title: Dynamic contrast enhanced-MRI in rectal cancer: Inter- and intraobserver reproducibility and the effect of slice selection on pharmacokinetic analysis.
abstract: OBJECTIVE
  To assess inter- and intraobserver reproducibility of DCE-MRI measurements and possible differences between two directly adjacent slices.
  
  
  METHODS
  DCE-MRI measurements of 30 patients with histologically proven rectal carcinoma were performed on a 1.5 Tesla (T) MR system during intravenous contrast agent application before and after neoadjuvant radiochemotherapy with two directly adjacent slices used for calculation per patient. Images were analyzed semiquantitatively (parameters TTP and MITR) and quantitatively using the Brix compartment model (parameters kep and A) by two different observers and at two different time points. The concordance correlation coefficient was calculated for every parameter in intra-/interobserver comparison and slice comparison.
  
  
  RESULTS
  Median relative differences below 10% for all parameters and high values of the concordance correlation coefficient (CCC) were found for most pharmacokinetic parameters in inter-/intraobserver comparison and slice comparison, with the exception of the parameter A before therapy in intra-/ interobserver comparison (CCC: 0.315/0.452) and kep before therapy in intraobserver comparison (CCC: 0.362).
  
  
  CONCLUSIONS
  Our results indicate good inter- and intraobserver reproducibility for most pharmacokinetic parameters and for the two adjacent slices measured. However, as there were some parameters that demonstrated poor correlation, testing for reproducibility and a multiobserver approach might be considered whenever using pharmacokinetic parameters as biomarkers.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Universitätsmedizin Mainz, Germany.
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Hötker
authors.forename: Irene
authors.initials: I
authors.lastname: Schmidtmann
authors.forename: Katja
authors.initials: K
authors.lastname: Oberholzer
authors.forename: Christoph
authors.initials: C
authors.lastname: Düber
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000493:pharmacokinetics*; D005260:Female; D019786:Gadolinium DTPA / Q000493:pharmacokinetics*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA
keywords: dynamic contrast-enhanced MRI; magnetic resonance imaging; rectal cancer; reproducibility; tumor microcirculation