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  • 1
    Electronic Resource
    Electronic Resource
    Echo planar perfusion imaging with high spatial and temporal resolution: methodology and clinical aspects (1999)
    Springer
    European radiology 9 (1999), S. 221-229 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Perfusion-weighted MRI ; Cerebral perfusion ; Parameter images ; Cerebrovascular disease ; Brain tumours
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of the present study was to analyse specific advantages of calculated parameter images and their limitations using an optimized echo-planar imaging (EPI) technique with high spatial and temporal resolution. Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) was performed in 12 patients with cerebrovascular disease and in 13 patients with brain tumours. For MR imaging of cerebral perfusion an EPI sequence was developed which provides a temporal resolution of 0.68 s for three slices with a 128 × 128 image matrix. To evaluate DSC-MRI, the following parameter images were calculated pixelwise: (1) Maximum signal reduction (MSR); (2) maximum signal difference (ΔSR); (3) time-to-peak (Tp); and (4) integral of signal-intensity-time curve until Tp (SInt). The MSR maps were superior in the detection of acute infarctions and ΔSR maps in the delineation of vasogenic brain oedema. The time-to-peak (Tp) maps seemed to be highly sensitive in the detection of poststenotic malperfused brain areas (sensitivity 90 %). Hyperperfused areas of brain tumours were detectable down to a diameter of 1 cm with high sensitivity ( 〉 90 %). Distinct clinical and neuroradiological conditions revealed different suitabilities for the parameter images. The time-to-peak (Tp) maps may be an important advantage in the detection of poststenotic “areas at risk”, due to an improved temporal resolution using an EPI technique. With regard to spatial resolution, a matrix size of 128 × 128 is sufficient for all clinical conditions. According to our results, a further increase in matrix size would not improve the spatial resolution in DSC-MRI, since the degree of the vascularization of lesions and the susceptibility effect itself seem to be the limiting factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050659
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions of adaptation and masking in the guinea pig cochlea (1982)
    Springer
    European archives of oto-rhino-laryngology and head & neck 234 (1982), S. 197-202 
    Details
    ISSN: 1434-4726
    Keywords: Cochlear adaptation ; Pattern stimulation ; Preceding tone bursts ; Variable frequencies ; Delay time ; Additional adaptation ; Masking ; Summating potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fast cochlear adaptation and masking phenomena, expressed as percent inhibition of the summed action potential, are studied from the guinea pig cochlea responses to click trains and tone bursts given previously or simultaneously to the click sequence. After preceding tone bursts, the click responses are superposed by inhibitory aftereffects dependent on the tone frequency. With interposed tone bursts, the click sequence response is masked, dependent on tone frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00453631
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Cochlear responses to dynamic click patterns in the guinea pig (1981)
    Springer
    European archives of oto-rhino-laryngology and head & neck 230 (1981), S. 229-235 
    Details
    ISSN: 1434-4726
    Keywords: Cochlear adaptation ; Pattern stimulation ; Summed action potential ; Dynamical responses ; Rate sensitivity ; Inhibition ; Facilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Fast cochlear adaptation, expressed as percent inhibition of the summed action potential, is studied from the guinea pig cochlea responses to click trains, ramps, and steps in both directions. The transition time function of adaptation to constant click trains does not depend on click strength, but rather on click interval. On the background of steady state adaptation, click steps produce only transient changes of the adaptive state, opposite to step direction. Compared to constant train stimulation, adaptation is enhanced by descending click ramps, and diminished or reversed (near threshold) by ascending ramps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456323
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    Paper (German National Licenses)
    Fulltext
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