Correction of main and transmit magnetic field (B0 and B1) inhomogeneity effects in multicomponent‐driven equilibrium single‐pulse observation of T1 and T2

Deoni, Sean

doi:10.1002/mrm.22685

Cited by 98 publications

(152 citation statements)

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“…One of these techniques relies on multiple sets of spoiled gradient-recalled echo and balanced steady state free precession data acquired with multiple flip angles (Deoni, 2011;Deoni et al, 2008). The multicomponent driven-equilibrium single-pulse observation of T 1 and T 2 (mcDESPOT) technique affords whole brain coverage in approximately 15 minutes.…”

Section: Discussionmentioning

confidence: 99%

Rapid whole cerebrum myelin water imaging using a 3D GRASE sequence

et al. 2012

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Section: Discussionmentioning

confidence: 99%

Rapid whole cerebrum myelin water imaging using a 3D GRASE sequence

et al. 2012

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“…mcDESPOT is based on the use of SPGR and bSSFP datasets, each acquired over a range of FAs, with very short TR (18, 32). Neglecting exchange between components, the two-component SPGR signal is conventionally given by (33)

M_{S P G R}^{k} = M_{S P G R}^{0} sin (B_{1} α_{k}) true(f_{s} \frac{1 - E_{1, s}}{1 - E_{1, s} cos (B_{1} α_{k})} + (1 - f_{s}) \frac{1 - E_{1, l}}{1 - E_{1, l} cos (B_{1} α_{k})} true)

where the dimensionless quantity B 1 denotes an RF transmit scaling factor, s and l respectively denote the short- and long- T 2 components, f s is the fraction of the short T 2 component,

M_{0}^{S P G R}

represents the signal amplitude at echo time TE = 0 and incorporates proton density and machine factors, and α k is the k th excitation FA out of a total of K FAs.…”

Section: Theorymentioning

confidence: 99%

Improved determination of the myelin water fraction in human brain using magnetic resonance imaging through Bayesian analysis of mcDESPOT

Bouhrara

Spencer

2016

NeuroImage

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Myelin water fraction (MWF) mapping with magnetic resonance imaging has led to the ability to directly observe myelination and demyelination in both the developing brain and in disease. Multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) has been proposed as a rapid approach for multicomponent relaxometry and has been applied to map MWF in human brain. However, even for the simplest two-pool signal model consisting of MWF and non-myelin-associated water, the dimensionality of the parameter space for obtaining MWF estimates remains high. This renders parameter estimation difficult, especially at low-to-moderate signal-to-noise ratios (SNR), due to the presence of local minima and the flatness of the fit residual energy surface used for parameter determination using conventional nonlinear least squares (NLLS)-based algorithms. In this study, we introduce three Bayesian approaches for analysis of the mcDESPOT signal model to determine MWF. Given the high dimensional nature of mcDESPOT signal model, and, thereby, the high dimensional marginalizations over nuisance parameters needed to derive the posterior probability distribution of MWF parameter, the introduced Bayesian analyses use different approaches to reduce the dimensionality of the parameter space. The first approach uses normalization by average signal amplitude, and assumes that noise can be accurately estimated from signal-free regions of the image. The second approach likewise uses average amplitude normalization, but incorporates a full treatment of noise as an unknown variable through marginalization. The third approach does not use amplitude normalization and incorporates marginalization over both noise and signal amplitude. Through extensive Monte Carlo numerical simulations and analysis of in-vivo human brain datasets exhibiting a range of SNR and spatial resolution, we demonstrated the markedly improved accuracy and precision in the estimation of MWF using these Bayesian methods as compared to the stochastic region contraction (SRC) implementation of NLLS.

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“…However, authors of previous multicomponent T2 mapping studies (24)(25)(26)(27)(28) have been limited by their use of CarrPurcell-Meiboom-Gill techniques with long acquisition times, which allowed for cartilage assessment on only a single section of ex vivo specimens. Multicomponent driven equilibrium single-shot observation of T1 and T2 (mcDESPOT) is a rapid method for multicomponent T2 mapping (29)(30)(31)(32)(33)(34). The use of mcDESPOT allows acquisition of three-dimensional (3D) voxel-based measurements of the fractions and T2 values of the fast-relaxing and slow-relaxing water components of the articular cartilage of the human knee joint at 3.0 T with high spatial resolution, large volume coverage, and relatively Abbreviations: AUC = area under the curve BLOKS = Boston-Leeds osteoarthritis knee scoring CI = confidence interval F F = fraction of the fast-relaxing water component FSE = fast spin echo mcDESPOT = multicomponent driven equilibrium singleshot observation of T1 and T2 T2 F = T2 of the fast-relaxing water component T2 Single = single-component T2 T2 s = T2 of the slow-relaxing water component 3D = three-dimensional…”

Section: Study Groupmentioning

confidence: 99%