TY - JOUR
T1 - Inflow effects on functional MRI
AU - Gao, Jia Hong
AU - Liu, Ho Ling
N1 - Funding Information:
This work is partially supported by grants from the Ministry of Science and Technology of China with grant numbers of 2012CB720700 and 2011BAI12B01 ; and Department of Defense of USA with grant number of W81XWH-09-2-0102 .
PY - 2012/8/15
Y1 - 2012/8/15
N2 - Blood inflow from the upstream has contribution or contamination to the blood oxygen level-dependent (BOLD) functional signal both in its magnitude and time courses. During neuronal activations, regional blood flow velocity increases which results in increased fMRI signals near the macrovasculatures. The inflow effects are dependent on RF pulse history, slice geometry, flow velocity, blood relaxation times and imaging parameters. In general, the effect is stronger with more T1 weighting in the signal, e.g. by using a short repetition time and a large flip angle. This article reviews the basic principle of the inflow effects, its appearances in conventional GRE, fast spin-echo (FSE) and echo-planar imaging (EPI) acquisitions, methods for separating the inflow from the BOLD effect as well as the interplay between imaging parameters and other physiological factors with the inflow effects in fMRI. Based on theoretical derivation and human experiments, the inflow effects have been shown to contribute significantly in conventional GRE but negligible in FSE acquisitions. For gradient-echo EPI experiments, the blood inflow could modulate both amplitude and the temporal information of the fMRI signal, depending on the imaging parameters and settings.
AB - Blood inflow from the upstream has contribution or contamination to the blood oxygen level-dependent (BOLD) functional signal both in its magnitude and time courses. During neuronal activations, regional blood flow velocity increases which results in increased fMRI signals near the macrovasculatures. The inflow effects are dependent on RF pulse history, slice geometry, flow velocity, blood relaxation times and imaging parameters. In general, the effect is stronger with more T1 weighting in the signal, e.g. by using a short repetition time and a large flip angle. This article reviews the basic principle of the inflow effects, its appearances in conventional GRE, fast spin-echo (FSE) and echo-planar imaging (EPI) acquisitions, methods for separating the inflow from the BOLD effect as well as the interplay between imaging parameters and other physiological factors with the inflow effects in fMRI. Based on theoretical derivation and human experiments, the inflow effects have been shown to contribute significantly in conventional GRE but negligible in FSE acquisitions. For gradient-echo EPI experiments, the blood inflow could modulate both amplitude and the temporal information of the fMRI signal, depending on the imaging parameters and settings.
KW - Blood oxygen level-dependent (BOLD)
KW - Functional MRI (fMRI)
KW - Inflow effects
KW - MRI
KW - Time-of-flight (TOF)
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U2 - 10.1016/j.neuroimage.2011.09.088
DO - 10.1016/j.neuroimage.2011.09.088
M3 - Review article
C2 - 22019882
AN - SCOPUS:84863005578
SN - 1053-8119
VL - 62
SP - 1035
EP - 1039
JO - NeuroImage
JF - NeuroImage
IS - 2
ER -