title: Hypoxic-ischemic brain injury in the neonatal rat model: relationship between lesion size at early MR imaging and irreversible infarction.
abstract: OBJECTIVE
  By using a neonatal rat hypoxia-ischemia (HI) model, we studied the relationship between lesion volume-measured by diffusion-weighted imaging (DWI) and T2-weighted imaging (T2WI) at an early time point-and irreversible infarct volume. We also evaluated the optimal apparent diffusion coefficient (ADC) threshold that provides the best correlation with irreversible infarct size.
  
  
  METHODS
  Twenty-three neonatal rats underwent right common carotid artery ligation and hypoxia. MR imaging was performed 1-2 hours post-HI by using DWI and T2WI and at day 4 post-HI by using T2WI. Lesion volumes relative to whole brain (%LV) were measured on ADC maps by using different relative ADC thresholds 60%-80% of mean contralateral ADC and T2WI. Pearson correlation and multiple linear regression analysis were used to study the relationships between ln(%LV) at MR imaging and %LV at histopathology.
  
  
  RESULTS
  At 1-2 hours post-HI, all lesion volume measurements on DWI were significantly correlated with the infarct volume on histopathology, with the best correlation attained at the 80% ADC threshold (r = 0.738; P < .001). The estimated regression formula was %LV on histopathology = 20.60 + 3.33 ln(%LV on 80% ADC threshold) (adjusted R(2) = 0.523; P < .001). Lesion volume at 1-2 hours post-HI tended to underestimate the final infarct volume.
  
  
  CONCLUSIONS
  Early post-HI MR imaging by using DWI correlates moderately well with the size of irreversible infarct, especially when measured by using a relative ADC threshold of 80% mean contralateral ADC.
authors.affiliation: Department of Diagnostic Radiology University of Hong Kong, Hong Kong, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: P-T
authors.initials: PT
authors.lastname: Cheung
authors.forename: G X
authors.initials: GX
authors.lastname: Shen
authors.forename: E X
authors.initials: EX
authors.lastname: Wu
authors.forename: G
authors.initials: G
authors.lastname: Cao
authors.forename: I
authors.initials: I
authors.lastname: Bart
authors.forename: W H S
authors.initials: WH
authors.lastname: Wong
authors.forename: P-L
authors.initials: PL
authors.lastname: Khong
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000473:pathology*; D002544:Cerebral Infarction / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D020925:Hypoxia-Ischemia, Brain / Q000150:complications / Q000175:diagnosis* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley