Models: Signal Representation vs. Microstructural Models

Since the introduction of diffusion tensor imaging (DTI), the diffusion MRI community has proven particularly prolific in introducing hundreds of new approaches to address some of the limitations of DTI. Particularly, new approaches have focused on leveraging modern diffusion MRI acquisitions to extract additional tissue properties compared to DTI, and to disentangle the orientation of complex fiber configurations. These efforts can typically be grouped into three categories: signal representations, microstructural models, and model free approaches. This chapter presents some popular approaches from the three categories and discusses how to acquire diffusion MRI data that satisfies the needs of such more advanced models.