title: A novel method for quantifying scanner instability in fMRI.
abstract: A method was developed to quantify the effect of scanner instability on functional MRI data by comparing the instability noise to endogenous noise present when scanning a human. The instability noise was computed from agar phantom data collected with two flip angles, allowing for a separation of the instability from the background noise. This method was used on human data collected at four 3 T scanners, allowing the physiological noise level to be extracted from the data. In a "well-operating" scanner, the instability noise is generally less than 10% of physiological noise in white matter and only about 2% of physiological noise in cortex. This indicates that instability in a well-operating scanner adds very little noise to functional MRI results. This new method allows researchers to make informed decisions about the maximum instability level a scanner can have before it is taken off line for maintenance or rejected from a multisite consortium. This method also provides information about the background noise, which is generally larger in magnitude than the instability noise.
authors.affiliation: Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, USA. greve@nmr.mgh.harvard.edu
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Greve
authors.forename: Bryon A
authors.initials: BA
authors.lastname: Mueller
authors.forename: Thomas
authors.initials: T
authors.lastname: Liu
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Turner
authors.forename: James
authors.initials: J
authors.lastname: Voyvodic
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Yetter
authors.forename: Michele
authors.initials: M
authors.lastname: Diaz
authors.forename: Gregory
authors.initials: G
authors.lastname: McCarthy
authors.forename: Stuart
authors.initials: S
authors.lastname: Wallace
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Roach
authors.forename: Judy M
authors.initials: JM
authors.lastname: Ford
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Mathalon
authors.forename: Vince D
authors.initials: VD
authors.lastname: Calhoun
authors.forename: Cynthia G
authors.initials: CG
authors.lastname: Wible
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Brown
authors.forename: Steven G
authors.initials: SG
authors.lastname: Potkin
authors.forename: Gary
authors.initials: G
authors.lastname: Glover
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D019544:Equipment Failure Analysis / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity