title: Early effects of an x-ray contrast medium on renal T(2) */T(2) MRI as compared to short-term hyperoxia, hypoxia and aortic occlusion in rats.
abstract: OBJECTIVE
  X-ray contrast media (CM) can cause acute kidney injury (AKI). Medullary hypoxia is pivotal in CM-induced AKI, as indicated by invasively and pin-point measured tissue oxygenation. MRI provides spatially resolved blood oxygenation level-dependent data using T2 * and T2 mapping. We studied CM effects on renal T2 */T2 and benchmarked them against short periods of hyperoxia, hypoxia and aortic occlusion (AO).
  
  
  METHODS
  Rats were equipped with carotid artery catheters (tip towards aorta) and supra-renal aortic occluders. T2 */T2 mapping was performed using a 9.4-T animal scanner. CM (1.5 mL iodixanol) was injected into the thoracic aorta with the animal in the scanner followed by 2 h of T2 */T2 mapping. For T2 */T2 assessment, regions of interest in the cortex (C), outer medulla (OM), inner medulla (IM) and papilla (P) were determined according to morphological features.
  
  
  RESULTS
  Hyperoxia increased T2 * in C (by 17%) and all medullary layers (25-35%). Hypoxia decreased T2 * in C (40%) and all medullary layers (55-60%). AO decreased T2 * in C (18%) and all medullary layers (30-40%). Upon injection of CM, T2 * increased transiently, then decreased, reaching values 10-20% below baseline in C and OM and 30-40% below baseline in IM and P.
  
  
  CONCLUSIONS
  T2 * mapping corroborates data previously obtained with invasive methods and demonstrates that CM injection affects renal medullary oxygenation. CM-induced T2 * decrease in OM was small vs. hypoxia and aortic occlusion. T2 * decrease obtained for hypoxia was more pronounced than for AO. This indicates that T2 * may not accurately reflect blood oxygenation under certain conditions.
authors.affiliation: Center for Cardiovascular Research, Institut für Vegetative Physiologie, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Arakelyan
authors.forename: K
authors.initials: K
authors.lastname: Cantow
authors.forename: J
authors.initials: J
authors.lastname: Hentschel
authors.forename: B
authors.initials: B
authors.lastname: Flemming
authors.forename: A
authors.initials: A
authors.lastname: Pohlmann
authors.forename: M
authors.initials: M
authors.lastname: Ladwig
authors.forename: T
authors.initials: T
authors.lastname: Niendorf
authors.forename: E
authors.initials: E
authors.lastname: Seeliger
mesh_terms: D000818:Animals; D001011:Aorta / Q000473:pathology*; D003287:Contrast Media / Q000494:pharmacology; D018496:Hyperoxia; D000860:Hypoxia; D007679:Kidney Medulla / Q000187:drug effects*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D014283:Triiodobenzoic Acids / Q000494:pharmacology*
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C044834:iodixanol