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At least 1,495 records · Page 83Linked to original sources
PubMed2005

Experimental demonstration of an analytic method for image reconstruction in optical diffusion tomography with large data sets.

We report the first experimental test of an analytic image reconstruction algorithm for optical tomography with large data sets. Using a continuous-wave optical tomography system with 10(8) source-detector pairs, we demonstrate the reconstruction of an absorption image of a phantom consisting of a highly scattering medium containing absorbing inhomogeneities.

Algorithms↗
PubMed2005

Non-invasive fluorescence imaging of cell death in fresh human colon epithelia treated with 5-Fluorouracil, CPT-11 and/or TRAIL.

Apoptosis is instrumental in several physiological/pathophysiological processes and is a frequently used end-point in the development of anti-neoplastic compounds. Despite ample data on several colon cancer cell lines, little is known about the susceptibility of human colon to apoptosis following treatment with established chemotherapeutics. By treating fresh human colonic explants with 5-Fluorouracil (200 microg/ml), CPT-11 (100 microg/ml) and/or TRAIL (100 ng/ml) we readily detected a signal in situ using FITC-VAD-FMK at different time points, whereas labeling of colonic explants with EGFP-conjugated Annexin V proved less specific. Although TRAIL treatment alone appeared to cause little apoptosis in human colonic epithelia versus the control, we observed a greater number of cells undergoing apoptosis when a combination of CPT-11 and TRAIL was used as compared to either agent alone. This is the initial demonstration of TRAIL-induced apoptosis with or without a chemotherapeutic agent in fresh primary human colon epithelia explants. Thus, human colonic explants may provide a valuable reference point when candidate therapeutic compounds triggering apoptosis in colon cancer cell lines, xenografts or mouse models are developed. The results support the feasibility of developing non-invasive optical imaging strategies to detect apoptosis through direct visualization of injury to human colonic epithelia in vivo.

Adolescent↗
PubMed2003

Optical recordings of membrane potential using genetically targeted voltage-sensitive fluorescent proteins.

Optical imaging of electrical activity using voltage-sensitive dyes has been envisaged for many years as a powerful method to investigate multineuronal representation of information processing in brain tissue. This article describes the advent of novel genetically targeted voltage-sensitive fluorescent proteins. This new class of membrane voltage sensors overcomes previous limitations related to the nonselective staining of membranes associated with conventional voltage-sensitive dyes. Here, we discuss the methodology, applications, and potential advantages of this novel technique.

Animals↗
PubMed2002

Corneal optical aberrations and retinal image quality in patients in whom monofocal intraocular lenses were implanted.

OBJECTIVES: To compare retinal image quality and optical corneal aberrations in patients in whom monofocal polymethyl methacrylate intraocular lenses (IOLs) were implanted with those in healthy subjects of a similar older age (60-70 years old) and to use the results to suggest improved optical designs of IOLs to maximize retinal image quality. METHODS: A double-pass apparatus was used to measure retinal image quality for 3-, 4-, and 6-mm pupil diameters. Corneal aberrations for a 4-mm pupil were calculated by a ray-tracing technique from the elevations provided by corneal topography. Two groups of 20 subjects of a similar older age were studied: in one group, polymethyl methacrylate monofocal IOLs were implanted; and in a second group, healthy subjects were used as a reference. RESULTS: The average retinal image quality was similar in older healthy patients and in patients in whom IOLs were implanted, with both groups having a significantly worse image quality than healthy younger subjects (aged 20-30 years). Both groups were more tolerant to defocus than younger subjects. CONCLUSIONS: The average retinal image quality of patients in whom IOLs were implanted was worse than that of healthy younger subjects despite the good optical quality of isolated IOLs. This apparent paradox can be understood by the nature of the aberration coupling in the eyes that undergo implantation. The ideal substitute for the natural lens is not an IOL with the best-isolated optical performance, but rather one designed to compensate for the aberrations of the cornea-a design somehow inspired by the crystalline lens of younger subjects.

Aged↗
PubMed2004

[Optical coherence tomography in the evaluation of the oral cavity mucosa. Part II. Benign and malignant diseases].

This paper is the last one in the series of publications on the investigation of the capability of Optical Coherence Tomography (OCT) in diagnostic of state of oral cavity mucosa. Part II demonstrates the diversity of optical images, different forms specific to leukoplakia, lichen planus and squamous cell carcinoma on the basis of the investigation of 56 pathologic lesions of 43 patients with precancer and cancer of oral cavity. The OCT sensitivity in malignancy detection in oral cavity is high - 83%, specificity is 98%, and accuracy is 81%. The kappa coefficient of interobserver agreement is 0.76.

Carcinoma, Squamous Cell↗
PubMed2003

Functional organization of the cat visual cortex in relation to the representation of a uniform surface.

Neuronal activity in the early visual cortex has been extensively studied from the standpoint of contour representation. On the other hand, representation of the interior of a surface surrounded by a contour is much less well understood. Several studies have identified neurons activated by a uniform surface covering their receptive fields, but their distribution within the cortex is not yet known. The aim of the present study was to obtain a better understanding of the distribution of such neurons in the visual cortex. Using optical imaging of intrinsic signals, we found that there are a group of surface-responsive regions located in area 18, along the area 17/18 border, that tend to overlap the singular points of the orientation-preference map. Extracellular recordings confirmed that neurons responsive to uniform plane stimuli are accumulated in these regions. Such neurons also existed outside the surface-responsive regions around the singular points. These results suggest that there exists a functional organization related to the representation of a uniform surface in the early visual cortex.

Animals↗
PubMed2002

Steady-state and dynamic contrast MR imaging of human prostate cancer xenograft tumors: a comparative study.

Understanding tumor vascular physiology is critically important for developing non-invasive, molecularly targeted diagnostic agents and therapies. In this study, using three different human prostate cancer xenografts (MDA PCa 2b, PC3, and LnCap), structural and physiological parameters of neoplastic vasculature and interstitum were explored with a widely available magnetic resonance imaging (MRI) pulse sequence (3D SPGR: spoiled gradient echo). Using dual injection technique employing two T1 contrast agents of different molecular masses (Weissleder, R., Cheng, H. C., Marecos, E., Kwong, K. K., Bogdanov, A., Jr. Eur. J. Cancer 34, 1448-1454 (1998).), steady state (SS) MRI measurements and dynamic contrast agent enhancement (DCE) MRI measurements were simultaneously acquired and analyzed using a two-compartment model for calculating parameters reflecting tumoral architecture and physiology. In particular, interstitial volume and vascular permeability were independently quantified using these two different MRI techniques. Relative vascular water exchange rate, calculated by the flip angle (FA) dependence of measured blood volume using SS technique, and vascular permeability of contrast agent, extrapolated from DCE MRI, were compared. It was found that the SS and DCE techniques were comparable and yielded similar qualitative results for extravascular compartment (interstitial volume). However, the permeability (water exchange rate and contrast agent vascular permeability) values were in disagreement. The results of MR studies are important for interpreting optical imaging results obtained using long-circulating of tumor-associated enzymatic activity.

Contrast Media↗
PubMed2005

Arthritis imaging using a near-infrared fluorescence folate-targeted probe.

A recently developed near-infrared fluorescence-labeled folate probe (NIR2-folate) was tested for in vivo imaging of arthritis using a lipopolysaccharide intra-articular injection model and a KRN transgenic mice serum induction mouse model. In the lipopolysaccharide injection model, the fluorescence signal intensity of NIR2-folate (n = 12) and of free NIR2 (n = 5) was compared between lipopolysaccharide-treated and control joints. The fluorescence signal intensity of the NIR2-folate probe at the inflammatory joints was found to be significantly higher than the control normal joints (up to 2.3-fold, P < 0.001). The NIR2-free dye injection group showed a persistent lower enhancement ratio than the NIR2-folate probe injection group. Excessive folic acid was also given to demonstrate a competitive effect with the NIR2-folate. In the KRN serum transfer model (n = 4), NIR2-folate was applied at different time points after serum transfer, and the inflamed joints could be detected as early as 30 hours after arthritogenic antibody transfer (1.8-fold increase in signal intensity). Fluorescence microscopy, histology, and immunohistochemistry validated the optical imaging results. We conclude that in vivo arthritis detection was feasible using a folate-targeted near-infrared fluorescence probe. This receptor-targeted imaging method may facilitate improved arthritis diagnosis and early assessment of the disease progress by providing an in vivo characterization of active macrophage status in inflammatory joint diseases.

Animals↗
PubMed2005

Spectral imaging microscopy demonstrates cytoplasmic pH oscillations in glial cells.

Glial cells exhibit distinct cellular domains, somata, and filopodia. Thus the cytoplasmic pH (pH(cyt)) and/or the behavior of the fluorescent ion indicator might be different in these cellular domains because of distinct microenvironments. To address these issues, we loaded C6 glial cells with carboxyseminaphthorhodafluor (SNARF)-1 and evaluated pH(cyt) using spectral imaging microscopy. This approach allowed us to study pH(cyt) in discrete cellular domains with high temporal, spatial, and spectral resolution. Because there are differences in the cell microenvironment that may affect the behavior of SNARF-1, we performed in situ titrations in discrete cellular regions of single cells encompassing the somata and filopodia. The in situ titration parameters apparent acid-base dissociation constant (pK'(a)), maximum ratio (R(max)), and minimum ratio (R(min)) had a mean coefficient of variation approximately six times greater than those measured in vitro. Therefore, the individual in situ titration parameters obtained from specific cellular domains were used to estimate the pH(cyt) of each region. These studies indicated that glial cells exhibit pH(cyt) heterogeneities and pH(cyt) oscillations in both the absence and presence of physiological HCO(3)(-). The amplitude and frequency of the pH(cyt) oscillations were affected by alkalosis, by acidosis, and by inhibitors of the ubiquitous Na(+)/H(+) exchanger- and HCO(3)(-)-based H(+)-transporting mechanisms. Optical imaging approaches used in conjunction with BCECF as a pH probe corroborated the existence of pH(cyt) oscillations in glial cells.

Animals↗
PubMed1999

The critical period for ocular dominance plasticity in the Ferret's visual cortex.

Microelectrode recordings and optical imaging of intrinsic signals were used to define the critical period for susceptibility to monocular deprivation (MD) in the primary visual cortex of the ferret. Ferrets were monocularly deprived for 2, 7 or >14 d, beginning between postnatal day 19 (P19) and P110. The responses of visual cortical neurons to stimulation of the two eyes were used to gauge the onset, peak, and decline of the critical period. MDs ending before P32 produced little or no loss of response to the deprived eye. MDs of 7 d or more beginning around P42 produced the greatest effects. A rapid decline in cortical susceptibility to MD was observed after the seventh week of life, such that MDs beginning between P50 and P65 were approximately half as effective as those beginning on P42; MDs beginning after P100 did not reduce the response to the deprived eye below that to the nondeprived eye. At all ages, 2 d deprivations were 55-85% as effective as 7 d of MD. Maps of intrinsic optical responses from the deprived eye were weaker and less well tuned for orientation than those from the nondeprived eye, with the weakest maps seen in the hemisphere ipsilateral to the deprived eye. Analysis of the effects of 7 d and longer deprivations revealed a second period of plasticity in cortical responses in which MD induced an effect like that of strabismus. After P70, MD caused a marked loss of binocular responses with little or no overall loss of response to the deprived eye. The critical period measured here is compared to other features of development in ferret and cat.

Aging↗
PubMed1999

Geometrical and topological relationships between multiple functional maps in cat primary visual cortex.

The mammalian striate cortex is organized such that the receptive field properties of neighboring neurons change gradually across the cortical surface, forming so-called cortical maps. The presence of such maps has been demonstrated in different species of mammals for several parameters characterizing the visual space: retinotopy, ocular dominance, orientation, direction of motion and spatial frequency. In this study we used the optical imaging of intrinsic signals to simultaneously record the multiple functional maps in the same animal in order to obtain a comprehensive set of rules that govern mutual dependencies among the functional maps. Our results indicate that while orientation, direction and ocular dominance are represented on the cortex in a mutually dependent manner, the representation of spatial frequency is independent of the other types of cortical representations. The presence and/or absence of mutual dependence among the multiple functional maps are suggested to provide an important clue for the understanding of the development of visual cortical information representation in neonatal animals.

Animals↗
PubMed2002

The dark side of galaxy formation.

I discuss the discovery of a population of extremely luminous, but very dusty and very distant, galaxies in the submillimetre (submm) waveband. Almost all the light emitted by the stars in these galaxies is absorbed by interstellar dust (which is produced by the same stars) and re-radiated in the far-infrared. This leaves little to be detected at optical wavelengths and results in most of these galaxies being effectively invisible in even the deepest optical images obtainable with the Hubble space telescope. Yet this population contributes most of the light emitted by galaxies at wavelengths of lambda > or approximately equal 100 microm over the lifetime of the Universe. Together with other observations, this suggests that perhaps up to half of all the stars seen in galaxies today were formed in very dusty regions in the early Universe. Hence, studying the galaxies detected in the submm wavebands is critical for developing and testing models of galaxy formation and evolution. Individually, these luminous submm galaxies are forming stars a thousand times faster than our Galaxy is at the present-day, sufficiently fast to form all the stars in the most luminous galaxy in the local Universe within a short period, up to ca. 0.1-1 Gyr. Detailed study of a handful of examples of this population confirm these estimates and unequivocally identify the bulk of this submm-selected population with dusty, star-burst galaxies in the very distant Universe. The extreme faintness of this population in the optical and near-infrared wavebands, resulting from their obscuration by dust, means that our understanding of the detailed nature of these galaxies is only slowly growing. I give a brief summary of the properties of these highly obscured systems and describe the wide range of facilities currently being developed that will greatly aid in their study.

Journal Article↗
PubMed2004

Analysing one isolated single walled carbon nanotube in the near-field domain with selective nanovolume Raman spectroscopy.

In this paper, we describe a new method to the selective nanovolume analysing of one isolated single walled carbon nanotube (SWNT). This concept is based on actually available imaging micro-spectrometry systems for working in near-field domain combined with a stigmatic solid immersion lens. This combination of different analytical methods, and modified and configured equipment entitles us to expand the functionality toward a three-dimensional (3D) nanovolume Raman mapping and photoluminescence intensity with a possible discrimination in polarization, as well as photoluminescence decaytime constant mapping with their unique combination. Subsequently, selective spectra can be acquired from the same location on the samples. By spectrally selecting a SWNT, we registered the spatial distribution of the emitted photons in x, y, z vectors to determine the position of a SWNT in the near-field domain. For the SWNTs that are localized with an accuracy better than 18 nm in the x, y and <1 nm in the z directions, we demonstrate an analytical sensitivity close to a single nanotube with unity throughput. This near-field capability is applied to resolve local variations unambiguously in the Raman spectrum along one single SWNT. Finally, in this paper, we report what we believe to be the first evidence of Raman mapping and 3D real optical imaging of carbon nanotubes with near-field resolution.

Image Processing, Computer-Assisted↗
PubMed1996

Imaging developing neural morphology using optical coherence tomography.

Imaging technologies offer numerous possibilities to investigate the processes involved in neural development. The optical coherence tomography (OCT) technology is analogous to ultrasound backscatter microscopy except reflections of light are detected rather than sound. The OCT technology combines high-resolution in vivo imaging in a diode-based benchtop instrument capable of micron-scale resolution in transparent and non-transparent biological specimens. In this paper, we examine the potential of using OCT for the investigation of developing neural morphology. To demonstrate the capabilities of this technique in assessing neural development, we have chosen to image early normal and abnormal neural morphology in a common developmental biology model, Xenopus laevis. In vivo images clearly identify gross and subtle differences in neural structure and may offer an alternative to the costly and time-consuming process of repeated histological preparation for neural developmental studies. Because imaging can be performed rapidly and repeatedly, the morphological changes of single specimens can be followed throughout development. To illustrate the future potential of this technique, a state-of-the-art Cr4+:forsterite modelocked laser is used as a broad bandwidth light source to image individual cells in a developing specimen.

Animals↗
PubMed1999

Layer-specific horizontal propagation of excitation in the auditory cortex.

Optical imaging was conducted in rat auditory cortex slice preparations to study how horizontal excitation propagates in the cerebral cortex. When a horizontal cut was made between supragranular and infragranular layers, electrical stimulation of layer II/III elicited horizontally propagating excitation in supragranular layers with the same propagating velocities as those seen before a cut was made. Electrical stimulation of layer VI or the border between the white matter and layer VI also elicited horizontally propagating excitation in infragranular layers with the same propagating velocities as those seen before a cut was made. These results suggest that the horizontal propagation of excitation in supragranular and infragranular layers can occur independently in the auditory cortex.

Animals↗
PubMed1989

Photoreceptor topography of the retina in the adult pigtail macaque (Macaca nemestrina).

In spite of the crucial role retinal photoreceptors play in mapping optical images into a pattern of neural excitation, there are no complete studies of photoreceptor topography in any primate retina. We have measured the spatial density and inner segment areas of cones and rods across the whole mounted retinas of three adult pigtail macaques (Macaca nemestrina) and constructed maps of photoreceptor density and inner segment diameter. These retinas contain an average of 3.1 million cones (2.8-3.3 million), with an average peak foveal cone density of 210,000 cones/mm2 (190,000-260,000 cones/mm2). Cone density falls steeply with increasing eccentricity, to 100,000 cones/mm2 at 200 microns from the fovea, and to 50,000 cones/mm2 at 750 microns. Imposed on this gradient is a "streak" of higher cone density along the horizontal meridian. At equivalent eccentricities, cone density is higher in nasal and inferior retina. Cone inner segments increase in diameter from 2.3 microns at the foveal center to 11 microns in far temporal retina and 10 microns in far nasal retina. These retinas contain an average of 60.1 million rods (44.9-75.3 million). Rod density is zero within 20 microns of the foveal center, increases to the crest of a "rod ring" at the eccentricity of the optic disk, and then declines. Central rod topography is asymmetric, with higher densities in superior retina. Density along the crest of the rod ring peaks in superior retina at 177,000 rods/mm2, dips as low as 120,000 rods/mm2 along the horizontal meridian, and increases to about 150,000 rods/mm2 in inferior retina. Far peripheral rod topography is relatively symmetric around the fovea. Rod inner segment diameter ranged from 1.5 microns in the fovea to 4 microns at the temporal edge and 3.4 microns at the nasal edge of the retina. At eccentricities exceeding 6 mm, rod inner segment diameter was greater temporally than nasally. Cone inner segments cover 85-90% of the central fovea, with extrareceptor space accounting for the remainder. Cone coverage declines with increasing eccentricity to 20% at the temporal edge and 35% at the nasal edge of the retina. In contrast, rod coverage increases from zero at the foveal center to a maximum of 65% in temporal retina and 50% in nasal retina. The photoreceptor topography of the pigtail macaque is qualitatively similar to that of other macaques and to humans. Photoreceptor topography is formed by a complex interaction between regional changes in cone and rod density and inner segment diameter.

Animals↗
PubMed1996

Spatial and temporal analysis of evoked neural activity in optical recordings from American cockroach antennal lobes.

The spatio-temporal patterns of neural activity evoked by electrical stimuli to the antennal nerve (AN) in male cockroach antennal lobes (ALs) in vivo were analyzed by optical imaging using a voltage-sensitive dye. The response pattern was initially a depolarization on the AN and subsequently a depolarization followed by a hyperpolarization on the whole area of macroglomerulus (MG) and a part of ordinary glomerulus (OG). It was suggested by the pharmacological results that the depolarizing responses on the AL consist of both a presynaptic response, representing synchronous compound action potentials from the AN, and a postsynaptic response, representing synchronous compound excitatory postsynaptic potentials and action potentials from neurites of AL neurons, and that the inhibitory responses of GABAergic local interneurons in the AN are different in time course from that in the AL.

Action Potentials↗
PubMed2006

Component-dependent urine responses in the rat accessory olfactory bulb.

To investigate how pheromonal information is processed in the rat accessory olfactory bulb, we optically imaged intrinsic signals to obtain high-resolution maps of activation induced by urinary stimulation. Application of volatile components in male urine mainly induced activation in the anterior accessory olfactory bulb, irrespective of the sex, whereas volatile female urine elicited activation not only in the anterior but also to some extent in the caudal part of the posterior accessory olfactory bulb of male, but not female, rats. Nonvolatile components of both male and female urine induced activation mainly in the rostral part of the posterior and to a lesser extent in the anterior accessory olfactory bulb, irrespective of the sex. These results indicate that volatile and nonvolatile urinary components activate the anterior and posterior subdivisions of the accessory olfactory bulb, respectively.

Animals↗