The whole-body fluorodeoxyglucose F18 (18F-FDG) and gallium-68 (Ga-68 DOTATATE) are the most common radiopharmaceutical use in PET/CT imaging for cancer staging. Although radiopharmaceutical for PET/CT examination has been acknowledged for its safety and efficacy, the internal dosimetry and effective dose (ED) from the examinations are rarely discussed. Hence, this study aimed to evaluate radiation ED for whole-body radiopharmaceuticals PET/CT concerning patients’ gender and their weight. A total of 82 oncology patients (44 males and 38 females) were collected retrospectively from Institut Kanser Negara, Putrajaya. Data, such as 18F-FDG and Ga-68 DOTATATE activity and patient demography (weight, height, age), were recorded and analyzed. Effective doses from both internal and external exposure were calculated using the coefficient
provided by the International Commission on Radiological Protection (ICRP) report. The total ED of 18F-FDG for male patients was 20.2 ± 8.6 mSv and for female patients were 19.0 ± 8.2 mSv while total whole-body ED for Ga-68 DOTATATE for male patients was 18.5 ± 7.0 mSv and 17.0 ± 5.6 mSv for female patients. The ratio for ED between male and female were 1:1 for both examinations ranged from 12.0 – 23 mSv. From this study, it indicated that the ED of Ga-68 DOTATATE was far lower when compared to the ED of 18F-FDG by a factor of 0.7. Therefore, it is crucial to optimize the PET/CT protocol dose in order to uphold the dose as low as reasonably achievable (ALARA).