title: Comparative study into the robustness of compartmental modeling and model-free analysis in DCE-MRI studies.
abstract: OBJECTIVE
  To evaluate and compare the reproducibility of the preferred phenomenological parameter IAUC60 (initial area under the time-concentration curve [IAUC] defined over the first 60 seconds postenhancement) with the preferred modeling parameter (K(trans)), as derived using two simple models, in abdominal and cerebral data collected in typical Phase I clinical trial conditions.
  
  
  METHODS
  Dynamic contrast enhanced MRI (DCE-MRI) time series were acquired at two imaging centers from a group of patients with abdominal tumors and a group with gliomas. At both imaging centers, precontrast T1 was calculated using a variable flip angle three-dimensional spoiled gradient echo acquisition that was used to quantify tissue contrast agent concentration, allowing voxelwise definition of summary DCE-MRI parameters.
  
  
  RESULTS
  A comparison of reproducibility showed that there was no statistically significant difference in reproducibility between IAUC60 and K(trans), although there was a trend towards better reproducibility for K(trans) (P = 0.0782). The 95% confidence intervals (CIs) for individual changes showed that for IAUC60 and K(trans), changes in excess of 47% and 31%, respectively, are outside the range of normal variability.
  
  
  CONCLUSIONS
  Although modeling is more complex and more computationally intensive than an IAUC parameterization, our data suggest this approach to be preferable to a model-free approach since it provides greater physiological insight without a reduction in statistical power for Phase I/II clinical drug trials.
authors.affiliation: Imaging Science and Biomedical Engineering, University of Manchester, Manchester, UK.
authors.forename: Caleb
authors.initials: C
authors.lastname: Roberts
authors.forename: Basma
authors.initials: B
authors.lastname: Issa
authors.forename: Andrew
authors.initials: A
authors.lastname: Stone
authors.forename: Alan
authors.initials: A
authors.lastname: Jackson
authors.forename: John C
authors.initials: JC
authors.lastname: Waterton
authors.forename: Geoffrey J M
authors.initials: GJ
authors.lastname: Parker
mesh_terms: D000008:Abdominal Neoplasms / Q000473:pathology*; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001254:Astrocytoma / Q000473:pathology*; D001932:Brain Neoplasms / Q000473:pathology*; D003287:Contrast Media / Q000493:pharmacokinetics*; D005260:Female; D019786:Gadolinium DTPA / Q000493:pharmacokinetics*; D005909:Glioblastoma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000473:pathology; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA