ESTRO 2025 - Abstract Book

S2695

Physics - Dose calculation algorithms

ESTRO 2025

3. Pastor-Serrano O, Perkó Z. Millisecond speed deep learning based proton dose calculation with Monte Carlo accuracy. Phys Med Biol. 2022 May 9;67(10). PMID: 35447605. 4. Neishabouri A, Wahl N, Mairani A, Köthe U, Bangert M. Long short-term memory networks for proton dose calculation in highly heterogeneous tissues. Med Phys. 2021 Apr;48(4):1893-1908. doi: 10.1002/mp.14658. Epub 2021 Mar 11. PMID: 33332644.

2079

Digital Poster Monte Carlo-based Dosimetry of 241Am in a Custom Cell Irradiation Set-up for Targeted Alpha Therapy Radiobiology Studies Maryam Rahbaran 1,2 , Joanna Li 1,2 , Shirin A. Enger 1,2 1 Medical Physics Unit, McGill University, Montreal, Canada. 2 Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Canada Purpose/Objective: Targeted Alpha Therapy utilizes the high linear energy transfer of alpha particles for targeting tumors while sparing organs at risk due to their short ranges in tissue. Several radionuclides, including 225 Ac and 223 Ra, have been used in pre-clinical studies and clinical trials as radiopharmaceuticals for cancer treatment [1]. Determining the relative biological effectiveness (RBE) of alpha particles is currently of interest to allow for patient-specific multi-scale dosimetry. 241 Am is a useful radionuclide for studying the RBE of alpha particles, as it emits high energy alpha particles and few low energy gamma particles [2]. The purpose of this study was to develop a Monte Carlo-based software to characterize a custom cell irradiation set-up, allowing for accurate alpha particle dosimetry in RBE studies. Material/Methods: A Monte Carlo-based dose calculation software based on Geant4 10.02.p02 was developed [3]. A custom cell irradiation set-up was modelled in the software, including a 241 Am source of 5 mm in diameter plated on platinum foil and surrounded by aluminum components, a stainless-steel cell well with a 4.96 mm diameter opening, and 5µm cells seeded on a Kapton foil at 2 mm from the source (Figure 1). The G4EmStandardPhysics_option4 physics list was used, and dose was scored in 0.01x0.01x0.005 mm 3 voxels. Simulations were run on the Cedar computing cluster of the Digital Research Alliance of Canada with 5×10 10 histories to yield uncertainties of less than 1% in each voxel. The software was validated against Nishri et al., who reported a dose rate of 0.1 Gy/min [4].