[Fast and ultra-fast magnetic resonance tomography. Basic principles, pulse sequences and special properties]

The aim of this article is the systematic treatment of fast and ultrafast magnetic resonance imaging (MRI) techniques. Based on the basic principles of signal generation and spatial encoding with magnetic field gradients the differences and important similarities of pulse sequences will be explained. We suggest to replace the conventional grouping of pulse sequences in gradient and spin-echo sequences through single and multi-echo sequences, since the latter is more precise and helpful. We illustrate how single-echo sequences such as "spin-echo", FLASH, FISP, PSIF, CISS and DESS can be derived from a single gradient echo and how multi-echo sequences such as turbo spin-echo RARE, HASTE and GRASE are based on echo-planar imaging. The different properties, advantages and disadvantages of the various sequences will be discussed and frequently used acronyms will be explained.