title: Physiologic noise regression, motion regression, and TOAST dynamic field correction in complex-valued fMRI time series.
abstract: As more evidence is presented suggesting that the phase, as well as the magnitude, of functional MRI (fMRI) time series may contain important information and that there are theoretical drawbacks to modeling functional response in the magnitude alone, removing noise in the phase is becoming more important. Previous studies have shown that retrospective correction of noise from physiologic sources can remove significant phase variance and that dynamic main magnetic field correction and regression of estimated motion parameters also remove significant phase fluctuations. In this work, we investigate the performance of physiologic noise regression in a framework along with correction for dynamic main field fluctuations and motion regression. Our findings suggest that including physiologic regressors provides some benefit in terms of reduction in phase noise power, but it is small compared to the benefit of dynamic field corrections and use of estimated motion parameters as nuisance regressors. Additionally, we show that the use of all three techniques reduces phase variance substantially, removes undesirable spatial phase correlations and improves detection of the functional response in magnitude and phase.
authors: Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53222, USA. ahahn@mcw.edu
authors: Andrew D
authors: AD
authors: Hahn
authors: Daniel B
authors: DB
authors: Rowe
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping; D003627:Data Interpretation, Statistical; D017352:Echo-Planar Imaging; D005385:Fingers / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016013:Likelihood Functions; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D009038:Motion; D009068:Movement / Q000502:physiology; D012044:Regression Analysis; D059629:Signal-To-Noise Ratio