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Brain or veinoxygenation or flow? On signal physiology in functional MRI of human brain activation
Author(s) -
Frahm Jens,
Merboldt KlausDietmar,
Hänicke Wolfgang,
Kleinschmidt Andreas,
Boecker Henning
Publication year - 1994
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1940070108
Subject(s) - oxygenation , functional magnetic resonance spectroscopy of the brain , cerebral blood flow , human brain , blood oxygenation , functional magnetic resonance imaging , neuroscience , functional imaging , medicine , cardiology , psychology
Stimulus‐related signal changes in functional MRI of human brain activation not only reflect associated adjustments of cerebral blood flow and oxygen consumption, but strongly depend on the MRI technique chosen and the actual experimental setting. A list of relevant parameters includes static field homogeneity of the magnet, MR pulse sequence and signal type, TE , TR , flip angle, gradient strengths, gradient waveforms, receiver bandwidth and voxel size. In principle, a local signal increase during functional activation may reflect a regional change in cerebral blood flow or deoxyhemoglobin concentration or both. This ambiguity was demonstrated using long TE FLASH MRI at high spatial resolution. Subsequently, experimental strategies were evaluated that either discriminate MRI effects in large vessels from those in the cortical microvasculature or separate changes in blood flow velocity from those in blood oxygenation. Examples comprise studies of the human visual and motor cortex.