Radiation therapy
radiotherapy.  In particular, he uses Monte Carlo simulations as a research tool and has nearly 30 years of experience in various production Monte Carlo codes.  His recent research projects have included such diverse topics as parallel Monte Carlo computing using GPU/CUDA, nanomaterials-based x-ray sources, X-ray computed tomography (CT) and proton radiotherapy, compressive sensing. Xu has directed numerous projects, with a total of about $20 million in grant funding from agencies such as the [[National Science Foundation