The subject disclosure presents systems and computer-implemented methods for calculating the diffusivity constant of a sample using acoustic time-of-flight (TOF) based information correlated with a diffusion model to reconstruct a sample's diffusivity coefficient. Operations disclosed herein such as acoustically determining the phase differential accumulated through passive fluid exchange (i.e. diffusion) based on the geometry of the tissue sample, modeling the impact of the diffusion on the TOF, and using a post-processing algorithm to correlate the results to determine the diffusivity constant, are enabled by monitoring the changes in the speed of sound caused by penetration of fixative such as formalin into several tissue samples. A tissue preparation system may be adapted to monitor said diffusion of a tissue sample and determine an optimal processing workflow.