title: Temporal and regional changes during focal ischemia in rat brain studied by proton spectroscopic imaging and quantitative diffusion NMR imaging.
abstract: The early development of focal ischemia after permanent occlusion of the right middle cerebral artery (MCA) was studied in six rats using interleaved measurements by diffusion-weighted NMR imaging (DWI) of water and two variants of proton spectroscopic imaging (SI), multiecho SI (TE: 136, 272, 408 ms) and short TE SI (TE: 20 ms). Measurements on a 4.7-T NMR imaging system were performed between the control phase and approximately 6 h postocclusion. In the center of the ischemic lesion of all rats, the apparent diffusion coefficient (ADC) decreased rapidly to 84.4 +/- 4.2% (mean +/- SD) of the control values approximately 2 min postocclusion. Approximately 6 h postocclusion, the ADC was reduced to 67.1 +/- 5.9%. In contrast, large differences between the animals were observed for the temporal increase of lactate (Lac) in the ipsilateral hemisphere. The maximum Lac signal was reached in four rats after 0.5-1.5 h, and in two rats was not reached even after 6 h postocclusion. Six h postocclusion, SI spectra measured at a TE of 136 ms revealed a decrease in the CH3 signal of N-acetylaspartate (NAA) to 67 +/- 13% of the control values. Differences were observed between the spatial regions of decreased NAA and increased Lac. In the lesions, a T2 relaxation time of Lac of 292 +/- 40 ms, considering a J-coupling constant of 6.9 Hz, was measured. Furthermore, a prolongation of the T2 of the CH3 signal of creatine/phosphocreatine (Cr/PCr) was observed in the lesion, from 163 +/- 22 ms during control to 211 +/- 41 ms approximately 6 h postocclusion. The experiments proved that DWI and proton SI are valuable tools to provide complementary information on processes associated with brain infarcts.
authors.affiliation: Universität Bremen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Dreher
authors.forename: B
authors.initials: B
authors.lastname: Kühn
authors.forename: M L
authors.initials: ML
authors.lastname: Gyngell
authors.forename: E
authors.initials: E
authors.lastname: Busch
authors.forename: T
authors.initials: T
authors.lastname: Niendorf
authors.forename: K A
authors.initials: KA
authors.lastname: Hossmann
authors.forename: D
authors.initials: D
authors.lastname: Leibfritz
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D002544:Cerebral Infarction / Q000175:diagnosis / Q000503:physiopathology*; D003401:Creatine / Q000378:metabolism; D004058:Diffusion; D004292:Dominance, Cerebral / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D019344:Lactic Acid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D008297:Male; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values
chemical_list: D001786:Blood Glucose; D010725:Phosphocreatine; D001224:Aspartic Acid; D019344:Lactic Acid; C000179:N-acetylaspartate; D003401:Creatine