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Results for “Fiber Optic Technology”

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At least 127 records · Page 7Linked to original sources
PubMed1986

The temporal use of diagnostic tests of the colon: some results for fee-for-service medicine in Australia.

In the context of rising health expenditures it is relevant to consider the behavior of those who, in large part, determine what medical procedures are performed on patients. The purpose of this paper is to describe the utilization of diagnostic tests of the colon in Australia. The study is restricted to private medical practitioners operating on a fee-for-service basis. Diagnosis of the gastrointestinal tract is of some interest because the new technology of fiber optic endoscopy has provided an alternative means of diagnosing diseases or conditions. The results presented here indicate rising per capita utilization rates for both the "new" technology and the "old" techniques of barium enema radiology and sigmoidoscopy. There is no evidence of the "new" technology displacing the "old" in terms of per capita use. The data may be consistent with the hypothesis that process innovations in medicine do not displace alternative products: rather they are "added on" to the existing products.

Australia↗
PubMed1994

The J. Otto Lottes Health Sciences Library and the Microcomputer Learning Laboratory.

Opened in 1985, the J. Otto Lottes Health Sciences Library at the University of Missouri-Columbia has adapted to changes in information technology by installing a fiber optic backbone, establishing local area networks and file servers with databases and software programs, establishing a microcomputer learning laboratory, and responding to the needs of a problem-based learning curriculum. The library works cooperatively with the Medical Informatics Group, which is housed in the library and runs the micro laboratory, to support student and faculty computing.

CD-ROM↗
PubMed2006

Mass-balanced blend uniformity analysis of pharmaceutical powders by at-line near-infrared spectroscopy with a fiber-optic probe.

A near-infrared (NIR) fiber-optic probe was used at-line to study the blending dynamics of pharmaceutical powder blends on a mass-balanced basis. The probe with a flexible fiber-optic cable can be inserted directly into a 10-L bin blender to get quantitative readings. NIR calibration models were developed and validated for the probe based on a designed 50-sample calibration set. A model formulation containing acetaminophen, mannitol, Avicel, magnesium stearate and AcDiSol was used in the study. The blending study was conducted at 18 rpm for 20 min. NIR probe scans were performed at 1 min intervals and five different locations in the bin. Thief samples were collected and later analyzed by a bench-top NIR instrument to confirm the results from the probe. Complete blending profiles were constructed and compared based on the assay results from both instruments.

Acetaminophen↗
PubMed1987

Fiber-optic chemical sensors (Gas-Stat) for blood gas monitoring during hypothermic extracorporeal circulation.

Measurements of pO2, pCO2 and pH by optical fluorescence microsensing technology has recently become available for monitoring blood gases during extracorporeal circulation ECC). We have compared simultaneous measurements with fiber-optic sensors (Gas-Stat, Bentley) and electrochemical sensors (ABL-4, Radiometer) on discrete samples. In 10 patients undergoing coronary artery bypass grafting during hypothermic (25 degrees C) ECC and hemodilution (hemoglobin concentration 4 mmol.l-1) arterial and venous pO2, pCO2 and pH were measured in-line in the extracorporeal circuit at the actual blood temperature. Simultaneous and anaerobically collected blood samples in glass syringes were analyzed within five minutes at 37 degrees C in the ABL-4. Linear regression analysis of the values at actual temperature shows the following equations: Gas-Stat = Y, ABL-4 = X: pO2 (kPa): Y = 1.04 X + 0.5 r = 0.95 n = 136; pCO2 (kPa): Y = 0.71 X + 1.5 r = 0.79 n = 136; pH: Y = 0.788 X + 1.590 r = 0.76 n = 136. The advantage of the Gas-Stat is continuous monitoring of blood gas parameters during ECC. The present study shows that measurements of pO2, pCO2 and pH with fiber-optic chemical sensors may be reliable. The differences between the two principles of measurement may be due to unknown factors interfering with the in-line measurements or to variations in sensitivity and stability of the individual sensor.

Blood Gas Analysis↗
PubMed1987

Spectrophotometry in vivo, a technique for local and direct enzymatic assays: application to brain acetylcholinesterase.

In vivo enzymology is not widely studied due to the lack of a well-adapted technology. We have developed a system that allows local and long-term spectrophotometric assays in brain tissue of live animals. It utilizes a miniaturized optical probe consisting of a multibarrel micropipette for reagent injections and optical fibers for light absorption measurements. We have applied this system to the colorimetric determination of brain acetylcholinesterase activity in rats. The reproducibility of the assay was demonstrated by repetitive assays over 24 hr, its specificity was established through the use of a highly specific organophosphorus inhibitor, and the activities measured in different brain areas agreed with the known distribution of acetylcholinesterase. No electroencephalographic abnormalities and no change in vigilance level were observed in the experimental animals. This methodology should prove to be useful for the colorimetric measurement of different enzymes or metabolites in various organs.

Acetylcholinesterase↗
PubMed1999

Micromachining in plastics using X-ray lithography for the fabrication of microelectrophoresis devices.

Micromachining was performed in polymethylmethacrylate (PMMA) using X-ray lithography for the fabrication of miniaturized devices (microchips) for potential applications in chemical and genetic analyses. The devices were fabricated using two different techniques: transfer mask technology and a Kapton mask. For both processes, the channel topography was transferred (1:1) to the appropriate substrate via the use of an optical mask. In the case of the transfer mask technique, the PMMA substrate was coated with a positive photoresist and a thin Au/Cr plating base. Following UV exposure, the resist was developed and a thick overlayer (approximately 3 microns) of Au electroplated onto the PMMA substrate only where the resist was removed, which acted as an absorber of the X-rays. In the other technique, a Kapton film was used as the X-ray mask. In this case, the Kapton film was UV exposed using the optical mask to define the channel topography and following development of the resist, a thick Au overlayer (8 microns) was electrodeposited onto the Kapton sheet. The PMMA wafer during X-ray exposure was situated directly underneath the Kapton mask. In both cases, the PMMA wafer was exposed to soft X-rays and developed to remove the exposed PMMA. The resulting channels were found to be 20 microns in width (determined by optical mask) with channel depths of approximately 50 microns (determined by x-ray exposure time). In order to demonstrate the utility of this micromachining process, several components were fabricated in PMMA including capillary/chip connectors, injectors for fixed-volume sample introduction, separation channels for electrophoresis and integrated fiber optic fluorescence detectors. These components could be integrated into a single device to assemble a system appropriate for the rapid analysis of various targets.

Electrophoresis, Capillary↗
PubMed1999

Some factors affecting enantiomeric impurity determination by capillary electrophoresis using ultraviolet and laser-induced fluorescence detection.

The key factors influencing enantiomer trace determination were investigated; these include resolution capillary diameter, limit of detection, linear range and type of detection. Chiral reagents, (+)- and (-)-1-(9-fluorenyl)ethyl chloroformate (FLEC), were employed as probes to demonstrate the influence of the variables. In order to find the best resolution, separation variables were optimized in both capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) modes by the application of factorial design experiments. A highly efficient chiral separation of the (+/-)-FLEC, derivatized with nonchiral amino acids, was achieved when using gamma-cyclodextrin as the chiral selector. The benefits of using a small diameter capillary for direct determination of both (+) and (-)-FLEC impurity (0.05-0.1% area/area) were demonstrated using UV detection and applying a sample stacking condition. A frequency-doubled argon ion laser (244 nm) was used as light source for laser-induced fluorescence (LIF) detection. Excitation light was provided by means of an optical fiber directed into the Hewlett Packard 3D capillary cartridge. The signals from UV and LIF were monitored simultaneously. The application of LIF detection greatly improved sensitivity and linear range. Further, as a consequence of the increased sensitivity, sample loading could be decreased, which led to an improvement of separation efficiency. Direct determination of 0.005% impurity could be achieved within the linear range.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2002

Feasibility study of a fiber-optic system for invasive blood pressure measurements.

A comparative study was conducted to evaluate the feasibility of a fiber-optic sensor in invasive blood pressure measurements. Static and wide-bandwidth stimuli were offered to the fiber-optic, Millar, Baxter, and Sentron devices to measure static transfer function and transient response. Animal experiments focused on offset drift, dynamic accuracy, and electromagnetic sensitivity. Compared to the Millar, Sentron, and Baxter devices, the fiber-optic sensor had a near-identical static transfer function. Gain and offset errors were < 3.4% and < 0.25%, respectively. Hysteresis nonlinearity was < 0.1%. The dynamic accuracy of the fiber-optic system matched that of the Millar and Sentron systems. Time delay was < 1 msec. Maximum rate of change was > 30,000 mm Hg/sec and bandwidth was 0-150 Hz minimum. Offset drift was 0.6 +/- 0.03 mm Hg. Application of diathermy highlighted the fiber-optic sensor's excellent electromagnetic disturbance rejection. The fiber-optic system appears to be a reliable, high-fidelity pressure monitor in demanding clinical environments.

Animals↗
PubMed1986

Intravascular blood velocity in simulated coronary artery stenoses.

The profiles of blood velocity within arterial stenoses have been measured using fiber optic laser Doppler anemometry (FOLDA). The arterial stenoses were created in arteries and tubes of similar size to human coronary arteries and were perfused in vitro at pressures and flows typical of those in the human circulation. At very low flow rates, flow and peak velocity are linearly related, and thus peak velocity measurement can predict internal cross-sectional areas accurately. With higher flow rates, the intravascular velocities are not linearly related to flow and cannot be used to measure internal cross-sectional area. This is due to flattening of the velocity profile at both more severe stenoses and higher flow rates.

Blood Flow Velocity↗
PubMed2002

Nanobiosensors: probing the sanctuary of individual living cells.

Recently, nanotechnology has been revolutionizing important areas in molecular biology, especially diagnostics and therapy at the molecular and cellular level. The combination of nanotechnology, biology, and photonics opens the possibility of detecting and manipulating atoms and molecules using nanodevices, which have the potential for a wide variety of medical uses at the cellular level. The nanoprobes were fabricated with optical fibers pulled down to tips with distal ends having sizes of approximately 30-50 nm. The nanoscale size of this new class of sensors, allows for measurements in the smallest of environments. One such environment that has evoked a great deal of interest is that of individual cells. Using these nanobiosensors, it has become possible to probe individual chemical species in specific locations throughout a cell. This article provides an overview of the principle, development, and applications of optical nanosensor systems for in vivo bioanalysis at the single-cell level. The fiberoptics nanoprobes were covalently bound with antibodies that are selective to target analyte molecules. Excitation light is launched into the fiber and the resulting evanescent field at the tip of the fiber is used to excite target molecules bound to the antibody molecules. The fluorescence emission from the analyte molecules is then collected via a microscope. The usefulness and potential of this nanotechnology-based biosensor systems in biological research and applications in single-cell analysis are discussed.

Biosensing Techniques↗
PubMed2004

Performance evaluation of cylindrical fiber optic light diffusers for biomedical applications.

BACKGROUND AND OBJECTIVES: Dosimetry for intracavity and interstitial light delivery requires next to the knowledge of tissue optical properties and models describing light propagation in tissue also exact knowledge of the spatial light source emission characteristics. However, the emission characteristics of cylindrical diffusers are often ill defined by the manufacturer, and not regularly determined by the end user, thus limiting the attainable dosimetry accuracy. STUDY DESIGN/MATERIALS AND METHODS: Commercial cylindrical diffusers, with active diffusive lengths of 1-2 cm and outer diameters of </=1 mm, were evaluated regarding their photometric emission characteristics. In addition to traditional tests of homogeneity such as light intensity emitted along the diffuser length and around its circumference (polar angle), azimuth emission was also measured. RESULTS: It was demonstrated that the light emission distribution is specific to the diffuser manufacturer, and while good polar isotropy is often attained, azimuth isotropy can vary by more than a factor of 5. In hollow organs the latter can result in over treatment of tissue distal to the actual placement of the cylindrical diffusers. CONCLUSIONS: To enable light dosimetry and treatment planning for applications such as photodynamic therapy or interstitial laser hyperthermia or photocoagulation, standardization of emission properties reporting for optical fiber diffusers is required.

Equipment Design↗
PubMed1990

A laser Doppler catheter for monitoring both phasic and mean coronary vein flow.

A new catheter-type laser Doppler velocimeter has been developed to monitor coronary vein flow. A thin graded-index multimode optical fiber (outer diameter of 125 microns) is set inside a 5-F catheter, and eight elastic silicon rubber spikes are arranged radially toward the vessel wall to fix the catheter tip in or near the axial region of the coronary vein. He-Ne laser light (wave length = 632.8nm) is introduced into the blood through the optical fiber, and reflected light is collected by the same fiber. The Doppler signal is detected by a spectrum analyzer. To avoid any effect by the spikes on flow, the fiber is extended from the catheter tip by 3 mm at the time of measurement. Straight and curved tubing was used to examine the accuracy of flow measurement. The flow velocities recorded by the catheter, which were measured by an electromagnetic flowmeter, exhibited excellent linearity (r = straight; 0.982, curved: 0.996). The blood flow velocity in the great cardiac vein was measured by this method in five dogs. The predominantly systolic waveform, which is a characteristic of the coronary vein flow, was observed in all of the dogs. The great cardiac vein velocity increased around the beginning of the ventricular ejection and decreased gradually after the peak formation at mid- or end-diastole. In addition to this main peak, small flow components were frequently observed during isovolumic contraction and the atrial contraction phase, although these flow components varied in individual dogs. Following left anterior descending artery occlusion, the great cardiac vein flow velocity decreased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Measurement of point velocity in the canine coronary artery by laser Doppler velocimeter with optical fiber.

A laser Doppler velocimeter with an optical fiber was developed to investigate point blood velocity in the arteries and was applied to the measurement of blood velocity in the canine coronary artery. Fundamental experiments revealed that the accuracy of this method was satisfactory, since an excellent linear relation was found between the known blood velocity and the Doppler shift frequency (r = 0.998). The fiber tip (0.1 mm diam.) was inserted into the proximal portion of the left circumflex coronary artery and was traversed across the vascular lumen to measure the point velocity at each sampling point. Detailed velocity profiles were than reconstructed sequentially in three dimensional coordinates, i.e., velocity, diameter and time. In general the velocity waveform showed a diastolic dominant pattern which is characteristic of coronary arterial flow. One peak in early systole and two peaks in early and in late diastole were commonly observed in the velocity waveform near the center-line of the vessel. The velocity profiles were flat in the axial region and declined abruptly near the vessel wall. These results indicate that the laser Doppler velocimetry with an optimal fiber proved to be an accurate and feasible method of evaluating the point velocity of coronary artery flow.

Animals↗
PubMed1975

Transillumination of the angular and frontal veins.

A 500-W fiber optics cold light used to transilluminate the angular and frontal veins allowed quick, accurate delineation of the veins for percutaneous orbital venography. It also allowed the surgeon to avoid cutting the angular vein when operating on the lacrimal sac.

Face↗
PubMed1982

Retinal irradiance from vitrectomy endoilluminators.

We compared the maximum light output of selected 19- and 20-gauge continuous-fiber and detachable-tip endoilluminators to the retinal damage threshold for intravitreal fiber-optic light in the owl monkey. Because of cumulative light toxicity to the retina there is a substantial risk of retinal damage from endoillumination when the endoilluminator is close to the retina (for example, during membrane peeling procedures) and especially when the continuous-fiber endoilluminator with high light output is used.

Animals↗
PubMed1990

A comparison of new and conventional methods for quantification of tooth color.

Tooth color is caused by volume reflection, that is, passage of incident light through the tooth followed by backward emergence. This passage is concurrent with sideward displacement of photons that, in effect, influences the result of usual instrumental methods of determining tooth color. This problem is overcome by the use of large-field illumination and small-field observation. A fiber-optics colorimeter based on this principle is described. The color observed through two holes in a double box was visually matched by subtractive adjustment of the illuminating color in one box, whereas the other box showed the central part of the tooth diffusely illuminated by illuminant C light. This colorimeter was tested on wet, extracted human incisors in the tooth arch of a phantom-head. Results were compared with a visual standard-strip method described previously and with a conventional spectrophotometer. It was concluded that the fiber-optics colorimeter is a promising instrument, although technical improvement is necessary.

Acrylic Resins↗
PubMed1994

Stimulation in the rat of a nerve fiber bundle by a short UV pulse from an excimer laser.

A bundle of central nervous fibers was excited in the rat with a short pulse (40 ns) of UV light produced by an excimer laser. Evoked responses were recorded in the thalamic ventralis posterior nucleus after stimulation of the medial lemniscus or the cuneate bundle in the spinal cord. The effects of electrical and optical fiber applied UV stimulation were compared in both cases. At threshold, the latency for the UV light stimulation was slightly longer than for electrical stimulation. The excitation threshold was 0.9 J/cm2, very close to the UV photoablation threshold (order of 1 J/cm2). The intermediary events mediating the light excitation are discussed.

Afferent Pathways↗