Blood oxygenation level-dependent (BOLD) total and extravascular signal changes and ΔR2* in human visual cortex at 1.5, 3.0 and 7.0 T

Manus J. Donahue, Hans Hoogduin, Peter C.M. Van Zijl, Peter Jezzard, Peter R. Luijten, Jeroen Hendrikse

Research output: Contribution to journalArticle

Abstract

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=0s/mm2) and predominantly EV (b=100s/mm2) gradient echo BOLD ΔR2* and signal changes (ΔS/S) in response to visual stimulation (flashing checkerboard; f=8Hz) were investigated sequentially (within<3h) at 1.5, 3.0 and 7.0 T in the same subgroup of healthy volunteers (n=7) and at identical spatial resolutions (3.5×3.5×3.5mm3). Total ΔR2* (z-score analysis) values were -0.61±0.10s-1 (1.5 T), -0.74±0.05s-1 (3.0 T) and -1.37±0.12s-1 (7.0 T), whereas EV ΔR2* values were -0.28±0.07s-1 (1.5 T), -0.52±0.07s-1 (3.0 T) and -1.25±0.11s-1 (7.0 T). Although EV ΔR2* 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 ΔR2*, 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 ΔR2* measurement as opposed to a ΔS/S measurement at a single TE. Total and extravascular (EV) blood oxygenation level-dependent (BOLD) ΔR2* and signal changes were investigated sequentially at 1.5, 3.0 and 7.0 T. Total ΔR2* values were -0.61±0.10s-1(1.5 T), -0.74± 0.05s-1 (3.0 T) and -1.37±0.12s-1 (7.0 T), whereas EV ΔR2* values were -0.28± 0.07s-1(1.5 T), -0.52±0.07s-1(3.0 T) and -1.25±0.11s-1 (7.0 T). Although EV ΔR2* increased linearly with field, EV signal changes increased less than linearly with field; these findings suggest that calibrated BOLD approaches may benefit from an EV ΔR2* measurement as opposed to a signal change measurement at a single TE.

Original languageEnglish (US)
Pages (from-to)25-34
Number of pages10
JournalNMR in biomedicine
Volume24
Issue number1
DOIs
StatePublished - Jan 1 2011

Keywords

  • 7 T
  • Blood oxygenation level dependent
  • Extravascular
  • Functional MRI
  • Intravascular
  • R*

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy

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