Basal cerebral blood volume during the poststimulation undershoot in BOLD MRI of the human brain.
One of the characteristics of the blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) response to functional challenges of the brain is the poststimulation undershoot, which has been suggested to originate from a delayed recovery of either cerebral blood volume (CBV) or cerebral metabolic rate of oxygen to baseline. Using bolus-tracking MRI in humans, we recently showed that relative CBV rapidly normalizes after the end of stimulation. As this observation contradicts at least part of the blood-pool contrast agent studies performed in animals, we reinvestigated the CBV contribution by dynamic T1-weighted three-dimensional MRI (8 seconds temporal resolution) and Vasovist at 3 T (12 subjects). Initially, we determined the time constants of individual BOLD responses. After injection of Vasovist, CBV-related T1-weighted signal changes revealed a signal increase during visual stimulation (1.7% ± 0.4%), but no change relative to baseline in the poststimulation phase (0.2% ± 0.3%). This finding renders the specific nature of the contrast agent unlikely to be responsible for the discrepancy between human and animal studies. With the assumption of normalized cerebral blood flow after stimulus cessation, a normalized CBV lends support to the idea that the BOLD MRI undershoot reflects a prolonged elevation of oxidative metabolism.
Dechent
Peter
P
MR-Research in Neurology and Psychiatry, Georg-August-Universität, Göttingen, Germany. pdechen@gwdg.de
Schütze
Gunther
G
Helms
Gunther
G
Merboldt
Klaus Dietmar
KD
Frahm
Jens
J
D000328:Adult; D001810:Blood Volume / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D003627:Data Interpretation, Statistical; D005260:Female; D005682:Gadolinium; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009942:Organometallic Compounds; D010100:Oxygen / Q000097:blood*; D010775:Photic Stimulation; D055815:Young Adult
D003287:Contrast Media; D009942:Organometallic Compounds; D005682:Gadolinium; D010100:Oxygen; C109932:gadofosveset trisodium