<![CDATA[Bone scintigraphy using Technetium-99m methylene diphosphonate (Tc-99m MDP) is a nuclear medicine imaging procedure widely used for the diagnosis of various skeletal disorders. The use of hybrid Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) provides simultaneous functional and anatomical information; however, it also results in radiation exposure from both the administered radiopharmaceutical and the CT component. This study aimed to estimate the effective doses associated with the radiopharmaceutical and CT components and to determine their respective contributions to the total estimated effective dose in bone scan SPECT/CT examinations. A retrospective study was conducted in 44 patients who underwent bone scan SPECT/CT examinations at Dr. M. Djamil Hospital, Padang, Indonesia, between March and May 2026. The radiopharmaceutical effective dose was estimated based on the administered Tc-99m MDP activity, whereas the CT effective dose was estimated from the Dose-Length Product (DLP). The mean administered radiopharmaceutical activity was 707.83 ± 106.27 MBq, corresponding to an estimated effective dose of 3.47 ± 0.52 mSv. The mean DLP was 642.09 ± 188.54 mGy·cm, corresponding to an estimated CT effective dose of 8.35 ± 2.48 mSv. The mean total estimated effective dose was 11.82 ± 2.74 mSv. The CT component contributed 69.72% of the total estimated effective dose, whereas the radiopharmaceutical component contributed 30.28%. These findings indicate that the CT component contributed a greater proportion of the total estimated effective dose in bone scan SPECT/CT examinations.]]>
