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309 records · Page 18Linked to original sources
PubMed2004

Radionuclide imaging of miniaturized chemical analysis systems.

We propose radionuclide imaging as a valuable tool for the study of molecular interactions in miniaturized systems for chemical analysis. Sensitive and quantitative imaging can be performed with compounds labeled with short-lived positron-emitting radionuclides, such as (11)C and (68)Ga, within selected parts of the system. Radionuclide imaging is not restricted to transparent materials since the relatively energetic positrons can penetrate high optical density materials. Experimentally, a radiotracer is introduced into the object of study, which is subsequently placed on a phosphor storage plate. After exposure, the plate is scanned with a laser and a digital, quantitative image can be reconstituted. To demonstrate the concept, three types of microstructures suited for integration in chemical analysis systems were imaged with (11)C- and (68)Ga-labeled tracers. The influence of factors such as geometry of the object and type of radionuclide on resolution and sensitivity was investigated. The resolution ranged from 0.9 to 2.7 mm (fwhm). Measuring low amounts of radioactivity in the three structures, 2-20 Bq could be detected, which corresponded to 2.3-500 amol or 2.4-110 pM tracer. The imaging approach was applied to study analyte concentration and sample dilution effects on the performance of a capillary extraction column integrated in an automated LC-ESI-MS system. The utility of the technique was further illustrated by imaging of microchannels in a zeonor plastic compact disk and in a poly(dimethylsiloxane) material for the study of nonspecific peptide adsorption.

Carbon Isotopes↗
PubMedDate not supplied

Line-scanning laser ophthalmoscope.

Scanning laser ophthalmoscopy (SLO) is a powerful imaging tool with specialized applications limited to research and ophthalmology clinics due in part to instrument size, cost, and complexity. Conversely, low-cost retinal imaging devices have limited capabilities in screening, detection, and diagnosis of diseases. To fill the niche between these two, a hand-held, nonmydriatic line-scanning laser ophthalmoscope (LSLO) is designed, constructed, and tested on normal human subjects. The LSLO has only one moving part and uses a novel optical approach to produce wide-field confocal fundus images. Imaging modes include multiwavelength illumination and live stereoscopic imaging with a split aperture. Image processing and display functions are controlled with two stacked prototype compact printed circuit boards. With near shot-noise limited performance, the digital LSLO camera requires low illumination power (<500 microW) at near-infrared wavelengths. The line-scanning principle of operation is examined in comparison to SLO and other imaging modes. The line-scanning approach produces high-contrast confocal images with nearly the same performance as a flying-spot SLO. The LSLO may significantly enhance SLO utility for routine use by ophthalmologists, optometrists, general practitioners, and also emergency medical personnel and technicians in the field for retinal disease detection and other diverse applications.

Computer-Aided Design↗
PubMed1985

[Automated and semiautomated perimetry. Comparative trial of 3 devices (Baylor programmer, Friedmann Mark II campimeter, Octopus 2000 R.)].

Modern perimetry involves automated or semi-automated procedures, this computer assisted perimetry (CAP) providing results independent of the examiner, and with marked discrimination of light sensibility through quantification of points tested. A wide variety of CAP devices are available, and a comparative study was conducted in 50 patients using 3 perimetric apparatuses with similar supraliminal static techniques but with variable automated potentials: The Goldman perimeter modified by "Baylor visual fields programmer": static technique for the middle area and kinetic for the peripheral area. The Friedmann Mark II Visual Fields Analyser with a multiple stimulus static technique for the middle area. The Fankhauser Octopus 2000 R perimeter with a precise static technique for middle and peripheral areas. This perimeter, highly automated, also allows statistical evaluation of defects changes, owing to storage of results on magnetic discs. Patients studied had either: glaucoma (25 cases) or neuro-ophthalmologic and retinal disorders (24 cases). Conclusions drawn from the experience acquired by the authors during more than one year of use of the 3 devices were: Rate of detection of defects is excellent with the Octopus and quite good with the Friedmann MKII, but limited in the middle area. The Baylor program does not allow quantification of defects. The image is clear with the Octopus as far as the gray scale is concerned, and more exact as far as the comparative tables are concerned; is not clear with the Friedmann MKII; is typical and clear with the Baylor. The length of examination (which varies with the programs used as far as the Octopus is concerned, and with the patient's reaction time) is usually long with the Octopus and the Friedmann, but short with the Baylor. Time and energy can be gained by the use of the Octopus, since it supplies data obtained from use of the Baylor program associated with that of the Friedmann MKII. The authors prefer to follow up campimetric evolution of glaucomatous patients with the Octopus because it offers more sensibility and precision in quantifying losses. The application of the statistical evaluation delta program on the 2000 R device, which will soon be tested in the Ophthalmological Department, could in an objective way indicate whether there is stabilization or a real progression of glaucomatous defects.

Adenoma↗