Exploiting the Phase in Diffusion MRI for Microstructure Recovery: Towards Axonal Tortuosity via Asymmetric Diffusion Processes

Marco Pizzolato (1) , Demian Wassermann (1) , Timothé Boutelier (2) , Rachid Deriche (1)

1 ATHENA - Computational Imaging of the Central Nervous System
2 Olea Medical [La Ciotat]

Microstructure recovery procedures via Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) usually discard the signal's phase, assuming symmetry in the underlying diffusion process. We propose to recover the Ensemble Average Propagator (EAP) directly from the complex DW signal in order to describe also eventual diffusional asymmetry, thus obtaining an asymmetric EAP. The asymmetry of the EAP is then related to tortuosity of undulated white matter axons, which are found in pathological scenarios associated with axonal elongation or compression. We derive a model of the EAP for this geometry and quantify its asymmetry. Results show that the EAP obtained when accounting for the DW signal's phase provides useful microstructural information in such pathological scenarios. Furthermore, we validate these results in-silico through 3D Monte-Carlo simulations of white matter tissue that has experienced different degrees of elongation/compression.

Mots clés: tortuosity; axon; diffusion MRI; asymmetry; EAP; phase

Domaines: Traitement du signal et de l'image [eess.SP]; Modélisation et simulation

Marco Pizzolato, Demian Wassermann, Timothé Boutelier, Rachid Deriche. Exploiting the Phase in Diffusion MRI for Microstructure Recovery: Towards Axonal Tortuosity via Asymmetric Diffusion Processes. Medical Image Computing and Computer Assisted Intervention, 2015, Munich, Germany. ⟨10.1007/978-3-319-24553-9_14⟩. ⟨hal-01152672⟩