MASTER : a multivariate axonal simulator for tractography e valuation in R towards reliable reconstruction of brain white matter fascicles

Our brain receives and processes information via neurons, which are cells connected together by axons, grouped into dense bundles called fascicles. When these latter are damaged, parts of the body functions might be defective, which might lead to fatal outcomes for patients. However, the axonal cytoarchitecture of the brain is not visible to the naked eye. It is thus of critical importance for the diagnosis and treatment of brain disorders to depict as accurately as possible and in the most reproducible fashion this cytoarchitecture. Using mathematical models, for instance, brain tumor removal surgery would be greatly improved if such reconstructions could be reliably provided. Diffusion MRI enables in-vivo and non-invasive reconstruction of such fascicles. However this reconstruction is prone to external influences, such as imaging artifacts and noise; moreover it involves a number of non-trivial modeling steps which have not been successfully validated yet. This motivated the realization of both hardware and software frameworks, on which to test reconstruction algorithms, which unfortunately are not able to correctly deal with complex configurations of fascicles or, alternatively, lack ground truth. There is thus an urgent unmet need for a validation tool able to correctly reproduce the white matter cytoarchitecture. To overcome this problem we propose master, a Multivariate Axonal Simulator for Tractography Evaluation in R, which enables to simulate the white matter fascicles configurations. master has been developed with the open-source statistical software R. It is the result of a deep study of the white matter cytoarchitecture, which brought us to innovatively reproduce each fascicle configuration from a single simple mathematical model with few, and very intuitive, input parameters that are relevant to a reliable cytoarchitecture reconstruction. master is available both as R-package and as web application; moreover its portability is enhanced thanks to the possibility to export simulated data as .csv files.