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At least 1,315 records · Page 73Linked to original sources
PubMed2004

Efficient electrospray ionization from polymer microchannels using integrated hydrophobic membranes.

A simple process for realizing stable and reliable electrospray ionization (ESI) tips in polymer microfluidic systems is described. The process is based on the addition of a thin hydrophobic membrane at the microchannel exit to constrain lateral dispersion of the Taylor cone formed during ESI. Using this approach, ESI chips are shown to exhibit well-defined Taylor cones at flow rates as low as 80 nL min(-1) through optical imaging. Furthermore, stable electrospray current has been measured for flow rates as low as 10 nL min(-1) over several hours of continuous operation. Characterization of the electrospray process by optical and electrical monitoring of fabricated ESI chips is reported, together with mass spectrometry validation using myoglobin as a model protein. The novel process offers the potential for low-cost, direct interfacing of disposable polymer microfluidic separation platforms to mass spectrometry.

Membrane Proteins↗
PubMed2003

Visualization of modulatory effects of serotonin in the silkmoth antennal lobe.

A unique serotonin-immunoreactive neuron innervates every glomerulus of the contralateral antennal lobe (AL), the primary olfactory center, of the male silkmoth Bombyx mori. In order to examine the possible modulatory effects of serotonin in the AL, we utilized high-speed optical imaging with a voltage-sensitive dye combined with bath application of serotonin. We found that serotonin at 10(-4)mol l(-1) caused significant and reversible increases in the optical responses in both the macroglomerular complex (MGC) and the ordinary glomeruli (Gs) evoked by electrical stimulation of the antennal nerve. Optical responses in both the MGC and Gs were also significantly longer lasting following serotonin application. Serotonin exerted a significantly greater enhancing effect in the toroid glomerulus of the MGC than in the cumulus, and the effects of serotonin were also non-homogeneously distributed in the Gs. Our results are evidence that serotonin acts in both the MGC and Gs to modulate the responses of neuronal populations.

Animals↗
PubMed2004

Functional segregation of plural regions representing cardinal contours in cat primary visual cortex.

Our previous data based on an imaging study suggested that, in cat area 17, the representations of cardinal orientations overlap less than the representation of their nearby angles. The purpose of this study was to further investigate the underlying single-cell properties. Optical imaging was performed first to map the cortical regions corresponding to the four principal contours, the two cardinals and the two obliques. The cortical region activated by a principal orientation but not by the +10 degrees or -10 degrees neighbouring angles, namely the area with optically relative independent orientation selectivity (RIOS), was mapped together with the regions that overlapped with the +10 degrees and/or -10 degrees neighbouring angles (non-RIOS). Electrode penetrations were targeted to the RIOS and non-RIOS regions in each of the four orientations. A comparison between the RIOS and the non-RIOS regions documented a significantly higher percentage of cells with the orientation preference of the cardinal orientations in the cardinal RIOS region than that seen in the other regions. Additionally, the difference in the tuning width of cells between the RIOS and non-RIOS in the cardinal region was significantly larger than the difference between the RIOS and non-RIOS in the oblique region. The cells in the cardinal RIOS region were tuned more sharply and the cells in cardinal non-RIOS region more broadly than the oblique RIOS and/or the non-RIOS region, which showed no significant difference. These data strongly suggest the existence of functional segregation in the region corresponding to the cardinal contours.

Animals↗
PubMed2006

Histologic correlation of in vivo optical coherence tomography images of the human retina.

PURPOSE: To correlate in vivo human retina optical coherence tomography (OCT)3 images with histology. DESIGN: Case series. METHODS: Linear OCT3 scans through the macula and optic nerve were obtained in three eyes of three patients who then underwent exenteration surgery for orbital cancers. OCT3 images were then correlated with histology. RESULTS: On histology, two eyes were normal, and one eye had dry macular degeneration. The plexiform layers on histology correlated with the green/yellow areas on the OCT3 scans, and the nuclear layers correlated with the black areas on the OCT3 scans. CONCLUSIONS: The authors are unaware of previous reports correlating histology to in vivo human retina OCT3 images. Our findings using human eyes are not different from previous animal studies, in that the plexiform layers are optically highly backscattering and the nuclear layers are not.

Aged↗
PubMed2000

Multiple-site optical recording of mouse brainstem evoked by vestibulocochlear nerve stimulation.

We used optical imaging to investigate the mouse cochlear and vestibular nucleus in brainstem slices using a voltage-sensitive dye, RH 155. As a result, the spatiotemporal patterns of excitatory propagation were shown. These optical signals consisted of two components consisting of a spike-like fast signal and a long-lasting slow signal. All responses were abolished by tetrodotoxin. The slow signals were eliminated under a Ca(2+)-free solution. In addition, synaptic fatigue was also observed. The present study indicated the feasibility of optical recording for visually revealing the synaptic transmission in both the vestibular and cochlear nucleus.

Animals↗
PubMed2006

[Application of molecular imaging to chemotherapy].

Molecular imaging is a new subject of exploring the biological metabolism process of the cells or organs in living organisms with some non-invasive technologies, such as PETE-CT, MR, and optical imaging instruments, using specific molecular probes to investigate the pathologic and physiologic metabolisms of the patients at molecular and gene levels. With the development of this technology, molecular imaging plays a more and more important role in guiding cancer chemotherapy, choosing sensitive medicines, planning treatment scheme, evaluating chemotherapy effect, and so on.

Antineoplastic Agents↗
PubMed2005

In vivo optical coherence tomography imaging of the pancreatic and biliary ductal system.

BACKGROUND: In vivo optical coherence tomography (OCT) imaging has not yet been applied to the pancreatic ductal system. The aim of this study was to obtain in vivo OCT images of dog pancreatic and biliary ducts, and to correlate the images with histology. METHODS: Images of dog pancreatic and biliary ducts were obtained by using an in vivo OCT probe introduced through the respective papillary orifices. Each duct was imaged in multiple locations, and the site of imaging was marked with injected India ink. After imaging, the dogs were euthanized, and the pancreaticobiliary system was harvested. Histologic cross sections were correlated with in vivo OCT images by measuring the structures seen on in vivo OCT images and correlating them with structures seen on corresponding histology slides that contained India ink. OBSERVATIONS: Eighteen pairs of in vivo OCT images and histology slides from the bile duct and the pancreatic duct were obtained from 5 dogs. The entire duct wall could be visualized. A low reflective in vivo OCT layer corresponding to the epithelium could be discerned on many images. The bile duct showed a more complex architecture and had greater variations within the reflective OCT layers, possibly because of greater cellularity within the lamina propria. Nuclei within cells could not be identified, and structures adjacent to the ducts could not be imaged. CONCLUSIONS: In vivo OCT is capable of imaging the pancreaticobiliary ductal system and of identifying the epithelial layer. Because of limited depth of imaging (320-845 micron), OCT is unlikely to serve the purpose of tumor staging.

Animals↗
PubMed1995

Clinical use of a digital simulator for rapid setup verification in high dose rate brachytherapy.

PURPOSE: Fractionated high dose rate (HDR) brachytherapy provides a number of technical advantages over conventional implant therapy in that (a) it can be carried out on an outpatient basis, (b) personnel exposure is reduced to insignificant levels, and (c) patient motion during irradiation is minimized, resulting in a more accurate delivery of the planned radiation dose distribution to the target and critical structures. The patient discomfort associated with the repeated applicator insertions and/or treatment setups can be alleviated to the extent that the setup time is held to a minimum. This work describes the use of a prototype digital simulator to obtain fast, high-quality digital images for rapid setup verification. METHODS AND MATERIALS: The digital imaging system of the prototype simulator consists of a charge-coupled device (CCD) camera, which views the x-ray image optically transmitted from a conventional phosphor screen. Treatment is carried out with a remote afterloading HDR unit immediately after setup verification with the patient on the simulator stretcher. The high-resolution digital images are processed and displayed in about 5 s, as opposed to a minimum of approximately 2 min for film. RESULTS: The imaging system has been evaluated for a variety of implant types, both intracavitary and interstitial. The digital radiographs provided permanent high-resolution images as required in most cases for precise applicator positioning. The gray scale manipulation capabilities were found to be useful for imaging in regions of different density, such as lung and soft tissue, in the same radiograph. The advantages of short image acquisition and display times were observed in all cases, but were most evident in the intraluminal procedures, which sometimes involved several pretreatment applicator adjustments at a time of considerable patient discomfort. CONCLUSION: Pretreatment imaging is necessary to fully exploit the technical advantages of HDR brachytherapy. High-quality digital radiography offers unique advantages in HDR setup and verification by providing fast high-resolution, undistorted images with software manipulation capabilities and permanent storage of images.

Brachytherapy↗
PubMedDate not supplied

Near-infrared fluorescent nanoparticles as combined MR/optical imaging probes.

A number of quantitative three-dimensional tomographic near-infrared fluorescence imaging techniques have recently been developed and combined with MR imaging to yield highly detailed anatomic and molecular information in living organisms (1, 2). Here we describe magnetic nanoparticle based MR contrast agents that have a near-infrared fluorescence (NIRF) that is activated by certain enzymes. The probes are prepared by conjugation of arginyl peptides to cross-linked iron oxide amine (amino-CLIO), either by a disulfide linkage or a thioether linker, followed by the attachment of the indocyanine dye Cy5.5. The NIRF of disulfide-linked conjugate was activated by DTT, while the NIRF of thioether-linked conjugate was activated by trypsin. Fluorescent quenching of the attached fluorochrome occurs in part due to the interaction with iron oxide, as evident by the activation of fluorescence with DTT when nanoparticles that have less than one dye attached per particle. With a SC injection of the probe, axillary and brachial lymph nodes were darkened on MR images and easily delineated by NIRF imaging. The probes may provide the basis for a new class of so-called smart nanoparticles, capable of pinpointing their position through their magnetic properties, while providing information on their environment by optical imaging techniques.

Animals↗
PubMed2025

MedImg: An Integrated Database for Public Medical Images.

The advancements in deep learning algorithms for medical image analysis have garnered significant attention in recent years. While several studies have shown promising results, with models achieving or even surpassing human performance, translating these advancements into clinical practice is still accompanied by various challenges. A primary obstacle lies in the availability of large-scale, well-characterized datasets for validating the generalization of approaches. To address this challenge, we curated a diverse collection of medical image datasets from multiple public sources, containing 105 datasets and a total of 1,995,671 images. These images span 14 modalities, including X-ray, computed tomography, magnetic resonance imaging, optical coherence tomography, ultrasound, and endoscopy, and originate from 13 organs, such as the lung, brain, eye, and heart. Subsequently, we constructed an online database, MedImg, which incorporates and systematically organizes these medical images to facilitate data accessibility. MedImg serves as an intuitive and open-access platform for facilitating research in deep learning-based medical image analysis, accessible at https://www.cuilab.cn/medimg/.

Humans↗
PubMed1997

Intrinsic optical changes in neuronal tissue. Basic mechanisms.

Associated with changes in the level of physiological activity in neuronal tissue are changes in the intrinsic optical properties of the tissue. As a consequence, it is possible to optically monitor neuronal activity without the use of dyes or other contrast-enhancing agents. Such optical techniques have been applied in the laboratory for more than 50 years. Recent developments in near-infrared spectroscopy and intraoperative optical imaging have suggested a number of clinically important applications of this technology. This article provides an overview of what is known about the physiological correlates and underlying mechanisms associated with activity-evoked optical changes in neuronal tissue.

Brain↗
PubMed2006

Computational studies of optical textures of twist disclination loops in liquid-crystal films by using the finite-difference time-domain method.

Optical images of textured liquid-crystal films containing various types of twist disclination loops are computed using an approximate matrix method and a direct numerical simulation based on the finite-difference time-domain (FDTD) method. The selected defects introduce large multidirectional spatial gradients in the optic axis, mimicking the orientation textures that arise in the construction and use of biosensors based on liquid-crystal vision. It is shown that under these experimentally relevant conditions, the matrix method fails to capture important signatures in the transmitted light intensity under crossed polarizers. The differences between the predictions by the two methods are analyzed with respect to gradients in the optic axis. We show that the FDTD method is a useful tool to perform computational optics of textured liquid-crystal films.

Algorithms↗
PubMed2006

Three dimensional optic disc visualisation from stereo images via dual registration and ocular media optical correction.

BACKGROUND/AIMS: The three dimensional (3-D) visualisation of the optic disc in true colour will give essential meaning in clinical application. It is not only useful for clinicians in the evaluation of the condition of the optic disc, but it also simplifies the pathological diagnosis and disease progression monitoring. This paper describes a complete 3-D optic disc reconstruction method from a pair of stereo images by a series of robust procedures including camera calibration, image registration, depth recovery, and ocular media optical inclusion. METHODS: Two registration techniques (correlation and feature based methods) are combined together to prune the uncertain matching points in order to improve the overall accuracy of registration. The ocular media within the eyeball are lump modelled as a single lens and integrated into the reconstruction process to obtain an accurate 3-D optic disc image. CONCLUSION: The recovered 3-D optic disc images show good consistency and compatibility when compared with the results from Heidelberg retina tomography (HRT) under clinical validation, with an additional advantage of implementing a more economical and conventional mode of retinal image acquisition.

Algorithms↗
PubMed2006

Retinal nerve fiber layer analysis in the diagnosis of glaucoma.

PURPOSE OF REVIEW: The detection of optic disc and retinal nerve fiber layer damage and change is the cornerstone of glaucoma management. Assessment of the retinal nerve fiber layer for localized and diffuse damage has been traditionally based on clinical examination, with documentation of change primarily qualitative. With the latest improvements in optical imaging instruments, objective and quantitative measurements of the retinal nerve fiber layer are now possible. This review summarizes the results from recent cross-sectional studies evaluating the discriminating ability of automated retinal nerve fiber layer measurements to detect glaucoma, and from longitudinal studies assessing the ability to predict and monitor glaucomatous changes. RECENT FINDINGS: Numerous cross-sectional studies have documented good diagnostic accuracy of a scanning laser polarimeter (GDx VCC), the optical coherence tomograph (Stratus), and the Heidelberg Retina Tomograph retinal nerve fiber layer measurements for differentiating between healthy and glaucoma eyes. There are only limited data available on the ability of these retinal nerve fiber layer measurements to document change over time. SUMMARY: It is essential that the clinician understand the specific strengths and weaknesses of each technique so that only good quality retinal nerve fiber layer information will be used in conjunction with careful clinical examination and visual function testing for glaucoma management decisions. Longitudinal studies are needed to evaluate the ability of these instruments to document retinal nerve fiber layer change over time.

Diagnostic Imaging↗
PubMed2006

Identifying intestinal metaplasia at the squamocolumnar junction by using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is an optical imaging method that produces high-resolution cross-sectional images of the esophagus. The accuracy of OCT for differentiating tissue types at the squamocolumnar junction (SCJ) has not been established. OBJECTIVE: The purpose of this study was to identify and validate OCT image criteria for distinguishing metaplastic from nonmetaplastic tissue at the SCJ. DESIGN: A total of 196 biopsy-correlated OCT images of the SCJ were acquired from 113 patients undergoing upper endoscopy. A pathologist blinded to the OCT results reviewed each pathology specimen and determined the presence of the following histopathology: gastric cardia, squamous mucosa, pancreatic metaplasia, and intestinal metaplasia. An algorithm for diagnosing specialized intestinal metaplasia (SIM) was created by reviewing a training set of 40 biopsy-correlated OCT images. Two blinded investigators prospectively tested the algorithm on a validation set of 123 images. RESULTS: OCT images of squamous mucosa were characterized by a layered appearance without epithelial glands; gastric cardia, by vertical pit and gland structure, a well-defined epithelial surface reflectivity, and relatively poor image penetration; and SIM by an irregular architecture and good image penetration. The OCT criteria were 85% sensitive and 95% specific for SIM when applied retrospectively to the training set. When applied to the validation set, the algorithm was 81% sensitive for both OCT readers and 66% and 57% specific for diagnosing SIM. The interobserver agreement was good (kappa = 0.53). CONCLUSIONS: OCT imaging can identify SIM at the SCJ with an accuracy similar to that of endoscopy.

Algorithms↗
PubMed2006

Noninvasive assessment of collagen gel microstructure and mechanics using multiphoton microscopy.

Multiphoton microscopy of collagen hydrogels produces second harmonic generation (SHG) and two-photon fluorescence (TPF) images, which can be used to noninvasively study gel microstructure at depth ( approximately 1 mm). The microstructure is also a primary determinate of the mechanical properties of the gel; thus, we hypothesized that bulk optical properties (i.e., SHG and TPF) could be used to predict bulk mechanical properties of collagen hydrogels. We utilized polymerization temperature (4-37 degrees C) and glutaraldehyde to manipulate collagen hydrogel fiber diameter, space-filling properties, and cross-link density. Multiphoton microscopy and scanning electron microscopy reveal that as polymerization temperature decreases (37-4 degrees C) fiber diameter and pore size increase, whereas hydrogel storage modulus (G', from 23 +/- 3 Pa to 0.28 +/- 0.16 Pa, respectively, mean +/- SE) and mean SHG decrease (minimal change in TPF). In contrast, glutaraldehyde significantly increases the mean TPF signal (without impacting the SHG signal) and the storage modulus (16 +/- 3.5 Pa before to 138 +/- 40 Pa after cross-linking, mean +/- SD). We conclude that SHG and TPF can characterize differential microscopic features of the collagen hydrogel that are strongly correlated with bulk mechanical properties. Thus, optical imaging may be a useful noninvasive tool to assess tissue mechanics.

Biomechanical Phenomena↗
PubMed2003

[Olfactory perception and learning in the honey bee (Apis mellifera): calcium imaging in the antenna lobe].

Honey bees are a key-model in the study of learning and memory, because they show considerable learning abilities, their brain is well described and is accessible to a wide range of physiological recordings and treatments. We use in vivo calcium imaging to study olfactory perception in the bee brain, and combine this method to appetitive olfactory conditioning to unravel the neural substrates of olfactory learning. Odours are detected by receptor neurons on the antennae. Each receptor neuron projects to the first-order neuropile of the olfactory pathway, the antennal lobe, connecting to projection neurons in one of its 160 functional units, the glomeruli. In calcium imaging experiments, each odour elicits a particular activity pattern of antennal lobe glomeruli, according to a code conserved between individuals. The antennal lobe is also a site where the olfactory memory is formed. Using optical imaging, two studies have shown modulations of odour representation in the antennal lobe after learning, with different effects depending on the type of conditioning used. While simple differential conditioning (A + B- training) showed an increased calcium response to the reinforced odour, side-specific conditioning (A + B-/B + A- training) decorrelated the calcium responses of odours between brain sides. This difference may owe to the formation of different memories, which will be addressed in future work. By specifically staining antennal lobe neuronal subpopulations, we hope to be able in the future to study synaptic plasticity in the honey bee.

Animals↗
PubMed2006

Imaging and oncologic drug development.

For decades anatomic imaging with computed tomography or magnetic resonance imaging has facilitated drug development in medical oncology by providing quantifiable and objective evidence of response to cancer therapy. In recent years metabolic imaging with [18F]fluorodeoxyglucose-positron emission tomography has added an important component to the oncologist's armamentarium for earlier detection of response that is now widely used and appreciated. These modalities along with ultrasound and optical imaging (bioluminescence, fluorescence, near-infrared imaging, multispectral imaging) have become used increasingly in preclinical studies in animal models to document the effects of genetic alterations on cancer progression or metastases, the detection of minimal residual disease, and response to various therapeutics including radiation, chemotherapy, or biologic agents. The field of molecular imaging offers potential to deliver a variety of probes that can image noninvasively drug targets, drug distribution, cancer gene expression, cell surface receptor or oncoprotein levels, and biomarker predictors of prognosis, therapeutic response, or failure. Some applications are best suited to accelerate preclinical anticancer drug development, whereas other technologies may be directly transferable to the clinic. Efforts are underway to apply noninvasive in vivo imaging to specific preclinical or clinical problems to accelerate progress in the field. Because resources are limited, and patient suffering from failed or ineffective therapy continues, a concerted effort is being made to address these issues. Many simultaneous activities involving academia; the pharmaceutical, device, and biotechnology industries; US Food and Drug Administration; National Cancer Institute; Centers for Medicare and Medicaid Services; and specialized networks sponsored by the National Institutes of Health are beginning to address these issues to develop consensus recommendations and progress in this important area.

Drug Approval↗