[MikeWaters]

Originally Posted by SeattleUte

I'm not pregnant.

No wonder you are so slow:

http://content.nejm.org/cgi/content/full/341/22/1688

Investigations on the effect of caffeine on cerebral venous vessel contrast by using susceptibility-weighted imaging (SWI) at 1.5, 3 and 7 T.

Sedlacik J, Helm K, Rauscher A, Stadler J, Mentzel HJ, Reichenbach JR.

Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Friedrich Schiller University, Philosophenweg 3, Jena, Germany.

Caffeine lowers the blood oxygenation level-dependent (BOLD) signal by acting as an adenosine antagonist, thus decreasing the cerebral blood flow (CBF). The aims of this study were to demonstrate the sensitivity of susceptibility-weighted imaging (SWI) to caffeine-induced changes in CBF and to investigate the time course and magnitude of signal change in caffeine-habituated and -abstinent volunteers. High-resolution susceptibility-weighted images were acquired with both groups at 1.5 T using a fully velocity compensated 3D gradient echo sequence. Following a native scan, subjects were given a tablet containing 200 mg of caffeine. Scans were repeated for about 1 h and the acquired 3D data sets were co-registered to each other. BOLD signal changes of several venous vessels were analyzed in dedicated ROIs. Maps of relative signal change clearly visualized the caffeine-induced signal response of veins. Only very weak signal changes of about -2+/-1% were found in both, grey and white matter and -1+/-2% in the ventricles. Maximum signal decrease of veins occurred 40-50 min after caffeine ingestion. The signal decrease was -16.5+/-6.5% and -22.7+/-8.3% for the caffeine users group and abstainers, respectively. The signal difference of both groups was statistically significant (Student's t-test, t=2.16, p=0.021). Data acquired at 1.5, 3 and 7 T with echo times scaled to the respective field strength display very similar temporal signal behavior.

You don't have blood flowing to your brain. Are you a lush too?