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Results for “Optical imaging”

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At least 595 records · Page 33Linked to original sources
PubMed2005

Long-term tracing of adenoviral expression in rat and rabbit using luciferase imaging.

BACKGROUND: Luciferase optical imaging provides a novel method to monitor transgene expression in small living animals. As the genetic and immunological heritages of particular animals significantly affect the expression of adenovirus-delivered transgenes, it is essential to know the expression patterns specific to athymic nude and Sprague-Dawley rats, two strains commonly used in rodent models. In this study we set out to determine these patterns. At the same time, we tested luciferase optical imaging in a larger animal, the rabbit. METHODS: A recombinant luciferase adenoviral vector was injected subcutaneously or intramuscularly into athymic nude rats, Sprague-Dawley rats, and Dutch Belted rabbits. The luciferase expression was assessed using a cooled charge-coupled device. RESULTS: The luminescent signal was capable of passing through at least 1.3 cm of muscle tissue and proved to be much stronger when luciferin was delivered via a local injection than by an intraperitoneal injection. Although the types of immune cells differed between immunodeficient and immunocompetent rats, similar amounts and patterns of luciferase expression were observed in the musculature in two rat strains during the 1st month after a viral intramuscular injection. The duration of luciferase expression was longer than 15 months in athymic nude rats, 9 months in Sprague-Dawley rats, and 6 months in rabbits following a direct viral injection. CONCLUSIONS: Luciferase expression after adenoviral gene delivery can persist for longer than 6 months, even in immunocompetent animals. Live imaging of luciferase expression can be performed not only in small animals, but also in larger animals such as rabbits.

Adenoviridae↗
PubMed2005

Functional assessment of glutamate clearance mechanisms in a chronic rat glaucoma model using retinal ganglion cell calcium imaging.

Using optical imaging of retinal ganglion cell (RGC) calcium dynamics in living intact retinal wholemount preparations, we tested whether RGCs in an experimental rat glaucoma model were more sensitive to exogenously applied glutamate as a result of deficient glutamate clearance mechanisms. In contrast to post-natal rat RGCs in purified cultures, in which the calcium influx induced by 200 microm NMDA and 10 microm glutamate was approximately equivalent, application of up to 500 microm glutamate did not affect calcium levels in RGCs in retinal wholemounts, even though the RGCs responded to 200 microm NMDA. Glutamate (500 microm) did elicit a RGC calcium response in retinal wholemounts when glutamate transporters were inhibited pharmacologically with DL-threo-beta-benzyloxyaspartate, confirming the presence of glutamate clearance mechanisms in this intact retina preparation. The effect of glutamate was then assessed on retinas from rats with chronically elevated intraocular pressure in one eye, produced by the injection of hypertonic saline into an episcleral vein. Application of up to 500 microm glutamate had no effect on RGC calcium levels, while millimolar concentrations of glutamate induced a calcium signal in RGCs that was indistinguishable from that in fellow control retinas. Therefore, there was no evidence for a global defect in glutamate uptake in this rat model of experimental glaucoma. Imaging glutamatergic calcium dynamics of RGCs in retinal wholemounts represents a novel methodology to probe glutamate transporter function and dysfunction in an intact CNS tissue system.

Animals↗
PubMed2003

Improvement of optical resolution in far-field imaging by optical multiplication.

Based on the idea of the complex filters suggested by Toraldo di Francia in 1952, super-resolved imaging has been achieved by using interferometric image multiplication. The question of whether super-resolution implies a limited field of view is discussed, and an analytical criterion to decide this question is obtained. Three different imaging configurations are investigated, all of which gave a spatial resolution exceeding that corresponding to the full open aperture of the optical system. A resolution limit 55% of the Rayleigh limit was achieved for incoherently illuminated objects. One price that must be paid for the super-resolution is inefficient use of the light source. A second price is a limitation to the usable field of view.

Fourier Analysis↗
PubMed2003

Optic disc imaging in conscious rats and mice.

PURPOSE: To determine whether useful images of the optic discs of conscious rats and mice can be obtained by using a photo slit lamp and a modified Goldmann-type fundus contact lens. METHODS: Testing was performed with a photo slit lamp equipped with two 2x teleconverters and a digital camera through a Goldmann-type fundus contact lens that was fabricated for the rodent eye. RESULTS: Images of the rat and mouse optic discs were obtained that are comparable to those used by ophthalmologists to assess optic neuropathy in glaucoma, a key part of the standard of care and of clinical investigation of this disease. The cup in the optic disc image of these rodents is darker than the neural rim of the disc, rather than lighter, as it is in humans. CONCLUSIONS: In addition to the application of this imaging method to studies of the effect on optic disc cupping of induced increased intraocular pressure in rats and mice, by detecting and documenting the onset and the course of optic neuropathy, it should be valuable in identifying animal models of glaucoma, in studying neuropathogenic mechanisms, and in assessing the effects of experimental therapies.

Animals↗
PubMed2002

Genetically expressed cameleon in Drosophila melanogaster is used to visualize olfactory information in projection neurons.

Complex external stimuli such as odorants are believed to be internally represented in the brain by spatiotemporal activity patterns of extensive neuronal ensembles. These activity patterns can be recorded by optical imaging techniques. However, optical imaging with conventional fluorescence dyes usually does not allow for resolving the activity of biologically defined groups of neurons. Therefore, specifically targeting reporter molecules to neuron populations of common genetic identity is an important goal. We report the use of the genetically encoded calcium-sensitive fluorescence protein cameleon 2.1 in the Drosophila brain. We visualized odorant-evoked intracellular calcium concentration changes in selectively labeled olfactory projection neurons both postsynaptically in the antennal lobe, the primary olfactory neuropil, and presynaptically in the mushroom body calyx, a structure involved in olfactory learning and memory. As a technical achievement, we show that calcium imaging with a genetically encoded fluorescence probe is feasible in a brain in vivo. This will allow one to combine Drosophila's advanced genetic tools with the physiological analysis of brain function. Moreover, we report for the first time optical imaging recordings in synaptic regions of the Drosophila mushroom body calyx and antennal lobe. This provides an important step for the use of Drosophila as a model system in olfaction.

Animals↗
PubMed2003

High-resolution optical coherence microscopy for high-speed, in vivo cellular imaging.

Optical coherence microscopy (OCM) is demonstrated with a high-speed, broadband, reflective-grating phase modulator and a femtosecond Ti:Al2O3 laser. The novel system design permits high-resolution OCM imaging in a new operating regime in which a short coherence gate is used to relax the requirement for high-numerical-aperture confocal axial sectioning. In vivo cellular imaging is demonstrated in the Xenopus laevis tadpole and in human skin with a 3-microm coherence gate and a 30-microm confocal gate. The ability to achieve cellular imaging with a lower numerical aperture should facilitate the development of miniaturized probes for in vivo imaging applications.

Animals↗
PubMed1997

Magnetic resonance imaging in optic neuropathy.

Magnetic resonance imaging has revolutionised the ability to investigate intrinsic disease of the anterior optic pathways. We review the data accumulated from this technique not only in the conditions, such as neoplasia, which have traditionally been the domain of neuroimaging, but also in inflammatory, metabolic and degenerative diseases.

Humans↗
PubMed2005

Time-domain optical mammography SoftScan: initial results.

RATIONALE AND OBJECTIVES: Near-infrared (NIR) technology appears promising as a noninvasive technique for breast cancer screening and diagnosis. The technology capitalizes on the relative transparency of human tissue in this spectral range and its sensitivity to the main components of the breast: water, lipid, and hemoglobin. In this study, the authors report quantitative measurements of these components and the functional contrast between healthy and diseased tissue. MATERIALS AND METHODS: A four-wavelength time domain optical imaging system was used to perform noninvasive NIR measurements in the breast of 49 women both pre- and postmenopausal, ages 24-80. Algorithms based on a diffusive model of light transport provided absolute bulk and local values of breast constituent concentrations. RESULTS: Important variations in the functional and structural NIR properties of the breast were observed. Demographics trend were noticed in accordance with breast physiology. In the 23 cases imaged with suspicious masses, the optical images were consistent with the mammographic findings. Substantial contrast between masses and adjacent tissue is observed. Moreover, consistent differences between malign and benign cases are found with optical imaging. CONCLUSION: The results of this pilot study illustrate the sensitivity of optical techniques to the composition of the breast. In addition, preliminary data suggest that benign and malignant tumors can potentially be noninvasively differentiated with optical imaging. Moreover, statistically significant discrimination based on deoxy-hemoglobin content between malign and benign cases was found with optical imaging (P = .0184, one-tailed t test).

Adult↗
PubMed2005

Fourier-domain holographic optical coherence imaging of tumor spheroids and mouse eye.

Fourier-domain holography (FDH) has several advantages over image-domain holography for optical coherence imaging of tissue. Writing the hologram in the Fourier plane significantly reduces background arising from reference light scattered from the photorefractive holographic film. The ability to use FDH is enhanced by the use of a diffuse target, such as scattering tissue, rather than specular targets, because the broader angular distribution from diffuse targets is transformed into a relatively uniform distribution in the Fourier plane. We demonstrate significantly improved performance for Fourier-domain optical coherence imaging on rat osteogenic sarcoma tumor spheroids and mouse eye. The sensitivity is documented at -95 dB.

Algorithms↗
PubMed2002

Spectral characterization of acousto-optic filters used in imaging spectroscopy.

The purpose of this investigation is to improve the study of the characteristics of noncollinear acoustooptic tunable filters (AOTFs) used in imaging spectroscopy. Three filters were characterized and the results compared with tuning models to verify that device operation can be reliably predicted in advance. All these devices use tellurium dioxide as the interaction medium and have large geometric apertures for spectroscopic imaging applications in the spectral range 0.5-3.5 microm. The device characteristics that we studied were compared with the results of AOTF models, and the spectral and angular dependence of acoustic frequency and bandpass width for both output polarization states were confirmed by measurements. One of the AOTFs was used as a dispersive element coupled to external imaging optics. We summarize measurements of the basic spectral and imaging characteristics in this configuration.

Journal Article↗
PubMed2005

Contrast response in visual cortex: quantitative assessment with intrinsic optical signal imaging and neural firing.

While previous studies showed that intrinsic optical signals spatially correspond with electrophysiological responses in mammalian visual cortex, the quantitative correspondence of their response strengths is open to question. Measurement of both signals' strength as functions of visual stimulus contrast provides an opportunity for quantitative comparison. Towards that end, the spatial and temporal properties of the optical signal impose important constraints upon quantification of its strength. We used intrinsic optical signal imaging and single unit recording to measure responses to drifting gratings at contrasts ranging from 10-80% in cat area 18. We calculated the average difference images for pairs of oppositely moving, or orthogonally oriented, gratings at each contrast and evaluated three different methods for quantifying optical signal strength. After about 2.5 s, the spatial patterns of optical images and the time course of their strength were contrast-invariant. This "space-time-contrast separability" for optical response implies a spatial uniformity of the optical contrast response functions, provides an objective basis to guide temporal averaging of optical signals, and validates a scalar metric of optical signal strength. Optically measured contrast response functions increase monotonically and saturate at high contrasts, qualitatively resembling those from single units. However, quantitative comparison reveals a nonlinear relationship with neural firing, such that the optical response reaches half of its maximum when the neural response has reached only around 20% of its maximum. This relationship suggests that intrinsic optical signals are relatively more sensitive to weak signals than neural firing.

Animals↗
PubMed1995

Image forming optics with a common aperture for fast switching between TEM magnified image and selected area diffraction.

Image-forming optics that can switch between a magnified image and its diffraction pattern without any movement of aperture is proposed. Both the images are alternately taken and are simultaneously shown in a monitor. This type of optics is applied to the design of an ultrahigh-voltage electron microscope (H-3000) and is tested at 100 kV TEM.

Image Processing, Computer-Assisted↗
PubMed1990

Gadolinium-DTPA-enhanced magnetic resonance imaging in optic neuropathies.

Magnetic resonance imaging (MRI), after intravenous administration of the paramagnetic agent gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), showed enhancement of the optic nerve in 7 of 13 patients with acute optic neuritis. Four of these patients had Gd-DTPA enhancement of the intracranial optic nerve and two had involvement of the optic nerve at the orbital apex, ipsilateral to the eye with visual loss. Gadolinium-DTPA enhancement of both intracranial optic nerves was seen in one of two patients with bilateral retrobulbar neuritis. Two patients with acute radiation-induced optic neuropathy also had Gd-DTPA enhancement of the intracranial optic nerve. The authors recommend MRI with Gd-DTPA as the neuro-diagnostic procedure of choice for visualization of increased permeability of the blood-brain barrier in acute optic neuritis and radiation-induced optic neuropathy.

Adolescent↗
PubMed2004

Optic disc imaging by Heidelberg retinal tomogram in congenital optic disc anomaly.

We evaluated two cases of congenital optic disc anomaly with the Heidelberg Retinal Tomograph (HRT) that could be mistaken for glaucomatous optic disc. One was an optic disc coloboma with a visual field defect and the other had an optic disc pit without a visual field defect. HRT was abnormal only in the eye with optic disc pit with normal fields. While HRT can be a valuable adjunct to disc evaluation and follow-up, it cannot be used in isolation in the differentiation of abnormal from normal optic discs.

Adult↗
PubMed2005

Optical tomography with ultrasound localization: initial clinical results and technical challenges.

Optical tomography with ultrasound localization utilizes co-registered ultrasound lesion structure information to guide optical imaging reconstruction. A hand-held probe consisting of a commercial ultrasound transducer and near infrared optical imaging sensors was used to simultaneously acquire ultrasound images and optical measurements. A dual-mesh scheme was used to map the ultrasound-visible lesions to finer-grid lesion regions and coarser-grid background regions for optical imaging reconstruction. As a result, optical imaging reconstruction was well-conditioned for inverse mapping of lesion hemoglobin concentration and blood oxygen saturation. Initial clinical results have shown that early stage invasive cancers may be distinguished by a two-fold greater total hemoglobin concentration compared with fibroadenomas and other benign lesions. Initial results of advanced cancers have shown that the hemoglobin distribution is highly distorted and heterogeneous and the distorted distributions correlate with histological microvessel density counts and could be used to assess chemotherapy response.

Adenocarcinoma↗
PubMed2004

A mouse optical simulation environment (MOSE) to investigate bioluminescent phenomena in the living mouse with the Monte Carlo method.

RATIONALE AND OBJECTIVES: As an important part of bioluminescence tomography, which is a newly developed optical imaging modality, mouse optical simulation environment (MOSE) is developed to simulate bioluminescent phenomena in the living mouse and to predict bioluminescent signals detectable outside the mouse. This simulator is dedicated to small animal optical imaging based on bioluminescence. MATERIALS AND METHODS: With the parameters of biological tissues, bioluminescent sources, and charge coupled device (CCD) detectors, the 2-dimensional/3-dimensional MOSE simulates the whole process of the light propagation in 2-dimensional/3-dimensional biological tissues using the Monte Carlo method. Both the implementation details and the software architecture are described in this article. RESULTS: The software system is implemented in the Visual C++ programming language with the OpenGL techniques and has a user-friendly interface facilitating interactions relevant to bioluminescent imaging. The accuracy of the system is verified by comparing the MOSE results with independent data from analytic solutions and commercial software. CONCLUSION: As shown in our simulation and analysis, the MOSE is accurate, flexible, and efficient to simulate the photon propagation for bioluminescence tomography. With graduate refinements and enhancements, it is hoped that the MOSE will become a standard tool for bioluminescence tomography.

Computer Simulation↗