Fast spin-echo imaging of the brain.

Fast spin-echo (FSE) imaging is a recently modified rapid-acquisition relaxation-enhanced technique that affords rapid magnetic resonance (MR) imaging while retaining true spin-echo (SE) contrast features. By manipulating factors such as echo train length, echo spacing, and order of phase encoding, dual-echo brain images currently may be obtained many times faster than with conventional SE techniques. The time advantage of FSE may be used simply to obtain images much more rapidly or to acquire images of much higher contrast or spatial resolution compared with conventional SE images in a comparable period of time. Lesion appearance and conspicuity are usually quite similar to those on conventional SE images, with the important exception of some hemorrhagic blood products, which may appear less conspicuous on FSE images because of reduced magnetic susceptibility effects. Another important difference is the bright appearance of fat on all routine FSE sequences (T1-weighted, proton-density, and T2-weighted), although this may be eliminated easily by using routine fat-suppression techniques. Recent applications of FSE include three-dimensional multislab imaging and high-resolution imaging with large-matrix, small-field of view, thin-slice, and multiple-excitation imaging parameters. FSE techniques appear quite promising for rapid MR imaging of the brain, and they have largely replaced conventional SE technique at some institutions.