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Blood oxygenation level‐dependent (BOLD) total and extravascular signal changes and Δ R 2 * in human visual cortex at 1.5, 3.0 and 7.0 T
Author(s) -
Donahue Manus J.,
Hoogduin Hans,
van Zijl Peter C. M.,
Jezzard Peter,
Luijten Peter R.,
Hendrikse Jeroen
Publication year - 2011
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.1552
Subject(s) - visual cortex , nuclear magnetic resonance , physics , oxygenation , chemistry , cortex (anatomy) , blood oxygenation , blood oxygen level dependent , nuclear medicine , functional magnetic resonance imaging , neuroscience , medicine , psychology
The characterisation of the extravascular (EV) contribution to the blood oxygenation level‐dependent (BOLD) effect is important for understanding the spatial specificity of BOLD contrast and for modelling approaches that aim to extract quantitative metabolic parameters from the BOLD signal. Using bipolar crusher gradients, total ( b = 0 s/mm 2 ) and predominantly EV ( b = 100 s/mm 2 ) gradient echo BOLD Δ R 2 * and signal changes (ΔS/ S ) in response to visual stimulation (flashing checkerboard; f = 8 Hz) were investigated sequentially (within < 3 h) at 1.5, 3.0 and 7.0 T in the same subgroup of healthy volunteers ( n = 7) and at identical spatial resolutions (3.5 × 3.5 × 3.5 mm 3 ). Total Δ R 2 * ( z ‐score analysis) values were −0.61 ± 0.10 s −1 (1.5 T), −0.74 ± 0.05 s −1 (3.0 T) and −1.37 ± 0.12 s −1 (7.0 T), whereas EV Δ R 2 * values were −0.28 ± 0.07 s −1 (1.5 T), −0.52 ± 0.07 s −1 (3.0 T) and −1.25 ± 0.11 s −1 (7.0 T). Although EV Δ R 2 * increased linearly with field, as expected, it was found that EV ΔS/ S increased less than linearly with field in a manner that varied with TE choice. Furthermore, unlike Δ R 2 *, total and EV ΔS/ S did not converge at 7.0 T. These trends were similar whether a z ‐score analysis or occipital lobe‐based region‐of‐interest approach was used for voxel selection. These findings suggest that calibrated BOLD approaches may benefit from an EV Δ R 2 * measurement as opposed to a ΔS/ S measurement at a single TE. Copyright © 2010 John Wiley & Sons, Ltd.