Single-shell diffusion models: From DTI to HARDI

This chapter provides a comprehensive overview of single-shell diffusion models and methods that have played a significant role in the development and application of tractography. It begins with an introduction to diffusion tensor imaging (DTI), discussing its fundamental role in diffusion imaging and tractography. The chapter then explores High Angular Resolution Diffusion Imaging (HARDI) and its impact on creating new generations of methods capable of extracting multiple fiber orientations within individual voxels. A range of approaches is reviewed, including multitensor methods and nonparametric techniques, offering insights into their strengths and limitations. Particular emphasis is placed on spherical deconvolution methods, detailing their evolution and refinements that have helped establish them as preferred solutions for many contemporary tractography applications. The chapter aims to be accessible to a broad readership, providing practical advice on how to apply these approaches in research and clinical settings.