@article {Robertson1555, author = {A.D. Robertson and G. Matta and V.S. Basile and S.E. Black and C.K. Macgowan and J.A. Detre and B.J. MacIntosh}, title = {Temporal and Spatial Variances in Arterial Spin-Labeling Are Inversely Related to Large-Artery Blood Velocity}, volume = {38}, number = {8}, pages = {1555--1561}, year = {2017}, doi = {10.3174/ajnr.A5257}, publisher = {American Journal of Neuroradiology}, abstract = {BACKGROUND AND PURPOSE: The relationship between extracranial large-artery characteristics and arterial spin-labeling MR imaging may influence the quality of arterial spin-labeling{\textendash}CBF images for older adults with and without vascular pathology. We hypothesized that extracranial arterial blood velocity can explain between-person differences in arterial spin-labeling data systematically across clinical populations.MATERIALS AND METHODS: We performed consecutive pseudocontinuous arterial spin-labeling and phase-contrast MR imaging on 82 individuals (20{\textendash}88 years of age, 50\% women), including healthy young adults, healthy older adults, and older adults with cerebral small vessel disease or chronic stroke infarcts. We examined associations between extracranial phase-contrast hemodynamics and intracranial arterial spin-labeling characteristics, which were defined by labeling efficiency, temporal signal-to-noise ratio, and spatial coefficient of variation.RESULTS: Large-artery blood velocity was inversely associated with labeling efficiency (P = .007), temporal SNR (P \< .001), and spatial coefficient of variation (P = .05) of arterial spin-labeling, after accounting for age, sex, and group. Correction for labeling efficiency on an individual basis led to additional group differences in GM-CBF compared to correction using a constant labeling efficiency.CONCLUSIONS: Between-subject arterial spin-labeling variance was partially explained by extracranial velocity but not cross-sectional area. Choosing arterial spin-labeling timing parameters with on-line knowledge of blood velocity may improve CBF quantification.ASLarterial spin-labelingCoVcoefficient of variationPCphase contrastWMHwhite matter hyperintensities}, issn = {0195-6108}, URL = {https://www.ajnr.org/content/38/8/1555}, eprint = {https://www.ajnr.org/content/38/8/1555.full.pdf}, journal = {American Journal of Neuroradiology} }