Advanced Example brachytherapy

 

Responsible Geant4 Collaborator: Susanna Guatelli, Centre For Medical Radiation Physics, Wollongong University, Australia.

Current contributors: Susanna Guatelli (1), Albert Le (1) and Dean Cutajar (1), with the support of Luciano Pandola (2)

  1. Centre For Medical Radiation Physics (CMRP), University of Wollongong, NSW, Australia

  2. LNS, INFN, Catania, Italy

Past contributors: S. Agostinelli (Istituto Tumori, Genova, Italy), S. Garelli (Istituto Tumori, Genova, Italy), S. George (Centre For Medical and Radiation Physics, Wollongong University, Wollongong, Australia), M.G. Pia (INFN, Genova, Italy), M. Tropeano (Universita’ di Genova, Italy)

Short description

This example allows to calculate the energy deposition/dose in a water phantom produced by a brachytherapy source. The user can select a source among the following options:

  • Iridium sources (Flexisource and TG186).
  • Iodine source (Bebig Isoseed I-125 and Oncura).
  • Leipzig Applicator with an iridium source (model from the Istituto Tumori, Genova, Italy).

The sources are shown in Figure 1.

Brachy sources
Figure 1: Brachytherapy sources implemented in the Geant4 Advanced Example Brachytherapy. Sizes not to scale.

The Flexisource, an Ir-192 source manufactured by Nucletron, an Elekta company, is a source commonly used for high dose rate brachytherapy treatments. The geometry of the Flexisource was adapted from D. Granero, J. Pérez-Calatayud, E. Casal, et al, “A dosimetric study on the Ir-192 high dose rate Flexisource”, Med. Phys. 33 (12), 2006, 4578-82.

The TG186 source is a generic Ir-192 source created to provide developers of model based dose engines with a method of validating new dose calculation techniques. Details of the TG186 source may be obtained from Facundo Ballester, Åsa Carlsson Tedgren, Domingo Granero, et al, “A generic high-dose rate 192Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism”, Med. Phys. 42, 2015, 3048-62.

The Leipzig applicator geometry was kindly provided by the Istituto Tumori, Genova, Italy.

This example shows how to:

  • Model a radioactive source in terms of radiation field and geometry
  • Model the radiation field with the General Particle Source with two alternative methods:
    • Define the energy spectrum of photons exiting the radioactive core or
    • Modelling the Radioactive Decay
  • Calculate the energy deposition in a phantom by means of the Geant4 scoring mesh
  • Define the physics by means of a Geant4 Modular Physics List
  • Save results in an analysis ROOT file
  • Calculate the radial dose rate distribution along the main axis of the source

Comparison to reference data

The user can compare the radial dose rate g(r) of the Flexisource and the Oncura sources calculated by means of the example to reference data. Please read the README file of the example in order to do so.

This comparison is included as benchmarking test in geant-val within the G4-Med project. Reference publication: Arce P. et al, “Report on G4-Med, a Geant4 benchmarking system for medical physics applications developed by the Geant4 Medical Simulation Benchmarking Group”, Medical Physics, 2020.

Last updated: 05/02/2022 by S. Guatelli