Brainstem functional magnetic resonance imaging: Disentangling signal from physiological noise
Article first published online: 24 NOV 2008
Copyright © 2008 Wiley-Liss, Inc.
Journal of Magnetic Resonance Imaging
Volume 28, Issue 6, pages 1337–1344, December 2008
How to Cite
Harvey, A. K., Pattinson, K. T.S., Brooks, J. C.W., Mayhew, S. D., Jenkinson, M. and Wise, R. G. (2008), Brainstem functional magnetic resonance imaging: Disentangling signal from physiological noise. J. Magn. Reson. Imaging, 28: 1337–1344. doi: 10.1002/jmri.21623
- Issue published online: 24 NOV 2008
- Article first published online: 24 NOV 2008
- Manuscript Accepted: 10 SEP 2008
- Manuscript Received: 14 JAN 2008
- Association of Anaesthetists of Great Britain and Ireland
- International Anesthesia Research Society
- Engineering and Physical Sciences Research Council (UK)
- Medical Research Council (UK)
- Human Frontiers Science Program RGP 0013/2004 (EU)
- Biotechnology and Biological Sciences Research Council (UK)
- physiological noise;
To estimate the importance of respiratory and cardiac effects on signal variability found in functional magnetic resonance imaging data recorded from the brainstem.
Materials and Methods
A modified version of the retrospective image correction (RETROICOR) method (Glover et al,  Magn Reson Med 44:162–167) was implemented on resting brainstem echo-planar imaging (EPI) data in 12 subjects. Fourier series were fitted to image data based on cardiac and respiratory recordings (pulseoximetry and respiratory turbine), including multiplicative terms that accounted for interactions between cardiac and respiratory signals. F-tests were performed on residuals produced by regression analysis. Additionally, we evaluated whether modified RETROICOR improved detection of brainstem activation (in 11 subjects) during a finger opposition task.
The optimal model, containing three cardiac (C) and four respiratory (R) harmonics, and one multiplicative (X) term, “3C4R1X,” significantly reduced signal variability without overfitting to noise. The application of modified RETROICOR to activation data increased group Z-statistics and reduced putative false-positive activation.
In addition to cardiac and respiratory effects, their interaction was also a significant source of physiological noise. The modified RETROICOR model improved detection of brainstem activation and would be usefully applied to any study examining this brain region. J. Magn. Reson. Imaging 2008;28:1337–1344. © 2008 Wiley-Liss, Inc.