Quantitative differentiation between BOLD models in fMRI

F. G.C. Hoogenraad, P. J.W. Pouwels, M. B.M. Hofman, J. R. Reichenbach, M. Sprenger, E. M. Haacke

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Abstract

Several gradient-echo fMRI blood oxygenation level-dependent (BOLD) effects are described in the literature: extravascular spin dephasing around capillaries and veins, intravascular phase changes, and transverse relaxation changes of blood. This work considers a series of tissue compartmentalized models incorporating each of these effects, and tries to determine the model which is most consistent with the data. To isolate the different tissue contributions, a series of multi-echo inversion recovery (IR) fMRI scans were performed. Visual stimulation experiments were performed at 1.5 T, one interleaved six-echo and two IR six-echo EPI scans (the latter to suppress gray matter (GM) and cerebrospinal fluid (CSF)). The tissue and vascular composition of activated areas was analyzed using independent spin-echo IR MRI experiments and MR venography, respectively. This information was used to fit the multi-echo fMRI data to the BOLD models. The activated areas almost always included a venous vessel visible on the venogram and consisted of GM and CSF. The fMRI signal changes were best described by extravascular dephasing effects in both GM and CSF around a venous vessel, in combination with intravascular effects. The role of spin dephasing around capillaries in GM appears to be insignificant.

Original languageEnglish
Pages (from-to)233-246
Number of pages14
JournalMagnetic resonance in medicine
Volume45
Issue number2
DOIs
Publication statusPublished - 15 Feb 2001

Keywords

  • BOLD fMRI
  • Extravascular dephasing
  • In vivo modeling
  • Multi-compartment
  • fMRI model

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