A 3-D isotropic phase field simulation was used to predict the morphology of individual grains during grain growth. The simulation employed a polycrystalline array of titanium alloy Ti-β-21S experimentally characterized by X-ray tomography as an initial condition. The non-destructive nature of X-ray tomography allowed for a second characterization of the same sample following coarsening induced by a heat treatment. Thus, direct comparisons of individual grains between simulation and experiment could be made. Although the experimental system appeared isotropic from a statistical standpoint, direct examination of individual grains revealed very distinct anisotropy in the grain boundaries on the local scale. The comparison between experiment and phase-field simulations revealed regions with excellent agreement, despite the complex topological changes grains may undergo during grain growth. Thus, the sequence of topological transitions that occurred experimentally is correctly captured by the phase-field model. We therefore conclude that this phase-field model for isotropic systems has been verified experimentally.