Dosimetry at the sub-cellular scale of Auger-electron emitter 99mTc in a mouse single thyroid follicle

Abstract

The Auger-electrons emitted by 99mTc 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 99mTc a pertinent and pressing subject. The S-values for 99mTc 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 99mTc within different cellular compartments in a single mouse thyroid follicle model, considering the radiative and non-radiative transitions of the 99mTc radiation spectrum. It was shown that the contribution of the 99mTc 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 99mTc play a significant role in the occurrence of the thyroid stunning effect in mice.