SEARCH · PubMed Health

Results for “Fiber Optic Technology”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2005

Combined affinity and catalytic biosensor: in situ enzymatic activity monitoring of surface-bound enzymes.

Surface Plasmon Resonance Spectroscopy (SPR) and miniature Fiber Optic Absorbance Spectroscopy (FOAS) were combined to monitor in situ and quantitatively an enzymatic model reaction catalyzed by beta-lactamase. The enzyme was covalently immobilized to the gold surface of a SPR chip, which was functionalized with NeutrAvidin through a biotinylated alkanethiol self-assembled monolayer, thus serving as a highly sensitive affinity biosensor. SPR was used to control the density of the surface-bound enzyme. Nitrocefin as the enzymatic substrate was allowed to react with the immobilized enzyme in the SPR flow cell, and its turnover was detected with the FOAS system acting as the catalytic biosensor. The coupling of the two techniques has a substantial potential for highly controlled on-line monitoring of surface-bound enzyme activity. The FOAS technique may also be easily employed as an add-on device to other types of affinity sensing instruments.

Biosensing Techniques↗

PubMed2006

Optical sensor for sulfur dioxide determination in wines.

A method for the determination of free and total sulfur dioxide in wines, based on the use of an optical sensor that employs a dichlorobis(diphenylphosphino)methane dipalladium I complex [Pd(2)(dppm)(2)Cl(2)] immobilized in a PVC membrane plasticized with o-nitrophenyloctylether (o-NPOE) is described. A sensing membrane [4.2% Pd(2)(dppm)(2)Cl(2), 20.8% PVC, and 75% o-NPOE] was adapted to the tip of a bifurcated optical fiber bundle to perform reflectance measurements at 550 nm. The detection system consisted of two cells (40 mL), which hold the sample solution (plus reagents) and the optical sensor, respectively. For the determination of free SO(2), a wine sample was mixed with H(2)SO(4) solution in the sample cell, into which N(2) was bubbled, providing mixing of the solutions and conducting the SO(2) formed toward the detection cell. For determination of total SO(2), a KOH solution was mixed with the wine in the sample cell. Afterward, an H(2)SO(4) solution was added to the cell, and then N(2) was bubbled to conclude the measurement. Linear responses up to 50 and 150 mg L(-1) were obtained for free and total SO(2), with detection limits of 0.37 and 0.70 mg L(-1), respectively. The repeatability of the method was evaluated by carrying out 10 measurements using a single wine sample, providing relative standard deviation values of 2.2 and 2.5% for free and total SO(2), respectively. The sensing membrane prepared from 10 muL of the cocktail solution lasted for 80 measurements, whereas those prepared from 200 muL can be used for 250 measurements. The method was applied to free and total SO(2) determination in wines, and the results did not show significant difference from those obtained with the Ripper reference method at a confidence level of 95%.

Chemistry Techniques, Analytical↗

PubMed2000

Modular separation-based fiber-optic sensors for remote in situ monitoring.

A modular separation-based fiber-optic sensor (SBFOS) with an integrated electronically controlled injection device is described for potential use in remote environmental monitoring. An SBFOS is a chemical monitor that integrates the separation selectivity and versatility afforded by capillary electrophoresis with the remote and high sensitivity capabilities of fiber-optic-based laser-induced fluorescence sensing. The detection module of the SBFOS accommodates all essential sensing components for dual-optical fiber, on-capillary fluorescence detection. An injection module, similar to injection platforms on micro-analysis chips, is also integrated to the SBFOS. The injection module allows for electronically controlled injection of the sample onto the separation capillary. The design and operational characteristics of the modular SBFOS are discussed in this paper. A micellar electrokinetic capillary chromatography mode of separation is employed to evaluate the potential of the sensor for in situ monitoring of neutral toxins (aflatoxins). The analytical figures of merit for the modular SBFOS include analysis times of between 5 and 10 min, separation efficiencies of approximately 10(4) theoretical plates, detection limits for aflatoxins in the mid-to-low nanomolar range, and controllable operation that results in sensor performance that is largely immune to sample matrix effects.

Chromatography↗

PubMed2000

A remote flow cell for UV absorbance detection with capillary HPLC based on a single strand fiber optic.

A remote flow cell based on a single strand of fused-silica fiber optic was built for UV absorbance detection with a packed capillary HPLC system, using commercially available pumps, detection electronics (Shimadzu) and fittings. This 'off-column' flow cell design is applicable to both pressure and electro-osmotically driven systems. The goals were to minimize the linearity and light leakage problems that often limit the performance of UV absorbance detection with capillary chromatography. A linear dynamic range of 10(3) (reserpine, lambda = 220 nm), and a concentration detection limit of 5.1 x 10(-8) mol l-1 were observed. Baseline noise was measured at 3.5 x 10(-5) absorbance units (AU), with a standard deviation of 1.7 x 10(-5) AU. The illuminated volume of approximately 3 nl was optimized for capillaries with inner diameters in the range 50-100 microns, and flow rates from 100 nl min-1 to 1 microliter min-1. These modifications of readily available instrumentation have allowed the construction of a practical system for fractionating complex mixtures of peptides in small amounts, prior to mass spectrometry or additional wet chemistry steps.

Chromatography, High Pressure Liquid↗

PubMed2002

A highly sensitive hexachromium monitor using water core optical fiber with UV LED.

A simply structured, cheap hexachromium monitor was developed. The monitor is based on UV/VIS absorption technique. A 2-m long water core optical fiber was employed as a long path length sample cell and a UV light emitting diode (LED) was used as a light source. The emission profile of the UV LED fits very well with the absorption spectrum of chromate ions in water. Therefore, the light-dispersing element, which is usually used in an optical spectrometer, is not necessary in this monitor design. The water core fiber as a long path length makes the monitor highly sensitive for hexachromium detection. This monitor is specific for hexachromium detection without interference from tri-valence chromium ions. A detection limit of 0.1 ng Cr(VI) ml(-1) was obtained with this simple monitor.

Adsorption↗

PubMed2001

A portable fiber-optic chemical device for the quantitative determination of carbon monoxide from automobile exhaust emissions.

A colorimetric method for the quantitative determination of CO by diffuse reflectance is described. This method is based on the reduction by CO of Mo (VI) from the indicator reagent molybdosilicic acid (H8Si[Mo2O7]6). The reduction yielded a change of color from clear yellow to dark green on white disk filter chart paper wetted with reagent indicator solution. The gaseous mixture containing CO was forced to pass through this chart paper, initiating the reaction. The intensity of the color produced, measured by diffuse reflectance, was proportional to the CO concentration present in exhaust gases in the range from 0.02 to 12% volume/volume (v/v). A 650-nm light-emitting diode was used as a light source. A two-fiber-optic system carried the light from the source to the detection system, which was composed of a photodiode, an amplification circuit, and a digital display. The method was applied with success in field measurements for automobiles in the Otto cycle. In a previous paper, this method was used for the quantitative determination of exhaust emissions from diesel-fueled vehicles.

Carbon Monoxide↗

PubMed2003

Using fiber optics to detect moisture intrusion into a landfill cap consisting of a vegetative soil barrier.

The intrusion of moisture into landfills can pose a health hazard because of the possibility that the moisture will carry harmful substances into the groundwater. Early detection of moisture anywhere within these landfills is essential if corrective action is to be taken well before an occurrence of this kind. This paper presents the results of a field-scale simulation test of the use of fiber optics to detect the presence of moisture within landfill covers, using a detection method based on the thermal response of soils as a function of their moisture content. By sending electrical current through an embedded stainless-steel tube, soils of varying moisture content were heated and time-dependent temperature measurements were obtained with a fiber-optic distributed temperature sensor system. The optical fiber itself lay within the tube, but its temperature was a function of how rapidly heat was conducted into the surrounding medium. The results of this experiment, which are in agreement with those obtained using more traditional "point" sampling and laboratory analysis, are presented along with the strengths and limitations of the thermal-response method of detecting moisture.

Environmental Monitoring↗

PubMed1996

Advances in the development of the interferometric otoscope.

Present measurement techniques for middle ear function have inherent limitations because they are either spatially insensitive (acoustic immittance) or descriptive and qualitative in nature (otoscopy). By integrating advances in electrooptic technology (fiber optics, miniature diode lasers, solid-state detector arrays) and digital processing, further advances are possible. On the basis of measurements taken with electronic speckle-pattern interferometry on human temporal bones and models, we demonstrate quantitative static and dynamic vibration/displacement characteristics of the tympanic membrane with high spatial resolution. Our presentation emphasizes advantages of optically based methods and demonstrates computerized signal processing capable of fringe localization, enhancement, and counting. Miniaturization and real-time digital image processing in the clinical setting is the goal of this research.

Humans↗

PubMed1993

Development of a dual function sensor system for measuring pressure and temperature at the tip of a single optical fiber.

A dual function sensor system has been developed for measuring pressure and temperature at the tip of a single optical fiber. The sensor contains three parts: a filter band-edge shift temperature based spectral modulation pressure sensor. The sensor system uses a separate and distinct LED for interrogating each sensor, three 100/140 microns step-index fused couplers for managing light, and separate paired photodiode assemblies for analyzing the return light signal from each sensor. In bench tests, each sensor performed to specification and, importantly, there was no crosstalk between sensors. This dual function sensor design has potential catheter applications where catheter size must be kept to an absolute minimum.

Equipment Design↗

PubMed1992

Multifiber, multiwavelength, fiber optic fluorescence spectrophotometer.

A fiberoptic spectrofluorimeter was constructed capable of remote operation of up to 18 biosensors under fully automated, multiplexed control. Excitation and emission wavelengths were separately adjustable, as were optical bandwidths, signal gain, phase, integration time, and illumination duty cycle. Synchronous demodulation was used to enhance signal-to-noise ratio and allow operation under ambient lighting conditions. Detection limit for aqueous sodium-fluorescein was below 1 ng/mL at greater than unity signal-to-noise ratio, with effective sampling volumes less than 0.02 microL. The fluorimeter showed characteristics fiberoptic sampling behavior with asymptotic nonzero signal magnitudes under increasing pathlength conditions.

Equipment Design↗

PubMed1991

A low-cost fiber-optic strain gage system for biological applications.

A new low-cost strain measurement system has been developed for the mechanical testing of biological soft tissues. The technique creates four spots of light on a tissue sample surface by piercing the tissue sample with two pairs of small light-conducting optical fibers (one pair for each axis of a biaxial stretch), terminated by high intensity infrared emitters. A large-area photodiode, located below the tissue sample, detects the light emitted from the two pairs of light-spots. Analog and digital circuitry analyze the current signal from the photodiode to determine the position of a light-spot in real time. Each infrared emitter is sequentially cycled "on" at a rate of 3 kHz and the resulting photodiode current signal, after being converted to a voltage signal, is held by an integrated circuit sample and hold amplifier. Analog differencing of pairs of light-spot voltage signals provides a final output proportional to the separation between coaxial light-spots.

Biomechanical Phenomena↗

PubMedDate not supplied

Quantitative concentration measurements of creatinine dissolved in water and urine using Raman spectroscopy and a liquid core optical fiber.

We describe the use of a Teflon-AF liquid core optical fiber (LCOF) geometry to enhance the collection of Raman scattering from the biochemical creatinine, dissolved in water and in urine. At short integration times, where shot noise is most troublesome, the enhanced signal leads to greater accuracy in estimating the creatinine concentration from the spectrum. At longer integration times, instabilities in the LCOF geometry manifest themselves, and the predictions are the same as or worse than those from standard cuvette-based spectral measurements. Photobleaching of fluorescence from urine is more extensive and more stable in the LCOF as well. Starting from the measured enhancement of a major creatinine Raman band, we calculate the expected ratio of prediction errors obtained using the two geometries, and it agrees closely with the observed ratio. These results indicate that Raman spectroscopy with these Teflon-AF LCOFs is stable enough for quantitative concentration predictions, accurate to a few percent of the concentration range spanned.

Algorithms↗

PubMed2006

Surface preparation and coupling in plastic scintillator dosimetry.

One way to improve the performance of scintillation dosimeters is to increase the light-collection efficiency at the coupling interfaces of the detector system. We performed a detailed study of surface preparation of scintillating fibers and their coupling with clear optical fibers to minimize light loss and increase the amount of light collected. We analyzed fiber-surface polishing with aluminum oxide sheets, coating fibers with magnesium oxide, and the use of eight different coupling agents (air, three optical gels, an optical curing agent, ultraviolet light, cyanoacrylate glue, and acetone). We prepared 10 scintillating fiber and clear optical fiber light guide samples to test different coupling methods. To test the coupling, we first cut both the scintillating fiber and the clear optical fiber. Then, we cleaned and polished both ends of both fibers. Finally, we coupled the scintillating fiber with the clear optical fiber in either a polyethylene jacket or a V-grooved support depending on the coupling agent used. To produce more light, we used an ultraviolet lamp to stimulate scintillation. A typical series of similar couplings showed a standard deviation in light-collection efficiency of 10%. This can be explained by differences in the surface preparation quality and alignment of the scintillating fiber with the clear optical fiber. Absence of surface polishing reduced the light collection by approximately 40%, and application of magnesium oxide on the proximal end of the scintillating fiber increased the amount of light collected from the optical fiber by approximately 39%. Of the coupling agents, we obtained the best results using one of the optical gels. Because a large amount of the light produced inside a scintillator is usually lost, better light-collection efficiency will result in improved sensitivity.

Artifacts↗

PubMedDate not supplied

Large-area contrast of a fiber-optic coupled x-ray image intensifier.

Large-area contrast measurements have been made upon a fiber-optic x-ray image intensifier with an external input phosphor. Both photometric and photographic techniques were used. For a shadowed area of 10% of the input window area, a contrast ratio in excess of 150 was determined. This is a factor of 5 higher than previously reported for any x-ray image intensifier. The improved contrast in the device is attributed to (1) reduced effect of x-ray Compton scattering in the input window; (2) less cross-chord light at the photocathode; and (3) greatly reduced light scattering and reflecting in output phosphor and window.

Fiber Optic Technology↗

PubMed2006

Measurement of high intensity focused ultrasound fields by a fiber optic probe hydrophone.

The acoustic fields of a high intensity focused ultrasound (HIFU) transducer operating either at its fundamental (1.1 MHz) or third harmonic (3.3 MHz) frequency were measured by a fiber optic probe hydrophone (FOPH). At 1.1 MHz when the electric power applied to the transducer was increased from 1.6 to 125 W, the peak positive/negative pressures at the focus were measured to be p(+) = 1.7-23.3 MPa and p(-) = -1.2(-) -10.0 MPa. The corresponding spatial-peak pulse-average (I(SPPA)) and spatial-average pulse-average (I(SAPA)) intensities were I(SPPA) =77-6000 W/cm2 and I(SAPA) = 35-4365 W/cm2. Nonlinear propagation with harmonics generation was dominant at high intensities, leading to a reduced -6 dB beam size (L x W) of the compressional wave (11.5 x 1.8-8.8 1.04 mm) but an increased beam size of the rarefactional wave (12.5 x 1.6-13.2 x 2.0 mm). Enhancement ratio of absorbed power density in water increased from 1.0 to 3.0. In comparison, the HIFU transducer working at 3.3 MHz produced higher peak pressures (p(+) = 3.0-35.1 MPa and p(-) = -2.5(-) - 13.8 MPa) with smaller beam size (0.5 x 4 mm). Overall, FOPH was found to be a convenient and reliable tool for HIFU exposimetry measurement.

Acoustics↗

PubMed2000

Intravascular ultrasound combined with Raman spectroscopy to localize and quantify cholesterol and calcium salts in atherosclerotic coronary arteries.

Coronary intravascular ultrasound (IVUS) can assess arterial wall architecture and localize large intravascular deposits, but it does not provide quantitative chemical information, which is essential in the evaluation of atherosclerotic lesions. Previously, it has been shown that Raman spectroscopy can be used to accurately quantify the relative weights of cholesterol, calcium salts, triglycerides, and phospholipids in homogenized arterial tissue. In the present study, we explore some benefits of combining IVUS and Raman spectroscopy to evaluate the intact arterial wall. IVUS images were collected in vitro from human coronary arterial segments in various stages of disease (n=7). The images were divided into radial segments (11 to 28 per image, 332 in total), each of which was classified visually as calcified or noncalcified tissue. The arteries were opened longitudinally, and Raman spectra were collected from locations at 0. 5-mm intervals across the arterial luminal circumference. The spectra were used to calculate the chemical composition of the arterial wall at the examined locations. Generally, locations containing large amounts of calcium salts, as determined with Raman spectroscopy, were classified as calcified with IVUS. However, small calcific deposits (<6% of weight) were not readily detected with IVUS. The amounts and location of cholesterol determined with Raman spectroscopy were correlated closely with the presence of cholesterol observed by histochemistry, but these deposits could not be located accurately by IVUS. The combination of Raman spectroscopy and IVUS applied in vitro provides detailed information about the amount and location of calcific deposits and lipid pools in atherosclerotic plaques. Future advances in optical fiber technology may allow simultaneous collection of Raman spectra and IVUS images through the same catheter in vivo.

Adult↗

PubMed1992

Laser recanalization of thrombosed arteries using thermal and/or modified optical probes; angiographic and angioscopic study.

The degree of residual stenosis by fresh thrombus after laser recanalization was compared by use of angiography and angioscopy. Fifteen NZW rabbits were used. Occlusive fresh thrombus in rabbit aorta was produced by mechanical deendothelialization and external constrictions simulating clinical situations. Argon laser angioplasty using microlens-tipped optical fiber and/or 2 mm hot-tip probe was done to recanalize thrombosed aorta in 10 animals. Two-mm hybrid probe was used in 5. Percent area stenosis (% AST) was derived by use of the mean radius method obtained by angiography of stenotic segments in two orthogonal views and/or from angioscopy. All 15 totally occluded vessels with fresh thrombus were recanalized. Four minor perforations occurred. Following argon laser angioplasty with the microlens optical fiber, percent stenosis was reduced to 53% in diameter by angiography and 66 in % AST by angioscopy, and to 48% and 55 respectively following hot-tip probe. After laser angioplasty with the hybrid probe, residual stenosis by fresh thrombus was 37% in diameter on angiography and 63 in % AST on angioscopy. Mean percent AST was 62% with angiography and 52% with angioscopy, and there was no correlation between them (r = -0.028). Angioscopy provided cross-sectional topographic views of thrombosed lumen and showed charring and shrinkage of thrombus following laser angioplasty. This study suggests that (1) continuous-wave laser angioplasty using modified optical fibers can recanalize thrombotic vascular occlusion, (2) laser angioplasty by hot-tip probe could evacuate fresh thrombus more than microlens fiber on angioscopy, and (3) angiographic % AST did not correlate with angioscopic % AST.

Angiography↗

PubMed2006

Surface-relief fiber Bragg gratings for sensing applications.

We present a new type of fiber Bragg grating (FBG) in which we etch the grating into the flat surface of a D-shaped optical fiber. Instead of being written in the core of the fiber, as are standard FBGs, these surface-relief FBGs are placed in the cladding above the core. These gratings are a viable alternative to standard FBGs for sensing applications. We describe the fabrication process for etching Bragg gratings into the surface of D-fibers and demonstrate their performance as temperature sensors.

Environmental Monitoring↗