title: Components of acquisition-to-acquisition variance in continuous arterial spin labelling (CASL) imaging.
abstract: BACKGROUND
  Images of perfusion estimates obtained with the continuous arterial spin labelling technique are characterized by variation between single acquisitions. Little is known about the spatial determinants of this variation during the acquisition process and their impact on voxel-by-voxel estimates of effects.
  
  
  RESULTS
  We show here that the spatial patterns of covariance between voxels arising during the acquisition of these images uncover distinct mechanisms through which this variance arises: through variation in global perfusion levels; through the action of large vessels and other, less well characterized, large anatomical structures; and through the effect of noisy areas such as the edges of the brain.
  
  
  CONCLUSIONS
  Knowledge of these covariance patterns is important to experimenters for a correct interpretation of findings, especially for studies where relatively few acquisitions are made.
authors.affiliation: Department of Psychiatry and Psychotherapy III, University of Ulm, Leimgrubenweg 12, Ulm, Germany. roberto.viviani@uni-ulm.de
authors.forename: Roberto
authors.initials: R
authors.lastname: Viviani
authors.forename: Petra
authors.initials: P
authors.lastname: Beschoner
authors.forename: Hanna
authors.initials: H
authors.lastname: Lo
authors.forename: Nadine
authors.initials: N
authors.lastname: Osterfeld
authors.forename: Jan
authors.initials: J
authors.lastname: Thöne
authors.forename: Eun-Jin
authors.initials: EJ
authors.lastname: Sim
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis; D012815:Signal Processing, Computer-Assisted; D013113:Spin Labels; D055815:Young Adult
chemical_list: D013113:Spin Labels