FAT-SUPPRESSION TECHNIQUES IN MRI - AN UPDATE

Due to short relaxation times, fat has a high signal on magnetic reson ance images (MRI). This high signal, easily recognized on MRI, may be useful to characterize a lesion. However, small amounts of lipids are more difficult to detect on conventional MRI. In addition, the high si gnal due to fat may be responsible for artifacts such as ghosting and chemical shift. Lastly, a contrast enhancing tumor may be hidden by th e surrounding fat. These problems have prompted development of fat sup pression techniques in MRI. Fat may be suppressed on the basis of its difference in resonance frequency with water by means of frequency sel ective pulses or phase contrast techniques, or on the basis of its sho rt T1 relaxation time by means of inversion recovery sequences. Lastly , hybrid techniques combining several of these fat suppression techniq ues are also possible. The aim of this paper is to review the basic pr inciples of all these fat suppression techniques and to exemplify thei r clinical use. (C) 1998 Elsevier, Paris.