A novel method for quantifying scanner instability in fMRI
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. Copyright © 2010 Wiley-Liss, Inc.
Greve, DN; Mueller, BA; Liu, T; Turner, JA; Voyvodic, J; Yetter, E; Diaz, M; McCarthy, G; Wallace, S; Roach, BJ; Ford, JM; Mathalon, DH; Calhoun, VD; Wible, CG; Brown, GG; Potkin, SG; Glover, G
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