Physiology and fMRI Papers

Useful Papers - Physiology and fMRI

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Glover et. al, "Image-based method for retrospective correction of physiological motion effects in fMRI: RETROICOR," Magnetic Resonance in Medicine 44, 162-167 PDF

Summary: Glover et. al describe a fast and effective retrospective algorithm to identify physiological noise in raw data and remove it; the algorithm is based on sorting images based on their point in the cardiac and/or respiratory cycles. They show it to be more effective than a popular k-space correction program.

Bottom line: Unless correlation of physiological noise with your task is a concern, you should be using this correction. At Stanford, it's built into the makevols reconstruction program.

Dagli et. al, "Localization of cardiac-induced signal change in fMRI," NeuroImage 9, 407-415 PDF

Summary: The group uses a retrospective gating method in real data to find voxels that are significantly affected by cardiac-cycle noise, to see if that noise affects parts of the brain worse than others. Unsurprisingly, the noise is found to be especially bad near major arteries, as well as near the sinus regions.

Bottom line: fMRI signal without some kind of correction will be significantly degraded in large but spatially organized regions, focused on major arteries near the medial areas of the brain, as well as near sinus regions.


Pfeuffer et. al, "Correction of physiologically induced global off-resonance effects in dynamic echo-planar and spiral functional imaging," Magnetic Resonance in Medicine 47, 344-353 PDF

Summary: Presents a correction method (innovatively named DORK, thanks to our own Gary Glover) that operates using a navigator echo to correction off-resonance artifacts largely induced by respiration (see Van de Mooretele et. al, below). Can also be used with slightly reduced effectiveness without the navigator. Best for correcting global effects - less effect on cardiac, as those artifacts are more local.

Bottom line: A fast and simple correction for global artifacts in the respiration (and other) frequency band. Probably less useful than RETROICOR, in the final analysis, but more general for global effects.

Van de Moortele et. al, "Respiration-induced B0 fluctuations and their spatial distribution in the human brain at 7 Tesla," Magnetic Resonance in Medicine 47, 888-895 PDF

Summary: A companion paper to Pfeuffer et. al above, this discusses the sources of those respiration-induced global frequency shifts. The authors examined data at 7T to mathematically model the changes in susceptibility and B0 induced by respiration, and describe a previously published mathematical model than can model those changes well.

Bottom line: Good summary description of the sources of respiration-induced artifacts and how they differ from cardiac-induced artifacts.

Peeters & Van der Linden, "A data post-processing protocol for dynamic MRI data to discriminate brain activity from global physiological effects," Magnetic Resonance Imaging 20, 503-510 PDF

Summary: Authors attempt to devise a method to help distinguish long-term gradual global changes - like those induced by a sudden temperature change and vasoconstriction, or those induced by gradual "kicking in" of a pharmacological agent - from focal changes, to enable use of those factors in studying global and local interactions. The method is simple and probably easily confounded, but low in calculation effort and straightforward.

Bottom line: Probably too crude a method to be much use for physiological correction, but how often do you see a study that does MRI on anaesthesized carp? I mean, that's awesome.