IMPACT: Image-based physiological artifacts estimation and correction technique for functional MRI

Functional MRI (fMRI) signal variation induced by respiratory and cardiac m otion affects the activation signal and limits the accuracy of analysis. Cu rrent physiological motion correction methods require either synchronizatio n with external monitoring of respiration and heartbeat, specialized pulse sequence design, or k-space data. The IMage-based Physiological Artifacts e stimation and Correction Technique (IMPACT), which is free from these const raints, is described. When images are acquired fast enough to sample physio logical motion without aliasing, respiratory and cardiac signals can be dir ectly estimated from magnitude images. Physiological artifacts are removed by reordering images according to the estimated respiratory and cardiac pha ses and then subtracting the Fourier-fitted variation from magnitude images . Compared with the k-space-based method, this method can efficiently and e ffectively reduce the overall signal fluctuation in the brain and increase the activated area. With this new technique, physiological artifacts can be reduced using traditional fMRI pulse sequences, and existing data can be c orrected and reanalyzed without additional experiments. (C) 2001 Wiley-Liss , Inc.