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Analysis of mcDESPOT‐ and CPMG‐derived parameter estimates for two‐component nonexchanging systems
Author(s) -
Bouhrara Mustapha,
Reiter David A.,
Celik Hasan,
Fishbein Kenneth W.,
Kijowski Richard,
Spencer Richard G.
Publication year - 2016
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.25801
Subject(s) - estimation theory , stability (learning theory) , monte carlo method , range (aeronautics) , maxima and minima , reliability (semiconductor) , statistical physics , physics , nuclear magnetic resonance , mathematics , statistics , computer science , mathematical analysis , materials science , quantum mechanics , power (physics) , machine learning , composite material
Purpose To compare the reliability and stability of the multicomponent‐driven equilibrium single pulse observation of T 1 and T 2 (mcDESPOT) and Carl‐Purcell‐Meiboom‐Gill (CPMG) approaches to parameter estimation. Methods The stability and reliability of mcDESPOT and CPMG‐derived parameter estimates were compared through examination of energy surfaces, evaluation of model sloppiness, and Monte Carlo simulations. Comparisons were performed on an equal time basis and assuming a two‐component system. Parameter estimation bias, reflecting accuracy, and dispersion, reflecting precision, were derived for a range of signal‐to‐noise ratios (SNRs) and relaxation parameters. Results The energy surfaces for parameters incorporated into the mcDESPOT signal model exhibit flatness, a complex structure of local minima, and instability to noise to a much greater extent than the corresponding surfaces for CPMG. Although both mcDESPOT and CPMG performed well at high SNR, the CPMG approach yielded parameter estimates of considerably greater accuracy and precision at lower SNR. Conclusion mcDESPOT and CPMG both permit high‐quality parameter estimates under SNR that are clinically achievable under many circumstances, depending upon available hardware and resolution and acquisition time constraints. At moderate to high SNR, the mcDESPOT approach incorporating two‐step phase increments can yield accurate parameter estimates while providing values for longitudinal relaxation times that are not available through CPMG. However, at low SNR, the CPMG approach is more stable and provides superior parameter estimates. Magn Reson Med 75:2406–2420, 2016. © 2015 Wiley Periodicals, Inc.