Test-retest reliability of cerebral blood flow and blood oxygenation level-dependent responses to hypercapnia and hyperoxia using dual-echo pseudo-continuous arterial spin labeling and step changes in the fractional composition of inspired gases.
OBJECTIVE
To assess the reproducibility of blood oxygenation level-dependent / cerebral blood flow (BOLD/CBF) responses to hypercapnia/hyperoxia using dual-echo pseudo-continuous arterial spin labeling (pCASL) and step changes in inspired doses.


METHODS
Eight subjects were scanned twice, within 24 hours, using the same respiratory manipulation and imaging protocol. Imaging comprised a 5-minute anatomical acquisition, allowing segmentation of the gray matter (GM) tissue for further analysis, and an 18-minute pCASL functional scan. Hypercapnia/hyperoxia were induced by increasing the fraction of inspired CO2 to 5% and inspired O2 to 60%, alternately. Reproducibility of BOLD and CBF pCASL measures was assessed by computing the inter-session coefficient of variation (CV) of the respective signals in GM.


RESULTS
BOLD and CBF measures in GM were robust and consistent, yielding CV values below 10% for BOLD hypercapnic/hyperoxic responses (which averaged 1.9 ± 0.1% and 1.14 ± 0.02%) and below 20% for the CBF hypercapnic response (which averaged 35 ± 2 mL/min/100g). The CV for resting CBF was 3.5%.


CONCLUSIONS
It is possible to attain reproducible measures of the simultaneous BOLD and CBF responses to blood gases, within a reasonable scan time and with whole brain coverage, using a simple respiratory manipulation and dual-echo pCASL.
Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.|Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada.|Hospital Israelita Albert Einstein Imagem Av. Albert Einstein, 627, São Paulo, SP, Brazil.
Felipe B
FB
Tancredi
Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.|Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada.
Isabelle
I
Lajoie
Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.|Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada.
Richard D
RD
Hoge
D000328:Adult; D001783:Blood Flow Velocity; D001921:Brain / Q000503:physiopathology; D002536:Cerebral Arteries / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D018496:Hyperoxia / Q000503:physiopathology*; D001239:Inhalation; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels; D055815:Young Adult
D013113:Spin Labels; D010100:Oxygen
ASL; BOLD; cerebrovascular reactivity; fMRI; hypercapnia; hyperoxia