title: Quantitative cerebrovascular 4D flow MRI at rest and during hypercapnia challenge.
abstract: Non-invasive measurement of cerebral blood flow (CBF) in humans is fraught with technologic, anatomic, and accessibility issues, which has hindered multi-vessel hemodynamic analysis of the cranial vasculature. Recent developments in cardiovascular MRI have allowed for the measurement of cine velocity vector fields over large imaging volumes in a single acquisition with 4D flow MRI. The purpose of this study was to develop an imaging protocol to simultaneously measure pulsatile flow in the circle of Willis as well as the carotid and vertebrate arteries at rest and during increased CO2 (hypercapnia).
  
  
  METHODS
  8 healthy adults (3 women, 26±0.4years) completed this study. Heart rate (pulse oximetry), arterial oxygen saturation (pulse oximetry), blood pressure (MAP, sphygmomanometry), and end-tidal CO2 (capnograph) were measured at rest (baseline) and during hypercapnia. Hypercapnia was induced via breathing a mixed gas of 3% CO2 and 21% O2 (balance N2) in the MR magnet. CBF and vessel cross-sectional area were quantified in 11 arteries using a 4D flow MRI scan, lasting 5-6min with a radially undersampled acquisition and an isotropic spatial resolution of 0.7mm.
  
  
  RESULTS
  Baseline total CBF was 665±54ml • min(-1). Hypercapnia increased total CBF 9±3% to 721±61ml • min(-1). Hypercapnic increases in CBF ranged from 7 to 36% by artery, with the largest increases in the left anterior cerebral artery. Increases in artery cross-sectional area were observed in basilar and vertebral arteries.
  
  
  CONCLUSIONS
  4D flow MRI methods are sensitive enough to detect non-uniform changes in CBF and cross-sectional area to a mild yet clinically relevant CO2 stimulus. 4D flow MRI is a non-invasive reliable tool providing high spatio-temporal resolution in clinically feasible scan times without contrast agent. This approach can be used to interrogate regional cerebrovascular control in health and disease.
authors.affiliation: Department of Kinesiology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: kellawan@wisc.edu.
authors.forename: J
authors.initials: J
authors.lastname: Mikhail Kellawan
authors.affiliation: Department of Kinesiology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: john.harrell@drake.edu.
authors.forename: John W
authors.initials: JW
authors.lastname: Harrell
authors.affiliation: Department of Medical Physics, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: schrauben@wisc.edu.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Schrauben
authors.affiliation: Department of Medical Physics, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: cahoffman@wisc.edu.
authors.forename: Carson A
authors.initials: CA
authors.lastname: Hoffman
authors.affiliation: Department of Radiology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: roldan@wisc.edu.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Roldan-Alzate
authors.affiliation: Department of Kinesiology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: wschrage@education.wisc.edu.
authors.forename: William G
authors.initials: WG
authors.lastname: Schrage
authors.affiliation: Department of Medical Physics, University of Wisconsin - Madison, Madison, WI, USA; Department of Radiology, University of Wisconsin - Madison, Madison, WI, USA. Electronic address: owieben@wisc.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Wieben
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000097:blood; D002339:Carotid Arteries / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002941:Circle of Willis / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000000981:diagnostic imaging*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D011673:Pulsatile Flow; D012146:Rest; D014711:Vertebral Artery / Q000000981:diagnostic imaging
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: 4D flow; Cerebral blood flow; Hypercapnia; Phase contrast vastly-undersampled isotropic projection reconstruction (PC VIPR)