title: Functional evaluation of transplanted kidneys with diffusion-weighted and BOLD MR imaging: initial experience.
abstract: OBJECTIVE
  To prospectively evaluate feasibility and reproducibility of diffusion-weighted (DW) and blood oxygenation level-dependent (BOLD) magnetic resonance (MR) imaging in patients with renal allografts, as compared with these features in healthy volunteers with native kidneys.
  
  
  METHODS
  The local ethics committee approved the study protocol; patients provided written informed consent. Fifteen patients with a renal allograft and in stable condition (nine men, six women; age range, 20-67 years) and 15 age- and sex-matched healthy volunteers underwent DW and BOLD MR imaging. Seven patients with renal allografts were examined twice to assess reproducibility of results. DW MR imaging yielded a total apparent diffusion coefficient including diffusion and microperfusion (ADC(tot)), as well as an ADC reflecting predominantly pure diffusion (ADC(D)) and the perfusion fraction. R2* of BOLD MR imaging enabled the estimation of renal oxygenation. Statistical analysis was performed, and analysis of variance was used for repeated measurements. Coefficients of variation between and within subjects were calculated to assess reproducibility.
  
  
  RESULTS
  In patients, ADC(tot), ADC(D), and perfusion fraction were similar in the cortex and medulla. In volunteers, values in the medulla were similar to those in the cortex and medulla of patients; however, values in the cortex were higher than those in the medulla (P < .05). Medullary R2* was higher than cortical R2* in patients (12.9 sec(-1) +/- 2.1 [standard deviation] vs 11.0 sec(-1) +/- 0.6, P < .007) and volunteers (15.3 sec(-1) +/- 1.1 vs 11.5 sec(-1) +/- 0.5, P < .0001). However, medullary R2* was lower in patients than in volunteers (P < .004). Increased medullary R2* was paralleled by decreased diffusion in patients with allografts. A low coefficient of variation in the cortex and medulla within subjects was obtained for ADC(tot), ADC(D), and R2* (<5.2%), while coefficient of variation within subjects was higher for perfusion fraction (medulla, 15.1%; cortex, 8.6%). Diffusion and perfusion indexes correlated significantly with serum creatinine concentrations.
  
  
  CONCLUSIONS
  DW and BOLD MR imaging are feasible and reproducible in patients with renal allografts.
authors.affiliation: Department of Radiology, University Hospital of Bern, Switzerland. Harriet.Thoeny@inssel.ch
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Thoeny
authors.forename: Dominik
authors.initials: D
authors.lastname: Zumstein
authors.forename: Sonja
authors.initials: S
authors.lastname: Simon-Zoula
authors.forename: Ute
authors.initials: U
authors.lastname: Eisenberger
authors.forename: Frederik
authors.initials: F
authors.lastname: De Keyzer
authors.forename: Lucie
authors.initials: L
authors.lastname: Hofmann
authors.forename: Peter
authors.initials: P
authors.lastname: Vock
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Frey
authors.forename: Peter
authors.initials: P
authors.lastname: Vermathen
mesh_terms: D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007668:Kidney / Q000033:anatomy & histology*; D007674:Kidney Diseases / Q000175:diagnosis* / Q000503:physiopathology; D016030:Kidney Transplantation; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D014184:Transplantation, Homologous