Venous blood effects in spin-echo fMRI of human brain

Joni M.E. Oja, Joe Gillen, Risto A. Kauppinen, Michael Kraut, Peter C.M. Van Zijl

Research output: Contribution to journalArticle

Abstract

The spin-echo response to visual activation was studied as a function of spatial resolution at a field of 1.5 T. The results showed that the increase in absolute T2 upon activation was as large as 22.8 ± 3.1% (P < 0.05) at the highest resolution (5.3 mm3), while it was as small as 3.5 ± 0.2% (P < 0.05) at the lowest resolution (42.2 mm3). In addition, upon increasing resolution, the spin-echo signal decay as a function of echo time changed from monoexponential to nonexponential. These data indicate that, when using the standard resolution for fMRI studies at 1.5 T, the effects of spin-echo changes in the draining veins are of major contribution to the total blood oxygenation level-dependent (BOLD) signal changes measured in voxels encompassing the activated brain areas. The data can be quantitatively accounted for using a model based on the intravascular origin of the spin- echo effect including both macrovascular and microvascular effects. Existing theories for the spin-echo BOLD effect based on diffusion through field gradients predict negligible spin-echo effects inside the large vessels and are therefore incompatible with the data.

Original languageEnglish (US)
Pages (from-to)617-626
Number of pages10
JournalMagnetic resonance in medicine
Volume42
Issue number4
DOIs
StatePublished - Oct 16 1999

Keywords

  • Blood oxygenation level-dependent
  • Brain
  • Functional MRI
  • Spin echo
  • Venous blood
  • Visual cortex

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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