Towards a better understanding of the meaning of diffusion kurtosis in the human briain. Insights from theoretical models and simulations
Summary
DKI is an emerging technique based on non-Gaussian water
diffusion analysis. A better explanation of the meaning of kurtosis in
terms of features of microstructural anatomy would make DKI more
concrete and accessible for clinicians. This work aims at a better understanding
on the meaning of kurtosis in the human brain. A literature
study is performed on possible causes of changes in kurtosis according
to some popular diffusion models. First we review some of these models
and their validity. Second we give an overview of anatomical links
between diffusion models and kurtosis metrics that are implied by the
reviewed models. Tortuousity differences, exchange, axon/neurite fraction,
axon radius, neurite orientation distribution, intrinsic axon/neurite
diffusivity, axon bending, bulging, breaking and crimping are in this
way found to affect kurtosis metrics. Axon orientation dispersion, CSF
contamination, astrocytes, trapped water and axon undulation could
possibly also affect kurtosis metrics. Several rules of thumb are stated
which provides anatomical explanations for a positively or negatively
observed change in a kurtosis metric