title: Influence of Vascular Variant of the Posterior Cerebral Artery (PCA) on Cerebral Blood Flow, Vascular Response to CO2 and Static Functional Connectivity.
abstract: BACKGROUND
  The fetal origin of the posterior cerebral artery (fPCA) is a frequent vascular variant in 11-29% of the population. For the fPCA, blood flow in the PCA originates from the anterior instead of the posterior circulation. We tested whether this blood supply variant impacts the cerebral blood flow assessed by arterial spin labeling (ASL), cerebrovascular reserve as well as resting-state static functional connectivity (sFC) in the sense of a systematic confound.
  
  
  METHODS
  The study included 385 healthy, elderly subjects (mean age: 74.18 years [range: 68.9-90.4]; 243 female). Participants were classified into normal vascular supply (n = 296, 76.88%), right fetal origin (n = 23, 5.97%), left fetal origin (n = 16, 4.16%), bilateral fetal origin (n = 4, 1.04%), and intermediate (n = 46, 11.95%, excluded from further analysis) groups. ASL-derived relative cerebral blood flow (relCBF) maps and cerebrovascular reserve (CVR) maps derived from a CO2 challenge with blocks of 7% CO2 were compared. Additionally, sFC between 90 regions of interest (ROIs) was compared between the groups.
  
  
  RESULTS
  CVR was significantly reduced in subjects with ipsilateral fPCA, most prominently in the temporal lobe. ASL yielded a non-significant trend towards reduced relCBF in bilateral posterior watershed areas. In contrast, conventional atlas-based sFC did not differ between groups.
  
  
  CONCLUSIONS
  In conclusion, fPCA presence may bias the assessment of cerebrovascular reserve by reducing the response to CO2. In contrast, its effect on ASL-assessed baseline perfusion was marginal. Moreover, fPCA presence did not systematically impact resting-state sFC. Taken together, this data implies that perfusion variables should take into account the vascularization patterns.
authors.affiliation: Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Emmert
authors.affiliation: Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland.|Office Médico-Pédagogique, Department of Psychiatry, University of Geneva, Geneva, Switzerland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Zöller
authors.affiliation: Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland.
authors.forename: Maria Giulia
authors.initials: MG
authors.lastname: Preti
authors.affiliation: Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Medical Image Processing Laboratory, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Geneva, Switzerland.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Van De Ville
authors.affiliation: Department of Psychiatry, University of Geneva, Geneva, Switzerland.
authors.forename: Panteleimon
authors.initials: P
authors.lastname: Giannakopoulos
authors.affiliation: Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Affidea Centre de Diagnostic Radiologique de Carouge CDRC, Carouge, Switzerland.|Department of Surgical Sciences, Radiology, Uppsala University, Uppsala, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Haller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D002245:Carbon Dioxide / Q000378:metabolism*; D002339:Carotid Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D020769:Posterior Cerebral Artery / Q000502:physiology*; D013113:Spin Labels; D013702:Temporal Lobe / Q000098:blood supply*
chemical_list: D013113:Spin Labels; D002245:Carbon Dioxide