title: Diffusion-weighted MRI does not reflect kidney fibrosis in a rat model of fibrosis.
abstract: OBJECTIVE
  To assess the apparent diffusion coefficient (ADC) derived from diffusion-weighted (DW) magnetic resonance imaging (MRI) as a specific marker of renal fibrosis in rats with unilateral ureteral obstruction (UUO).
  
  
  METHODS
  Thirteen rats were analyzed in group 1 (n = 4), group 2 (n = 3), and group 3 (n = 6) and measured using a clinical 3.0T MR scanner. Groups 1 and 2 were used to establish the final imaging protocols for group 3. DW imaging with four b-values (0, 50, 300, 800 s/mm(2) ) was conducted before UUO, at days 3 and 5 after UUO, after release of the obstruction, and after sacrifice. Renal cortical ADCs were correlated with histological and ultrastructural analyses.
  
  
  RESULTS
  ADC values of group 3 are shown as mean ± standard deviation of [10(-3) mm(2) /s]. On day 5, in vivo cortical ADC of obstructed fibrotic kidneys was significantly reduced compared to unobstructed kidneys (1.4 ± 0.086 vs. 1.535 ± 0.087, P = 0.0018). Postmortem ADC dropped by 50% and was significantly increased in obstructed vs. unobstructed kidneys (0.711 ± 0.094 vs. 0.566 ± 0.049, P = 0.0046). Histopathology of obstructed kidneys showed tubular dilation, tubular cell atrophy, and expansion of the interstitial space. Postmortem ADC correlated tightly with tubular lumen area (r = 0.9, P < 0.001), fibronectin (r = 0.8, P = 0.003), collagen type I (r = 0.73, P = 0.007), and interstitial expansion (r = 0.69, P = 0.013).
  
  
  CONCLUSIONS
  Compared to the in vivo measurements, postmortem renal ADCs were considerably reduced and, unlike in vivo, fibrotic kidneys exhibited consistently higher ADC compared to healthy kidney parenchyma. Our data suggest that in vivo ADC is unlikely to be a direct measure of renal fibrosis.
authors: Institute of Pathology, RWTH University Aachen, Aachen, Germany.|Division of Nephrology, RWTH University Aachen, Aachen, Germany.|Electron Microscopic Facility, Medical Faculty RWTH, Aachen, Germany.|Institute of Molecular Biomedicine, Comenius University, Bratislava, Slovakia.
authors: Peter
authors: P
authors: Boor
authors: Department of Radiology, RWTH University Aachen, Aachen, Germany.|Philips Technologie GmbH Innovative Technologies, Research Laboratories, Aachen, Germany.
authors: Michael
authors: M
authors: Perkuhn
authors: Department of Radiology, RWTH University Aachen, Aachen, Germany.|Philips Technologie GmbH Innovative Technologies, Research Laboratories, Aachen, Germany.
authors: Martin
authors: M
authors: Weibrecht
authors: Division of Nephrology, RWTH University Aachen, Aachen, Germany.
authors: Stephanie
authors: S
authors: Zok
authors: Division of Nephrology, RWTH University Aachen, Aachen, Germany.
authors: Ina V
authors: IV
authors: Martin
authors: Philips Healthcare, Hamburg, Germany.
authors: Jürgen
authors: J
authors: Gieseke
authors: Department of Radiology, RWTH University Aachen, Aachen, Germany.
authors: Felix
authors: F
authors: Schoth
authors: Division of Nephrology, RWTH University Aachen, Aachen, Germany.
authors: Tammo
authors: T
authors: Ostendorf
authors: Department of Radiology, RWTH University Aachen, Aachen, Germany.
authors: Christiane
authors: C
authors: Kuhl
authors: Division of Nephrology, RWTH University Aachen, Aachen, Germany.
authors: Jürgen
authors: J
authors: Floege
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004195:Disease Models, Animal; D005355:Fibrosis; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000473:pathology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: apparent diffusion coefficient (ADC); chronic kidney disease (CKD); diffusion-weighted (DW) imaging; extracellular matrix; renal fibrosis; tubular dilation