High resolution SE-fMRI in humans at 3 and 7 T using a motor task
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The sensitivity of spin echo (SE) experiments to blood oxygenation level dependent (BOLD) contrast was explored in a study of the same six subjects carried out at 3 and 7 T.
Materials and methods
Multi-slice, single shot, spin echo, echo planar images with a voxel size of 1 × 1 × 3 mm3 were acquired at three different echo times, during execution of a simple motor task.
Significant activation was observed at all echo times at both field strengths. Analysis of the fractional signal change as a function of echo time indicated that the change in relaxation rate, ΔR 2, at 7 T was 0.51 ± 0.14 s −, which was 1.3 times larger than the value found at 3 T. Measurements of the percentage signal change on activation and temporal signal to noise ratio showed that there was an increase in the BOLD contrast to noise ratio (CNR) at 7 versus 3 T by a factor of 1.9. There was no overlap of areas of significant activation in the SE data acquired at either field strength with the site of large veins.
SE-BOLD CNR in motor cortex was found to increase significantly at 7 T compared with 3 T.
KeywordsBOLD High resolution High field fMRI Spin echo SE
Blood oxygenation level dependent
Regional blood volume
Cerebral blood flow
Cerebral metabolic consumption rate
Echo planar imaging
Functional magnetic resonance imaging
Field of view
Region of interest
Outer volume suppression
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