Exercices for GATE

Exercices for GATE

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    • Welcome
    • Ressources
    • Exercice 1
    • Exercice 2.1 (dose)
    • Exercice 2.2 (dose, 3D)
    • Exercice 2.3 (dose, proton)
    • Exercice 3 (linac)
    • Exercice 4 (trt)
    • Exercice 5 (brachy)
    • Exercice 6 (spect)
    • Exercice 7 (pet)
    • Exercice 8 (tle)

    Exercice 4 - Internal radiation therapy

    TRT

    Targeted radionuclide therapy (TRT) delivers radiation to lesions by administration of radiolabeled molecular agents designed to specifically concentrate into targets. We want now to create a simulation of such a treatment (internal radiation therapy). Macros will be in the folder internal-rt/.

    Step 1

    To start, we first study some radionuclides. Create from scratch a simple simulation that allow you to get the energy spectrum of the e- emitted by a source of Yttrium-90 in a vacuum. Energy spectrum may be recorded with a EnergySpectrumActor or a PhaseSpaceActor. Plot the energy spectrum.

    In GATE, a source of a radionuclide is defined with some macro like:

        /gate/source/addSource Yttrium
        /gate/source/Yttrium/gps/particle ion
        /gate/source/Yttrium/gps/ion 39 90 0 0
        /gate/source/Yttrium/gps/type Volume
        /gate/source/Yttrium/gps/shape Sphere
        /gate/source/Yttrium/gps/radius 1.5 mm
        /gate/source/Yttrium/gps/angtype iso
        /gate/source/Yttrium/gps/centre 0. 0. 0. mm
        /gate/source/Yttrium/gps/energy 0 MeV
    

    Do not forget to add the radioactive decay process:

        /gate/physics/addProcess RadioactiveDecay
        /gate/physics/addPhysicsList emstandard_opt3
    

    Use a Filter to record separately the energy spectrums for e- and gamma.

    Analyze the emitted e- and gamma from other radionuclides used for treatment, for example Lutetium-177 or Iode-131. You may also consider radionuclides used for imaging: Indium-111 (SPECT), Gallium-68 (PET) or Fluor-18 (PET).

    Information can be found on http://www.nucleide.org/DDEP_WG/DDEPdata.htm.

    Step 2

    Modify the previous simulations in order to plot the depth dose curve of the radionuclides in water. You may have to change the direction of emission of the source along a defined direction. Consider a depth resolution of for example, 0.2 mm.

    What are the differences in absorbed dose according to the radionuclides ?

    Step 3

    We will now learn to use a "voxelized source". This is an emitting source of particles described as a spatial distribution with a matrix of pixel intensity. Several SPECT images have been calibrated and merged together to produce a time-integrated activity emission map (TIA) associated with a patient CT. Consider the simulation that uses this TIA as a voxelized source, see macros main.mac and source-vox.mac in the folder 4_internal_rt. The pixels in the TIA image are expressed in MBq.h.

    Perform a simulation, analyze the results.

    Step 4

    Change the voxelized source to a simple point source in the middle of the patient. Then, change the radionuclide, for example by using Lutetium-177 or Iode-131 or any radionuclides you like in http://www.nucleide.org/DDEP_WG/DDEPdata.htm. You may look at the source-gps.mac file.

    What are the differences in absorbed dose according to the radionuclides ?

    ← Exercice 3 (linac)Exercice 5 (brachy) →
    • TRT
    • Step 1
    • Step 2
    • Step 3
    • Step 4
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