Radiation Oncology Residency Program
Welcome to the OHSU Radiation Oncology Residency Program! We are pleased to introduce you to our Program Director, Dr. Nima Nabavizadeh, who will provide you with valuable insights into our residency and what makes our program unique.
The Radiation Oncology Residency Program is a four-year ACGME-accredited program designed to develop skilled radiation oncologists ready for careers in clinical practice, education, research, and advocacy. We offer a supportive learning environment that prioritizes trainee well-being and professional growth, in keeping with the University's mission of healing, teaching, and discovery.
Our training combines clinical experience, lectures, multidisciplinary learning, and research to build both clinical and scientific expertise. Throughout the program, trainees progressively assume more responsibility as they rotate through various segments over the four years. Learn more about our residency program, including our curriculum, faculty, and application requirements.
Program Aims
The Radiation Oncology Residency Program aims to offer residents a robust, progressive clinical experience in radiation oncology, complemented by essential basic science and research support. The program will achieve this by providing a blend of supervised clinical experiences, seminars, lectures, and research assignments, all carefully designed to enhance the resident's clinical skills and establish a strong scientific foundation for their growth. The objectives of the Radiation Oncology Residency Program include:
- Train physicians to think critically and independently for the practice of patient-centered radiation oncology with graduated responsibility as residents demonstrate competence.
- Promote a culture of safety and continuous system-based improvement.
- Provide an advanced educational experience in all radiation oncology subspecialties.
- Provide opportunities for research and/or professional development during residency.
- Develop well-adjusted residents through the promotion of resident well-being and happiness.
- Promote diversity and inclusiveness in the workforce.
Program Leadership
Nima Nabavizadeh, M.D.
Dr. Nima Nabavizadeh is the Program Director of the Radiation Oncology Residency Program and an Associate Professor of Radiation Medicine. He received his medical degree from the University of Oklahoma College of Medicine, where he was inducted into the Alpha Omega Alpha Honor Medical Society, and completed his residency at OHSU. He also holds a degree in Mechanical Engineering from the University of Oklahoma. In addition to his clinical work, Dr. Nabavizadeh serves as Chief Medical Officer at the Cancer Early Detection Advanced Research Center (CEDAR), where he helps lead efforts to improve early cancer detection and outcomes.
Casey Williamson, M.D., M.A.S.
Dr. Casey Williamson is the Associate Program Director of the Radiation Oncology Residency Program, an Assistant Professor of Radiation Medicine. He earned both his medical degree and a master’s degree in clinical research from the University of California San Diego, where he also completed his residency training in radiation oncology. Dr. Williamson’s clinical interests focus on the treatment of gynecologic and genitourinary cancers, with specialized expertise in external beam radiation therapy and brachytherapy. In addition to his commitment to the residency program, he also serves as the Medical Director of the Radiation Therapy Program.
Program Faculty
Aaron Grossberg, M.D., Ph.D.
Dr. Grossberg is an Associate Professor of Radiation Medicine and Co-Director of the program's radiation biology curriculum. He earned his medical and doctorate degrees from OHSU and completed his residency training at the University of Texas - MD Anderson Cancer Center. In a joint appointment with the Cancer Early Detection Advanced Research Center and the Brenden-Colson Center for Pancreatic Care, Dr. Grossberg studies the interaction between cancer and metabolism in an effort to identify ways to diagnose cancers sooner and improve the quality of life of cancer patients. His clinical focus includes pancreatic cancer, gastrointestinal cancer, and breast cancer.
Arthur Hung, M.D.
Dr. Hung is the Interim Chair of the Department of Radiation Medicine. He is an Associate Professor of Radiation Medicine and an Associate Professor of Ophthalmology. He received his medical degree from The Ohio State University and completed his residency at the University of Texas – MD Anderson Cancer Center. His clinical focus includes bladder, kidney, liver, and prostate cancers and sarcomas.
Carl Post, M.D.
Dr. Post is an Assistant Professor of Radiation Medicine and faculty advisor for the Radiation Medicine Student Interest Group. He received his medical degree from University of Nebraska Medical Center and completed his residency training at OHSU's Radiation Oncology Residency Program. His clinical interests includes thoracic malignancies and sarcoma.
Dr. Post received the ARRO Educator of the Year in July 2025.
Joshua Walker, M.D., Ph.D.
Dr. Walker is and Assistant Professor of Radiation Medicine and an Assistant Professor of Cell, Developmental and Cancer Biology. He also serves as Co-Director of the program's radiation biology curriculum. He earned both his medical and doctorate degrees at Oregon Health and Science University School of Medicine and completed his residency at OHSU as well. Dr. Walker's clinical interests primarily revolve around tumor immunotherapy and radiotherapy of solid tumors.
Reid F. Thompson, M.D., Ph.D.
Dr. Thompson is Associate Professor of Radiation Medicine and an Associate Professor of Biomedical Engineering. He obtained his medical and doctorate degrees from the Albert Einstein College of Medicine and completed his residency at the University of Pennsylvania. Dr. Thompson also holds degrees in genetics and biophysical chemistry. His clinical focus includes the treatment of melanoma and other skin cancers using radiotherapy, often in combination with other agents such as immunotherapy.
Sophia Bornstein, M.D., Ph.D.
Dr. Bornstein is a Clinical Associate Professor of Radiation Medicine. She earned her medical and doctorate degrees from Oregon Health and Science University School of Medicine and completed her residency at OHSU's Radiation Oncology Residency Program. Her clinical focus includes palliative care and the treatment of breast cancers.
Timur Mitin, M.D., Ph.D.
Dr. Mitin is a Professor of Radiation Medicine. He received his medical and doctorate degrees from Tufts University and completed his residency training at the Harvard Radiation Oncology Program. His clinical interests center on the treatment of genitourinary malignancies, with a special focus on bladder preservation therapy for patients with muscle-invasive bladder cancer, as well as head and neck cancers.
Dr. Mitin received the program's Above & Beyond Educator Award in July 2025.