@article{Xiaoming2010,
abstract = {Accurate R2* measurements are critical for many abdominal imaging applications. Conventionally, R2* maps are derived via the monoexponential fitting of signal decay within a series of gradient-echo (GRE) images reconstructed from multichannel datasets combined using a root sum-of-squares (RSS) approach. However, the noise bias at low-SNR TEs from RSS-reconstructed data often causes the underestimation of R2* values. In phantom, ex vivo animal model and normal volunteer studies, we investigated the accuracy of low-SNR R2* measurement when combining truncation and coil combination methods. The accuracy for R2* estimations was shown to be affected by the intrinsic R2* value, SNR level and the chosen reconstruction method. The R2* estimation error was found to decrease with increasing SNR level, decreasing R2* value and the use of the optimal B1-weighted combined (OBC) image reconstruction method. Data truncation based on rigorous voxel-wise SNR estimates can reduce R2* measurement error in the setting of low SNR with fast signal decay. When optimal SNR truncation thresholds are unknown, the OBC method can provide optimal R2* measurements given the minimal truncation requirements. {\textcopyright} 2010 John Wiley & Sons, Ltd.},
author = {Yin, Xiaoming and Shah, Saurabh and Katsaggelos, Aggelos K. and Larson, Andrew C.},
doi = {10.1002/nbm.1539},
issn = {09523480},
journal = {NMR in Biomedicine},
keywords = {Multiple gradient-echo,Noise bias,Optimal B1-weighted image reconstruction,Phase array coils,R2* mapping,Root sum-of-square,Signal to noise ratios,Truncation},
month = {dec},
number = {10},
pages = {1127--1136},
pmid = {21162142},
title = {{Improved R2* measurement accuracy with absolute SNR truncation and optimal coil combination}},
url = {https://onlinelibrary.wiley.com/doi/10.1002/nbm.1539},
volume = {23},
year = {2010}
}

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In phantom, ex vivo animal model and normal volunteer studies, we investigated the accuracy of low-SNR R2* measurement when combining truncation and coil combination methods. The accuracy for R2* estimations was shown to be affected by the intrinsic R2* value, SNR level and the chosen reconstruction method. The R2* estimation error was found to decrease with increasing SNR level, decreasing R2* value and the use of the optimal B1-weighted combined (OBC) image reconstruction method. Data truncation based on rigorous voxel-wise SNR estimates can reduce R2* measurement error in the setting of low SNR with fast signal decay. 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