aids for the blind--sonar and vibrotactile--is described. Rather than immediately assessing the aids in the mobility context, which has customarily been the case, the aids' capabilities are considered in terms of the major functions of vision, that is, the exteroceptive perception of objects, surfaces, and events of the environment, and the proprioceptive perception of the self, especially the self in relation to the environment. Although sonar aids function very well for localizing objects and for providing acoustic flow specifying self-movement, they do not provide high acuity pattern and shape information due to the long wavelength of ultrasound relative to light. This limitation is considered specifically with respect to the visual accomplishment of recovery of three-dimensional structure/motion from dynamic two-dimensional images. Vibrotactile sensory aids using optical imaging can deliver detailed pattern information to the skin and thus permit assessment of the extent to which a nonvisual system can mediate the recovery of structure problem. However, in even moderately cluttered or complicated environments the skin proves unable to resolve the amount of stimulation it receives vibrotactually. The limitations of sonar and vibrotactile sensory aids are discussed with respect to future sensory substitution efforts as well as their implications for understanding differences and similarities among the senses.

Blindness↗
PubMed2004

Walter Thompson Welford 31 August 1916 - 18 September 1990.

Walter Thompson Welford (Walter Weinstein until 1957), born in London, left Hackney Technical Institute at the age of 16 years to become a technician at the London Hospital and later at Oxford University Biochemistry Department. In 1942, after obtaining a first-class honours external degree in mathematics from London University by private study, he returned to London to work at Adam Hilger Ltd. He moved to Imperial College, London, as a research assistant in 1947, became a lecturer in 1951, a senior lecturer in 1959, Reader in 1964 and Professor of Physics in 1973. He was elected a Fellow of The Royal Society in 1980. After formal retirement in 1983 he continued to be research active at Imperial College and the University of Chicago until his death from throat cancer in 1990.Walter's scientific work was in the craft of optical instrumentation, in which he became an internationally recognized master. His contributions ranged from basic aberration theory to the design, construction and testing of a vast ranger of optical instrumentation. His research fields were principally lens aberrations, optical microscopy, bubble chamber optics, laser speckle, non-imaging optics, diffraction gratings and diffraction lenses. Many will also remember him as a kindly and inspiring educator.

Equipment and Supplies↗
PubMed2006

Neuropsychology: traditional and new methods of investigation.

The neuropsychological assessment is an integral part of the clinical investigation of patients suffering from epilepsy. The aim of the evaluation is to determine disease-related and treatment-related effects on cognition and behavior in order to orient therapeutic interventions, by taking into account the compensatory mechanisms that are available to the patient. Examples of the tests best illustrating the classical neuropsychological protocol are presented. Neuropsychology also plays an important role in the assessment of language lateralization in patients slated for epilepsy surgery. Traditionally, this has been achieved by means of the rather invasive Wada procedure. However, with the advent of new neuroimaging techniques, this procedure is gradually being replaced by minimally invasive or noninvasive methods, such as functional magnetic resonance imaging, positron emission tomography, and optical imaging. In the present paper, we discuss some of the newer techniques that are available to the neuropsychologist for the study of the impact of epilepsy on cerebral functioning.

Amobarbital↗
PubMed2004

Design and demonstration of a miniature catheter for a confocal microendoscope.

The fluorescence confocal microendoscope provides high-resolution, in vivo imaging of cellular pathology during optical biopsy. The confocal microendoscope employs a flexible fiber-optic catheter coupled to a custom-built slit-scan confocal microscope. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The 3-mm-diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope, adding microscopic imaging capability to conventional endoscopy. The design and performance of the miniature objective and focus assembly are discussed. Primary applications of the system include diagnosis of disease in the gastrointestinal tract and female reproductive system.

Catheterization↗
PubMed2005

Current state and future development of intracranial neuroendoscopic surgery.

Since the introduction of the modern, smaller endoscopes in the 1960s, neuroendoscopy has become an expanding field of neurosurgery. Neuroendoscopy reflects the tendency of modern neurosurgery to aim towards minimalism; that is, access and visualization through the narrowest practical corridor and maximum effective action at the target point with minimal disruption of normal tissue. Transventricular neuroendoscopy allows the treatment of several pathologies inside the ventricular system, such as obstructive hydrocephalus and intra-/paraventricular tumors or cysts, often avoiding the implantation of extracranial shunts or more invasive craniotomic approaches. Endoscopic endonasal transphenoidal surgery allows the treatment of pathologies of the sellar and parasellar region, with the advantage of a wider vision of the surgical field, less traumatism of the nasal structures, greater facility in the treatment of possible recurrences and reduced complications. However, an endoscope may be used to assist microsurgery in virtually any kind of neurosurgical procedures (endoscope-assisted microsurgery), particularly in aneurysm and tumor surgery. Basic principles of optical imaging and the physics of optic fibers are discussed, focusing on the neuroendoscope. The three main chapters of neuroendoscopy (transventricular, endonasal transphenoidal and endoscope-assisted microsurgery) are reviewed, concerning operative instruments, surgical procedures, main indications and results.

Brain↗
PubMed2003

Applications and limitations of perfusion-dependent functional brain mapping for neurosurgical guidance.

Perfusion-dependent brain mapping modalities, such as functional magnetic resonance imaging, positron emission tomography, and optical imaging of intrinsic signals, have become increasingly popular for neurosurgical guidance because they offer a relatively rapid and noninvasive means of mapping brain function. These modalities are unique because they rely on perfusion-related signals that are coupled with neuronal activity to map the brain instead of measuring electrophysiological responses. They consequently present unique challenges to the clinician in terms of understanding the significance and limitations of the maps they produce. In particular, one must be aware of limitations of the modalities with respect to spatial specificity, sensitivity, and reliability of these maps and how the presence of intracranial lesions may further complicate these issues. The authors review the evolution, interpretation, and limitations of perfusion-based brain mapping techniques, with special attention to clinical implications of the brain maps.

Brain Diseases↗
PubMedDate not supplied

Correlation between corneal and total wavefront aberrations in myopic eyes.

PURPOSE: Corneal topography data expressed as corneal aberrations are frequently used to report corneal laser surgery results. However, the optical image quality depends on all optical elements of the eye, including the human lens. We investigated correlations between corneal and total wavefront aberrations and the relevance of corneal aberrations for representing the optical quality of the total eye. METHODS: Thirty-three eyes of 22 myopic patients were measured using a corneal topography system and a Tscherning-type wavefront analyzer. Pupils were dilated to at least 6 mm in diameter. All measurements were centered with respect to the line of sight. Corneal and total wavefront aberrations were calculated up to the 6th Zernike order in the same reference plane. RESULTS: Statistically significant correlations (P<.05) between corneal and total wavefront aberrations were found for astigmatism (C3,C5) and all 3rd Zernike order coefficients such as coma (C7,C8). No statistically significant correlations were found for 4th, 5th, or 6th order Zernike coefficients. On average, all Zernike coefficients for corneal aberrations were larger than the Zernike coefficients for total wavefront aberrations. CONCLUSIONS: Due to the lack of correlation between corneal and total wavefront aberrations in most of the higher order aberrations, measurement of corneal aberrations are of limited use for representation of the optical quality of the human eye, especially after corneal laser surgery. Corneal aberrations and optical elements within the eye are optically balanced. As a consequence, ideal customized ablations must take both corneal and total wavefront aberrations into consideration.

Adult↗
PubMed2001

Findings on retinal topography and thickness mapping in age-related macular degeneration.

PURPOSE: To report alterations in the retinal topography and thickness in typical cases of age-related macular degeneration (ARMD). METHODS: An optical imaging system was applied to patients with ARMD with alterations in the retinal structures. The system generates a series of 20 optical section images that encompass a 2 mm x 2 mm retinal area. The optical sections are digitized and analyzed to provide topographic maps of the vitreo-retinal and chorio-retinal surfaces and the retinal thickness. RESULTS: Retinal topography and thickness mapping in a normal eye corresponded to normal anatomy. Topographic mapping in a patient with confluent drusen indicated elevation of the vitreo-retinal surface. Retinal topography in a patient with retinal pigment epithelium detachment displayed localized elevation of the chorio-retinal surface. The thickness map in a patient with geographic atrophy of the retinal pigment epithelium revealed retinal thinning. In the patients with choroidal neovascularization, the vitreoretinal and chorio-retinal surfaces were elevated. The chorio-retinal surface map in a patient with evolving disciform scar displayed topographic variations corresponding to the fibrovascular tissue underlying the serous detachment. CONCLUSION: Retinal topography and thickness mapping is useful for visualization and evaluation of pathologic alterations in retinal structures due to ARMD.

Adult↗
PubMed2004

Symmetries, inversion formulas, and image reconstruction for optical tomography.

We consider the image reconstruction problem for optical tomography with diffuse light. The associated inverse scattering problem is analyzed by making use of particular symmetries of the scattering data. The effects of sampling and limited data are analyzed for several different experimental modalities, and computationally efficient reconstruction algorithms are obtained. These algorithms are suitable for the reconstruction of images from very large data sets.

Algorithms↗
PubMedDate not supplied

Universal interface for exchange of medical images via magneto-optical discs.

Digital images are the ever-growing basis of modern medical imaging and treatment. Despite the advent of the DICOM 3.0 standard for medical image communication it still requires cumbersome efforts to export images from imaging modalities to other computer systems. This is true especially for smaller institutions, which often have limited resources for standardized image transfer. To gain access even to these data we developed an exchange interface on the basis of magneto-optical discs (MO-discs), as they are usually available in most of the imaging modalities in use today. Unfortunately images on MO-discs are usually stored in formats specific for each manufacturer. Therefore special routines to access the data on MO-discs had to be developed for each company or even each scanner. Over 10,000 CT and MRI images including their header information from different General Electric and Siemens scanners were extracted successfully from MO-discs. The interface proved to be reliable and easy to handle by technicians. Support of additional manufacturers and of the DICOM 3.0 standard are work in progress.

Computer Communication Networks↗
PubMed1999

Optic nerve enhancement on magnetic resonance imaging in arteritic ischemic optic neuropathy.

Although optic nerve enhancement may be seen in magnetic resonance imaging of radiation-induced ischemic optic neuropathy, similar enhancement in ischemic optic neuropathy has not been previously reported in the English-language neuroophthalmologic literature. We report three cases of optic nerve enhancement in biopsy-proven arteritic ischemic optic neuropathy. Clinicians should consider giant cell arteritis in the differential diagnosis of an optic neuropathy with optic nerve enhancement on magnetic resonance imaging.

Aged↗
PubMed2000

Combined optical and fluorescence imaging for breast cancer detection and diagnosis.

In this article, we present a novel approach that combines the best aspects of both endogenous optical imaging and exogenous fluorescent lifetime and yield imaging for breast cancer detection and diagnosis. Using this approach, spatial distributions of optical properties, fluorescence lifetime, and yield in tissue can be reconstructed from measured excitation and emission data at the surface of the breast tissue by regularized inverse algorithms. We show images from simulated data, as well as images from experimental data using tissue-like phantom materials in the laboratory.

Algorithms↗