Brachytherapy Advanced Example

Developers

Since 2007 the Brachytherapy example is maintained and upgraded by Susanna Guatelli (1), Dean Cutajar (1) and Albert Lee (1), with the support of Luciano Pandola (2) .

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

Past contributors:

• S. Agostinelli (Istituto Tumori, Genova, Italy),
• S. Garelli (Istituto Tumori, Genova, Italy)
• M.G.Pia (INFN, Genova, Italy),
• M. Tropeano (Universita' di Genova, Italy)

Introduction

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

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

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 user can define other brachytherapic sources without changing the example implementation.

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:
  1. Define the energy spectrum of photons exiting the radioactive core or
  2. Modelling the Radioactive Decay
• Calculate the energy deposition in a phantom by means of the G4 scoring mesh
• Define the physics by means of a Geant4 Modular Physics List
• Save results in an analysis ROOT file
• Calculate the dose rate distribution along the main axis of the source
• Compare the calculated dose rate distribution to reference data. In the case of the example, the dose rate distribution of a Flexisource is compared to 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 example can be executed in multithreading mode.

Comparison to reference data

The user can compare the dose rate distribution g(r) for 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 and executed for each reference tag of Geant4.