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Removal of phase artifacts from fMRI data using a Stockwell transform filter improves brain activity detection
Author(s) -
Goodyear Bradley G.,
Zhu Hongmei,
Brown Robert A.,
Mitchell J. Ross
Publication year - 2004
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.10681
Subject(s) - artifact (error) , computer science , artificial intelligence , signal (programming language) , magnitude (astronomy) , computer vision , filter (signal processing) , phase (matter) , point (geometry) , fourier transform , pattern recognition (psychology) , mathematics , physics , geometry , quantum mechanics , astronomy , mathematical analysis , programming language
A novel and automated technique is described for removing fMRI image artifacts resulting from motion outside of the imaging field of view. The technique is based on the Stockwell transform (ST), a mathematical operation that provides the frequency content at each time point within a time‐varying signal. Using this technique, 1D Fourier transforms (FTs) are performed on raw image data to obtain phase profiles. The time series of phase magnitude for each and every point in the phase profile is then subjected to the ST to obtain a time‐frequency spectrum. The temporal location of an artifact is identified based on the magnitude of a frequency component relative to the median magnitude of that frequency's occurrence over all time points. After each artifact frequency is removed by replacing its magnitude with the median magnitude, an inverse ST is applied to regain the MR signal. Brain activity detection within fMRI datasets is improved by significantly reducing image artifacts that overlap anatomical regions of interest. The major advantage of ST‐filtering is that artifact frequencies may be removed within a narrow time‐window, while preserving the frequency information at all other time points. Magn Reson Med 51:16–21, 2004. © 2003 Wiley‐Liss, Inc.