• 153Sm-EDTM
• Monte Carlo simulation
• radiation dose

Bone metastases are a very common problem in clinical oncology, affecting approximately 70% of patients with prostate or breast cancer. Radiopharmaceutical therapy has proved effective with minimal side effects for treatment of refractory painful skeletal metastases of the blastic or mixed type, but administered activities are generally based on limited series of clinical studies without a proven correlation between the activity and the delivered dose to metastatic lesions. In bone pain palliation therapy the red marrow is generally the dose-limiting organ and due to the complex microstructure of the skeleton it has been difficult to calculate accurately the dose deposited to this region. Thus, the estimation of dose to the skeletal system at the microscopic level has been limited by the lack of a realistic characterization of the trabecular bone architecture. The dose distribution to bone marrow of metastatic lesions for the bone seeking radiopharmaceutical 153Sm EDTMP has been evaluated using a Monte Carlo simulation. In this setting a new dosimetric model has been developed based on the micro-CT analysis of bone metastases to investigate the morphology, topology and texture of bone samples based on assessment of the micro-structural parameters classically evaluated with histomorphometry. The distribution of radiation dose and the mean absorbed dose per unit cumulated activity (S value) were computed for bone marrow space.