Our Neurosurgeons



Robert E. Breeze, M.D.

Dr. Breeze is the Vice–Chair for the Department of Neurosurgery and the Program Director for CU  Neurosurgery’s Residency Program.  His primary clinical interests are neurovascular surgery and skull-base surgery. He oversees the largest referral center for complex neurovascular surgery in the Rocky Mountain region. Learn more about Dr. Breeze.





J. Adair Prall, M.D.

Dr. Prall is board certified by the American Board of Neurological Surgery. He is experienced in all types of cranial and spinal surgery, and is nationally renowned for his expertise in vascular compression syndromes, including trigeminal neuralgia. Learn more about Dr. Prall.






Stephen Cass, M.D.

Dr. Stephen Cass is Professor in the Department of Otolaryngology at the University of Colorado School of Medicine. Dr. Cass is board certified in Otology and Neurotology, specializing in skull base tumors, hearing loss, and vertigo disorders. Learn more about Dr. Cass.




Radiation Oncologists

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Brian Kavanagh, M.D


Dr. Brian Kavanagh graduated summa cum laude with honors in biomedical engineering from the Tulane University School of Engineering and then remained at Tulane to receive his MD and MPH degrees from the School of Medicine and School of Public Health. He completed an internship at the Charity Hospital of Louisiana before entering a radiation oncology residency at Duke University, where he was an American Cancer Society Clinical Oncology Fellow. 





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Chad G. Rusthoven, M.D.


Dr. Chad Rusthoven is an Assistant Professor of Radiation Oncology at the University Of Colorado School Of Medicine, with a specialization in the treatment of thoracic and central nervous system malignancies. Learn more about Dr. Rusthoven.






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Sameer (Sam) Nath, M.D.

Dr. Nath received his medical degree from the University of California - San Diego and completed his residency at Yale University School of Medicine. A dedicated clinical researcher, Dr. Nath's interests include treatment techniques for radiotherapy patients. Learn more about Dr. Nath.






Tracey Schefter, M.D.


Dr. Tracey Schefter is a board certified (in both Canada and the US) radiation oncologist.  Dr. Schefter received her undergraduate engineering degree from The Royal Military College of Canada (1985-1989) and her medical degree from Queen's University in Kingston, Ontario, Canada (1990-1994).  Learn more about Dr. Schefter.






Douglas Tippin, M.D.

Dr. Douglas Tippin specializes in intraoperative radiation and brachytherapy cancer treatments. Dr. Tippin earned his medical degree from Ohio State University and completed a residency in internal medicine at the University of Chicago, where he also competed fellowship training in radiation oncology at the University of Chicago and the James Cancer Hospital in Columbus, Ohio.






Medical Team


Kelly Stuhr, MS, DABR

Ms. Stuhr joined the physics staff at the University of Colorado Department of Radiation Oncology in 1996. Ms. Stuhr is a board certified medical physicist, and is responsible for Gamma Knife Physics services such as treatment planning and quality assurance of the Gamma Knife system.  Ms. Stuhr is also the Senior Medical Physicist in the Department of Radiation Oncology, and assists in the organization and coordination of the dosimetry and physics teams.  Ms. Stuhr’s clinical interests include cranial and extracranial stereotactic radiation therapy, image guided radiation therapy, and high dose-rate brachytherapy. Ms. Stuhr’s primary research interest is investigating various techniques for treatment planning and delivery of stereotactic radiation therapy.





Cem Altunbas, PhD, DABR

Dr. Cem Altunbas is board certified by American Board of Radiology in Therapeutic Medical Physics, and he is responsible for Gamma Knife Physics services, such as treatment planning and quality assurance of the Gamma Knife system. Dr. Altunbas received his Ph.D. in Physics from SUNY Buffalo. Following his Ph.D. work, he completed a postdoctoral fellowship in Imaging Physics at UT MD Anderson Cancer Center and medical physics residency at Virginia Commonwealth University. Dr. Altunbas currently serves as Assistant Professor in the Department of Radiation Oncology, University Of Colorado School of Medicine.


David Thomas, PhD

Dr. Thomas joined the faculty of the Department of Radiation Oncology at the University of Colorado School of Medicine as Assistant Professor in July 2016. He received his PhD from the University of Edinburgh (UK), where his research focused on the physics and acoustics of resonating microbubbles in an ultrasound field, with relevance to contrast enhanced ultrasound imaging of microvasculature perfusion. Following graduation, he began a post-doctoral fellowship at the University of California Los Angeles, where he developed techniques for radiotherapy treatment planning that explicitly consider and compensate for breathing motion. Dr. Thomas is responsible for Gamma Knife Physics services, such as treatment planning and quality assurance of the Gamma Knife system. His current research interests include: Motion management techniques, 4D dose calculations, Functional lung imaging, MRI guided radiotherapy and Adaptive radiotherapy.



Management Team

Rocky-Mountain-Gamma-Knife-WJ-Kochevar.jpgW.J. Kochevar, Executive Manager




Natalie Pratt