Dosimetry Evaluation on the Use of 18F-FDG for PET/CT Imaging using OLINDA/EXM and Geant4 Monte Carlo Simulations - A Single Centre Experience.

Abstract

Background: PET/CT using ¹⁸F-FDG has been increasingly used for diagnostic imaging. Thus, dosimetry evaluation is crucial to minimise unnecessary radiation exposure to other organs. This study aimed to evaluate the absorbed dose to patients undergoing ¹⁸F-FDG sequential PET/CT imaging in the Institut Kanser Negara (IKN), Putrajaya, Malaysia using OLINDA/EXM and Geant4 MC simulation, focusing on identifying the most suitable method for clinical application and analysing whether the absorbed dose complies with the safety standard set by ICRP 128.

Methods: OLINDA/EXM (version 1.1) and Geant4 MC (version 10.6.0) software were used to evaluate the absorbed doses to the liver, kidneys, and urinary bladder. MIRD-5 mathematical phantom was used in Geant4 MC simulation, whereas in OLINDA/EXM, adult male and female models with organ masses normalised to the Japanese reference model were applied.

Results: The mean absorbed doses to the liver, kidneys, and urinary bladder were 0.010 ± 0.006 mGy/MBq, 0.011 ± 0.004 mGy/MBq, and 0.025 ± 0.047 mGy/MBq, respectively, for OLINDA/EXM, and 0.009 ± 0.004 mGy/MBq, 0.011 ± 0.003 mGy/MBq, and 0.073 ± 0.086 mGy/MBq, respectively, for Geant4 MC. The corresponding differences between these two methods were 10.526%, 0%, and 97.959%, respectively for the liver, kidneys, and urinary bladder. The results comply with the ICRP-128 limits, indicating the safe use of ¹⁸F-FDG for diagnostic purposes in IKN.

Conclusion: Both methods were shown to be reliable in estimating the absorbed dose for ¹⁸F-FDG. The selection of the methods for absorbed dose estimation depends on the capacity of the clinics (i.e., in terms of time and computational capability [power and literacy]).