title: Time delay processing of hypercapnic fMRI allows quantitative parameterization of cerebrovascular reactivity and blood flow delays.
abstract: Blood oxygenation level-dependent fMRI contrast depends on the volume and oxygenation of blood flowing through the circulatory system. The effects on image intensity depend temporally on the arrival of blood within a voxel, and signal can be monitored during the time course of such blood flow. It has been previously shown that the passage of global endogenous variations in blood volume and oxygenation can be tracked as blood passes through the brain by determining the strength and peak time lag of their cross-correlation with blood oxygenation level-dependent data. By manipulating blood composition using transient hypercarbia and hyperoxia, we can induce much larger oxygenation and volume changes in the blood oxygenation level-dependent signal than result from natural endogenous fluctuations. This technique was used to examine cerebrovascular parameters in healthy subjects (n = 8) and subjects with intracranial stenosis (n = 22), with a subgroup of intracranial stenosis subjects scanned before and after surgical revascularization (n = 6). The halfwidth of cross-correlation lag times in the brain was larger in IC stenosis subjects (21.21 ± 14.22 s) than in healthy control subjects (8.03 ± 3.67), p < 0.001, and was subsequently reduced in regions that co-localized with surgical revascularization. These data show that blood circulatory timing can be measured robustly and longitudinally throughout the brain using simple respiratory challenges.
authors.affiliation: Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA Department of Neurology, Vanderbilt Medical Center, Nashville, TN, USA Department of Psychiatry, Vanderbilt Medical Center, Nashville, TN, USA Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.
authors.forename: Manus J
authors.initials: MJ
authors.lastname: Donahue
authors.affiliation: Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Strother
authors.affiliation: Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
authors.forename: Kimberly P
authors.initials: KP
authors.lastname: Lindsey
authors.affiliation: Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Bioengineering, Tufts University, Medford, MA, USA.
authors.forename: Lia M
authors.initials: LM
authors.lastname: Hocke
authors.affiliation: Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Tong
authors.affiliation: Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA bbfrederick@mclean.harvard.edu.
authors.forename: Blaise deB
authors.initials: BD
authors.lastname: Frederick
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D003251:Constriction, Pathologic; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: Atherosclerosis; cerebral blood flow; cerebrovascular disease; fMRI; moyamoya; surgery/endarterectomy