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  • 1
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Computertomographie ; Lunge ; Niedrigdosis-CT ; Strahlenexposition ; Rundherd ; Key words Computed tomography ; Lung ; Low-Dose CT ; Radiation exposure ; Pulmonary nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Introduction. Computed tomography is a significant source of medical radiation exposure for populations in Europe. Reduced radiation exposure may be possible with modern CT scanners with an image quality that while less good than before remains acceptable for clinical purposes. The lung appears particularly well suited to investigation with low-dose CT owing to the high contrast between normal and diseased pulmonary parenchyma. Methods. We analysed the diagnostic accuracy of different low-dose CT protocols for the detection of pulmonary nodules using inflation-fixed isolated postmortem lung specimens in a chest phantom. In a comparative patient study diagnostic accuracies of standard-dose CT (120 kV, 250 mAs; slice thickness 10 mm, pitch 1) and low-dose CT (120 or 140 kV, 50 mAs; slice thickness 5 or 10 mm, pitch 1 or 2) were assessed. Results. Preliminary results suggest that low-dose CT protocols with radiation exposure of 10–20 % of that with standard-dose CT can reliably depict soft tissue density pulmonary nodules with a diameter of more than 5 mm and can also demonstrate smaller nodules equally well in many cases. Conclusions. Low-dose CT may frequently be an adequate imaging procedure in a given clinical setting, particularly in young patients with benign disease.
    Notes: Zusammenfassung Die Computertomographie (CT) trägt wesentlich zur medizinischen Strahlenexposition der Bevölkerung bei. Eine Reduktion dieser Strahlenexposition läßt sich vermutlich mit modernen CT-Geräten bei für viele Fragestellungen vertretbaren Einschränkungen der Bildqualität realisieren. Zur Untersuchung mittels solcher Niedrigdosis-CT (NDCT) erscheint die Lunge aufgrund der günstigen Kontrastverhältnisse des normalen und pathologischen Parenchyms besonders geeignet. Wir untersuchten die Treffsicherheit unterschiedlicher NDCT-Protokolle im Nachweis pulmonaler Rundherde an Lungenpräparaten in einem Thoraxphantom. In einer vergleichenden Patientenstudie wurde die Treffsicherheit der Spiral-CT des Thorax mit etablierten Parametern (120 kV, 250 mAs, Schichtdicke 10 mm, Pitch 1) mit derjenigen verschiedener NDCT-Protokolle (120 oder 140 kV, 50 mAs, Schichtdicke 5 oder 10 mm, Pitch 1 oder 2) verglichen. Vorläufige Ergebnisse zeigen, daß diese NDCT-Protokolle mit einer Dosis von 10 bis 20 % der Standard-Dosis CT weichteildichte Lungenrundherde mit einem Durchmesser von mehr als 5 mm zuverlässig nachweisen konnten und auch bei kleineren Rundherden häufig gleichwertig waren. Abhängig von der Fragestellung sollten derartige NDCT-Protokolle v. a. bei jungen Individuen mit benignen Erkrankungen auch in der klinischen Routine eingesetzt werden.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0509
    Keywords: Radiation exposure ; Endoscopic retrograde cholangiopancreatography ; Endoscopic papillotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Radiation exposure was studied in 327 patients undergoing endoscopic retrograde cholangiopancreatography, or endoscopic papillotomy taking into account fluoroscopy time and incident area exposure. The mean fluoroscopy time was 238±152 seconds and the incident area exposure 3,730±2,790 R×cm2. These results were compared with standard exposures in upper GI series and colon examinations as found in the literature.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: 42.55 ; 52.00 ; 34.80 ; 52.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A comprehensive experimental and theoretical study of the optimization of a continuous-wave radiofrequency (rf) excited CO2 waveguide laser is presented. The numerical simulation includes the modelling of the gas-discharge plasma parameters like the plasma impedance and energy deposition, the laser kinetics and finally the influence of the resonator feedback on the lasing process. Along with this theoretical study, an extensive experimental research program enabled us to optimize the laser performance of the CO2 waveguide laser. As a result, a total output power of 42 W and a specific output power of 1.1 W/cm were obtained.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0649
    Keywords: 42.55 ; 42.60 ; 52.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A radiofrequency excited atomic Xe slab laser with an active volume of 2 × 10 × 300 mm3 using a quartz envelope containing the laser-gas mixture shows a stable cw performance with an output power of almost 1 W. The free-running system oscillates, depending on gas composition and density, on several lines between 1.73 and 3.51 μm. Line competition phenomena are observed. Single-line oscillation yields more than 500 mW.
    Type of Medium: Electronic Resource
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