LAUSR

PURPOSE Monte Carlo (MC) simulation is an important technique that can help design advanced and challenging experimental setups. GATE (Geant4 Application for Tomographic Emission) is a useful simulation toolkit for applications in nuclear medicine. Transarterial radioembolization is a treatment for liver cancer, where microspheres embedded with Yttrium-90 (90 Y) are administered intra-arterially to the tumour. Personalised dosimetry for this treatment may provide higher dosimetry accuracy compared to the conventional partition model (PM) calculation. However, incorporation of three-dimensional tomographic input data into MC simulation is an intricate process. In this article, 3D Slicer, a free and open-source software, was utilised for the incorporation of patient tomographic images into GATE, to demonstrate the feasibility of personalised dosimetry in hepatic radioembolization with 90 Y. METHODS In this article, the steps involved in importing, segmenting, and registering tomographic images using 3D Slicer were thoroughly described, before importing them into GATE for MC simulation. The absorbed doses estimated using GATE were then compared with that of PM. SlicerRT, a 3D Slicer extension, was then used to visualise the isodose from the MC simulation. RESULTS A workflow diagram consisting of all the steps taken in the utilisation of 3D Slicer for personalised dosimetry in 90 Y radioembolization has been presented in this article. In comparison to the MC simulation, the absorbed doses to the tumour and normal liver were overestimated by PM by 105.55% and 20.23%, respectively, while for lungs, the absorbed dose estimated by PM was underestimated by 25.32%. These values were supported by the isodose distribution obtained via SlicerRT, suggesting the presence of beta particles outside the VOIs. This finding demonstrate the importance of personalised dosimetry for a more accurate absorbed dose estimation compared to PM. CONCLUSION The methodology provided in this study can assist users (especially students or researchers who are new to MC simulation) in navigating intricate steps required in the importation of tomographic data for MC simulation. These steps can also be utilised for other radiation therapy related applications, not necessarily limited to internal dosimetry. This article is protected by copyright. All rights reserved.