brachytherapy

Introduction

Brachytherapy is a widely used medical device for cancer treatment. The software is used by medical physicists to define the treatment planning in order to deliver a therapeutic dose to tumors, preserving the surrounding healty tissues.

A software emploied to define the patient treatment planning must be rigourous and reliable for the cause of the delicate clinical use; the requirements for such a software are listed below.

The brachytherapic dosimetric software must:

  • be precise in the dose calculation;
  • reproduce the real geometry and tissues involved in the treatment (Computerised Thomography interface);
  • be fast in terms of computational time;
  • be simple to use (for hospitals!).

Brachytherapy example development

The example has been developed by: S. Agostinelli, S. Garelli , S. Guatelli, M.G.Pia, M. Tropeano with the medical physics consultancy of F. Foppiano.

The requested functionalities of the example are listed in the User Requirements file.

Features of the brachytherapy example

The result of the brachytherapy example is the dose calculation due to brachytherapic sources set inside a phantom. The brachytherapy example is generalised for all the brachytherapic techniques.

1. General features shared by the different brachytherapic techniques.

The application satisfies general functionalities which are shared by the different brachytherapic techniques:
  • it calculates the dose delivered in the phantom;
  • the isodose curves are obtained thanks to analysis instruments;
  • the user can choose the phantom materials interactively;
  • the user can visualize the experimental set-up.

2. Particular aspects of each brachytherapic source

The application satisfies also particular aspects of each brachytherapic device which consists in different source composition. The source is defined in the following terms:
  • in the geometry structure;
  • in the materials composition;
  • in the energy spectrum of the gamma delivered by the source.

The feature of generalisation + specific aspect of the sources is obtained thanks to the use of the design pattern Abstract Factory. Thanks to the use of this design pattern, the source definition is completely trasparent: the user communicates with the abstract object BrachyVFactory, indipendently from the concrete sorce definition. The defined sources are:

  • the interstitial source Bebig Isoseed I-125;
  • the endocavitary source MicroSelectron HDR Ir-192;
  • Leipzig Applicator.

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

3. Physics

The Geant4 Low Energy processes are activated for electrons and gamma. The Standard Processes are activated for positrons.

4. Detector

The phantom (sensitive detector) is devided in voxels (dimension=1mm); the energy deposit of a voxel is associated with the center of the voxel itself.

5.Analysis

  • The energy deposit information is stored in a ntuple;
  • The energy deposit in the plain containg the source is stored in a 2D histogram;
  • The primary particles energy spectrum is stored in a 1D histogram;

How to run the application

In the README of the application you will find the information about:

  • how to run the simulation;
  • how to switch the sources;
  • how to change the absorber material;
  • what is contained in the result of the simulation brachytherapy.hbk.
  • the environment set-up of the application is shown.

Results of the simulation

Example of results for all the brachytherapic techniques are shown in the information stored in the ntuple has been elaborated with analysis devices to obtain the histograms shown and the isodose curves.

Future

The next project involving the brachytherapy advanced example is the parallelisation of the system and the access to distributed calculation resources. MonteCarlo simulations have never been used in the clinical practice because they are slow in terms of computational time, even if the dose calculation is more accurate. A solution to this problem is given by the parallelisation of the application and the access to distributed resources: in such a way institutes can share CPU and run the simulation in a parallelised way, even if their single CPU resources are poor.

Collaborations

  • IST Genova
  • Servizio di Fisica Sanitaria Savona
  • Facolta' di Fisica Genova
  • INFN Genova

-- LucianoPandola - 21 Oct 2014

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Topic revision: r1 - 2014-10-21 - LucianoPandola
 
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