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  • 1
    Electronic Resource
    Electronic Resource
    Gene therapy for glioblestome multiforme: in vivo tumor transduction with the herpes simplex thymidine kinase gene followed by ganciclovir (1997)
    Springer
    Journal of molecular medicine 75 (1997), S. 300-304 
    Details
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001090050116
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Stereotaktische Behandlung der Bewegungsstörungen (1997)
    Springer
    Der Nervenarzt 68 (1997), S. 477-484 
    Details
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Bewegungsstörungen ; M. Parkinson ; Stereotaxie ; Tremor ; Hirnstimulation ; Key words Stereotactic surgery ; Parkinson’s disease ; Movement disorders ; Thalamotomy ; Pallidotomy ; Brain ; Stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Stereotactic surgery for movement disorders is currently undergoing a re-evaluation. A new understanding of the pathophysiology makes the surgical lesion a logical step for the aleviation of both hyperkinetic symptoms such as tremor and hypokinetic symptoms like bradykinesia. Advances in imaging and electrophysiological control render these procedures more accurate and safer. Indications are medically refractory, Parkinsonean tremor, essential tremor, cerebellar tremor, bradykinesia and L-Dopa induced dyskinesis. The standard procedure is ablative surgery, i.e. thalamotomy for tremors and pallidotomy for bradykinesia, dystonia and L-Dopa induced dyskinesias. Deep brain stimulation is a novel alternative for selected patients which is currently evaluated. Neural transplantation of autologus, fetal or genetically manipulated cell suspensions into the striatum for the time being is experimental.
    Notes: Zusammenfassung Die chirurgische, d.h. stereotaktische Behandlung von Bewegungsstörungen erfährt derzeit eine Neubewertung. Neue Einsichten in die Pathophysiologie der Bewegungsstörungen haben dazu geführt, daß der stereotaktische Eingriff als begründeter therapeutischer Schritt angesehen wird. Die Nebenwirkungen stereotaktischer Eingriffe sind durch neue operative Techniken, digitale Bildgebung und elektrophysiologische Kontrollen geringer geworden. Die hauptsächlichen Indikationen sind Parkinson-Tremor und Rigidität, essentieller Tremor und zerebellärer Tremor. Als etablierte Routinemethode wird die stereotaktische Elektrokoagulation im Thalamus für alle Tremorformen weiterhin bevorzugt. Für die Behandlung von Akinesie und Bradykinesie, besonders auch der Dopa-induzierten Hyperkinesien, gewinnt die Pallidotomie rasch wieder an Bedeutung. Die chronische Stimulation durch Implantation von Hirnelektroden ist in Einzelfällen indiziert. Die Transplantation autologer, fetaler oder gentechnisch manipulierter Zellen wird derzeit in ihrer Bedeutung für die Therapie untersucht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001150050150
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Use of scanner characteristics in iterative image reconstruction for high-resolution positron emission tomography studies of small animals (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 779-786 
    Details
    ISSN: 1619-7089
    Keywords: Key words: Positron emission tomography ; Spatial resolution ; Image restoration ; Animal studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this work was to improve of the spatial resolution of a whole-body positron emission tomography (PET) system for experimental studies of small animals by incorporation of scanner characteristics into the process of iterative image reconstruction. The image-forming characteristics of the PET camera were characterized by a spatially variant line-spread function (LSF), which was determined from 49 activated copper-64 line sources positioned over a field of view (FOV) of 21.0 cm. This information was used to model the image degradation process. During the course of iterative image reconstruction, the forward projection of the estimated image was blurred with the LSF at each iteration step before the estimated projections were compared with the measured projections. The imaging characteristics of the high-resolution algorithm were investigated in phantom experiments. Moreover, imaging studies of a rat and two nude mice were performed to evaluate the imaging properties of our approach in vivo. The spatial resolution of the scanner perpendicular to the direction of projection could be approximated by a one-dimensional Gaussian-shaped LSF with a full-width at half-maximum increasing from 6.5 mm at the centre to 6.7 mm at a radial distance of 10.5 cm. The incorporation of this blurring kernel into the iteration formula resulted in a significantly improved spatial resolution of about 3.9 mm over the examined FOV. As demonstrated by the phantom and the animal experiments, the high-resolution algorithm not only led to a better contrast resolution in the reconstructed emission scans but also improved the accuracy for quantitating activity concentrations in small tissue structures without leading to an amplification of image noise or image mottle. The presented data-handling strategy incorporates the image restoration step directly into the process of algebraic image reconstruction and obviates the need for ill-conditioned ”deconvolution” procedures to be performed on the projections or on the reconstructed image. In our experience, the proposed algorithm is of special interest in experimental studies of small animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879667
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Use of scanner characteristics in iterative image reconstruction for high-resolution positron emission tomography studies of small animals (1997)
    Springer
    European journal of nuclear medicine 24 (1997), S. 779-786 
    Details
    ISSN: 1619-7089
    Keywords: Positron emission tomography ; Spatial resolution ; Image restoration ; Animal studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this work was to improve of the spatial resolution of a whole-body positron emission tomography (PET) system for experimental studies of small animals by incorporation of scanner characteristics into the process of iterative image reconstruction. The image-forming characteristics of the PET camera were characterized by a spatially variant line-spread function (LSF), which was determined from 49 activated copper-64 line sources positioned over a field of view (FOV) of 21.0 cm. This information was used to model the image degradation process. During the course of iterative image reconstruction, the forward projection of the estimated image was blurred with the LSF at each iteration step before the estimated projections were compared with the measured projections. The imaging characteristics of the high-resolution algorithm were investigated in phantom experiments. Moreover, imaging studies of a rat and two nude mice were performed to evaluate the imaging properties of our approach in vivo. The spatial resolution of the scanner perpendicular to the direction of projection could be approximated by a one-dimensional Gaussian-shaped LSF with a full-width at half-maximum increasing from 6.5 mm at the centre to 6.7 mm at a radial distance of 10.5 cm. The incorporation of this blurring kernel into the iteration formula resulted in a significantly improved spatial resolution of about 3.9 mm over the examined FOV As demonstrated by the phantom and the animal experiments, the high-resolution algorithm not only led to a better contrast resolution in the reconstructed emission scans but also improved the accuracy for quantitating activity concentrations in small tissue structures without leading to an amplification of image noise or image mottle. The presented data-handling strategy incorporates the image restoration step directly into the process of algebraic image reconstruction and obviates the need for ill-conditioned ”deconvolution“ procedures to be performed on the projections or on the reconstructed image. In our experience, the proposed algorithm is of special interest in experimental studies of small animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879667
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Experimental evidence of crack tip shielding mechanisms in quasi-brittle materials (1997)
    Springer
    Journal of materials science 32 (1997), S. 4011-4017 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract To gain insight into the shielding processes in quasi-brittle materials, in situ crack propagation and crack profile measurements were performed inside the scanning electron microscope (SEM). Crack tip shielding phenomena were studied in monolithic alumina and in SiC fibre-reinforced alumina matrix composites as a function of fibre coatings. The crack in the fibre-reinforced composite samples is bridged by a row of fibres which contains a fibre area fraction of 10%. The applied stress intensity factor necessary to extend the crack in the composite materials increased 25% for the gold coated fibre-reinforced alumina matrix composites and 13% for the polymer-coated fibre-reinforced composites, compared to the monolithic samples. Crack extension in the monolithic samples and in the fibre-reinforced composites occurred after the crack opening displacements close to the crack tip approached the critical crack tip profile corresponding to the intrinsic toughness of alumina. A hypothesis on the effect of closure stresses on crack profile shape and net toughness has been developed. Furthermore, crack profiles revealed that grain bridging in the vicinity of the fibres was operative in the fibre-reinforced composites at stress intensity factors far exceeding the critical stress intensity factor of the monolithic matrix material. The additional grain bridging in the vicinity of the fibres has never been reported and can only be revealed through crack profile measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018685303978
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    Paper (German National Licenses)
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