PSF, LSF and S/P in mammography: GEANT4 validation.

The main goal of this study was to validate the predictions of GEANT4, a Monte Carlo code originally developed for high-energy physics, for low-energy (10-40 keV) photon transmission and scattering through matter similar to biological tissue. We compared GEANT4 calculations with existing phantom data relevant for the mammographic imaging technique. This work showed that scattered-to-primary ratio data can be simulated using GEANT4 with a deviation smaller than 5%. At the same time, we encountered a limitation in the small-angle region description by the code, which is important for point- and line-spread function calculations. The comparison with forward angle data showed that the GEANT4 models, known as "G4 Low Energy" and "G4 Penelope", describe the measurements for X-ray beams typically used in mammography better than 10% for angles above 10 degrees, and that "G4 Low Energy" is preferable to "G4 Penelope ". The results confirm the possible use of GEANT4 for the optimization of applications based on low-energy photon transmission and scattering.