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Results for “Optical imaging”

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At least 217 records · Page 12Linked to original sources
PubMed2002

Feasibility of in vivo multichannel optical imaging of gene expression: experimental study in mice.

PURPOSE: To develop and test a multichannel reflectance imaging system for small animals on the basis of a previously developed single-channel setup. MATERIALS AND METHODS: The imaging system was composed of modular parts, including a light source, excitation filters, emission filters, and a charged-coupled device for recording images. On the basis of generated excitation and absorption spectra of green fluorescent protein (GFP), tricarbocyanine 5.5 (Cy5.5), and indocyanine green (ICG), filters were selected to allow spectral separation and optimize resultant recorded signal. The system was tested by using a combination of the fluorochromes to confirm spectral separation. In vivo tests were performed in nude mice with tumors that expressed cathepsin B, which could be evaluated by using a Cy5.5-based activatable probe and GFP. For each in vivo tumor type and channel, statistical analysis was performed on the basis of signal intensity in the region of interest. RESULTS: The different fluorochromes were readily distinguished with the system; characteristics such as power were determined for all wavelengths. The system demonstrated a linear response for GFP, a monotonic response for Cy5.5 over a range of more than three orders of magnitude of concentration, and a more complex response for ICG. In vivo analysis demonstrated the ability to image GFP expression and cathepsin B expression separately in tumors: As expected, marked differences were observed in GFP-expression imaging between tumor types (1,363 arbitrary units [AU] +/- 236 [SD] vs 110 AU +/- 11 for GFP-positive and GFP-negative tumors, respectively; P <.001), whereas similar cathepsin B expression (1,070 AU +/- 285 vs 1,168 AU +/- 367; P >.5) was observed. Histologic analysis confirmed in vivo findings. CONCLUSION: Imaging multiple gene expressions simultaneously in vivo by using optical imaging is feasible.

Animals↗
PubMed2005

Fiber-optic fluorescence imaging.

Optical fibers guide light between separate locations and enable new types of fluorescence imaging. Fiber-optic fluorescence imaging systems include portable handheld microscopes, flexible endoscopes well suited for imaging within hollow tissue cavities and microendoscopes that allow minimally invasive high-resolution imaging deep within tissue. A challenge in the creation of such devices is the design and integration of miniaturized optical and mechanical components. Until recently, fiber-based fluorescence imaging was mainly limited to epifluorescence and scanning confocal modalities. Two new classes of photonic crystal fiber facilitate ultrashort pulse delivery for fiber-optic two-photon fluorescence imaging. An upcoming generation of fluorescence imaging devices will be based on microfabricated device components.

Animals↗
PubMed2004

Intraoperative optical imaging of human face cortical topography: a case study.

We used intrinsic signal optical imaging to obtain maps of human somatosensory cortex during electrocutaneous stimulation of the face during a neurosurgical procedure for epilepsy. We found that human face somatotopy is organized like the macaque or cebus monkey, with peri-orbital skin located medial to peri-buccal skin, and that cortical magnification in the human is comparable to that in non-human primates. This study demonstrates that intrinsic signal imaging can be performed on humans during operative procedures with sufficient spatial resolution to reveal high-resolution topographic maps.

Adult↗
PubMed1993

Optical imaging of parallel fiber activation in the rat cerebellar cortex: spatial effects of excitatory amino acids.

Using optical imaging, the effects of excitatory amino acids and their antagonists on the spatial pattern of activity evoked by the stimulation of parallel fibers in the cerebellar cortex of the anesthetized rat were examined. A vermal folium was stained with the stryrl voltage-sensitive dye RH-795 and imaged with a cooled charge-coupled service system during the activation of the parallel fibers with surface stimulation. Stimulation of the cerebellar cortex produced discrete "beams" of optical activity consistent with extracellular field recordings. The signal-to-noise ratio was excellent (> 10:1), reducing the number of stimuli, exposure time, and acquisition time needed to produce images. Extracellular field potential recordings were used to assay neuronal activity as well as the effects of the various excitatory amino acid agonists. Application of several glutamate receptor antagonists reversibly blocked the optical signals as well as the synaptic components of the extracellular field potentials. Neither N-methyl-D-aspartate nor its antagonist, (+/-)-2-amino-7-phosphonoheptanoic acid, had any affect on the optical signals or field potentials. These results indicate that the optical signal is not due to the evoked parallel fiber activity, but is generated mainly by postsynaptic targets and the parallel fiber synaptic action is primarily mediated by non-N-methyl-D-aspartate receptors. Other excitatory amino acid agonists had a differential effect on the optical response. Glutamate and kainate increased the "on beam" optical signal evoked by parallel fiber stimulation, in amplitude and width. In contrast, quisqualate always decreased the amplitude and width of the optical beam. Also, quisqualate produced an increase in fluorescence lateral to the optical beam, possibly due to an increase in "off beam" inhibitory activity. The changes in the extracellular field potentials were in agreement with the effects on the optical signals. Two possible mechanisms are proposed to account for the inhibitory effect of quisqualate. One is that quisqualate desensitizes Purkinje cell receptors, the other is that inhibitory interneurons in the cerebellar cortex are more preferentially excited with quisqualate application which in turn inhibits Purkinje cells both "on beam" and "off beam". In conclusion, voltage-sensitive dye optical signals evoked by stimulation of the cerebellar surface were imaged at high signal-to-noise levels using a cooled charge-coupled device system. Use of excitatory amino acid agonists and antagonists demonstrated that the optical signal was dependent on postsynaptic activity and confirmed that the parallel fiber postsynaptic action is primarily mediated by non-N-methyl-D-aspartate receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed2004

In vivo tracking of bone marrow stromal cells transplanted into mice cerebral infarct by fluorescence optical imaging.

Recent experimental studies have indicated that bone marrow stromal cells (BMSC) improve neurological deficits when transplanted into the animal models of various neurological disorders, although precise mechanism still remains unclear. In this study, we developed a new in vivo fluorescence optical imaging protocol to sequentially track the transplanted into the brain of the living animals subjected to cerebral infarct. Mice BMSC were harvested from transgenic mice expressing green fluorescent protein (BMSC-GFP). They were stereotactically transplanted into the ipsilateral striatum of mice subjected to permanent middle cerebral artery occlusion after 7 days of ischemia (n=12). During 12 weeks after transplantation, the skull was exposed and the green fluorescence emitted from the brain surface was sequentially observed, using in vivo fluorescence optical microscopy. As the results, regional green fluorescence was detected in the ipsilateral parietal region 4-12 weeks after transplantation in all animals and became more apparent over the time. The images obtained through the skull were very similar to those acquired by thinning or removing the skull. Immunohistochemistry evaluation revealed that the transplanted cells migrated towards the ischemic boundary zone and expressed the neuronal or astrocytic marker, supporting the findings on fluorescence optical images. Sequential visualization of the BMSC transplanted into the brain of living animals would be valuable for monitoring the migration, growth and differentiation of the transplanted cells to explore the fate and safety of stem cell transplantation for various neurological disorders.

Animals↗
PubMed1997

Evaluation of spatial resolution as a function of thickness for time-resolved optical imaging of highly scattering media.

Previous experimental and theoretical investigations of the utility of time-resolved methods as a means of optical imaging through the human breast have indicated that a spatial resolution of approximately 1 cm is achievable by isolating the shortest path length photons which propagate through the tissue. Studies have also shown that resolution may be improved further by extrapolating the measured distribution using an appropriate model of photon transport. The experiments described here were performed in order to observe the relationship between achievable spatial resolution and the thickness of the medium. For a given time gate, an improvement in the spatial resolution was observed as the object thickness was reduced. Overall, the results indicate that a breast compression of about 1 cm may improve the limiting spatial resolution by as much as 7 mm. Less encouraging is the implication that temporal extrapolation over several orders of magnitude in intensity is required to achieve a comparable improvement in spatial resolution.

Biophysical Phenomena↗
PubMed2002

Optical imaging of glycinergic inhibition in the vestibular and cochlear nuclei.

Using multiple-site optical recording techniques, the spatiotemporal activity was observed in both the cochlear and vestibular nucleus in newborn mice. The optical responses were obviously enhanced by bath-applied strychnine. A quantitative analysis showed higher enhancements to occur in the cochlear nucleus than in the vestibular nucleus. Optical imaging enables us to visualize the spatiotemporal extent of the inhibitory receptive field after the application of strychnine.

Animals↗
PubMed2003

Optical imaging of the cervix.

Recent advances in fiber optics, sources and detectors, imaging, and computer-controlled instrumentation have stimulated a period of unprecedented growth in the development of photonics technologies for a wide variety of diagnostic and therapeutic clinical applications. These include the application of quantitative optical spectroscopy and imaging for the detection of precancerous lesions in the uterine cervix, a topic of interest at the Second International Conference on Cervical Cancer, which was held April 11-14, 2002. Investigators have applied the Littenberg method of emerging technology assessment to new optical methods used to detect cervical neoplasia. Currently, such technologies as fluorescence spectroscopy (the combination of fluorescence and diffuse reflectance spectroscopy), tri-modal spectroscopy, and light-scattering spectroscopy that probe the spectral characteristics of tissue are being investigated. Optical technologies that create images of subcellular structure without biopsy subsequent to pathology that currently are under investigation include in vivo confocal imaging and optical coherence tomography. Numerous small studies have demonstrated the potential of these optical technologies. What remains to be elucidated are the fundamental biophysical origins of variations in remitted optical signals between normal and dysplastic tissue. Large multicenter randomized controlled trials are needed to confirm the detection and imaging capabilities of optical technology. Furthermore, the development of contrast agents that could boost detection with these technologies is needed, and basic biologic characterization of signals should be pursued. Applying the Littenberg assessment will help ensure that superior, not simply alternative, technologies are implemented.

Cervix Uteri↗
PubMed1996

Optical imaging of respiratory burst activity in newborn rat medullary block preparations.

We report on the optical imaging of excitation propagation induced by electrical stimulation of the nucleus tractus solitarius (NTS) area and subsequent inspiratory burst activity in the ventrolateral medulla (VLM) of a medullary block preparation. A medullary block preparation with a thickness of 1.0-1.4 mm was made from brainstems isolated from 0- to 4-day-old rats and stained with a fluorescent voltage-sensitive dye, RH795. Neuronal responses in the VLM evoked by electrical stimulation were recorded as a fluorescence change using an optical recording apparatus with a 128 x 128 photodiode array and a maximum time resolution of 0.6 ms. Motoneuronal activity was simultaneously recorded at the contralateral hypoglossal nerve roots. Neuronal excitation evoked by stimulation of the NTS area propagated to the VLM through the intermediate reticular zone (IRt). In contrast, caudal VLM stimulation induced excitation which propagated to the rostral VLM without any detectable excitation propagation in the IRt toward the NTS area from the VLM. NTS stimulation also induced an inspiratory burst activity in the hypoglossal nerve root activity with a 150-200 ms delay. Fluorescence changes corresponding to the inspiratory burst activity were observed in the VLM which coincided with the area in which the localization of many respiratory neurons had been demonstrated in previous studies using whole-brainstem preparations. The present results show the feasibility of using optical recordings for the analysis of respiratory neuron activity as well as for analysis of the transmission pathway of afferent and/or efferent information in the medulla.

Animals↗
PubMed1997

Advances in optical imaging of biomedical media.

In this article, we have presented an overview of fundamental issues involved in mediphotonic imaging, and reviewed some of the emerging techniques for early-light transillumination imaging of body organs. The results on human breast tissues presented here, together with the data accumulated and advances made by researchers around the globe, not only demonstrate the feasibility of optical imaging as a clinical procedure but indicate a road map to reach that goal. The milestones include evaluation of relative merits of available approaches for a particular imaging application; selection of diagnostic wavelengths, as well as sources to generate and detectors to monitor light at those wavelengths; accumulation of data on optical, spectroscopic, and transport properties of tissues and organs; in vivo testing; prototype instrumentation development; clinical trials; governmental approval; cost analysis and marketing; and finally system improvement based on feedback from end users. A new era of optical clinical imaging is at the door.

Animals↗
PubMed2002

Optical imaging of intrinsic signals induced by peripheral nerve stimulation in the in vivo rat spinal cord.

We examined neural response patterns evoked by peripheral nerve stimulation in in vivo rat spinal cords using an intrinsic optical imaging technique to monitor neural activity. Adult rats were anesthetized by urethane, and laminectomy was performed between C5 and Th1 to expose the dorsal surface of the cervical spinal cord. The median, ulnar, and radial nerves were dissected, and bipolar electrodes were implanted in the forelimb. Changes in optical reflectance were recorded from the dorsal cervical spinal cord in response to simultaneous stimulation of the median and ulnar nerves using a differential video acquisition system. In the region of the cervical spinal cord, intrinsic optical signals were detected between C5 and Th1 at wavelengths of 605, 630, 730, 750, and 850 nm: the image with the largest signal intensity and highest contrast was obtained at 605 nm. The signal intensity and response area expanded with an increase in the stimulation intensity and varied with the depth of the focal plane of the macroscope. The intrinsic optical response was mostly eliminated by Cd(2+), suggesting that the detected signals were mainly mediated by postsynaptic mechanisms activated by sensory nerve fibers. Furthermore, we succeeded in imaging neural activity evoked by individual peripheral nerve stimulation. We found that the response areas related to each peripheral nerve exhibited different spatial distribution patterns and that there were animal-to-animal variations in the evoked neural responses in the spinal cord. The results obtained in this study confirmed that intrinsic optical imaging is a very useful technique for acquiring fine functional maps of the in vivo spinal cord.

Animals↗
PubMed1997

Simultaneous digitization of upper airway fiber-optic images and respiratory signals.

We developed an inexpensive and efficient method for simultaneously digitizing respiratory signals and fiber-optic images of the upper airway. The main components of the system are a fiber-optic scope, a charge coupled device video camera, and a personal computer equipped with a frame grabber and an A/D board. The frame grabber digitizes images at five frames per second while the A/D board samples six respiratory signals at 25 samples per second. Digitized images are saved only in the event that the user instructs the computer to do so in order to limit disk space requirements. A circular buffering technique provides continuous storage of the most recent 50 frames in frame grabber memory. This feature gives the user up to 10 seconds, following the beginning of a respiratory event, to initiate the saving of images to computer hard disk. A postacquisition program displays the data acquired during the sleep study and allows the user to interactively select images for subsequent upper airway area measurement. This system enables us to observe and quantify the dynamics of the upper airway during different breathing conditions with minimal time and cost. It is also a potential clinical tool to use to determine the site of obstruction during sleep in patients with obstructive sleep apnea.

Computers↗
PubMed1995

Optical imaging of rat somatosensory cortex reveals representational overlap as topographic principle.

We measured reflectance changes by means of optical imaging of intrinsic signals to study the topography of the paw representations in rat somatosensory cortex. Following circumscribed tactile stimulation of single digits or pads, we found large and partially overlapping areas of reflectance changes (delta R). The diameters of their focal zones defined at 75% maximal delta R were in the range of 150 microns and preserved all details of the underlying maps. Zones of overlap were in the range 15-25% measured at half-maximal delta R. In contrast, we found sharp boundaries with no overlap between the fore- and hindpaw representations. The data suggest that large and overlapping cortical maps constitute a normal type of neural representation supporting the idea of a distributed neural processing scheme.

Animals↗
PubMed1993

Optical imaging of Cl- permeabilities in normal and CFTR-expressing mouse L cells.

Single cell optical imaging techniques were used to compare Cl- conductances in cystic fibrosis transmembrane conductance regulator (CFTR)-expressing and control mouse L cell fibroblasts. Elevation of intracellular cAMP levels in control cells was without effect on plasma membrane Cl- permeability, whereas cells engineered to stably express CFTR displayed a 20-fold enhancement of plasma membrane Cl- permeability in response to cAMP. Control L cells displayed Ca(2+)-, as well as swelling-activated Cl- permeabilities, which were small compared with cAMP-stimulated permeability in CFTR-expressing cells. CFTR-expressing cells also displayed a similar swelling-activated Cl- permeability. Whereas 50% of the CFTR-expressing cells possessed a small Ca(2+)-activated Cl- permeability similar to control cells, the other cells displayed an enhanced response which was never observed in control cells. Intracellular cAMP determinations suggested that this latter result might be explained by a Ca(2+)-induced rise of cAMP. The cAMP-activated and Ca(2+)-activated Cl- conductances had different anion selectivities, as measured by light scattering of suspended cells. Activation of protein kinase C was without effect on Cl- permeability in CFTR-expressing cells, nor did it modify cAMP-activation of Cl- permeability. Thus, expression of human CFTR in L cells does not confer cAMP-sensitivity to pre-existing, endogenous Ca(2+)- or swelling-activated Cl- channels, but rather confers a novel Cl- conductance which is regulated by cAMP. Osmotic cell swelling and PKC activation are without specific effect in CFTR-expressing L cells. However, elevated [Ca2+]i may play a role in activating a Cl- conductance specifically associated with CFTR.

Animals↗
PubMed2005

Three-element phased-array approach to diffuse optical imaging based on postprocessing of continuous-wave data.

We present a multielement phased-array approach to diffuse optical imaging based on postprocessing of continuous-wave data for the improvement of spatial resolution. In particular, we present a theoretical and experimental analysis of the performance of a three-element source array in the study of an optically turbid medium with two embedded cylindrical inclusions. We find that the proposed phased-array approach is able to resolve two cylinders with side-to-side separation of 10 mm that are not resolved by the intensity associated with a single light source.

Image Enhancement↗
PubMed2006

Optical imaging of bacterial infection in living mice using a fluorescent near-infrared molecular probe.

An optical imaging probe was synthesized by attaching a near-infrared carbocyanine fluorophore to an affinity group containing two zinc(II) dipicolylamine (Zn-DPA) units. The probe has a strong and selective affinity for the surfaces of bacteria, and it was used to image infections of Gram-positive S. aureus and Gram-negative E. coli bacteria in living nude mice. After intravenous injection, the probe selectively accumulates at the sites of localized bacterial infections in the thigh muscles of the mice.

Animals↗
PubMed1995

Emergence of functional circuits in ferret visual cortex visualized by optical imaging.

The emergence of functional lateral interactions in ferret visual cortex was monitored using high speed optical imaging of voltage-sensitive dye signals in brain slices. Prior to the time of eye opening, lateral activation was restricted to a narrow columnar region. During the week following eye opening, the extent of lateral propagation of activity more than doubled. Selective interruption of specific pathways in the slice, combined with pharmacological and anatomical experiments, determined that this lateral propagation was mediated by horizontal projections made within layer 2/3. These results indicate that functional horizontal interactions emerge only after axons begin branching and in parallel with, but not prior to, the refinement of orientation selectivity.

Age Factors↗