A Standardized Parameter-Free Algorithm for Combined Intravoxel Incoherent Motion and Diffusion Kurtosis Analysis of Diffusion Imaging Data. Issue 3 (March 2016) - Wurnig, Moritz C.
Abstract : Objectives: The aims of this study were to implement and systematically evaluate the performance of a new parameter-free segmented algorithm for analysis of diffusion imaging data using a combined intravoxel incoherent motion and diffusion kurtosis imaging (IVIM-DKI) model of spin diffusion in comparison with the simpler intravoxel incoherent motion (IVIM) model. Materials and Methods: A multistep algorithm was implemented intended to separate diffusion kurtosis from IVIM effects in multi- b -value diffusion measurements using an adaptive b -value threshold technique. For each possible b -value threshold (separating diffusion and perfusion effects), diffusion kurtosis analysis of high b -values is followed by IVIM analysis keeping kurtosis parameters fixed. The b -value threshold with smallest Akaike information criterion is chosen as best model solution. The algorithm was tested in diffusion data sets of the upper abdomen from 8 healthy volunteers with 16 different b -values and compared with a standard multistep IVIM analysis. Results: The proposed algorithm could successfully be applied to all data sets and provided a significantly better fit of the observed signal decay in all assessed organs (all P < 0.03). Using the proposed IVIM-DKI model of diffusion instead of an IVIM model had a systematic impact on the resulting IVIM parameters: The pure diffusion coefficient and the pseudodiffusion coefficient were significantly increased ( P < 0.03 in all assessed organs), accompanied by a decrease in the perfusion fraction in liver, pancreas, renal cortex, and skeletal muscle (all P < 0.02). Optimal b -value thresholds separating diffusion from perfusion effects had a tendency to lower values when the IVIM-DKI model was used. Conclusions: The proposed algorithm provides a new approach for separation of IVIM and kurtosis effects of diffusion data without organ-specific adaptation.