Quantitative differentiation between BOLD models in fMRI.
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. Magn Reson Med 45:233-246, 2001.
Hoogenraad
F G
FG
Department of Clinical Physics and Informatics, University Hospital Vrije Universiteit, Amsterdam, The Netherlands. Frank.Hoogenraad@Philips.com
Pouwels
P J
PJ
Hofman
M B
MB
Reichenbach
J R
JR
Sprenger
M
M
Haacke
E M
EM
D001825:Body Fluid Compartments / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical; D010100:Oxygen / Q000097:blood*; D010775:Photic Stimulation
D010100:Oxygen