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Smoothness of in vivo spectral baseline determined by mean‐square error
Author(s) -
Zhang Yan,
Shen Jun
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.25013
Subject(s) - smoothness , mean squared error , baseline (sea) , mathematics , nonparametric statistics , root mean square , in vivo , statistics , function (biology) , mathematical analysis , physics , biology , quantum mechanics , evolutionary biology , fishery , microbiology and biotechnology
Purpose A nonparametric smooth line is usually added to the spectral model to account for background signals in vivo magnetic resonance spectroscopy (MRS). The assumed smoothness of the baseline significantly influences quantitative spectral fitting. In this paper, a method is proposed to minimize baseline influences on the estimated spectral parameters. Methods The nonparametric baseline function with a given smoothness was treated as a function of spectral parameters. Its uncertainty was measured by root‐mean‐square error (RMSE). The proposed method was demonstrated with a simulated spectrum and in vivo spectra of both short echo time and averaged echo times. The estimated in vivo baselines were compared with the metabolite‐nulled spectra and the LCModel‐estimated baselines. The accuracies of estimated baseline and metabolite concentrations were further verified via cross‐validation. Results An optimal smoothness condition was found that led to the minimal baseline RMSE. In this condition, the best fit was balanced against minimal baseline influences on metabolite concentration estimates. Conclusion Baseline RMSE can be used to indicate estimated baseline uncertainties and serve as the criterion for determining the baseline smoothness of in vivo MRS. Magn Reson Med 72:913–922, 2014. © 2013 Wiley Periodicals, Inc.