title: Functional magnetic resonance imaging activation detection: fuzzy cluster analysis in wavelet and multiwavelet domains.
abstract: OBJECTIVE
  To present novel feature spaces, based on multiscale decompositions obtained by scalar wavelet and multiwavelet transforms, to remedy problems associated with high dimension of functional magnetic resonance imaging (fMRI) time series (when they are used directly in clustering algorithms) and their poor signal-to-noise ratio (SNR) that limits accurate classification of fMRI time series according to their activation contents.
  
  
  METHODS
  Using randomization, the proposed method finds wavelet/multiwavelet coefficients that represent the activation content of fMRI time series and combines them to define new feature spaces. Using simulated and experimental fMRI data sets, the proposed feature spaces are compared to the cross-correlation (CC) feature space and their performances are evaluated. In these studies, the false positive detection rate is controlled using randomization. To compare different methods, several points of the receiver operating characteristics (ROC) curves, using simulated data, are estimated and compared.
  
  
  RESULTS
  The proposed features suppress the effects of confounding signals and improve activation detection sensitivity. Experimental results show improved sensitivity and robustness of the proposed method compared to the conventional CC analysis.
  
  
  CONCLUSIONS
  More accurate and sensitive activation detection can be achieved using the proposed feature spaces compared to CC feature space. Multiwavelet features show superior detection sensitivity compared to the scalar wavelet features.
authors.affiliation: Control and Intelligent Processing Center of Excellence, Electrical and Computer Engineering Department, Faculty of Engineering, University of Tehran, Tehran, Iran.
authors.forename: Hesamoddin
authors.initials: H
authors.lastname: Jahanian
authors.forename: Hamid
authors.initials: H
authors.lastname: Soltanian-Zadeh
authors.forename: Gholam-Ali
authors.initials: GA
authors.lastname: Hossein-Zadeh
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology; D016000:Cluster Analysis; D017143:Fuzzy Logic; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011897:Random Allocation