The radiation dose delivered to the patient in radiotherapy is usually calculated using commercial software (“TPS”) which allows a very accurate calculation in the vast majority of clinical cases. However, it is sometimes necessary to have access to a reference calculation under certain complex conditions or for research purposes: very small treatment fields, presence of very dense heterogeneity, complex target motion, determination of reference data, etc. The Monte-Carlo method is considered as the reference calculation in medical physics and the GATE platform () is one of the most used tools in this field. It is based on the Geant4 computational library ( developed by the CERN physics teams. This article presents GAMMORA, a project developed at the CRCT that allows to easily generate Monte-Carlo GATE simulations for radiotherapy, for the VARIAN TrueBeam accelerator (one of the most common in the world). This tool has many applications in the field, some of which are presented here.  This is a technical note, i.e. a reference article that presents the project.

The clinical impact for these study was for example, modulated stereotaxy (SBRT VMAT) of bronchial cancers has started in the Department of Radiotherapy after evaluating the importance of the interplay effect using measurements and simulations with the GAMMORA tool.

The evaluation of a new commercial GST algorithm is also underway by comparing it with GAMMORA measurements and simulations.

The tool is open-source under the LGPL license.
This work is open access: (this link points to a github repository which contains all the documentation and publications related to the project)

Discover the published article :

Phys Med. 2021 Aug 17;89:211-218.doi: 10.1016/j.ejmp.2021.07.037. Online ahead of print.
Technical note: GAMMORA, a free, open-source, and validated GATE-based model for Monte-Carlo simulations of the Varian TrueBeam
Jeremy Leste, Tony Younes, Maxime Chauvin, Xavier Franceries, Alexia Delbaere, Laure Vieillevigne, Regis Ferrand, Manuel Bardies, Luc Simon

Key words :

  • Monte-Carlo ;
  • radiotherapy ;
  • geant4 ;
  • gate ;
  • gammora

Collaborations and acknowledgements

The authors were granted access to the HPC resources at the CALMIP supercomputing center under allocation 2016-P19001.

This study was supported by the French National Cancer Institute (INCa) under the framework of the 2016 Physics Cancer Project STEREPID.

Contact :

Luc Simon
CRCT Team : RADOPT : Optimization of radiotherapy: from mechanisms to clinical trials
Mail :

One picture

Example of radiotherapy modelling with GAMMORA. All elements of the machine head are modelled. A CT scan of a patient with bronchial cancer is used here.