Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-1920
    Keywords: Key words MRI ; Cerebral ischaemia ; Carotid artery obstruction ; Perfusion studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our purpose was to investigate the potential of dynamic susceptibility contrast-enhanced MRI in assessing regional haemodynamics in patients with cerebrovascular disease. T2*-weighted FLASH sequences were performed on a control group of 10 healthy subjects, 13 patients with unilateral stenosis or occlusion of the internal carotid artery and 6 patients with acute onset of neurological symptoms, the observed signal intensities being converted into concentration-time curves. A gamma-variate function was fitted to the measured concentration-time curves to eliminate effects of tracer recirculation. In each patient the two cerebral hemispheres were compared and the difference between the mean transit times and the percental change of the regional cerebral blood volume, calculated for each side. Patients with haemodynamically significant unilateral carotid obstruction can be divided into two subgroups: those with good and those with poor collateral supply. Patients with good collateral supply had a slight but not statistically significant increase in mean transit time and cerebral blood volume on the diseased side, whereas those with poor collaterals had a significant increase compared with the control group. In patients with acute onset of neurological symptoms perfusion maps clearly demonstrated the disturbed perfusion at a time when T2-weighted images were still normal. Perfusion imaging is a reliable and noninvasive method of assessing changes in cerebral perfusion in patients with unilateral carotid stenosis. This MR technique permits monitoring of haemodynamic changes during therapy and thus may become an alternative to SPECT and PET scanning. In patients with acute occlusion of a cerebral artery, perfusion imaging reveals the entire perfusion deficit before conventional MRI and thus allows early intervention.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1920
    Keywords: Key words Perfusion-weighted magnetic resonance imaging ; Echo planar imaging ; Cerebral ischaemia ; Animal studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared gradient-echo (GRE), spin-echo (SE) and stimulated-echo (STE) echo-planar imaging sequences for perfusion-weighted imaging at different field strengths. Focal cerebral ischaemia was induced by endovascular occlusion of the middle cerebral artery in eight rats. MR was performed at 4.7 T or 2.35 T. With each sequence, we acquired data sets before, during and after bolus injection of Gd-DTPA with a time resolution of 1.2 s per image. The perfusion-weighted images were assessed with regard to image quality, artefacts, signal-to-noise ratio (SNR), and signal-attenuation-to-noise ratio (ΔSNR) of the non-ischaemic tissue. Visual assessment showed GRE-EPI images acquired at 4.7 T to suffer from distortion due to susceptibility artefacts. Artefacts were less marked with the SE and STE series. The GRE-EPI sequence gave the highest SNR and ΔSNR. At 2.35 T, the SNR of the STE sequences was less than 3 and therefore did not allow construction of reliable signal-time curves. SE-EPI was best suited for perfusion-weighted imaging at high field strength thanks to its minimal distortion artefacts and high SNR. Using lower field strengths (2.35 T and less), susceptibility artefacts are reduced; GRE-EPI sequences are then best suited, because they have the highest SNR and T2* sensitivity.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European radiology 7 (1997), S. S203 
    ISSN: 1432-1084
    Keywords: Key words: Neuroimaging ; Diffusion-weighted MR ; Perfusion-weighted MR ; Infarction ; Ischaemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Cerebral infarct causes over 170, 000 deaths per year in the United States. Recent developments in neuroimaging are providing an insight into focal cerebral ischaemia, including its pathophysiology and the area of brain at risk. Perfusion-weighted magnetic resonance (MR) allows evaluation of the blood supply to the ischaemic area, and diffusion-weighted MR permits assessment of tissue damage. Although both functional imaging techniques require some refinement, it is likely that they will soon become part of the normal clinical routine and allow accurate characterisation of pathology. It is expected that this may eventually lead to the development of new treatments.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Magnetresonanztomographie ; Kontrastmittel ; Eisenoxid ; MION ; Glioblastom ; Key words Magnetic resonance imaging ; Contrast medium ; Iron oxide ; MION ; Glioblastoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Purpose: To investigate whether the margins of microscopic tumors can be delineated better with monocrystalline iron oxide nanoparticles (MION), a superparamagnetic contrast medium, than with Gd-DTPA by magnetic resonance imaging (MRI). Methods: MRI and histological examinations were conducted in 28 Wistar rats with sterotactically implanted gliomas (C6 gliomas). Of the 28 animals, 14 were examined after intravenous administration of MION [nine animals received 179 mmol Fe/kg body weight (dose 1), and five, 893 mmol Fe/kg (dose 2)]. The other 14 animals were examined first after i.v. administration of Gd-DTPA (0.2 mmol/ kg) and then after i.v. administration of MION. The extent of the tumors as seen on MRI and at histological study were compared. Results: Iron particles were identified microscopically in tumor cells and in the tumoral interstitium. After administration of MION at dose 1, the contrast-enhanced area of tumor was 1.55-fold greater than the extent of tumor identified by histological study, at dose 2, 2.15-fold. Compared with Gd-DTPA the area of contrast enhancement was greater by a factor of 1.38 with MION administration at dose 1 and by a factor of 1.91 at dose 2. Conclusion: MION provides intra- and extracellular contrast enhancement. The area of the contrast-enhanced tumor is dose-dependently greater with MION than with Gd-DTPA and also greater than the extent of tumor seen at histological study.
    Notes: Zusammenfassung Fragestellung: Verbessert ein superparamagnetisches Kontrastmittel (monocrystalline iron oxide nanoparticle, MION) die MR-tomographische Abgrenzbarkeit mikroskopischer Tumorgrenzen im Vergleich zu Gd-DTPA? Methodik: 28 Wistar-Ratten mit stereotaktisch implantiertem Gliom (C6-Gliom) wurden MR-tomographisch und mikroskopisch untersucht. 14 Tiere hiervon wurden nach intravenöser (i.v.) Gabe der MION untersucht [9 Tiere erhielten 179 μmol Fe/kg Körpergewicht (=Dosierung 1), 5 Tiere 893 μmol Fe/kg (=Dosierung 2)]. 14 Tiere wurden zuerst nach i.v. Gabe von Gd-DTPA (0,2 mmol/kg) und anschließend nach i.v. Gabe der MION untersucht. MR-tomographische und mikroskopische Tumorausdehnungen wurden verglichen. Ergebnisse: Eisenpartikel konnten mikroskopisch in Tumorzellen und im Tumorinterstitium nachgewiesen werden. Nach Gabe der MION in Dosierung 1 war die Ausdehnung des KM-anreichernden Areals in der MRT im Durchschnitt 1,55fach größer als der in der Histologie erkennbare Tumor, bei Dosierung 2 sogar 2,15fach. Im Vergleich mit Gd-DTPA war die KM-anreichernde Fläche nach Gabe der MION in Dosierung 1 um den Faktor 1,38 größer, in Dosierung 2 um den Faktor 1,91. Schlußfolgerungen: MION führen zu einer intra- und extrazellulären KM-Anreicherung. Die Ausdehnung des KM-anreichernden Areals ist dosisabhängig ausgedehnter als die KM-Anreicherung nach Gd-DTPA Gabe und auch ausgedehnter als die morphologisch nachweisbaren Tumorgrenzen.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Hirninfarkt ; Neuroradiologie ; Computertomographie ; MRT ; Key words Brain infarct ; Neuroradiology ; Computertomography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary At least three questions has to be answered by imaging methods, when new therapies in acute ischemic stroke should be used: 1. Is there a cerebral ischemia? 2. What is the size of the irreversibel damaged tissue and what is the size of the safeable tissue? Is there still a vessel occlusion? New MRI-techniques including MR-angiography, diffusion-weighted imaging and perfusion-MRI, have the potential to de-scribe the status of the brain in detail and to answer these questions. However, the value of these techniques for therapeutical deci-sions (thrombolysis) is unclear and has to be evaluated in clinical studies. Therefore in clinical routine these decisions should still be based on informations from CT and perhaps CT-angiography.
    Notes: Zusammenfassung Um neue Therapien beim arteriellen Schlaganfall optimal einsetzen zu können, müssen in der Akutphase mit den bildgebenden Verfahren drei Fragen beantwortet werden: 1. Liegt eine zerebrale Ischämie vor? 2. Wie groß ist das irreversibel geschädigte und das noch rettbaren Hirngewebe? 3. Liegt noch eine Gefäßokklusion vor? Die neuen magnetresonanztomographischen Techniken (MR-Angiographie, diffusionsgewichtete Bildgebung und Perfusions-MRT) liefern in relativ kurzer Untersuchungszeit eine umfassende Beschreibung des aktuellen Infarktstatus und können prinzipiell diese Fragen beantworten. Die therapeutische Wertigkeit dieser Techniken insbesondere als Entscheidungsgrundlage für eine Thrombolysetherapie muß jedoch noch in klinischen Studien untersucht werden. Bis dahin kann für den klinischen Alltag die Computertomographie evtl. mit der ergänzenden CT-Angiographie als die Methode der Wahl angesehen werden, mit der die therapieentscheidende Infarktdiagnostik durchgeführt werden sollte.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 13 (1997), S. 215-224 
    ISSN: 0749-503X
    Keywords: glucose transporter gene ; heterologous expression ; substrate accumulation ; transport energization ; Schizosaccharomyces pombe ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Genomic DNA of the Schizosaccharomyces pombe glucose transporter, GHT1, was obtained by complementation of the glucose transport deficient Sz. pombe strain YGS-5. Here we describe the GHT1 gene that encodes a protein of 565 amino acids with a corresponding molecular mass of 62·5 kDa. This eukaryotic glucose transporter contains 12 putative transmembrane segments and is homologous to the HXT multigene family of S. cerevisiae with several amino acid motifs of this sugar transporter family. It is also homologous to other sugar carriers from human, mouse and Escherichia coli. The function of the Ght1 protein as a glucose transporter was proved both by homologous and heterologous expression in the Sz. pombe mutant YGS-5 and in the S. cerevisiae hxt mutant RE700A, respectively. Both transformed yeast strains transported d-glucose with substrate specificity similar to that in Sz. pombe wild-type cells. Moreover, the cells of the two transformed yeast strains accumulated 2-deoxy-d-glucose, a non-metabolizable d-glucose analogue, with an efficiency similar to Sz. pombe wild-type cells. The ability of the S. cerevisiae mutant RE700A to accumulate 2DG in an ΔμH+dependent manner after transformation with GHT1 provides evidence that the Sz. pombe transporter catalyses an energy-dependent uptake of glucose. The sequence of GHT1 was deposited at EMBL, Outstation EBI, Accession Number X91218. ©1997 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...