title: Separating changes in the intra- and extracellular water apparent diffusion coefficient following focal cerebral ischemia in the rat brain.
abstract: Selective intracellular (IC) and extracellular (EC) brain water apparent diffusion coefficient (ADC) values were measured in normal and ischemic rat brain. Selective T(1)-relaxation enhancement of the EC water, using intracerebroventricular (ICV) infusion of an NMR contrast reagent (CR), was used to separate the IC and EC signal contributions. In the CR-infused, normal brain (n = 4), T(1) = 235 +/- 10 ms and T(2) = 46 +/- 2 ms for IC water (85%) and T(1) = 48 +/- 8 ms and T(2) = 6 +/- 2 ms for EC water (15%). Volume-localized ADC(z) (z-gradient axis) values were 0.90 +/- 0.02 (EC+IC), 0.81 +/- 0.05 (IC), 0.51 +/- 0.02 (EC+IC), and 0.53 +/- 0.07 (IC), for normal, CR-infused, ischemic, and ischemic/CR-infused groups, respectively (ADC values are x10(-3) mm(2)/s; n = 5 for each group). Imaging ADC(z) values were 0.81 +/- 0.03 (EC+IC), 0.75 +/- 0.05 (IC), 0.51 +/- 0.04 (EC+IC), and 0.52 +/- 0.05 (IC), respectively, for the same groups. Imaging ADC(av) (average diffusivity) values for the same groups were 0.70 +/- 0.05 (EC+IC), 0.69 +/- 0.06 (IC), 0.45 +/- 0.06 (EC+IC), and 0.44 +/- 0.06 (IC), respectively. These results suggest that the IC water ADC determines the overall water ADC value in normal and ischemic rat brain.
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Silva
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Omae
authors.forename: Karl G
authors.initials: KG
authors.lastname: Helmer
authors.forename: Fuhai
authors.initials: F
authors.lastname: Li
authors.forename: Marc
authors.initials: M
authors.lastname: Fisher
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Sotak
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005110:Extracellular Space / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013057:Spectrum Analysis; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water