Malignant tissues can be effectively treated by Total Skin Electron Therapy (TSET) over the entire body surface using 6 MeV electron beams. During the radiation treatment, Cherenkov photons are emitted from the patient’s skin, and can potentially be used for in-vivo imaging of the radiation dose distribution. A Monte Carlo (MC) simulation toolkit TOPAS is used to study the generation and propagation of Cherenkov photons that are generated from the interaction of electron radiation with human tissues, and to understand the relationship between the dose distributions and the Cherenkov photon distributions. Validation of MC simulations with experiments are performed at 100 SSD and 500 SSD, and simulations of a patient phantom in realistic clinical treatment setups have been done. These simulations with TOPAS show that the emitted Cherenkov distributions at phantom surfaces closely follow their corresponding dose distributions.