Effect of image registration on the estimation of pharmacokinetic parameters from DCE-MRI of patients with esophageal cancer

We investigated the effectiveness of the most commonly used registration methods (deformable and rigid-body registrations) with different reference images on pharmacokinetic parameters estimated from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) of esophageal cancer patients. We obtained DCE-MRI images from 10 patients with esophageal cancer. Both rigid-body and deformable registrations of the images were performed on DCE-MRI images at different time points as reference images before the pharmacokinetic parameters were estimated. The deformable registration used non-rigid B-spline transforms in a multi-resolution scheme, and Euler transform were used for the rigid body registration. A nonparametric statistical test and the intra-class correlation coefficient assessed the consistency and reproducibility of the pharmacokinetic parameters estimated with both registration methods and using images acquired at different time points. Kruskal-Wallis testing demonstrated significant differences (p < 0.05) in all the estimated parameters for deformable registration but no significant differences (p > 0.78) for rigid-body registration. The intra-class correlation coefficient for rigid-body registration was higher than that for deformable registration for each pharmacokinetic parameter, indicating that, for rigid-body registration, the parameter values from different reference images of one patient tended to be similar to each other. In contrast, the values for deformable registration were more variable. In conclusion, the choice of the reference image of deformable registration significantly affected the estimates of pharmacokinetic parameters, and rigid-body registration showed small variations in pharmacokinetic parameters over the choice of the reference images for small motion artifacts of small distal esophageal cancer on DCE-MRI.