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 523 records · Page 29Linked to original sources
PubMed2004

Optical imaging of the spatiotemporal dynamics of cerebral blood flow and oxidative metabolism in the rat barrel cortex.

Oxidative metabolism and cerebral blood flow (CBF) are two of the most important measures in neuroimaging. However, results from concurrent imaging of the two with high spatial and temporal resolution have never been published. We used flavoprotein autofluorescence (AF) and laser speckle imaging (LSI) in the anaesthetized rat to map oxidative metabolism and CBF in response to single vibrissa stimulation. Autofluorescence responses reflecting oxidative metabolism demonstrated a fast increase with a delay of 0.1 s. The sign-reversed speckle contrast reflecting CBF started to rise with a delay of 0.6 s and reached its maximum 1.4 s after the stimulation offset. The fractional signal changes were 2.0% in AF and 9.7% in LSI. Pixelwise modelling revealed that CBF maps spread over an area up to 2.5-times larger than metabolic maps. The results provide evidence that the increase in cerebral oxidative metabolism in response to sensory stimulation is considerably faster and more localized than the CBF response. This suggests that future developments in functional imaging concentrating on the metabolic response promise an increased spatial resolution.

Animals↗
PubMed1995

Shades of gray matter: noninvasive optical images of human brain responses during visual stimulation.

Recent theories about human brain function emphasize the need for imaging methods that allow the study of dynamic interactions among different structures. In this paper, we report on a new technique, based on the measurement of parameters of migration of near-infrared photons, that yields functional images of the human occipital cortex, combining a spatial resolution of 0.5 cm and a temporal resolution of 50 ms. This technique appears to be suitable for studying the dynamics of cortical activation.

Adult↗
PubMed2003

Optical imaging of metastatic tumors using a folate-targeted fluorescent probe.

We describe the use of a tumor targeting ligand, the vitamin folic acid, to deliver an attached fluorescent probe to both primary and metastatic tumors overexpressing the folate receptor. Upon laser excitation, derived images of normal tissues generally show little or no fluorescence, whereas images of folate receptor-expressing tumors display bright fluorescence that can be easily distinguished from adjacent normal tissue. Furthermore, metastatic tumor loci of submillimeter size can also be visualized without the aid of image processing or enhancement. The sharp distinction between tumor and normal tissues provided by this technique could find application in the localization and resection of tumor tissue during surgery or in the enhanced endoscopic detection and staging of cancers.

Animals↗
PubMedDate not supplied

High payload delivery of optical imaging and photodynamic therapy agents to tumors using phthalocyanine-reconstituted low-density lipoprotein nanoparticles.

To improve the labeling efficiency of a low-density lipoprotein (LDL)-based photosensitizer (PS) for achieving high probe to protein payload, a tetra-t-butyl silicon phthalocyanine bearing two oleate moieties at its axial positions, SiPcBOA, is designed and synthesized. Using this novel strategy, SiPcBOA reconstituted LDL (r-SiPcBOA-LDL) with a very high payload (SiPcBOA to LDL molar ratio >3000 to 35001:1) is obtained. Using electron microscopy, we find reconstituted LDL (rLDL) with such a high payload essentially retains the mean particle size of native LDL. Since acetylated LDL binds to scavenger receptors of endothelial and microglial cells instead of LDLR, SiPcBOA reconstituted acetylated LDL (r-SiPcBOA-AcLDL) is also prepared to serve as a negative control to validate the LDL receptor (LDLR) targeting specificity. Confocal microscopy studies demonstrate that the internalization of r-SiPcBOA-LDL by human hepatoblastoma G2 (HepG2) tumor cells is mediated by LDLR pathway. The in vitro photodynamic therapy (PDT) response of HepG2 cells to r-SiPcBOA-LDL is compared to SiPcBOA (free drug control) using a clonogenic assay. The slopes of the linear regression fit to the logarithmic data for these two plots are significantly different from each other (p=0.0007), indicating greatly enhanced efficacy of LDLR-targeted PDT.

Cell Line, Tumor↗
PubMed2000

Optical imaging as an adjunct to sonograph in differentiating benign from malignant breast lesions.

The role of near infrared (NIR) diffusive light imaging as an adjunct to ultrasound in differentiating benign from malignant lesions was evaluated in 27 mammography patients with infiltrating ductal carcinomas, apocrine metaplasia, fibroadenomas, radial scar and ductal hyperplasia, cysts, and normal tissues. Conventional ultrasound/mammography images were graded based on BI-RADS assessment categories. The spatial NIR measurements were made at wavelengths of 750 and 830 nm. Functional images, such as relative changes of deoxyhemoglobin (deoxyHb) and total blood concentration, were estimated from the dual wavelength measurements. Maximum relative deoxyHb and blood concentration changes were measured, and spatial correlation of masses in relative deoxyHb and blood concentration images for each breast were calculated. For the five biopsy proven benign lesions, ultrasound/mammography diagnoses were suspicious for malignancy (four cases) and highly suspicious for malignancy (one case). Four lesions showed less than 1.0 V maximum deoxyHb and less than 1.5 V maximum blood concentration levels on average and spatial image correlation showed no correlated masses in both deoxyHb and blood concentration images. For the four biopsy proven malignant lesions, ultrasound/mammography diagnoses were highly suspicious for malignancy. Maximum deoxyHb and blood concentration changes were greater than 2.9 V on average except one lesion which showed smaller deoxyHb signal (maximum 0.85 V) but the deoxyHb mass and blood concentration mass were highly correlated.

Adult↗
PubMedDate not supplied

Evaluating the spatial resolution performance of a time-resolved optical imaging system.

An imaging system is being developed as a possible means of screening for breast cancer using harmless doses of visible or near-infrared radiation. This system produces transmission images of highly scattering objects by recording and discriminating between the times-of-flight of transmitted photons. Experiments have been performed to evaluate the likely spatial resolution performance of such a system. This involved measuring the edge profile produced by an opaque mask embedded in a highly scattering medium, and evaluating the spatial resolution as a function of the period of time over which transmitted light was integrated. The results suggest that a resolution of a few millimeters is achievable with a system with a temporal resolution of about 10 ps.

Breast Neoplasms↗
PubMed2005

Optical imaging of neuronal populations during decision-making.

We investigated decision-making in the leech nervous system by stimulating identical sensory inputs that sometimes elicit crawling and other times swimming. Neuronal populations were monitored with voltage-sensitive dyes after each stimulus. By quantifying the discrimination time of each neuron, we found single neurons that discriminate before the two behaviors are evident. We used principal component analysis and linear discriminant analysis to find populations of neurons that discriminated earlier than any single neuron. The analysis highlighted the neuron cell 208. Hyperpolarizing cell 208 during a stimulus biases the leech to swim; depolarizing it biases the leech to crawl or to delay swimming.

Analysis of Variance↗
PubMed2004

Noninvasive optical imaging method to evaluate postantibiotic effects on biofilm infection in vivo.

Eradication of Staphylococcus aureus biofilms after rifampin treatment was tested in a mouse model of device-related infection by using biophotonic imaging. Following treatment, the bioluminescent signals decreased to undetectable levels, irrespective of the age of the biofilm. After the final treatment, the signals rebounded in a time-dependent manner and reached those for the untreated mice. Readministration of rifampin was unsuccessful in eradicating reestablished infections, with the rifampin MICs for such bacteria being increased and with the bacteria having point mutations in the rpoB gene.

Animals↗
PubMed2005

Functional organization of visual cortex in the prosimian bush baby revealed by optical imaging of intrinsic signals.

Cells in primary visual cortex (V1) of primates and carnivores respond most strongly to a visual stimulus presented to one eye, in a particular visual field location, and at a particular orientation. Each of these stimulus attributes is mapped across the cortical surface, and, in macaque monkeys and cats, strong geometrical relationships exist between these feature maps. In macaque V1 and V2, correlations between feature maps and cytochrome oxidase (CO)-rich modules have also been observed. To see if such relationships reflect a conserved principle of V1 functional architecture among primate species, we examined these maps in the prosimian bush baby, a species that has been proposed to represent the ancestral primate organization. We found that the layout of individual feature maps in bush baby V1 is similar to that of other primates, but we found an entirely different organization of orientation preference in bush baby V2 compared with that reported in simian primates. Another striking distinction between bush baby and simian species is that we observed no strong relationships among maps of orientation, ocular dominance, and CO blobs in V1. Thus our findings suggest that precise relationships between feature maps are not a common element of the functional organization in all primates and that such relationships are not necessary for achieving basic coverage of stimulus feature combinations. In addition, our results suggest that specific relationships between feature maps in V1, and the subdivision of V2 into functional compartments, may have arisen comparatively late in the evolution of primates.

Animals↗
PubMed2004

In vivo optical imaging of pleural space drainage to lymph nodes of prognostic significance.

BACKGROUND: Understanding the spatial and temporal drainage patterns of the pleural space could have profound impact on the treatment of lung cancer and mesothelioma. The purpose of this study was to identify the in vivo pattern of drainage from the pleural space to prognostic lymph node stations. METHODS: Fifty-six rats underwent pleural space injection of a novel lymph tracer composed of recombinant human serum albumin (HSA) covalently conjugated to the near-infrared (NIR) fluorophore IRDye78 via an amide bond (HSA-78). Nodal uptake was imaged at 10, 20, 30, and 60 minutes and 4, 12, and 24 hours after injection with a custom system that simultaneously acquires color video, NIR fluorescence of HSA-78, and a merged picture of the two. Six pigs underwent the same procedure with imaging at 30 minutes, 1 hour, and 24 hours. RESULTS: In both the rat model and the pig model, HSA-78 drained from the pleural space to superior mediastinal lymph nodes first, followed by other intrathoracic and then extrathoracic lymph nodes over the course of 24 hours. CONCLUSION: NIR fluorescence imaging in two species shows that the superior mediastinal lymph nodes are the first to drain the pleural space. Over the course of 24 hours, the pleural space also communicates with other intrathoracic and then extrathoracic lymph nodes. This study also demonstrates an intraoperative method for identifying nodes communicating with the pleural space, with potential utility in the staging and/or resection of lung cancer and mesothelioma.

Animals↗
PubMed2000

Probabilistic regularization in inverse optical imaging.

The problem of object restoration in the case of spatially incoherent illumination is considered. A regularized solution to the inverse problem is obtained through a probabilistic approach, and a numerical algorithm based on the statistical analysis of the noisy data is presented. Particular emphasis is placed on the question of the positivity constraint, which is incorporated into the probabilistically regularized solution by means of a quadratic programming technique. Numerical examples illustrating the main steps of the algorithm are also given.

Journal Article↗
PubMed2000

Aberrations of diffracted wave fields. I. Optical imaging.

The concept of aberrations of diffracted waves is revisited by using the Rayleigh-Sommerfeld theory of diffraction, and it is pointed out that these aberrations are in a class by themselves; they are only deceptively similar to the aberrations of a rotationally symmetric imaging system. Although an exact Fourier-transform expression can be written for the diffracted wave field, its numerical calculation is cumbersome because of the dependence of the aberrations of the diffracted wave on the observation point. This is true regardless of whether the diffracted wave field is observed on a plane or a hemisphere. It is shown that the Fresnel and Fraunhofer approximations, which neglect these aberrations and thereby simplify the calculations, are valid in imaging applications.

Journal Article↗
PubMed2006

Feasibility of diffuse optical imaging with long-lived luminescent probes.

Long-lived near-infrared phosphors with high quantum yields have recently become available, making it possible to image oxygen distributions in tissue in three dimensions. By numerical simulations we demonstrate that, by using phosphorescent probes with appropriate oxygen quenching constants, one can image hypoxic phantoms in scattering media with adequate spatial resolution, employing simple time-gated measurements. The approach developed will guide experimental imaging of phosphorescence lifetime and oxygen pressure in living tissue.

Cell Hypoxia↗