Background: ¹⁷⁰Tm-EDTMP has been proposed as a radiopharmaceutical with desirable properties and an alternative to ⁸⁹Sr-Cl₂ for the palliative treatment of patients with bone metastasis. This study aimed to calculate the absorbed dose of ¹⁷⁰Tm-EDTMP in the bone of patients with bone metastasis.
Materials and Methods: In this study, an adult human femur phantom and the GATE Monte Carlo toolkit were used for simulation. ¹⁷⁰Tm-EDTMP was distributed in the bone compartment, and the absorbed dose per disintegration was calculated in the different phantom compartment. In order to comparison and validation of results, simulations with similar conditions were performed for ⁸⁹Sr-Cl₂. Then, the absorbed dose per administered activity of radiopharmaceuticals in the bone and bone marrow was calculated using the MIRD method and compared with each other.
Results: The bone absorbed dose per administered activity for ¹⁷⁰Tm-EDTMP was 5.52 times higher than ⁸⁹Sr-Cl₂, while the bone marrow absorbed dose by ¹⁷⁰Tm-EDTMP was 2.11 times higher than ⁸⁹Sr-Cl₂.
Conclusion: According to the results obtained in this study, ¹⁷⁰Tm-EDTMP is a suitable radiopharmaceutical for use in the palliative treatment of patients with bone metastases. However, in order to further investigation, there is a need for clinical trial in the patients.

Keywords: Thulium-170, Palliative therapy, Monte Carlo method, Absorbed dose

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