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Results for “Optical Devices”

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At least 19 recordsLinked to original sources
PubMed2000

Artificial neural networks as a method to improve the precision of subcutaneous adipose tissue thickness measurements by means of the optical device LIPOMETER.

The LIPOMETER is an optical device for measuring the thickness of a subcutaneous adipose tissue layer. It illuminates the interesting layer, measures the backscattered light signals and from these, it computes absolute values of subcutaneous adipose tissue layer thickness (in mm). Previously, these light pattern values were fitted by nonlinear regression analysis to absolute values provided by computed tomography. Nonlinear regression analysis might provide slight limitations for our problem: a selected curve type cannot be changed afterwards during the application of the measurement device. Artificial neural networks yield a more flexible approach to this fitting problem and might be able to refine the fitting results. In the present paper we compare nonlinear regression analysis with the behaviour of different architectures of multilayer feed forward neural networks trained by error back propagation. Specifically, we are interested whether neural networks are able to yield a better fit of the LIPOMETER light patterns to absolute subcutaneous adipose tissue layer thicknesses than the nonlinear regression techniques. Different architectures of these networks are able to surpass the best result of regression analysis in training and test, providing higher correlation coefficients, regression lines with absolute values obtained from computed tomography closer to the line of identity, decreased sums of absolute and squared deviations, and higher measurement agreement.

Adult↗
PubMed1976

[Peritoneoscopy with 2 optical devices: reduced risk - better diagnostic results (author's transl)].

Peritoneoscopy with 2 optical devices was performed in two cases; the technique of this procedure is described. The method allows inspection of areas, which cannot be seen during routine peritoneoscopy, especially of the anterior abdominal wall and of intraabdominal organs covered by adhesions. In addition, this method allows to find out, whether the anterior abdominal wall and vessels in it were injured by the troikart; the risk of the procedure is reduced thereby. Using a second optical device allows to visualize areas, which cannot be studied during routine peritoneoscopy because of intraabdominal adhesions. Thus better diagnostic results can be achieved with this method as compared to the routine technique.

Aged↗
PubMed2001

A comparison of patient reading performance and preference: optical devices, handheld CCTV (Innoventions Magni-Cam), or stand-mounted CCTV (Optelec Clearview or TSI Genie).

BACKGROUND: Clinicians frequently prescribe reading devices for low vision patients having a central field loss. This study seeks to provide comparative information the clinician can use to assist patients in selecting the most cost-effective device(s) for reading. METHOD: In this study we compared optical devices with two types of closed-circuit televisions (CCTVs) that differed in two important characteristics: price, and whether the camera was stand-mounted with an X-Y table or whether the camera was handheld. A "within-subjects" design was used with 22 subjects. The primary comparisons between devices were subject reading speed, duration, and preference. RESULTS: Subject reading speed and duration were significantly greater with the CCTV systems than with optical devices; however, no significant performance differences were found between the two types of CCTVs. Patients did express a clear preference for one versus the other type of CCTV, with an overall preference for the stand-mounted system. When asked to consider the price differential between types of CCTVs, patient preferences were about equally divided. CONCLUSIONS: Clinicians can expect significantly better initial reading performance for patients with central visual-field losses when reading with CCTVs versus optical devices. Handheld CCTVs, when compared with stand-mounted systems, are less expensive, provide equal performance, and have slightly lower subject preference ratings. The current study provides clinicians with objective performance data and subjective preference data that can be used to help patients with central visual-field losses select the most cost-effective reading device.

Aged↗
PubMed2000

Estimating percentage total body fat and determining subcutaneous adipose tissue distribution with a new noninvasive optical device LIPOMETER.

A newly developed optical device was applied to measure the subcutaneous adipose tissue (SAT) thickness of 20 healthy women and 18 healthy men at specified body sites. These measurements were used to derive equations to estimate percentage total body fat (TBF%). Total body electrical conductivity (TOBEC) was employed as a reference method; caliper techniques and measurements of absorbances of infrared light in fat versus lean tissue were also compared. The LIPOMETER results show good agreement with TOBEC data (r = 0.96). The technique allows the precise determination of the distribution of SAT thickness at specified body sites. The method also permits the construction of profiles of SAT thicknesses, e.g., the profiles are significantly different between women and men. Based on the normal profiles of healthy subjects, patients with proven type-2 diabetes mellitus were also evaluated. The patients showed significantly different profiles. By linear discriminant analysis, classification functions were extracted with good predictive accuracy classification of subjects according to the presence or absence of type-2 diabetes mellitus. The data suggest that measurement of SAT thickness might aid in the diagnosis and/or classification of metabolic disorders. Am. J. Hum. Biol. 12:221-230, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMed1992

Refinement of an optical device that stabilizes vision in patients with nystagmus.

An optical device that produces partial stabilization of retinal images has been described. It consists of a high-plus spectacle lens used in combination with a large, high-minus, polymethyl methacrylate (PMMA) contact lens. This device is designed to provide more clear and stable vision in patients with acquired nystagmus due to neurological disease. We report success in using a smaller, rigid, gas permeable (RGP) contact lens that achieves the required degree of stabilization, but is more comfortable for patients than the PMMA contact lens originally described. We have confirmed that the degree of retinal image stabilization is similar to that achieved with the PMMA lens. We present a case report to illustrate its use.

Adult↗
PubMed2003

La3Ga5SiQ14 single-crystal Q switch used as an electro-optic device.

A new kind of electro-optic Q switch is designed by use of a La3Ga5SiQ14 (LGS) crystal. Because the LGS crystal is optically active, the Q switch is based on the consideration that the total rotation angle of the polarization plane is zero, whereas the polarized wave propagates through the Pockels cell back and forth, with the polarization plane gyration and electro-optic effect existing simultaneously. The LGS Q switch is a practical electro-optic device that can be used in medium output energy lasers to partially take the place of deuterated potassium dihydrogen phosphate and lithium niobate Q switches.

Journal Article↗
PubMed2003

The effect of optical devices and repeated trials on the velocity of saccadic eye movements.

OBJECTIVE: The purpose of this prospective study was to analyze the effect of glasses and contact lenses on the latency and velocity of visually evoked saccadic eye movements. MATERIAL AND METHODS: A saccadic test was performed 10 times on 20 emmetropic controls (Group A) and 20 ametropic test subjects with myopia (Group B) who were using glasses (Subgroup Bg) or contact lenses (Subgroup Bc). RESULTS: No training or fatigue effect on either latency or eye velocity was registered. Regardless of visual acuity (Group A or B) or of the optical device used (Subgroup Bg or Bc), no significant intergroup difference in latency could ultimately be established. Subgroup Bc showed a significantly slower eye velocity than Group A. Regardless of the optical device used, subjects with a higher degree of myopia (> 6 D) showed a lower eye velocity than the Group A controls. Additionally, saccadic velocity was lower in this subgroup ( > 6 D) in subjects using contact lenses than in those using glasses. CONCLUSION: These results demonstrate that optical devices have an influence on the electronystagmographical analyses of the vestibulo-ocular reflex that must be taken into consideration, particularly in scientific investigations.

Adult↗
PubMedDate not supplied

[Method and optical device for exactly hinge axis localization tested on original phantom].

The quickly and exactly method of location of the hinge-axis is based on the moiré effect, produced between two superposed optical nets, one of it being moved. A face bow is fixed on the mandible to the occlusion rim. Two optical devices are mounted on the bottoms of the face bow. Two other optical nets are applied on the skin, corresponding to the TMJ. During the opening movements of the mandible when a pure rotation of the mandibular condiles take place on the TMJ, the optical nets are displaced and me exactly register the place corresponding to the rotation axe and we can note on the skin the hinge axis. The checkout was done using a phanthom achieved in our department, consisting of a skull made up of polyestheric resins and an elastic element made up of PVC.

Cephalometry↗
PubMedDate not supplied

[Light-optical device for fiber light guides].

The paper gives a calculation method for a lighting optical device consisting of light flux concentrator lamps rigidly installed in an ellipsoid reflector with heat-permeable coating, and the parameters of two big concentrator lamps for fibre endoscopes.

Endoscopes↗
PubMed1986

An infra-red fibre optic device for cardiac cycle timing and photoplethysmography.

In this work a simple fibre optic device using infra-red radiation is used to obtain information on the timing of the cardiac cycle and blood volume changes in the flow of blood in the body. The device is small, non-invasive and free from interference by surrounding electromagnetic fields enabling it to be used in the environment of such devices as NMR scanners.

Cardiography, Impedance↗
PubMedDate not supplied

[Examination of the patient with supraglottic carcinoma at the medical office. Contribution of the rigid optical devices and the fiberscope].

Seventy one patients afflicted of supraglottic carcinoma were included in a prospective study whose purpose was to determine which of three optical tools available at the medical office--indirect mirror laryngoscopy, laryngotelescopy and fiberscopic examination--is the most suitable to examine the larynx of patients with this disease. No significant differences were found among these explorations in the easily observable regions, as the hypopharyngeal areas and the epilarynx. The examination of the pericommisural region--the most difficult area to see--was easier with the flexible fiberscope. The laryngotelescope provided better visualization than the mirror laryngoscopy. Exploration with the new optical devices did not correct the errors in the interpretation of images made with the mirror laryngoscopy. We conclude that flexible fiberoptic laryngoscopy provides better information than other diagnostic tools for the assessment of patients with supraglottic carcinoma at the medical office.

Carcinoma, Squamous Cell↗
PubMed2004

Evaluation of a fibre optic device in solution equilibria studies. Application to 3-hydroxybenzoic acid ionization.

The use of a fibre optic device for spectrophotometric measurements in solution equilibria studies is presented. In particular the precision obtainable with such equipment is evaluated as a function of different experimental conditions, such as path length, averaging time and stirring of the solution. Analysis of 3-hydroxybenzoic acid ionization is presented to assess the results obtained in the study of an equilibrium system.

Fiber Optic Technology↗
PubMed2003

On-line monitoring of biofilm formation in a brewery water pipeline system with a fibre optical device.

Any advanced anti-fouling strategy must be based on early warning systems which allow for timely, precisely directed and optimized countermeasures. Such systems must be able to detect biofilm growth on representative surfaces. In order to meet this requirement, a fibre optical device (FOS) has been developed. It is based on light which is scattered by objects deposited on the tip of an optical fibre. A receiving fibre collects the signal and forwards it to a detection and quantification unit. Both the sending and the receiving fibre are mounted in a measuring head which is integrated evenly on the inner surface of a water pipeline at representative sites. This device was applied to a water system of a brewery in order toput its reliability to test under practical conditions. The FOS detected the build-up of a deposit which was identified independently as consisting of microorganisms, i.e., a biofilm. A stable, well detectable and reproducible signal could be obtained above a colonization of 10(5) cells cm-2. Adjustment of the sensitivity of the amplifier allowed for detection of biofilms up to 10(10) cells cm-2. Cleaning countermeasures could be detected clearly by a decrease of backscattered light intensity. The system proved to be suitable for on-line, non-destructive, real-time and automatic monitoring for a period of almost two years, and thus, provides an important constituent for an advanced anti-fouling strategy.

Automation↗