title: In vivo quantification of hyperoxic arterial blood water T1.
abstract: Normocapnic hyperoxic and hypercapnic hyperoxic gas challenges are increasingly being used in cerebrovascular reactivity (CVR) and calibrated functional MRI experiments. The longitudinal arterial blood water relaxation time (T1a) change with hyperoxia will influence signal quantification through mechanisms relating to elevated partial pressure of plasma-dissolved O2 (pO2) and increased oxygen bound to hemoglobin in arteries (Ya) and veins (Yv). The dependence of T1a on Ya and Yv has been elegantly characterized ex vivo; however, the combined influence of pO2, Ya and Yv on T1a in vivo under normal ventilation has not been reported. Here, T1a is calculated during hyperoxia in vivo by a heuristic approach that evaluates T1 -dependent arterial spin labeling (ASL) signal changes to varying gas stimuli. Healthy volunteers (n = 14; age, 31.5 ± 7.2 years) were scanned using pseudo-continuous ASL in combination with room air (RA; 21% O2/79% N2), hypercapnic normoxic (HN; 5% CO2/21% O2/74% N2) and hypercapnic hyperoxic (HH; 5% CO2/95% O2) gas administration. HH T1a was calculated by requiring that the HN and HH cerebral blood flow (CBF) change be identical. The HH protocol was then repeated in patients (n = 10; age, 61.4 ± 13.3 years) with intracranial stenosis to assess whether an HH T1a decrease prohibited ASL from being performed in subjects with known delayed blood arrival times. Arterial blood T1a decreased from 1.65 s at baseline to 1.49 ± 0.07 s during HH. In patients, CBF values in the affected flow territory for the HH condition were increased relative to baseline CBF values and were within the physiological range (RA CBF = 36.6 ± 8.2 mL/100 g/min; HH CBF = 45.2 ± 13.9 mL/100 g/min). It can be concluded that hyperoxic (95% O2) 3-T arterial blood T1aHH = 1.49 ± 0.07 s relative to a normoxic T1a of 1.65 s.
authors.affiliation: Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Jeroen C W
authors.identifier: http://orcid.org/0000-0001-5079-2868
authors.initials: JC
authors.lastname: Siero
authors.affiliation: Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA.|Neurological Surgery, Vanderbilt Medical Center, Nashville, TN, USA.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Strother
authors.affiliation: Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA.
authors.forename: Carlos C
authors.initials: CC
authors.lastname: Faraco
authors.affiliation: Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Hans
authors.initials: H
authors.lastname: Hoogduin
authors.affiliation: Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Hendrikse
authors.affiliation: Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA.|Neurology, Vanderbilt Medical Center, Nashville, TN, USA.|Psychiatry, Vanderbilt Medical Center, Nashville, TN, USA.|Vanderbilt Brain Institute, Vanderbilt Medical Center, Nashville, TN, USA.
authors.forename: Manus J
authors.initials: MJ
authors.lastname: Donahue
mesh_terms: D000328:Adult; D000465:Algorithms; D001834:Body Water / Q000378:metabolism*; D002536:Cerebral Arteries / Q000378:metabolism*; D002561:Cerebrovascular Disorders / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels
chemical_list: D013113:Spin Labels; D010100:Oxygen
keywords: T1; arterial spin labeling; blood; carbogen; cerebrovascular reactivity; hypercapnia; hyperoxia