Diffusion Weighted Imaging of Prostate and Rectal Wall: Comparison of Biexponential and Monoexponential Modelled Diffusion Coefficients

Diffusion weighted (DW) MRI is increasingly being used to identify prostate cancer, in particular to delineate tumors within the central gland where T2-W imaging has poor contrast between benign and malignant nodules. Quantitation using Apparent Diffusion Coefficients (ADC) usually entails monoexponential fitting of the DW data and does not account for the contribution from intravoxel incoherent motion (IVIM). Biexponential modelling over a large range of b-values allows the fast IVIM component to be separated from the slower component to reveal the volume fraction (PF) of microvasculature within a voxel and the ‘true’ molecular diffusion coefficient (D). The purpose of this study was to examine whether biexponentially derived diffusion coefficients (D) from prostate central gland (PCG), prostate peripheral zone (PPZ), and rectal wall (RW) tissues with 11 b values from 0-800s/mm improved modelling of these tissues and whether they were significantly different from monoexponentially derived apparent diffusion coefficients (ADCs).