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  • 1
    Digitale Medien
    Digitale Medien
    A stereotactic device for experimental Gamma Knife radiosurgery in rats (1993)
    Springer
    Acta neurochirurgica 125 (1993), S. 156-160 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Gamma Knife ; radiosurgery ; rat ; stereotaxis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A rat stereotactic device was designed for use in Gamma Knife radiosurgery. Experimental radiosurgical lesions were made in superficial and deep cerebral structures to verify the accuracy of the coordinate system, which is based on a standard rat stereotactic atlas. Calculated dosages were shown to be accurate utilizing thermoluminescence dosimetry. Two additional features of the device permit the surgical positioning and placement of electrodes, and postmortem slicing of the brain according to the same coordinate system. This new apparatus allows precise and repeatable gamma irradiation of the rat brain without the need for expensive and time-consuming imaging techniques. Studies of this type will provide a rapid means for examining the effects of radiosurgery on the central nervous system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01401844
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  • 2
    Digitale Medien
    Digitale Medien
    Accuracy of an experimental stereotactic system for MRI-based Gamma Knife irradiation in the rat (1996)
    Springer
    Acta neurochirurgica 138 (1996), S. 1103-1108 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Gamma Knife ; MRI ; Stereotactic atlas ; rat ; stereotactic device
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Stereotactic devices for experimental Gamma Knife irradiation and magnetic resonance imaging (MRI) have recently been developed for experimental studies using rats [6, 7]. The present study examined the accuracy of these devices using the following two approaches. In the first approach, Gamma Knife irradiation was performed using the stereotactic device with targets based on a standard stereotactic atlas. Gadolinium-enhanced T1-weighted magnetic resonance imaging was performed using the MRI stereotactic device. Animals were then sacrificed after Evans blue injection, and the rat brain was sliced using an attachment to the stereotactic device. The center coordinates of the gadolinium-enhanced area from the MRI and Evans blue-stained area from the tissue sections were obtained using a computer-assisted image analysis system. These coordinates were compared with the target coordinates planned from the stereotactic atlas. In the second approach, a thermoluminescence dosimeter was implanted in the rat brain. Stereotactic MRI was performed using the stereotactic MRI device, and the coordinates of the implant were obtained. Gamma Knife irradiation was then performed at this target using the stereotactic device. The absorbed dose was measured and compared with the planning dose. These experiments demonstrated a spatial error of 0.6 mm (standard error ± 0.07) between Gamma Knife irradiation based on a comparison of the atlas coordinates and the lesion, and a spatial error of 1.0 mm (standard error ± 0.13) based on a comparison of the stereotactic MR images and the lesion. Gamma Knife irradiation based on MR images using the stereotactic device demonstrated a maximum error of 10% in absorbed dose at the target center. Together, the stereotactic devices for Gamma Knife irradiation and magnetic resonance imaging provide useful tools for Gamma Knife research in an animal model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01412315
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  • 3
    Digitale Medien
    Digitale Medien
    The role of the coagulation cascade in brain edema formation after intracerebral hemorrhage (1996)
    Springer
    Acta neurochirurgica 138 (1996), S. 396-401 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Brain edema ; brain water ; coagulation cascade ; fibrinogen ; Nα-(2-Naphthalenesulfonylglycyl)-4-amidino-DL-phenylalaninepiperidide ; α-NAPAP ; rat ; thrombin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The coagulation cascade has a potential role in brain edema formation due to intracerebral hemorrhage. In this study blood and other solutions were injected stereotactically into the right basal ganglia in rats. Twenty-four hours following injection, brain water and ion contents were measured to determine the amount of brain edema. Intracerebral blood resulted in an increase in brain water content. The amount of brain edema surrounding the intracerebral hematoma was reduced by a thrombin inhibitor Na-(2-Naphthalenesulfonylglycyl)-4-amidino-DL-phenylalaninepiperidide, (α-NAPAP) infused into the hematoma after the clot had been allowed to solidify. The inhibitor did not alter the actual size of the clot mass. An artificial clot composed of fibrinogen, thrombin, and styrene microspheres also produced brain edema. A fibrin clot led to edema formation even in the absence of mass effect provided by the microspheres. The single component responsible for production of brain edema in all these models was thrombin. The edema was formed in response to a fibrinogen-independent pathway. These results indicate that the coagulation cascade is involved in brain edema that develops adjacent to an intracerebral hematoma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01420301
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Histological changes in the normal rat brain after gamma irradiation (1996)
    Springer
    Acta neurochirurgica 138 (1996), S. 451-459 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Radiosurgery ; Gamma Knife ; radiation necrosis ; rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Radiation-induced changes in the parietal cortex of Wistar rats were observed at various time points after gamma surgery. Maximum dosages of 50, 75, and 120 Gy were given at the iso-center of the radiation using a 4-mm collimator. Conventional histochemical and immunocytochemical analyses, and computer-assisted videomicroscopy were utilized to examine perfusion-fixed brain tissue. Irradiation at a dosage of 50 Gy elicited morphological changes of astrocytes in the parietal cortex at 3 months. Vasodilatation became obvious at 12 months; fibrin deposition was observed in the dilated capillary wall. Neither leakage of Evans Blue from the vasculature into the tissue nor necrosis was observed across the 12 month observation period. Irradiation at a dosage of 75 Gy resulted in morphological changes of astrocytes within 1 month. Dilatation of vessels and capillary thickening were observed at 3 months. Evans Blue leakage and necrosis were observed at 4 months after 75 Gy irradiation. At this time, the walls of arterioles became thickened by subintimal accumulation of fibrin and hyaline substance; this sometimes resulted in occlusion of the lumen. Significant hemispheric swelling was observed at 4 months. Irradiation at a dosage of 120 Gy elicited changes in astrocytic morphology within 3 days. Evans Blue leakage into the tissue was observed by 3 weeks. Vasodilatation became marked at this time point and rarefaction was observed in the irradiated cortex. Necrosis was observed at 4 weeks, however, no significant swelling was observed. Taken together, these findings demonstrate time-dependent and dosage-dependent changes in normal cerebral tissue after Gamma Knife irradiation. These results provide a basis for gauging the impact of gamma surgery in regions of eloquent tissue. An enhanced understanding of the cellular responses to radiosurgery will contribute to developing and evaluating future applications for gamma surgery.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01420308
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  • 5
    Digitale Medien
    Digitale Medien
    An evasion game with a destination (1985)
    Springer
    Journal of optimization theory and applications 46 (1985), S. 359-372 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Game theory ; time lag systems ; value of the game ; optimal strategies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper solves an aiming and evasion game in which a gunner with a number of shots attempts to hit an evader moving along the positivex-axis. The gunner's aiming of the evader is complicated by the fact that there is a delay due to the time taken for the shot to reach the evader from the gunner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00939289
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  • 6
    Digitale Medien
    Digitale Medien
    Equilibrium points of a class of many-person games (1977)
    Springer
    Journal of optimization theory and applications 23 (1977), S. 285-303 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Game theory ; optimal strategies ; equilibrium points ; economics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper deals with the competitive equilibrium points of a class of (n+1)-person games, the players beingn sellers and a single buyer. Each seller offers a price for his product; depending upon the prices offered, the buyer then determines the amount he wishes to buy from each seller. Two types of equilibrium points in this class of games are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00933053
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  • 7
    Digitale Medien
    Digitale Medien
    A firing game with time lag (1983)
    Springer
    Journal of optimization theory and applications 41 (1983), S. 547-558 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Game theory ; time lags ; value of the game ; difference equations ; optimal strategies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A gunnerG, withj units of ammunition, can fire at an evaderE which attempts to avoid from being hit by moving about integral points along the nonnegativex-axis. When at pointi, the evaderE can move to pointi − 1, remain at pointi, or move to pointi + 1 after one unit of time, which is the amount of time required by the ammunition to reachE fromG.E's destination is a bunker at the origin where he is safe from being hit. This game is solved recursively for all possible values ofi andj.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00934642
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