title: MR-based semi-automated quantification of renal functional parameters with a two-compartment model--an interobserver analysis.
abstract: OBJECTIVE
  To assess the interobserver agreement in a semi-automated quantification approach of MR-renal perfusion and filtration parameters with a two-compartment model analysis.
  
  
  METHODS
  Twelve consecutive patients underwent renal perfusion measurements after intravenous injection of 7 ml Gd-BOPTA at 4 ml/s at 3.0 T. Two independent observers placed two regions of interest (ROI) manually on the axial slice, one in the abdominal aorta to determine the arterial input function (AIF), and one at the tissue-air interface for retrospective triggering. The data were fitted on a pixel-by-pixel basis to the two-compartment model, producing maps of the perfusion parameters FP (plasma flow), TP (plasma mean transit time) and of the tubular filtration parameters FT (tubular flow) and TT (tubular mean transit time). A cortical ROI was segmented by selecting those pixels with plasma volume VP>10 ml/100 ml, and the model fit was repeated on a ROI basis to produce the cortical averages.
  
  
  RESULTS
  The average values (observer 1/observer 2) were FP (226.2/187.3 ml/100 ml/min), TP (9.0/9.1s), FT (23.5/20.8 ml/100 ml/min), TT (142.1/140.0 s). The correlation coefficients between both observers were 0.90 (FP), 0.80 (TP), 0.80 (FT), 0.78 (TT). Correlations of all values were significant (p<0.05). A paired t-test yielded significant differences for FP (p=0.004).
  
  
  CONCLUSIONS
  The data demonstrate a significant systematic difference for the parameter FP, while TP seems to be most stable. Further decrease of the residual variability of all parameters seems desirable to improve the robustness of the method for clinical routine.
authors.affiliation: Institute of Clinical Radiology, University Hospitals Grosshadern, Ludwig-Maximilians-University Munich, Marchioninistr. 15, 81377 Munich, Germany. Ulrike.attenberger@med.uni-muenchen.de
authors.forename: U I
authors.initials: UI
authors.lastname: Attenberger
authors.forename: S P
authors.initials: SP
authors.lastname: Sourbron
authors.forename: M
authors.initials: M
authors.lastname: Notohamiprodjo
authors.forename: K P
authors.initials: KP
authors.lastname: Lodemann
authors.forename: C G
authors.initials: CG
authors.lastname: Glaser
authors.forename: M F
authors.initials: MF
authors.lastname: Reiser
authors.forename: S O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: H J
authors.initials: HJ
authors.lastname: Michaely
mesh_terms: D003287:Contrast Media; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007674:Kidney Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives; D008875:Middle Aged; D015588:Observer Variation; D009942:Organometallic Compounds; D011446:Prospective Studies; D012079:Renal Circulation
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine