Our Physicians

John H. Giesler, MD

After graduating with an undergraduate degree in biology from the University of Toledo, Dr. Giesler attended medical school at Ohio State University College of Medicine. He completed his radiation oncology residency at M.D. Anderson Cancer Center in Houston in 1992. That same year, Dr. Giesler became board-certified by the American Board of Radiology. Dr. Giesler has provided senior physician leadership for Radiation Oncology Services since 1992.

Kim N. Vu, MD

Dr. Vu attended Rhodes College in Memphis, Tennessee, where she received her undergraduate degree in biochemistry. She later graduated from medical school at the University of Tennessee. Dr. Vu finished her Radiation Oncology residency in 2005 at the Medial University of South Carolina. In 2006, she was board-certified by the American Board of Radiology. Dr. Vu joined Radiation Oncology Services in 2005.

Sasha H. Wahab, MD

Dr. Wahab attended the University of Virginia where he received his undergraduate degree before attending Washington University School of Medicine. He then completed his residency in radiation oncology at Mallinckrodt/Washington University. In 2009, Dr. Wahab was board-certified by the American Board of Radiology. Dr. Wahab began his private practice career in Atlanta in 2008 before joining ROS in 2009.

J. Warner Ray, MD, FACRO

Dr. Ray, an Atlanta native, is the founder and medical director of Radiation Oncology Services. His vision and leadership have resulted in seven community-based cancer centers throughout the greater Atlanta area as well as numerous cancer treatment programs. It is through Dr. Ray’s strong commitment to quality that Radiation Oncology Services is known for blending the very technical aspects of radiation therapy with the compassionate and personalized care needed for each patient and family.