A New Evaluation of the Brain Parenchymal Fraction: Application in Multiple Sclerosis Group or Longitudinal Studies

In multiple sclerosis (MS) research, burden of disease and treatments efficacy are mainly evaluated with lesion load and atrophy. The former being poorly correlated with patient’s handicap, it is of interest to evaluate accurately the latter. A lot of methods to measure the brain atrophy as the brain parenchymal fraction (BPF) are available in the literature. The BPF needs a precise segmentation of the brain and of the Cerebro-Spinal Fluid. However artefacts like partial volume effects (PVE) can impair this classification. According to some articles, the BPF may also be less precise in longitudinal studies. To address these points, this article proposes a new method to evaluate the BPF thanks to an ExpectationMinimization framework taking into consideration PVE. Modifications of the pipeline are also proposed to improve its reliability in longitudinal study. Experiments have been conducted on simulated pathological images that validate the different measures.