Improved Robustness with a Stretched Exponential Model for Intravoxel Incoherent Motion (IVIM) DW Signal

INTRODUCTION Le Bihan et al (1) proposed using diffusion-weighted imaging (DWI) based on intravoxel incoherent motion (IVIM) to distinguish pure molecular diffusion and microcirculation, or blood perfusion, by acquiring DW data with the diffusion sensitivity parameter b at low values (<200 sec/mm and at high values (>200 s/mm). The ability of IVIM to provide sensitive and specific values for the bi-exponential (BE) model is severely limited due to 1) the narrow range of relevant b-values associated with pseudo-diffusion in the faster diffusion component (i.e., the large slope of ln(S(b)) vs. b) and 2) the high degree of signal variability in low b-value measurements. We propose the stretched exponential (SE) model, previously considered for modeling high b-value data (2), as an alternative to describe IVIM diffusion signal.