Cellular dosimetry of 197Hg, 197mHg and 111In: comparison of dose deposition and identification of the cell and nuclear membrane as important targets

Purpose To examine the reliability to model cellular S-values for the Auger electron (AE) emitters, In-111, Hg-197 and Hg-197m with MCNP6 and their relative dose deposition in subcellular targets. Methods A model cell was defined as four concentric spheres consisting of the nucleus (N), cytoplasm (Cy), cell and nuclear membranes (CM, NM) in which radionuclides distributed homogeneously. The transport of AE, conversion electrons and photons were simulated by MCNP6 to calculate cellular S values (S-N <- CM, S-N <- Cy, S-N <- NM, S-N <- N, S-CM <- CM, S-NM <- NM). S-N <- CM, S-N <- Cy and S-N <- N were also calculated with MIRDcell. Results MIRDcell and MCNP6-calculated S-N <- N were in excellent agreement, but a slight discrepancy on S-N <- Cy and S-N <- CM was observed. The ratios of S-CM <- CM or S-NM <- NM vs. S-N <- N were 9.7-51.0 or 10.5-37.4, 7.9-41.8 or 8.4-31.8 and 7.2-36.9 or 8.0-28.1 for In-111, Hg-197, Hg-197m, respectively. The mean S(Hg-197)/S(In-111) and S(Hg-197m)/S(In-111) were 2.5 +/- 0.5 and 2.5 +/- 0.6, respectively. Conclusions Cellular S-values were reliably calculated with MCNP6. Hg-197 and Hg-197m deposit two-fold more doses than In-111 at the subcellular scale. All AE emitters deposit a higher self-dose in the CM and NM than in the N, which warrants studies on the effects of targeting the CM and NM by AE emitters.

Automated summary

The reliability of modeling cellular S-values for AE emitters and their relative dose deposition in subcellular targets were examined using MCNP6. Results showed that Hg-197 and Hg-197m deposit two-fold more doses than In-111 at the subcellular scale. All AE emitters deposit a higher self-dose in cellular and nuclear membranes compared to the nucleus.