STEAM-BURST - A SINGLE-SHOT, MULTISLICE IMAGING SEQUENCE WITHOUT RAPID GRADIENT SWITCHING

The stimulated-echo acquisition mode-Burst sequence is a single-shot, multi-slice imaging technique that does not involve rapid gradient swi tching. A Burst excitation pulse train is followed by a 90 degrees har d pulse and, after a mixing time, by a 90 degrees slice-selective puls e, A read gradient refocuses a set of stimulated echoes, which can be phase-encoded to form an image. By repeating the selective pulse N tim es, each time with the carrier frequency offset differently, it is pos sible to sample N slices in a single-shot, A comparison is made of the sequence with other three-dimensional single-shot methods, Experiment s implementing the technique on a 3 T whole-body imaging system and a 2 T, 31-cm bore animal imager are described. Both phantom and brain im ages are presented, The principal advantages of the new sequence are i ts speed, the absence of rapid gradient switching and corresponding fr eedom from artifacts, its insensitivity to static magnetic field inhom ogeneities, and its low acoustic noise, The main disadvantages are the low signal-to-noise ratio of the images produced and the concomitant limitation in resolution.