Coherence-induced artifacts in large-flip-angle steady-state spin-echo imaging
Article first published online: 23 JUL 2004
Copyright © 2004 Wiley-Liss, Inc.
Magnetic Resonance in Medicine
Volume 52, Issue 2, pages 346–353, August 2004
How to Cite
Vasilic, B., Song, H. K. and Wehrli, F. W. (2004), Coherence-induced artifacts in large-flip-angle steady-state spin-echo imaging. Magn Reson Med, 52: 346–353. doi: 10.1002/mrm.20156
- Issue published online: 23 JUL 2004
- Article first published online: 23 JUL 2004
- Manuscript Accepted: 9 MAR 2004
- Manuscript Revised: 5 FEB 2004
- Manuscript Received: 9 DEC 2003
- NIH. Grant Numbers: RO1 AR41443, RO1 AR049553
High-resolution imaging of trabecular bone aimed at analyzing the bone's microarchitecture is preferably performed with spin-echo-type pulse sequences. Unlike gradient echoes, spin-echoes are immune to artifactual broadening of trabeculae caused by local static field gradients near the bone–bone marrow interface and signal loss from chemical shift dephasing at k-space center. However, the previously practiced 3D fast large-angle spin-echo (FLASE) pulse sequence was found to be prone to a low-frequency modulation artifact in both the readout and slice direction. The artifact is caused by deviations in the effective flip angle of the nonselective 180° pulse, which converts a fraction of the phase-encoded transverse magnetization to longitudinal magnetization. The latter recurs as transverse magnetization in the subsequent pulse sequence cycle forming a spurious stimulated echo. The objective of this work was to perform a k-space analysis of this steady-state artifact and propose two modifications of the original 3D FLASE that effectively remove it. The results of the simulations were in exact agreement with the experiments and the proposed remedy was found to eliminate the artifact. Magn Reson Med 52:346–353, 2004. © 2004 Wiley-Liss, Inc.