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  • 1
    Electronic Resource
    Electronic Resource
    Carbon isotope thermometry in marbles of the Adirondack Mountains, New York (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 13 (1995), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Carbon isotope thermometry has been applied to coexisting calcite and graphite in marbles from throughout the Adirondack Mountains, New York. Eighty-nine calcite-graphite pairs from the amphibolite grade NW Adirondacks change systematically in temperature north-westwards from 680 to 640 to 670° C over a 30-km distance, reflecting transitions from amphibolite facies towards granulite facies to the north-west and to the south-east. Temperature contours based on calcite-graphite thermometry in the NW Adirondacks parallel mineral isograds, with the orthopyroxene isograd falling above 675° C, and indicate that regional metamorphic temperatures were up to 75° C higher than temperatures inferred from isotherms based on cation and solvus thermometry (Bohlen et al. 1985). Fifty-five calcite-graphite pairs from granulite grade marbles of the Central Adirondacks give regional metamorphic temperatures of 670–780° C, in general agreement with cation and solvus thermometry.Data for amphibolite and granulite grade marbles show a 12%oo range in δ13Ccal and δ13Cgr. A strong correlation between carbon isotopic composition and the abundance of graphite (Cgr/Crock) indicates that the large spread in isotopic compositions results largely from exchange between calcite and graphite during closed system metamorphism. The trends seen in δ13C vs. Cgr/Crock and δ13Ccal vs. δ13Cgr could not have been preserved if significant amounts of CO2-rich fluid had pervasively infiltrated the Adirondacks at any time. The close fit between natural data and calculated trends of δ13C vs. Cgr/Crock indicates a biogenic origin for Adirondack graphites, even though low δ13C values are not preserved in marble.Delamination of 17 graphite flakes perpendicular to the c-axis reveals isotopic zonation, with higher δ13C cores. These isotopic gradients are consistent with new graphite growth or recrystallization during a period of decreasing temperature, and could not have been produced by exchange with calcite on cooling due to the sluggish rate of diffusion in graphite. Samples located 〉2km from anorthosite show a decrease of 0.5-0.8%oo in the outer 100 μ of the grains, while samples at distances over 8 km show smaller core-to-rim decreases of c.0.2%oo. Correlation between the degree of zonation and distance to anorthosite suggests that the isotopic profiles reflect partial overprinting of higher temperature contact metamorphism by later granulite facies metamorphism. Core graphite compositions indicate contact metamorphic temperatures were 860–890° C within 1 km of the Marcy anorthosite massif. If samples with a significant contact metamorphic effect (Δ(cal-gr) 〈3.2%oo) are not included, then the remaining 38 granulite facies samples define the relation Δ13C(cal-gr) = 3.56 ± 106T-2 (K).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1995.tb00244.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Wrapping of Solitary Ruptured Intracranial Aneurysms, Outcome at Five Years (1998)
    Springer
    Acta neurochirurgica 140 (1998), S. 1167-1171 
    Details
    ISSN: 0942-0940
    Keywords: Keywords: Aneurysm; wrapping; microsurgical; outcome.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  Previous follow up studies of patients who have had ruptured intracranial aneurysms treated by a wrapping technique have largely been in the pre-microsurgical era. Our objective was to ascertain whether wrapping aneurysms with the aid of the operating microscope provides protection against rebleeding in the short and long term. The study involved retrospective analysis of patients with ruptured aneurysms treated by wrapping over a six-year period. Twenty-nine patients were identified with wrapped aneurysms, of these 15 had wrapping of a solitary ruptured aneurysm, the remainder were excluded because of clip/wrap combination, multiple aneurysms, and unruptured aneurysms. Of the 15 patients who had a solitary ruptured aneurysm wrapped, none had rebled at one year follow up. One patient died of a myocardial infarction at 4 years, the remaining 14 patients had no episodes of rebleeding with all patients achieving Glasgow outcome scores of four or five at 5 years follow-up. Although surgical clipping of intracranial aneurysms is the definitive method of treatment, our findings suggest that wrapping of ruptured intracranial aneurysms with the aid of the operating microscope confers good protection against both early and late rebleeding in those cases considered `unclippable'.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007010050232
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  • 3
    Electronic Resource
    Electronic Resource
    The value of per-operative smear examination during stereotactic biopsy (1993)
    Springer
    Acta neurochirurgica 121 (1993), S. 196-198 
    Details
    ISSN: 0942-0940
    Keywords: Stereotactic biopsy ; smear
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sixty-two consecutive CT-directed stereotactic biopsies were studied retrospectively to determine the value of the per-operative smear examination. Overall, in 69% of cases the immediate smear result agreed with the definitive histology. However, a smear diagnosis of malignant glioma was more reliable than that of metastasis (with 100% and 55% aggreement with the final result respectively). In those cases where the final histological diagnosis was that of malignant glioma, immediate smear preparations taken from the hypodense centre were found to be more reliable than those taken from the enhancing edge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01809275
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Open stereotactic amygdalohippocampectomy — Clinical, psychometric, and MRI follow-up (1993)
    Springer
    Acta neurochirurgica 123 (1993), S. 33-38 
    Details
    ISSN: 0942-0940
    Keywords: Epilepsy ; surgical technique ; stereotactic resection ; magnetic resonance imaging ; psychometry ; follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The clinical results of six cases of open stereotactic amygdalohippocampectomy for medically intractable epilepsy are presented. Outcome in terms of seizure control (highly satisfactory in five patients) and neuropsychological sequelae (all cases had poor functioning of the contralateral temporal lobe pre-operatively) are detailed. In addition the use of post-operative Magnetic Resonance Imaging (MRI) is demonstrated and shown to be a valuable tool in providing the crucially accurate baseline that is required for more meaningful follow-up outcome studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01476282
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Contrast-enhanced MR angiography in patients with carotid artery stenosis: comparison of two different techniques with an unenhanced 2D time-of-flight sequence (2000)
    Springer
    Neuroradiology 42 (2000), S. 240-248 
    Details
    ISSN: 1432-1920
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Conventional time-of-flight (TOF) MR angiography (MRA) in carotid artery stenosis relies on flow-related enhancement to produce signal from vascular structures. Intravoxel phase dispersion, due to vortices, causes loss of signal and is the reason for the tendency to overestimate the degree of stenosis. In contrast-enhanced MRA, intravascular signal is mainly dependent on T1 shortening of the blood. We compared first-pass contrast-enhanced MRA (contrast-enhanced 3D gradient echo, ce3D GRE) and contrast-enhanced 2D TOF (ce2D TOF) sequences with an unenhanced 2D TOF in 13 patients with carotid artery stenosis, assessing delineation of the carotid bifurcation, enhancement of veins and grade of stenosis. The contrast-enhanced techniques produced more morphological detail, the ce3D GRE being superior to the ce2D TOF. Four carotid arteries were reclassified into lesser stenosis categories using the ce3D GRE technique. However, seven carotid arteries (27 %) were rated as nondiagnostic on the ce3D GRE, mainly due to masking of the carotid bifurcation by veins. The latter can be avoided by decreasing the acquisition time; on our 1.5-T system we could achieve a minimum time of 23 s per 3D GRE. Further reduction of acquisition time would be necessary to incorporate this method into clinical routine, requiring higher-performance gradients, which are not available in many UK hospitals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050879
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Artefact on MRA following aneurysm clipping: an in vitro study and prospective comparison with conventional angiography (1999)
    Springer
    Neuroradiology 41 (1999), S. 680-686 
    Details
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance angiography ; Digital subtraction angiography ; Aneurysm clips ; Magnetic resonance artefact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using both an experimental model and clinical cases, we looked at the artefact produced by Aesculap titanium-alloy aneurysm clips on MRA. Experimentally, the volume affected by artefact was 50 % less when the clip was imaged lying parallel to the main ferromagnetic field than when lying perpendicular to it. Clinically, MRA was prospectively compared with digital subtraction angiography (DSA) in nine patients who had undergone aneurysm clipping. One patient with a non-diagnostic MRA due to movement artefact was excluded. In all other cases there was an area of signal loss surrounding the clips, obscuring the immediately adjacent vessel segments. There was good demonstration of the adjacent bifurcations in five cases and the contralateral circulation was seen well in all patients. In three cases in which the adjacent bifurcations were not seen, considerable vasospasm was suggested by MRA and confirmed with DSA. In one patient an unclipped contralateral ophthalmic artery aneurysm was identified using both modalities. In this series there were no adverse events relating to clips in either static or time-varying magnetic fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050824
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