title: A biexponential DWI study in rat brain intracellular oedema.
abstract: OBJECTIVE
  To examine the changes in MR parameters derived from diffusion weighted imaging (DWI) biexponential analysis in an in vivo intracellular brain oedema model, and to apply electron microscopy (EM) to shed more light on the morphological background of MR-related observations.
  
  
  METHODS
  Intracellular oedema was induced in ten male Wistar rats (380-450g) by way of water load, using a 20% body weight intraperitoneal injection of 140mmol/L dextrose solution. A 3T MRI instrument was used to perform serial DWI, and MR specroscopy (water signal) measurements. Following the MR examination the brains of the animals were analyzed for EM.
  
  
  RESULTS
  Following the water load induction, apparent diffusion coefficient (ADC) values started declining from 724±43μm(2)/s to 682±26μm(2)/s (p<0.0001). ADC-fast values dropped from 948±122 to 840±66μm(2)/s (p<0.001). ADC-slow showed a decrease from 226±66 to 191±74μm(2)/s (p<0.05). There was a shift from the slow to the fast component at 110min time point. The percentage of the fast component demonstrated moderate, yet significant increase from 76.56±7.79% to 81.2±7.47% (p<0.05). The water signal was increasing by 4.98±3.52% compared to the base line (p<0.01). The results of the E.M. revealed that water was detected intracellularly, within astrocytic preivascular end-feet and cell bodies.
  
  
  CONCLUSIONS
  The unexpected volume fraction changes (i.e. increase in fast component) detected in hypotonic oedema appear to be substantially different from those observed in stroke. It may suggest that ADC decrease in stroke, in contrast to general presumptions, cannot be explained only by water shift from extra to intracellular space (i.e. intracellular oedema).
authors.affiliation: Department of Neurosurgery, Faculty of Medicine University of Pécs, H-7623 Pécs, Rét street 2, Hungary. roy.steier@gmail.com
authors.forename: Roy
authors.initials: R
authors.lastname: Steier
authors.forename: Mihály
authors.initials: M
authors.lastname: Aradi
authors.forename: József
authors.initials: J
authors.lastname: Pál
authors.forename: Gábor
authors.initials: G
authors.lastname: Perlaki
authors.forename: Gergely
authors.initials: G
authors.lastname: Orsi
authors.forename: Péter
authors.initials: P
authors.lastname: Bogner
authors.forename: Ferenc
authors.initials: F
authors.lastname: Galyas
authors.forename: Péter
authors.initials: P
authors.lastname: Bukovics
authors.forename: József
authors.initials: J
authors.lastname: Janszky
authors.forename: Tamás
authors.initials: T
authors.lastname: Dóczi
authors.forename: Attila
authors.initials: A
authors.lastname: Schwarcz
mesh_terms: D000465:Algorithms; D000818:Animals; D001921:Brain / Q000473:pathology* / Q000648:ultrastructure*; D001929:Brain Edema / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity