Mass-transfer based modeling to investigate iodine staining effects for enhanced contrast X-ray computed tomography

Iodine staining combined with X-ray computed tomography (CT) has become a core approach in anatomy, offering three-dimensional and essentially non-destructive imaging of soft tissues. Although there have been rapid advances in methodologies and techniques, the mechanisms underlying diffusible iodine contrast-enhanced CT are not yet fully understood. The protocols for staining samples of differing sizes and tissue types have not yet been justified theoretically. Here we utilize mass transfer modeling to simulate iodine diffusion and predict iodine concentrations within distinct tissue types. We also undertake iodine staining experiments to visualize the detailed anatomy and contrast effects on whole-body avian specimens using different concentrations of iodine solution to compare with model simulation results. The simulations effectively explain most observed concentration changes in differently-sized samples over distinct iodine treatment durations. These results also provide insight into the mechanisms behind the efficacy of solution replenishment for enhancing staining effects. Both consistencies and inconsistencies between our simulation and experimental results regarding iodine concentration in tissues will inform further investigations to optimize iodine staining protocols.