Comparison of Local-rigid and Non-rigid Registration of Diffusion Weighted MRI for Improved Estimation of ADC

Our aim is to develop methodologies for the determination of ADC, suitable for use in patient management and drug trials. In this paper we demonstrate improvements in ADC measurement which at the same time maintain the biological structures essential for analysis of tissue heterogeneity. Two motion correction methods are compared, one based upon non-rigid registration using freely available open source algorithms and the other a purpose designed local rigid registration. Performance of these methods is evaluated using metrics computed from regional ADC histograms. While the nonrigid registration method has the advantages of being applicable on the whole volume and in a fully automatic fashion, the local rigid registration method is much faster and also provides advantages with regard to data smoothness by avoiding interpolation and sub-sampling. Our study also shows that the averaging commonly applied to DW-MR images as part of the acquisition protocol should be avoided if at all possible.