fMRI at 1.5, 3 and 7 T: Characterising BOLD Signal Changes. van der Zwaag, W., Francis, S., Head, K. E., Peters, A., Gowland, P., Morris, P., & Bowtell, R. NeuroImage.
Paper doi abstract bibtex Blood oxygenation level dependent (BOLD) signal changes occurring during execution of a simple motor task were measured at field strengths of 1.5, 3 and 7 Tesla using multi-slice, single shot, gradient-echo EPI at a resolution of 1x1x3 mm3, to quantify the benefits offered by ultra-high magnetic field for functional MRI. Using four different echo times at each field strength allowed quantification of the relaxation rate, R2* and the change in relaxation rate on activation, [Delta]R2*. This work adds to previous studies of the field strength dependence of BOLD signal characteristics, through its: (i) focus on motor rather than visual cortex; (ii) use of single-shot, multi-slice, gradient-echo EPI for data acquisition; (iii) co-registration of images acquired at different field strengths to allow assessment of the BOLD signal changes in the same region at each field strength. [Delta]R2* was found to increase linearly with field strength (0.51±0.06 s-1 at 1.5T; 0.98±0.08 s-1 at 3 T; 2.55±0.22 s-1 at 7T), while the ratio of [Delta]R2*/R2, which dictates the accessible BOLD contrast was also found to increase (0.042±0.002 at 1.5T; 0.054±0.002 at 3 T; 0.084±0.003 at 7T). The number of pixels classified as active, the t-value calculated over a common region of interest and the percentage signal change in the same region were all found to peak at TE \textasciitilde T2* and increase significantly with field strength. An earlier onset of the haemodynamic response at higher field provides some evidence for a reduced venous contribution to the BOLD signal at 7 T.
@article{van_der_zwaag_fmri_nodate,
title = {{fMRI} at 1.5, 3 and 7 {T}: {Characterising} {BOLD} {Signal} {Changes}},
volume = {In Press, Accepted Manuscript},
issn = {1053-8119},
shorttitle = {{fMRI} at 1.5, 3 and 7 {T}},
url = {http://www.sciencedirect.com/science/article/B6WNP-4W91PVH-6/2/f83784ad83614535c0a3627822a39596},
doi = {10.1016/j.neuroimage.2009.05.015},
abstract = {Blood oxygenation level dependent (BOLD) signal changes occurring during execution of a simple motor task were measured at field strengths of 1.5, 3 and 7 Tesla using multi-slice, single shot, gradient-echo EPI at a resolution of 1x1x3 mm3, to quantify the benefits offered by ultra-high magnetic field for functional MRI. Using four different echo times at each field strength allowed quantification of the relaxation rate, R2* and the change in relaxation rate on activation, [Delta]R2*. This work adds to previous studies of the field strength dependence of BOLD signal characteristics, through its: (i) focus on motor rather than visual cortex; (ii) use of single-shot, multi-slice, gradient-echo EPI for data acquisition; (iii) co-registration of images acquired at different field strengths to allow assessment of the BOLD signal changes in the same region at each field strength. [Delta]R2* was found to increase linearly with field strength (0.51±0.06 s-1 at 1.5T; 0.98±0.08 s-1 at 3 T; 2.55±0.22 s-1 at 7T), while the ratio of [Delta]R2*/R2, which dictates the accessible BOLD contrast was also found to increase (0.042±0.002 at 1.5T; 0.054±0.002 at 3 T; 0.084±0.003 at 7T). The number of pixels classified as active, the t-value calculated over a common region of interest and the percentage signal change in the same region were all found to peak at TE {\textasciitilde} T2* and increase significantly with field strength. An earlier onset of the haemodynamic response at higher field provides some evidence for a reduced venous contribution to the BOLD signal at 7 T.},
urldate = {2009-05-15},
journal = {NeuroImage},
author = {van der Zwaag, Wietske and Francis, Susan and Head, Kay E. and Peters, Andrew and Gowland, Penny and Morris, Peter and Bowtell, Richard},
keywords = {BOLD},
file = {ScienceDirect Snapshot:/Users/nickb/Zotero/storage/WVDJKEQ2/science.html:text/html;vanderzwaag2009.pdf:/Users/nickb/Zotero/storage/GITESQT8/vanderzwaag2009.pdf:application/pdf}
}
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Using four different echo times at each field strength allowed quantification of the relaxation rate, R2* and the change in relaxation rate on activation, [Delta]R2*. This work adds to previous studies of the field strength dependence of BOLD signal characteristics, through its: (i) focus on motor rather than visual cortex; (ii) use of single-shot, multi-slice, gradient-echo EPI for data acquisition; (iii) co-registration of images acquired at different field strengths to allow assessment of the BOLD signal changes in the same region at each field strength. [Delta]R2* was found to increase linearly with field strength (0.51±0.06 s-1 at 1.5T; 0.98±0.08 s-1 at 3 T; 2.55±0.22 s-1 at 7T), while the ratio of [Delta]R2*/R2, which dictates the accessible BOLD contrast was also found to increase (0.042±0.002 at 1.5T; 0.054±0.002 at 3 T; 0.084±0.003 at 7T). 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