Document Detail

On the origin of respiratory artifacts in BOLD-EPI of the human brain.
MedLine Citation:
PMID:  12467863     Owner:  NLM     Status:  MEDLINE    
BOLD-based functional MRI (fMRI) can be used to explicitly measure hemodynamic aspects and functions of human neuro-physiology. As fMRI measures changes in regional cerebral blood flow and volume as well as blood oxygenation, rather than neuronal brain activity directly, other processes that may change the above parameters have to be examined closely to assess sensitivity and specificity of fMRI results. Physiological processes that can cause artifacts include cardiac action, breathing and vasomotion. Although there has been substantial research on physiological artifacts and appropriate compensation methods, controversy still remains on the mechanisms that cause the fMRI signal fluctuations. Respiratory-correlated fluctuations may either be induced by changes of the magnetic field homogeneity due to moving organs, intra-thoracic pressure differences, respiration-dependent vasodilation or oxygenation differences. The aim of this study was to characterize the impact of different breathing patterns by varying respiration frequency and/or tidal volume on EPI time courses of the resting human brain. The amount of respiration-related oscillations during three respiration patterns was quantified, and statistically significant differences were obtained in white matter only: p < 0.03 between 6 vs. 12 ml/kg body weight end tidal volume at a respiration frequency of 15/min, p < 0.03 between 12 vs. 6 ml/kg body weight and 15 vs. 10 respiration cycles/min. There was no significant difference between 15 vs. 10 respiration cycles/min at an end tidal volume of 6 ml/kg body weight (p = 0.917). In addition, the respiration-affected brain regions were very similar with EPI readout in the a-p and l-r direction. Based on our results and published literature we hypothesize that venous oxygenation oscillations due to changing intra-thoracic pressure represent a major factor for respiration-related signal fluctuations and increase significantly with increasing end tidal volume in white matter only.
Christian Windischberger; Herbert Langenberger; Thomas Sycha; Edda M Tschernko; Gabriele Fuchsjäger-Mayerl; Leopold Schmetterer; Ewald Moser
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Magnetic resonance imaging     Volume:  20     ISSN:  0730-725X     ISO Abbreviation:  Magn Reson Imaging     Publication Date:  2002 Oct 
Date Detail:
Created Date:  2002-12-06     Completed Date:  2003-03-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8214883     Medline TA:  Magn Reson Imaging     Country:  United States    
Other Details:
Languages:  eng     Pagination:  575-82     Citation Subset:  IM    
Institute for Medical Physics, University of Vienna, Austria.
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MeSH Terms
Brain / blood supply*,  physiology*
Cerebral Arteries / physiology
Cerebral Veins / physiology
Cerebrovascular Circulation / physiology
Magnetic Resonance Imaging*
Pilot Projects
Sensitivity and Specificity
Tidal Volume / physiology*

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