Comparison of three-dimensional fast spin echo and gradient echo sequencesfor high-resolution temporal bone imaging

T2-weighted high-resolution gradient and fast spin echo sequences are widel y used as an alternative or adjunct to contrast-enhanced T1-weighted tempor al bone imaging. However, to date no systematic comparison has been present ed. The purpose of this work is to identify optimal acquisition parameters and to compare volume gradient and fast spin echo techniques. Signal intens ities and scan efficiency were computed for gradient echo segment-interleav ed motion-compensated acquisition into steady state (SIMCAST), standard fas t spin echo (FSE), and fast recovery fast spin echo (FR-FSE). Computations were compared with inner ear images acquired with cubic vowel sizes of 0.35 -0.40 mm(3) in 5-8 minutes. Given otherwise identical conditions, the FR-FS E sequence produces images with improved SNR in shorter scan times than sta ndard FSE. For FR-FSE, the scan efficiency is optimal for specific pairs of TR and echo train length, eg, 400 ms/8, 735 ms/16, and 2,050 ms/48. FR-FSE images with large TR and echo trains, while achieving better SNR, are seve rely compromised by blurring. Imaging with echo train lengths of 16-24 and TR of 800-1,200 ms is a good compromise, and FR-FSE signal-to-noise ratio ( SNR) and scan efficiency become comparable to SIMCAST. In vivo image qualit y is excellent with both FR-FSE and SIMCAST, but SIMCAST images have slight ly higher SNR and are significantly more crisp. (C) 2000 Wiley-Liss, Inc.