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At least 613 records · Page 34Linked to original sources
PubMed2005

Comparison of retinal nerve fibre layer measurements using optical coherence tomography versions 1 and 3 in eyes with band atrophy of the optic nerve and normal controls.

AIMS: To compare retinal nerve fibre layer (RNFL) measurements were carried out with two different versions of an optical coherence tomography device in patients with band atrophy (BA) of the optic nerve and in normal controls. METHODS: The RNFL of 36 eyes (18 with BA and 18 normals) was measured using an earlier version of an optical coherence tomography device (OCT-1). The measurements were repeated using a later version of the same equipment (OCT-3), and the two sets of measurements were compared. RESULTS: Using OCT-1, the peripapillary RNFL thickness (mean+/-SD, in microm) in eyes with BA measured 80.42+/-6.94, 99.81+/-14.00, 61.69+/-13.02, 101.70+/-12.54, and 57.36+/-16.52 corresponding to the total RNFL average, superior, temporal, inferior, and nasal quadrants, respectively. Using OCT-3, the corresponding measurements were 63.11+/-6.76, 81.22+/-13.34, 39.50+/-8.27, 86.72+/-15.16, and 45.05+/-8.03. Each of these measurements was significantly smaller with OCT-3 than with OCT-1. In normal eyes, RNFL average and temporal quadrant OCT-3 values were significantly smaller than OCT-1 values, but there was no significant difference in measurements from the superior, inferior, and nasal quadrant. CONCLUSIONS: RNFL measurements were smaller with OCT-3 than with OCT-1 for almost all parameters in eyes with BA and in the global average and temporal quadrant measurements in normal eyes. Investigators should be aware of this fact when comparing old RNFL measurement with values obtained with later versions of the equipment.

Adult↗
PubMed2003

"Stapled" bis(phthalocyaninato)niobium(IV), Pc2Nb: X-ray crystal structure, chemical and electrochemical behavior, and theoretical studies. Perspectives for the use of Pc2Nb (thin films) as an "optically passive electrode" in electrochromic devices.

Recrystallization of the previously reported monosolvated bis(phthalocyaninato)niobium(IV), [Pc2Nb].CINP (CINP = 1-chloronaphthalene), has allowed isolation of a single crystal of a new solvated form, i.e. [Pc2Nb]. 3.5CINP, whose structure has been elucidated by X-ray work: space group P2(1)/n (No. 14); a = 16.765(3), b = 23.800(4), c = 19.421(4) A; alpha = gamma = 90 degrees, beta = 92.51(2) degrees; Z = 4. The sandwiched material is a "stapled" molecule, characterized by the presence of two intramolecular interligand C-C sigma bonds and highly strained phthalocyanine units, as formerly observed by crystallographic work for its Ti(IV) analogue, [Pc2Ti], and the +1 corresponding fragment, [Pc2Nb]+, present in the species [Pc2Nb](l3)(l2)0.5.3.5CINP. [Pc2Nb] appears to be reluctant to undergo further oxidation above the +1 oxidation state. Detailed theoretical studies by DFT and TDDFT methods have been developed on [Pc2Nb] and [Pc2Nb]+, also extended for comparison to the Ti(IV) complex [Pc2Ti], and an adequate picture of the ground-state electronic structure of these species has been achieved. Moreover, the excitation energies and oscillator strengths calculated for the closed-shell systems, [Pc2Ti] and [Pc2Nb]+, provide a satisfactory interpretation of their characteristic visible optical spectra and help to rationalize the similar features observed in the visible spectrum of the open-shell "stapled" complex, [Pc2Nb]. Thin solid films (100-250 nm) of [Pc2Nb] deposited on ITO (indium-doped tin oxide) show a reversible redox process in neutral or acidic aqueous electrolytes. The electrochemical and electrochromic properties of the sandwiched complex, combined with impedance and UV/visible spectral measurements, are presented and discussed. The achieved electrochemical information, while substantially in keeping with the observed chemical redox behavior and theoretical predictions, qualifies [Pc2Nb] as an "optically passive" electrode and a promising material for its use in electrochromic devices.

Journal Article↗
PubMedDate not supplied

The relationship between elastomer opacity, colorimeter beam size, and measured colorimetric response.

The effect of opacity on the colorimetric responses of large-area and small-area colorimeters was determined using an elastomer intended for maxillofacial prosthetics use and containing various pigments at different concentrations. Opacity was determined by calculating the contrast ratio of 2-mm-thick specimens against black and white backings, using Kubelka-Munk analyses to correct for thickness and backing color variations. The measure of comparison of the two colorimeters was the relative difference in tristimulus reflectance, with the tristimulus reflectance of the large-area colorimeter as the basis of the relative difference. A significant quadratic relationship was found between contrast ratio and the relative difference in tristimulus reflectance. This relationship may be used to describe opacity without the need to make optical observations or measurements of a thin layer of material on contrasting backings. The small-area colorimeter produced color parameters that are a measure of the combined effects of both color and opacity. The importance of beam size considerations of optical measuring devices for translucent natural and prosthetic materials was emphasized.

Color↗
PubMed2001

[Evaluating the stability of fracture fixation systems: mechanical device for evaluation of 3-D stiffness in vitro].

Different fixation systems are used for fracture and defect treatment. A prerequisite for complication free healing is sufficient mechanical stability of the osteosynthesis. In vitro investigations offer the possibility of both analysing and assessing the pre-clinical fixation stability. Due to the complex loading environment in vivo, stiffness analysis should include a complete determination of the stiffness under standardised conditions. Based on a mathematical procedure to calculate the 3-D stiffness, a mechanical testing device for the 3-D loading of fixation systems was designed and integrated in the existing test set-up. The set-up consisted of a material testing machine to produce the necessary loads and an optical measurement device to detect the resulting inter-fragmentary movements. To validate the testing device, the 3-D stiffness matrices of different Ilizarov fixator configurations were determined and compared. The good reproducibility of the test was reflected in the small intra-individual variability of the stiffness components. A distinct direction dependence of the fixator stiffness was observed. Increasing the number of rings led to a stiffness increase of up to 50%, especially in bending. The presented testing device allows a complete standardised determination of the stiffness of different fixation systems. It considers the direction dependence of the stiffness and creates a prerequisite for a more direct implant comparison.

Biomechanical Phenomena↗
PubMed2001

Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices.

The fabrication and performance of an electrophoretic separation chip with integrated optical waveguides for absorption detection is presented. The device was fabricated on a silicon substrate by standard microfabrication techniques with the use of two photolithographic mask steps. The waveguides on the device were connected to optical fibers, which enabled alignment free operation due to the absence of free-space optics. A 750 microm long U-shaped detection cell was used to facilitate longitudinal absorption detection. To minimize geometrically induced band broadening at the turn in the U-cell, tapering of the separation channel from a width of 120 down to 30 microm was employed. Electrical insulation was achieved by a 13 microm thermally grown silicon dioxide between the silicon substrate and the channels. The breakdown voltage during operation of the chip was measured to 10.6 kV. A separation of 3.2 microM rhodamine 110, 8 microM 2,7-dichlorofluorescein, 10 microM fluorescein and 18 microM 5-carboxyfluorescein was demonstrated on the device using the detection cell for absorption measurements at 488 nm.

Electrophoresis, Capillary↗
PubMed1999

Disposable optical sensor chip for medical diagnostics: new ways in bioanalysis.

An optical sensor system is described which is particularly well suited for medical point-of-care diagnostics. The system allows for all kinds of immunochemical assay formats and consists of a disposable sensor chip and an optical readout device. The chip is built up from a ground and cover plate with in- and outlet and, between, of an adhesive film with a capillary aperture of 50 microns. The ground plate serves as a solid phase for the immobilization of biocomponents. In the readout device, an evanescent field is generated at the surface of the ground plate by total internal reflection of a laser beam. This field is used for the excitation of fluorophor markers. The generated fluorescence light is detected by a simple optical setup using a photomultiplier tube. Because of the evanescent field excitation, washing or separation steps can be avoided. With this system the pregnancy hormone chorionic gonadotropin (hCG) could be determined in human serum with a detection limit of 1 ng/mL. Recovery values were 86, 106, and 102% for 5, 50, and 100 ng/mL hCG, respectively. The SD in repeated measurements (n = 10) was 5.6%. Furthermore, the feasibility of the system in competitive-type immunoassays was demonstrated for serum theophylline. A linear calibration curve of signal vs theophylline between 1 and 50 mg/L was obtained. Recovery values varied between 118% (10 mg/L) and 81.0% (20 mg/L).

Biosensing Techniques↗
PubMedDate not supplied

A novel device for the non-invasive measurement of free hemoglobin in blood bags.

The production of red blood cell concentrates from human donors is a very expensive procedure and human resources are in short supply. Under perfect storage conditions at a temperature of 2-6 degrees C, a blood bag must be used within 35-49 days (in Germany). Visual inspection of the bag for apparent hemolysis by a blood bank physician is a crucial but subjective quality control assessment. Since an interruption of the cold chain cannot be definitely ruled out, bags are often disposed of prematurely for safety reasons. There is currently no method of testing a closed blood bag with respect to hemolysis for its suitability to be used in a transfusion. The proposed optical measuring device is a hemoglobin sensor which determines the free hemoglobin in standard erythrocyte concentrates without opening the bag. The optical measurements are done on the flexible tube connected to the main bag. The optical measurements were evaluated using standard hemoglobin solutions with an accuracy of 0.005 g/dL. These investigations show that in the future each blood bag can be tested non-invasively for its content of free hemoglobin. This will contribute to decreasing the wastage rate of red blood cell concentrates.

Blood Chemical Analysis↗
PubMed2004

Optical imaging of the heart.

Optical techniques have revolutionized the investigation of cardiac cellular physiology and advanced our understanding of basic mechanisms of electrical activity, calcium homeostasis, and metabolism. Although optical methods are widely accepted and have been at the forefront of scientific discoveries, they have been primarily applied at cellular and subcellular levels and considerably less to whole heart organ physiology. Numerous technical difficulties had to be overcome to dynamically map physiological processes in intact hearts by optical methods. Problems of contraction artifacts, cellular heterogeneities, spatial and temporal resolution, limitations of surface images, depth-of-field, and need for large fields of view (ranging from 2x2 mm2 to 3x3 cm2) have all led to the development of new devices and optical probes to monitor physiological parameters in intact hearts. This review aims to provide a critical overview of current approaches, their contributions to the field of cardiac electrophysiology, and future directions of various optical imaging modalities as applied to cardiac physiology at organ and tissue levels.

Action Potentials↗
PubMedDate not supplied

Comparison of an optical catheter office arthroscope with a standard rigid rod-lens arthroscope in the evaluation of the knee.

In a prospective, randomized study, 47 patients underwent arthroscopic evaluation of the knee in an operating room setting with both a standard rod-lens arthroscope and a newer flexible optical catheter fiberoptic system. The goal of the study was to assess the diagnostic accuracy of the newer catheter system, which is recommended for use in the office setting. Forty-four patients were included in the data analysis, three were eliminated because we were unable to perform an adequate examination with the catheter scope secondary to intraarticular adhesions or excessive bleeding. A comparison of the two systems revealed an overall underestimation and underrecognition of intraarticular knee pathologic changes. Anterior cruciate ligament tears were missed in 3 of 21 knees; no posterior cruciate ligament tears were detected by the rod-lens arthroscope in 44 knees, but one false-positive result was "seen" using the optical catheter device. Similar trends in diagnosis (sensitivity, 25% to 67%; specificity, 96% to 99%) were seen for tears of the medial and lateral menisci, chondral lesions, and the identification of loose bodies. We conclude from the results of this study that the use of the optical catheter system for arthroscopic evaluation and treatment of the knee in the office setting may result in a significant compromise in visual acuity, resulting in missed and incorrect diagnoses.

Anterior Cruciate Ligament Injuries↗
PubMed2005

[Devic's neuromyelitis optica in Morocco. A study of 9-cases].

INTRODUCTION: Optic neuromyelitis or Devic's syndrome associates optic neuritis and myelitis. It can have a monophasic or relapsing course. The limits of this entity remain controversial. METHODS: We analyzed the results of a retrospective series of Moroccan patients with Devic's syndrome defined on the basis of Wingerchuk's criteria. RESULTS: Six women and three men were retained for study; average age was 39 years. Three patients presented with a monophasic form and six with relapsing disease. CSF analysis was abnormal in five. Brain MRI was normal in eight. Signal abnormalities extended over more than three vertebrae in eight patients. Infections were associated with neurological features in half of the patients. DISCUSSION: Our results are in agreement with those of large series in the literature regarding the clinical, imaging, and laboratory findings and disease course. We also noted that infections were more frequently associated with Devic's syndrome in our patients. CONCLUSION: Our study reports the results of the first North African series of Devic's syndrome patients. We suggest that this syndrome is particular in our context due to the high frequency and diversity of associated infections.

Adult↗
PubMed2005

Resist-free patterning of surface architectures in polymer-based microanalytical devices.

The ability to form patterns of chemically reactive surface functionalities in microanalytical devices using a simple photopatterning approach without the need for photoresist-based methods is described. Direct UV exposure of the surfaces of poly(methyl methacrylate), PMMA, and poly(carbonate), PC, microfluidic devices through optical masks leads to the production of patterns of near monolayer quantities of surface carboxylic acid groups as determined by surface coverage, X-ray photoelectron spectroscopy, and fluorescence microscopy experiments. Formation of the reactive carboxylic acid groups without significant physical (topographical) damage to the polymer device substrates is achieved by use of low UV fluence and exposure times. Modification of the patterned, surface carboxylic acid groups with metals, thermally responsive polymers, and antibodies results in microfluidic devices possessing metallic interconnects and detection electrodes and the ability to capture intact biological cells and proteins from solution.

Methylmethacrylates↗
PubMed1995

A comparative optical analysis of laser side-firing devices: a guide to treatment.

OBJECTIVE: To compare the optical characteristics of five different laser side-firing fibres used to perform deep laser coagulation of the prostate. MATERIALS AND METHODS: The intensity profile, angle of exit and beam divergence from the launch fibre were measured underwater (to simulate endoscopic conditions) for each fibre using both the Helium Neon(633 nm) and Nd:YAG(1064 nm) lasers. RESULTS: The intensity profiles and spot sizes varied among fibres but broadly fell within two groups characterized by large and small footprints (low and high power density). There was a maximum 5.5 fold difference in average power densities between the fibres. CONCLUSIONS: Not all side-firing devices are the same. Variations in the power density profiles among the fibres suggest that the choice of fibre is of critical importance in determining the type of laser tissue interaction (i.e. coagulation or vaporization) that will follow the use of that fibre.

Laser Coagulation↗
PubMed2003

Catheter for diagnosis and therapy with infrared evanescent waves.

We have developed an optical delivery device (catheter) capable of transmitting broadband infrared light (IR wavelengths from 2 to 10 microm) for both diagnostic and therapeutic applications. The catheter is 1.68 mm in outer diameter and 1 m in length. It consists of two hollow glass waveguides coupled to a high-refractive-index optic tip. The IR light interacts with the tissue at the optic-tissue interface to measure the spectral signatures and perform therapy on the tissue at this interface. Fourier-transform IR spectrophotometer light is used to obtain the spectral signatures, and an IR free-electron laser (FEL) is used to study the therapeutic interaction of evanescent waves with the tissue. We present our catheter design; preliminary IR spectroscopy of aorta, blood, fatty tissue, and muscle; and IR FEL therapy on atheroslerotic aorta.

Absorption↗
PubMed2005

Comparison of anterior chamber depth in healthy myopic Thai eye using Orbscan and ultrasound.

OBJECTIVES: To compare the anterior chamber depth (ACD) using ultrasonic and optical measurements. MATERIAL AND METHOD: In this prospective study, ultrasound and optical (Orbscan) devices were employed to measure ACD in 42 eyes of 21 myopic volunteers. ACD values were compared using the paired-sample Student t test. The correlation of ACD values obtained from two groups was assessed by linear regression analysis. RESULTS: The difference of mean ACD values between the ultrasound (3.02 +/- 0.37 mm) and Orbscan (3.56 +/- 0.42 mm) method was statistically significant difference (p < 0.0001). CONCLUSION: The optical measurement of ACD in healthy myopic Thai eyes is, on average, 0.54 mm greater than ultrasonic measurement; however, both methods posses a significant linear correlation.

Adult↗
PubMed1997

Studies on the structure of sperm heads of Eledone cirrhosa by means of CLSM linked to bioimage-oriented devices.

We have used a confocal laser scanning optical microscope imaging device and a bioimage-oriented workstation equipped for augmented reality to study the helical sperm head of the octopus Eledone cirrhosa. This approach allows us to study different complex organisational motifs due to the spatial arrangement of linear helical structures. We consider this helical specimen an enlarged copy of one of the most important biostructures governing cell functioning such as chromatin-DNA. Moreover, this very same sample is made of highly compacted chromatin that can be studied at higher resolution, i.e., by means of scanning force microscopy. Fluorescence optical sectioning has been used to enter the spatial organisation. Three-dimensional images of single, twisted, and folded fibers are shown.

Animals↗
PubMed1993

Current status of infrared fiber optics for medical laser power delivery.

There are a host of fiber-optic delivery devices available for use with the Er:YAG, HF, CO, and CO2 lasers at 2.9, 2.8, 5.3, and 10.6 microns wavelengths, respectively. While many of these fibers are not as convenient to use as conventional silica fibers, they offer the ability to deliver infrared laser energy for a wide variety of medical applications. The fundamental attributes of fluoride glass, chalcogenide glass, single-crystal sapphire, and polycrystalline silver halide optical fibers are reviewed and their practical properties tabulated.

Fiber Optic Technology↗
PubMed1985

Visual performance and reading capacity of partially sighted persons in a rehabilitation center.

Visual acuity and reading performance of 178 partially sighted patients from a rehabilitation center were measured using a TV text display device. A linear relation was demonstrated between visual acuity and reading speed for patients with visual acuity values below 15% of the normal value. With respect to reading performance, three groups of partially sighted patients could be distinguished: (1) 25% of the patients are unable to read visually and require tactile reading aids; (2) 50% are partially sighted and require high-magnification electronic reading aids; (3) 25% can read normal text by using optical magnifying devices. There is evidence that reading performance is related to the nature of the underlying ocular problem, such as refractive anomalies, macular degeneration, or other diseases.

Adolescent↗
PubMed1999

Trocar and instrument positioning system TISKA. An assist device for endoscopic solo surgery.

The assistance received by the surgeon from support personnel during surgical laparoscopy is extremely important. This includes the retracting of instruments and the positioning of the endoscope. However, human assistance is costly and often does not provide satisfaction for the surgeon. The aim of the project was to develop a mechanical arm capable of manipulating a laparoscopic instrument under the control of the operating surgeon. The system design is based on a particular kinematic construction that maintains an invariant point of constraint motion coincident with the trocar puncture site through the abdominal wall. The guidance system allows transparent and intuitive operation, and its setup is easy and quick. It may be adapted either as an instrument retractor or as an optic positioning device. A new generation of instrument positioning systems, with improved ergonomy, will be a first step toward the diffusion of solo surgery techniques in minimally invasive therapy. We believe this prototype represents a valid compromise between human and robotic control for conventional laparoscopic instruments.

Animals↗