Dosimetric Comparison of Different Radionuclides Used in Metastatic Bone Disease Treatment.

Introduction: This study aimed to determine the critical organ doses in ²²³Ra, ⁸⁹Sr, ¹⁵³Sm, and ³²P treatments via dosimetry using the phantoms.

Material and methods: The OpenDose was used to calculate S values (mGy MBq^-1s^-1) for bone surface, red bone marrow, urinary bladder wall, testes, ovaries, uterus, and kidneys using male (ICRP110AM) and female (ICRP110AF) phantoms. The cortical thoracic spine was modeled as metastasis. Moreover, the absorbed doses were computed via MIRD formalism according to the activities of 3.3, 148, 2220, and 370 MBq for ICRP110AM and 4.015, 148, 2701, and 370 MBq for ICRP110AF in ²²³Ra, ⁸⁹Sr, ¹⁵³Sm, and ³²P treatments, respectively.

Results: Whilst the maximum bone surface doses were found as 1.22E+02 and 8.51E+01 mGy at ³²P treatment, the minimum bone surface doses were calculated as 8.42E-02 and 8.26E-02 mGy at ²²³Ra. In terms of the comparison of red bone marrow, urinary bladder wall, and kidney doses, ¹⁵³Sm and ⁸⁹Sr treatments showed maximum doses of 2.45E-03, 1.50E-03, 3.23E-07, 5.45E-06, 1.20E-01, 1.49E-01 mGy and the minimum doses with 3.46E-05, 1.99E-05, 6.33E-09, 8.77E-09, 1.19E-04, 1.15E-04 mGy, respectively. The maximum testes and ovaries-uterus doses were found as 6.17E-08, 7.40E-06, 3.46E-07 mGy in ¹⁵³Sm treatment, and minimum testes and ovaries doses as 1.70E-09, 1.34E-07 mGy in ²²³Ra. The minimum uterus dose with 7.03E-09 mGy was determined in ⁸⁹Sr treatment.

Conclusion: It is observed that ²²³Ra produces low critical organ doses in the treatment of painful bone metastasis. Among the beta-emitting radionuclides, ⁸⁹Sr stands out by showing optimal dosimetric results.