Monte Carlo simulations for targeted beta therapy: An optimization for liver lesions and comparison of dose distributions in other organs

Objective

To optimize targeted beta therapy for liver lesions in adult male phantom by comparing the efficacy and safety profiles of five different beta-emitting radionuclides: ⁹⁰Y, ¹⁶⁶Ho, ¹⁵³Sm, ⁴⁷Sc, and ¹⁷⁷Lu.

Methods

This study includes Monte Carlo simulations of the behavioral characteristics of five different beta emitters that have current or potential use in targeted beta therapy. The energy loss of beta particles moving within the material through ionization or chemical processes, the energy transferred to the material, the energy lost by beta particles along the distance traveled within the tissue, and consequently, the stopping power are calculated using the Bethe-Bloch formula. The CSDA (continuous slowing-down approximation) range of beta particles within the tissue is examined using ESTAR and GEANT codes, while the stopping power of the tissue is investigated using FLUKA, ESTAR, and GEANT codes. Tissue dose calculations for the target organ are obtained using the IDAC-Dose2.1 and MIRDcalc simulation programs, using parameters such as absorbed dose per accumulated activity (S-factor) and specific absorbed fraction (SAF). Additionally, dose and flux values are obtained using the PHITS program.

Results

The behaviors and dose contribution of beta particles in liver tissue have been addressed in various ways. ⁹⁰Y, which has the highest average beta energy, was observed to provide a higher absorbed dose value in the liver compared to other beta-emitting isotopes, while the lowest absorbed dose was observed with ¹⁷⁷Lu. In other organs, it has been observed that ⁹⁰Y and ⁴⁷Sc contribute to a higher absorbed dose compared to other beta-emitting isotopes.

Conclusions

This study emphasizes the complexity and significance of targeted beta therapy optimization.