Assessment of cerebrovascular reactivity with functional magnetic resonance imaging: comparison of CO2 and breath holding

Cerebral blood flow (CBF) and oxygenation changes following both a simple b reath holding test (BHT) and a CO2 challenge can be detected with functiona l magnetic resonance imaging techniques. The BHT has the advantage of not r equiring a source of CO2 and acetazolamide and therefore it can easily be p erformed during a routine MR examination. In this study we compared global hemodynamic changes induced by breath holding and CO2 inhalation with blood oxygenation level dependent (BOLD) and CBF sensitized fMRI techniques. Dur ing each vascular challenge BOLD and CBF signals were determined simultaneo usly with a combined BOLD and flow-sensitive alternating inversion recovery (FAIR) pulse sequence. There was a good correlation between the global BOL D signal intensity changes during breath holding and CO2 inhalation support ing the notion that the BHT is equivalent to CO2 inhalation in evaluating t he hemodynamic reserve capacity with BOLD fMRI. In contrast, there was no c orrelation between relative CBF changes during both vascular challenges, wh ich was probably due to the reduced temporal resolution of the combined BOL D and FAIR pulse sequence. (C) 2001 Elsevier Science Inc. All rights reserv ed.