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Results for “Optical imaging”

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At least 73 records · Page 4Linked to original sources
PubMed2001

Digital optical imaging of green fluorescent proteins for tracking vascular gene expression: feasibility study in rabbit and human cell models.

PURPOSE: To investigate the feasibility of using a sensitive digital optical imaging technique to detect green fluorescent protein (GFP) expressed in rabbit vasculature and human arterial smooth muscle cells. MATERIALS AND METHODS: A GFP plasmid was transfected into human arterial smooth muscle cells to obtain a GFP-smooth muscle cell solution. This solution was imaged in cell phantoms by using a prototype digital optical imaging system. For in vivo validation, a GFP-lentivirus vector was transfected during surgery into the carotid arteries of two rabbits, and GFP-targeted vessels were harvested for digital optical imaging ex vivo. RESULTS: Optical imaging of cell phantoms resulted in a spatial resolution of 25 microm/pixel. Fluorescent signals were detected as diffusely distributed bright spots. At ex vivo optical imaging of arterial tissues, the average fluorescent signal was significantly higher (P <.05) in GFP-targeted tissues (mean +/- SD, 9,357.3 absolute units of density +/- 1,001.3) than in control tissues (5,633.7 absolute units of density +/- 985.2). Both fluorescence microscopic and immunohistochemical findings confirmed these differences between GFP-targeted and control vessels. CONCLUSION: The digital optical imaging system was sensitive to GFPs and may potentially provide an in vivo imaging tool to monitor and track vascular gene transfer and expression in experimental investigations.

Animals↗
PubMed1997

Coherent detection techniques in optical imaging of tissues.

To form optical images from the transmitted or reflected light that is multiply scattered inside biological tissue, several detection techniques that extract the least-scattered photons or path-resolved photons have been developed. This paper reviews the coherent detection techniques. Emphasis is put on coherent detection imaging methods based on optical heterodyning, whose attractive features include quantum-noise-limited sensitivity, wide dynamic range, and excellent directionality and selectivity. Coherent detection methods have been implemented to achieve laser computed tomography and micrometre-resolution cross-sectional images in both in vivo and in vitro biological systems. Imaging works by ourselves and others are described, and an experimental study on coherent photon migration through highly scattering media is described to aid the understanding of the coherent detection method in selectively detecting the signal-carrying photons.

Diagnostic Imaging↗
PubMed1993

Optical imaging the "Right" way.

Optical imaging systems can help lead the way to the computer-based patient record. This article addresses several security clearance issues that these systems raise and tells how one facility responded to them.

Computer Security↗
PubMedDate not supplied

Percutaneous optical imaging system to track reporter gene expression from vasculatures in vivo.

This study develops a percutaneous optical imaging system for tracking fluorescent reporter gene expression in vasculatures. We build a percutaneous optical imaging system that primarily comprised a 1.5-mm, semi-rigid, two-port optical probe. The performance of the optical probe is first tested in vitro with cell phantoms, and then the feasibility of the percutaneous optical imaging system is validated in vivo in eight femoral artery segments of two pigs. The green fluorescent protein (GFP) gene is locally delivered into four arterial segments, while saline is delivered to the four contralateral arterial segments as controls. The targeted arteries are localized using color Doppler, and thereafter the optical probe is positioned to the target arterial segments under ultrasound guidance. Optical imaging captures are obtained using different exposure times from 10 to 60 s. Subsequently, the GFP- and saline-targeted arteries are harvested for fluorescent microscopy confirmation. The percutaneous optical probe is successfully positioned at a distance approximately 2 mm from the targets in all eight arteries. The in-vivo imaging shows higher average signal intensity in GFP-treated arteries than in saline-treated arteries. This study demonstrates the potential using the percutaneous optical imaging system to monitor, in vivo, reporter gene expression from vasculatures.

Animals↗
PubMed2006

Quantitative analysis of brain optical images with 2D C0 complexity measure.

Optical imaging based on intrinsic signals is a powerful method to visualize the activities of neural assembly in the cortex of animals in vivo, especially the detailed functional architecture of the visual cortex. Here, a new index, two-dimensional (2D) C0 complexity has been used to give a quantitative measure of the spatial pattern of the neural activity in orientation maps optically recorded from the visual cortex of cats globally. Results show that 2D C0 complexity could be employed to reveal the dynamic process of generating an orientation map in the visual cortex, and describe the variance of the neural responses in cortical area 17 under high and normal intraocular pressure. This suggests that 2D C0 could be used as a new quantitative measure for analyzing the intrinsic signal optical images.

Algorithms↗
PubMed1990

On-line radiotherapy imaging with an array of fiber-optic image reducers.

In the optical approach for on-line radiotherapy imaging, a large metal sheet-fluorescent screen combination is used to convert the radiation intensity distribution into a visible light image. Data are then captured via a mirror with a camera located out of the beam. Although usable portal images can be acquired, presence of the large mirror renders the system impractical in many treatment geometries. We have overcome this limitation by replacing the mirror with an array of 16 by 16 bundles of plastic fiber-optic image reducers. Each bundle, in turn, is made up of 16 by 16 individual optical fibers. The total of 256 by 256 fibers spans an input area of 40 cm by 40 cm with each individual fiber viewing an area of 1.6 mm by 1.6 mm. Within a height of 12 cm, each fiber is reduced to an area of 0.1 mm by 0.1 mm. The reduced portal image is then turned and "piped" to a final 3.0 cm by 3.0 cm output area. For data acquisition and digitization, the fiber output is directly coupled to the sensor of a TV camera interfaced to a small computer via a 512 by 512 frame grabber. In this initial evaluation, the imaging system has been characterized in terms of its line spread function, noise and resistance to radiation damage. Adequate phantom and patient images are presented.

Fiber Optic Technology↗
PubMed2000

Blind signal separation from optical imaging recordings with extended spatial decorrelation.

Optical imaging is the video recording of two-dimensional patterns of changes in light reflectance from cortical tissue evoked by stimulation. We derived a method, extended spatial decorrelation (ESD), that uses second-order statistics in space for separating the intrinsic signals into the stimulus related components and the nonspecific variations. The performance of ESD on model data is compared to independent component analysis algorithms using statistics of fourth and higher order. Robustness against sensor noise is scored. When applied to optical images, ESD separates the stimulus specific signal well from biological noise and artifacts.

Algorithms↗
PubMed2000

Functional neocortical microcircuitry demonstrated with intrinsic signal optical imaging in vitro.

Intrinsic signal optical imaging was used to record the changes in light transmittance evoked by electrical stimulation in slices prepared from sensorimotor cortex of young adult rats. The spatial characteristics of the optical signal evoked by stimulation of layer II/III, IV, V, or VI were clearly different. Layer IV and V stimulation elicited a radially-oriented region of increased light transmittance which was "hourglass" shaped: its tangential extent was greatest in layers II/III and layer V, and least in layer IV. Layer VI stimulation also elicited a radially-oriented signal but the tangential extent of this signal was the same across layers II-VI--that is, it was column-shaped. Upper layer stimulation produced a signal whose tangential extent was much greater in the upper layers than its radial extent to the deeper layers. The spatial form of the stimulus-evoked intrinsic signal was not dependent on the cytoarchitectonic area in which it was elicited. The tangential and radial distribution of the signal evoked by stimulation of different layers appears to reflect the connectivity of cortex, particularly the horizontal connectivity present in layers II/III, V, and VI, and the interlaminar connections that exist between layers II/III and V and from layers VI to IV. The spatial characteristics of the intrinsic signal were independent of the strength of stimulation used. The idea that inhibitory mechanisms restrict the tangential extent of the signal was evaluated in experiments in which the intrinsic signal was recorded before and after the addition of 10 microM bicuculline methiodide. In all slices studied in this way (n = 12), bicuculline methiodide drastically increased the tangential extent of the signal. In 4/12 slices, the tangential spread of the signal was asymmetric with respect to the stimulus site. Asymmetric spread of the signal occurred for both layer V and layer VI stimulation and, in 2/4 of those cases, could be attributed to a cytoarchitectonic border whose presence appeared to restrict the spread of the signal across the border. Although increasing stimulation strength did not change the spatial characteristics of the radially-oriented signal evoked by layer V or VI stimulation, at maximal stimulus intensity the signal evoked from these layers was often accompanied by a band of decreased light transmittance in the most superficial layers (layers I and II). It is concluded that in vitro intrinsic optical signal imaging allows one to image a response attributable to activation of local subsets of cortical connections. In addition, the opposite effects of high-intensity deep layer stimulation on the superficial layers vs layers III-VI of the same column raise the possibility that the most superficial layers may respond differently to repetitive input drive than the rest of the cortical column.

Animals↗
PubMed2003

Optical imaging based on time-resolved Stokes vectors in filamentous tissues.

Time-resolved Stokes vector components of light transmitted through filamentous tissues were measured with a view to improving the imaging quality of optical images in such tissues. Temporal profiles of the Stokes vectors and the time-resolved degree of polarization (DOP) were calibrated to produce higher image quality than that of images based on time gating, polarization discrimination, or both. A thin chicken bone inserted into chicken breast tissue with filament orientation in different directions with respect to the direction of input linear polarization was scanned to demonstrate images of higher spatial resolution and contrast based on the measurement of time-resolved DOP.

Animals↗
PubMed2006

Optical imaging of luminescence for in vivo quantification of gene electrotransfer in mouse muscle and knee.

BACKGROUND: Optical imaging is an attractive non-invasive way to evaluate the expression of a transferred DNA, mainly thanks to its lower cost and ease of realization. In this study optical imaging was evaluated for monitoring and quantification of the mouse knee joint and tibial cranial muscle electrotransfer of a luciferase encoding plasmid. Optical imaging was applied to study the kinetics of luciferase expression in both tissues. RESULTS: The substrate of luciferase (luciferin) was injected either intraperitonealy (i.p.) or in situ into the muscle or the knee joint. Luminescence resulting from the luciferase-luciferin reaction was measured in vivo with a cooled CCD camera and/or in vitro on tissue lysate. Maximal luminescence of the knee joint and muscle after i.p. (2.5 mg) or local injection of luciferin (50 microg in the knee joint, 100 microg in the muscle) were highly correlated. With the local injection procedure adopted, in vivo and in vitro luminescences measured on the same muscles significantly correlated. Luminescence measurements were reproducible and the signal level was proportional to the amount of plasmid injected. In vivo luciferase activity in the electrotransfered knee joint was detected for two weeks. Intramuscular electrotransfer of 0.3 or 3 microg of plasmid led to stable luciferase expression for 62 days, whereas injecting 30 microg of plasmid resulted in a drop of luminescence three weeks after electrotransfer. These decreases were partially associated with the development of an immune response. CONCLUSION: A particular advantage of the i.p. injection of substrate is a widespread distribution at luciferase production sites. We have also highlighted advantages of local injection as a more sensitive detection method with reduced substrate consumption. Besides, this route of injection is relatively free of uncontrolled parameters, such as diffusion to the target organ, crossing of biological barriers and evidencing variations in local enzymatic kinetics, probably related to the reaction medium in the targeted organ. Optical imaging was shown to be a sensitive and relevant technique to quantify variations of luciferase activity in vivo. Further evaluation of the effective amount of luciferase in a given tissue by in vivo optical imaging relies on conditions of the enzymatic reaction and light absorption and presently requires in vitro calibration for each targeted organ.

Animals↗
PubMed2006

Characterizing vascular parameters in hypoxic regions: a combined magnetic resonance and optical imaging study of a human prostate cancer model.

The integration of imaging technologies with the capabilities of genetic engineering has created novel opportunities for understanding and imaging cancer. Here, we have combined vascular magnetic resonance imaging (MRI) and optical imaging to understand the relationship between hypoxia and vascularization in a human prostate cancer model engineered to express enhanced green fluorescent protein (EGFP) under hypoxia. Characterization and validation of EGFP expression under hypoxic conditions was done in culture and in solid tumors in vivo. MRI measurements showed that vascular volume was significantly lower in fluorescing regions. These regions also frequently exhibited high permeability. These data were further supported by the detection of low vessel density in EGFP-positive regions, as determined by the distribution of intravascularly administered, fluorescence-labeled Lycopersicon esculentum lectin in frozen tumor sections. These observations are consistent with the possibility that regions of low vascular volumes are hypoxic, which induces increased expression of functionally active vascular endothelial growth factor, a potent vascular permeability factor.

Animals↗
PubMed1989

Comparison of the unwanted optical images produced by 6 mm and 7 mm intraocular lenses.

Unwanted optical images are noticed by a surprisingly large number of patients following cataract extraction with implantation of posterior chamber intraocular lenses (IOLs). These images are caused by the positioning holes, lens edge, or laser ridge. We studied 550 eyes in which one of seven different IOLs was inserted. The IOLs varied in optic diameter, the presence or absence of positioning holes or a laser ridge, the use of partial depth holes or placement of positioning holes in tabs outside the optical zone. We determined that unwanted optical images could practically be eliminated by using a 7 mm optic without positioning holes. This study also demonstrated that partial depth holes offer no advantage over full thickness holes for reducing unwanted optical images and that positioning holes, even on a 7 mm optic, produce a significant number of complaints.

Equipment Design↗
PubMed2002

Near-infrared optical imaging of the breast with model-based reconstruction.

RATIONALE AND OBJECTIVES: Near-infrared diffuse optical imaging may offer enhanced contrast resolution over that of the existing technologies for detection and diagnosis of breast cancer. The authors report quantitative absorption and scattering images of the human breast with model-based reconstruction methods using near-infrared continuous-wave tomographic data. MATERIALS AND METHODS: An automatic, multichannel optical imaging system was used to image the breasts of nine women: four with infiltrating ductal carcinomas, one with infiltrating lobular carcinoma, one with fibroadenoma, and three control subjects with no breast lesion. The image reconstruction methods are centered on the finite element solution of photon diffusion in breast tissue. RESULTS: Substantial contrast between tumor and adjacent parenchyma was observed. Images of the control subjects showed homogeneous optical features. In the six women with breast lesions, the locations and sizes of tumors imaged optically were accurate and consistent with the mammographic findings. CONCLUSION: The results of this pilot study show that cancers as small as 5 mm can be quantitatively imaged. In addition, preliminary data from the scattering images suggest that benign and malignant tumors can be noninvasively differentiated with optical imaging.

Adenocarcinoma↗
PubMed2003

Hemodynamic evoked response of the sensorimotor cortex measured noninvasively with near-infrared optical imaging.

We have performed a noninvasive bilateral optical imaging study of the hemodynamic evoked response to unilateral finger opposition task, finger tactile, and electrical median nerve stimulation in the human sensorimotor cortex. This optical study shows the hemoglobin-evoked response to voluntary and nonvoluntary stimuli. We performed measurements on 10 healthy volunteers using block paradigms for motor, sensory, and electrical stimulations of the right and left hands separately. We analyzed the spatial/temporal features and the amplitude of the optical signal induced by cerebral activation during these three paradigms. We consistently found an increase (decrease) in the cerebral concentration of oxy-hemoglobin (deoxy-hemoglobin) at the cortical side contralateral to the stimulated side. We observed an optical response to activation that was larger in size and amplitude during voluntary motor task compared to the other two stimulations. The ipsilateral response was consistently smaller than the contralateral response, and even reversed (i.e., a decrease in oxy-hemoglobin, and an increase in deoxy-hemoglobin) in the case of the electrical stimulation. We observed a systemic contribution to the optical signal from the increase in the heart rate increase during stimulation, and we made a first attempt to subtract it from the evoked hemoglobin signal. Our findings based on optical imaging are in agreement with results in the literature obtained with positron emission tomography and functional magnetic resonance imaging.

Adult↗
PubMed1994

Tomographic time-of-flight optical imaging device.

Time-resolved optical imaging has been used to image phantoms, animals, and humans, and offers the potential for the production of functional images of human tissues, such as the oxygenation of brain during stroke. We had previously reported a transmission scanner, and now give an early report on conversion to a rotational tomographic scanner with a non-parallel ray geometry similar to early CAT scanners. Initial scans show that 1) spatial imaging in turbid media using time-of-flight measurements, non-recursive algorithms, and standard tomographic geometry is possible, 2) separation of absorbance and scattering as an image is attainable, a key step in performing spatially-resolved chemometric analysis, 3) imaging of multiple objects buried within scattering material is feasible, demonstrating that equations derived for homogeneous media can be applied in at least some cases to inhomogeneous media such as tissue-like phantoms, and 4) imaging of brain pathology produces recognizable images with sufficient resolution for diagnostic decisions. We conclude that optical tomography is feasible for clinical use and that conversion of the present mechanically scanning device to a clinical scanner should be possible with retention of the current processing algorithms. Such a clinical scanner should ultimately be able to generate images in a few minutes with centimeter resolution at the center of living human brain.

Algorithms↗
PubMed1991

A method to analyze 2-dimensional daily radiotherapy portal images from an on-line fiber-optic imaging system.

On-line radiotherapy imaging systems allow convenient treatment verification and generate a wealth of data. Quantitative analysis of data will provide important information about the nature of treatment variations. Using an inhouse fiber-optic imaging system to acquire daily portal images for five patients, we have developed a method to analyze the cumulative positional variation of blocks in the 2-dimensional images. For each beam arrangement used to treat a particular patient, a reference portal image was established. All other images for that patient were registered with respect to the anatomical landmarks visible on the reference image. Two-dimensional frequency distributions describing the overlap of the blocks during the course of treatment were then calculated and superimposed on the reference image. Results of the analysis show positional and quantitative information about the daily variation in block placement, and appeared to be site-dependent. Long term verification studies using on-line imaging systems will be important in the understanding of treatment uncertainties.

Radiology Information Systems↗
PubMed1996

Enhanced optical imaging of human gliomas and tumor margins.

One of the potential variables affecting the overall survival and quality of life of patients with intracranial gliomas is the extent of tumor resection that results in the smallest volume of residual disease. A technique involving enhanced optical imaging of human gliomas has the potential to localize tumors, identify tumor remaining at the resection margins, and determine the grade of the tumor. In a preliminary study involving nine patients undergoing surgery for the removal of intrinsic brain tumors, enhanced optical imaging was performed using indocyanine green as an intravenous contrast-enhancement agent. Optical images were obtained before and after injection of the indocyanine green. The studies in the nine patients showed differences in the dynamic optical signals among normal brain, low-grade astrocytomas, and malignant astrocytomas. Optical imaging of the resection margins in malignant tumors showed differences between adjacent normal tissue and remaining tumor tissue. Enhanced optical imaging of human gliomas using a contrast-enhancing dye, indocyanine green, provides a potential means to differentiate between normal brain and tumor tissue at the cortical surface and the depths of the resection margins. Having the ability to obtain real-time information and feedback in the operating room may allow neurosurgeons to maximize the extent of tumor resection while sparing normal brain and increasing the diagnostic accuracy of intraoperative biopsies. Enhanced optical imaging potentially could facilitate the accuracy and safety of surgery when tumors are removed at sites even outside the central nervous system.

Adult↗