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At least 667 records · Page 37Linked to original sources
PubMed2004

Molecular imaging: Bridging the gap between neuroradiology and neurohistology.

Historically, in vivo imaging methods have largely relied on imaging gross anatomy. More recently it has become possible to depict biological processes at the cellular and molecular level. These new research methods use magnetic resonance imaging (MRI), positron emission tomography (PET), near-infrared optical imaging, scintigraphy, and autoradiography in vivo and in vitro. Of primary interest is the development of methods using MRI and PET with which the progress of gene therapy in glioblastoma (herpes simplex virus-thymidine kinase) and Parkinson's disease can be monitored and graphically displayed. The distribution of serotonin receptors in the human brain and the duration of serotonin-receptor antagonist binding can be assessed by PET. With PET, it is possible to localize neurofibrillary tangles (NFTs) and beta-amyloid senile plaques (APs) in the brains of living Alzheimer disease (AD) patients. MR tracking of transplanted oligodendrocyte progenitors is feasible for determining the extent of remyelinization in myelin-deficient rats. Stroke therapy in adult rats with subventricular zone cells can be monitored by MRI. Transgene expression (beta-galactosidase, tyrosinase, engineered transferrin receptor) can also be visualized using MRI. Macrophages can be marked with certain iron-containing contrast agents which, through accumulation at the margins of glioblastomas, ameliorate the visual demarcation in MRI. The use of near-infrared optical imaging techniques to visualize matrix-metalloproteinases and cathepsin B can improve the assessment of tumor aggressiveness and angiogenesis-inhibitory therapy. Apoptosis could be detected using near-infrared optical imaging representation of caspase 3 activity and annexin B. This review demonstrates the need for neurohistological research if further progress is to be made in the emerging but burgeoning field of molecular imaging.

Animals↗
PubMed1991

Pattern visually evoked cortical potential and magnetic resonance imaging in optic neuritis.

We studied the extent of optic nerve lesion with magnetic resonance imaging (MRI) in 24 patients with optic neuritis and compared it with visually evoked cortical potentials (VECP). Patients were divided into acute and chronic stage groups according to the duration of the disease from its onset. The short TI inversion recovery (STIR) mode of the MRI was selected for study. In the acute stage group, abnormally high signals of optic nerve on MRI were demonstrated in 11 of 12 eyes, and the amplitude and peak latency of pattern VECP were unrelated to the extent of the optic nerve lesion visualized by MRI. Conversely, in the chronic stage group, the abnormal MRI findings were exhibited in 19 of 23 eyes, and the relationship between the measurements was statistically significant. This difference in the optic nerve lesion observed by MRI between the acute stage and the chronic stage of optic neuritis may indicate pathophysiologic differences in their origins.

Acute Disease↗
PubMedDate not supplied

A novel approach to a bifunctional photosensitizer for tumor imaging and phototherapy.

Optical imaging has attracted a great attention for studying molecular recognitions because minute fluorescent tracers can be detected in homogeneous and heterogeneous media with existing laboratory instruments. In our preliminary study, a clinically relevant photosensitizer (HPPH, a chlorophyll-a analog) was linked with a cyanine dye (with required photophysical characteristics but limited tumor selectivity), and the resulting conjugate was found to be an efficient tumor imaging (fluorescence imaging) and photosensitizing agent. Compared to HPPH, the presence of the cyanine dye moiety in the conjugate produced a significantly higher uptake in tumor than skin. At a therapeutic/imaging dose, the conjugate did not show any significant skin phototoxicity, a major drawback associated with most of the porphyrin-based photosensitizers. These results suggest that tumor-avid porphyrin-based compounds can be used as "vehicles" to deliver the desired fluorescent agent(s) to tumor. The development of tumor imaging or improved photodynamic therapy agent(s) by itself represents an important step, but a dual function agent (fluorescence imaging and photodynamic therapy) provides the potential for tumor detection and targeted photodynamic therapy, combining two modalities into a single cost-effective "see and treat" approach.

Animals↗
PubMed2006

Dual optical and nuclear imaging in human melanoma xenografts using a single targeted imaging probe.

INTRODUCTION: Dual-labeled imaging agents that allow both nuclear and optical imaging after a single injection would be advantageous in certain applications. In this study, we synthesized and characterized a dual-labeled RGD (Arg-Gly-Asp) peptide and compared nuclear and optical images obtained with this agent. METHODS: 111In-DTPA-Lys(IRDye800)-c(KRGDf) composed of both the 111In chelator diethylenetriaminepentaacetic acid (DTPA) and the near-infrared (NIR) fluorescent dye IRDye800 (excitation/emission, 765/792 nm) was synthesized. The probe was characterized with regard to in vitro biological activity and in vivo pharmacokinetics and the ability to target integrin alphavbeta3. Tumors of mice injected with the dual-labeled probe were imaged both by gamma scintigraphy and NIR fluorescence optical camera. RESULTS: DTPA-Lys(IRDye800)-c(KRGDf), DTPA-Lys-c(KRGDf) and c(KRGDf) inhibited the adhesion of melanoma M21 cells to vitronectin-coated surface with the similar biological activity. Both 111In-DTPA-Lys(IRDye800)-c(KRGDf) and 111In-DTPA-Lys-c(KRGDf) had significantly higher uptakes in alphavbeta3-positive M21 melanoma than in alphavbeta3-negative M21-L melanoma at 4-48 h after their injection. Side-by-side comparison of images obtained using 111In-DTPA-Lys(IRDye800)-c(KRGDf) revealed that in living mice, both optical imaging and gamma scintigraphy enabled noninvasive detection of the bound probe to alphavbeta3-positive tumors, with optical images providing improved resolution and sensitive detection of the superficial lesions and gamma images providing sensitive detection of deeper structures. CONCLUSION: The dual-labeled imaging probe 111In-DTPA-Lys(IRDye800)-c(KRGDf) was found to specifically bind to alphavbeta3 in melanoma tumor cells. Employing both nuclear and optical imaging with a single imaging probe may facilitate translation of NIR fluorescence optical imaging into clinical applications.

Animals↗
PubMed1998

Fibre optic confocal imaging (FOCI) of keratinocytes, blood vessels and nerves in hairless mouse skin in vivo.

Fibre optic confocal imaging (FOCI) enabled subsurface fluorescence microscopy of the skin of hairless mice in vivo. Application of acridine orange enabled imaging of the layers of the epidermis. The corneocytes of the stratum corneum, the keratinocytes in the basal layers and redundant hair follicles were visualised at depths greater than 100 microm. Cellular and nuclear membranes of keratinocytes of the skin were visualised by the use of acridine orange and DIOC5(3). Imaging of the skin after injection of FITC-dextran revealed an extensive network of blood vessels with a size range up to 20 microm. Blood cells could be seen moving through dermal vessels and the blood circulation through the dermal vascular bed was video-taped. The fluorescent dye 4-di-2-ASP showed the presence of nerves fibres around the hair follicles and subsurface blood vessels. Comparison was made between images obtained in vivo using FOCI and in vitro scanning electron microscopy and conventional histology. FOCI offers the potential to study dynamic events in vivo, such as blood flow, skin growth, nerve regeneration and many pathological processes, in ways which have not previously been possible.

Administration, Topical↗
PubMed2004

A comparison of cup-to-disc ratio measurement in normal subjects using optical coherence tomography image analysis of the optic nerve head and stereo fundus biomicroscopy.

PURPOSE: To determine the relationships between morphometric optic nerve head (ONH) characteristics defined using optical coherence tomography (OCT) and clinical judgments of cup-to-disc (CD) ratios. METHODS: CD ratios were estimated in 20 subjects by two experienced clinicians using stereo fundus biomicroscopy. Sagittal OCT images were obtained in positions defined by clinicians corresponding to the location of their horizontal and vertical CD ratio estimates. To estimate CD ratios using the OCT images, disc width was defined as the separation of the terminations of the retinal pigment epithelium on each side of the image. OCT cup widths were determined using two criteria: the first measured the separation of cup walls halfway down each side and the second estimated the separation 1/3 down each side. Cups that were less than 150 microm deep were defined as flat for the OCT images. Data were analysed using mean and standard deviation of the differences between clinical estimates and imaging techniques as well as using intraclass correlations (ICC). RESULTS: Between techniques, the range of ICCs for the 1/2 depth criterion was 0.74-0.90 and for the 1/3 criterion was 0.59-0.81. The limits of agreement for the 1/2 criterion were also better than the 1/3 criterion. CONCLUSION: Accurate measures of CD ratio may be derived from OCT ONH images. Estimates of clinical CD ratios in normal subjects appear to be made using depth judgments closer to 1/2 of the way down the cup than 1/3.

Adult↗
PubMed2002

High-resolution imaging of living retina through optic adaptive retinal imaging system.

PURPOSE: To evaluate the possibility as well as the usage of adaptive optics in high-resolution retinal imaging. METHODS: From March to November 2001, the fundus of 25 adults were checked by using Optic Adaptive Retinal Imaging System (OAS). The age of the subjects varied from 18 - 48 years. All had normal visual acuity from 0.9 to 1.0. No abnormality was found in the ocular examination, and their medical as well as ocular history was unremarkable. RESULTS: High-resolution images of the retinal cells, photoreceptor and bipolar cell, were analysed. In these images, the cells are clearly resolved. The density of the photoreceptor at area 1.5 degree from the foveloa is around 40 000 - 50 000/mm2. At area 3 degree, it drops to less than 30 000/mm2. CONCLUSION: Optic Adaptive Retinal Imaging System (AOS) is able to get high-resolution image of retinal cells in living human eyes. It may be widely used in ophthalmology experimentally and clinically.

Adolescent↗
PubMed1996

Imaging congenital optic disc pits and associated maculopathy using optical coherence tomography.

OBJECTIVE: To elucidate the anatomy of congenital optic disc pits with and without maculopathy using optical coherence tomography. SETTING: All patient were examined, photographed, and scanned at the New York Eye and Ear Infirmary. PATIENTS: Ten eyes of eight consecutive patients with congenital optic disc pits were studied. Three eyes had associated serous macular detachment (group 1), four had evidence of resolved detachment (group 2), and three had no clinical macular pathologic lesion (group 3). METHODS: Optical coherence tomography, a new, noninvasive, noncontact, imaging technology capable of producing cross-sectional images of the retina in vivo with high resolution ( < 17 microns) was used to obtain multiple cross-sectional images of the pit, peripapillary retina, and macula. Ophthalmologic examination and standard fundus photography were performed on all eyes. Fluorescein angiography was performed in eyes that had associated macular detachment. RESULTS: Communication between a schisis cavity or subretinal space and the optic nerve pit was imaged in all eyes in group 1. No such communication could be identified in groups 2 and 3. Cystic degeneration and schisis were imaged in the peripapillary retina, macula, or both in all eyes of groups 1 and 2 and in one patient in group 3. A direct communication between the subretinal space and vitreous cavity could not be identified in any eye. CONCLUSIONS: Schisis formation plays an integral role in the development of serous retinal detachment in the presence of congenital optic disc pits. Our findings are consistent with the theory that the optic disc pit acts as a conduit for fluid flow between the schisis cavity or subretinal space and the subarachnoid space.

Adult↗
PubMed1998

Temporal modulation of spatial borders in rat barrel cortex.

We examined the effects of varying vibrissa stimulation frequency on intrinsic signal and neuronal responses in rat barrel cortex. Optical imaging of intrinsic signals demonstrated that the region of cortex activated by deflection of a single vibrissa at 1 Hz is more diffuse and more widespread than the territory activated at 5 or 10 Hz. With the use of two different paradigms, constant time of stimulation and constant number of vibrissa deflections, we showed that the optically imaged spread of activity is more discrete at higher stimulation frequencies. We combined optical imaging with multiple electrode recording and confirmed that the neuronal response to individual vibrissa stimulation at the optically imaged center of activity is greater than the response away from the imaged center. Consistent with the imaging data, these recordings also showed no response to a second vibrissa deflection at 5 Hz at a peripheral recording site, though there was a significant response to a second vibrissa deflection at 1 Hz at the same peripheral site. These findings demonstrate that vibrissa stimulation at higher frequencies leads to more focused physiological responses in cortex. Thus the spread of activation in rat barrel cortex is modulated in a dynamic fashion by the frequency of vibrissa stimulation.

Animals↗
PubMed1997

Optic neuritis: imaging with magnetization transfer.

OBJECTIVE: Our objective was to prospectively examine the optic nerves in patients with clinically severe unilateral optic neuritis, using routine spin-echo and magnetization transfer MR imaging. SUBJECTS AND METHODS: For 39 patients with such lesions, we calculated the magnetization transfer ratio along the involved intraorbital optic nerve and along the asymptomatic contralateral optic nerve in a mirror-image location. Magnetization transfer ratios were correlated with the imaging findings on routine spin-echo MR imaging. RESULTS: Magnetization transfer ratios were decreased in 33 of the 39 clinically symptomatic optic nerves, including 12 of the 18 clinically symptomatic optic nerves in which no abnormality was seen on routine spin-echo MR images obtained before and after administration of gadopentetate dimeglumine. CONCLUSION: Magnetization transfer imaging reveals intraorbital optic nerve abnormalities in patients with optic neuritis even when such lesions are otherwise occult on routine magnetization transfer imaging.

Adult↗
PubMed2002

Aluminum surface corrosion and the mechanism of inhibitors using pH and metal ion selective imaging fiber bundles.

The localized corrosion behavior of a galvanic aluminum copper couple was investigated by in situ fluorescence imaging with a fiber-optic imaging sensor. Three different, but complementary methods were used for visualizing remote corrosion sites, mapping the topography of the metal surface, and measuring local chemical concentrations of H+, OH-, and Al3+. The first method is based on a pH-sensitive imaging fiber, where the fluorescent dye SNAFL was covalently attached to the fiber's distal end. Fluorescence images were acquired as a function of time at different areas of the galvanic couple. In a second method, the fluorescent dye morin was immobilized on the fiber-optic imaging sensor, which allowed the in situ localization of corrosion processes on pure aluminum to be visualized over time by monitoring the release of Al3+. The development of fluorescence on the aluminum surface defined the areas associated with the anodic dissolution of aluminum. We also investigated the inhibition of corrosion of pure aluminum by CeCl3 and 8-hydroxyquinoline. The decrease in current, the decrease in the number of active sites on the aluminum surface, and the faster surface passivation are all consistent indications that cerium chloride and 8-hydroxyquinoline inhibit corrosion effectively. From the number and extent of corrosion sites and the release of aluminum ions monitored with the fiber, it was shown that 8-hydroxyquinoline is a more effective inhibitor than cerium chloride.

Aluminum↗
PubMed2004

Color Doppler imaging in optic neuritis with multiple sclerosis.

PURPOSE: To evaluate the retrobulbar hemodynamics in eyes with optic neuritis with multiple sclerosis and to compare these values with those of the unaffected fellow eyes and healthy control eyes. METHODS: Thirty-four eyes of 17 patients with unilateral optic neuritis and multiple sclerosis and 16 eyes of 16 normal healthy subjects were recruited from the Departments of Ophthalmology and Neurology. The peak systolic and end-diastolic blood flow velocities and resistivity indices of the ophthalmic artery, posterior ciliary arteries and central retinal artery were measured in each eye with optic neuritis, using color Doppler imaging. Then, they were compared with those of the unaffected fellow eyes and healthy control eyes using paired and unpaired Student's t-tests, respectively. RESULTS: The mean retrobulbar blood flow velocities and mean resistivity index in the ophthalmic artery in the eyes with optic neuritis were not significantly different from the unaffected fellow eyes and healthy control eyes, as well (P>0.05). The mean end-diastolic blood flow velocity in the central retinal artery (P=0.04) was lower and mean resistivity indices in the central retinal (P=0.02) and posterior ciliary arteries (P=0.009) were higher in the eyes with optic neuritis than in the control eyes. In patients with multiple sclerosis, the eyes with optic neuritis had higher resistivity indices in the posterior ciliary (P=0.02) and central retinal arteries (P=0.04) than did the unaffected fellow eyes. The retrobulbar blood flow velocities and resistivity indices of all vessels in the unaffected fellow eyes did not significantly differ from the control eyes (P>0.05). CONCLUSIONS: This study suggests that optic neuritis with multiple sclerosis is associated with impaired retrobulbar hemodynamics, especially in the posterior ciliary and central retinal arteries when compared with the contralateral unaffected eyes as well as healthy control eyes.

Adult↗
PubMed1999

Analysis of dynamic brain imaging data.

Modern imaging techniques for probing brain function, including functional magnetic resonance imaging, intrinsic and extrinsic contrast optical imaging, and magnetoencephalography, generate large data sets with complex content. In this paper we develop appropriate techniques for analysis and visualization of such imaging data to separate the signal from the noise and characterize the signal. The techniques developed fall into the general category of multivariate time series analysis, and in particular we extensively use the multitaper framework of spectral analysis. We develop specific protocols for the analysis of fMRI, optical imaging, and MEG data, and illustrate the techniques by applications to real data sets generated by these imaging modalities. In general, the analysis protocols involve two distinct stages: "noise" characterization and suppression, and "signal" characterization and visualization. An important general conclusion of our study is the utility of a frequency-based representation, with short, moving analysis windows to account for nonstationarity in the data. Of particular note are 1) the development of a decomposition technique (space-frequency singular value decomposition) that is shown to be a useful means of characterizing the image data, and 2) the development of an algorithm, based on multitaper methods, for the removal of approximately periodic physiological artifacts arising from cardiac and respiratory sources.

Brain↗
PubMed2005

Noninvasive assessment of chorioretinal oxygenation changes in experimental carotid occlusion.

PURPOSE: To demonstrate the capability of our optical imaging system to assess oxygenation changes in chorioretinal vasculatures due to experimentally induced carotid occlusion. METHODS: Chorioretinal oxygenation was assessed by projecting a narrow laser line at an angle on the retina after intravenous injection of an oxygen sensitive probe and imaging phosphorescence emission. Optical section phosphorescence imaging was performed in rats, under steady-state conditions and during unilateral occlusion of the common carotid artery. Phosphorescence intensity was measured in the retinal vein, artery, capillaries, and choroid vascular areas. Oxygenation was defined as the inverse of phosphorescence intensity. Oxygenation changes in the four vascular areas were determined relative to initial preocclusion oxygenation values and compared to measured changes under steady-state conditions. RESULTS: Under steady-state conditions, phosphorescence intensity in chorioretinal vasculatures remained constant, displaying a change of < or = 8% over time. At 12 +/- 5 s from initiation of occlusion, oxygenation decreased in the retinal venous, arterial, capillary, and choroidal circulations by -41 +/-19%, -10 +/- 5%, -20 +/- 18%, -10 +/- 5%, respectively (p < or = 0.05; n = 6). At 30 +/- 10 s from initiation of occlusion, oxygenation change in the retinal vein, artery, capillaries, and choroid was -9 +/- 12%, -2 +/- 4%, -11 +/- 21%, -1 +/- 8%, respectively, and not statistically different as compared to steady-state oxygenation changes (p > or = 0.3; n = 6). CONCLUSIONS: Optical section phosphorescence imaging technique can be used to assess intravascular oxygenation changes and may be a valuable tool for studying disease-related oxygen dynamics in the chorioretinal vasculatures.

Animals↗
PubMedDate not supplied

Evaluation of nano-optical probe from scanning near-field optical microscope images.

We studied a nanometre-sized optical probe in a scanning near-field optical microscope. The probe profile is determined by using a knife-edge method and a modulated transfer function evaluation method which uses nanometre-sized line-and-space tungsten patterns (with spaces 1 microm to 50 nm apart) on SiO2 substrates. The aluminium-covered, pipette-pulled fibre probe used here has two optical probes: one with a large diameter (350 nm) and the other with a small diameter (10 nm). The small-diameter probe has an optical intensity approximately 63 times larger than that of the large-diameter probe, but the power is about 1/25 of that of the large probe.

Journal Article↗
PubMed1995

Interlaboratory comparison of autoradiographic DNA profiling measurements. 2. Measurement uncertainty and its propagation.

Identifying the intrinsic sources of measurement uncertainty greatly facilitates control and further optimization of a measurement system. We have developed a model which quantitatively describes the observed interlaboratory variability of autoradiographic DNA band sizing. The model focuses on optical imaging measurements of band position and the calibration techniques used to convert measured band position to reported band size. The imaging component of measurement variability is described as a 0.05-0.2% standard deviation in determining the relative location of sample and calibration bands on a given film image. While developed solely with optical imaging information, the model is consistent with interlaboratory band sizing measurement variability observed with pristine samples. This interlaboratory variability can be modeled as a 0.2-0.4% standard deviation in the relative positions of sample and calibration bands across different electrophoretic gels. Further band sizing protocol standardization among laboratories would thus be expected to achieve at best a 2-fold reduction in interlaboratory band sizing variability.

Autoradiography↗
PubMed2006

Influence of multiple scattering on three-dimensional imaging with optical diffraction tomography.

Optical diffraction tomography is an imaging technique that permits retrieval of the map of permittivity of an object from its scattered far field. Most reconstruction procedures assume that single scattering is dominant so that the scattered far field is linearly linked to the permittivity. In this work, we present a nonlinear inversion method and apply it to complex three-dimensional samples. We show that multiple scattering permits one to obtain a power of resolution beyond the classical limit imposed by the use of propagative incident and diffracted waves. Moreover, we stress that our imaging method is robust with respect to correlated and uncorrelated noise.

Journal Article↗
PubMedDate not supplied

Electro-optic fundus imaging.

Fundus imaging and photography are cornerstones of modern ophthalmic practice. The recent developments in electro-optic and computer imaging technology resulted in many improvements in the acquisition and analysis of fundus images, which already are being used in commercial fundus imaging systems. This paper reviews the basic aspects of the electro-optic methods for fundus imaging, with emphasis on the differences between these new techniques and conventional, film-based, fundus photography. Potential benefits of these systems in image acquisition, archival, communication, processing, and quantitative analysis, as as well as their current advantages and shortcomings are discussed.

Fundus Oculi↗