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Parameter estimation approach to banding artifact reduction in balanced steady‐state free precession
Author(s) -
Björk Marcus,
Ingle R. Reeve,
Gudmundson Erik,
Stoica Petre,
Nishimura Dwight G.,
Barral Joëlle K.
Publication year - 2014
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.24986
Subject(s) - estimator , computer science , algorithm , upper and lower bounds , reduction (mathematics) , precession , linearization , noise reduction , noise (video) , nonlinear system , mathematics , artificial intelligence , statistics , physics , image (mathematics) , mathematical analysis , geometry , astronomy , quantum mechanics
Purpose The balanced steady‐state free precession (bSSFP) pulse sequence has shown to be of great interest due to its high signal‐to‐noise ratio efficiency. However, bSSFP images often suffer from banding artifacts due to off‐resonance effects, which we aim to minimize in this article. Methods We present a general and fast two‐step algorithm for 1) estimating the unknowns in the bSSFP signal model from multiple phase‐cycled acquisitions, and 2) reconstructing band‐free images. The first step, linearization for off‐resonance estimation (LORE), solves the nonlinear problem approximately by a robust linear approach. The second step applies a Gauss‐Newton algorithm, initialized by LORE, to minimize the nonlinear least squares criterion. We name the full algorithm LORE‐GN. Results We derive the Cramér‐Rao bound, a theoretical lower bound of the variance for any unbiased estimator, and show that LORE‐GN is statistically efficient. Furthermore, we show that simultaneous estimation of T 1 and T 2 from phase‐cycled bSSFP is difficult, since the Cramér‐Rao bound is high at common signal‐to‐noise ratio. Using simulated, phantom, and in vivo data, we illustrate the band‐reduction capabilities of LORE‐GN compared to other techniques, such as sum‐of‐squares. Conclusion Using LORE‐GN we can successfully minimize banding artifacts in bSSFP. Magn Reson Med 72:880–892, 2014. © 2013 Wiley Periodicals, Inc.