The diffusion MRI signal arising from neurons can be numerically simulated by solving the Bloch-
Torrey partial differential equation. In a previous work [Fang et al., NeuroImage, 2020], we constructed high quality finite element meshes for a set of human neurons whose morphological descriptions were found in the publicly available neuron repository NeuroMorpho.Org. To produce a
database of simulated diffusion MRI signals under a large number of experimental acquisition conditions, we numerically computed the eigenfunctions and the eigenvalues of the Laplace operators
on the full set of neuron geometries using a P1 finite elements discretization and stored the relevant
simulation data. A preliminary statistical study on a small subset of neurons was performed to test
some candidate biomakers that can potentially indicate the soma size.
In this PhD project, we propose a systematic analysis of the connection between the diffusion MRI
signal and neuron morphology by conducting statistical studies on a large number of neurons, using
the Bloch-Torrey PDE model that connects the neuron geometry to the diffusion MRI signal. We
also plan to produce robust machine learning algorithms that can output selected morphological
properties from the diffusion MRI signals. Finally, as usual, we will make resulting software and
data available for public use.
Below is a preliminary roadmap for the project.
1. Familiarize with and add to our database of over 1000 human neurons (high quality finite
elements meshes) and their morphological properties;
2. Run and store the simulated diffusion MRI signals under many different experimental conditions for the full set of neurons, by running the Matrix Formalism solver [Li et al. NMR in
Biomedicine, 2020] (numerical computation of Laplace eigenfunctions) from the SpinDoctor toolbox [Li et al. Neuroimage. 2019].
3. From the simulated diffusion MRI signals, explain the relationships found between candidate
biomakers and soma size.
4. Incorporate additional morphological properties such as total dendrite length and dendrite to
soma ratio to the statistical study.
5. Test, implement, and optimize machine learning algorithms that robustly output selected
morphological properties from the diffusion MRI signals.
6. Analyse the connections between the input-output relationships from the chosen machine
learning algorithms and the underlying properties of the Bloch-Torrey PDE.