title: Comparison of arterial transit times estimated using arterial spin labeling.
abstract: OBJECTIVE
  To compare arterial transit time estimates from two efficient transit time mapping techniques using arterial spin labeling (ASL)-flow encoded arterial spin tagging (FEAST) and Look-Locker ASL (LL-ASL). The effects of bipolar gradients and label location were investigated.
  
  
  METHODS
  Six healthy subjects were scanned with pseudo-continuous ASL (pCASL) FEAST and pulsed (PASL) and pCASL variants of LL-ASL at different labeling locations with and without bipolar gradients. Application of transit time mapping was demonstrated in a clinical case.
  
  
  RESULTS
  Mean (±SD) macrovascular transit times were 363 ± 39, 676 ± 73 and 908 ± 170 ms for LL-PASL, LL-pCASL with labeling offsets of 60 and 90 mm respectively, showing linear dependence on labeling locations. Mean microvascular transit time for LL-pCASL was 1,463±135 ms, in good agreement with the FEAST estimate of 1,444 ± 128 ms. Data acquired from a patient with stroke demonstrate how transit time and CBF maps provide complementary information for clinical diagnosis.
  
  
  CONCLUSIONS
  Both FEAST and LL-ASL provide transit time information in clinically acceptable scan times. Bipolar gradients can be used to tailor transit time estimates for different experimental and clinical situations.
authors.affiliation: Center for Advanced MRI, Department of Radiology, Northwestern University, 737 N Michigan Ave. 16th Flr., Chicago, IL 60611, USA. yfchen@northwestern.edu
authors.forename: Yufen
authors.initials: Y
authors.lastname: Chen
authors.forename: Danny J J
authors.initials: DJ
authors.lastname: Wang
authors.forename: John A
authors.initials: JA
authors.lastname: Detre
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008833:Microcirculation / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D059629:Signal-To-Noise Ratio; D013113:Spin Labels
chemical_list: D013113:Spin Labels