Depth dose calculation in Geant4 involves simulating the energy deposition of particles as they travel through a medium, typically to understand how radiation dose varies with depth. This is crucial in applications like radiation therapy, where precise dose distribution is necessary for effective treatment.
To set up a depth dose simulation in Geant4, you need to define the geometry of your medium, specify the particle source, and configure the physics processes. You also need to set up scoring volumes or detectors to record the energy deposited at various depths. This involves creating a G4RunManager, defining the materials, and implementing a sensitive detector to collect dose information.
For accurate depth dose calculations, it is recommended to use the appropriate physics lists that include electromagnetic and hadronic processes. Commonly used physics lists include QGSP_BIC, FTFP_BERT, and QGSP_BERT for hadronic interactions, and standard EM physics for electromagnetic interactions. The choice depends on the type of particles and energies involved in your simulation.
To visualize the depth dose distribution, you can use Geant4’s built-in visualization tools or export the data to external tools like ROOT or MATLAB. Geant4 provides commands to create histograms and profiles of the dose distribution, which can be plotted to visualize how the dose varies with depth in the medium.
Common sources of error in depth dose calculations include incorrect geometry setup, inappropriate physics list selection, insufficient number of simulated particles, and inadequate detector resolution. Ensuring accurate material properties and using a sufficiently fine scoring grid can help minimize errors. Additionally, validating your simulation results against experimental data or established benchmarks is crucial for ensuring accuracy.