title: Physiological noise reduction using volumetric functional magnetic resonance inverse imaging.
abstract: Physiological noise arising from a variety of sources can significantly degrade the detection of task-related activity in BOLD-contrast fMRI experiments. If whole head spatial coverage is desired, effective suppression of oscillatory physiological noise from cardiac and respiratory fluctuations is quite difficult without external monitoring, since traditional EPI acquisition methods cannot sample the signal rapidly enough to satisfy the Nyquist sampling theorem, leading to temporal aliasing of noise. Using a combination of high speed magnetic resonance inverse imaging (InI) and digital filtering, we demonstrate that it is possible to suppress cardiac and respiratory noise without auxiliary monitoring, while achieving whole head spatial coverage and reasonable spatial resolution. Our systematic study of the effects of different moving average (MA) digital filters demonstrates that a MA filter with a 2 s window can effectively reduce the variance in the hemodynamic baseline signal, thereby achieving 57%-58% improvements in peak z-statistic values compared to unfiltered InI or spatially smoothed EPI data (FWHM = 8.6 mm). In conclusion, the high temporal sampling rates achievable with InI permit significant reductions in physiological noise using standard temporal filtering techniques that result in significant improvements in hemodynamic response estimation.
authors.affiliation: Institute of Biomedical Engineering and Environmental Sciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Fa-Hsuan
authors.initials: FH
authors.lastname: Lin
authors.forename: Aapo
authors.initials: A
authors.lastname: Nummenmaa
authors.forename: Thomas
authors.initials: T
authors.lastname: Witzel
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Polimeni
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Zeffiro
authors.forename: Fu-Nien
authors.initials: FN
authors.lastname: Wang
authors.forename: John W
authors.initials: JW
authors.lastname: Belliveau
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D003198:Computer Simulation; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*