MRI mapping of cerebrovascular reactivity using square wave changes in end-tidal PCO2

Magn Reson Med. 2001 Jun;45(6):1011-3. doi: 10.1002/mrm.1134.


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.

MeSH terms

  • Adult
  • Brain / blood supply*
  • Brain Mapping*
  • Carbon Dioxide / blood*
  • Female
  • Homeostasis / physiology
  • Humans
  • Image Enhancement*
  • Image Processing, Computer-Assisted*
  • Magnetic Resonance Imaging*
  • Male
  • Reference Values
  • Regional Blood Flow / physiology
  • Vascular Resistance / physiology*


  • Carbon Dioxide