Els Fieremans1,2, Yves De Deene2,3, Jens H. Jensen1, Joseph A. Helpern1
1Department of Radiology, CBI, New York University School of Medicine, New York, NY, USA; 2Department of Electronics and Information Systems, MEDISIP, Ghent University-IBBT-IBiTech, Ghent, Belgium; 3Department of Radiotherapy and Nuclear Medicine, QMRI, Ghent University, Ghent, Belgium
The diffusion weighted MR-signal attenuation in brain white matter is not mono-exponential. A bi-exponential model has been proposed since this fits the data well. We have modeled the diffusion weighted MR-signal by Monte Carlo simulations in a fiber geometry similar to brain white matter. Although a bi-exponential model fitted the data very well, the fitted diffusion coefficients and fractions did not converge to the simulated values in the intra- and extracellular space. However, fitting the cumulant expansion form terminated after the Nth order term to the data results in accurate fits for the diffusion coefficient and kurtosis.