Comparative study into the robustness of compartmental modeling and model‐free analysis in DCE‐MRI studies

Purpose To evaluate and compare the reproducibility of the preferred phenomenological parameter IAUC 60 (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. Materials and 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 T 1 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 IAUC 60 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 IAUC 60 and K trans , changes in excess of 47% and 31%, respectively, are outside the range of normal variability. Conclusion 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. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.