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  • 1
    Electronic Resource
    Electronic Resource
    MR guidance of laser disc decompression: preliminary in vivo experience (1998)
    Springer
    European radiology 8 (1998), S. 592-597 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Spine ; Intervertebral disks ; Lasers ; MR imaging guidance ; MR imaging temperature monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this study was to perform percutaneous laser disc decompression (PLDD) under MR guidance in an open configuration 0.5-T MR system. Following failed conservative treatment for 6 months, eight patients with contained disc herniations were enrolled in the study. Following MR guided introduction of the laser fiber into the targeted disc space, the laser-induced temperature distribution was visualized using a color-coded subtraction technique based on a T1-weighted GRE sequence. In seven patients PLDD could be performed. In all cases laser effects were depicted by MR. In this regard the color-coded technique was found to be superior to conventional magnitude images. Whereas no apparent decrease in the extent of herniation was discovered immediately following PLDD, T2-weighted FSE images showed signal intensity alterations in two of the seven patients. Clinical evaluation, obtained 3–4 months after PLDD, revealed a fair (n = 2) or good (n = 4) response to the treatment. One patient showed no change in symptoms. MR guidance and monitoring of PLDD is feasible within an open 0.5-T system and seems to render PLDD more safe and controllable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050441
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  • 2
    Electronic Resource
    Electronic Resource
    Interactive MR-guided biopsies of the thyroid gland: validation of a new method (1998)
    Springer
    European radiology 8 (1998), S. 1173-1178 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Thyroid ; Biopsy ; Interventional MR ; MR guidance ; Stereotaxis ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of this study was to demonstrate the clinical feasibility and utility of an interactive MR-guidance system to target and biopsy thyroid lesions, and to compare resolution between ultrasound and interventional MR imaging in the evaluation of thyroid lesions. Twenty thyroid lesions of 18 patients were interactively biopsied using a 0.5-T superconducting open magnet system. Stereotactic localization of the needle and imaging was accomplished using T1-weighted gradient-recalled-echo (GRE) images. Representative cytological material was retrieved in 16 of 20 lesions (benign cystic or colloid goiter: n = 14; one de Quervain's thyroiditis and one follicular neoplasia). Lesions smaller than 1.5 cm detected by ultrasound could not be visualized adequately on GRE images. Lesions smaller than 1.5 cm were successfully biopsied by ultrasound (three colloid and haemorrhagic goiters and one adenoma). Magnetic-resonance-guided interactive biopsies and positioning of non-ferromagnetic needles in the thyroid gland are technically feasible and safe. Compared with high-resolution ultrasound, lesions larger than 1.5 cm can be adequately visualized and biopsied. Magnetic-resonance-guided placement of non-ferromagnetic needles is no substitute for high-resolution ultrasound in clinical work-up of thyroid lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050529
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  • 3
    Electronic Resource
    Electronic Resource
    Low energy electron-enhanced etching of Si(100) in hydrogen/helium direct-current plasma (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2475-2477 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low energy electron-enhanced etching of Si(100) has been achieved by placing the sample on the anode of a dc discharge in hydrogen/helium mixtures. Over a broad range of gas composition, gas pressure, and discharge current, nonpatterned samples gave etch yields of 0.01–0.02 atoms/electron, and average etch rates of 2000–3000 A(ring)/min. Postetch examination by atomic force microscopy revealed surface roughness of 2–3 nm. These results are related to incident flux of H atoms and electrons through a simple model of the anode sheath layer above the sample. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114000
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrafast absorption in free-standing porous silicon films (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1966-1968 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrafast absorption studies on free-standing porous silicon films have been carried out at room temperature to investigate the carrier dynamics and the luminescence mechanism. Ultraviolet and visible excitations were used on an as-prepared sample and two annealed samples. Transient absorption curves of UV pumped, as-prepared samples contain a fast decay (τf) of 0.8±0.2 ps and a slower decay of (approximately-greater-than)30 ps. τf is found to be shorter for both the 500 °C annealed sample with UV excitation and for the as-prepared sample with visible excitation. The faster decay rates suggest that the subpicosecond component of the transient absorption may be due to carrier thermalization rather than core-to-surface state excitation transfer. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114755
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  • 5
    Electronic Resource
    Electronic Resource
    Punktionen an einem offenen, interventionellen MR-Gerät Veranschaulichung anhand eines Fallbeispiels (1996)
    Springer
    Der Radiologe 36 (1996), S. 705-708 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Endometriose ; Biopsie ; Nadel ; Magnetresonanztomographie ; Interventionelle Radiologie ; Key words Endometriosis ; Biopsy ; needle ; Magnetic resonance imaging ; Interventional radiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Introduction and Methods: A 0.5 T open-configuration MR system allows free access to the patient via a 58-cm-wide opening on both sides of the machine. A newly developed system for needle guidance enables the examiner to perform biopsies in combination with real-time imaging and to position laser fibers in the human body. For imaging, a 2D gradient echo sequence is used (TR 19 ms, TE 9 ms, flip angle 30 °, FOV 24 × 24 cm, slice thickness 10 mm matrix 256 × 128). The acquired images are displayed on two LCD screens localized within the MR system, thus allowing an interactive needle guidance. This procedure is illustrated by a case report. Discussion: The handling of the system for needle guidance was simple, mainly due to a real-time adaption of the scan plane to the needle direction. The possibility of multi-angulated approaches makes biopsies of hardly accessible anatomic regions feasible. Conclusion: We think that MR-guided needle positioning will play an important role in combination with thermosensitive therapies. Thermosensitivity of MR imaging allows extensive monitoring of such interventions.
    Notes: Zusammenfassung Ein offenes, interventionelles MR-Gerät (0,5 Tesla) erlaubt durch eine 58 cm breite Öffnung den Zugang zum im Gerät liegenden Patienten. Ein spezielles Punktionssystem ermöglicht es, unter Echtzeitbildgebung Punktionen vorzunehmen sowie auch Laserfasern im menschlichen Körper zu plazieren. Zur Bildgebung wird eine 2d-Gradientenechosequenz verwendet (TR 19 ms, TE 9 ms, Flipwinkel 30 °, FOV 24 × 24 cm, Schichtdicke 10 mm, Matrix 256 × 128). Die akquirierten Bilder werden dem punktierenden Radiologen auf 2 im Gerät angebrachten LCD-Monitoren angezeigt, wodurch eine interaktive Nadelführung ermöglicht wird. Es wurden bereits zahlreiche Punktionen an Patienten durchgeführt. Wichtig wird die MR-gesteuerte Punktion von Läsionen in Kombination mit der Durchführung thermosensitiver Therapien. Die der MR-Bildgebung inhärente Temperatursensitivität ermöglicht ein umfassendes Monitoring solcher Eingriffe in Echtzeit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050131
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  • 6
    Electronic Resource
    Electronic Resource
    Photoemission of LaI2 and CeI2 (1995)
    Springer
    The European physical journal 97 (1995), S. 25-34 
    Details
    ISSN: 1434-6036
    Keywords: 79.60 ; 71.28
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of the layered compounds LaI2 and CeI2 was investigated by photoemission and electron energy loss spectroscopy. From the experimental results we are able to confirm the metallic nature of these compounds, and by using photon energy dependent measurements of the valence band we can identify the orbital character of the conduction band as essentially 5d1-like. A detailed analysis of the Ce 3d and 4f spectra yields a remarkably small 4f-5d hybridization strength, almost completely decoupling the f-electron from the conduction band, which makes CeI2 a somewhat unusual system compared to other metallic Ce compounds. Band structure calculations by Jepsen and Andersen [1] confirm these experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317584
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  • 7
    Electronic Resource
    Electronic Resource
    Electron and hole doping in NiO (1995)
    Springer
    The European physical journal 97 (1995), S. 83-93 
    Details
    ISSN: 1434-6036
    Keywords: 79.60 ; 71.20 ; 71.28
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated hole doped (by lithium) and electron-doped (by nickel metal) NiO with photoemission (PES), inverse photoemission (IPES) and low and high energy electron energy loss spectroscopy (EELS). Both types of doping create empty states approximately in the middle of the charge transfer gap of undoped NiO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317591
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  • 8
    Electronic Resource
    Electronic Resource
    Hole doping in correlated CT — insulators: LixNi1−xO (1995)
    Springer
    Journal of low temperature physics 99 (1995), S. 421-423 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Experimental results on the optical absorption in Li doped NiO are presented. Upon Li doping, considerable oscillator strength is found to appear throughout the fundamental absorption gap until at 2% doping the d-d excitations usually observed within the gap are completely overwhelmed by these new excitations. Low energy REELS measurements on the same set of samples do not show the same behaviour. We briefly discuss the compatibility of our findings with results of previous electron spectroscopic results and with theoretical scenarios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00752319
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