Can DTI and 3D-SHORE based indices differentiate RRMS from PMS Patients?

Multiple Sclerosis (MS) is a long-lasting disease of the brain and spinal cord, characterized by demyelinating lesions in white matter (WM) as well as cortical lesions and tissue volume loss in several grey matter (GM) structures. Although GM alterations are a common feature of MS, they have not been largely explored in literature. Diffusion Tensor Imaging (DTI) is nowadays used to investigate the damaged WM structures in MS since DTI-based indices, as Fractional Anisotropy (FA) and Mean Diffusivity (MD), have been proven to reflect the pathological features of the disease in many studies. However, DTI has been scarcely employed for GM analysis plus is not able to model the complex fiber architecture. Hence, advanced models are required to probe the microstructural pathology. One of this, the Simple Harmonic Oscillator Based Reconstruction and Estimation (SHORE), is a novel diffusion-weighted Magnetic Resonance Imaging (dMRI) analysis method which is considered a promising tool to characterize tissue microstructure thanks to its ability to detect multiple diffusion directions. In this study, we aimed to probe the viability of DTI and 3D-SHORE derived indices for characterizing the microstructural GM modulations in Relapsing Remitting Multiple Sclerosis (RRMS) and Progressive Multiple Sclerosis (PMS) patients by relying on histogram-based analyses.