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At least 289 records · Page 16Linked to original sources
PubMed2005

Portable light transmission measuring system for preserved corneas.

BACKGROUND: The authors have developed a small portable device for the objective measurement of the transparency of corneas stored in preservative medium, for use by eye banks in evaluation prior to transplantation. METHODS: The optical system consists of a white light, lenses, and pinholes that collimate the white light beams and illuminate the cornea in its preservative medium, and an optical filter (400-700 nm) that selects the range of the wavelength of interest. A sensor detects the light that passes through the cornea, and the average corneal transparency is displayed. In order to obtain only the tissue transparency, an electronic circuit was built to detect a baseline input of the preservative medium prior to the measurement of corneal transparency. The operation of the system involves three steps: adjusting the "0 %" transmittance of the instrument, determining the "100 %" transmittance of the system, and finally measuring the transparency of the preserved cornea inside the storage medium. RESULTS: Fifty selected corneas were evaluated. Each cornea was submitted to three evaluation methods: subjective classification of transparency through a slit lamp, quantification of the transmittance of light using a corneal spectrophotometer previously developed, and measurement of transparency with the portable device. CONCLUSION: By comparing the three methods and using the expertise of eye bank trained personnel, a table for quantifying corneal transparency with the new device has been developed. The correlation factor between the corneal spectrophotometer and the new device is 0,99813, leading to a system that is able to standardize transparency measurements of preserved corneas, which is currently done subjectively.

Cornea↗
PubMed1993

Future directions in electronic image handling.

After a relatively slow start compared with the United States and Japan, several projects are now being established in Europe that are aimed at the development of prototype systems for medical image processing and management. Frequently, this includes aspects of multimedia communication, as well as legal, ethical, and economic issues. Consideration is also often given to systems security, reliability, and data protection. All these projects are based on the application of modern computer and communication technologies. The following interesting conclusions can be drawn from these preliminary activities: 1. PACS and IMAC systems should not be regarded as products or devices, but as a means to improve the infrastructure in a given medical care environment. Sometimes this activity is also referred to as knowledge business. Individual components of these systems, for example image acquisition devices, networks, storage facilities, and medical workstations, should be provided with standard interfaces allowing a modular build-up and an easy adaptation to the specific conditions of clinical departments. 2. Digital luminescence radiography will further establish itself as a method for image acquisition and increasingly will replace analog radiologic methods. Consequently, digital processing, archiving, and communication will be a necessity for optimal patient care. 3. New network technologies and magnetic-optical storage media offer the possibility of an improved cost-effectiveness for communication and storage. They should therefore be considered an important factor in future economic considerations regarding health care services. 4. The practice of modern medicine is based on team-work; good communication among the parties concerned is a critical factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Communication Networks↗
PubMed1998

Diode laser absorption sensors for gas-dynamic and combustion flows.

Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room-temperature mid-IR materials and broadly tunable multisection devices is reviewed to suggest new sensor possibilities.

Absorption↗
PubMed1991

Electronic system for digital acquisition of rotational panoramic radiographs.

A prototype system for digital panoramic imaging of the maxillofacial complex has been developed. In this system x-ray film is replaced by an electronic sensor that delivers the image information to a computer for storage in digital format. The images, which are similar to conventional panoramic radiographs, are displayed on a high-resolution video monitor and may be stored on optical disk for future use. Hard-copy output is also available. The present prototype system has been installed on an Orthopantomograph model OP10 panoramic x-ray machine is programmed for operation with this machine, but in principle the system can be installed on any such device. The system may be incorporated into the design of future panoramic x-ray systems or may be used to retrofit panoramic x-ray systems now using photographic film to record the radiographic image. Greater sensitivity of electronic sensors should make possible a reduction of x-ray dose to the patient, compared with film-based systems.

Analog-Digital Conversion↗
PubMed2003

Electric field-induced cubic phase in 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid.

We examine the influence of an alternating-current electric field on the lamellar smectic C (SmC) phase of 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid, and the formation of a field-induced cubic (Cub) phase with optical isotropy was observed for the first time. The induction was realized down to a temperature 10 K below the zero-field SmC to Cub phase transition temperature (TSmC-Cub). The formation of the induced Cub phase gave rise to a gradual increase of the shear storage modulus, and the modulus recovered quickly in response to the removal of the field, which is of interest as future applications to the stress transferring device.

Journal Article↗
PubMed2000

An automated, handheld biosensor for aflatoxin.

A new immunoaffinity fluorometric biosensor has been developed for detecting and quantifying aflatoxins, a family of potent fungi-produced carcinogens that are commonly found in a variety of agriculture products. They have also been cited as a biological agent under weapons development. The handheld, self-contained biosensor is fully automatic, highly sensitive, quick, quantitative, and requires no special storage. Approximately 100 measurements can be made before refurbishment is required, and concentrations from 0.1 parts per billion (ppb) to 50 ppb can be determined in <2 min with a 1 ml sample volume. The device operates on the principles of immunoaffinity for specificity and fluorescence for a quantitative assay. The analytic procedure is flexible so that other chemical and biological analytes could be detected with minor modifications to the current device. Advances in electro-optical components, electronics, and miniaturized fluidics were combined to produce this reliable, small, and versatile instrument.

Aflatoxins↗
PubMedDate not supplied

Applications of array biosensor for detection of food allergens.

Although food is a necessity, compounds within food products can be dangerous and life-threatening for people with food allergies. These allergy-causing compounds, such as proteins from eggs and milk, must be identified on the labels of commercial products. Unintentional contamination of food with these compounds occurs as a result of storage, manufacturing procedures, or cleaning procedures. A sensitive, specific, and rapid method to identify foods containing allergens is required by the food industry. The array biosensor, a rapid detection system, may provide a solution to this need. The array biosensor performs fluorescent immunoassays on the surface of a planar waveguide by first running samples, then fluorescently labeled antibodies, over a surface patterned with capture antibodies. An optical image is captured by a charged-coupled device camera and converted into fluorescence values. Signal intensity and spot location provide information on the compound and its concentration. The array biosensor has been successfully demonstrated for toxin, bacteria, and virus detection at low levels in under 20 min in food, clinical samples, and environmental matrixes. An assay for detection of ovalbumin as an indicator of egg contamination has been developed with limits of detection of 25 pg/mL in buffer and 1.3 ng/mL (13 ng/g) in non-egg pasta extract (buffer:pasta 10:1, v/w).

Allergens↗
PubMed1989

Improved control of image optical density with low-dose digital and conventional radiography in bedside imaging.

The technical and diagnostic performance of simultaneously acquired low-dose (44% of standard dose) storage-phosphor digital radiographs (system resolution = 0.2 mm, 10 bits) were compared with those of standard-dose conventional bedside radiographs of the chest in 32 patients. The mean optical density (OD) of the lungs (800 measurements) was closer to the ideal density with digital radiography (1.45 OD +/- 0.20 [standard deviation] vs 1.75 OD +/- 0.53) and was less often outside the usable range (2.5% vs 42.5%). Receiver operating characteristic analysis for detection of simulated nodules and monitoring devices (nine readers, 4,608 observations) showed that digital radiography was superior to conventional radiography (P less than .05) for four of the nine readers and equivalent to conventional radiography for five readers. The authors concluded that digital radiography produces more consistent and ideal image density and performs at least as well as conventional radiography under phantom test conditions.

Absorptiometry, Photon↗
PubMedDate not supplied

Optical densities of dental resin composites: a comparison of CCD, storage phosphor, and Ektaspeed plus radiographic film.

Density versus exposure was determined for digital and film radiographic images of various thicknesses of six dental resin composites. The curves were relatively parallel; saturation at the black end of the contrast scale occurred at lower exposures with Computed Dental Radiography (CDR, Schick Industries, Long Island City, NY) than with the Sens-A-Ray (Regam AB, Sundsvall, Sweden). Ektaspeed Plus film (Kodak Dental Products, Rochester, NY) was the least sensitive modality tested. The DIGORA storage phosphor system (Soredex-Orion, Helsinki) had a wide exposure latitude with significantly less steep characteristic slopes than for images from the charge-coupled devices (CCDs). Slopes generated for the Sens-A-Ray and the CDR were not significantly different. Slopes generated for each resin composite were not significantly different for each of the modalities. Relative radiopacities of the resin materials with respect to each other were constant across all modalities; hence, in these systems, sensor type is unlikely to affect differentiation between resin composites and dental enamel or recurrent caries.

Absorptiometry, Photon↗
PubMed1994

Advanced image analysis systems in cell, molecular and neurobiology applications.

Many of today's image acquisition devices (scanners and cameras) yield high-resolution (1280 x 1024 pixels is typical) and/or high-precision (> 8 bits) image data. When coupled to a powerful image analyzer these image acquisition devices offer practical advantages in many bioscience applications. The benefits of high resolution include better contrast transfer (sharper images with more accurate density rendition) and an ability to work with large specimens at lower optical magnifications (larger field of view). High precision is useful if images contain subtle features (e.g., fluorescently labeled processes at densities close to background) and/or wide dynamic range. Examples are given, illustrating the use of a number of medium- and high-performance image acquisition devices with an advanced image analyzer. The examples include a comparison of intensified and integrating cameras in fluorescence microscopy, evaluation of the performance of a fast, cooled integrating camera in ratio fluorescence imaging, and a comparison of film and storage phosphor-plate performance in quantitative receptor autoradiography.

Animals↗
PubMed1995

Fiber-optic DNA sensor for fluorometric nucleic acid determination.

Single-stranded deoxyribonucleic acid (ssDNA) thymidylic acid icosanucleotides (dT20) were synthesized on the surfaces of derivatized quartz optical fibers to create an optical DNA biosensor. The synthesis made use of an automated solid-phase synthesizer and phosphoramidite synthons. The covalently immobilized oligomers were found to hybridize with complementary ssDNA (cDNA) or ssRNA (cRNA) from solution, and the device was regenerable for multiple cycles of application. Hybridization on optical fibers was detected by the use of the fluorescent DNA stain ethidium bromide (EB). The procedure used hybridization assay techniques and provided a detection limit of 86 ng x mL(-1) cDNA and a sensitivity of 200% fluorescence intensity increase per 100 ng x mL(-1) of cDNA, with one cycle of hybridization analysis requiring 45 min. The sensor has been observed to be regenerable (minimum of five cycles) and to sustain full activity after prolonged storage times (1 year), harsh washing conditions (sonication), and sterilization (autoclaving). The extent of hybridization between the immobilized and complementary nucleic acid strands was determined by UV absorbance thermal denaturation studies wherein all 20 bases on each strand of the nucleic acid were found to be involved in duplex formation.

Biosensing Techniques↗
PubMed2002

High-precision shape measurement by white-light interferometry with real-time scanner error correction.

White-light interferometric techniques allow high-precision shape measurement of objects with discontinuous structures by detecting the peak of the coherence envelope. These techniques assume a specific change in the optical path difference (OPD) between the interfering beams; however, the scanning device effecting that change often introduces OPD errors that are carried over to the measurements. We present a technique for measuring OPD changes from the collected interference fringes during each measurement. Information about the scan is directly fed into the algorithm, which compensates for the errors, resulting in improved measurement accuracy. The method corrects not only the scanner errors but also slowly varying vibrations. In addition, this technique can be easily adapted to any existing low-coherence interferometer because no large data storage or postprocessing is required.

Journal Article↗
PubMed2003

Single-nanowire electrically driven lasers.

Electrically driven semiconductor lasers are used in technologies ranging from telecommunications and information storage to medical diagnostics and therapeutics. The success of this class of lasers is due in part to well-developed planar semiconductor growth and processing, which enables reproducible fabrication of integrated, electrically driven devices. Yet this approach to device fabrication is also costly and difficult to integrate directly with other technologies such as silicon microelectronics. To overcome these issues for future applications, there has been considerable interest in using organic molecules, polymers, and inorganic nanostructures for lasers, because these materials can be fashioned into devices by chemical processing. Indeed, amplified stimulated emission and lasing have been reported for optically pumped organic systems and, more recently, inorganic nanocrystals and nanowires. However, electrically driven lasing, which is required in most applications, has met with several difficulties in organic systems, and has not been addressed for assembled nanocrystals or nanowires. Here we investigate the feasibility of achieving electrically driven lasing from individual nanowires. Optical and electrical measurements made on single-crystal cadmium sulphide nanowires show that these structures can function as Fabry-Perot optical cavities with mode spacing inversely related to the nanowire length. Investigations of optical and electrical pumping further indicate a threshold for lasing as characterized by optical modes with instrument-limited linewidths. Electrically driven nanowire lasers, which might be assembled in arrays capable of emitting a wide range of colours, could improve existing applications and suggest new opportunities.

Journal Article↗
PubMed2004

Digital image storage.

Film has long been considered the gold standard for displaying and storing clinical images. But that may be changing. Digital technology--specifically digital imaging and storage technology--has advanced to the point where it can now deliver on the promises envisioned years ago. That is, the ability to provide any image, virtually anywhere, at any time--a goal that could never be achieved with film. Achieving this goal, however, requires a properly implemented digital infrastructure, including effective digital image storage. As early adopters will attest, digital image storage can be difficult to implement. It requires the careful selection and implementation of storage technologies and the continuous management of storage operations. In this Guidance Article, we address many of the issues facing the healthcare professionals charged with managing this process: We introduce the topic of medical digital storage, discussing how it is accomplished and why storing images is not that different from storing other forms of data. We review the available storage alternatives, from fast-access hard drives and RAIDs to long-term magnetic tape and optical disc storage. We delve into the issue of image compression, describing what compression is and how much can be used without affecting patient care. And we review the pertinent legal, regulatory, and management issues. When committing to a digital image workflow, it is essential that a healthcare facility give careful consideration to data storage issues, since poor choices can lead to significant long-term costs for the facility.

Computer Storage Devices↗
PubMed1985

Pseudo-outbreak of Bacillus species: related to fibreoptic bronchoscopy.

In July and August 1980, Bacillus spp. were isolated with unusual frequency from bronchial washings obtained during bronchoscopy performed with fibreoptic equipment. Clinical disease in culture-positive patients was not apparent; but Bacillus spp. were recovered from one component of the bronchoscope, the automatic suction valve. It appeared that secretions became contaminated during passage through the valve en route to a collection device. After institution of controls directed primarily at proper storage and maintenance, the number of isolations of Bacillus spp. decreased significantly. Thus, investigation revealed a site for contamination not previously described and the results suggest that in future outbreaks, cultures of the component parts may permit localization of the site of contamination which may help focus control measures.

Bacillus↗
PubMed2006

[Recent advances in airway management devices].

As a variety of new airway devices has been introduced, the practice of airway management has seemingly become more complex. Among them laryngeal mask airway (LMA) is the single most important development in the past 10 years. It has become a commonly accepted device for routine and rescue airway management, and is now listed in the American Society of Anesthesiologists (ASA) Difficult Airway Management Algorithm as an airway and a conduit for tracheal intubation. The ASA Task Force on Management of the Difficult Airway recommends us to have a portable storage unit that contains specialized equipment including LMA for difficult airway management. This article focuses on several of the newly developed and the ordinary devices that are listed by the Task Force, with particular emphasis on the difficult airway. Recent information about standardization work of ISO for rigid laryngoscopes, tracheal tubes and supralaryngeal airway devices are also discussed. Each airway devices has unique properties that may be advantageous in certain situations but disadvantageous in others. Choice and combination of device based on experienced clinical judgment may be crucial to their application.

Anesthesiology↗
PubMed2006

Strategies for data collection and calibration with a pinhole-geometry SAXS instrument on a synchrotron beamline.

Undulator X-ray sources on third-generation synchrotrons have pushed small-angle X-ray scattering (SAXS) to the forefront of techniques in nanoscience and technology. With higher X-ray fluxes and improved focusing, it is usually the scattered intensity detector that places the most serious limitations on the overall capabilities of the instrument. Incorporating relatively simple components like point detectors, scattering standards, masking filters and in-line sample visualization into the flight tube of a pinhole-geometry SAXS camera can do much to mitigate these limitations. How these enhancements can be incorporated into routine data collection is demonstrated on the ChemMatCARS SAXS instrument, which utilizes pinhole geometry with an undulator insertion device at sector 15 of the Advanced Photon Source. In addition, with an X-ray energy range of 6-32 keV (2.0-0.4 A) and an energy resolution of 10(-4) DeltaE/E, this instrument can measure anomalous SAXS over a wide variety of atom species, with reliable normalization of scattered data.

Calibration↗
PubMedDate not supplied

A high-resolution digital dosimetric system for spatial characterization of radiation fields using a thermoluminescent CaF2:Dy crystal.

A high-resolution digital dosimetric system has been developed for the spatial characterization of radiation fields. The system comprises the following: 0.5-mm-thick, 25-mm-diam CaF2:Dy thermoluminescent crystal; intensified charge coupled device video camera; video cassette recorder; and a computerized image processing subsystem. The optically flat single crystal is used as a radiation imaging device and the subsequent thermally stimulated phosphorescence is viewed by the intensified camera for further processing and analysis. Parameters governing the performance characteristics of the system were measured. A spatial resolution limit of 31 +/- 2 microns (1 sigma) corresponding to 16 +/- 1 line pairs/mm measured at the 4% level of the modulation transfer function has been achieved. The full width at half maximum of the line spread function measured independently by the slit method or derived from the edge response function was found to be 69 +/- 4 microns (1 sigma). The high resolving power, speed of readout, good precision, wide dynamic range, and the large image storage capacity make the system suitable for the digital mapping of the relative distribution of absorbed doses for various small radiation fields and the edges of larger fields.

Health Physics↗