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PubMed2005

Microinterferometric optical phase tomography for measuring small, asymmetric refractive-index differences in the profiles of optical fibers and fiber devices.

A new technique, microinterferometric optical phase tomography, is introduced for use in measuring small, asymmetric refractive-index differences in the profiles of optical fibers and fiber devices. The method combines microscopy-based fringe-field interferometry with parallel projection-based computed tomography to characterize fiber index profiles. The theory relating interference measurements to the projection set required for tomographic reconstruction is given, and discrete numerical simulations are presented for three test index profiles that establish the technique's ability to characterize fiber with small, asymmetric index differences. An experimental measurement configuration and specific interferometry and tomography practices employed in the technique are discussed.

Journal Article↗
PubMed2000

Flame hydrolysis deposition of glass on silicon for the integration of optical and microfluidic devices

Flame hydrolysis deposition (FHD) of glasses has previously found applications in the telecommunications industry. This paper shows how the technology can be used to deposit silica with different refractive indices and thereby produce low-loss planar waveguides for use in analytical applications. We also show that the glasses can be patterned using a new reactive ion etch and sealed using a modification of anodic bonding, such that the resulting microstructures can be readily incorporated within a lithographically defined "chip", integrating both optical and fluidic circuitry on the same device. In the example described in this paper, waveguides, analytical microtiter chambers and fluidic capillary channels, with the necessary high aspect ratio features (and with depths up to 40 microm) were all produced in glass, using the appropriate deposition and etching technologies. The performance of the chip was assessed in the framework of a low-volume fluorescence assay, using waveguides to address miniaturized microtiter chambers with volumes of 230 and 570 pL. Devices featuring different optical detection configurations, including both in-line and orthogonal waveguide geometries, were fabricated. In the optimal configuration, the experimental detection limit was determined as ca. 20 pM (equivalent to 10 zmol) of a cyanine fluorophore, Cy5. The applicability of the device as a biochip platform was further illustrated by analytical measurements on fluorescently labeled oligodeoxynucleotides.

Journal Article↗
PubMed1987

The use of a charge-coupled device for quantitative optical microscopy of biological structures.

The properties of a charge-coupled device (CCD) and its application to the high-resolution analysis of biological structures by optical microscopy are described. The CCD, with its high resolution, high sensitivity, wide dynamic range, photometric accuracy, and geometric stability, can provide data of such high quality that quantitative analysis on two- and three-dimensional microscopic images is possible. For example, the three-dimensional imaging properties of an epifluorescence microscope have been quantitatively determined with the CCD. This description of the imaging properties of the microscope, and the high-quality image data provided by the CCD, allow sophisticated computational image processing methods to be used that greatly improve the effective resolution obtainable for biological structures. Image processing techniques revealed fine substructures in Drosophila embryonic diploid chromosomes in two and three dimensions. The same approach can be extended to structures as small as yeast chromosomes or to other problems in structural cell biology.

Animals↗
PubMed1997

Neuromyelitis optica (Devic's syndrome): no association with the primary mitochondrial DNA mutations found in Leber hereditary optic neuropathy.

Devic's neuromyelitis optica is a rare syndrome characterised by the combination of acute or subacute optic neuritis and transverse myelitis, in some cases considered to be a variant of multiple sclerosis. Mutations of mitochondrial DNA (mtDNA) associated with Leber hereditary optic neuropathy (LHON) have been identified in some patients with multiple sclerosis in whom optic neuritis is a prominent early feature. Using restriction enzyme digestion of mtDNA products amplified by the polymerase chain reaction, the primary LHON mtDNA mutations at positions 3460 bp, 11,778 bp, and 14,484 bp have been excluded in four women with Devic's neuromyelitis optica. A mutation at 4160 bp associated in some LHON families with more widespread neurological disease was also not detected. It is concluded that the primary mtDNA mutations currently associated with LHON are not responsible for the prominence of optic nerve disease in Devic's neuromyelitis optica.

Adult↗
PubMed2003

The use of optical fiber bundles combined with electrochemistry for chemical imaging.

The present Review describes the progress made in using imaging optical fiber bundles for fluorescence and electrochemical-initiated chemiluminescence imaging. A novel optoelectrochemical micro-ring array has been fabricated and demonstrated for concurrent electrochemical and optical measurements. The device comprises optical fibers coated with gold via electroless gold deposition and assembled in a random array format. The design yielded an array of approximately 200 micro-ring electrodes, where interdiffusional problems were minimized. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 microns), while the outer radius is determined by the thickness of the deposited gold. While all the fibers are optically addressable, they are not all electrochemically addressable. The resolution of this device is in the tens of micrometers range, determined by the diameter of the optical fiber (25 microns) and by the spacing between each electrically connected fiber. For the purpose of having well-behaved microelectrode characteristics, this spacing was designed to be larger than 60 microns. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady-state currents at short response times. This device has potential application to be used as an optoelectronic sensor, especially for the electrolytic generation and transmission of electrochemiluminescence, and was used to demonstrate that electrochemically generated luminescent products can be detected with the fiber assembly.

Diagnostic Imaging↗
PubMed1992

A single optical fiber fluorometric device for measurement of intracellular Ca2+ concentration: its application to hippocampal neurons in vitro and in vivo.

We developed a new system to measure the intracellular Ca2+ concentration in the deep region of the central nervous system with a single optical fiber (300 microns in diameter), used for both excitation and detection of the fluorescence of previously loaded fura-2. With this system, a brain region loaded with fura-2 was illuminated by a rotating disc bearing three different interference filters of 340, 360 and 380 nm at a rate of 600 rpm. The emitted fluorescence was collected by the same fiber connected to a photomultiplier whose output was fed into a computer which regulates the timing of illumination and detection. The time course of the change in the fluorescence due to 340, 360 or 380 nm excitation was measured simultaneously at the maximum sampling rate of 10 points/s. Ratios of fluorescence intensities were obtained after the experiment. After confirming that this system was sensitive enough to detect the change of intracellular Ca2+ concentration in cultured hippocampal neurons and hippocampal slices during depolarization by high potassium medium (50 mM), we applied this system to anesthetized rats. In the hippocampus preloaded with fura-2, characteristic changes in fluorescence intensities ascribed to an increase in intracellular Ca2+ concentration were detected after asphyxia. The system is potentially useful for investigating the physiological and pathological roles of Ca2+ in the brain.

Anesthesia↗
PubMed1997

A new optical 3-D device for the detection of wear.

For the clinical performance of new dental restorative materials to be accurately assessed, the three-dimensional anatomical changes of the functional surfaces of the restoration must be elucidated over time. To this end, a highly accurate 3-D optical scanner has been developed that utilizes the principles of triangulation and a reference-free automated 3-D superimposition software. The aim of this study was to assess the accuracy and the precision of the new system with and without referenced positioning. Additionally, the ability of the system to determine wear of posterior fillings three-dimensionally has been shown. Gypsum replicas of restored teeth were evaluated. The tooth surfaces were scanned with a resolution of 250,000 surface points within a measuring time of 20 to 40 sec. The results show that the precision and accuracy of 3-D data acquisition depend on the surface inclination. Up to an angle of 60 degrees, the precision is better than 3 microns, and the accuracy is better than 6 microns. If exact repositioning of the object before and after occlusal loading is possible, e.g., with in vitro studies, differences on the surface can be determined with a precision of 2.2 microns. In reference-free measurements, which are a necessity in clinical studies, the 3-D data acquisition in combination with the automatic matching program can detect wear with an accuracy of 10 microns. The application of this measuring device for the detection of wear of a composite filling functioning in the mouth has been shown. Since this measuring technique is automated, and measurements of high accuracy can be attained in a short period of time, this system offers the possibility for complex analyses of three-dimensional wear to be conducted on a large number of samples in clinical studies.

Algorithms↗
PubMed2006

Three-color mixing for classifying agricultural products for safety and quality.

A three-color mixing application for food safety inspection is presented. It is shown that the chromaticness of the visual signal resulting from the three-color mixing achieved through our device is directly related to the three-band ratio of light intensity at three selected wavebands. An optical visual device using three-color mixing to implement the three-band ratio criterion is presented. Inspection through human vision assisted by an optical device that implements the three-band ratio criterion would offer flexibility and significant cost savings as compared to inspection with a multispectral machine vision system that implements the same criterion. Example applications of this optical three-color mixing technique are given for the inspection of chicken carcasses with various diseases and for apples with fecal contamination. With proper selection of the three narrow wavebands, discrimination by chromaticness that has a direct relation with the three-band ratio can work very well. In particular, compared with the previously presented two-color mixing application, the conditions of chicken carcasses were more easily identified using the three-color mixing application. The novel three-color mixing technique for visual inspection can be implemented on visual devices for a variety of applications, ranging from target detection to food safety inspection.

Agriculture↗
PubMed2006

Advantages and limitations of prospective head motion compensation for MRI using an optical motion tracking device.

RATIONALE AND OBJECTIVES: Subject motion appears to be a limiting factor in numerous magnetic resonance (MR) imaging (MRI) applications. In particular, head tremor, which often accompanies stroke, may render certain high-resolution two- (2D) and three-dimensional (3D) techniques inapplicable. The reason for that is head movement during acquisition. The study objective is to achieve a method able to compensate for complete motion during data acquisition. The method should be usable for every sequence and easily implemented on different MR scanners. MATERIALS AND METHODS: The possibility of interfacing the MR scanner with an external optical motion-tracking system capable of determining the object's position with submillimeter accuracy and an update rate of 60 Hz is shown. Movement information on the object position (head) is used to compensate for motion in real time by updating the field of view (FOV) by recalculating the gradients and radiofrequency parameter of the MR scanner during acquisition of k-space data, based on tracking data. RESULTS: Results of rotation phantom, in vivo experiments, and implementation of three different MRI sequences, 2D spin echo, 3D gradient echo, and echo planar imaging, are presented. Finally, the proposed method is compared with the prospective motion correction software available on the scanner software. CONCLUSION: A prospective motion correction method that works in real time only by updating the FOV of the MR scanner is presented. Results show the feasibility of using an external optical motion-tracking system to compensate for strong and fast subject motion during acquisition.

Algorithms↗
PubMed2006

Developing optofluidic technology through the fusion of microfluidics and optics.

We describe devices in which optics and fluidics are used synergistically to synthesize novel functionalities. Fluidic replacement or modification leads to reconfigurable optical systems, whereas the implementation of optics through the microfluidic toolkit gives highly compact and integrated devices. We categorize optofluidics according to three broad categories of interactions: fluid-solid interfaces, purely fluidic interfaces and colloidal suspensions. We describe examples of optofluidic devices in each category.

Animals↗
PubMed1990

[Test of non-invasive PVI measure with a fiber-optic pressure monitoring device in head injured patients].

At present, method for determining pressure volume status in head injured patients must be obtained via analysis of pressure response to bolus injections into the ventricular catheter system. The concept introduced by Bray of extracting Pressure Volume Index (PVI) measures from analysis of the pulse pressure centroid presents a less invasive technique and provides PVI data continuously. The objective of this study was to test the application of the system which incorporated the Bray concept to PVI measures in head injured patients. The centroid of frequency power spectrum was provided continuously by a computer system linked to the bedside monitor. The computer incorporated the Bray concept for PVI estimation. These values were compared with PVI measured by conventional bolus technique. We tested the system using ICP pulsating wave form delivered from a fiberoptic pressure monitoring system in brain tissue in two different band-width (Narrow band-width: 4-8 Hz, Wide band-width: 4-15 Hz). PVI studies using bolus fluid injection or withdrawal were conducted at least twice a day and usually each study consisted of 3 to 6 injections or withdrawals to obtain a study average PVI. These study average were correlated with the centroid obtained during the same study interval in 17 head injured patients of Glasgow Coma Scale (GCS) 8 or less. The correlation of the centroid and PVI in the wide band-width group was significant (p less than 0.01, r = 0.77), however, in the narrow band-width group, the correlation was not significant (r = 0.07, N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2006

[Quality control in rehabilitation of patients with visual impairment: evaluation of use and benefits of optic and electronic devices].

BACKGROUND: Not only medical care and prescription of magnifying devices, but also social and professional rehabilitation are part of a complete interdisciplinary low vision service. This study provides quantitative data about the success of rehabilitation and the quality of the Low Vision Department's work. PATIENTS AND METHODS: A sample of 105 visually disabled patients, who had already been provided with magnifying aids and other rehabilitation measures by the Low Vision Department, answered a questionnaire about quality control during a follow-up visit. The survey was carried out between May and October 2004. Patients were asked to rate the different rehabilitation measures and to comment on how frequently they used the different magnifying devices. Furthermore, they were asked to judge to what degree they coped with different life situations when using or not using the low vision aids. RESULTS: The most frequently used aids were magnifiers (61%), glasses for near vision (34%), closed circuit television (20%), and monocular telescopes (20%). Of the 105 patients, 85 (81%) reported on frequent use of the devices, with just 3 patients (3%) reporting that they hardly ever used the aids. Only 2% of the patients could read newspaper text without the use of magnifying aids, while 51% were able to do this using the aids; 46% of the patients reported that they had profited from the social and professional rehabilitation measures. CONCLUSION: Independently from the causal ophthalmologic diagnosis, patients were found to have benefited greatly from the rehabilitation measures provided by the Low Vision Department, enabling them to take part in more activities and participate more fully in social life, thereby greatly improving their quality of life. Frequent use of the low vision aids by the patient was ensured when offered alongside continued professional support.

Aged↗
PubMed2006

Discrimination between glaucomatous and nonglaucomatous eyes using quantitative imaging devices and subjective optic nerve head assessment.

PURPOSE: To compare the diagnostic ability of the confocal scanning laser ophthalmoscope (HRT-II; Heidelberg Engineering, Heidelberg, Germany), scanning laser polarimeter (GDx-VCC; Carl Zeiss Meditec, Inc., Dublin, CA), and optical coherence tomographer (StratusOCT, Carl Zeiss Meditec, Inc.) with subjective assessment of optic nerve head (ONH) stereophotographs in discriminating glaucomatous from nonglaucomatous eyes. METHODS: Data from 79 glaucomatous and 149 normal eyes of 228 subjects were included in the analysis. Three independent graders evaluated ONH stereophotographs. Receiver operating characteristic curves were constructed for each technique and sensitivity was estimated at 80% of specificity. Comparisons of areas under these curves (aROC) and agreement (kappa) were determined between stereophoto grading and best parameter from each technique. RESULTS: Stereophotograph grading had the largest aROC and sensitivity (0.903, 77.22%) in comparison with the best parameter from each technique: HRT-II global cup-to-disc area ratio (0.861, 75.95%); GDx-VCC Nerve Fiber Indicator (NFI; 0.836, 68.35%); and StratusOCT retinal nerve fiber layer (RNFL) thickness (0.844, 69.62%), ONH vertical integrated rim area (VIRA; 0.854, 73.42%), and macular thickness (0.815, 67.09%). The kappa between photograph grading and imaging parameters was 0.71 for StratusOCT-VIRA, 0.57 for HRT-II cup-to-disc area ratio, 0.51 for GDX-VCC NFI, 0.33 for StratusOCT RNFL, and 0.28 for StratusOCT macular thickness. CONCLUSIONS: Similar diagnostic ability was found for all imaging techniques, but none demonstrated superiority to subjective assessment of the ONH. Agreement between disease classification with subjective assessment of ONH and imaging techniques was greater for techniques that evaluate ONH topography than with techniques that evaluate RNFL parameters. A combination of subjective ONH evaluation with RNFL parameters provides additive information, may have clinical impact, and deserves to be considered in the design of future studies comparing objective techniques with subjective evaluation by general eye care providers.

Adult↗