Internal dosimetry in Nuclear Medicine with the application GATE: Evaluation of the impact of dose element and source type

For a realistic ¹⁸F simulation of dosimetry purposes, the preconfigured 'Fluor18' source, which simulates the positrons emission spectrum, should be used with all physical process of radiation interaction with matter. In conclusion, GATE application is a reliable and friendly environment for dose estimation in nuclear medicine imaging. GATE application (Geant4 Application for Emission Tomography) provides a series of tools that allow the collection of data from the interaction of radiation with matter during simulation, such as energy deposited and particles created within a volume, among others. The objective of this work is to evaluate the impact of the dose element size on the simulation of the absorbed dose in an attenuating medium in GATE application, using ^99mTc and ¹⁸F point sources. The influence of the dose map elements (dosel) size was investigated on the absorbed dose, as well as the impact of different source configurations. The results show that a matrix with larger voxels underestimates the absorbed dose values, especially when closer to the source. Thus, for a more accurate dosimetry it is recommended to use smaller dosels near the source. In relation to ¹⁸F simulation, they must be performed with the source preset as 'Fluor18', so all physical processes can be properly considered. It is concluded that the GATE application is a reliable environment for dose estimation in nuclear medicine imaging, allowing the investigation and selection of the most relevant radiation interaction processes with the material to perform internal dosimetry. (author)