New MRI sequences.

Every year, manufacturers of MRI machines introduce new sequences. Most of them result in improved spatial resolution and signal contrast, occasionally with a decrease in sequence duration or MRI time (as when a single 3D sequence is substituted for three 2D sequences). Some sequences that are specifically designed to obtain structural or functional information about a specific tissue (ultrashort TE, T2 mapping, spectro-MRI) are used only for research purposes. Diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and tractography constitute an original microarchitectural approach based on water molecule diffusion. These methods are nearly ready to be introduced into clinical practice. They are discussed in this article.