TOPAS is a user-friendly simulation software layered upon the general-purpose Geant4 particle transport toolkit. It was designed specifically for medical physics applications by MGH, Stanford and UCSF.
Plastimatch is an open source software for image computation. Our main focus is high-performance volumetric registration of medical images, such as X-ray computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET).
TOPAS-nBio is an extension to the TOPAS toolkit that is currently being developed as part of an NCI-R01. The goal is to follow the approach of the TOPAS software package, making Monte Carlo simulations easy-to-use with focus on radiation biology at sub-cellular scales.