Ashok Tiwari is a Postdoctoral Research Associate at Oak Ridge National Laboratory. He received his Ph.D. in physics from the University of Iowa and two master’s degrees in physics from the University of South Dakota and Tribhuvan University. His Ph.D. research spanned radiopharmaceutical therapy dosimetry and quantitative imaging in nuclear medicine. He explored (1) the dosimetry of beta and alpha-emitting radionuclides using the Monte Carlo simulations and (2) the simulation of a clinical PET scanner and its validation. His Ph.D. thesis was awarded the prestigious Ballard and Seashore dissertation fellowship. His research interests include radiation physics, radiopharmaceutical therapy, and Monte Carlo simulations. Dr. Tiwari’s work at ORNL primarily focuses on developing and validating a multiscale simulation framework for generating patient-specific synthetic data.