This work continues the development of the use of magnetic resonance imaging (MRI) techniques to characterize fluid/particulate mixtures during pipe flow. A primary application of this research is to aseptic processing of these mixtures by heat treatment. The heat treatment of flowing fluid/particulate systems is influenced by the fact that incorporating particles into a suspending fluid alters the velocity profile during pipe flow, and therefore the residence time distribution in a thermal system. MRI techniques were used to noninvasively determine velocity profiles of pure fluids and fluid/particulate mixtures. With this information and a suspension rheology analysis, the relationship between relative viscosity, shear rate, and particle loading was determined. The results were characterized by a parameter that reflects the physics of particle migration during flow and the constitutive model for the viscosity as a function of particle loading. The predicted particle concentration varied between 50 and 150% of the average particle concentration, from a low loading in the high shear region near the pipe wall to a high particle loaning at the pipe center.