Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Optical imaging”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,261 records · Page 70Linked to original sources
PubMed1985

Cone mosaic observed directly through natural pupil of live vertebrate.

Using a simple ophthalmoscopic technique, the cone mosaic of a live garter snake was clearly visible when viewed directly through its natural pupil, providing the first definitive cone map in a vertebrate eye. The optical MTF was also measured in natural conditions by projecting gratings in the snakes' field of view. Marrying these two results gives, unequivocally, the interrelation of optical image quality and the photoreceptor mosaic.

Animals↗
PubMed1987

Theoretical Fraunhofer light diffraction patterns calculated from three-dimensional sarcomere arrays imaged from isolated cardiac cells at rest.

Sarcomere striation positions have been obtained throughout the volumes of calcium-tolerant resting heart cells by direct computer interfaced high-resolution optical imaging. Each sarcomere position is stored in a three-dimensional (3-D) matrix array from which Fraunhofer light diffraction patterns have been calculated using numerical methods based on Fourier transforms. Diffraction patterns have been calculated from heart cell data arrays oriented normal to a theoretical laser beam. Twelve characteristic features have been identified and described from these diffraction patterns that correlate to diffraction phenomena observed from both cardiac and skeletal muscle. This numerical approach provides the means to directly assess diffraction pattern formulation, the precision of layer line angular separation, layer-line intensity and angular asymmetries, line widths and fine structures in terms of the known diffracting source structures. These results confirm that theoretical calculations can predict real muscle diffraction patterns and their asymmetries.

Animals↗
PubMed2002

PET imaging of gene expression.

Noninvasive in vivo molecular imaging has developed over the past decade and involves nuclear (Positron emission tomography (PET), gamma camera), magnetic resonance, and in vivo optical imaging systems. Most current in vivo molecular imaging strategies are "indirect" and involve the coupling of a "reporter gene" with a complimentary "reporter probe". Imaging the level of probe accumulation provides indirect information related to the level of reporter gene expression. Reporter gene constructs are driven by upstream promoter/enhancer elements; they can be constitutive leading to continuous transcription and used to identify the site of transduction and to monitor the level and duration of gene (vector) activity. Alternatively, they can be inducible leading to controlled gene expression, or they can function as a sensor element to monitor the level of endogenous promoters and transcription factors. Several examples of imaging endogenous biological processes in animals using reporter constructs, radiolabelled probes and PET imaging are reviewed (p53-dependent gene expression and T-cell receptor-dependent activation of T-lymphocytes). Issues related to the translation of non-invasive molecular imaging technology into the clinic are discussed.

Forecasting↗
PubMed2004

Toward development of imaging modalities for islets after transplantation: insights from the National Institutes of Health Workshop on Beta Cell Imaging.

BACKGROUND: Pancreatic islet transplantation can provide insulin independence and near normal glucose control in selected patients with type 1 diabetes mellitus. However, in most cases, achieving insulin independence necessitates the use of at least two donor pancreases per recipient and the rate of insulin independence may decline after transplantation. To better understand the fate of transplanted islets and the relationship between transplanted islet mass, graft function, and overall glucose homeostasis, an accurate and reproducible method of imaging islets in vivo is needed. METHODS: Recent advances in noninvasive imaging techniques such as magnetic resonance imaging, positron emission tomography, and other imaging modalities show great promise as potential tools to monitor islet number, mass, and function in the clinical setting. A recent international workshop, "Imaging the Pancreatic Beta Cell," sponsored by the National Institute of Biomedical Imaging and Bioengineering, the National Institute of Diabetes and Digestive and Kidney Diseases, and the Juvenile Diabetes Research Foundation International focused on these emerging efforts to develop novel ways of imaging pancreatic beta cells in vivo. RESULTS: Potential clinically applicable techniques include the use of directed magnetic resonance contrast agents such as lanthanides (Ln(3+)) and manganese (Mn(2+)) or magnetic resonance imaging probes such as superparamagnetic iron oxide nanoparticles. Potential techniques for positron emission tomography imaging include the use of beta cell-specific antibodies, or pharmacologic agents such as glyburide analogs, or d-mannoheptulose. Optical imaging techniques are also being used to evaluate various aspects of beta cell metabolism including intracellular Ca(2+) flux, glucokinase activity, and insulin granular exocytosis. CONCLUSIONS: The consensus among investigators at the imaging workshop was that an accurate and reproducible in vivo measure of functional islet mass is critically needed to further the strides that have been made in both islet transplantation and diabetes research as a whole. Such measures would potentially allow the assessment of islet engraftment and the early recognition of graft loss, leading to greater improvements in islet graft survival and function.

Diagnostic Imaging↗
PubMedDate not supplied

Permeation peptide conjugates for in vivo molecular imaging applications.

Rapid and efficient delivery of imaging probes to the cell interior using permeation peptides has enabled novel applications in molecular imaging. Membrane permeant peptides based on the HIV-1 Tat basic domain sequence, GRKKRRQRRR, labeled with fluorophores and fluorescent proteins for optical imaging or with appropriate peptide-based motifs or macrocycles to chelate metals, such as technetium for nuclear scintigraphy and gadolinium for magnetic resonance imaging, have been synthesized. In addition, iron oxide complexes have been functionalized with the Tat basic domain peptides for magnetic resonance imaging applications. Herein we review current applications of permeation peptides in molecular imaging and factors influencing permeation peptide internalization. These diagnostic agents show concentrative cell accumulation and rapid kinetics and display cytosolic and focal nuclear accumulation in human cells. Combining methods, dual-labeled permeation peptides incorporating fluorescein maleimide and chelated technetium have allowed for both qualitative and quantitative analysis of cellular uptake. Imaging studies in mice following intravenous administration of prototypic diagnostic permeation peptides show rapid whole-body distribution allowing for various molecular imaging applications. Strategies to develop permeation peptides into molecular imaging probes have included incorporation of targeting motifs such as molecular beacons or protease cleavable domains that enable selective retention, activatable fluorescence, or targeted transduction. These novel permeation peptide conjugates maintain rapid translocation across cell membranes into intracellular compartments and have the potential for targeted in vivo applications in molecular imaging and combination therapy.

Animals↗
PubMed2006

Pentax confocal endomicroscope: a novel imaging device for in vivo histology of the upper and lower gastrointestinal tract.

With advances in endoscopic imaging tools, it is becoming increasingly possible to find, assess and treat numerous gastrointestinal (GI) pathologies at the time of endoscopy. This article focuses on the newly developed Pentax confocal endomicroscope that enables in vivo microscopic imaging of the upper and lower GI tract in histological detail at the time of patient examination without the collection of biopsies. The optical imaging technique has the potential to revolutionize clinical workflows in endoscopy through high-resolution fluorescence imaging of cellular and subcellular detail from the surface and subepithelial layers of the GI mucosa. The device incorporates a full screen, high-resolution charge coupled device as well as a confocal microscope. Preliminary data from blinded clinical studies suggests that the use of this device can increase the diagnostic yield for disease detection in conditions such as ulcerative colitis and Barrett's esophagus, where diagnosis using white light endoscopy is problematic. The early detection and diagnosis of GI abnormalities through the collection of 'optical' biopsies or targeted mucosal excisional biopsies has the potential to improve patient outcomes and enable early therapeutic intervention.

Barrett Esophagus↗
PubMed2004

Fourier phase microscopy for investigation of biological structures and dynamics.

By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda/5500, which is stable over several hours. The results obtained on epithelial and red blood cells demonstrate the potential of this instrument for quantitative investigation of the structure and dynamics associated with biological systems without sample preparation.

Cells, Cultured↗
PubMed2006

Effects of measurement method, wavelength, and source-detector distance on the fast optical signal.

Fast optical signals can be used to study the time course of neuronal activity in localized cortical areas. The first report of such signals [Gratton, G., Corballis, P. M., Cho, E., Fabiani, M., Hood, D., 1995a. Shades of gray matter: Noninvasive optical images of human brain responses during visual stimulation. Psychophysiol, 32, 505-509.] was based on photon delay measures. Subsequently, other laboratories have also measured fast optical signals, but a debate still exists about how these signals are generated and optimally recorded. Here we report data from a visual stimulation paradigm in which different parameters (continuous: DC intensity; modulated: AC intensity and photon delay), wavelengths (shorter and longer than the hemoglobin isosbestic point), and source-detector distances (shorter and longer than 22.5 mm) were used to record fast signals. Results indicate that a localized fast signal (peak latency=80 ms) can be detected with both delay and AC intensity measures in visual cortex, but not with unmodulated DC measures. This is likely due to the fact that differential measures (delay and AC intensity) are less sensitive to superficial noise sources, which heavily influence DC intensity. The fast effect had similar sign at wavelengths shorter and longer than the hemoglobin isosbestic point, consistent with light scattering but not rapid deoxygenation accounts of this phenomenon. Finally, the fast signal was only measured at source-detector distances greater than 22.5 mm, consistent with the intracranial origin of the signal, and providing indications about the minimum distance for recording. These data address some of the open questions in the field and provide indications about the optimal recording methods for fast optical signals.

Adult↗
PubMed2004

Molecular imaging of gene expression in living subjects by spliceosome-mediated RNA trans-splicing.

Spliceosome-mediated RNA trans-splicing (SMaRT) provides an effective means to reprogram mRNAs and the proteins they encode. SMaRT technology has a broad range of applications, including RNA repair and molecular imaging, each governed by the nature of the sequences delivered by the pre-trans-splicing molecule. Here, we show the ability of SMaRT to optically image the expression of an exogenous gene at the level of pre-mRNA splicing in cells and living animals. Because of the modular design of pre-trans-splicing molecules, there is great potential to employ SMaRT to image the expression of any arbitrary gene of interest in living subjects. In this report, we describe a model system that demonstrates the feasibility of imaging gene expression by transsplicing in small animals. This represents a previously undescribed approach to molecular imaging of mRNA levels in living subjects.

Animals↗
PubMed1996

Imaging exocytosis and endocytosis.

From the secretion of neurotransmitters via synaptic vesicles to the expulsion of cellular waste via contractile vacuoles, exocytosis and its sequel, endocytosis, are being explored with a variety of new optical tools. Fluorescent markers, especially styryl dyes such as FM1-43 (which reversibly labels endosomal membranes), have been used to follow exo- and endocytic events in many cell types. Even though the development of new dyes is still largely empirical, some theoretical principles have emerged to guide future dye chemistry. Moreover, advances in optical imaging technology that augment conventional fluorescence microscopy are appearing. For example, interference reflection microscopy (which requires no flurophore) and total internal reflection microscopy have recently been used to observe single exocytic events at the contact point between a glass coverslip and the plasma membrane.

Animals↗
PubMed1995

Stimulus parameters influence characteristics of optical intrinsic signal responses in somatosensory cortex.

Optical imaging of intrinsic signals was performed in the barrel cortex of the rat during whisker deflections of varying frequencies (1 to 20 Hz) and durations (0.1 to 5 s). A dose-response relationship was shown between these stimuli and the characteristics of the optically recorded intrinsic signal response. At constant frequencies, longer stimulus durations increased response magnitude, as defined by mean pixel value in statistically determined regions of interest. At constant durations, higher stimulus frequencies increased response magnitude. Response magnitude was also increased by greater numbers of deflections. When stimulus number was constant, there were no differences in response magnitude, regardless of stimulus frequency and duration. Spatial extent of responses, as defined by number of pixels in regions of interest, did not differ between stimulus frequencies, durations, or numbers. Comparison of the time to reach peak intrinsic signal response after stimulus onset ("time-to-peak") suggested that higher frequencies were associated with faster time-to-peak. Registration of intrinsic signal responses with cytochrome oxidase-stained whisker barrels demonstrated that responses were located over the barrel corresponding to the stimulated whisker. In summary, we have shown that the absolute number of stimuli delivered to the system is, at least for short stimulus periods (< or = 5 s), a determining factor for the magnitude of these responses, whereas stimulus frequency appears to influence time-to-peak response.

Animals↗
PubMed2006

In vivo imaging of the diseased nervous system.

In vivo microscopy is an exciting tool for neurological research because it can reveal how single cells respond to damage of the nervous system. This helps us to understand how diseases unfold and how therapies work. Here, we review the optical imaging techniques used to visualize the different parts of the nervous system, and how they have provided fresh insights into the aetiology and therapeutics of neurological diseases. We focus our discussion on five areas of neuropathology (trauma, degeneration, ischaemia, inflammation and seizures) in which in vivo microscopy has had the greatest impact. We discuss the challenging issues in the field, and argue that the convergence of new optical and non-optical methods will be necessary to overcome these challenges.

Animals↗
PubMed1993

Imaging of hippocampal and neocortical neural activity following intravenous cocaine administration in freely behaving cats.

We examined spatial-temporal patterns of neural activity, as inferred from 700 nm light reflectance, from the dorsal hippocampus and surrounding neocortex in seven freely behaving cats following 1.5, 2.5, 3.5 and 5.0 mg/kg intravenous cocaine administration. Images were acquired using a new technique which gathered reflected light from cortical and subcortical structures. Cardiac and respiratory patterning, collected simultaneously with optical images, revealed increased rates and diminished variation after intravenous cocaine administration. Cocaine increased reflectance correlates of hippocampal neural activity in a dose-dependent fashion over a 120 min period, with a lengthening time-to-peak effect (22-76 min). The largest dose resulted in an initial decrease, followed by the greatest enhancement in neuronal activity. Correlates of neural activation in the neocortex displayed an inverse dose-response curve to that found in the hippocampus; the time-to-peak effect was shorter (6-43 min) and the maximal change was reduced. Regional patches and bands of activation occurred during the period of the cocaine response, and were more pronounced in the hippocampus than the neocortex. Procaine, administered in a similar dose, slightly increased neural activity for 10 min in both the hippocampus and neocortex, and elicited a small increase in respiration. Cocaine induces a pronounced enhancement of neural activation in the neocortex and dorsal hippocampus; the time course of activation in the hippocampus parallels an increased respiratory pattern and outlasts the neocortical response. We speculate that hippocampal activation may be related to the profound respiratory acceleration found in response to cocaine.

Animals↗
PubMedDate not supplied

Postoperative changes over time in size of anterior capsulorrhexis in phacoemulsification/aspiration.

In the present study, we attempted to determine the extent to which an anterior capsulorrhexis carried out during cataract surgery contracts postoperatively. The size of the continuous curvilinear capsulorrhexis (CCC) was measured at the end of surgery and at the final follow-up examination in 52 eyes of 40 patients who underwent phacoemulsification/aspiration and implantation of an intraocular lens (IOL) with 6-mm optics. Images obtained by video during surgery and by slit-lamp microscopy were used to determine the CCC size with reference to the optics of the IOL. The average CCC size was 5.0 mm at the end of surgery; it contracted to 4.4 mm by the final postoperative examination. The contraction of the anterior capsule progressed rapidly in the first 50 days following surgery and then gradually thereafter. The extent of contraction was greater in older patients. The smaller the CCC size immediately after surgery, the more rapidly it contracted. The size of the capsulorrhexis contracted an average of 22% following cataract surgery. The contraction rate tended to be higher in older patients. The results suggest that the capsulorrhexis carried out in cataract surgery for elderly patients should be sufficiently large, but not larger than the optics size of the IOL.

Aged↗
PubMedDate not supplied

Imaging tumor angiogenesis with fluorescent proteins.

We have developed three unique mouse models to image angiogenesis with fluorescent proteins, which are described in this review. First, we have adapted the surgical orthotopic implantation (SOI) model to image angiogenesis of human tumors labeled with green fluorescent protein (GFP) transplanted in nude mice. The nonluminous induced capillaries are clearly visible by contrast against the very bright tumor fluorescence examined either intravitally or by whole-body imaging in real time. Intravital images of an SOI model of human pancreatic tumors expressing GFP visualized angiogenic capillaries at both primary and metastatic sites. Whole-body optical imaging showed that blood vessel density increased linearly over a 20-week period in an SOI model of human breast cancer expressing GFP. Opening a reversible skin-flap in the light path markedly reduces signal attenuation, increasing detection sensitivity many-fold and enabling vessels to be externally visualized in GFP-expressing tumors growing on internal organs. The second model utilizes dual-color fluorescence imaging, effected by using red fluorescent protein (RFP)-expressing tumors growing in GFP-expressing transgenic mice that express GFP in all cells. This dual-color model visualizes with great clarity the details of the tumor-stroma interaction, especially tumor-induced angiogenesis. The GFP-expressing tumor vasculature, both nascent and mature, are readily distinguished interacting with the RFP-expressing tumor cells. Using a spectral imaging system based on liquid crystal tunable filters, we were able to separate individual spectral species on a pixel-by-pixel basis. Such techniques non-invasively visualized the presence of host GFP-expressing vessels within an RFP-labeled orthotopic human breast tumor by real-time whole-body imaging. The third model involves a transgenic mouse in which the regulatory elements of the stem cell marker nestin drive GFP. The nestin-GFP mouse expresses GFP in areas of the brain, hair follicle stem cells, and in a network of blood vessels in the skin interconnecting hair follicles. RFP-expressing tumors transplanted to nestin-GFP mice enable specific visualization of nascent vessels in skin-growing tumors such as melanoma. Thus, fluorescent proteins expressed in vivo offer very high resolution and sensitivity for real-time imaging of angiogenesis.

Animals↗
PubMedDate not supplied

Novel near-infrared cyanine fluorochromes: synthesis, properties, and bioconjugation.

Recently, near-infrared (NIR) fluorescence light has been applied to image various biological events in vivo, because it penetrates tissue more efficiently than light in the visible spectrum. Compounds exhibiting fluorescent properties in the NIR range are key elements for this upcoming optical imaging technology. In this paper, we report the synthesis of four new, water-soluble NIR cyanine fluorochromes which have superior chemical stability and optical properties. Each fluorochrome was designed with a monoreactive carboxyl group for labeling purposes. When multiple fluorochromes were attached to a single macromolecule, fluorescence quenching was observed. On the basis of this property, a novel autoquenched enzyme sensitive NIR fluorescence probe was prepared.

Amides↗
PubMed2006

A reference standard for the measurement of macular oedema.

Macular oedema is associated with several conditions that lead to blindness. Accurate measurement of macular thickness is important in order to follow disease progression and evaluate treatments. Four techniques are examined to determine the best reference standard for the detection and quantification of macular oedema: ultrasound, optical coherence tomography, the retinal thickness analyser, and the scanning laser ophthalmoscope. The three optical techniques have the highest resolution and sensitivity, in particular optical coherence tomography. Ultrasound can be useful where dense opacities preclude optical imaging.

Humans↗
PubMedDate not supplied

Noninvasive imaging and analysis of skin lesions for early detection of cutaneous malignant melanoma.

Knowledge of the depth of invasion and three-dimensional (3D) characteristics of skin lesions is crucial to the early diagnosis and prognosis of malignant melanoma. These parameters are currently available only after biopsy. A clinical prototype of an optical imaging instrument, called a nevoscope, has been developed to noninvasively image skin lesions. The nevoscope provides multiple views of a transilluminated skin lesion. These views provide a three-dimensional perception of the lesion. In addition, image-analysis techniques are applied to these images to quantify various diagnostic parameters, such as 3D geometric features and surface texture and pigmentation characteristics. Clinical trials are under way to evaluate the utility of the nevoscope as a diagnostic tool for early detection of melanoma. The construction of the clinical prototype and the integrated clinical imaging environment are described. The development of iterative reconstruction techniques suitable for nevoscopy data is also described. Experimental reconstructions of a physical tissue-like phantom and an in-vivo lesion are presented. The phantom is recovered effectively. Thus, nevoscopy is of potential diagnostic value.

Absorption↗