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  • 1990-1994  (2)
  • 42.55 F  (1)
  • Magnetic resonance  (1)
  • 1
    ISSN: 1432-1084
    Keywords: Magnetic resonance ; Magnetic resonance-pulse sequences ; Magnetic resonance angiography ; Carotid arteries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three-dimensional (3D) time-of-flight methods are used to study anatomy and pathology of the supra-aortic arteries because they are quick and optimal for fast-flow conditions. Although highest signal intensities can be obtained by orientating the sections perpendicular to the long axis of the artery (axial), sagittal and/or coronal slice orientations cover the regions of interest with smaller volumes and therefore give adequate information in less time. Sagittal and coronal time-of-flight magnetic resonance angiography (MRA) gave excellent results (sensitivity 92.3%, specificity 85.7%, accuracy 90.9%) compared with intra-arterial digital subtraction angiography (DSA) in 30 patients, when coronal and sagittal acquisition were combined for final diagnosis. These values decreased to 69.6%/57.1%/66.7% for coronal and 83.6%/78.6%/81.7% for sagittal sections. Reasons for the variable extent of signal dropout at the site of a stenosis and for the different appearances of post-stenotic slow flow in the various planes are explained by T1 phenomena and intravoxel phase dispersion due to variable parameter settings.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 336-340 
    ISSN: 1432-0649
    Keywords: 34.80 D ; 41.80 Dd ; 42.55 F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In order to study the kinetic mechanism of the e-beam pumped Ar/Xe laser, the temporal profiles of individual laser lines during multiline oscillation have been measured as a function of power deposition (1–12MW/cm3) and gas laser pressure (2–14 bar) using a short pulse (30 ns) coaxial electron beam as excitation source. It was found that the optimum output energy at each pressure was obtained at the same specific power deposition. Strong line competition has been observed between the 2.65 and 1.73 μm transitions. In order to explain our results we suggest that besides electron collision mixing (ECM) between the 5d and 6p levels of Xe, there is also a redistribution between all 6p levels which strongly favours the lower levels at higher pumping densities.
    Type of Medium: Electronic Resource
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