title: Characterization and evolution of diffusion MR imaging abnormalities in stroke patients undergoing intra-arterial thrombolysis.
abstract: OBJECTIVE
  Lesions revealed by pretreatment diffusion-weighted imaging (DWI) may not progress to infarction, and apparent diffusion coefficient (ADC) or DWI thresholds for tissue viability may exist. We evaluated the evolution of abnormal DWI findings in patients with acute stroke who underwent thrombolysis.
  
  
  METHODS
  Sixteen patients with acute occlusion of the anterior circulation underwent DWI followed by intra-arterial thrombolysis; follow-up CT or MR imaging was performed after reperfusion therapy. Lesion volumes were measured on all images. In three patients with abnormal DWI findings that appeared normal at follow-up, ADC values, ADC ratios, and DWI ratios were obtained on a section-by-section basis in the DWI-hyperintense regions that were either abnormal or normal at follow-up.
  
  
  RESULTS
  In three patients, part of the DWI-hyperintense tissue appeared normal and part appeared abnormal at follow-up imaging. In one of these patients, the lesion decreased by -35.6%. In the other two, lesion growth appeared in regions that appeared normal at initial DWI: in one, the overall change in size was -2.4%, and in the other, the lesion increased by 89.8%. Respective mean changes at follow-up in normal-appearing and abnormal-appearing regions were: ADC, 731.7 x 10(-6) mm(2)/s and 650.4 x 10(-6) mm (2)/s; ADC ratio, 0.92 and 0.78; and DWI ratio, 1.16 and 1.32 (P <.001 for all measures).
  
  
  CONCLUSIONS
  In patients with acute stroke who undergo intra-arterial thrombolysis, most abnormal, pretreatment DWI findings indicate eventual infarction. In 19% of the patients described herein, DWI-hyperintense regions appeared normal at follow-up. ADC values, ADC ratios, and DWI ratios may be useful in identifying the portion of abnormal tissue that is potentially salvageable after reperfusion therapy.
authors.affiliation: Department of Radiology, Division of Neuroradiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Pamela W
authors.initials: PW
authors.lastname: Schaefer
authors.forename: Alvand
authors.initials: A
authors.lastname: Hassankhani
authors.forename: Christopher
authors.initials: C
authors.lastname: Putman
authors.forename: A Gregory
authors.initials: AG
authors.lastname: Sorensen
authors.forename: Lee
authors.initials: L
authors.lastname: Schwamm
authors.forename: Walter
authors.initials: W
authors.lastname: Koroshetz
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: Gonzalez
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007269:Injections, Intra-Arterial; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000188:drug therapy*; D015912:Thrombolytic Therapy; D014057:Tomography, X-Ray Computed