The brain is made of three main structures : the white matter (WM), the gray matter (GM), and the CSF. The WM is made of fibers (axons surrounded by a myelin sheath) whose goal is to connect various regions of the gray matter as well as the spinal cord. The WM has been shown to be at the centre of several neurodegenerative diseases such as Parkinson, Alzheimer, Multiple-Sclerosis and traumatic brain injuries to name a few. With diffusion magnetic resonance images (dMRI) and the latest image processing software, it is now possible to measure microstructural information within the WM such as the amount of free water (and thus inflammation) around the axons, the amount of myelin and the apparent density of fibers. Interesting enough, these metrics have been largely documented to correlate with several neuro-degenerative diseases and thus can be use to diagnose those diseases, track it over time and measure the microstructural effect of new drugs.
But dMRI is not void of limitation as its images do not come with a standard measuring unit. As such, in order to determine if the dMRI metrics of a patient deviate from normality and are the sign of a disease, one needs a reference atlas (typically from healthy or baseline patients) to compare against. The overarching objective of this project is to measure the brain microstructural metrics of a large population of healthy subjects in order to build a WM reference atlas. The atlas will account for male and female, people of different handedness, different ethnic background and of various age. With this at hand, we hope to show how clinicians in their day-to-day practice can use such a reference atlas to benchmark the WM integrity of subjects suspected to suffer from a neurodegenerative disease. We expect this atlas to have the same impact on the neuroscience community that the growth charts had on the pediatric practice many years ago.