Statistical model for diffusion attenuated MR signal

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Abstract
A general statistical model that can describe a rather large number of experimental results related to the structure of the diffusion‐attenuated MR signal in biological systems is introduced. The theoretical framework relies on a phenomenological model that introduces a distribution function for tissue apparent diffusion coefficients (ADC). It is shown that at least two parameters—the position of distribution maxima (ADC) and the distribution width (σ)—are needed to describe the MR signal in most regions of a human brain. A substantial distribution width, on the order of 36% of the ADC, was found for practically all brain regions examined. This method of modeling the MR diffusion measurement allows determination of an intrinsic tissue‐specific ADC for a given diffusion time independent of the strength of diffusion sensitizing gradients. The model accounts for the previously found biexponential behavior of the diffusion‐attenuated MR signal in CNS. Magn Reson Med 50:664–669, 2003.