Introduction:
Although there are several ways to relief pain in metastatic patients, the use of radionuclides is one of the known and effective ways to relieve the pain caused by bone metastases. The purpose of this study was to assessment of radiation dose distribution of different radioisotopes used to treatment and pain relief patients in a bone-based model based on Monte Carlo simulation for particle transport.
 
Materials and Methods:
Distribution of radiation dose of six different radioisotopes such as Sm-153, Re-188, Lu-177, Re-186, Sr-89, Ra-223 was done in a foot-bone model using the MCNPX computational code for particle transport. The RADAR decay nuclear data on gamma and beta radiation and the probability emission of each, as well as the recommended ICRU and ICRP data for bone marrow, bone and soft tissue components were used in the dose calculations.
Results:
After performing of simulation calculations, the absorbed dose spectrums of gamma and beta- rays of radioisotopes mentioned above were calculated according to foot phantom radius, separately. Also, bar charts were used for comparison of the absorbed dose to bone marrow, bone and soft tissue. The highest dose delivered to the bone was related to Ra-223 alpha ray and beta ray of Re-188 and Sr-89.
Conclusion:
The delivered absorbed dose to the bone tissue as a therapeutic target by alpha ray of Ra- 223 and beta rays of Re-188 and Sr-89 was maximum and the amount of absorbed dose delivered to bone marrow and soft tissue by gamma rays of Sr-89 and Re-188 was high. Accordingly, the choose of widespread clinically used radioisotopes such as Sr-89 and Sm- 153 to treatment and pain relief patients seems to need be revised and more careful.