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Spin‐echo micro‐MRI of trabecular bone using improved 3D fast large‐angle spin‐echo (FLASE)
Author(s) -
Magland J.F.,
Wald M.J.,
Wehrli F.W.
Publication year - 2009
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21905
Subject(s) - nuclear magnetic resonance , isotropy , spin echo , fast spin echo , pulse sequence , anisotropy , physics , materials science , optics , magnetic resonance imaging , medicine , radiology
Fast large‐angle spin echo (FLASE) is a common pulse sequence designed for quantitative imaging of trabecular bone (TB) microarchitecture. However, imperfections in the nonselective phase‐reversal pulse render it prone to stimulated echo artifacts. The problem is further exacerbated at isotropic resolution. Here, a substantially improved RF‐spoiled FLASE sequence (sp‐FLASE) is described and its performance is illustrated with data at 1.5T and 3T. Additional enhancements include navigator echoes for translational motion sensing applied in a slice parallel to the imaging slab. Whereas recent work suggests the use of fully‐balanced FLASE (b‐FLASE) to be advantageous from a signal‐to‐noise ratio (SNR) point of view, evidence is provided here that the greater robustness of sp‐FLASE may outweigh the benefits of the minor SNR gain of b‐FLASE for the target application of TB imaging in the distal extremities, sites of exclusively fatty marrow. Results are supported by a theoretical Bloch equation analysis and the pulse sequence dependence of the effective T 2 of triglyceride protons. Last, sp‐FLASE images are shown to provide detailed and reproducible visual depiction of trabecular networks in three dimensions at both anisotropic (137 × 137 × 410 μm 3 ) and isotropic (160 × 160 × 160 μm 3 ) resolutions in the human distal tibia in vivo. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.