Dr. Johnstone has clinical interest in pediatric, and genitourinary malignancies and sarcomas. His recent clinical trials have involved acupuncture as symptom control in cancer patients, and his recent publications have dealt with the use of proton radiotherapy in children. He is a Fellow of the American College of Radiology and serves on the ACR Board of Chancellors. In 2007 he was President of the Society for Integrative Oncology, and in 2011 was President of the American Radium Society.