Peter Johnstone was raised in Gresham, Oregon. He graduated from the United States Naval Academy in 1979, completing a Master of Arts degree in Communication from Oklahoma University in 1985 and an M.D. degree from the Uniformed Services University of the Health Sciences in 1989. He completed Residency in Radiation Oncology subsequently at the National Cancer Institute. Currently Clinical Director and Vice Chair of Radiation at Moffitt Cancer Center, Dr. Johnstone previously served as Chair and William A. Mitchell Professor of Radiation Oncology at Indiana University, President and Chief Executive Officer of the IU proton center and director of IU cyclotron operations. Dr. Johnstone was President of the Society for Integrative Oncology in 2007, and of the American Radium Society in 2010.  He served on the ACR Board of Chancellors between 2011-2017.