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On the fluid‐tissue contrast behavior of high‐resolution steady‐state sequences
Author(s) -
Bieri Oliver,
Ganter Carl,
Scheffler Klaus
Publication year - 2012
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.24154
Subject(s) - precession , steady state (chemistry) , contrast (vision) , diffusion , nuclear magnetic resonance , anisotropy , resolution (logic) , larmor precession , physics , voxel , diffusion mri , materials science , chemistry , optics , condensed matter physics , magnetic resonance imaging , thermodynamics , magnetic field , medicine , computer science , radiology , quantum mechanics , artificial intelligence
In general, MR image contrast is expected to be resolution independent, but a pronounced loss of contrast is observed between fluids and tissues with contemporary musculoskeletal protocols (typical inplane resolution << 1 mm) using nonbalanced steady‐state free precession, such as double echo steady state. For nonbalanced steady‐state free precession, diffusion sensitivity increases with increasing spoiler moments which increase with decreasing voxel size, suggesting diffusion damping as the major cause for the observed contrast variation. This is confirmed by simulations and measurements indicating that for fluids, diffusion effects become apparent already for resolutions Δ x < 1 mm, whereas tissues typically require Δ x < 200 μm. Gradient spoiling, however, is generically not minimized but frequently applied along the readout direction. For anisotropic steady‐state free precession scans, the loss of contrast between fluids and tissues from diffusion can thus be minimized by simply moving the spoiler gradients to the lowest resolution direction. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.