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1.

001-es BibID:BIBFORM033464
Első szerző:Franke, Claudia
Cím:Arterial spin tagging perfusion imaging of rat brain : dependency on magnetic field strength / C. Franke, F. A. van Dorsten, L. Olah, W. Schwindt, M. Hoehn
Dátum:2000
ISSN:0730-725X
Megjegyzések:Perfusion-weighted imaging (PWI), using the method of arterial spin tagging, is strongly T(1)-dependent. This translates into a high field dependency of the perfusion signal intensity. In order to determine the expected signal improvement at higher magnetic fields we compared perfusion-weighted images in rat brain at 4.7 T and 7 T. Application of PWI to focal ischemia and functional activation of the brain and the use of two different anesthetics allowed the observation of a wide range of flow values. For all these (patho-)physiological conditions switching from 4.7 T to 7 T resulted in a significant increase of mean perfusion signal intensity by a factor of 2.96. The ratio of signal intensities of homotopic regions in the ipsi- and contralateral hemisphere was field-independent. The relative contribution of a) T(1) relaxation time, b) net magnetization, c) the Q-value of the receiver coils and d) the degree of adiabatic inversion to the signal improvement at higher field strength were discussed. It was shown that the main parameters contributing to the higher signal intensity are the lengthening of T(1) and the higher magnetization at the higher magnetic field.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Magnetic Resonance Imaging. - 18 : 9 (2000), p. 1109-1113. -
További szerzők:van Dorsten, Ferdi A. Oláh László (1967-) (neurológus) Schwindt, Wolfram Hoehn, Mathias
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2.

001-es BibID:BIBFORM033467
Első szerző:Grüne, Matthias
Cím:Quantitative T*(2) and T'(2) maps during reversible focal cerebral ischemia in rats : separation of blood oxygenation from nonsusceptibility-based contributions / Grüne M., van Dorsten F. A., Schwindt W., Oláh L., Hoehn M.
Dátum:2000
Megjegyzések:Quantitative imaging contrast is evaluated which allows the selective measurement of the blood oxygenation state during cerebral ischemia within a multiparametric imaging study on rats. In a first step, the ambiguities arising in T*(2)-weighted images due to T*(2) heterogeneity are eliminated by calculating T*(2) maps. Then, 1/T'(2) maps are calculated according to 1/T'(2) = 1/T*(2) - 1/T(2) to eliminate nonsusceptibility-induced changes of 1/T*(2) after the induction of stroke. This is of particular importance in the presence of vasogenic edema. The changes Delta(1/T'(2)) after the onset of ischemia selectively quantify the variations of the deoxyhemoglobin content during the development of the infarct. The presented results are not available from conventionally recorded parameters of a stroke study and, together with perfusion-weighted images, form a powerful combination to analyze the oxygen consumption and the metabolism of the tissue.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Magnetic Resonance in Medicine. - 42 : 6 (2000), p. 1027-1032. -
További szerzők:van Dorsten, Ferdi A. Schwindt, Wolfram Oláh László (1967-) (neurológus) Hoehn, Mathias
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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3.

001-es BibID:BIBFORM033461
Első szerző:Oláh László (neurológus)
Cím:Secondary deterioration of apparent diffusion coefficient after 1-hour transient focal cerebral ischemia in rats / Laszlo Olah, Stefan Wecker, Mathias Hoehn
Dátum:2000
Megjegyzések:Recent investigations on transient focal cerebral ischemia suggested recovery of energy metabolism during early reperfusion, but followed by secondary energy failure. As disturbances of energy metabolism are reflected by changes of the apparent diffusion coefficient (ADC) of water, the aim of the current study was to follow the dynamics of the ADC during 1 hour of middle cerebral artery occlusion (MCAO) and 10 hours of reperfusion. The right MCA was occluded in male Wistar rats inside the magnet using a remotely controlled thread occlusion model. Diffusion-, perfusion-, and T2-weighted images were performed repetitively, and ADC, perfusion, and T2 maps were calculated and normalized to the respective preischemic value. The lesion volume at each time point was defined by ADC < 80% of control. At the end of 1-hour MCAO the hemispheric lesion volume was 22.3 +/- 9.0%; it decreased to 6.4 +/- 5.7% in the first 2 hours of reperfusion (P < 0.01), but then increased again, and by the end of 10 hours of reperfusion reached 17.3 +/- 9.3%. The mean relative ADC in the end ischemic lesion volume significantly improved within 2 hours of reperfusion (from 65.7 +/- 1.2% to 90.1 +/- 6.7% of control), but later declined and decreased to 75.4 +/- 7.3% of control by the end of the experiment. Pixels with secondary deterioration of ADC showed a continuous increase of T2 value during the first 2 hours of reperfusion in spite of ADC improvement, indicating improving cytotoxic, but generation of vasogenic edema during early reperfusion. A significant decrease of the perfusion level was not observed during 10 hours of recirculation. The authors conclude that the improvement of ADC in the early phase of reperfusion may be followed by secondary deterioration that was not caused by delayed hypoperfusion.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Journal of Cerebral Blood Flow and Metabolism. - 20 : 10 (2000), p. 1474-1482. -
További szerzők:Wecker, Stefan Hoehn, Mathias
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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4.

001-es BibID:BIBFORM033460
Első szerző:Oláh László (neurológus)
Cím:Relation of apparent diffusion coefficient changes and metabolic disturbances after 1 hour of focal cerebral ischemia and at different reperfusion phases in rats / Laszlo Olah, Stefan Wecker, Mathias Hoehn
Dátum:2000
Megjegyzések:Changes in apparent diffusion coefficients (ADC) were compared with alterations of adenosine triphosphate (ATP) concentration and pH in different phases of transient focal cerebral ischemia to study the ADC threshold for breakdown of energy metabolism and tissue acidosis during ischemia and reperfusion. Male Wistar rats underwent 1 hour of middle cerebral artery occlusion without recirculation (n = 3) or with 1 hour (n = 4) or 10 hours of reperfusion (n=5) inside the magnet, using a remotely controlled thread occlusion model. ADC maps were calculated from diffusion-weighted images and normalized to the preischemic value to obtain relative ADC maps. Hemispheric lesion volume (HLV) was determined on the last relative ADC maps at different relative ADC thresholds and was compared to the HLV measured by ATP depletion and by tissue acidosis. The HLVs, defined by ATP depletion and tissue acidosis, were 26.0% +/- 10.6% and 38.1% +/- 6.5% at the end of ischemia, 3.3% +/- 2.4% and 4.8% +/- 3.5% after 1 hour of reperfusion, and 11.2% +/- 4.7% and 10.9% +/- 5.2% after 10 hours of recirculation, respectively. The relative ADC thresholds for energy failure were consistently approximately 77% of the control value in the three different groups. The threshold for tissue acidosis was higher at the end of ischemia (86% of control) but was similar to the results obtained for ATP depletion after 1 hour (78% of control) and 10 hours (76% of control) of recirculation. These results indicate that the described relative ADC threshold of approximately 77% of control provides a good estimate for the breakdown of energy metabolism not only during middle cerebral artery occlusion but also at the early phase of reperfusion, when recovery of energy metabolism is expected to occur, or some hours later, when development of secondary energy failure was described.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Journal of Cerebral Blood Flow and Metabolism. - 21 : 4 (2000), p. 430-439. -
További szerzők:Wecker, Stefan Hoehn, Mathias
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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5.

001-es BibID:BIBFORM033446
Első szerző:Oláh László (neurológus)
Cím:CO2 Reactivity Measured by Perfusion MRI During Transient Focal Cerebral Ischemia in Rats Editorial Comment / Olah, L., Franke, C., Schwindt, W., Hoehn, M., Fisher, M.
Dátum:2000
ISSN:0039-2499
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:Stroke. - 31 : 9 (2000), p. 2236-2244. -
További szerzők:Franke, Claudia Schwindt, Wolfram Hoehn, Mathias Fisher, Mark
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6.

001-es BibID:BIBFORM033453
Első szerző:van Dorsten, Ferdi A.
Cím:Dynamic changes of ADC, perfusion, and NMR relaxation parameters in transient focal ischemia of rat brain / van Dorsten F. A., Oláh L., Schwindt W., Grüne M., Uhlenküken U., Pillekamp F., Hossmann K. A., Hoehn M.
Dátum:2002
ISSN:0740-3194
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Magnetic Resonance In Medicine. - 47 : 1 (2002), p. 97-104. -
További szerzők:Oláh László (1967-) (neurológus) Schwindt, Wolfram Grüne, Matthias Uhlenküken, U. Pillekamp, F. Hossmann, Konstantin-Alexander Hoehn, Mathias
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