There is working machinery in some fields, who have been majorly ruling the big journals for over a decade and never let new people contribute. Tried convincing that DTI with global scale factor based conductivity tensor is wrong. Thread...
Electrical conductivity is an intrinsic material property and primarily determined by ion concentration and mobility. Electrical conductivity doesn’t generate its contrast, so we need to externally energize the domain need to externally induce or inject electrical current.
Accurate current density, electric field distribution, or forward modeling requires subject-specific conductivity information of the brain. Brain tissues especially white matter is highly anisotropic so the term anisotropic conductivity or conductivity tensor is exercised.
Almost all existed modeling studies used either literature values of conductivity in the segmented model or more advanced calculated from water diffusion tensor.
Coming to the diffusion tensor-based conductivity tensor reconstruction. In early 2000, A proposed linear relationship model that assumes that the conductivity tensors share the same eigenvectors with water diffusion tensors, and their eigenvalues satisfy a linear relationship
which means conductivity tensor is proportional to water diffusion tensor and that proportionality depends upon scale factor. The scale factor is known as eta.
Coming to this scale factor which is important and needs to be understood carefully, the eta was defined as ECDR which is extracellular conductivity and diffusivity ratio.
Tuch et al. derived a rigorous linear relation between conductivity and diffusion tensors by relating the two transport processes through the statistical moments of brain tissue microstructure and got a conversion coefficient. Which is globally multiplied by diffusion tensor.
The linear relation model is based on the medium theory and does not directly consider the impact of the geometrical structure of brain tissues or heterogeneity. It reveals the mathematical relationship between the two kinds of tensors from the theoretical perspective.
A non-significant amount of work followed and none has tried to decompose the term eta or any additional information to the linear relationship model. Some used literature conductivity and trace (D) in ECDR.
Hereby, attaching one simple phantom experiment with results from all the existed conductivity reconstruction methods. 
Two different electrolytes with different NaCl amount. Except for model #3 none has shown the effect of ion concentration change. Even if we see the results from model #3, where we use literature and trace D ratio, conductivity values are incorrect. Should be doubled
The irony is the first three models have been highly used for brain modeling studies.
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