title: Comparison of arterial spin labeling and bolus perfusion-weighted imaging for detecting mismatch in acute stroke.
abstract: OBJECTIVE
  The perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch paradigm is widely used in stroke imaging studies. Arterial spin labeling (ASL) is an alternative perfusion method that does not require contrast. This study compares the agreement of ASL-DWI and PWI-DWI mismatch classification in patients with stroke.
  
  
  METHODS
  This was a retrospective study drawn from all 1.5-T MRI studies performed in 2010 at a single institution. Inclusion criteria were: symptom onset<5 days, DWI lesion>10 mL, and acquisition of both PWI and ASL. DWI and PWI time to maximum>6 seconds lesion volumes were determined using automated software. Patients were classified into reperfused, matched, or mismatch groups. Two radiologists classified ASL-DWI qualitatively into the same categories blinded to DWI-PWI. Agreement between both individual readers and methods was assessed.
  
  
  RESULTS
  Fifty-one studies met the inclusion criteria. Seven cases were excluded (1 due to PWI susceptibility artifact, 2 due to motion, and 4 due to severe ASL border zone sign), resulting in 44 studies for comparison. Interrater agreement for ASL-DWI mismatch status was high (κ=0.92; 95% CI, 0.80-1.00). ASL-DWI and PWI-DWI mismatch categories agreed in 25 of 44 cases (57%). In the 16 of 19 discrepant cases (84%), ASL overestimated the PWI lesion size. In 34 of 44 cases (77%), they agreed regarding the presence of mismatch versus no mismatch.
  
  
  CONCLUSIONS
  Mismatch classification based on ASL and PWI agrees frequently but not perfectly. ASL tends to overestimate the PWI time to maximum lesion volume. Improved ASL methodologies and/or higher field strength are necessary before ASL can be recommended for routine use in acute stroke.
authors.affiliation: Department of Radiology, Stanford University Medical Center, 1201 Welch Road, Mailcode 5488, Stanford, CA 94305-5488, USA. gregz@stanford.edu
authors.forename: Greg
authors.initials: G
authors.lastname: Zaharchuk
authors.forename: Ibraheem S
authors.initials: IS
authors.lastname: El Mogy
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Fischbein
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Albers
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D013113:Spin Labels; D020521:Stroke / Q000175:diagnosis* / Q000378:metabolism*; D055815:Young Adult
chemical_list: D013113:Spin Labels