Premium
Microstructural changes in ischemic cortical gray matter predicted by a model of diffusion‐weighted MRI
Author(s) -
VestergaardPoulsen Peter,
Hansen Brian,
Østergaard Leif,
Jakobsen Rikke
Publication year - 2007
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21030
Subject(s) - diffusion , ischemia , diffusion mri , effective diffusion coefficient , white matter , diffusion imaging , brain tissue , nuclear magnetic resonance , intracellular , chemistry , biomedical engineering , magnetic resonance imaging , physics , medicine , thermodynamics , cardiology , radiology , biochemistry
Purpose To understand the diffusion attenuated MR signal from normal and ischemic brain tissue in order to extract structural and physiological information using mathematical modeling, taking into account the transverse relaxation rates in gray matter. Materials and Methods We fit our diffusion model to the diffusion‐weighted MR signal obtained from cortical gray matter in healthy subjects. Our model includes variable volume fractions, intracellular restriction effects, and exchange between compartments in addition to individual diffusion coefficients and transverse relaxation rates for each compartment. A global optimum was found from a wide range of parameter permutations using cluster computing. We also present simulations of cell swelling and changes of exchange rate and intracellular diffusion as possible cellular mechanisms in ischemia. Results Our model estimates an extracellular volume fraction of 0.19 in accordance with the accepted value from histology. The absolute apparent diffusion coefficient obtained from the model was similar to that of experiments. The model and the experimental results indicate significant differences in diffusion and transverse relaxation between the tissue compartments and slow water exchange. Our model reproduces the signal changes observed in ischemia via physiologically credible mechanisms. Conclusion Our modeling suggests that transverse relaxation has a profound influence on the diffusion attenuated MR signal. Our simulations indicate cell swelling as the primary cause of the diffusion changes seen in the acute phase of brain ischemia. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.