Assessment of weight-based variations in effective dose for common PET/CT scans in a tertiary hospital.

BACKGROUND: Positron Emission Tomography/Computed Tomography (PET/CT) is a crucial imaging modality widely used for diagnosing and staging various cancers. Although patient weight is known to influence radiation dose, there is limited research on optimizing PET/CT protocols based on weight categories to minimize unnecessary exposure. OBJECTIVES: This study evaluates the effective dose for common PET/CT scans at Penang Hospital, with a particular focus on the influence of patient weight on both PET and CT dose components. Additionally, the study assesses whether weight-based dose protocols can contribute to dose optimization. METHODS: This retrospective study analyzed 1439 PET/CT scans performed at Penang Hospital. The effective dose was calculated using International Commission on Radiological Protection (ICRP) 103, 106, and 128 dose coefficients. Conversion factors used were 0.019 mSv/MBq for 18F-FDG, 0.0199 mSv/MBq for 68Ga-PSMA, and 0.021 mSv/MBq for 68Ga-DOTATATE. The CT dose component was estimated using the dose-length product (DLP) with an empirical conversion factor (k = 0.015 mSv·mGy-1·cm-1) for whole-body CT. RESULTS: The total effective dose for 18F-FDG (head-to-thigh and head-to-feet) scans was 12.34 and 16.38 mSv, respectively. For 68Ga-PSMA and 68Ga-DOTATATE scans, the total effective dose was 11.55 and 12.00 mSv, respectively. A statistically significant increase in dose was observed in heavier patients due to increased administered activity and CT parameters (P < .05). Weight had a smaller impact on PET dose in 68Ga-PSMA and 68Ga-DOTATATE compared to 18F-FDG. CONCLUSION: Patient weight significantly influences the total effective dose in PET/CT examinations. These findings highlight the importance of considering patient-specific factors when evaluating radiation dose in clinical practice.