ABSTRACT
Diffusion MRI (dMRI) has been widely utilized to probe the random motion of water molecules in tissues. In a dMRI acquisition protocol, diffusion weighting or b-value is one of the most important parameters to consider. In recent years, high and ultrahigh b-values have become popular partly due to advances in hardware. In this mini-review, we will discuss impacts of high/ultrahigh b-values in three different areas: brain microstructure, tractography, and clinical applications. We will emphasize advantages of high b-value in probing diffusion within highly restricted regions or fine structures with enhanced diffusion contrast. A short summary is included at the end of each section to illustrate both advantages and disadvantages of using a high/ultrahigh b-value for each purpose.