Premium
Identification of signal bias in the variable flip angle method by linear display of the algebraic ernst equation
Author(s) -
Helms Gunther,
Dathe Henning,
Weiskopf Nikolaus,
Dechent Peter
Publication year - 2011
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.22849
Subject(s) - flip angle , signal (programming language) , amplitude , relaxation (psychology) , pulse (music) , noise (video) , tangent , algorithm , physics , mathematical analysis , mathematics , optics , computer science , nuclear magnetic resonance , geometry , artificial intelligence , medicine , psychology , social psychology , detector , magnetic resonance imaging , image (mathematics) , radiology , programming language
Abstract A novel linear parameterization for the variable flip angle method for longitudinal relaxation time T 1 quantification from spoiled steady state MRI is derived from the half angle tangent transform, τ, of the flip angle. Plotting the signal S at coordinates x = Sτ and y = S /τ, respectively, establishes a line that renders signal amplitude and relaxation term separately as y ‐intercept and slope. This representation allows for estimation of the respective parameter from the experimental data. A comprehensive analysis of noise propagation is performed. Numerical results for efficient optimization of longitudinal relaxation time and proton density mapping experiments are derived. Appropriate scaling allows for a linear presentation of data that are acquired at different short pulse repetition times, TR << T1 thus increasing flexibility in the data acquisition by removing the limitation of a single pulse repetition time. Signal bias, like due to slice‐selective excitation or imperfect spoiling, can be readily identified by systematic deviations from the linear plot. The method is illustrated and validated by 3T experiments on phantoms and human brain. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.