MRI mapping of cerebrovascular reactivity using square wave changes in end-tidal PCO2.
Cerebrovascular reactivity can be quantified by correlating blood oxygen level dependent (BOLD) signal intensity with changes in end-tidal partial pressure of carbon dioxide (PCO2). Four 3-min cycles of high and low PCO2 were induced in three subjects, each cycle containing a steady PCO2 level lasting at least 60 sec. The BOLD signal closely followed the end-tidal PCO2. The mean MRI signal intensity difference between high and low PCO2 (i.e., cerebrovascular reactivity) was 4.0 +/- 3.4% for gray matter and 0.0 +/- 2.0% for white matter. This is the first demonstration of the application of a controlled reproducible physiologic stimulus, i.e., alternating steady state levels of PCO2, to the quantification of cerebrovascular reactivity.
Vesely
A
A
Department of Anesthesia, University Health Network, University of Toronto, Toronto, Canada.
Sasano
H
H
Volgyesi
G
G
Somogyi
R
R
Tesler
J
J
Fedorko
L
L
Grynspan
J
J
Crawley
A
A
Fisher
J A
JA
Mikulis
D
D
D000328:Adult; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology*
D002245:Carbon Dioxide