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Results for “Optical imaging”

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At least 703 records · Page 39Linked to original sources
PubMed2003

Protease sensors for bioimaging.

Optical imaging of specific molecular targets and pathways in vivo has recently become possible through continued developments in imaging equipment, reconstruction algorithms, and more importantly the availability of imaging reporter molecules. These reporter molecules encompass photoproteins expressed in vivo and exogenously administered probes detectable by fluorescence and/or bioluminescence imaging. One particularly enticing aspect of optical imaging is the ability to design activatible probes with inherent amplification. This review summarizes our experience in developing novel near-infrared fluorescent (NIRF) imaging agents that report on protease activities. These agents are designed to be biocompatible, highly activatible, and able to produce bright NIRF following protease cleavage.

Animals↗
PubMed2005

Dynamic optical breast imaging: a new technique to visualise breast vessels: comparison with breast MRI and preliminary results.

The purpose of our study was to explore and evaluate an innovative imaging approach, which consists on imaging the breast parenchyma by means of photoluminescence detectors (LED) and analysis of dynamic data. Breast magnetic resonance imaging (MRI) was chosen as the reference imaging method, as this is considered to be nowadays the gold standard for breast vascularisation evaluation. Preliminary results reveal a good correlation between breast MRI findings and light images.

Adult↗
PubMed1990

[MR imaging of optic neuritis using short T1 IR (inversion recovery)].

We evaluated the ability of MRI using short T1 inversion recovery (STIR) to diagnose optic neuritis. Eleven patients with previous or recent attack of optic neuritis were studied with MRI at 0.5 tesla. STIR images revealed high signal regions in 7 of 12 symptomatic and 5 of 10 asymptomatic nerves. Three of five asymptomatic nerves with high intensity were pertinent to the cases with past attack and seemed to reflect the demyelinating change. The other two nerves were pertinent to the cases without past attack and seemed to show occult lesions. We consider that STIR is useful in detection of optic nerve lesions associated with optic neuritis.

Humans↗
PubMed1997

Wavelet representations for monitoring changes in teeth imaged with digital imaging fiber-optic transillumination.

Digital imaging fiber-optic transillumination (DI-FOTI) is a novel method to detect and monitor dental caries, using light, a charge-coupled device (CCD) camera, and computer-controlled image acquisition. The advantages of DIFOTI over radiography include: no ionizing radiation, no film, real-time diagnosis, and higher sensitivity in detection of early lesions not apparent to X-ray, as demonstrated in vitro. Here, we present a method of processing DIFOTI images, acquired at different times, for monitoring changes. Of central importance to this application is pattern matching of image frames that is invariant to translation and rotation of a tooth, relative to the field of view of the imaging camera, and that is robust to changes in illumination source intensity. Our method employs: 1) wavelet modulus maxima representations for segmentation of teeth images; 2) first and second moments of gray level representations of DIFOTI images in the spatial domain, to estimate tooth location and orientation; and 3) multiresolution wavelet magnitude representations for quantitative monitoring. Even with illumination source intensity variation, it is demonstrated in vitro that such wavelet representations can facilitate detection of simulated clinical changes in light transmission that cannot be detected in the spatial domain.

Algorithms↗
PubMed1998

Optical chemical imaging of tobacco mosaic virus in solution at 60-nm resolution.

Scanning near-field optical microscopy can provide images with a resolution less than the wavelength of light, and therefore ought in principle to be of great value in studies of biological structures. In this work we show how for the first time images have been obtained of tobacco mosaic virus particles at 60-nm resolution, combined with chemical imaging using monoclonal antibodies under in vitro conditions.

Antibodies, Monoclonal↗
PubMed2006

Bifunctional antibody-Renilla luciferase fusion protein for in vivo optical detection of tumors.

An anti-carcinoembryonic antigen (CEA) antibody fragment, the anti-CEA diabody, was fused to the bioluminescence enzyme Renilla luciferase (RLuc) to generate a novel optical imaging probe. Native RLuc or one of two stabilized variants (RLucC124A, RLuc8) was used as the bioluminescent moiety. A bioluminescence ELISA showed that diabody-luciferase could simultaneously bind to CEA and emit light. In vivo optical imaging of tumor-bearing mice demonstrated specific targeting of diabody-RLuc8 to CEA-positive xenografts, with a tumor:background ratio of 6.0 +/- 0.8 at 6 h after intravenous injection, compared with antigen-negative tumors at 1.0 +/- 0.1 (P = 0.05). Targeting and distribution was also evaluated by microPET imaging using (124)I-diabody-RLuc8 and confirmed that the optical signal was due to antibody-mediated localization of luciferase. Renilla luciferase, fused to biospecific sequences such as engineered antibodies, can be administered systemically to provide a novel, sensitive method for optical imaging based on expression of cell surface receptors in living organisms.

Amino Acid Sequence↗
PubMed2005

Design and implementation of dynamic near-infrared optical tomographic imaging instrumentation for simultaneous dual-breast measurements.

Dynamic near-infrared optical tomographic measurement instrumentation capable of simultaneous bilateral breast imaging, having a capability of four source wavelengths and 32 source-detector fibers for each breast, is described. The system records dynamic optical data simultaneously from both breasts, while verifying proper optical fiber contact with the tissue through implementation of automatic schemes for evaluating data integrity. Factors influencing system complexity and performance are discussed, and experimental measurements are provided to demonstrate the repeatability of the instrumentation. Considerations in experimental design are presented, as well as techniques for avoiding undesirable measurement artifacts, given the high sensitivity and dynamic range (1:10(9)) of the system. We present exemplary clinical results comparing the measured physiologic response of a healthy individual and of a subject with breast cancer to a Valsalva maneuver.

Algorithms↗
PubMed2006

Optical molecular imaging for systems biology: from molecule to organism.

The development of highly efficient analytical methods capable of probing biological systems at system level is an important task that is required in order to meet the requirements of the emerging field of systems biology. Optical molecular imaging (OMI) is a very powerful tool for studying the temporal and spatial dynamics of specific biomolecules and their interactions in real time in vivo. In this article, recent advances in OMI are reviewed extensively, such as the development of molecular probes that make imaging brighter, more stable and more informative (e.g., FPs and semiconductor nanocrystals, also referred to as quantum dots), the development of imaging approaches that provide higher resolution and greater tissue penetration, and applications for measuring biological events from molecule to organism level, including gene expression, protein and subcellular compartment localization, protein activation and interaction, and low-mass molecule dynamics. These advances are of great significance in the field of biological science and could also be applied to disease diagnosis and pharmaceutical screening. Further developments in OMI for systems biology are also proposed.

Animals↗
PubMed1999

Potential sources of intrinsic optical signals imaged in live brain slices.

Changes in how light is absorbed or scattered in biological tissue are termed intrinsic optical signals (IOSs). Imaging IOSs in the submerged brain slice preparation provides insight into brain activity if it involves significant water movement between intracellular and extracellular compartments. This includes responses to osmotic imbalance, excitotoxic glutamate agonists, and oxygen/glucose deprivation, the latter leading to spreading depression. There are several misconceptions regarding these signals. (1) IOSs are not generated by glial swelling alone. Although neuronal and glia sources cannot yet be directly imaged, several lines of evidence indicate that neurons contribute significantly to the changes in light transmittance. (2) Excitotoxic swelling and osmotic swelling are physiologically different, as are their associated IOSs. Hyposmotic swelling involves no detectable neuronal depolarization of cortical pyramidal neurons, only the passive drawing in of water from a dilute medium across the cell membrane. In contrast excitotoxic swelling involves sustained membrane depolarization associated with inordinate amounts of Na+ and Cl- entry followed by water. IOSs demonstrate substantial damage in the latter case. (3) Osmotic perturbations do not induce volume regulatory mechanisms as measured by IOSs. The osmotic responses measured by IOSs in brain slices are passive, without the compensatory mechanisms that are assumed to be active on a scale suggested by studies of cultured brain cells under excessive osmotic stress. (4) Spreading depression (SD) can cause neuronal damage. Innocuous during migraine aura, SD induces acute neuronal damage in brain slices that are metabolically compromised by oxygen/glucose deprivation, as demonstrated by IOSs. Neighboring tissue where SD does not spread remains relatively healthy as judged by a minimal reduction in light transmittance. IOSs show that the metabolic stress of SD combined with the compromise of energy resources leads to acute neuronal damage that is resistant to glutamate antagonists. (5) While hyperosmotic conditions reduce LT by causing cells to shrink, excitotoxic conditions reduce LT by causing dendritic beading. This conformational change increases light scattering even as the tissue continues to swell.

Animals↗
PubMed1990

[Laser scanning in ophthalmology].

The current state of the art for the major laser scanning methods, laser scanning ophthalmoscopy (LSO) and laser tomographic scanning (LTS) is discussed and the function principles are described. Experience with a prototype of each instrument from Rodenstock (LSO) and Heidelberg Instruments (LTS) is reported. LSO imaging of the cornea, vitreous, retina, and optic disc, as well as on-line processing is demonstrated with examples (nerve fibre colour coding and histograms). Measurement of the cornea, optic disc and retinal topography with LTS is also demonstrated with examples. An example of polarization optical imaging of the cornea's assumed interferometric "tension patterns" is shown. The current status and future possibilities of laser scanning, its expanded diagnostic potential with microperimetry, IR scanning angiography and polarization optic imaging and measurement (eg. nerve fibre thickness) is discussed extensively. The safety aspects of laser light exposure of the macula are also mentioned. Laser scanners as imaging and measuring sensors of unknown accuracy open a new area of possibly revolutionary diagnostic possibilities.

Cornea↗
PubMed2005

Time-resolved diffuse optical tomographic imaging for the provision of both anatomical and functional information about biological tissue.

We present in vivo images of near-infrared (NIR) diffuse optical tomography (DOT) of human lower legs and forearm to validate the dual functions of a time-resolved (TR) NIR DOT in clinical diagnosis, i.e., to provide anatomical and functional information simultaneously. The NIR DOT system is composed of time-correlated single-photon-counting channels, and the image reconstruction algorithm is based on the modified generalized pulsed spectral technique, which effectively incorporates the TR data with reasonable computation time. The reconstructed scattering images of both the lower legs and the forearm revealed their anatomies, in which the bones were clearly distinguished from the muscles. In the absorption images, some of the blood vessels were observable. In the functional imaging, a subject was requested to do handgripping exercise to stimulate physiological changes in the forearm tissue. The images of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentration changes in the forearm were obtained from the differential images of the absorption at three wavelengths between the exercise and the rest states, which were reconstructed with a differential imaging scheme. These images showed increases in both blood volume and oxyhemoglobin concentration in the arteries and simultaneously showed hypoxia in the corresponding muscles. All the results have demonstrated the capability of TR NIR DOT by reconstruction of the absolute images of the scattering and the absorption with a high spatial resolution that finally provided both the anatomical and functional information inside bulky biological tissues.

Algorithms↗
PubMed2003

Morphological changes in blood vessels produced by hyperosmotic agents and measured by optical coherence tomography.

Optical tissue clearing by hyperosmotic chemical agents significantly increases light depth penetration in skin and may improve light-based therapeutics such as laser treatment of cutaneous vascular lesions. A feasibility study was conducted to evaluate the potential role of optical clearing by glycerol in laser treatment of cutaneous vessels. Optical imaging was performed to investigate the morphological effects of glycerol on blood vessels of skin. Blood vessels were imaged using Doppler optical coherence tomography in in vivo hamster skin treated with glycerol. Images were obtained from the subdermal side to assess morphological changes in the blood vessels caused by glycerol and from the epidermal side to assess enhanced Doppler imaging of blood vessels. Application of glycerol to the subdermis resulted in venule stasis and for prolonged treatment times, arteriole stasis. In cases where flow remained in arterioles, an improved Doppler signal was detected from blood vessels when imaging transepidermally compared with the native condition. Intensity images indicated changes in blood optical properties and improved contrast of skin cross sections after glycerol application. The observed optical and morphological effects were reversed upon hydration of the skin with phosphate-buffered saline. The combination of increased depth of light penetration and the temporary slowing or cessation of flow in blood vessels could mean improved laser treatment of vessels.

Animals↗
PubMed2005

Cholinergic modulation of the spatiotemporal pattern of hippocampal activity in vitro.

The aim of this study was to use optical imaging with voltage-sensitive dyes (Di-4-ANEPPS), to examine the cholinergic modulation of CA1 network responses to Schaffer collateral input. By comparing responses recorded with optical imaging and field recordings across the proximodistal axis of CA1, it was initially demonstrated that voltage-sensitive dyes could report reliably both the pattern of activation and cholinergic modulation. The higher spatial resolution of optical imaging was used to explore the somatodendritic profile of cholinergic modulation. It was found that activation of muscarinic acetylcholine receptors (mAChR) (1-10 microM carbachol), inhibited evoked responses across all layers of CA1. This was accompanied by an increase in paired-pulse facilitation in the apical and distal dendritic layers (40 ms inter-stimulus interval), but not in perisomatic regions. The mAChR antagonist, 20 microM atropine, alone increased facilitation at perisomatic sites, suggesting that muscarinic signalling pathways actively suppress perisomatic responses to repetitive stimulation. In contrast, the activation of nicotinic acetylcholine receptors (10 microM nicotine) had no significant effect on single evoked responses, but selectively increased facilitation at perisomatic sites. These results suggest that cholinergic modulation of the hippocampal CA1 network has multiple differential effects on the somatodendritic processing of the Schaffer collateral input.

Acetylcholine↗
PubMed2004

Towards a standard analysis for functional near-infrared imaging.

Functional near-infrared spectroscopy (fNIRS) allows the ability to monitor brain activation by measuring changes in the concentration of oxy- and deoxy-hemoglobin. Until now no standardized approach for fNIRS data analysis has been established, although this has to be regarded as a precondition for future application. Hence, we applied the well-established general linear model to optical imaging data. Further, fNIRS data were analyzed in the frequency domain. Two visual tasks were investigated with optical imaging: a checkerboard paradigm supposed to activate the primary and secondary visual cortex, and a paradigm consisting of moving colored stimuli (rotating 'L's) additionally involving the motion area V5. Analysis with the general linear model detected the activation focus in the primary and secondary visual cortex during the first paradigm. For the second paradigm, a second laterally localized activated brain region was found, most likely representing V5. Spatially resolved spectral analysis confirmed the results by showing maxima of power spectral density and coherence in the same respective brain regions. Moreover, it demonstrated a delay of the hemodynamic response in the motion area. In summary, the present study suggests that the general linear model and spatially resolved spectral analysis can be used as standard statistical approaches for optical imaging data, particularly because they are almost independent of the assumed differential path length factors.

Adult↗
PubMed2005

Three-dimensional visualization of protein expression in mouse brain structures using imaging mass spectrometry.

We have developed a method to visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions. Details of the methodology are exemplified using the 3-D reconstruction of myelin basic protein (MBP) in the corpus callosum of a mouse brain. In this procedure, optical images obtained from serial coronal sections are first aligned to each other to reconstruct a surface of the corpus callosum from segmented contours of the aligned images. The MALDI IMS data are then coregistered to the optical images and superimposed into the surface to create the final 3-D visualization. Correlating proteomic data with anatomical structures provides a more comprehensive understanding of healthy and pathological brain functions, and holds promise to be utilized in more complex anatomical arrangements.

Animals↗
PubMed1999

CCD imaging for optical tomography of gel radiation dosimeters.

Several investigations have been carried out by a number of researchers over the past few years to evaluate the utility of imaging gel dosimeters for the three-dimensional measurement of radiation fields. These have been proposed to be of particular value in mapping radiation dose distributions associated with emerging and complex approaches to cancer treatment such as conformal (CRT), intensity modulated (IMRT), "gamma knife," and pencil beam radiotherapies. Imaging of the gels has been successfully accomplished with clinical MRI units and via laser-based optical scanning. However, neither of these methods is generally accessible to all potential users, limiting the broader study and implementation of this valuable tool. We report here the design, methodology, and results of a preliminary study carried out to evaluate the utility of a new, inexpensive, and simplified approach to tomographic imaging of gel radiation dosimeters. For the purpose of this initial investigation, an array of liquid scintillation vials was prepared, containing a ferrous sulphate xylenol orange (FSX) gelatin formulation. The FSX formulation undergoes a change in optical absorption characteristics following irradiation, and the resulting color change can be observed visually. The vials were irradiated individually to different doses. Three-dimensional imaging was accomplished by tomographic reconstruction from two-dimensional optical images acquired using a diffuse, fluorescent light source, a digital charge-coupled device camera, single-photon-emission-computed tomography software, and other simple components designed by the authors. The resulting transverse images were evaluated through a region-of-interest (ROI) analysis to obtain the average change in image density in each vial as a function of radiation dose. These measured ROI values were subjected to a linear regression analysis to fit them to a straight line, and to determine the goodness of fit. Results from multiple imaging trials are compared. The correlation coefficients obtained are typically on the order of 0.98, and the p value from analysis of variance is approximately 0.05, indicating a linear and reproducible response for the dosimeter formulation and imaging system.

Dose-Response Relationship, Radiation↗
PubMed1994

Mapping patterns of neuronal activity and seizure propagation by imaging intrinsic optical signals in the isolated whole brain of the guinea-pig.

Image analysis techniques were used to examine changes in the intrinsic optical properties in the isolated brain of the guinea-pig in order to map normal neuronal activity patterns and seizure propagation in the olfactory cortex. Electrical stimulation of the lateral olfactory tract decreased light reflectance in distant cortical areas where fibres of the tract are known to project. These areas included the amygdalar, anterior and posterior piriform, and entorhinal cortices, as well as the olfactory tubercle. Stimulation of the lateral entorhinal cortex decreased reflectance in a more circumscribed area in the lateral and medial entorhinal cortex. By imaging intrinsic signals in real-time, we also demonstrated that seizure activity elicited in the entorhinal cortex/hippocampus preferentially propagated to the posteromedial cortical amygdaloid nucleus. The magnitudes of the intrinsic optical signals were correlated with the amplitudes of field potentials recorded in laminae II or III of the olfactory cortex of the same preparations. These signals had onset times of approximately 3 s during 5 Hz stimulation, consistently recovered and were graded with stimulation frequency. The generation of the intrinsic signals required postsynaptic activation, since attenuating synaptic transmission with kynurenic acid (an excitatory amino acid antagonist) eliminated the signals. The intrinsic signals exhibited maxima at 425-450, 550 and 600 nm, suggesting that they arose from changes in light absorption by cytochromes. Intrinsic signals of relatively constant magnitude were also present at 400, 475-500 and 575 nm, and at wavelengths greater than 600 nm. This suggested that an additional component of the intrinsic signal arose from changes in light scattering, possibly due to cellular swelling.

Animals↗
PubMed2005

Spatial deconvolution technique to improve the accuracy of reconstructed three-dimensional diffuse optical tomographic images.

A straightforward spatial deconvolution operation is presented that seeks to invert the information-blurring property of first-order perturbation algorithms for diffuse optical tomography (DOT) image reconstruction. The method that was developed to generate these deconvolving operators, or filters, was conceptually based on the frequency-encoding process used in magnetic resonance imaging. The computation of an image-correcting filter involves the solution of a large system of linear equations, in which known true distributions and the corresponding recovered distributions are compared. Conversely, application of a filter involves only a simple matrix multiplication. Simulation results show that application of this deconvolution operation to three-dimensional DOT images reconstructed by the solution of a first-order perturbation equation (Born approximation) can yield marked enhancement of image quality. In the examples considered, use of image-correcting filters produces obvious improvements in image quality, in terms of both location and mirco(a) of the inclusions. The displacements between the true and recovered locations of an inclusion's centroid location are as small as 1 mm, in an 8-cm-diameter medium with 1.5-cm-diameter inclusions, and the peak value of the recovered micro(a) for the inclusions deviates from the true value by as little as 5%.

Algorithms↗