T2‐weighted thin‐section imaging with the multislab three‐dimensional RARE technique

A novel three‐dimensional (3D) RARE (rapid acquisition with relaxation enhancement) sequence was implemented on a clinical imager. In this technique, multiple slabs are excited in the same way as in the multisection spin‐echo sequence, and each slab is further phase encoded into eight sections along the section‐slab direction. With a 16‐echo RARE sequence, 128 excitations cover the 256 × 256 × 8 3D k space. With a TR of 2.500 msec, 10 slabs can be excited sequentially at each TR, yielding 80 sections in 5 minutes. Slabs were overlapped to give contiguous sections after discarding of the aliased sections at slab edges. This relatively fast sequence makes contiguous thin‐section T2‐weighted imaging possible, an impractical achievement with the much longer spin‐echo method. Compared with 3D Fourier transform gradient‐echo imaging, the sensitivity of 3D RARE sequences to magnetic susceptibility is reduced. The clinical potential of T2‐weighted 3D imaging is illustrated with high‐resolution brain, spine, and temporomandibular joint images.