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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 25:692-698, May 2004
© 2004 American Society of Neuroradiology

BRAIN

Water Diffusion Compartmentation at High b Values in Ischemic Human Brain

Pierre Brugières^a,c, Philippe Thomas^a, Anne Maraval^a, Hassan Hosseini^b,c, Catherine Combes^a, Abdallah Chafiq^a, Lucile Ruel^a,b,c, Stéphane Breil^a,b,c, Marc Peschanski^c and André Gaston^a

^a Department of Neuroradiology and Neurology, Créteil; Siemens SA, St Denis
^b Department of Henri Mondor Hospital, Neurology, Créteil; Siemens SA, St Denis
^c INSERM U421, Créteil, France

Address reprint requests to Pierre Brugières, Henri Mondor Hospital, Neuroradiology, 51 ave du Mal de Lattre de, Tassigny, Créteil 94000, France

BACKGROUND AND PURPOSE: We studied the evolution of brain water compartments during the early stage of ischemic stroke.

METHODS: Diffusion-weighted imaging was performed at 1.5 T in 10 volunteers and 14 patients with stroke. We used a single-shot echo-planar technique with 11 b values of 0–5000 s/mm². Regions of interest were selected in the white matter (WM) and striatum of the volunteers and in the ischemic core of the patients. Measurements were fitted on the basis of a biexponential decay with the b factor as follows: S(b) = S(0)[(f_slow x exp(–b x ADC_slow) + (f_fast x exp(–b xADC_fast)] where S(b) is the signal intensity in the presence of a diffusion gradient, S(0) is the signal intensity without diffusion sensitization, ADC_slow and ADC_fast are the respective apparent diffusion coefficients (ADCs) of slow diffusing compartments (SDCs) and fast diffusing compartments (FDCs), and f_slow and f_fast the respective contributions to the signal intensity of SDC and FDC.

RESULTS: In healthy subjects, FDC represents 74.3 ± 3.1% of brain water, with ADC_fast = (124.6 ± 12.0) x 10^–5 mm²/s and ADC_slow = (15.5 ± 3.9) x 10^–5 mm²/s. In stroke, decreased FDC (49.1% ± 10.9%; P = 1.05 x10^–5) and increased ADC_slow ([22.4 ± 8.1] x 10^–5 mm²/s; P = 8.07 x 10^–3) were observed, but ADC_fast was not significantly changed ([135.6 ± 25.7] x 10 ^–5 mm²/s; P = .151).

CONCLUSION: The restricted diffusion observed in the early stroke is mainly related to a redistribution of water from the FDC to the SDC.