Medical Physicists

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Medical Physicists


Bruce Libby, Ph.D.

Associate Professor of Radiological Physics

Dr. Libby is a medical physicist in the Department of Radiation Oncology. The essential responsibility of the medical physicist’s clinical practice is to assure the safe and effective delivery of patient radiation treatments as prescribed by the Radiation Oncology physician. Dr. Libby assists the radiation oncology physician with patient brachytherapy treatments. Brachytherapy treatments are a form of radiation treatment where “seeds” containing radioactive material are inserted into the patient’s tumor site. He monitors the level of radiation being administered to the patient making sure that the treatment is delivered according to the treatment plan requested by the physician.

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Krishni Wijesooriya, Ph.D.

Associate Professor of Radiation Oncology

Dr. Wijesooriya joined the Department of Radiation Oncology Clinical Physics faculty in February 2008. She received her PhD in Nuclear Physics for research work at Thomas Jefferson National Accelerator Facility. Upon receiving her PhD she joined Argonne National Laboratory in Chicago as a post doctoral researcher to work on more Nuclear Physics experiments. In 2003 she joined VCU Medical Physics as a post doctoral fellow to perform 4D radiotherapy research. From 2006 - 2008 she worked as a Clinical Assistant Professor at University of Pittsburgh Medical Center. At UVA, Dr. Wijesooriya is actively involved in national clinical trial protocols. She is also involved in clinical and research projects that attempts to better manage organ motion that occur during radiation treatment.

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Quan Chen, Ph.D.

Assistant Professor of Radiation Oncology

Dr. Chen earned his Ph.D. in medical physics in 2004 from University of Wisconsin-Madison.  Prior to joining UVA, Dr. Chen worked at TomoTherapy Inc. as a senior research physicist developing innovative radiation therapy technologies.  Dr. Chen is experienced in TomoTherapy and high-performance computing in radiation therapy.  His other research interests include image processing, respiratory and motion management, quality assurance methods, Monte Carlo calculation, bio-luminescence imaging, and ultrasound parametric imaging.


David Schlesinger, Ph.D.

Associate Professor of Radiation Oncology

Dr. Schlesinger has worked as an Assistant Professor in the Department of Neurological Surgery since 2004, and formally joined the Clinical Physics Faculty in the Department of Radiation Oncology in 2009. Dr. Schlesinger’s clinical expertise is in stereotactic radiosurgey at the University of Virginia Gamma Knife center, where he assists the radiation oncologist and neurosurgeon to develop minimally invasive treatments for brain tumors and other neurologic conditions. Dr. Schlesinger also works in support of clinical trials at the university’s MR-Guided Focused Ultrasound Surgery Center.  Dr. Schlesinger earned his Ph.D. in Biomedical Engineering from the University of Virginia in 1998. His research interests include image processing, pattern recognition, multi-objective optimization, and systems engineering tools as applied to procedural quality assurance.


Jeffrey V. Siebers, Ph.D.

Director of Radiological Physics &

Professor of Radiation Oncology and Biomedical Engineering

Dr. Siebers joined the Department of Radiation Oncology, Medical Physics, in 2013.  He received his Ph.D. in Medical Physics from the University of Wisconsin in 1990.  Prior to joining UVA, he was a tenured Professor in the Department of Radiation Oncology at VCU where he acted as founding director of the Medical Physics graduate program and was program director of the Medical Physics residency program. Dr. Siebers’ clinical and research interests include robust treatment optimization, dose assessment accuracy, during treatment delivery quality assurance, radiation Dosimetry, quality assurance methods and metrics, clinical safety and efficiency.  He also provides instruction in the area of radiological physics to M.D. and Medical Physics’ residents.