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  • 1
    Electronic Resource
    Electronic Resource
    Bradford : Emerald
    Compel 20 (2001), S. 665-675 
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We applied minimum norm estimations using different regularization techniques to the solution of the biomagnetic inverse field problem. Using magnetic field data measured with a multi-channel-SQUID-sensor-system we computed reconstruction of the impressed current density distributions which were generated by extended current sources placed inside a human torso phantom. The common inverse techniques usually applied in modern biomedical investigations in bioelectricity or biomagnetism are compared, and their aptitude for reconstruction of 3D current sources in space was evaluated. We analyzed the impact of using magnetic data, electrical data, and combination of both respectively on the localization of an equivalent current dipole (ECD). Finally, we use a visualization tool which enables a comparison of current density reconstruction. The study is, in parts, related to the new TEAM problem No. 31.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für Kardiologie 89 (2000), S. 630-637 
    ISSN: 1435-1285
    Keywords: Key words Heart rate variability ; respiratory arrhythmia ; sinus arrhythmia ; cardiorespiratory coupling ; Schlüsselwörter ; Herzfrequenzvariabilität ; respiratorische Arrhythmie ; Sinusarrhythmie ; kardiorespiratorische Kopplung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Variabilität von Regulationsgrößen des Herz-Kreislauf-Systems erlaubt Aussagen über die Prognose kardialer Erkrankungen. Die veränderte Variabilität einer Regulationsgröße führt zu Störungen in der Synchronisation interagierender Regelkreise. Die Quantifizierung dieser Störungen könnte Rückschlüsse auf die Schwere der zugrunde liegenden funktionellen Beeinträchtigung erlauben. Diese Studie untersucht die Synchronisation der Regelkreise von Herzfrequenz und Atmung (kardiorespiratorische Synchronisation, CRS) nach akutem Myokardinfarkt.    Es wurden 43 Patienten nach Myokardinfarkt und 27 Gesunde untersucht. Zur Quantifizierung der CRS wurde die Phasensynchronisation von Atemfrequenz und Herzfrequenz beurteilt. Ebenfalls wurden die Parameter der Herzfrequenzvariabilität (HRV) untersucht. Patienten nach Myokardinfarkt haben eine signifikant reduzierte HRV und CRS. Zwischen HRV und CRS besteht eine nichtlineare Abhängigkeit. Infarktpatienten mit linksventrikulärer Dilatation und eingeschränkter linksventrikulärer Pumpfunktion (EF≤45%) unterschieden sich in dieser Studie in der CRS, nicht aber in der HRV von den übrigen Infarktpatienten und Gesunden. Sie hatten eine ausgeprägte kardiorespiratorische Desynchronisation und konnten durch einen Schwellwert identifiziert werden.    Die CRS erfasst die Interaktionen von Herzfrequenz- und Atemregulation. Nach Myokardinfarkt kommt es zu einer Reduktion der HRV. Eine Desynchronisation der Regelkreise von Atmung und Herzfrequenz tritt offenbar insbesondere bei ausgedehnteren Myokardinfarkten ein. Dies kann mit der vorgestellten Methode quantifiziert werden.
    Notes: Summary The prognosis of cardiac diseases can be estimated from the variability of regulation parameters of the cardiovascular system. Changes in the variability of a regulation parameter causes disturbances in the synchronisation of interacting control loops. Conclusions about the severity of the underlying functional impairment can be drawn from these disturbances. This study investigates the synchronisation of the control loops of the heart rate and respiration (cardiorespiratory synchronisation, CRS) after acute myocardial infarction.    We investigated 43 patients after myocardial infarction and 27 healthy controls. To quantify the CRS the synchronisation in phase of respiration and heart rate was assessed. The heart rate variability (HRV) was also assessed. Patients after myocardial infarction have a significantly reduced HRV and CRS. There is a non-linear relationship between HRV and CRS. Patients with left ventricular enlargement and reduced left ventricular ejection fraction (≤45%) significantly differed from the other infarct patients and controls in CRS but not in HRV. They had a marked degree of cardiorespiratory desynchronisation and were identified by a threshold value.    CRS is a measure of the interaction of respiration control and heart rate control. After myocardial infarction, a reduction of the HRV can be observed. The desynchronisation of the control loops of respiration and heart rate especially appears in large infarcts. This can be quantitatively assessed by the method presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 9 (1996), S. 145-158 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: For the interpretation of human neuromagnetic data it is necessary to compute the magnetic field of a source (e.g. a dipole) in a volume conductor (e.g. a homogeneous conducting sphere or a homogeneous head model). The Multiple Multipole (MMP) method, which is a semianalytical field calculation method, is applied to neuromagnetic field calculation for the first time. The unique feature of the MMP method is that multipole expansions are used for the description of the electromagnetic field. First a validation of the MMP method is done with the help of a spherical model and an analytical solution. Then the MMP method is applied to a realistically shaped one compartment head model. The results are compared to results obtained with the Boundary Element Method (BEM). The results suggest that it is possible to solve the neuromagnetic forward problem faster with the help of the MMP method than with the conventional numerical field calculation methods for realistic shaped volume conductor models. Further investigations are necessary to tackle the inverse problem of biomagnetism with the MMP method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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