title: Serial MR analysis of early permanent and transient ischemia in rats: diffusion tensor imaging and high b value diffusion weighted imaging.
abstract: OBJECTIVE
  To evaluate the temporal evolution and diagnostic values of the diffusion tensor imaging (DTI) and the high b value diffusion weighted imaging (DWI) in the early permanent and transient cerebral ischemia.
  
  
  METHODS
  For permanent or 30-minute transient-ischemia induced 30 rats, DTI and DWIs at both high b (b = 3000 s/mm(2)) and standard b value (b = 1000 s/mm(2)) were obtained at the following conditions: at 15, 30, 45, 60 minutes after the occlusion of what for hyperacute permanent ischemia; at 1, 3, 5, 7, 9 hours after the occlusion for acute permanent ischemia; and at 15 minutes before reperfusion, 0.5, 2.5, and 24 hours after reperfusion for transient ischemia. The diffusion parameters and their ratios were obtained and compared between different b values, and among different time points and groups, respectively.
  
  
  RESULTS
  For both b values, the apparent diffusion coefficient (ADC) ratio decreased for first three hours, and then slightly increased until 9 hours after the occlusion during a gradual continuous increase of DWI signal intensity (SI) ratio, with excellent correlation between ADC ratios and DWI SI ratios. The DWI showed a higher contrast ratio, but the ADC map showed a lower contrast ratio for permanent ischemia at high b value than at standard b value. Fractional anisotropy (FA) increased for 1 hour, then gradually decreased until 9 hours after the occlusion in permanent ischemia and showed transient normalization and secondary decay along with change in ADC in transient ischemia.
  
  
  CONCLUSIONS
  This study presents characteristic initial elevation and secondary decay of FA, higher contrast ratio of DWI, and lower contrast ratio of ADC map at high b value, in addition to the time evolutions of diffusion parameters in early permanent and transient ischemia.
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul 110-744, Korea.
authors.forename: Ji-hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Dong Gyu
authors.initials: DG
authors.lastname: Na
authors.forename: Kee-Hyun
authors.initials: KH
authors.lastname: Chang
authors.forename: In Chan
authors.initials: IC
authors.lastname: Song
authors.forename: Seung Hong
authors.initials: SH
authors.lastname: Choi
authors.forename: Kyu Ri
authors.initials: KR
authors.lastname: Son
authors.forename: Kyung Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Chul Ho
authors.initials: CH
authors.lastname: Sohn
mesh_terms: D000818:Animals; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D019786:Gadolinium DTPA; D002546:Ischemic Attack, Transient / Q000175:diagnosis*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: Apparent diffusion coefficient; Diffusion tensor imaging; Diffusion weighted imaging; Fractional anisotropy; Ischemia