title: Arterial spin labeling imaging findings in transient ischemic attack patients: comparison with diffusion- and bolus perfusion-weighted imaging.
abstract: BACKGROUND
  Since transient ischemic attacks (TIAs) can predict future stroke, it is important to distinguish true vascular events from non-vascular etiologies. Arterial spin labeling (ASL) is a non-contrast magnetic resonance (MR) method that is sensitive to cerebral perfusion and arterial arrival delays. Due to its high sensitivity to minor perfusion alterations, we hypothesized that ASL abnormalities would be identified frequently in TIA patients, and could therefore help increase clinicians' confidence in the diagnosis.
  
  
  METHODS
  We acquired diffusion-weighted imaging (DWI), intracranial MR angiography (MRA), and ASL in a prospective cohort of TIA patients. A subset of these patients also received bolus contrast perfusion-weighted imaging (PWI). Two neuroradiologists evaluated the images in a blinded fashion to determine the frequency of abnormalities on each imaging sequence. Kappa (ĸ) statistics were used to assess agreement, and the χ(2) test was used to detect differences in the proportions of abnormal studies.
  
  
  RESULTS
  76 patients met the inclusion criteria, 48 (63%) of whom received PWI. ASL was abnormal in 62%, a much higher frequency compared with DWI (24%) and intracranial MRA (13%). ASL significantly increased the MR imaging yield above the combined DWI and MRA yield (62 vs. 32%, p < 0.05). Arterial transit artifact in vascular borderzones was the most common ASL abnormality (present in 51%); other abnormalities included focal high or low ASL signal (11%). PWI was abnormal in 31% of patients, and in these, ASL was abnormal in 14 out of 15 cases (93%). In hemispheric TIA patients, both PWI and ASL findings were more common in the symptomatic hemisphere. Agreement between neuroradiologists regarding abnormal studies was good for ASL and PWI [ĸ = 0.69 (95% CI 0.53-0.86) and ĸ = 0.66 (95% CI 0.43-0.89), respectively].
  
  
  CONCLUSIONS
  In TIA patients, perfusion-related alterations on ASL were more frequently detected compared with PWI or intracranial MRA and were most frequently associated with the symptomatic hemisphere. Almost all cases with a PWI lesion also had an ASL lesion. These results suggest that ASL may aid in the workup and triage of TIA patients, particularly those who cannot undergo a contrast study.
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA 94305-5488, USA. gregz@stanford.edu
authors.forename: Greg
authors.initials: G
authors.lastname: Zaharchuk
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Olivot
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Fischbein
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
authors.forename: Matus
authors.initials: M
authors.lastname: Straka
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Kleinman
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Albers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002536:Cerebral Arteries / Q000473:pathology*; D015331:Cohort Studies; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000175:diagnosis / Q000473:pathology*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013113:Spin Labels
chemical_list: D013113:Spin Labels