Dosimetry at the sub-cellular scale of Auger-electron emitter super(99m)Tc in a mouse single thyroid follicle

The Auger-electrons emitted by super(99m)Tc have been recently associated with the induction of thyroid stunning in in vivo experiments in mice, making the dosimetry at the sub-cellular level of super(99m)Tc a pertinent and pressing subject. The S-values for super(99m)Tc were calculated using MCNP6, which was first validated for studies at the sub-cellular scale and for low energies electrons. The calculation was then performed for super(99m)Tc within different cellular compartments in a single mouse thyroid follicle model, considering the radiative and non-radiative transitions of the super(99m)Tc radiation spectrum. It was shown that the contribution of the super(99m)Tc Auger and low energy electrons to the absorbed dose to the follicular cells' nucleus is important, being at least of the same order of magnitude compared to the emitted photons' contribution and cannot be neglected. The results suggest that Auger-electrons emitted by super(99m)Tc play a significant role in the occurrence of the thyroid stunning effect in mice.