Vascular transit times in calcarine cortex: kinetic analysis of R2* changes observed using localized 1H spectroscopy.
A kinetic analysis of water signal intensity changes measured in human visual cortex by PRESS localized 1H spectroscopy at 500 ms resolution with light-emitting diode (LED) goggle stimulation was used to determine vascular transit times for transitions between rest and activation. Monoexponential curve fitting was used to determine both R2* values for each free induction decay and the time constants for R2* changes with activation and deactivation. Measured transit time values were in general agreement with the literature, and were significantly shorter for "Off-->On" than for "On-->Off" transitions, consistent with known alterations in blood flow with activation and deactivation. The differences in transit times between "Off-->On" and "On-->Off" also varied with stimulus frequency in accordance with known physiology. This type of analysis may provide a useful means of analyzing functional activation data and for quantitatively comparing functional activation results from differing subjects and imaging sessions.
Detre
J A
JA
Department of Neurology, University of Pennsylvania Medical Center, Philadelphia 19104-4283, USA.
Wang
Z
Z
Stecker
M M
MM
Zimmerman
R A
RA
D000328:Adult; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010775:Photic Stimulation; D013997:Time Factors; D014793:Visual Cortex / Q000098:blood supply*