Requirements in modeling and visualization for Geant4-based radiotherapy simulation

Geant4 is utilized for many radiological software applications and then successfully adopted to them. However, developers spend much time and effort to add functions in order to apply Geant4 to the research of the radiotherapy. We described requirements of the modeling of the target volume such as a patient geometry and the visualization of results in simulation. Additionally, tools we developed subject to the requirements are also described.