EPI

Echo-planar imaging — ultra-fast sequence that acquires a whole image in one TR. Basis for diffusion (DWI) and functional MRI (fMRI).

Why it matters to buyers: Gates fMRI and DWI capability. High gradient + slew rate required; not all scanners support robust EPI.

Why it matters to engineers: Susceptible to geometric distortion near air-tissue interfaces. Requires good shim.