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Characterization of BOLD activation in multi‐echo fMRI data using fuzzy cluster analysis and a comparison with quantitative modeling
Author(s) -
Barth Markus,
Windischberger Christian,
Klarhöfer Markus,
Moser Ewald
Publication year - 2001
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.737
Subject(s) - functional magnetic resonance imaging , nuclear magnetic resonance , voxel , signal (programming language) , pattern recognition (psychology) , echo time , spiral (railway) , artificial intelligence , magnetic resonance imaging , physics , chemistry , computer science , mathematics , neuroscience , psychology , medicine , mathematical analysis , radiology , programming language
A combination of multiple gradient‐echo imaging and exploratory data analysis (EDA), i.e. fuzzy cluster analysis (FCA), is proposed for separation and characterization of BOLD activation in single‐shot spiral functional magnetic resonance imaging (fMRI) experiments at 3 T. Differentiation of functional activation using FCA is performed by clustering pixel signal changes (Δ S ) as a function of echo time ( TE ). Further vascular classification is supported by the localization of activation and the comparison with a single‐exponential decay model. In some subjects, an additional indication for large vessels within a voxel was found as oscillation of the fMRI signal difference vs echo time ( TE ). Such large vessels may be separated from small vessel activation and, therefore, our proposed procedure might prove useful if a more specific functional localization is desired in fMRI. In addition to the signal change Δ S , Δ T 2 */ T 2 * is significantly different between activated regions. Averaged over all eight subjects Δ T 2 * is 1.7 ± 0.2 ms in ROIs with the highest signal change characterized as containing large vessels, whereas in ROIs corresponding to microvascular environment average Δ T 2 * values are 0.8 ± 0.1 ms. Copyright © 2001 John Wiley & Sons, Ltd.