The diffusion coefficient D, depending on the viscosity, molecular size (mass) and temperature (cf. Fig. 1a for H 2 O), affects the diffusion properties of the phantom. Download: Download high-res image (739KB) Download: Download full-size image Fig. 1.Liquids that are popular test phantoms in dMRI, according to increasing complexity: a) D as a function of temperature for water, whereby ice.